We present an assessment of the deposition rates of airborne trace metals onto the Los Angeles Ba... more We present an assessment of the deposition rates of airborne trace metals onto the Los Angeles Basin and adjacent coastal waters. For this purpose, the UCLA Surface Meteorology and Ozone Generation (SMOG) air pollution modeling system has been used to simulate the geographical distributions of trace metals and their deposition fluxes. Calculations were performed for average summer and winter conditions, as well as for extreme meteorological events, in particular, for Santa Ana winds. Thus, a series of simulations were carried out that define the range of meteorological conditions contributing to dry deposition in the region. These predictions have been calibrated and validated using measurements collected in the LA area. Significant spatial and temporal variability are found in trace metal concentrations and deposition rates. Large spatial gradients occur near the coast as well as at the mountainous boundaries of the airshed. Considerable diurnal and seasonal variations in trace metal deposition are also noted. For example, the development of a daytime sea breeze, particularly in the warmer months, leads to greater deposition in the northern and eastern basin as well as in the high desert. A nighttime land breeze, especially in the colder months, enhances deposition onto coastal ocean surfaces. Large particles dominate local trace metal deposition in central urban (and adjacent) areas, while fine particles export metals over regional scales through long-range advection. Since the majority of urban metal deposition occurs on particles larger than 10-mm diameter, routine measurements of PM 10 or PM 2.5 concentrations for air quality characterization may not be reliable indicators of local sources. Some 35-45% of all trace metal emissions are deposited locally within the Los Angeles Basin on an annual basis. Santa Monica Bay and its watersheds receive about 6% of this amount, which can have a significant impact on trace metal concentrations in the surface waters of the bay, primarily through land runoff following storms.
Proceedings of the Water Environment Federation, 2011
In order to help protect the diverse natural resources in the State of California, water quality ... more In order to help protect the diverse natural resources in the State of California, water quality regulatory agencies are developing a new policy to set biological objectives (aka biocriteria). This manuscript is a description of the State's workplan. The policy development will include ten steps including: 1) Reference condition; 2) Stressor response models; 3) Waterbody classification; 4) Stressor identification; 5) Information management; 6) Implementation Plan Development; 7) Rulemaking; 8) Outreach; and 10) Training and standardization. The first five steps are largely technical while the remaining tasks are policy and administrative oriented. The new policy is expected to go before the state regulatory authority in 2013.
Bulletin, Southern California Academy of Sciences, Dec 1, 2007
US EPA. 1993a. Methods for measuring acute toxicity of effluents and receiving waters to freshwat... more US EPA. 1993a. Methods for measuring acute toxicity of effluents and receiving waters to freshwater and marine organisms, Fourth Edition. EPA 600/4-90/027. US Environmental Protection Agency,
Contamination in the coastal zone is closely linked to urbanization and has become a global issue... more Contamination in the coastal zone is closely linked to urbanization and has become a global issue. The coastal aquatic environment is the terminal sink for many chemicals; however, little is known about the occurrence and variation among habitats as well as integrative toxicity for pesticides, i.e., fipronil, and its three major degradates (-desulfinyl, -sulfide, and -sulfone, fiproles hereafter) in sediments in urban coastlines. In the present study, we report results of a random stratified survey for fiproles in surficial sediments in five embayment habitats (strata) along the Southern California Bight (SCB), USA coastline. Fiproles were present in a small areal extent (6.8%) of the SCB embayment, and detected in 14 out of 174 stations with a total concentration of the four analytes ranging from 0.50 to 17.5 μg/kg dry weight. The area-weighted mean concentrations were 3.16 ± 3.37, 0.584 ± 0.558, 0.071 ± 0.103, and 0.005 ± 0.009 μg/kg in brackish estuaries, estuaries, bays, and marinas, respectively, with the results below the detection limits in ports. Fipronil sulfone had the greatest detection frequency (8.05%) and highest mean concentration (3.24 ± 3.36 μg/kg) among the four compounds. A screening-level deterministic risk assessment for invertebrates found that, region-wide, fiproles generally posed an insignificant to low acute risk to the amphipod Eohaustorius estuarius in 7.36% of the SCB embayment area. In addition, high risk to the midge Chironomus dilutus was found in 77.5% of the fiproles-detectable area in the brackish estuary stratum that is a part of the Los Angeles River. Fipronil sulfone was identified as the major contributor of these effects. The results of this study establish a baseline of occurrence and toxicity potential for fiproles in coastal sediments of southern California.
