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Journal Article (Peer-Reviewed)
Yarnell, S. M.; Petts, G. E.; Schmidt, J. C.; Whipple, A.; Beller, E. E.; Dahm, C. N.; Goodwin, P.; Viers, J. H. 2015. Functional Flows in Modified Riverscapes: Hydrographs, Habitats and Opportunities. BioScience.

Building on previous environmental flow discussions and a growing recognition that hydrogeomorphic processes are inherent in the ecological functionality and biodiversity of riverscapes, we propose a functional-flows approach to managing heavily modified rivers. The approach focuses on retaining specific process-based components of the hydrograph, or functional flows, rather than attempting to mimic the full natural flow regime. Key functional components include wet-season initiation flows, peak magnitude flows, recession flows, dry-season low flows, and interannual variability. We illustrate the importance of each key functional flow using examples from western US rivers with seasonably predictable flow regimes. To maximize the functionality of these flows, connectivity to morphologically diverse overbank areas must be enhanced in both space and time, and consideration must be given to the sediment-transport regime. Finally, we provide guiding principles for developing functional flows or incorporating functional flows into existing environmental flow frameworks.

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Thompson, B.; Chapman, J. 1997. General guidelines for using the sediment quality triad. Mar. Poll. Bull 34, 368-372 . SFEI Contribution No. 198.
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Cohen, A. N. 1997. Have claw, will travel. Aquatic Nuisance Species Digest 2, 1, 16-17. . SFEI Contribution No. 200.
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Zhu, X.; Munno, K.; Grbic, J.; Werbowski, L. M.; Bikker, J.; Ho, A.; Guo, E.; Sedlak, M.; Sutton, R.; Box, C.; et al. 2021. Holistic Assessment of Microplastics and Other Anthropogenic Microdebris in an Urban Bay Sheds Light on Their Sources and Fate. Environmental Science and Technology Water . SFEI Contribution No. 1060.

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.


Cloern, J. E.; Safran, S. M.; Vaughn, L. Smith; Robinson, A.; Whipple, A.; Boyer, K. E.; Drexler, J. Z.; Naiman, R. J.; Pinckney, J. L.; Howe, E. R.; et al. 2021. On the human appropriation of wetland primary production. Science of the Total Environment 785.

Humans are changing the Earth's surface at an accelerating pace, with significant consequences for ecosystems and their biodiversity. Landscape transformation has far-reaching implications including reduced net primary production (NPP) available to support ecosystems, reduced energy supplies to consumers, and disruption of ecosystem services such as carbon storage. Anthropogenic activities have reduced global NPP available to terrestrial ecosystems by nearly 25%, but the loss of NPP from wetland ecosystems is unknown. We used a simple approach to estimate aquatic NPP from measured habitat areas and habitat-specific areal productivity in the largest wetland complex on the USA west coast, comparing historical and modern landscapes and a scenario of wetland restoration. Results show that a 77% loss of wetland habitats (primarily marshes) has reduced ecosystem NPP by 94%, C (energy) flow to herbivores by 89%, and detritus production by 94%. Our results also show that attainment of habitat restoration goals could recover 12% of lost NPP and measurably increase carbon flow to consumers, including at-risk species and their food resources. This case study illustrates how a simple approach for quantifying the loss of NPP from measured habitat losses can guide wetland conservation plans by establishing historical baselines, projecting functional outcomes of different restoration scenarios, and establishing performance metrics to gauge success.

Hatje, V.; Bruland, K. W.; A. Flegal, R. 2016. Increases in Anthropogenic Gadolinium Anomalies and Rare Earth Element Concentrations in San Francisco Bay over a 20 Year Record. Environ. Sci. Technol. 50 (8).

