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USGS2021

Racial, ethnic, and social patterns in the recreation specialization of birdwatchers: An analysis of United States eBird registrants

Although birdwatchers comprise a large and growing proportion of the American public, there is a lack of racial and ethnic diversity in the birdwatching community. Previous research suggests that this homogeneity is self-perpetuating, as ethno-racial minorities are less likely to pursue activities in which no one they know participates. However, it is unclear whether this trend in birdwatching participation also applies to degree of subsequent participant involvement. Using a national online survey of US birdwatchers, we measured the degree of recreation specialization among birdwatchers along affective, cognitive, and behavioral dimensions. We also determined whether respondents had social connections (acquaintances, close friends, or relatives) who birdwatch. We then used logistic regression to determine which ethno-racial groups were more likely to have birdwatcher social connections, and multiple linear regression to investigate how our measures of recreation specialization varied by ethno-racial group. As expected, the ethno-racial composition of the birdwatchers we studied was significantly less diverse than that of the American public. Of the 29,380 respondents who reported their ethno-racial group, 5.2% were Black, Indigenous, and/or people of color (including Native American, Black, Asian, Pacific Islander, Hispanic/Latino, or multiracial), while 94.8% were non-Hispanic White. However, we observed no statistically significant ethno-racial patterns in overall degree of recreation specialization, even when controlling for social connection and demographic characteristics. Considering the three dimensions of specialization individually, we found that some ethno-racial predictors were statistically significant, but coefficients were too small to be practically significant. We conclude that while some ethno-racial groups are underrepresented among birdwatchers, there is insufficient evidence that they are also under-specialized.

Journal of Outdoor Recreation and Tourism↗

USGS2009

Variations in population exposure and sensitivity to lahar hazards from Mount Rainier, Washington

Although much has been done to understand, quantify, and delineate volcanic hazards, there are fewer efforts to assess societal vulnerability to these hazards, particularly demographic differences in exposed populations or spatial variations in exposure to regional hazards. To better understand population diversity in volcanic hazard zones, we assess the number and types of people in a single type of hazard zone (lahars) for 27 communities downstream of Mount Rainier, Washington (USA). Using various socioeconomic and hazard datasets, we estimate that there are more than 78 000 residents, 59 000 employees, several dependent-population facilities (e.g., child-day-care centers, nursing homes) and numerous public venues (e.g., churches, hotels, museums) in a Mount Rainier lahar-hazard zone. We find that communities vary in the primary category of individuals in lahar-prone areas-exposed populations are dominated by residents in some communities (e.g., Auburn), employees in others (e.g., Tacoma), and tourists likely outnumber both of these groups in yet other areas (e.g., unincorporated Lewis County). Population exposure to potential lahar inundation varies considerably-some communities (e.g., Auburn) have large numbers of people but low percentages of them in hazard zones, whereas others (e.g., Orting) have fewer people but they comprise the majority of a community. A composite lahar-exposure index is developed to help emergency managers understand spatial variations in community exposure to lahars and results suggest that Puyallup has the highest combination of high numbers and percentages of people and assets in lahar-prone areas. Risk education and preparedness needs will vary based on who is threatened by future lahars, such as residents, employees, tourists at a public venue, or special-needs populations at a dependent-care facility. Emergency managers must first understand the people whom they are trying to prepare before they can expect these people to take protective measures after recognizing natural cues or receiving an official lahar warning.

Washington↗

USGS2021

Growth of the wildland-urban interface within and around U.S. National Forests and Grasslands, 1990-2010

The wildland-urban interface (WUI), where housing is in close proximity to or intermingled with wildland vegetation, is widespread throughout the United States, but it is unclear how this type of housing development affects public lands. We used a national dataset to examine WUI distribution and growth (1990–2010) in proximity to National Forests and created a typology to characterize each National Forest’s combination of WUI area and housing growth. We found that National Forests are hotspots for WUI growth, with a 38% increase in WUI area and 46% growth in WUI houses from 1990 to 2010, in excess of WUI growth for the conterminous U.S. Growth within National Forests was higher than the surrounding area. Diffuse intermix WUI, where houses are intermingled with wildland vegetation, is common within National Forests, but WUI houses around National Forests were primarily in denser interface WUI areas, which lack substantial wildland vegetation. WUI was more prevalent within and around National Forests in the East, while National Forests in the West experienced higher rates of WUI growth. National Forests with the most challenging WUI issues—extensive WUI area and rapid growth in intermix and interface—were found primarily in the South and interior West. Given the diversity of WUI landscapes, effectively responding to current and future WUI challenges will require both engagement with individual homeowners dispersed throughout National Forests, as well as increased emphasis on mitigating denser interface development around National Forests. At a time when wildfire risks are expected to intensify due to climate change, and 75% of privately owned land within and around National Forests is not yet WUI, understanding WUI growth patterns in proximity to public lands is vital for land management and human well-being.