After the United Nation's International Maritime Organization banned the use of organotins in ant... more After the United Nation's International Maritime Organization banned the use of organotins in antifouling products, organic booster biocides were introduced as alternatives to these compounds. The purpose of this study was to measure concentrations of the antifouling agent Irgarol 1051, its major metabolite M1 (aka GS26575), and other antifouling pesticides (diuron, chlorothalonil, dichlofluanid and TCMTB) in San Diego, California, USA region marinas and evaluate the environmental risk posed by these compounds. To our knowledge, this is first study reporting Irgarol concentrations in western areas of the US. Water samples were collected from marina sites in four harbors surrounding greater San Diego,
Emissions of trace metals to the atmosphere and subsequent deposition, either directly to a water... more Emissions of trace metals to the atmosphere and subsequent deposition, either directly to a waterbody surface or indirectly to the watershed as washoff during rainfall, represents a potential source of contamination to surface waters near urban centers. The present study provides measurements of atmospheric concentrations of particle-bound trace metals, and it estimates the dry deposition mass loading of trace metals in coastal watersheds in the Los Angeles, California, USA, air basin. Coarse-particle atmospheric concentrations of metals were measured seasonally using a Noll Rotary Impactor at six urban sites and one nonurban site. Dry deposition fluxes were calculated by summing the product of air concentration and the theoretical deposition velocity for each particle size fraction. Mean fluxes at urban sites ranged from 3.2 to 9.1, 11 to 34, 3.8 to 8.8, 8.3 to 29, and 69 to 228 g/ m 2 /d for chromium, copper, nickel, lead, and zinc, respectively. Mean concentrations and fluxes were significantly higher at urban sites compared with the nonurban site, although differences between urban and nonurban sites were reduced when sampling took place within 5 d after rainfall. Dry deposition to watershed land surfaces was substantial, representing a potentially large source of trace metals based on comparisons with load estimates from stormwater runoff.
Archives of Environmental Contamination and Toxicology, Aug 1, 1999
Stormwater runoff in a coastal urban area (San Diego County, CA) produced significant toxicity to... more Stormwater runoff in a coastal urban area (San Diego County, CA) produced significant toxicity to early life stages of medaka (Oryzias latipes) and Menidia (M. beryllina). Exposure of embryos to lower concentrations (5 to 25%) increased the incidence of abnormal swim bladder inflation and other teratogenic responses, whereas higher concentrations resulted in mortality or failure to hatch. Comparisons of EC50s for mortality and failure to hatch with concentrations of individual chemical pollutants (including Cd, Cr, Cu, Pb, Ni, and Zn) revealed low correlations; however, the correlation with total metals was high (Ϫ0.84) and corresponded with sample exceedences of Water Quality Criteria (WQC) for Cd, Cu, Pb, and Zn. This strong association between developmental toxicity and toxic metal content of storm water compared favorably with developmental anomalies reported in other studies. Analytical chemistry data for pesticides that may have been in these samples were limited to selected pesticides found usually below detection limits. Greater toxicity of the watershed effluents sampled was generally associated with more developed land surface and less open space. Both medaka and Menidia were found to be useful for studying effects of stormwater on embryonic and early larval development.
