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This 20-year water quality monitoring status and trends report for the Lahontan Water Board’s Surface Water Ambient Monitoring Program (Regional SWAMP) provides an overview of the environmental settings across the Region to give the reader a sense of the diverse ecological landscape, land uses, distribution and abundance of aquatic resources, and fire history. It includes a retrospective analysis of the Regional SWAMP’s ongoing, targeted water quality monitoring results (2000 - 2021), and concludes by presenting an adaptive monitoring and assessment framework (adapted from the California Wetlands Monitoring Workgroup's Wetland and Riparian Monitoring Plan, known as "WRAMP").  The framework was used to review the program and recommend future monitoring changes to improve efficiencies and address some of the recommendations listed in the Regional SWAMP's 2019 Core Program Review. 

The purpose of this document is to guide efforts and summarize plans developed within the RMP. The intended audience includes representatives of the many organizations who directly participate in the Program. This document will also be useful for individuals who are not directly involved with the RMP but are interested in an overview of the Program and where it is heading.  

The organization of this Multi-Year Plan parallels the RMP planning process (Figure 2). Section 1 presents the long-term management plans of the agencies responsible for managing water quality in the Bay and the overarching management questions that guide the Program. The agencies’ long-term management plans provide the foundation for RMP planning (Figure 2). In order to turn the plans into effective actions, the RMP distills prioritized lists of management questions that need to be answered (Page 8). The prioritized management questions then serve as a roadmap for scientists on the Technical Review Committee, workgroups, and strategy teams to plan and implement scientific studies to address the most urgent information needs. This information sharpens the focus on management actions that will most effectively and efficiently improve water quality in the Bay. 

While the antimicrobial ingredient triclosan has been widely monitored in the environment, much less is known about the occurrence and toxicity of its major transformation product, methyl triclosan. An improved method was developed and validated to effectively extract and quantify both contaminants in fish tissue and was used to characterize concentrations in small prey fish in areas of San Francisco Bay where exposure to triclosan via municipal wastewater discharges was expected to be highest. Concentrations of triclosan (0.44–57 ng/g ww, median 1.9 ng/g ww) and methyl triclosan (1.1–200 ng/g ww, median 36 ng/g ww) in fish tissue decreased linearly with concentrations of nitrate in site water, used as indicators of wastewater influence. The total concentrations of triclosan and methyl triclosan measured in prey fish were below available toxicity thresholds for triclosan, but there are few ecotoxicological studies to evaluate impacts of methyl triclosan. Methyl triclosan represented up to 96% of the total concentrations observed. These results emphasize the importance of monitoring contaminant transformation products, which can be present at higher levels than the parent compound.

This report details activities associated with the biannual Regional Monitoring Program for Water Quality in the San Francisco Estuary (RMP) water cruise. The RMP water sampling program was redesigned in 2002 to adopt a randomized sampling design at thirty-one sites in place of the twenty-six “spine of the Estuary” stations sampled previously. In 2007, the number of sites was decreased to twenty-two stations, combined probabilistic and historic, and it remains as such for 2021. 

The theme of the 2022 Pulse is "50 Years After the Clean Water Act." Nine different individuals or groups have contributed perspectives on progress to date and challenges ahead. This Pulse also includes summaries, from a historical perspective, on the major water quality parameters of concern in the Bay.   

Bisphenols are a class of synthetic, mobile, endocrine-disrupting chemicals. Bisphenol A (BPA), the most well-studied bisphenol, is produced and used in vast quantities worldwide—especially in polycarbonate plastics and as a polymer additive. Recently, some manufacturers have begun using alternative bisphenol compounds, such as bisphenol F (BPF) and bisphenol S (BPS). These uses of bisphenols have led to widespread bisphenol detections in the environment and wildlife. The present study examined wastewater effluent in the San Francisco Bay Area and San Francisco Bay sediment samples for 17 bisphenols. The effluent samples were compared to available stormwater runoff data to better understand bisphenol transport, fate, and potential risks to wildlife.

This report describes the updates to the vernal pool habitat map, the development of the ambient baseline ecological condition survey of vernal pool systems within the Central Valley, and the development and results of the habitat development curve. A fictional project example shows how CRAM and the vernal pool complex CDFs and HDCs can help project proponents and the regulatory agencies think critically about project designs (using CRAM Attributes and Metrics as a standard measure), evaluate project conditions within a regional landscape context, and monitor project performance over time to ensure that project goals are met.

Funding for this report was provided through an agreement with the U.S. Environmental Protection Agency (USEPA).  This report does not necessarily reflect the views and policies of USEPA nor does the mention of trade names or commercial products within this report constitute endorsement or recommendation for use.

A future Sacramento-San Joaquin Delta and Suisun Marsh (“Delta” herein) that supports healthy ecosystems and native species, while also meeting flood risk reduction, water supply, water quality, carbon sequestration, economic, and cultural objectives, requires that appropriate restoration and management actions be taken in the right place at the right time. Geographic setting affects the potential opportunities available—not all actions are suitable everywhere. Physical factors determining what types of activities are appropriate now and in the future include a site’s elevation, degree of tidal and fluvial influence, salinity, soil type, and local effects of climate change, which all vary spatially across the Delta. While there has been considerable progress over the last several decades, continued acceleration of the pace and scale of enhancement actions appropriate to landscape position is needed. Understanding the physical template is necessary for developing strategies that move beyond opportunistic restoration, support resilience over time, and have the potential to connect and magnify benefits across the larger landscape.

As we drive our cars, our tires shed tiny particles

When it rains, stormwater runoff carries tire particles—and the toxic chemicals they contain—from city streets and highways to storm drains and fish habitat in creeks and estuaries like San Francisco Bay. Stormwater washes trillions of tire particles into the Bay each year.

How do tires affect wildlife?

A recent study found a highly toxic chemical (“6PPD-quinone”) derived from vehicle tires in Bay Area stormwater at levels that are lethal to coho salmon. New data indicate that steelhead, a salmon species still migrating through the Bay to surrounding watersheds, are also sensitive to this chemical.