We evaluated both the spatial distribution of gadolinium (Gd) and other rare earth elements (REE) in surface waters collected in a transect of San Francisco Bay (SFB) and their temporal variations within the Bay over two decades. The REE were preconcentrated using the NOBIAS PA-1 resin prior to analysis by high-resolution inductively coupled plasma mass spectrometry. Measurements revealed a temporal increase in the Gd anomaly in SFB from the early 1990s to the present. The highest Gd anomalies were observed in the southern reach of SFB, which is surrounded by several hospitals and research centers that use Gd-based contrast agents for magnetic resonance imaging. Recent increases in that usage presumably contributed to the order of magnitude increase in anthropogenic Gd concentrations in SFB, from 8.27 to 112 pmol kg–1 over the past two decades, and reach the northeast Pacific coastal waters. These measurements (i) show that “exotic” trace elements used in new high-tech applications, such as Gd, are emerging contaminants in San Francisco Bay and that anthropogenic Gd concentrations increased substantially over a 20 year period; (ii) substantiate proposals that REE may be used as tracers of wastewater discharges and hydrological processes; and (iii) suggest that new public policies and the development of more effective treatment technologies may be necessary to control sources and minimize future contamination by REE that are critical for the development of new technologies, which now overwhelm natural REE anomalies.

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Cohen, A. N.; McGann, M.; Sloan, D. 2000. Invasion by a Japanese marine microorganism in western North America. Hydrobiologia 421, 25-30 . SFEI Contribution No. 343.
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Cohen, A. N. 2004. Invasions in the sea. Park Science 22, 37-41.
Flegal, A. R. 1997. Lead levels in the oceans. Encyclopedia of Environmental Analysis and Remediation(H. Ben-Zvi, editor)John Wiley & Sons, Inc. In press . SFEI Contribution No. 24.
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Hampton, L. M. Thornto; De Frond, H.; Hermabessiere, L.; Miller, E.; de Ruijter, V. N.; Faltynkova, A.; Kotar, S.; Monclús, L.; Siddiqui, S.; Völker, J.; et al. 2022. A living tool for the continued exploration of microplastic toxicity. Microplastics and Nanoplastics 2 (13).

Throughout the past decade, many studies have reported adverse effects in biota following microplastic exposure. Yet, the field is still emerging as the current understanding of microplastic toxicity is limited. At the same time, recent legislative mandates have required environmental regulators to devise strategies to mitigate microplastic pollution and develop health-based thresholds for the protection of human and ecosystem health. The current publication rate also presents a unique challenge as scientists, environmental managers, and other communities may find it difficult to keep up with microplastic research as it rapidly evolves. At present, there is no tool that compiles and synthesizes the data from these studies to allow for visualization, interpretation, or analysis. Here, we present the Toxicity of Microplastics Explorer (ToMEx), an open access database and open source accompanying R Shiny web application that enables users to upload, search, visualize, and analyze microplastic toxicity data. Though ToMEx was originally created to facilitate the development of health-based thresholds to support California legislations, maintaining the database by the greater scientific community will be invaluable to furthering research and informing policies globally. The database and web applications may be accessed at https://microplastics.sccwrp.org/.

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Davis, J. A. 2004. The Long-Term Fate of PCBs in San Francisco Bay. Environmental Toxicology and Chemistry 23, 2396-2409.
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Collins, J. N.; Yee, D.; Davis, J. A. 2002. Mercury and tidal wetland restoration. CalFED Journal . SFEI Contribution No. 339.
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Flegal, A. R.; Scelfo, G. M.; Sanudo-Wilhelmy, S. A.; Ritson, P. I.; Rivera-Duarte, I.; Smith, G. J.; Gordon, M. R. 1996. Metal contamination in San Francisco Bay waters: Historic perturbations, contemporary concentrations, and future considerations. San Francisco Bay: The Ecosystem(J.T. Rollibaugh, ed.)American Association for the Advancement of Science 173-188 . SFEI Contribution No. 12.
Hung, C.; Klasios, N.; Zhu, X.; Sedlak, M.; Sutton, R. 2020. Methods Matter: Methods for Sampling Microplastic and Other Anthropogenic Particles and Their Implications for Monitoring and Ecological Risk Assessment. Integrated Environmental Assessment and Management 16 (6) . SFEI Contribution No. 1014.

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.

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Jabusch, T. W.; Tjeerdema, R. S. 2006. Microbial degradation of penoxsulam in flooded rice field soils. Journal of Agricultural and Food Chemistry 54, 5962-5967.
Sutton, R.; Mason, S. A.; Stanek, S. K.; Willis-Norton, E.; Wren, I. F.; Box, C. 2016. Microplastic contamination in the San Francisco Bay, California, USA. Marine Pollution Bulletin 109 . SFEI Contribution No. 769.