The contribution of atmospheric deposition to emissions of trace metals in stormwater runoff was ... more The contribution of atmospheric deposition to emissions of trace metals in stormwater runoff was investigated by quantifying wet and dry deposition fluxes and stormwater discharges within a small, highly impervious urban catchment in Los Angeles. At the beginning of the dry season in spring 2003, dry deposition measurements of chromium, copper, lead, nickel, and zinc were made monthly for one year. Stormwater runoff and wet deposition samples also were collected, and loading estimates of total annual deposition (wet + dry) were compared with annual stormwater loads. Wet deposition contributed 1% to 10% of the total deposition inside the catchment, indicating the dominance of dry deposition in semi-arid regions such as Los Angeles. Based on the ratio of total deposition to stormwater, atmospheric deposition potentially accounted for as much as 57% to 100% of the total trace metal loads in stormwater within the study area. Despite potential bias attributable to processes that were not quantified in this study (e.g., resuspension out of the catchment or sequestration within the catchment), these results demonstrate atmospheric deposition represents an important source of trace metals in stormwater to waterbodies near urban centers.
Although inputs of chlorinated hydrocarbon compounds to the Southern California Bight (SCB) are p... more Although inputs of chlorinated hydrocarbon compounds to the Southern California Bight (SCB) are presently low, historical deposits represent a source of bioaccumulation potential to sediment-associated fauna. To assess this bioaccumulation potential, 14 chlorinated hydrocarbon classes were measured in livers of three species of flatfish collected from 63 randomly selected sites on the coastal shelf between Point Conception and the United States-Mexico international border. Tissue contamination was widespread throughout the SCB, but was limited to just two chlorinated hydrocarbon classes. Virtually 100% of Pacific sanddab (Citharichthys sordidus) and longfin sanddab (Citharichthys xanthostigma) populations were estimated to be contaminated with dichlorodiphenyltrichloroethane (total DDT ϭ sum of o,pЈ and p,pЈ isomers of DDT ϩ dichlorodiphenyldichloroethylene [DDE] ϩ dichlorodiphenyldichloroethane [DDD]) and/or polychlorinated biphenyls (total PCBs). Total DDT also contaminated the majority (64%) of the Dover sole (Microstomus pacificus) population in the SCB. Total PCB measurements in tissues of SCB flatfish were dominated by 12 congeners (
Proceedings of the Water Environment Federation, 2005
Stormwater runoff is currently perceived as a major source of pollutants discharged to the coasta... more Stormwater runoff is currently perceived as a major source of pollutants discharged to the coastal oceans of southern California, but the quality and quantity of stormwater runoff is highly variable. In this study, nearly 2,000 samples were collected at 15-min intervals during the 1997/98 wet season from the Santa Ana River, an urbanized watershed in Orange County, California, to assess the magnitude of seasonal flushing and to assess pollutant variability within and among storm events. All samples were analyzed for total suspended solids (TSS); and a selected subset was analyzed for total organic carbon (TOC), total nitrogen (TN), and trace metals (cadmium, chromium, copper, lead, nickel, and zinc). Flow ranged up to five orders of magnitude and constituent concentrations routinely varied among storms by two orders of magnitude. Flow was the largest factor that accounted for changes in TSS concentrations. Significant seasonal flushing was observed. There were 220 non-rain days prior to the season's first event, and the first four storms had significantly higher concentrations of TSS and trace metals than the remaining storms of the season.