Organophosphate esters (OPEs) and bisphenols are two classes of industrial chemicals that are ubiquitously detected in environmental matrices due to high global production and widespread use, particularly in the manufacture of plastic products. In 2017, water samples collected throughout the highly urbanized San Francisco Bay were analyzed for 22 OPEs and 16 bisphenols using liquid chromatography-electrospray ionization-Q Trap-mass spectrometry. Fifteen of the 22 OPEs were detected, with highest median concentrations in the order TCPP (42 ng/L) > TPhP (9.5 ng/L) > TBOEP (7.6 ng/L) > TnBP (7.5 ng/L) > TEP (6.7 ng/L) > TDCIPP (6.2 ng/L). In contrast, only two of 16 bisphenols, BPA and BPS, were quantified, with concentrations ranging from <0.7–35 ng/L and <1–120 ng/L, respectively. BPA and a few OPEs (EHDPP and TEHP) were primarily present in the particulate phase, while BPS and all other observed OPEs were predominantly found in the dissolved phase. Pairwise correlation analysis revealed several strong, positive correlations among OPEs, and few weak, negative correlations between OPEs and BPA, suggesting differences between the two classes with respect to their sources, pathways, and/or fate in the environment. Concentrations of OPEs and bisphenols observed in this study were generally consistent with reported concentrations in other estuarine and marine settings globally. TDCIPP exceeded existing predicted no-effect concentrations (PNECs) at some sites, and six other compounds (TCrP, IDDPP, EHDPP, TPhP, TBOEP, and BPA) were observed at levels approaching individual compound PNECs (not considering mixture effects), indicating potential risks to Bay biota. These results emphasize the need to control releases of these contaminants in order to protect the ecosystem. Periodic monitoring can be used to maintain vigilance in the face of potential regrettable substitutions.

Per- and polyfluoroalkyl substances (PFAS), a family of thousands of synthetic, fluorine-rich compounds commonly referred to as “forever chemicals,” are known for their thermal stability, non-reactivity, and surfactant properties. These unique compounds have widespread uses across consumer, commercial, and industrial products, resulting in widespread occurrence in the environment and wildlife across the globe. This study analyzed ambient surface water in San Francisco Bay for 40 PFAS to discern the occurrence, fate, and potential risks to ecological and human health.

Eleven of 40 PFAS were detected in ambient surface water collected in 2021 from 22 sites in the Bay. Seven PFAS (PFPeA, PFHxA, PFHpA, PFOA, PFBS, PFHxS, and PFOS), were found in at least 50% of samples. PFHxA and PFOA were the most frequently detected analytes (detection frequencies of 86% and 77%, respectively). PFPeA and PFHxA were generally found at the highest concentrations across sites, with median and maximum concentrations of 1.6 and 4.8 ng/L and 1.5 and 5.7 ng/L, respectively. Pairwise Spearman's correlations revealed strong positive correlations  (p <0.001; r > 0.77) among the seven PFAS detected in at least 50% of sites, suggesting significant similarities between their sources, pathways, and/or fate in the environment. PFBA, PFNA, PFDA, and 6:2 FTS were found at a limited number of sites in the Bay. 6:2 FTS was found at a single site at 14 ng/L, the highest concentration of any individual PFAS in the Bay. The sums of detected PFAS for all sites had median and maximum concentrations of 10 and 29 ng/L, respectively.

A central motivating question for the Sacramento-San Joaquin Delta science and management community is what should be done, where and when, to support future Delta landscapes that are ecologically and economically viable and resilient to change. Actions must be taken that have the greatest potential for achieving multiple benefits. This is especially important given the urgency to rapidly transition Delta landscapes to address biodiversity loss, erosion of ecosystem resilience, flood risk, water supply reliability, and cultural and economic sustainability. Landscape-scale planning is needed to examine how individual actions add up to meaningful change. Such planning involves figuring out how different areas can provide different functions at different times and helps show how choices made now can help shift trajectories toward desired outcomes. Too often, land use and management decisions are made based on a limited set of objectives or at the site scale, resulting in missed opportunities. Actions (or inaction) should not foreclose on critical opportunities. Moving forward, there is great need to more effectively compare possible future scenarios across a range of ecological and economic factors. This scenario analysis for Staten Island — a large Delta island managed for multiple uses and facing challenges similar to elsewhere in the Delta — provides an approach to help address this need.

The San Francisco Bay total maximum daily loads (TMDLs) call for a 50% reduction in mercury (Hg) loads by 2028 and a 90% reduction in PCBs loads by 2030. In support of these TMDLs, the Municipal Regional Permit for Stormwater (MRP) (SFBRWQCB, 2009, SFBRWQCB, 2015, SFBRWQCB, 2022) called for the implementation of control measures to reduce PCBs and Hg loads from urbanized tributaries. In addition, the MRP has identified additional information needs associated with improving understanding of sources, pathways, loads, trends, and management opportunities of pollutants of concern (POCs). In response to the MRP requirements and information needs, the Small Tributary Loading Strategy (STLS) was developed, which outlined a set of management questions (MQs) that have been used as the
guiding principles for the region’s stormwater-related activities. In recognition of the need to evaluate changes in loads or concentrations of POCs from small tributaries on a decadal scale, the updated 2018 STLS Trends Strategy (Wu et al., 2018) prioritized the development of a new dynamic regional watershed model for POCs (PCBs and Hg focused) loads and trends. This regional modeling effort will provide updated estimates of POC concentrations and loads for all local watersheds that drain to the Bay. The Watershed Dynamic Model (WDM) will also provide
a mechanism for evaluating the impact of management actions on future trends of POC loads or concentrations.

As a multi-use modeling platform, the WDM is being developed to include other pollutants, such as contaminants of emerging concern (CECs), sediment, and nutrients and to be coupled with a Bay fate model to form an integrated watershed-Bay modeling framework to address Regional Monitoring Program (RMP) management questions. As this model is developed, flexibility to link with other models will be an important consideration.

The response of shallow groundwater to sea-level rise is a relatively new field of study. For low-lying coastal communities, sea-level rise adaptation efforts must consider the potential for groundwater rise to avoid maladaptation. The need to better understand this slow and chronic threat was identified as a critical data gap in the San Francisco Bay Area’s (Bay Area’s) adaptation efforts during the Bay Area Groundwater and Sea-Level Rise Workshop in 2019.

Pathways Climate Institute LLC (Pathways) and the San Francisco Estuary Institute (SFEI) gathered and analyzed multiple data sets and collaborated with city and county partners to analyze and map the existing “highest annual” shallow groundwater table and its likely response to future sea-level rise. This effort covers four counties (Alameda, Marin, San Francisco, San Mateo) and was funded by the Bay Area Council’s California Resilience Challenge. The study focused on the San Francisco Bay side of each county and does not include the Pacific coastline of Marin, San Francisco, nor San Mateo Counties. An advisory committee composed of city and county representatives provided essential support by gathering data and reviewing depth-to-groundwater maps. Additional academic and agency advisors participated in project team meetings and informed project direction. This effort produced the following publicly available data and online tools to support adaptation efforts:

• Existing and future condition depth to groundwater GIS data available for download (geodatabase format).
• A StoryMap providing background information and graphical representations of the processes and impacts of groundwater rise.
• Web maps showing: (1) existing depth to groundwater; and (2) a comparison of the extent of emergent groundwater to the extent of coastal flooding under various sea-level-rise scenarios.