Despite widespread detection of microplastic pollution in marine environments, data describing microplastic abundance in urban estuaries and microplastic discharge via treated municipal wastewater are limited. This study presents information on abundance, distribution, and composition of microplastic at nine sites in San Francisco Bay, California, USA. Also presented are characterizations of microplastic in final effluent from eight wastewater treatment plants, employing varying treatment technologies, that discharge to the Bay. With an average microplastic abundance of 700,000 particles/km2, Bay surface water appears to have higher microplastic levels than other urban waterbodies sampled in North America. Moreover, treated wastewater from facilities that discharge into the Bay contains considerable microplastic contamination. Facilities employing tertiary filtration did not show lower levels of contamination than those using secondary treatment. As textile-derived fibers were more abundant in wastewater, higher levels of fragments in surface water suggest additional pathways of microplastic pollution, such as stormwater runoff.

Mason, S. A.; Garneau, D.; Sutton, R.; Chu, Y.; Ehmann, K.; Barnes, J.; Papazissimos, D.; Rogers, D. L. 2016. Microplastic pollution is widely detected in US municipal wastewater treatment plant effluent. Environmental Pollution 218, 1045-1054.

Municipal wastewater effluent has been proposed as one pathway for microplastics to enter the aquatic environment. Here we present a broad study of municipal wastewater treatment plant effluent as a pathway for microplastic pollution to enter receiving waters. A total of 90 samples were analyzed from 17 different facilities across the United States. Averaging all facilities and sampling dates, 0.05 ± 0.024 microparticles were found per liter of effluent. Though a small value on a per liter basis, even minor municipal wastewater treatment facilities process millions of liters of wastewater each day, yielding daily discharges that ranged from ∼50,000 up to nearly 15 million particles. Averaging across the 17 facilities tested, our results indicate that wastewater treatment facilities are releasing over 4 million microparticles per facility per day. Fibers and fragments were found to be the most common type of particle within the effluent; however, some fibers may be derived from non-plastic sources. Considerable inter- and intra-facility variation in discharge concentrations, as well as the relative proportions of particle types, was observed. Statistical analysis suggested facilities serving larger populations discharged more particles. Results did not suggest tertiary filtration treatments were an effective means of reducing discharge. Assuming that fragments and pellets found in the effluent arise from the 'microbeads' found in many cosmetics and personal care products, it is estimated that between 3 and 23 billion (with an average of 13 billion) of these microplastic particles are being released into US waterways every day via municipal wastewater. This estimate can be used to evaluate the contribution of microbeads to microplastic pollution relative to other sources (e.g., plastic litter and debris) and pathways (e.g., stormwater) of discharge.

Klasios, N.; De Frond, H.; Miller, E.; Sedlak, M.; Rochman, C. M. 2021. Microplastics and other anthropogenic particles are prevalent in mussels from San Francisco Bay, and show no correlation with PAHs. Environmental Pollution 271.

Microplastics are an emerging contaminant of high environmental concern due to their widespread distribution and availability to aquatic organisms. Filter-feeding organisms like bivalves have been identified as particularly susceptible to microplastics, and because of this, it has been suggested bivalves could be useful bioindicators of microplastic pollution in ecosystems. We sampled resident mussels and clams from five sites within San Francisco Bay for microplastics and other anthropogenic microparticles. Cages of depurated mussels (denoted transplants) were also deployed at four sites in the Bay for 90 days to investigate temporal uptake of microplastics and microparticles. Because microplastics can sorb PAHs, and thus may act as a source of these chemicals upon ingestion, transplant mussels and resident clams were also analyzed for PAHs. We found anthropogenic microparticles in all samples at all sites, some of which were identified as microplastics. There was no statistical difference between the mean number of microparticles found in resident and transplant species. There were significant site-specific differences among microparticle abundances in the Bay, with the highest abundances observed in the South Bay. No correlation was found between the number of microparticles and the sum concentrations of PAHs, priority PAHs, or any individual PAH, suggesting the chemical concentrations observed reflect broader chemical trends in the Bay rather than direct exposure through microplastic ingestion. The pattern of spatial distribution of microparticles in transplanted mussels matched that of sediment samples from the Bay, suggesting bivalves could be a useful bioindicator of microplastic abundances in sediment, but not surface water.

Soberón, F. Sánchez; Sutton, R.; Sedlak, M.; Yee, D.; Schuhmacher, M.; Park, J. - S. 2020. Multi-box mass balance model of PFOA and PFOS in different regions of San Francisco Bay. Chemosphere 252 . SFEI Contribution No. 986.

