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Austin K. Baldwin

Publications and source records attributed to Austin K. Baldwin.

At least 37 records · Page 2Linked to original sources
USGS2021

Identifying chemicals and mixtures of potential biological concern detected in passive samplers from Great Lakes tributaries using high-throughput data and biological pathways

Waterborne contaminants were monitored in 69 tributaries of the Laurentian Great Lakes in 2010 and 2014 using semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCIS). A risk-based screening approach was used to prioritize chemicals and chemical mixtures, identify sites at greatest risk for biological impacts, and identify potential hazards to monitor at those sites. Analyses included 185 chemicals (143 detected) including polycyclic aromatic hydrocarbons (PAHs), legacy and current-use pesticides, fire retardants, pharmaceuticals, and fragrances. Hazard quotients were calculated by dividing detected concentrations by biological effect concentrations reported in the ECOTOX Knowledgebase (toxicity quotients) or ToxCast database (exposure–activity ratios [EARs]). Mixture effects were estimated by summation of EAR values for chemicals that influence ToxCast assays with common gene targets. Nineteen chemicals—atrazine, N,N -diethyltoluamide, di(2-ethylhexyl)phthalate, dl-menthol, galaxolide, p-tert-octylphenol, 3 organochlorine pesticides, 3 PAHs, 4 pharmaceuticals, and 3 phosphate flame retardants—had toxicity quotients >0.1 or EARs for individual chemicals >10 –3 at 10% or more of the sites monitored. An additional 4 chemicals (tributyl phosphate, triethyl citrate, benz[ a ]anthracene, and benzo[ b ]fluoranthene) were present in mixtures with EARs >10 –3 . To evaluate potential apical effects and biological endpoints to monitor in exposed wildlife, in vitro bioactivity data were compared to adverse outcome pathway gene ontology information. Endpoints and effects associated with endocrine disruption, alterations in xenobiotic metabolism, and potentially neuronal development would be relevant to monitor at the priority sites. The EAR threshold exceedance for many chemical classes was correlated with urban land cover and wastewater effluent influence, whereas herbicides and fire retardants were also correlated to agricultural land cover. Environ Toxicol Chem 2021;40:2165–2182. Published 2021. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Great Lakes↗
USGS2021

Microplastics in the Delaware River, northeastern United States

Microplastics are a contaminant of increasing concern in aquatic environments. Our understanding of microplastics in freshwater environments has increased dramatically over the past decade, but we still lack information on microplastic occurrence and biological uptake in National Park Service (NPS) waters. During 2015–19, the U.S. Geological Survey and the NPS conducted a three-phase study of microplastic occurrence and biological uptake in NPS waters. This fact sheet summarizes results from Phase 3 in which microplastics were sampled at nine locations spanning various land uses on the Upper Delaware, Middle Delaware, and Lower Delaware Scenic and Recreational River and its tributaries in the northeastern United States. Water and sediment samples were collected during baseflow conditions at each location to assess microplastic occurrence, and fish and mussels were collected at a subset of locations to assess potential biological uptake of microplastics.

Delaware, New Jersey, New York, Pennsylvania↗
USGS2021

Effect of organic matter concentration and characteristics on mercury mobilization and methylmercury production at an abandoned mine site