Journal of The American Water Resources Association, Dec 3, 2010
ABSTRACT Schiff, Kenneth C. and Liesl L. Tiefenthaler, 2011. Seasonal Flushing of Pollutant Conce... more ABSTRACT Schiff, Kenneth C. and Liesl L. Tiefenthaler, 2011. Seasonal Flushing of Pollutant Concentrations and Loads in Urban Stormwater. Journal of the American Water Resources Association (JAWRA) 47(1):136-142. DOI: 10.1111/j.1752-1688.2010.00497.xAbstract: Despite broad observations of first flush within storms, the scientific understanding of seasonal flushing remains incomplete. Seasonal flushing occurs when initial storms of the season have greater concentrations or loads than storms later in the season. The goal of this study was to census stormwater concentrations and loads from an arid, urban watershed to quantify seasonal flushing. Samples were collected every 15 min during the 1997-1998 wet season from the Santa Ana River and analyzed for total suspended solids. Initial storms of the season generated event mean concentrations 3-10 times the event mean concentration of storms later in the season. Cumulative flow-weighted mean concentrations were calculated as the season progressed. Early season storms discharged only 6% of the annual volume, but influenced flow-weighted mean concentrations well past the midpoint of the wet season. Mass-based estimates also indicated a disproportionate load in the early portion of the year; over 52% of the annual load was discharged in the first 30% of the annual volume from the highly urbanized lower watershed. Other stormwater pollutants, including six trace metals (Cd, Cr, Cu, Pb, Ni, Zn), were highly correlated with total suspended solids and also exhibited a significant seasonal flush.
Background:Coliphages have been proposed as indicators of fecal contamination in recreational wat... more Background:Coliphages have been proposed as indicators of fecal contamination in recreational waters because they better mimic the persistence of pathogenic viruses in the environment and wastewater treatment than fecal indicator bacteria. We estimated the association between coliphages and gastrointestinal illness and compared it with the association with culturable enterococci.Methods:We pooled data from six prospective cohort studies that enrolled coastal beachgoers in California, Alabama, and Rhode Island. Water samples were collected and gastrointestinal illness within 10 days of the beach visit was recorded. Samples were tested for enterococci and male-specific and somatic coliphages. We estimated cumulative incidence ratios (CIR) for the association between swimming in water with detectable coliphage and gastrointestinal illness when human fecal pollution was likely present, not likely present, and under all conditions combined. The reference group was unexposed swimmers. We defined continuous and threshold-based exposures (coliphage present/absent, enterococci >35 vs. ≤35 CFU/100 ml).Results:Under all conditions combined, there was no association between gastrointestinal illness and swimming in water with detectable coliphage or enterococci. When human fecal pollution was likely present, coliphage and enterococci were associated with increased gastrointestinal illness, and there was an association between male-specific coliphage level and illness that was somewhat stronger than the association between enterococci and illness. There were no substantial differences between male-specific and somatic coliphage.Conclusions:Somatic coliphage and enterococci had similar associations with gastrointestinal illness; there was some evidence that male-specific coliphage had a stronger association with illness than enterococci in marine waters with human fecal contamination.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
We modeled the risk of gastrointestinal (GI) illness associated with recreational exposures to ma... more We modeled the risk of gastrointestinal (GI) illness associated with recreational exposures to marine water following storm events in San Diego County, California. We estimated GI illness risks via quantitative microbial risk assessment (QMRA) techniques by consolidating site specific pathogen monitoring data of stormwater, site specific dilution estimates, literature-based water ingestion data, and literature based pathogen dose-response and morbidity information. Our water quality results indicated that human sources of contamination contribute viral and bacterial pathogens to streams draining an urban watershed during wet weather that then enter the ocean and affect nearshore water quality. We evaluated a series of approaches to account for uncertainty in the norovirus dose-response model selection and compared our model results to those from a concurrently conducted epidemiological study that provided empirical estimates for illness risk following ocean exposure. The preferred norovirus dose-response approach yielded median risk estimates for water recreation-associated illness (15 GI illnesses per 1000 recreation events) that closely matched the reported epidemiological results (12 excess GI illnesses per 1000 wet weather recreation events). The results are consistent with norovirus, or other pathogens associated with norovirus, as an important cause of gastrointestinal illness among surfers in this setting. This study demonstrates the applicability of QMRA for recreational water risk estimation, even under wet weather conditions and describes a process that might be useful in developing site-specific water quality criteria in this and other locations. Due to distribution restrictions, the full-text version of this article is available by request only.