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.

Gilbreath, A.; McKee, L.; Shimabuku, I.; Lin, D.; Werbowski, L. M.; Zhu, X.; Grbic, J.; Rochman, C. 2019. Multi-year water quality performance and mass accumulation of PCBs, mercury, methylmercury, copper and microplastics in a bioretention rain garden. Journal of Sustainable Water in the Built Environment 5 (4) . SFEI Contribution No. 872.

A multiyear water quality performance study of a bioretention rain garden located along a major urban transit corridor east of San Francisco Bay was conducted to assess the efficacy of bioretention rain gardens to remove pollutants. Based on data collected in three years between 2012 and 2017, polychlorinated biphenyls (PCBs) and suspended sediment concentrations (SSCs) were reduced (>90%), whereas total mercury (Hg), methylmercury (MeHg), and copper (Cu) were moderately captured (37%, 49%, and 68% concentration reduction, respectively). Anthropogenic microparticles including microplastics were retained by the bioretention rain garden, decreasing in concentration from 1.6 particles/L to 0.16 particles/L. Based on subsampling at 50- and 150-mm intervals in soil cores from two areas of the unit, PCBs, Hg, and MeHg were all present at the highest concentrations in the upper 100 mm in the surface media layers. Based on residential screening concentrations, the surface media layer near the inlet would need to be removed and replaced annually, whereas the rest of the unit would need replacement every 8 years. The results of this study support the use of bioretention in the San Francisco Bay Area as one management option for meeting load reductions required by San Francisco Bay total maximum daily loads, and provide useful data for supporting decisions about media replacement and overall maintenance schedules.

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Spotswood, E.; Benjamin, M.; Stoneburner, L.; Wheeler, M. 2021. Nature inequity and higher COVID-19 case rates in less green neighbourhoods in the United States. Nature Sustainability 4 (10).

Nature inequity and higher COVID-19 case rates in less green neighbourhoods in the United StatesUrban 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


Shimabuku, I.; Chen, D.; Wu, Y.; Miller, E.; Sun, J.; Sutton, R. 2022. Occurrence and risk assessment of organophosphate esters and bisphenols in San Francisco Bay, California, USA. Science of the Total Environment 813 . SFEI Contribution No. 982.

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.

Wu, J.; Kauhanen, P.; Hunt, J. A.; Senn, D.; Hale, T.; McKee, L. J. . 2019. Optimal Selection and Placement of Green Infrastructure in Urban Watersheds for PCB Control. Journal of Sustainable Water in the Built Environment 5 (2) . SFEI Contribution No. 729.

San Francisco Bay and its watersheds are polluted by legacy polychlorinated biphenyls (PCBs), resulting in the establishment of a total maximum daily load (TDML) that requires a 90% PCB load reduction from municipal stormwater. Green infrastructure (GI) is a multibenefit solution for stormwater management, potentially addressing the TMDL objectives, but planning and implementing GI cost-effectively to achieve management goals remains a challenge and requires an integrated watershed approach. This study used the nondominated sorting genetic algorithm (NSGA-II) coupled with the Stormwater Management Model (SWMM) to find near-optimal combinations of GIs that maximize PCB load reduction and minimize total relative cost at a watershed scale. The selection and placement of three locally favored GI types (bioretention, infiltration trench, and permeable pavement) were analyzed based on their cost and effectiveness. The results show that between optimal solutions and nonoptimal solutions, the effectiveness in load reduction could vary as much as 30% and the difference in total relative cost could be well over $100 million. Sensitivity analysis of both GI costs and sizing criteria suggest that the assumptions made regarding these parameters greatly influenced the optimal solutions. 

If you register for access to the journal, then you may download the article for free through July 31, 2019.

DOI: 10.1061/JSWBAY.0000876

Bǎlan, S. A.; Andrews, D. Q.; Blum, A.; Diamond, M. L.; Fernández, S. Rojello; Harriman, E.; Lindstrom, A. B.; Reade, A.; Richter, L.; Sutton, R.; et al. 2023. Optimizing Chemicals Management in the United States and Canada through the Essential-Use Approach. Environmental Science & Technology 57 (4).