Stormwater agencies in the San Francisco Bay Area are identifying watershed areas that are polluted with PCBs in order to prioritize management efforts to reduce impairment in the Bay caused by PCBs carried in stormwater. Water sampling during storms has been used to characterize PCB concentrations but management prioritization based on the comparison of concentrations between watersheds is made difficult due to variations in flow and sediment erosion between storms and in relation to varying land use. In addition, identifying PCB source areas within priority watersheds has proven complex and costly. To address these challenges, the San Francisco Bay Regional Monitoring Program (RMP) has developed two new interpretive methods based on storm-event PCB yields (PCBs mass per unit area per unit time) and fingerprints of Aroclors (commercial PCB mixtures) that make existing data more useful for decision-making. 

The objectives of this study were to: 

• Apply the yield method to the regional stormwater dataset and provide new rankings, 
• Estimate the presence of Aroclors in samples where congener data are available
• Evaluate data weaknesses and recommend watersheds to resample, and
• Classify watersheds into high, medium, and low categories for potential management.

This report presents a strategy and multi-year workplan for modeling polychlorinated biphenyls (PCBs), contaminants of emerging concern (CECs), and sediment in San Francisco Bay (the Bay). Robust in-Bay fate modeling is needed to address priority management questions that have been identified for these constituents.

The strategy for in-Bay modeling presented in this report is a major element of a broader, integrated strategy that is being developed across RMP Workgroups for modeling contaminants flowing from the Bay watersheds and other pathways into the Bay. The broader project is expected to yield an integrated strategy in 2022, followed by implementation of a pilot effort in 2023. Coordination of the in-Bay modeling effort with the broader integrated strategy and other modeling work (e.g., nutrient modeling under the Nutrient Management Strategy) will be critical to optimizing use of the funds allocated to modeling.

The Dredged Material Management Office (DMMO) is responsible for annually approving dredging and disposal of millions of cubic yards of sediment to maintain safe navigation in San Francisco Bay. Dredged sediment is characterized for physical, chemical, and biological characteristics to ensure sediment disposed of in the Bay or at beneficial use locations does not cause adverse environmental impacts. Bioaccumulation thresholds and total maximum daily loads (TMDLs) have been established for several contaminant classes, including PCBs, and are used by the DMMO to determine whether sediment contaminant levels trigger subsequent bioaccumulation testing. Sediment with contaminant concentrations above any TMDL levels cannot be disposed of within the Bay but may be further evaluated for upland reuse and ocean disposal. The objective of this study was to evaluate PCB bioaccumulation data from navigational dredging projects to assess the existence of correlations between sediment chemistry and bioaccumulation test results. The motivation for this study was to determine whether the current PCB bioaccumulation trigger is effective in differentiating sediment bioaccumulation concerns. The DMMO may use the results of this study to inform evaluation requirements for PCBs, particularly in support of modifying the terms of the Long-term Management Strategy for San Francisco Bay (LTMS) programmatic Essential Fish Habitat (EFH) agreement concerning PCB bioaccumulation testing. 

The combustion of structures and household materials as well as firefighting during wildfires lead to releases of potentially hazardous chemicals directly into the landscape. Subsequent storm-water runoff events can transport wildfire-related contaminants to downstream receiving waters, where they may pose water quality concerns. To evaluate the environmental hazards of northern California fires on the types of contaminants in storm water discharging to San Francisco Bay and the coastal marine environment, we analyzed storm water collected after the northern California wildfires (October 2017) using a nontargeted analytical (NTA) approach. Liquid chromatography quadrupole time-of-flight mass spectrometric analysis was completed on storm-water samples (n = 20) collected from Napa County (impacted by the Atlas and Nuns fires), the city of Santa Rosa, and Sonoma County (Nuns and Tubbs fires) during storm events that occurred in November 2017 and January 2018. The NTA approach enabled us to establish profiles of contaminants based on peak intensities and chemical categories found in the storm-water samples and to prioritize significant chemicals within these profiles possibly attributed to the wildfire. The results demonstrated the presence of a wide range of contaminants in the storm water, including surfactants, per- and polyfluoroalkyl substances, and chemicals from consumer and personal care products. Homologs of polyethylene glycol were found to be the major contributor to the contaminants, followed by other widely used surfactants. Nonylphenol ethoxylates, typically used as surfactants, were detected and were much higher in samples collected after Storm Event 1 relative to Storm Event 2. The present study provides a comprehensive approach for examining wildfire-impacted storm-water contamination of related contaminants, of which we found many with potential ecological risk. Environ Toxicol Chem 2022;00:1–14. © 2022 SETAC

This memo provides a high-level summary of the quality assurance assessment for data reported by the RMP.  In 2019, fish tissue samples were collected from nine Bay/Delta areas and three additional wetland/slough areas for the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP). General descriptions of the sample collection methods are provided in the RMP Quality Assurance Program Plan, cruise plans, cruise reports, and field sampling reports. These documents are available from the SFEI website (http://www.sfei.org/content/status-and-trends-monitoring-documents).

This report details activities associated with the Regional Monitoring Program North Bay Selenium Study in 2020 and 2021. The study was designed to monitor two sites for selenium (Se) in water and clam tissue six times annually between June and February. Due to the COVID pandemic, however, four sample collection events were completed. This report outlines the sampling activities, personnel, and site locations monitored for the project.

This report details plans associated with sediment sampling for the Bay Margins Sediment Study for the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP). Bay margins (i.e., mud flats and adjacent shallow areas of the Bay) are productive and highly utilized by biota of interest (humans and wildlife). This study will provide a spatially-distributed characterization of surface sediment contamination and ancillary characteristics within San Pablo Bay, Suisun Bay, and Carquinez Strait margin areas. This study builds on two previous studies to characterize surface sediment contamination in Central and South Bays.

This report details plans associated with the annual Regional Monitoring Program for Water Quality in the San Francisco Estuary (RMP) water cruise. The RMP water sampling program was redesigned in 2002 to adopt a randomized sampling design at thirty-one sites in place of the twenty-six base program stations sampled previously. In 2007, the number of sites was decreased to twenty-two stations, and it remains as such for 2021. The analytes for 2021 have been modified based on the Status and Trends (S&T) Review process that started in 2020. The analytes that are being removed from the program include selenium and methylmercury (dissolved and particulate), while bisphenols and organophosphate esters (OPEs) have been added to S&T monitoring. 