We present an assessment of the deposition rates of airborne trace metals onto the Los Angeles Ba... more We present an assessment of the deposition rates of airborne trace metals onto the Los Angeles Basin and adjacent coastal waters. For this purpose, the UCLA Surface Meteorology and Ozone Generation (SMOG) air pollution modeling system has been used to simulate the geographical distributions of trace metals and their deposition fluxes. Calculations were performed for average summer and winter conditions, as well as for extreme meteorological events, in particular, for Santa Ana winds. Thus, a series of simulations were carried out that define the range of meteorological conditions contributing to dry deposition in the region. These predictions have been calibrated and validated using measurements collected in the LA area. Significant spatial and temporal variability are found in trace metal concentrations and deposition rates. Large spatial gradients occur near the coast as well as at the mountainous boundaries of the airshed. Considerable diurnal and seasonal variations in trace metal deposition are also noted. For example, the development of a daytime sea breeze, particularly in the warmer months, leads to greater deposition in the northern and eastern basin as well as in the high desert. A nighttime land breeze, especially in the colder months, enhances deposition onto coastal ocean surfaces. Large particles dominate local trace metal deposition in central urban (and adjacent) areas, while fine particles export metals over regional scales through long-range advection. Since the majority of urban metal deposition occurs on particles larger than 10-mm diameter, routine measurements of PM 10 or PM 2.5 concentrations for air quality characterization may not be reliable indicators of local sources. Some 35-45% of all trace metal emissions are deposited locally within the Los Angeles Basin on an annual basis. Santa Monica Bay and its watersheds receive about 6% of this amount, which can have a significant impact on trace metal concentrations in the surface waters of the bay, primarily through land runoff following storms.
Proceedings of the Water Environment Federation, 2011
In order to help protect the diverse natural resources in the State of California, water quality ... more In order to help protect the diverse natural resources in the State of California, water quality regulatory agencies are developing a new policy to set biological objectives (aka biocriteria). This manuscript is a description of the State's workplan. The policy development will include ten steps including: 1) Reference condition; 2) Stressor response models; 3) Waterbody classification; 4) Stressor identification; 5) Information management; 6) Implementation Plan Development; 7) Rulemaking; 8) Outreach; and 10) Training and standardization. The first five steps are largely technical while the remaining tasks are policy and administrative oriented. The new policy is expected to go before the state regulatory authority in 2013.
Bulletin, Southern California Academy of Sciences, Dec 1, 2007
US EPA. 1993a. Methods for measuring acute toxicity of effluents and receiving waters to freshwat... more US EPA. 1993a. Methods for measuring acute toxicity of effluents and receiving waters to freshwater and marine organisms, Fourth Edition. EPA 600/4-90/027. US Environmental Protection Agency,
Contamination in the coastal zone is closely linked to urbanization and has become a global issue... more Contamination in the coastal zone is closely linked to urbanization and has become a global issue. The coastal aquatic environment is the terminal sink for many chemicals; however, little is known about the occurrence and variation among habitats as well as integrative toxicity for pesticides, i.e., fipronil, and its three major degradates (-desulfinyl, -sulfide, and -sulfone, fiproles hereafter) in sediments in urban coastlines. In the present study, we report results of a random stratified survey for fiproles in surficial sediments in five embayment habitats (strata) along the Southern California Bight (SCB), USA coastline. Fiproles were present in a small areal extent (6.8%) of the SCB embayment, and detected in 14 out of 174 stations with a total concentration of the four analytes ranging from 0.50 to 17.5 μg/kg dry weight. The area-weighted mean concentrations were 3.16 ± 3.37, 0.584 ± 0.558, 0.071 ± 0.103, and 0.005 ± 0.009 μg/kg in brackish estuaries, estuaries, bays, and marinas, respectively, with the results below the detection limits in ports. Fipronil sulfone had the greatest detection frequency (8.05%) and highest mean concentration (3.24 ± 3.36 μg/kg) among the four compounds. A screening-level deterministic risk assessment for invertebrates found that, region-wide, fiproles generally posed an insignificant to low acute risk to the amphipod Eohaustorius estuarius in 7.36% of the SCB embayment area. In addition, high risk to the midge Chironomus dilutus was found in 77.5% of the fiproles-detectable area in the brackish estuary stratum that is a part of the Los Angeles River. Fipronil sulfone was identified as the major contributor of these effects. The results of this study establish a baseline of occurrence and toxicity potential for fiproles in coastal sediments of southern California.