Chemicals have improved the functionality and convenience of industrial and consumer products, but sometimes at the expense of human or ecological health. Existing regulatory systems have proven to be inadequate for assessing and managing the tens of thousands of chemicals in commerce. A different approach is urgently needed to minimize ongoing production, use, and exposures to hazardous chemicals. The premise of the essential-use approach is that chemicals of concern should be used only in cases in which their function in specific products is necessary for health, safety, or the functioning of society and when feasible alternatives are unavailable. To optimize the essential-use approach for broader implementation in the United States and Canada, we recommend that governments and businesses (1) identify chemicals of concern for essentiality assessments based on a broad range of hazard traits, going beyond toxicity; (2) expedite decision-making by avoiding unnecessary assessments and strategically asking up to three questions to determine whether the use of the chemical in the product is essential; (3) apply the essential-use approach as early as possible in the process of developing and assessing chemicals; and (4) engage diverse experts in identifying chemical uses and functions, assessing alternatives, and making essentiality determinations and share such information broadly. If optimized and expanded into regulatory systems in the United States and Canada, other policymaking bodies, and businesses, the essential-use approach can improve chemicals management and shift the market toward safer chemistries that benefit human and ecological health.

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Bruland, K. W.; Miller, L. A. 1995. Organic speciation of silver in marine waters. Environmental Science and Technology 29, 2616-2621 . SFEI Contribution No. 186.
Oros, D. R.; Simoneit, B. R. T.; Mazurek, M. A.; Baham, J. E. 2002. Organic Tracers from Wild Fire Residues in Soils and Rain/River Wash-Out. Water, Air and Soil Pollution 137, p.203-233 . SFEI Contribution No. 479.
Cohen, A. N.; Zabin, C. J. 2009. Oyster shells as vectors for exotic species. Journal of Shellfish Research 28 (1), 163-167 . SFEI Contribution No. 709.
Greenfield, B. K.; Davis, J. A. 2004. A PAH Fate Model for San Francisco Bay. Chemosphere . SFEI Contribution No. 114.
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Flegal, A. R.; Abu-Saba, K. E. 1997. Particulate sources and sinks of dissolved chromium in the San Francisco Bay estuary. Environmental Science and Technology . SFEI Contribution No. 25.
Sadaria, A. M.; Sutton, R.; Moran, K. D.; Teerlink, J.; Brown, J. V.; Halden, R. U. 2017. Passage of fiproles and imidacloprid from urban pest control uses through wastewater treatment plants in northern California. Environmental Toxicology and Chemistry 36, 1473-1482 . SFEI Contribution No. 783.

Urban pest control insecticides, specifically fipronil and its four major degradates (fipronil sulfone, sulfide, desulfinyl, and amide) and imidacloprid, were monitored during drought conditions in eight San Francisco Bay wastewater treatment plants (WWTPs). In influent and effluent, ubiquitous detections were obtained in units of ng/L for fipronil (13-88), fipronil sulfone (1-28), fipronil sulfide (1-5) and imidacloprid (58-306). In influent, 100% of imidacloprid and 62 ± 9% of total fiproles (fipronil and degradates) were present in the dissolved state, with the balance being bound to filter-removable particulates. Targeted insecticides persisted during wastewater treatment, regardless of treatment technology utilized (imidacloprid: 93 ± 17%; total fiproles: 65 ± 11%), with partitioning into sludge (3.7-151.1 μg/kg dry weight as fipronil) accounting for minor losses of total fiproles entering WWTPs. The load of total fiproles was fairly consistent across the facilities but fiprole speciation varied. This first regional study on fiprole and imidacloprid occurrences in raw and treated California sewage revealed ubiquity and marked persistence to conventional treatment of both phenylpyrazole and neonicotinoid compounds. Flea and tick control agents for pets are identified as potential sources of pesticides in sewage meriting further investigation and inclusion in chemical-specific risk assessments. 

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Iknayan, K.; Heath, S.; Terrill, S. B.; Wenny, D. G.; Panlasigui, S.; Wang, Y.; Beller, E. E.; Spotswood, E. 2024. Patterns in bird and pollinator occupancy and richness in a mosaic of urban office parks across scales and seasons. Ecology and Evolution 14 (3).

