Characterization of brominated, chlorinated, and phosphate flame retardants in San Francisco Bay, an urban estuary

Science of the Total Environment (Elsevier) | February 20th, 2019

Flame retardant chemical additives are incorporated into consumer goods to meet flammability standards, and many have been detected in environmental matrices. A uniquely

Flame retardant chemical additives are incorporated into consumer goods to meet flammability standards, and many have been detected in environmental matrices. A uniquely wide-ranging characterization of flame retardants was conducted, including polybrominated diphenyl ethers (PBDEs) and 52 additional brominated, chlorinated, or phosphate analytes, in water, sediment, bivalves, and harbor seal blubber of San Francisco Bay, a highly urbanized estuary once considered a hot spot for PBDE contamination. Among brominated flame retardants, PBDEs remained the dominant contaminants in all matrices, though declines have been observed over the last decade following their phase-out. Hexabromocyclododecane (HBCD) and other hydrophobic, brominated flame retardants were commonly detected at lower levels than PBDEs in sediment and tissue matrices. Dechlorane Plus (DP) and related chlorinated compounds were also detected at lower levels or not at all across all matrices. In contrast, phosphate flame retardants were widely detected in Bay water samples, with highest median concentrations in the order TCPP > TPhP > TBEP > TDCPP > TCEP. Concentrations in Bay water were often higher than in other estuarine and marine environments. Phosphate flame retardants were also widely detected in sediment, in the order TEHP > TCrP > TPhP > TDCPP > TBEP. Several were present in bivalves, with levels of TDCPP comparable to PBDEs. Only four phosphate flame retardants were detected in harbor seal blubber: TCPP, TDCPP, TCEP, and TPhP. Periodic, multi-matrix screening is recommended to track contaminant trends impacted by changes to flammability standards and manufacturing practices, with a particular focus on contaminants like TDCPP and TPhP that were found at levels comparable to thresholds for aquatic toxicity.

Characterization of Sediment Contamination in Central Bay Margin Areas

San Francisco Estuary Institute (SFEI) | July 2nd, 2018

The Bay margins (i.e., mudflats and adjacent shallow areas of the Bay) are important habitats where there is high potential for wildlife to be exposed to contaminants. H

The Bay margins (i.e., mudflats and adjacent shallow areas of the Bay) are important habitats where there is high potential for wildlife to be exposed to contaminants. However, these areas are not routinely sampled due to logistical considerations. In 2015, the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) conducted a survey of margin areas in Central Bay to determine ambient concentrations of contaminants in sediment in these areas. The results generally confirmed the current conceptual model expectation that the margin sediments are often more contaminated that those in the subtidal open bay, with PCBs showing the largest differences. These differences between Central Bay margins and open water areas are likely the largest to be found in San Francisco Bay, as margins in other bay segments generally account for more of the total area and the adjacent land use is less heavily industrial. The ambient data provide a useful baseline context against which the severity of contamination at specific sites can be compared. The baseline data will also be useful in setting targets and tracking improvements in watershed loads and their nearfield receiving waters, or for appropriate re-use or disposal of dredged sediment. These spatially unbiased data can also improve estimates of mean concentrations and contaminant inventories in margins. For example, based on data from this study, contamination in the margin areas accounts for ~20% of PCBs in Central Bay which is disproportionately high compared to the margin area (5% of Central Bay). Given a large inventory of contaminants in the open bay compared to annual loads, changes may be difficult to see at the bay scale in the short- and mid-term. However, with margins’ smaller inventories and greater proximity to likely sources, improvements in margin sediments may be easier to observe. This ambient sampling effort also identified or verified one expected area of very high PCB concentrations which had not been previously measured. However, the randomized monitoring design used for the Central Bay study was not ideal for identifying “hot spots”. Future studies with a goal of detecting hot spots should use deterministic sampling designs.