After the United Nation's International Maritime Organization banned the use of organotins in ant... more After the United Nation's International Maritime Organization banned the use of organotins in antifouling products, organic booster biocides were introduced as alternatives to these compounds. The purpose of this study was to measure concentrations of the antifouling agent Irgarol 1051, its major metabolite M1 (aka GS26575), and other antifouling pesticides (diuron, chlorothalonil, dichlofluanid and TCMTB) in San Diego, California, USA region marinas and evaluate the environmental risk posed by these compounds. To our knowledge, this is first study reporting Irgarol concentrations in western areas of the US. Water samples were collected from marina sites in four harbors surrounding greater San Diego,
Emissions of trace metals to the atmosphere and subsequent deposition, either directly to a water... more Emissions of trace metals to the atmosphere and subsequent deposition, either directly to a waterbody surface or indirectly to the watershed as washoff during rainfall, represents a potential source of contamination to surface waters near urban centers. The present study provides measurements of atmospheric concentrations of particle-bound trace metals, and it estimates the dry deposition mass loading of trace metals in coastal watersheds in the Los Angeles, California, USA, air basin. Coarse-particle atmospheric concentrations of metals were measured seasonally using a Noll Rotary Impactor at six urban sites and one nonurban site. Dry deposition fluxes were calculated by summing the product of air concentration and the theoretical deposition velocity for each particle size fraction. Mean fluxes at urban sites ranged from 3.2 to 9.1, 11 to 34, 3.8 to 8.8, 8.3 to 29, and 69 to 228 g/ m 2 /d for chromium, copper, nickel, lead, and zinc, respectively. Mean concentrations and fluxes were significantly higher at urban sites compared with the nonurban site, although differences between urban and nonurban sites were reduced when sampling took place within 5 d after rainfall. Dry deposition to watershed land surfaces was substantial, representing a potentially large source of trace metals based on comparisons with load estimates from stormwater runoff.
Archives of Environmental Contamination and Toxicology, Aug 1, 1999
Stormwater runoff in a coastal urban area (San Diego County, CA) produced significant toxicity to... more Stormwater runoff in a coastal urban area (San Diego County, CA) produced significant toxicity to early life stages of medaka (Oryzias latipes) and Menidia (M. beryllina). Exposure of embryos to lower concentrations (5 to 25%) increased the incidence of abnormal swim bladder inflation and other teratogenic responses, whereas higher concentrations resulted in mortality or failure to hatch. Comparisons of EC50s for mortality and failure to hatch with concentrations of individual chemical pollutants (including Cd, Cr, Cu, Pb, Ni, and Zn) revealed low correlations; however, the correlation with total metals was high (Ϫ0.84) and corresponded with sample exceedences of Water Quality Criteria (WQC) for Cd, Cu, Pb, and Zn. This strong association between developmental toxicity and toxic metal content of storm water compared favorably with developmental anomalies reported in other studies. Analytical chemistry data for pesticides that may have been in these samples were limited to selected pesticides found usually below detection limits. Greater toxicity of the watershed effluents sampled was generally associated with more developed land surface and less open space. Both medaka and Menidia were found to be useful for studying effects of stormwater on embryonic and early larval development.