Urbanization is a leading cause of global biodiversity loss, yet cities can provide resources required by many species throughout the year. In recognition of this, cities around the world are adopting strategies to increase biodiversity. These efforts would benefit from a robust understanding of how natural and enhanced features in urbanized areas influence various taxa. We explored seasonal and spatial patterns in occupancy and taxonomic richness of birds and pollinators among office parks in Santa Clara County, California, USA, where natural features and commercial landscaping have generated variation in conditions across scales. We surveyed birds and insect pollinators, estimated multi-species occupancy and species richness, and found that spatial scale (local, neighborhood, and landscape scale), season, and urban sensitivity were all important for understanding how communities occupied sites. Features at the landscape (distance to streams or baylands) and local scale (tree canopy, shrub, or impervious cover) were the strongest predictors of avian occupancy in all seasons. Pollinator richness was influenced by local tree canopy and impervious cover in spring, and distance to baylands in early and late summer. We then predicted the relative contributions of different spatial scales to annual bird species richness by simulating “good” and “poor” quality sites based on influential covariates returned by the previous models. Shifting from poor to good quality conditions locally increased annual avian richness by up to 6.8 species with no predicted effect on the quality of the neighborhood. Conversely, sites of poor local and neighborhood scale quality in good-quality landscapes were predicted to harbor 11.5 more species than sites of good local- and neighborhood-scale quality in poor-quality landscapes. Finally, more urban-sensitive bird species were gained at good quality sites relative to urban tolerant species, suggesting that urban natural features at the local and landscape scales disproportionately benefited them.

Sedlak, M.; Greig, D. 2012. Perfluoroalkyl compounds (PFCs) in wildlife from an urban estuary. Journal of Environmental Monitoring 14, 146-154.
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Vuckovic, D.; MacDonald, J. A.; Lin, D.; Méndez, M.; Miller, E.; Mitch, W. 2023. Pharmaceuticals, pesticides, and ultraviolet filters in wastewater discharges to San Francisco Bay as drivers of ecotoxicity. Environmental Pollution 336 . SFEI Contribution No. 1153.

Research in the United States evaluating ecotoxic risk to receiving waters posed by contaminants occurring in wastewater discharges typically has focused on measurements of pharmaceuticals and personal care products (PPCPs), with limited evaluations of UV filters and phenylpyrazole and neonicotinoid pesticides. In this study, concentrations of 5 representative pharmaceuticals, 11 pesticides or pesticide degradation products, and 5 ultraviolet filters were measured in 24 h composite samples of six wastewater discharges representing ∼70% of the total wastewater discharged to San Francisco Bay during the summer and fall of 2021. No significant difference was observed between concentrations measured on weekdays vs. weekends. A hydrodynamic model of San Francisco Bay was used to estimate annual average dilution factors associated with different subembayments. With and without considering dilution effects, Risk Quotients were calculated using the 90th percentile of measured concentrations in wastewater effluents and threshold concentrations associated with ecotoxicity. Risk Quotients were highest for the neonicotinoid pesticide, imidacloprid, and exceeded ecotoxicity thresholds in the lower South Bay by a factor of 2.4, even when considering dilution. Compared to commonly measured pharmaceuticals, Risk Quotients for imidacloprid were higher than those for carbamazepine, trimethoprim and diclofenac, and comparable to those for propranolol and metoprolol. Risk Quotients for the pesticide, fipronil, and the UV filter, oxybenzone, were higher than for carbamazepine. The results highlight the need to incorporate pesticides and UV filters with high Risk Quotients into studies in the United States evaluating ecotoxic risk associated with contaminants in municipal wastewater discharges.

Jabusch, T. W.; Tjeerdema, R. S. 2006. Photodegradation of penoxsulam. Journal of Agricultural and Food Chemistry 54, 5958-5961.
Flegal, A. R.; Bruland, K. W.; Sanudo-Wilhelmy, S. A.; Kozelka, P. B. 1997. Physicochemical speciation of lead in South San Francisco Bay. Estuarine, Coastal and Shelf Science 44, 649-658 . SFEI Contribution No. 26.
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Cohen, A. N. 1995. Place Invaders. Energy and Resources News 4, 1-3.
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Cohen, A. N. 1993. Place Invaders. Pacific Discovery (Calif. Acad. Sci.) 46, 22-26.
Oros, D. R. 2002. Polar aromatic biomarkers in the miocene Maritza-East Lignite, Bulgaria. Organic Geo-chemistry . SFEI Contribution No. 476.
Houtz, E. F.; Sutton, R.; Park, J. - S.; Sedlak, M. 2016. Poly- and perfluoroalkyl substances in wastewater: Significance of unknown precursors, manufacturing shifts, and likely AFFF impacts. Water Research . SFEI Contribution No. 780.