A comprehensive, non-targeted analysis of polar organic pollutants using high resolution/accurate mass (HR/AM) mass spectrometry approaches has been applied to water samples from San Francisco (SF) Bay, a major urban estuary on the western coast of the United States, to assess occurrence of emerging contaminants and inform future monitoring and management activities. Polar Organic Chemical Integrative Samplers (POCIS) were deployed selectively to evaluate the influence of three contaminant pathways: urban stormwater runoff (San Leandro Bay), wastewater effluent (Coyote Creek, Lower South Bay), and agricultural runoff (Napa River). Grab samples were collected before and after deployment of the passive samplers to provide a quantitative snapshot of contaminants for comparison. Composite samples of wastewater effluent (24 hours) were also collected from several wastewater dischargers. Samples were analyzed using liquid-chromatography coupled to high resolution mass spectrometry. Resulting data were analyzed using a customized workflow designed for high-fidelity detection, prioritization, identification, and semi-quantitation of detected molecular features. Approximately 6350 compounds were detected in the combined data set, with 424 of those compounds tentatively identified through high quality spectral library match scores. Compounds identified included ethoxylated surfactants, pesticide and pharmaceutical transformation products, polymer additives, and rubber vulcanization agents. Compounds identified in samples were reflective of the apparent sources and pathways of organic pollutant inputs, with stormwater-influenced samples dominated by additive chemicals likely derived from plastics and vehicle tires, as well as ethoxylated surfactants.

Cities are both embedded within and ecologically linked to their surrounding landscapes. Although urbanization poses a substantial threat to biodiversity, cities also support many species, some of which have larger populations, faster growth rates, and higher productivity in cities than outside of them. Despite this fact, surprisingly little attention has been paid to the potentially beneficial links between cities and their surroundings.

We identify five pathways by which cities can benefit regional ecosystems by releasing species from threats in the larger landscape, increasing regional habitat heterogeneity and genetic diversity, acting as migratory stopovers, preadapting species to climate change, and enhancing public engagement and environmental stewardship. Increasing recognition of these pathways could help cities identify effective strategies for supporting regional biodiversity conservation and could provide a science-based platform for incorporating biodiversity alongside other urban greening goals.

In response to the widely recognized negative impacts of urbanization on biodiversity, many cities are reimagining urban design to provide better biodiversity support. Some cities have developed urban biodiversity plans, primarily focused on improving biodiversity support and ecosystem function within the built environment through habitat restoration and other types of urban greening projects. The biophilic cities movement seeks to reframe nature as essential infrastructure for cities, seamlessly integrating city and nature to provide abundant, accessible nature for all residents and corresponding health and well-being outcomes. Urban biodiversity planning and biophilic cities have significant synergies in their goals and the means necessary to achieve them. In this paper, we identify three key ways by which the urban biodiversity planning process can support biophilic cities objectives: engaging the local community; identifying science-based, quantitative goals; and setting priorities for action. Urban biodiversity planning provides evidence-based guidance, tools, and techniques needed to design locally appropriate, pragmatic habitat enhancements that support biodiversity, ecological health, and human health and well-being. Developing these multi-functional, multi-benefit strategies that increase the abundance of biodiverse nature in cities has the potential at the same time to deepen and enrich our biophilic experience in daily life.

As municipalities and water-quality regulatory agencies have implemented programs and policies to improve management of the trash loading to storm drain conveyances, there has been increased interest in using a common set of methods to quantify the effectiveness of management actions. To create a foundation for developing a consistent, standardized approach to trash monitoring statewide, the project team performed a method comparison analysis, based on two seasons of fieldwork. This analysis facilitated the assessment of the accuracy, repeatability, and efficiency of some already developed trash monitoring methodologies already in use, as well as help to investigate a new, innovative method (cf. Fielding Testing Report on trashmonitoring.org). Methods developed by the Bay Area Stormwater Management Agencies Association (BASMAA) for use in the San Francisco Bay Area were compared to methods developed by the Southern California Stormwater Monitoring Coalition (SMC) for use in coastal southern California. One of the chief goals of these comparisons was to understand the similarities and differences between the already existing methods for detecting, quantifying, and characterizing trash in selected environments. Readers will find that the data bear out remarkable levels of accuracy and precision with quantitative metrics that help to align methods and management concerns. Furthermore, the degree of correlation among tested methods were especially high, offering greater opportunities for inter-method comparisons.

The findings of this project are intended for use by public agencies, non-profit organizations, private consultants, and all of their various partners in informing a statewide effort to adopt rigorous, standardized monitoring methods to support the State Water Board’s Trash Amendments. Over the next couple of decades, such public mandates will require all water bodies in California to achieve water quality objectives for trash.

This report describes the amount and distribution of aquatic resources in the Coyote Creek watershed, Santa Clara County, California, and presents the first reassessment of stream ecosystem conditions using a watershed approach and the California Rapid Assessment Method (CRAM). Field work was conducted in 2020, ten years after the baseline watershed assessment completed in 2010.

Trash has received renewed focus in recent years as policy makers, public agencies, environmental organizations, and community groups have taken many steps towards trash quantification and management across California. The range of management actions is matched by the diversity of monitoring approaches, designed to determine key attributes associated with trash pollution on California’s lands and in its waterways.

This report describes the field testing associated with a project designed to validate the accuracy, precision, and practicality of several trash monitoring methods, practiced across the state. Additionally, the project measured the efficacy of a novel monitoring method designed to detect trash via remote sensing and machine learning. Readers will find details about each respective method -- the specific approach to
landscape characterization, the qualitative or quantitative measures undertaken, the team-based quality assurance for data collection -- as well as the approach that the testing team adopted to ensure efficient, accurate, and useful validation of the methods.

Because the validation efforts integrated multiple methods, using multiple teams at a selection of common sites, the field testing report yields useful statistical information not only about each method individually, but about the comparability of the results. The report illustrates the
correlation factor associated with different forms of trash metrics, associated with different methods practiced on the same assessment sites. The results illustrated a generally high degree of correlation among different methods, which promises opportunities to compare results meaningfully across methods.

Furthermore, this field testing report provides quantitative measures to illustrate the repeatability of each method, the differences and insights yielded by assessment site sizing criteria varying among methods, the transferability / teach-ability of each method among trash monitoring practitioners, and how the degrees of accuracy might aid programs in performing mass balance analysis of known sources
to trash detected in a given site.