Thousands of abandoned mines throughout the western region of North America contain elevated total-mercury (THg) concentrations. Mercury is mobilized from these sites primarily due to erosion of particulate-bound Hg (THg-P). Organic matter-based soil amendments can promote vegetation growth on mine tailings, reducing erosion and subsequent loading of THg-P into downstream waterbodies. However, the introduction of a labile carbon source may stimulate microbial activity that can produce methylmercury (MeHg)—the more toxic and bioaccumulative form of Hg. Our objectives were to investigate how additions of different organic matter substrates impact Hg mobilization and methylation using a combination of field observations and controlled experiments. Field measurements of water, sediment, and porewater were collected downstream of the site and multi-year monitoring (and load calculations) were conducted at a downstream gaging station. MeHg production was assessed using stable isotope methylation assays and mesocosm experiments that were conducted using different types of organic carbon soil amendments mixed with materials from the mine site. The results showed that >80% of the THg mobilized from the mine was bound to particles and that >90% of the annual Hg loading occurred during the period of elevated discharge during spring snowmelt. Methylation rates varied between different types of soil amendments and were correlated with the components of excitation emission matrices (EEMs) associated with humic acid fractions of organic matter. The mesocosm experiments showed that under anoxic conditions carbon amendments to tailings could significantly increase porewater MeHg concentrations (up to 13 ± 3 ng/L). In addition, the carbon amendments significantly increased THg partitioning into porewater. Overall, these results indicate that soil amendment applications to reduce surface erosion at abandoned mine sites could be effective at reducing particulate Hg mobilization to downstream waterbodies; however, some types of carbon amendments can significantly increase Hg methylation as well as increase the mobilization of dissolved THg from the site.

Idaho↗
USGS2020

Seasonal dynamics and interannual variability in mercury concentrations and loads through a three-reservoir complex

The Hells Canyon Complex (HCC) along the Snake River (Idaho-Oregon border, USA) encompasses three successive reservoirs that seasonally stratify, creating anoxic conditions in the hypolimnion that promote methylmercury (MeHg) production. This study quantified seasonal dynamics and interannual variability in mercury concentrations (inorganic divalent mercury (IHg) and MeHg) and loads at four reservoir inflow and outflow locations through the HCC (2014-2017). We observed (1) that the HCC is a net sink for both IHg and MeHg, (2) interannual variability in IHg and MeHg loads largely reflecting streamflow conditions, and (3) seasonal variability in particulate IHg loading at the inflow (greatest from February to April) and MeHg export from the outflow (greatest from September to December) of the HCC. Seasonal export of MeHg was evidenced by increases in monthly mean concentrations of unfiltered MeHg (approximately twofold) and the percentage of total mercury (THg) as MeHg (≥ fourfold) coincident with reservoir destratification. Despite evidence of seasonal export of MeHg from the HCC, annual loads indicate a 42% decrease in unfiltered MeHg from HCC inflow to outflow. Results from this study improve the understanding of seasonal variability in mercury transport through and transformation within a reservoir complex.

Idaho, Oregon↗
USGS2020

Primary sources of polycyclic aromatic hydrocarbons to streambed sediment in Great Lakes tributaries using multiple lines of evidence

Polycyclic aromatic hydrocarbons (PAHs) are among the most widespread and potentially toxic contaminants in Great Lakes (USA/Canada) tributaries. The sources of PAHs are numerous and diverse, and identifying the primary source(s) can be difficult. The present study used multiple lines of evidence to determine the likely sources of PAHs to surficial streambed sediments at 71 locations across 26 Great Lakes Basin watersheds. Profile correlations, principal component analysis, positive matrix factorization source‐receptor modeling, and mass fractions analysis were used to identify potential PAH sources, and land‐use analysis was used to relate streambed sediment PAH concentrations to different land uses. Based on the common conclusion of these analyses, coal‐tar–sealed pavement was the most likely source of PAHs to the majority of the locations sampled. The potential PAH‐related toxicity of streambed sediments to aquatic organisms was assessed by comparison of concentrations with sediment quality guidelines. The sum concentration of 16 US Environmental Protection Agency priority pollutant PAHs was 7.4–196 000 µg/kg, and the median was 2600 µg/kg. The threshold effect concentration was exceeded at 62% of sampling locations, and the probable effect concentration or the equilibrium partitioning sediment benchmark was exceeded at 41% of sampling locations. These results have important implications for watershed managers tasked with protecting and remediating aquatic habitats in the Great Lakes Basin.