Characterization of Sediment Contamination in South Bay Margin Areas

San Francisco Estuary Institute (SFEI) | November 15th, 2019

The Bay margins (i.e., mudflats and adjacent shallow areas of the Bay) are important habitats where there is high potential for wildlife to be exposed to contaminants. Ho

The Bay margins (i.e., mudflats and adjacent shallow areas of the Bay) are important habitats where there is high potential for wildlife to be exposed to contaminants. However, until recently, these areas had not been routinely sampled by the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) due to logistical considerations. In 2015, the RMP conducted a spatially-distributed characterization of surface sediment contamination and ancillary characteristics within the RMP-defined Central San Francisco Bay margin areas. This was repeated in 2017 within South Bay, which for this report refers to the area collectively encompassing Upper South Bay (usually just called the “South Bay” segment in the Bay RMP, “Upper” added here to distinguish from the combined area), Lower South Bay, and “Extreme” Lower South Bay (previously named “Southern Sloughs”) margin areas.  Findings from the 2015 survey of margin areas in Central Bay (Yee et al., 2017) showed contamination in the margin areas accounted for 20% of the PCB mass in Central Bay, which is disproportionately high compared to margin area (5% of Central Bay). Central Bay watersheds contains many of the oldest and most industrialized urban environments within the Bay Area. There was a significant difference in mean contaminant concentrations in sediment from margins and nearby open water areas. In contrast, for South Bay, margins are more proximate to open water areas and represent a greater percentage of the overall Bay surface area. Therefore, as hypothesized, in the South Bay more uniform distributions were found, likely in part due to these physical factors. Average concentrations in South Bay margins were lower than in Central Bay margins, which was also hypothesized, because South Bay watersheds contain more recent industrial development and relatively less older industrial areas as a percentage of total area (~2% vs 5% for Central Bay watersheds). Although combined loads of PCBs from the South Bay watersheds are about 40% higher than from Central Bay areas, their total area is over 5 times larger, and their total runoff volume is more than double.  Ambient margins data in South Bay provide a context against which the severity of contamination at specific sites can be compared. The baseline data could also be useful in setting targets and tracking improvements in watershed loads and their nearfield receiving waters, or for appropriate assessment of re-use or disposal of dredged sediment. These spatially distributed data also provide improved estimates of mean concentrations and contaminant inventories in margins. Based on data from this study, contamination in the margin areas accounts for 35% of PCB mass in the upper 15 cm of surface sediments in South Bay, which is approximately proportional to the relative area of the margin (34% of the region). In contrast, margins only contain 30% of the mercury mass in South Bay, somewhat less than their proportional area.  Given the large inventory of contaminants in the open Bay compared to annual loads, changes may be difficult to see in the open Bay in the short- and mid-term. However, due to their smaller inventories and closer proximity to likely sources and loading pathways, improvements in margin sediments may potentially be detected more easily or sooner as loads are reduced, even if South Bay margins are better connected and more similar in concentrations to adjacent open water areas than in Central Bay. 

Coagulant and Sorbent Efficacy in Removing Mercury from Surface Waters in the Cache Creek Watershed, California

U.S. Geological Survey (USGS) | February 25th, 2019

Cache Creek drains part of northern California’s Coast Ranges and is an important source of mercury (Hg) to the Sacramento–San Joaquin Delta. Cache Creek is c