Regarding innovation, the project team leveraged multiple on-the-ground methods and special testing scenarios to compare conventional and novel (aerial) assessments to measure the relative accuracy and precision of this emergent technology that might address some of the resource constraints that currently limit the broader or more frequent deployment of conventional trash assessment methods. The analyses captured in this field testing report offer specific quantitative measures of the accuracy (bias), precision (repeatability), practicality and cost associated with each method. This information is subsequently used to inform a companion summary analysis found in the Trash Monitoring Playbook, which is designed to evaluate the applicability of the monitoring methods to address classes of
monitoring questions.

Wildfires can be extremely destructive to communities and ecosystems. However, the full scope of the ecological damage is often hard to assess, in part due to limited information on the types of chemicals introduced to affected landscapes and waterways. The objective of this study was to establish a sampling, analytical, and interpretive framework to effectively identify and monitor contaminants of emerging concern in environmental water samples impacted by wildfire runoff. A nontargeted analysis consisting of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC/TOF-MS) was conducted on stormwater samples from watersheds in the City of Santa Rosa and Sonoma and Napa Counties, USA, after the three most destructive fires during the October 2017 Northern California firestorm. Chemicals potentially related to wildfires were selected from the thousands of chromatographic features detected through a screening method that compared samples from fire-impacted sites versus unburned reference sites. This screening led to high confidence identifications of 76 potentially fire-related compounds. Authentic standards were available for 48 of these analytes, and 46 were confirmed by matching mass spectra and GC × GC retention times. Of these 46 compounds, 37 had known commercial and industrial uses as intermediates or ingredients in plastics, personal care products, pesticides, and as food additives. Nine compounds had no known uses or sources and may be oxidation products resulting from burning of natural or anthropogenic materials. Preliminary examination of potential toxicity associated with the 46 compounds, conducted via online databases and literature review, indicated limited data availability. Regional comparison suggested that more structural damage may yield a greater number of unique, potentially wildfire-related compounds. We recommend further study of post-wildfire runoff using the framework described here, which includes hypothesis-driven site selection and nontargeted analysis, to uncover potentially significant stormwater contaminants not routinely monitored after wildfires and inform risk assessment. 

This effort is intended to provide planning-level regional guidance for placement of green stormwater infrastructure (GSI) in Livermore-Amador Valley. This work identifies potential GSI locations and quantifies contaminant load and stormwater runoff volume reduction benefits through the application of GreenPlan-IT, a planning tool developed by the San Francisco Estuary Institute and regional partners. Ultimately, the urban greening analysis presented in this report is intended to help enhance stream and watershed resilience, reduce peak flows, and improve water quality.

The physical and chemical properties of microplastics and their environmental distributions may provide clues about their sources and inform their fate. We demonstrate the value of extensive monitoring of microplastics in an urban bay, San Francisco Bay. Surface water, fish, sediment, stormwater runoff, and treated wastewater were sampled across the bay and adjacent national marine sanctuaries (NMS). We found microplastics and other anthropogenic microdebris (“microdebris”) in all sample types. Concentrations were higher in the bay than in the NMS, and within the bay, concentrations were higher during the wet season than during the dry season. The fate of microdebris varied depending on their morphologies and densities: fibers were dominant in fish, black rubbery fragments were common in sediment, as were fibers, while buoyant fragments and fibers were widely observed in surface waters. Notably, we found large amounts of black rubbery fragments, an emerging contaminant, in stormwater. Moreover, stormwater was a significant pathway of microdebris, with concentrations roughly 140 times greater than those found in wastewater, which was dominated by fibers. Overall, we demonstrate the value of multimatrix regional monitoring to evaluate the sources and fate of microplastics, which can inform effective mitigation for other urban bays around the world.

 

Urban nature—such as greenness and parks—can alleviate distress and provide space for safe recreation during the COVID-19 pandemic. However, nature is often less available in low-income populations and communities of colour—the same communities hardest hit by COVID-19. In analyses of two datasets, we quantified inequity in greenness and park proximity across all urbanized areas in the United States and linked greenness and park access to COVID-19 case rates for ZIP codes in 17 states. Areas with majority persons of colour had both higher case rates and less greenness. Furthermore, when controlling for sociodemographic variables, an increase of 0.1 in the Normalized Difference Vegetation Index was associated with a 4.1% decrease in COVID-19 incidence rates (95% confidence interval: 0.9–6.8%). Across the United States, block groups with lower-income and majority persons of colour are less green and have fewer parks. Our results demonstrate that the communities most impacted by COVID-19 also have the least nature nearby. Given that urban nature is associated with both human health and biodiversity, these results have far-reaching implications both during and beyond the pandemic.

Related data: https://www.sfei.org/data/nature-equity-covid-2021

Conceptual models developed for selected San Francisco Bay margin areas (referred to as priority margin units, or PMUs) have identified shiner surfperch as a crucial indicator of PCB impairment, due to their explicit inclusion as an indicator species in the PCBs TMDL, importance as a popular sport fish species, tendency to accumulate high PCB concentrations, site fidelity, and other factors. The conceptual models recommend periodic monitoring of shiner surfperch to track trends in the PMUs, and as the ultimate indicator of progress in reduction of impairment. The objectives of this study were to 1) establish baselines for long-term monitoring of PCB concentrations in shiner surfperch in four PMUs, and 2) understand local spatial variation in shiner PCB concentrations to support optimization of the long-term sampling design. This study also provided valuable information on the presence of shiner surfperch and other species in the PMUs. 

The San Francisco Bay polychlorinated biphenyl (PCB) and mercury (Hg) total maximum daily loads (TMDLs) call for implementation of control measures to reduce PCB and Hg loads entering the Bay via stormwater. In 2009, the San Francisco Bay Regional Water Quality Control Board (Regional Water Board) issued the first Municipal Regional Stormwater Permit (MRP). This MRP contained a provision aimed at improving information on stormwater pollutant loads in selected watersheds (Provision C.8.) and piloted a number of management techniques to reduce PCB and Hg loading to the Bay from smaller urbanized tributaries (Provisions C.11. and C.12.). To address C8, a previously developed fixed station loads monitoring technique was refined that incorporated turbidity and stage sensors recording at 5-15 minute intervals with the collection of velocity and water samples using both manual and auto sampling techniques to compute loads. In 2015, the Regional Water Board issued the second iteration of the MRP. “MRP 2.0” placed an increased focus on identifying those watersheds, source areas, and source properties that are potentially the most polluted and are therefore most likely to be cost-effective areas for addressing load-reduction requirements.