Indiana, Michigan, Minnesota, New York, Ohio, Wisc↗
USGS2020

Microplastics in Lake Mead National Recreation Area, USA: Occurrence and biological uptake

Microplastics are an environmental contaminant of growing concern, but there is a lack of information about microplastic distribution, persistence, availability, and biological uptake in freshwater systems. This is especially true for large river systems like the Colorado River that spans multiple states through mostly rural and agricultural land use. This study characterized the quantity and morphology of microplastics in different environmental compartments in two large reservoirs along the Colorado River: Lakes Mead and Mohave, within Lake Mead National Recreation Area. To assess microplastic occurrence, surface water and surficial sediment were sampled at a total of nine locations. Sampling locations targeted different sub-basins with varying levels of anthropogenic impact. Las Vegas Wash, a tributary which delivers treated wastewater to Lake Mead, was also sampled. A sediment core (33 cm long, representing approximately 19 years) was extracted from Las Vegas Bay to assess changes in microplastic deposition over time. Striped bass (Morone saxatilis), common carp (Cyprinus carpio), quagga mussels (Dreissena bugensis), and Asian clams (Corbicula fluminea) were sampled at a subset of locations to assess biological uptake of microplastics. Microplastic concentrations were 0.44-9.7 particles/cubic meter at the water surface and 87.5-1,010 particles/kilogram dry weight (kg dw) at the sediment surface. Sediment core concentrations were 220-2,040 particles/kg dw, with no clear increasing or decreasing trend over time. Shellfish microplastic concentrations ranged from 2.7-105 particles/organism, and fish concentrations ranged from 0-19 particles/organism. Fibers were the most abundant particle type found in all sample types. Although sample numbers are small, microplastic concentrations appear to be higher in areas of greater anthropogenic impact. Results from this study improve our understanding of the occurrence and biological uptake of microplastics in Lake Mead National Recreation Area, and help fill existing knowledge gaps on microplastics in freshwater environments in the southwestern U.S.

Nevada↗
USGS2019

Vertical distribution of microplastics in the water column and surficial sediment from the Milwaukee River basin to Lake Michigan

Microplastic contamination was studied along a freshwater continuum from inland streams to the Milwaukee River estuary to Lake Michigan, and vertically from the water surface, water subsurface and sediment. Microplastics were detected in all 96 water samples and nine sediment samples collected. Results indicated a gradient of polymer presence with depth: low-density particles decreased from water surface to subsurface to sediment, and high-density particles had the opposite result. Polymer identification results indicated water surface and subsurface samples were dominated by low-density polypropylene particles and sediment samples were dominated by more dense polyethylene terephthalate particles. Of the five particle-type categories (fragments, films, foams, pellets/beads and fibers/lines), fibers/lines were the most common particle type and were present in every water and sediment sample collected. Fibers represented 45% of all particles in water samples and were distributed vertically throughout the water column regardless of density. Sediment samples were dominated by black foams (66%, identified as styrene-butadiene rubber, SBR) and to a lesser extent fibers/lines (29%) with approximately 89% of all the sediment particles coming from polymers with densities greater than 1.1 g cm-3. Results demonstrated polymer density influenced partitioning between water surface and subsurface and the underlying surficial sediment and the common practice of sampling only the water surface can result in substantial bias, especially in estuarine, harbor and lake locations where water surface concentrations tend to overestimate mean water column concentrations.