In late 2014, wastewater effluent samples were collected from eight treatment plants that discharge to San Francisco (SF) Bay in order to assess poly- and perfluoroalkyl substances (PFASs) currently released from municipal and industrial sources. In addition to direct measurement of twenty specific PFAS analytes, the total concentration of perfluoroalkyl acid (PFAA) precursors was also indirectly measured by adapting a previously developed oxidation assay. Effluent from six municipal treatment plants contained similar amounts of total PFASs, with highest median concentrations of PFHxA (24 ng/L), followed by PFOA (23 ng/L), PFBA (19 ng/L), and PFOS (15 ng/L). Compared to SF Bay municipal wastewater samples collected in 2009, the short chain perfluorinated carboxylates PFBA and PFHxA rose significantly in concentration. Effluent samples from two treatment plants contained much higher levels of PFASs: over two samplings, wastewater from one municipal plant contained an average of 420 ng/L PFOS and wastewater from an airport industrial treatment plant contained 560 ng/L PFOS, 390 ng/L 6:2 FtS, 570 ng/L PFPeA, and 500 ng/L PFHxA. The elevated levels observed in effluent samples from these two plants are likely related to aqueous film forming foam (AFFF) sources impacting their influent; PFASs attributable to both current use and discontinued AFFF formulations were observed. Indirectly measured PFAA precursor compounds accounted for 33%–63% of the total molar concentration of PFASs across all effluent samples and the PFAA precursors indicated by the oxidation assay were predominately short-chained. PFAS levels in SF Bay effluent samples reflect the manufacturing shifts towards shorter chained PFASs while also demonstrating significant impacts from localized usage of AFFF.

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Oram, J. J.; McKee, L. J. .; Davis, J. A.; Hetzel, F. 2007. Polychlorinated biphenyls (PCBs) in San Francisco Bay. Environmental Research 105, 67-86 . SFEI Contribution No. 526.
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Ross, J. R. M.; Oros, D. R. 2004. Polycyclic aromatic hydrocarbons in San Francisco Estuary sediments. Marine Chemistry 86, 169-184 . SFEI Contribution No. 82.
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Weinstein, A.; Cohen, A. N. 1998. The potential distribution and abundance of zebra mussels in California. Dreissena! (New York Sea Grant) 9, 1-3 . SFEI Contribution No. 323.
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Greenfield, B. K.; Hrabik, T. R.; Harvey, C. J.; Carpenter, S. R. 2000. Predicting mercury levels in fish: use of water chemistry, trophic ecology, and spatial traits. Canadian Journal of Fisheries and Aquatic Sciences 58, 1419 -1429 . SFEI Contribution No. 306.
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Cloern, J. E.; Robinson, A.; Richey, A.; Grenier, J. Letitia; Grossinger, R. M.; Boyer, K. E.; Burau, J.; Canuel, E.; DeGeorge, J. F.; Drexler, J. Z.; et al. 2016. Primary Production in the Delta: Then and Now. San Francisco Estuary and Watershed Science 14 (3).

To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical Delta (pre-1850). Here we describe an approach for using these metrics of land use change to: (1) produce the first quantitative estimates of how Delta primary production and the relative contributions from five different producer groups have been altered by large-scale drainage and conversion to agriculture; (2) convert these production estimates into a common currency so the contributions of each producer group reflect their food quality and efficiency of transfer to consumers; and (3) use simple models to discover how tidal exchange between marshes and open water influences primary production and its consumption. Application of this approach could inform Delta management in two ways. First, it would provide a quantitative estimate of how large-scale conversion to agriculture has altered the Delta's capacity to produce food for native biota. Second, it would provide restoration practitioners with a new approach—based on ecosystem function—to evaluate the success of restoration projects and gauge the trajectory of ecological recovery in the Delta region.

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Gunther, A. J.; O'Connor, J. M.; Davis, J. A. 1992. Priority pollutant loads from effluent discharges to the San Francisco Estuary. Water Environment Research 64, 134-140 . SFEI Contribution No. 171.