Cache Creek drains part of northern California’s Coast Ranges and is an important source of mercury (Hg) to the Sacramento–San Joaquin Delta. Cache Creek is contaminated with Hg from several sources, including historical Hg and gold mines, native Hg in the soils, and active mineral springs. In laboratory experiments in a study conducted by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, the use of coagulants and sorbents to immobilize Hg in water samples from high- concentration sources in the Cache Creek watershed was investigated. Three sites were selected for the collection of surface-water samples containing high and low concentrations of particulate-associated Hg. The high-particulate Hg samples were collected from Cache Creek Settling Basin duringstormflow conditions. The low-particulate Hg samples werecollected from two geochemically contrasting sites duringbase-flow conditions (downstream from a geothermal springand at the emergence point of a connate-water spring). Three coagulants were chosen for laboratory testing with the high-particulate sample— (1) ChitoVanTM HV 1.5 percent (shell based), (2) FerralyteTM 8131 (ferric sulfate based), and (3) UltrionTM 8186 (aluminum based). Each coagulant was tested at various dose amounts to determine the optimum dose rate for the high-particulate sample. The low-particulate source samples were passed through three sorbents— (1) chitosan flakes, (2) coconut shell-based activated carbon,and (3) coal-based activated carbon. In-line columns were packed with each material, and the untreated sample waspassed through each column at three different flow rates (0.1,0.5, and 1.0 liter per minute, L/min). For dose rates used in this study, ChitoVanTM reduced turbidity of the particulate sample by 85–91 percent, FerralyteTM reduced turbidity by 54–93 percent, and UltrionTMreduced turbidity by greater than 90 percent. At the lowest dose rate, ChitoVanTM achieved a 59- to 61-percent reduction in whole-water methylmercury (MeHg) concentrations and a 71- to 75-percent decrease in whole-water total mercury  (THg) concentrations. FerralyteTM achieved a 37- to 48-percent decrease in whole-water MeHg concentrations and a 37- to 48-percent reduction in whole-water THg concentrations. UltrionTM achieved a greater than 90-percent decrease in whole-water MeHg and THg concentrations. Mercury removal from the low-particulate samples was less efficient for the sorbent materials compared to the coagulants; less than 30 percent of THg was removed from any 500-milliliter aliquot using sorbent materials. The coal-based sorbent was the most versatile of the sorbents, removing THg to a similar extent from both low-particulatesource waters. The chitosan sorbent was the most effective atremoving THg from the low-particulate stream sample, but less effective for the low-particulate connate-spring sample. The Hg removal efficiency of the coconut sorbent decreasedquickly compared to the other two sorbents, indicating that sorption may be limited by the short contact times evaluated in this study.

Comparing imidacloprid, clothianidin, and azoxystrobin runoff from lettuce fields using a soil drench or treated seeds in the Salinas Valley, California

Environmental Pollution (Elsevier) | October 10th, 2022

Neonicotinoid insecticide use has increased over the last decade, including as agricultural seed treatments (application of chemical in a coating to the seed prior to pla

Neonicotinoid insecticide use has increased over the last decade, including as agricultural seed treatments (application of chemical in a coating to the seed prior to planting). In California, multiple crops, including lettuce, can be grown using neonicotinoid treated seeds or receive a direct neonicotinoid soil application (drenching) at planting. Using research plots, this study compared pesticide runoff in four treatments: (1) imidacloprid seed treatment; (2) clothianidin seed treatment; (3) imidacloprid drench and an azoxystrobin seed treatment; and (4) a control with no pesticidal treatment. Neonicotinoid and azoxystrobin concentrations were measured in surface water runoff during six irrigations events in the 2020 growing seasons. Results showed runoff concentrations up to 1308 (±1200) ng L−1 for imidacloprid drench treatment, 431 (±100) ng L−1 for clothianidin seed treatment, 135 (±60) ng L−1 for imidacloprid seed treatment, 13 (±10) ng L−1 for azoxystrobin seed treatment (treatments averaged). The percent of applied mass in runoff over the entire sampling period varied by compound; the imidacloprid seed treatment and drench were similar (0.015 and 0.019%, respectively) to the clothianidin seed treatment (0.036%) while the azoxystrobin seed treatment was much higher (15%). Although the proportion of imidacloprid in runoff was similar for imidacloprid treatments, the mass applied during soil drench was > 4x the amount applied from the imidacloprid seed treatment. Surface soils were collected before planting and at the end of the trial. The neonicotinoids were detected in soil throughout the study and average maximum concentrations were 9–13 ng g−1; azoxystrobin was detected in only two soils at concentrations up to 0.57 ng g−1. These results elucidate the comparative mass runoff resulting from planting treated seed and soil drench applications and highlight the value of additional work to characterize off-site transport from the many commodities that may be utilizing treated seeds.