This document presents potential products and methods for monitoring a suite of tidal wetland habitat indicators designated for the Montezuma Wetlands Project using remote sensing technology. This document can also serve as a starting place for the Technical Advisory Committee of the San Francisco Estuary Regional Monitoring Program (WRMP) to develop a set of regional protocols for monitoring the same or similar habitat indicators.

The overarching goal of the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) is to answer the highest priority scientific questions faced by managers of Bay water quality. The RMP is an innovative collaboration between the San Francisco Bay Regional Water Quality Control Board, the regulated discharger community, the San Francisco Estuary Institute, and many other scientists and interested parties. The purpose of this document is to provide a concise overview of recent RMP activities and findings, and a look ahead to significant products anticipated in the next two years. The report includes a description of the management context that guides the Program; a brief summary of some of the most noteworthy findings of this multifaceted Program; and a summary of progress to date and future plans for addressing priority water quality topics.

This report contains information on the late summer/early fall field sampling efforts conducted
by the Marine Pollution Studies Lab at Moss Landing Marine Labs (MPSL-MLML) in support of
the San Francisco Bay Regional Monitoring Program (RMP) North Bay (San Pablo and Suisun
Bays) Margins study. The North Bay Margins is the third and final round of a larger San
Francisco Bay study collecting sediment and water in shallow margin areas of the bay. The first
round was conducted in Central Bay in 2015 and second round in South Bay in 2017. The work
was contracted through the San Francisco Estuary Institute (SFEI) to the San Jose State
University Research Foundation (SJSURF).
This report includes sample collections over a three week period (August 31st through September
16th) in 2020 encompassing two trips. A total of 40 sediment sites were sampled (Appendix A).
Duplicate sediment samples were collected at two sites (SPB039 and SUB25). Detailed sample
counts and protocols can be found in the 2020 RMP Bay Margins Sediment Cruise Plan prepared
by SFEI.

The National Institute of Standards and Technology (NIST) has been collaborating with the San Francisco Bay Estuary Institute (SFEI) since 2009, providing biobanking services at the NIST Biorepository in Charleston, South Carolina in support of their ongoing water quality monitoring program, the Regional Monitoring Program for Water Quality in the San Francisco Bay (RMP). Specimens (bivalve tissue, bird egg contents, fish tissue and sediment) are collected and processed by SFEI-partnering institutions according to their established protocols and shipped to the NIST Biorepository for archival. This report outlines NIST's role in the project, describes collection and processing protocols developed by SFEI and their collaborators, details shipping and archival procedures employed by biorepository staff and provides an inventory of the collection maintained by NIST from 2009 to 2020.

The resilience of San Francisco Bay shore habitats, such as tidal marshes and mudflats, is essential to all who live in the Bay Area. Tidal marshes and tidal flats (also known as mudflats) are key components of the shore habitats, collectively called baylands, which protect billions of dollars of bay-front housing and infrastructure (including neighborhoods, business parks, highways, sewage treatment plants, and landfills). They purify the Bay’s water, support endangered wildlife, nurture fisheries, and provide people access to nature within the urban environment. Bay Area residents showed their commitment to restoring these critical habitats when they voted for a property tax to pay for large-scale tidal marsh restoration. However, climate change poses a great threat, because there may not be enough natural sediment supply for tidal marshes and mudflats to gain elevation fast enough to keep pace with sea-level rise.

This report analyses current data and climate projections to determine how much natural sediment may be available for tidal marshes and mudflats and how much supplemental sediment may be needed under different future scenarios. These sediment supply and demand estimates are combined with scientific knowledge of natural physical and biological processes to offer a strategy for sediment delivery that will allow these wetlands to survive a changing climate and provide benefits to people and nature for many decades to come. The approach developed in this report may also be useful beyond San Francisco Bay because shoreline protection, flood risk-management, and looming sediment deficits are common issues facing coastal communities around the world.

Urban-wildland interfaces in the western US are increasingly threatened by the growing number and intensity of wildfires, potentially changing the type of contaminants released into the landscape as more urban structures are burned. In October 2017, the Tubbs, Nuns, and Atlas wildfires devastated communities in Northern California (Figure 1), burning over 8,500 buildings and 210,000 acres of land in the span of 24 days (California Department of Forestry and Fire Protection 2017). Together, these wildfires were the most destructive and costliest fires in the history of California at that time (California Department of Forestry and Fire Protection 2019). 

Post-wildfire monitoring efforts in impacted watersheds typically focus on a few well-established water quality and chemistry concerns (McKee et al. 2018). Few studies go beyond these limited targeted analyses and attempt to identify the multitude of other fire-related compounds that are released from or form as the result of combustion of residential, commercial, and industrial structures in urban-wildland interfaces. Some of these unidentified compounds may be toxic to aquatic ecosystems or human health, and may pose risks to wildlife or in water bodies that act as drinking water supplies to nearby communities.  

California Senate Bill 1263 (2018) tasks the Ocean Protection Council (OPC) with leading statewide efforts to address microplastic pollution, and requires the OPC to adopt and implement a Statewide Microplastics Strategy related to microplastic materials that pose an emerging concern for ocean health. Key questions remain about the sources and pathways of microplastics, particularly to urban runoff, to inform an effective statewide microplastics management strategy. The OPC funded this work to inform these microplastics efforts. The purpose of this project was to build conceptual models that synthesize and integrate our current understanding of microplastic sources and pathways to urban runoff in order to provide future research priorities that will inform how best to mitigate microplastic pollution. Specifically, we developed conceptual models for cigarette butts and associated cellulose acetate fibers (Section 2), fibers other than cellulose acetate (Section 3), single-use plastic foodware and related microplastics (Section 4), and tire particles (Section 5), which were prioritized based on findings from the recent urban stormwater monitoring of microplastics in the San Francisco Bay region. Conceptual models specific to each of these particle types are valuable tools to refine source identification and elucidate potential source-specific data gaps and management options.

Historic and current regional management of watersheds and channels for water supply and flood control across the San Francisco Bay Area has cut off much of the coarse sediment that was historically delivered to the Bay. Here we define coarse sediment as having grain sizes larger than 0.0625 mm, which includes sand, gravel and even cobble, as opposed to fine sediment that includes clay, mud and silt. Future projections indicate that sediment supply will not meet the demand from extant and restored tidal marshes to keep up with sea level rise.