Wisconsin↗
USGS2019

Arsenic, antimony, mercury, and water temperature in streams near Stibnite mining area, central Idaho, 2011–17

Mineralization and historical mining of stibnite (antimony sulfide), tungsten, gold, silver, and mercury in the headwaters of the East Fork of the South Fork Salmon River (EFSFSR) near the former town of Stibnite in central Idaho resulted in water-quality impairments related to mercury, antimony, and arsenic. Additionally, mining-related disturbances and wildfires have resulted in a lack of riparian shade in some areas, likely impacting water temperatures. In 2011, the U.S. Geological Survey, in cooperation with Midas Gold Corporation and the Idaho Department of Lands, began a study to characterize the spatial and temporal occurrence of trace metals to the EFSFSR. Five sites on the EFSFSR and its tributaries (Meadow and Sugar Creeks) were sampled about six times annually during 2011–17, during a range of streamflow conditions, for a total of 36–40 samples per location. Continuous water temperature, specific conductance, and streamflow also were measured at each site. The purpose of this report is to update previously reported information related to arsenic, antimony, mercury, and water temperature. Concentrations of dissolved arsenic and antimony generally increased from upstream to downstream in the EFSFSR. At the upstream site, upstream of the Meadow Creek confluence, dissolved arsenic and antimony concentrations averaged 8.86 and 0.93 micrograms per liter (μg/L), respectively. Downstream, upstream from the Sugar Creek confluence, average dissolved concentrations increased to 56.5 and 27.9 μg/L, respectively. All samples from the downstream EFSFSR site exceeded the human-health based criterion for both dissolved arsenic (10 µg/L) and dissolved antimony (5.6 µg/L). The chronic aquatic life criterion for dissolved arsenic (150 μg/L) was not exceeded (the maximum sample concentration was 108 μg/L), and aquatic life criteria for antimony have not been established. The highest concentrations of both dissolved arsenic and dissolved antimony occurred during low-flow periods (July–March), suggesting the constituents are present in groundwater. In contrast, total mercury concentrations were highest during high-flow periods (April–June) and were particulate-associated, suggesting that mercury is present in surface materials. At Sugar Creek, where the highest total mercury concentrations were measured, 97 percent of samples exceeded the chronic aquatic life criterion (0.012 μg/L) and 11 percent exceeded the acute criterion (2.1 μg/L). At all sites, summertime water temperatures frequently exceeded criteria related to salmonid spawning. Surrogate models previously developed to estimate continuous concentrations of arsenic, antimony, and mercury were reevaluated and updated, and the importance of explanatory variables on constituent concentrations is discussed. Results from this study can help guide future remediation locations and strategies, and provide a baseline against which future changes can be measured.

Idaho↗
USGS2019

It is raining plastic

Atmospheric deposition samples were collected using the National Atmospheric Deposition Program / National Trends Network (NADP/NTN) at 6 sites in the Denver-Boulder urban corridor and 2 adjacent sites in the Colorado Front Range. Weekly wet-only atmospheric deposition samples collected at these sites during winter-summer of 2017 were filtered (0.45 micrometers, polyethersulfone) to obtain particulates washed from the atmosphere (washout). Plastics were identified on over 90 percent of the filters. The plastic materials are mostly fibers that are only visible with magnification (~40X). Fibers were present in a variety of colors; the most frequently observed color was blue followed by red > silver > purple > green > yellow > other colors. Plastic particles such as beads and shards were also observed with magnification. More plastic fibers were observed in samples from urban sites than from isolated, montane sites. However, frequent observation of plastic fibers in washout samples from the isolated Loch Vale site in Rocky Mountain National Park (elevation 3,159 meters) suggests that wet-deposition of plastic is ubiquitous and not just an urban condition. The mass of plastic in even the most concentrated samples was not large enough to weigh or reliably estimate. Developing a routine capability to calculate plastic wet-deposition loads is not possible with current technology. Counting plastic fibers under a microscope and multiplying the counts by a mean mass per fiber might be possible, but it is tedious, expensive, and has large inherent error. A means to estimate the recovery of the plastic materials from the NADP samples is needed. However, saving the NADP filters for subsequent analysis would make a washout deposition network possible with very little added expense, and methods could be developed to more accurately estimate plastic loads using the NTN. It is unclear how these plastic materials are accumulating and being assimilated in the environment and biota. Moreover, the potential effects of these materials on biota is not understood.