Concentrations for total dissolved solids, arsenic, boron, fluoride, and nitrite-nitrate for wells sampled in the Mojave Water Agency Management Area, California, 1991-97

U.S. Geological Survey (USGS) | January 31st, 2001

Conceptual Model to Support PCB Management and Monitoring in the Emeryville Crescent Priority Margin Unit

San Francisco Estuary Institute (SFEI) | April 3rd, 2017

The 2014 update of the RMP PCB Strategy called for a multi-year effort to implement the recommendations of the PCB Synthesis Report (Davis et al. 2014) pertaining to: 

The 2014 update of the RMP PCB Strategy called for a multi-year effort to implement the recommendations of the PCB Synthesis Report (Davis et al. 2014) pertaining to:  1. identifying margin units that are high priorities for management and monitoring,  2. development of conceptual models and mass budgets for margin units downstream of watersheds where management actions will occur, and  3. monitoring in these units as a performance measure.  The goal of the effort is to inform the review and possible revision of the PCB TMDL and the reissuance of the Municipal Regional Permit for Stormwater (MRP), both of which are tentatively scheduled to occur in 2020. Conceptual model development for four priority margin units (PMUs) that are high priorities for management and monitoring will provide a foundation for establishing effective and efficient monitoring plans to track responses to load reductions and will also help guide planning of management actions. The Emeryville Crescent (the Crescent) is the subject of this report and the first PMU to be studied. 

Conceptual Model to Support PCB Management and Monitoring in the San Leandro Bay Priority Margin Unit Final Report

San Francisco Estuary Institute (SFEI) | November 2nd, 2019

The goal of this report is to answer three questions related to management and monitoring of PCBs in priority margin units. To this end, a conceptual model was develope

The goal of this report is to answer three questions related to management and monitoring of PCBs in priority margin units. To this end, a conceptual model was developed that includes four major elements: 1. loading from the watersheds; 2. initial deposition and retention; 3. processes determining the long-term fate of PCBs in sediment and water; and 4. bioaccumulation in the food web

Conceptual Model to Support PCB Management and Monitoring in the San Leandro Bay Priority Margin Unit, Phase One

San Francisco Estuary Institute (SFEI) | June 1st, 2018

The goal of RMP PCB special studies over the next few years is to inform the review and possible revision of the PCB TMDL and the reissuance of the Municipal Regional P

The goal of RMP PCB special studies over the next few years is to inform the review and possible revision of the PCB TMDL and the reissuance of the Municipal Regional Permit for Stormwater, both of which are tentatively scheduled to occur in 2020. Conceptual model development for a set of four representative priority margin units will provide a foundation for establishing an effective and efficient monitoring plan to track responses to load reductions, and will also help guide planning of management actions. The Emeryville Crescent was the first PMU to be studied in 2015-2016. The San Leandro Bay PMU is second (2016-2017), Steinberger Slough in San Carlos is third (2017), and Richmond Harbor will be fourth (2018). The conceptual model reports for these four PMUs will be developed and presented using a consistent framework, and will build on each other to form an integrated assessment of these four areas. The lessons learned from these analyses will also be more generally applicable to similar contaminated sites on the margins of the Bay.

Contaminant Concentrations in Eggs of Double-crested Cormorants and Forster's Terns from San Francisco Bay: 2002-2012

San Francisco Estuary Institute (SFEI) | May 2nd, 2016

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) conducted an Exposure and Effects Pilot Study (EEPS) to monitor contaminant exposure and ef

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) conducted an Exposure and Effects Pilot Study (EEPS) to monitor contaminant exposure and effects in Bay wildlife. Avian egg monitoring is one tool that was piloted in the EEPS and retained as an element of RMP Status and Trends monitoring. Avian eggs from two species have been monitored: Double-crested Cormorants (Phalacrocorax auritus), a sentinel species for the open waters of the Bay, and Forster’s Terns (Sterna forsteri), a sentinel species for shallow-water habitats on the Bay margins, including managed ponds.