The US EPA Water Quality Improvement Fund Preparing for the Storm grant has funded the Zone 7 Water Agency, the San Francisco Estuary Institute and the San Francisco Bay Joint Venture to support the future development of a successful regional coarse sediment reuse strategy. Development of such a strategy requires an understanding of logistical and regulatory hurdles and identification of key strategies for breaking down barriers. One potential solution for meeting the sediment demand along the Bay margin is to utilize coarse sediment that is removed from flood control channels by public agencies. To-date, very little of this sediment that is removed is beneficially reused for restoration along the Bay shoreline. The current economic and regulatory framework around sediment removal presents many challenges, barriers and lack of incentives for agencies to reuse their sediment.

This document represents a step forward towards beneficially reusing coarse flood control channel sediment by outlining reuse challenges, and identifying incentives for participation and potential solutions.

Effective implementation of urban greening strategies is needed to address legacies of landscape change and environmental degradation, ongoing development pressures, and the urgency of the climate crisis. With limited space and resources, these challenges will not be met through single-issue or individual-sector management and planning. Increasingly, local governments, regulatory agencies, and other urban planning organizations in the San Francisco Bay Area are expanding upon the holistic, portfolio-based, and multi-benefit approaches.

This effort, presented in the Trees and Hydrology in Urban Landscapes report, seeks to build links between stormwater management and urban ecological improvements by evaluating how complementary urban greening activities, including green stormwater infrastructure (GSI) and urban tree canopy, can be integrated and improved to reduce runoff and contaminant loads in stormwater systems. This work expands the capacity for evaluating engineered GSI and non-engineered urban greening within a modeling and analysis framework, with a primary focus on evaluating the hydrologic benefit of urban trees. Insights can inform stormwater management policy and planning. 

Stormwater runoff has been suggested to be a significant pathway of microplastics to aquatic habitats; yet, few studies have quantified microplastics in stormwater. Here, we quantify and characterize urban stormwater runoff from 12 watersheds surrounding San Francisco Bay for anthropogenic debris, including microplastics. Depth-integrated samples were collected during wet weather events. All stormwater runoff contained anthropogenic microparticles, including microplastics, with concentrations ranging from 1.1 to 24.6 particles/L. These concentrations are much higher than those in wastewater treatment plant effluent, suggesting urban stormwater runoff is a major source of anthropogenic debris, including microplastics, to aquatic habitats. Fibers and black rubbery fragments (potentially tire and road wear particles) were the most frequently occurring morphologies, comprising ∼85% of all particles across all samples. This suggests that mitigation strategies for stormwater should be prioritized. As a case study, we sampled stormwater from the inlet and outlet of a rain garden during three storm events to measure how effectively rain gardens capture microplastics and prevent it from contaminating aquatic ecosystems. We found that the rain garden successfully removed 96% of anthropogenic debris on average and 100% of black rubbery fragments, suggesting rain gardens should be further explored as a mitigation strategy for microplastic pollution.

1. Preserving and restoring wildlife in urban areas benefits both urban ecosystems and the well-being of urban residents. While urban wildlife conservation is a rapidly developing field, the majority of conservation research has been performed in wildland areas. Understanding the applicability of wildland science to urban populations and the relative importance of factors limiting species persistence are of critical importance to identifying prescriptive management strategies for restoring wildlife to urban parks.
2. We evaluated how habitat fragmentation, habitat quality and mortality threats influence species occupancy and persistence in urban parks. We chose California quail Callipepla californica as a representative species with potential to respond to urban conservation. We used publicly available eBird data to construct occupancy models of quail in urban parks across their native range, and present an application using focal parks interested in exploring quail reintroduction.
3. Urban parks had a 0.23 ± 0.02 probability of quail occupancy, with greater occupancy in larger parks that were less isolated from potential source populations, had higher shrub cover and had lower impervious cover. Less isolated parks had higher colonization rates, while larger parks had lower extinction rates. These results align with findings across urban ecology showing greater biodiversity in larger and more highly connected habitat patches.
4. A case study highlighted that interventions to increase effective park size and improve connectivity would be most influential for two highly urban focal parks, while changes to internal land cover would have a relatively small impact. Low joint extinction probability in the parks (0.010 ± 0.013) indicated reintroduced populations could persist for some time.
5. Synthesis and applications. We show how eBird data can be harnessed to evaluate the responsiveness of wildlife to urban parks of variable size, connectivity and habitat quality, highlighting what management actions are most needed. Using California quail as an example, we found park size, park isolation and presence of coyotes are all important drivers of whether quail can colonize and persist in parks. Our results suggest reintroducing quail to parks could be successful provided parks are large enough to support quail, and management actions are taken to enhance regional connectivity or periodic assisted colonization is used to supplement local populations.

This report details activities associated with the Regional Monitoring Program North Bay Selenium Study. The  study was designed to monitor two sites for selenium (Se) in clam tissues and water six times between June  2019 and February 2020. This report outlines the sampling activities, personnel, and site locations monitored for  the project. 

The goal of monitoring for selenium in the North Bay tissue and water is to identify leading indicators of change to allow prompt management response to signs of increasing impairment. At the 2016 technical workshop, participants reached a consensus that monitoring sturgeon, clams, and water are all needed to answer management questions. Recommendations for long-term monitoring of these three matrices are detailed in the North Bay Monitoring Design document (Grieb et al. 2018). The purpose of this Sampling and Analysis Plan is to clearly document the sampling design, methods, and responsibilities; and to facilitate coordination among project partners.

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) monitors concentrations of contaminants in fish tissue as indicators of bioaccumulation of contaminants in the Bay. In 2019, the RMP will conduct its eighth round of sport fish monitoring by collecting sport fish samples from various locations in the Bay as a part of routine Status and Trends Monitoring. Add-ons to the routine Status and Trends sport fish monitoring design will include archiving for microplastics and fipronil, as well as additional collections of shiner surfperch in Priority Margin Unit areas (PMUs).

This 2020 CEC Strategy Update is a brief summary document that describes the addition of recently monitored CECs to the tiered risk-based framework. Reviews of findings relevant to San Francisco Bay are provided, as is a discussion of the role of environmental persistence in classifying CECs within the framework. The Strategy is a living document that guides RMP special studies on CECs, assuring continued focus on the issues of highest priority to protecting the health of the Bay. A key focus of the Strategy is a tiered risk-based framework that guides future monitoring proposals. The Strategy also features a multi-year plan indicating potential future research priorities.

This technical report describes the ten-year ambient stream condition reassessment survey design and monitoring plan (or strategy) for the Coyote Creek watershed. Because the reassessment employed (and modified) the 2010 sample draw, essential background information about the original 2010 probability-based survey design, sample draw, and field assessment outcomes were provided.