Colorado↗
USGS2019

Prioritizing chemicals of ecological concern in Great Lakes tributaries using high-throughput screening data and adverse outcome pathways

Chemical monitoring data were collected in surface waters from 57 Great Lakes tributaries from 2010-13 to identify chemicals of potential biological relevance and sites at which these chemicals occur. Traditional water-quality benchmarks for aquatic life based on in vivo toxicity data were available for 34 of 67 evaluated chemicals. To expand evaluation of potential biological effects, measured chemical concentrations were compared to chemical-specific biological activities determined in high-throughput (ToxCast) in vitro assays. Resulting exposure-activity ratios (EARs) were used to prioritize the chemicals of greatest potential concern: 4-nonylphenol, bisphenol A, metolachlor, atrazine, DEET, caffeine, tris(2-butoxyethyl) phosphate, tributyl phosphate, triphenyl phosphate, benzo(a)pyrene, fluoranthene, and benzophenone. Water-quality benchmarks were unavailable for five of these chemicals, but for the remaining seven, EAR-based prioritization was consistent with that based on toxicity quotients calculated from benchmarks. Water-quality benchmarks identified three additional PAHs (anthracene, phenanthrene, and pyrene) not prioritized using EARs. Through this analysis, an EAR of 10-3 was identified as a reasonable threshold above which a chemical might be of potential concern. To better understand apical hazards potentially associated with biological activities captured in ToxCast assays, in vitro bioactivity data were matched with available adverse outcome pathway (AOP) information. The 49 ToxCast assays prioritized via EAR analysis aligned with 23 potentially-relevant AOPs present in the AOP-Wiki. Mixture effects at monitored sites were estimated by summation of EAR values for multiple chemicals by individual assay or individual AOP. Commonly predicted adverse outcomes included impacts on reproduction and mitochondrial function. The EAR approach provided a screening-level assessment for evidence-based prioritization of chemicals and sites with potential for adverse biological effects. The approach aids prioritization of future monitoring activities and provides testable hypotheses to help focus those efforts. This also expands the fraction of detected chemicals for which biologically-based benchmark concentrations are available to help contextualize chemical monitoring results.

Science of the Total Environment↗
USGS2018

Human-associated indicator bacteria and human-specific viruses in surface water: a spatial assessment with implications on fate and transport

Hydrologic, seasonal, and spatial variability of sewage contamination was studied at six locations within a watershed upstream from water reclamation facility (WRF) effluent to define relative loadings of sewage from different portions of the watershed. Fecal pollution from human sources was spatially quantified by measuring two human-associated indicator bacteria (HIB) and eight human-specific viruses (HSV) at six stream locations in the Menomonee River watershed in Milwaukee, Wisconsin from April 2009 to March 2011. A custom, automated water sampler, which included HSV filtration, was deployed at each location providing unattended, flow-weighted, large-volume (30-913 L) sampling. In addition, wastewater influent samples were composited over discrete seven-day periods from the two Milwaukee WRFs. Of the eight HSV only three were detected, present in up to 38% of the 228 stream samples, while at least one HSV was detected in all WRF influent samples. HIB occurred more often with significantly higher concentrations than the HSV in stream and WRF influent samples (p<0.05). HSV yield calculations showed a loss from upstream to the most downstream sub-watershed of the Menomonee River, and in contrast, a positive HIB yield from this same sub-watershed emphasizes the complexity in fate and transport properties between HSV and HIB. This study demonstrates the utility of analyzing multiple HSV and HIB to provide a weight of evidence approach for assessment of fecal contamination at the watershed level, provides an assessment of relative loadings for prioritizing areas within a watershed, and demonstrates how loadings of HSV and HIB can be inconsistent, inferring potential differences in fate and transport between the two indicators of human fecal presence.