The contribution of atmospheric deposition to emissions of trace metals in stormwater runoff was ... more The contribution of atmospheric deposition to emissions of trace metals in stormwater runoff was investigated by quantifying wet and dry deposition fluxes and stormwater discharges within a small, highly impervious urban catchment in Los Angeles. At the beginning of the dry season in spring 2003, dry deposition measurements of chromium, copper, lead, nickel, and zinc were made monthly for one year. Stormwater runoff and wet deposition samples also were collected, and loading estimates of total annual deposition (wet + dry) were compared with annual stormwater loads. Wet deposition contributed 1% to 10% of the total deposition inside the catchment, indicating the dominance of dry deposition in semi-arid regions such as Los Angeles. Based on the ratio of total deposition to stormwater, atmospheric deposition potentially accounted for as much as 57% to 100% of the total trace metal loads in stormwater within the study area. Despite potential bias attributable to processes that were not quantified in this study (e.g., resuspension out of the catchment or sequestration within the catchment), these results demonstrate atmospheric deposition represents an important source of trace metals in stormwater to waterbodies near urban centers.
Although inputs of chlorinated hydrocarbon compounds to the Southern California Bight (SCB) are p... more Although inputs of chlorinated hydrocarbon compounds to the Southern California Bight (SCB) are presently low, historical deposits represent a source of bioaccumulation potential to sediment-associated fauna. To assess this bioaccumulation potential, 14 chlorinated hydrocarbon classes were measured in livers of three species of flatfish collected from 63 randomly selected sites on the coastal shelf between Point Conception and the United States-Mexico international border. Tissue contamination was widespread throughout the SCB, but was limited to just two chlorinated hydrocarbon classes. Virtually 100% of Pacific sanddab (Citharichthys sordidus) and longfin sanddab (Citharichthys xanthostigma) populations were estimated to be contaminated with dichlorodiphenyltrichloroethane (total DDT ϭ sum of o,pЈ and p,pЈ isomers of DDT ϩ dichlorodiphenyldichloroethylene [DDE] ϩ dichlorodiphenyldichloroethane [DDD]) and/or polychlorinated biphenyls (total PCBs). Total DDT also contaminated the majority (64%) of the Dover sole (Microstomus pacificus) population in the SCB. Total PCB measurements in tissues of SCB flatfish were dominated by 12 congeners (
Proceedings of the Water Environment Federation, 2005
Stormwater runoff is currently perceived as a major source of pollutants discharged to the coasta... more Stormwater runoff is currently perceived as a major source of pollutants discharged to the coastal oceans of southern California, but the quality and quantity of stormwater runoff is highly variable. In this study, nearly 2,000 samples were collected at 15-min intervals during the 1997/98 wet season from the Santa Ana River, an urbanized watershed in Orange County, California, to assess the magnitude of seasonal flushing and to assess pollutant variability within and among storm events. All samples were analyzed for total suspended solids (TSS); and a selected subset was analyzed for total organic carbon (TOC), total nitrogen (TN), and trace metals (cadmium, chromium, copper, lead, nickel, and zinc). Flow ranged up to five orders of magnitude and constituent concentrations routinely varied among storms by two orders of magnitude. Flow was the largest factor that accounted for changes in TSS concentrations. Significant seasonal flushing was observed. There were 220 non-rain days prior to the season's first event, and the first four storms had significantly higher concentrations of TSS and trace metals than the remaining storms of the season.