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) has recently focused attention on better characterization of contaminants in nearshore “margin” areas of San Francisco Bay. The margins of the Lower South Bay are mudflats and shallow regions that receive direct discharges of stormwater and wastewater; as a result, they may have higher levels of urban contaminants than the open Bay. In the summer of 2017, the RMP collected samples of margin
sediment in the South and Lower South Bay for analysis of legacy contaminants. The study described here leveraged that sampling effort by adding monitoring of sediment and water for two additional sets of emerging contaminants: 1) current-use pesticides; and 2) fragrance ingredients including the polycyclic musk galaxolide, as well as a range of other commonly detected emerging contaminants linked to toxicity concerns such as endocrine disruption.

This report describes the Delta Landscapes Primary Production project, which quantifies how landscape change in the Delta has altered the quantity and character of primary production. Combining historical and modern maps with simple models of production for five dominant plant and algae groups, we estimate primary production across the hydrologically connected Delta. We evaluate changes in primary production over time (between the early 1800s and early 2000s), between wet and dry years, and with future targets for landscape-scale restoration. For managers in the Delta, restoring historical patterns of primary productivity is a means to better support native fish and other wildlife. To better equip decision makers in managing for improved primary production, this study offers historical context and the best available science on the relative production value of habitat types and their configurations. 

The beneficial reuse of dredged sediment is one strategy in a broader portfolio that is being developed for San Francisco Bay to help marshes adapt to rising sea level. Dredged sediment is currently being used in restoration projects around the Bay, but additional sediment is needed to meet the demand. The guidelines for determining if sediment is appropriate for beneficial reuse were developed twenty years ago. As part of assessing the role of dredged sediment in Bay restoration and adaptation strategies, the Regional Monitoring Program for Water Quality (RMP) and stakeholders recognized the need to revisit the beneficial reuse guidelines for dredged sediment. In September 2019, the RMP convened a workshop that included four technical experts to review the beneficial reuse guidelines. The experts were asked to answer three questions: 1) Are the current screening guidelines appropriate for beneficial reuse? 2) Is the current screening process appropriate and adequate? If not, what are your recommendations for improving it? and 3) How should bioaccumulation potential be addressed for the beneficial reuse of sediment? Based on the discussion of these three questions, six recommendations emerged from the workshop.

To inform mitigation strategies and understand how microplastics affect wildlife, research is focused on understanding the sources, pathways, and occurrence of microplastics in the environment and in wildlife. Microplastics research entails counting and characterizing microplastics in nature, which is a labor‐intensive process, particularly given the range of particle sizes and morphologies present within this diverse class of contaminants. Thus, it is crucial to determine appropriate sampling methods that best capture the types and quantities of microplastics relevant to inform the questions and objectives at hand. It is also critical to follow protocols with strict quality assurance and quality control (QA/QC) measures so that results reflect accurate estimates of microplastic contamination. Here, we assess different sampling procedures and QA/QC strategies to inform best practices for future environmental monitoring and assessments of exposure. We compare microplastic abundance and characteristics in surface‐water samples collected using different methods (i.e., manta and bulk water) at the same sites, as well as duplicate samples for each method taken at the same site and approximate time. Samples were collected from 9 sampling sites within San Francisco Bay, California, USA, using 3 different sampling methods: 1) manta trawl (manta), 2) 1‐L grab (grab), and 3) 10‐L bulk water filtered in situ (pump). Bulk water sampling methods (both grab and pump) captured more microplastics within the smaller size range (<335 μm), most of which were fibers. Manta samples captured a greater diversity of morphologies but underestimated smaller‐sized particles. Inspection of pump samples revealed high numbers of particles from procedural contamination, stressing the need for robust QA/QC, including sampling and analyzing laboratory blanks, field blanks, and duplicates. Choosing the appropriate sampling method, combined with rigorous, standardized QA/QC practices, is essential for the future of microplastics research in marine and freshwater ecosystems.

California mussels (Mytilus californianus and hybrid Mytilus galloprovincialis / Mytilus trossulus) and Asian clams (Corbicula fluminea) were collected at multiple sites in San Francisco Bay. Mussels from a reference area with minimal urban influence were also deployed in cages for 90 days at multiple sites within the Bay prior to collection.Mussels from the reference time zero site, Bodega Head, had some of the lowest microparticle levels found in this study, along with resident clams from the San Joaquin and Sacramento Rivers and mussels transplanted to Pinole Point. The highest concentrations of microparticles were in mussels transplanted to Redwood Creek and Coyote Creek. The results of this study and current literature indicate that bivalves may not be good status and trends indicators of microplastic concentrations in the Bay unless the interest is in human health exposure via contaminated bivalve consumption.

We present a model to predict the long-term distribution and concentrations of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in estuaries comprising multiple intercommunicated sub-embayments. To that end, a mass balance model including rate constants and time-varying water inputs was designed to calculate levels of these compounds in water and sediment for every sub-embayment. Subsequently, outflows and tidal water exchanges were used to interconnect the different regions of the estuary. To calculate plausible risks to population, outputs of the model were used as inputs in a previously designed model to simulate concentrations of PFOA and PFOS in a sport fish species (Cymatogaster aggregata). The performance of the model was evaluated by applying it to the specific case of San Francisco Bay, (California, USA), using 2009 sediment and water sampled concentrations of PFOA and PFOS in North, Central and South regions. Concentrations of these compounds in the Bay displayed exponential decreasing trends, but with different shapes depending on region, compound, and compartment assessed. Nearly stable PFOA concentrations were reached after 50 years, while PFOS needed close to 500 years to stabilize in sediment and fish. Afterwards, concentrations stabilize between 4 and 23 pg/g in sediment, between 0.02 and 44 pg/L in water, and between 7 and 104 pg/g wet weight in fish, depending on compound and region. South Bay had the greatest final concentrations of pollutants, regardless of compartment. Fish consumption is safe for most scenarios, but due to model uncertainty, limitations in monthly intake could be established for North and South Bay catches.

In the summer of 2017, open Bay water samples were collected during the RMP Status and Trends Water Cruise. Samples were analyzed for 19 neonicotinoids and metabolites. The only neonicotinoid detected was imidacloprid, an active ingredient used in both urban and agricultural applications. Imidacloprid was detected at a single site above the method detection limits (2.2-2.6 ng/L) in Lower South Bay at a level of 4.2 ng/L. This value is within the range of concentrations found in a separate RMP study in water samples collected from the South and Lower South Bay margins in 2017. Imidacloprid was detected at 3 of 12 of the margin sites at levels between 3.9 and 11 ng/L; no other neonicotinoids were detected. Of note, these RMP studies appear to represent the first evaluation of ambient neonicotinoid concentrations in an estuarine environment in the nation.