Wisconsin↗
USGS2018

Patterns of host-associated fecal indicators driven by hydrology, precipitation, and land use attributes in Great Lakes watersheds

Fecal contamination from sewage and agricultural runoff is a pervasive problem in Great Lakes watersheds. Most work examining fecal pollution loads relies on discrete samples of fecal indicators and modeling land use. In this study, we made empirical measurements of human and ruminant-associated fecal indicator bacteria and combined these with hydrological measurements in eight watersheds ranging from predominantly forested to highly urbanized. Flow composited river samples were collected over low-flow ( n = 89) and rainfall or snowmelt runoff events ( n = 130). Approximately 90% of samples had evidence of human fecal pollution, with highest loads from urban watersheds. Ruminant indicators were found in ∼60–100% of runoff-event samples in agricultural watersheds, with concentrations and loads related to cattle density. Rain depth, season, agricultural tile drainage, and human or cattle density explained variability in daily flux of human or ruminant indicators. Mapping host-associated indicator loads to watershed discharge points sheds light on the type, level, and possible health risk from fecal pollution entering the Great Lakes and can inform total maximum daily load implementation and other management practices to target specific fecal pollution sources.

Environmental Science & Technology↗
USGS2018

Year-round presence of neonicotinoid insecticides in tributaries to the Great Lakes, USA

To better characterize the transport of neonicotinoid insecticides to the world's largest freshwater ecosystem, monthly samples (October 2015–September 2016) were collected from 10 major tributaries to the Great Lakes, USA. For the monthly tributary samples, neonicotinoids were detected in every month sampled and five of the six target neonicotinoids were detected. At least one neonicotinoid was detected in 74% of the monthly samples with up to three neonicotinoids detected in an individual sample (10% of all samples). The most frequently detected neonicotinoid was imidacloprid (53%), followed by clothianidin (44%), thiamethoxam (22%), acetamiprid (2%), and dinotefuran (1%). Thiacloprid was not detected in any samples. The maximum concentration for an individual neonicotinoid was 230 ng L −1 and the maximum total neonicotinoids in an individual sample was 400 ng L −1 . The median detected individual neonicotinoid concentrations ranged from non-detect to 10 ng L −1 . The detections of clothianidin and thiamethoxam significantly increased as the percent of cultivated crops in the basins increased (ρ = 0.73, P = .01; ρ = 0.66, P = .04, respectively). In contrast, imidacloprid detections significantly increased as the percent of the urbanization in the basins increased (ρ = 0.66, P = .03). Neonicotinoid concentrations generally increased in spring through summer coinciding with the planting of neonicotinoid-treated seeds and broadcast applications of neonicotinoids. More spatially intensive samples were collected in an agriculturally dominated basin (8 sites along the Maumee River, Ohio) twice during the spring, 2016 planting season to provide further information on neonicotinoid inputs to the Great Lakes. Three neonicotinoids were ubiquitously detected (clothianidin, imidacloprid, thiamethoxam) in all water samples collected within this basin. Maximum individual neonicotinoid concentrations was 330 ng L −1 and maximum total neonicotinoid concentration was 670 ng L −1 ; median detected individual neonicotinoid concentrations were 7.0 to 39 ng L −1 .

Great Lakes↗
USGS2017

Hydrologic, land cover, and seasonal patterns of waterborne pathogens in Great Lakes tributaries