Journal of The American Water Resources Association, Dec 3, 2010
ABSTRACT Schiff, Kenneth C. and Liesl L. Tiefenthaler, 2011. Seasonal Flushing of Pollutant Conce... more ABSTRACT Schiff, Kenneth C. and Liesl L. Tiefenthaler, 2011. Seasonal Flushing of Pollutant Concentrations and Loads in Urban Stormwater. Journal of the American Water Resources Association (JAWRA) 47(1):136-142. DOI: 10.1111/j.1752-1688.2010.00497.xAbstract: Despite broad observations of first flush within storms, the scientific understanding of seasonal flushing remains incomplete. Seasonal flushing occurs when initial storms of the season have greater concentrations or loads than storms later in the season. The goal of this study was to census stormwater concentrations and loads from an arid, urban watershed to quantify seasonal flushing. Samples were collected every 15 min during the 1997-1998 wet season from the Santa Ana River and analyzed for total suspended solids. Initial storms of the season generated event mean concentrations 3-10 times the event mean concentration of storms later in the season. Cumulative flow-weighted mean concentrations were calculated as the season progressed. Early season storms discharged only 6% of the annual volume, but influenced flow-weighted mean concentrations well past the midpoint of the wet season. Mass-based estimates also indicated a disproportionate load in the early portion of the year; over 52% of the annual load was discharged in the first 30% of the annual volume from the highly urbanized lower watershed. Other stormwater pollutants, including six trace metals (Cd, Cr, Cu, Pb, Ni, Zn), were highly correlated with total suspended solids and also exhibited a significant seasonal flush.
Background:Coliphages have been proposed as indicators of fecal contamination in recreational wat... more Background:Coliphages have been proposed as indicators of fecal contamination in recreational waters because they better mimic the persistence of pathogenic viruses in the environment and wastewater treatment than fecal indicator bacteria. We estimated the association between coliphages and gastrointestinal illness and compared it with the association with culturable enterococci.Methods:We pooled data from six prospective cohort studies that enrolled coastal beachgoers in California, Alabama, and Rhode Island. Water samples were collected and gastrointestinal illness within 10 days of the beach visit was recorded. Samples were tested for enterococci and male-specific and somatic coliphages. We estimated cumulative incidence ratios (CIR) for the association between swimming in water with detectable coliphage and gastrointestinal illness when human fecal pollution was likely present, not likely present, and under all conditions combined. The reference group was unexposed swimmers. We defined continuous and threshold-based exposures (coliphage present/absent, enterococci >35 vs. ≤35 CFU/100 ml).Results:Under all conditions combined, there was no association between gastrointestinal illness and swimming in water with detectable coliphage or enterococci. When human fecal pollution was likely present, coliphage and enterococci were associated with increased gastrointestinal illness, and there was an association between male-specific coliphage level and illness that was somewhat stronger than the association between enterococci and illness. There were no substantial differences between male-specific and somatic coliphage.Conclusions:Somatic coliphage and enterococci had similar associations with gastrointestinal illness; there was some evidence that male-specific coliphage had a stronger association with illness than enterococci in marine waters with human fecal contamination.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
We modeled the risk of gastrointestinal (GI) illness associated with recreational exposures to ma... more We modeled the risk of gastrointestinal (GI) illness associated with recreational exposures to marine water following storm events in San Diego County, California. We estimated GI illness risks via quantitative microbial risk assessment (QMRA) techniques by consolidating site specific pathogen monitoring data of stormwater, site specific dilution estimates, literature-based water ingestion data, and literature based pathogen dose-response and morbidity information. Our water quality results indicated that human sources of contamination contribute viral and bacterial pathogens to streams draining an urban watershed during wet weather that then enter the ocean and affect nearshore water quality. We evaluated a series of approaches to account for uncertainty in the norovirus dose-response model selection and compared our model results to those from a concurrently conducted epidemiological study that provided empirical estimates for illness risk following ocean exposure. The preferred norovirus dose-response approach yielded median risk estimates for water recreation-associated illness (15 GI illnesses per 1000 recreation events) that closely matched the reported epidemiological results (12 excess GI illnesses per 1000 wet weather recreation events). The results are consistent with norovirus, or other pathogens associated with norovirus, as an important cause of gastrointestinal illness among surfers in this setting. This study demonstrates the applicability of QMRA for recreational water risk estimation, even under wet weather conditions and describes a process that might be useful in developing site-specific water quality criteria in this and other locations. Due to distribution restrictions, the full-text version of this article is available by request only.
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