Great Lakes tributaries are known to deliver waterborne pathogens from a host of sources. To examine the hydrologic, land cover, and seasonal patterns of waterborne pathogens (i.e. protozoa (2), pathogenic bacteria (4) human viruses, (8) and bovine viruses (8)) eight rivers were monitored in the Great Lakes Basin over 29 months from February 2011 to June 2013. Sampling locations represented a wide variety of land cover classes from urban to agriculture to forest. A custom automated pathogen sampler was deployed at eight sampling locations which provided unattended, flow-weighted, large-volume (120–1630 L) sampling. Human and bovine viruses and pathogenic bacteria were detected by real-time qPCR in 16%, 14%, and 1.4% of 290 samples collected while protozoa were never detected. The most frequently detected pathogens were: bovine polyomavirus (11%), and human adenovirus C, D, F (9%). Human and bovine viruses were present in 16.9% and 14.8% of runoff-event samples (n = 189) resulting from precipitation and snowmelt, and 13.9% and 12.9% of low-flow samples (n = 101), respectively, indicating multiple delivery mechanisms could be influential. Data indicated human and bovine virus prevalence was different depending on land cover within the watershed. Occurrence, concentration, and flux of human viruses were greatest in samples from the three sampling locations with greater than 25% urban influence than those with less than 25% urban influence. Similarly, occurrence, concentration, and flux of bovine viruses were greatest in samples from the two sampling locations with greater than 50 cattle/km 2 than those with less than 50 cattle/km 2 . In seasonal analysis, human and bovine viruses occurred more frequently in spring and winter seasons than during the fall and summer. Concentration, occurrence, and flux in the context of hydrologic condition, seasonality, and land use must be considered for each watershed individually to develop effective watershed management strategies for pathogen reduction.

Great Lakes tributaries↗
USGS2016

Primary sources and toxicity of PAHs in Milwaukee-area streambed sediment

High concentrations of polycyclic aromatic hydrocarbons (PAHs) in streams can be a significant stressor to aquatic organisms. To understand the likely sources and toxicity of PAHs in Milwaukee-area streams, streambed sediment samples from 40 sites and parking lot dust samples from 6 sites were analyzed for 38 parent PAHs and 25 alkylated PAHs. Diagnostic ratios, profile correlations, principal components analysis, source-receptor modeling, and mass fractions analysis were used to identify potential PAH sources to streambed sediment samples, and land-use analysis was used to relate streambed sediment PAH concentrations to different urban-related land uses. On the basis of this multiple lines-of-evidence approach, coal-tar pavement sealant was indicated as the primary source of PAHs in a majority of streambed sediment samples, contributing an estimated 77% of total PAHs to samples, on average. Comparison to the Probable Effect Concentrations and (or) the Equilibrium Partitioning Sediment Benchmark indicates that 78% of stream sediment samples are likely to cause adverse effects to benthic organisms. Laboratory toxicity tests on a 16-sample subset of the streambed sites using the amphipod Hyalella azteca (28-day) and the midge Chironomus dilutus (10-day) measured significant reductions in one or more biological endpoints, including survival, in 75% of samples, with H. azteca more responsive than C. dilutus .

Wisconsin↗
USGS2016

Plastic debris in 29 Great Lakes tributaries: Relations to watershed attributes and hydrology

Plastic debris is a growing contaminant of concern in freshwater environments, yet sources, transport, and fate remain unclear. This study characterized the quantity and morphology of floating micro- and macroplastics in 29 Great Lakes tributaries in six states under different land covers, wastewater effluent contributions, population densities, and hydrologic conditions. Tributaries were sampled three or four times each using a 333 μm mesh neuston net. Plastic particles were sorted by size, counted, and categorized as fibers/lines, pellets/beads, foams, films, and fragments. Plastics were found in all 107 samples, with a maximum concentration of 32 particles/m 3 and a median of 1.9 particles/m 3 . Ninety-eight percent of sampled plastic particles were less than 4.75 mm in diameter and therefore considered microplastics. Fragments, films, foams, and pellets/beads were positively correlated with urban-related watershed attributes and were found at greater concentrations during runoff-event conditions. Fibers, the most frequently detected particle type, were not associated with urban-related watershed attributes, wastewater effluent contribution, or hydrologic condition. Results from this study add to the body of information currently available on microplastics in different environmental compartments, including unique contributions to quantify their occurrence and variability in rivers with a wide variety of different land-use characteristics while highlighting differences between surface samples from rivers compared with lakes.

Environmental Science & Technology↗