Landscape and Urban Planning↗

USGS2025

An audience segmentation study of native plant gardening behaviors in the United States

Audience segmentation can be used to identify target audiences in environmental public engagement and communication, but few studies have used segmentation to study biodiversity conservation behavior. This study used segmentation to better understand perceptions and behaviors around different types of actions related to native plant gardening. With a United States representative survey ( n = 1,200), we measured beliefs and intentions to engage in personal-sphere (i.e., individual), social diffusion (i.e., encouraging others to act), and civic action behavior (e.g., voting). A latent class analysis (LCA) revealed four distinct groups within the population: Disengaged, Potential Adopters, Potential Amplifiers, and Potential Advocates. Each class comprised approximately one-quarter of the United States population. We found that certain groups are more receptive to personal-sphere behavior, while others may be more receptive to social diffusion behavior or civic action behavior. The groups varied by key distinguishing characteristics: perceptions around civic action, previous personal-sphere and social diffusion behavior, and intentions to engage in personal-sphere action. Findings revealed opportunities to create tailored public engagement strategies to engage different groups in urban biodiversity conservation behavior.

Landscape and Urban Planning↗

USGS2018

Developing Foram-AMBI for biomonitoring in the Mediterranean: Species assignments to ecological categories

Most environmental bio-monitoring methods using the species composition of marine faunas define the Ecological Quality Status of soft bottom ecosystems based on the relative proportions of species assigned to a limited number of ecological categories. In this study we analyse the distribution patterns of benthic foraminifera in the Mediterranean as a function of organic carbon gradients on the basis of 15 publications and assign the individual species to five ecological categories. Our categories (of sensitive, indifferent and 3rd, 2nd and 1st order opportunists) are very similar to the ecological categories commonly used for macrofauna, but show some minor differences. In the 15 analysed publications, we considered the numerical data of 493 taxa, of which 199 could be assigned. In all 79 taxa were classified as sensitive, 60 as indifferent, 46 as 3rd order, 12 as 2nd order and 2 as 1st order opportunists. The remaining 294 taxa are all accessory, and will only marginally contribute to biotic indices based on relative species proportions. In this paper we wanted also to explain the methodology we used for these species assignments, paying particular attention to all complications and problems encountered. We think that the species list proposed here will constitute a highly useful tool for foraminiferal bio-monitoring of soft bottoms in the Mediterranean Sea, which can be used in different ecological indices (Foram-AMBI and similar methods). With additional information becoming available in the next few years, it will be possible to expand the list, and, if necessary, to apply some minor corrections. As a next step, we intend to test this species list using several biotic indices, in a number of independent data sets, as soon as these will become available.

Marine Micropaleontology↗

USGS2020

Utilization of multiple microbial tools to evaluate efficacy of restoration strategies to improve recreational water quality at a Lake Michigan Beach (Racine, WI)

Hydro-meteorological conditions facilitate transport of fecal indicator bacteria (FIB) to the nearshore environment, affecting recreational water quality. North Beach (Racine, Wisconsin, United States), is an exemplar public beach site along Lake Michigan, where precipitation-mediated surface runoff, wave encroachment, stormwater and tributary outflow were demonstrated to contribute to beach advisories. Multiple restoration actions, including installation of a stormwater retention wetland, were successfully deployed to improve recreational water quality. Implementation of molecular methods (e.g. human microbial source tracking markers and Escherichia coli ( E. coli ) qPCR) assisted in identifying potential pollution sources and improving public health response time. However, periodic water quality failures still occur. As local beach managers reassess restoration measures in response to climatic changes, use of expanded microbial methods (including bacterial community profiling) may contribute to a better understanding of these dynamic environments. In this 2-year study (2015 and 2019), nearshore/offshore Lake Michigan, stormwater, and tributary samples were collected to determine if, 1) the constructed wetland (~50 m from the shoreline) continued to provide stormwater separation/retention and 2) mixing between onshore sources, Root River and Lake Michigan, was increasing due to rising precipitation/lake levels. Monthly rainfall totals were 1.5× higher in 2019 than 2015, coinciding with a 0.63 m lake-level rise. The prevalence of more intense, onshore winds also increased, facilitating interaction between potential reservoirs of FIB with nearshore water through wind driven waves and lake intrusion, e.g. beach sands and the adjacent Root River. While a strong relationship existed between wet weather wetland and North Beach nearshore E. coli concentrations (all sites), bacterial communities were strikingly different. Conversely, bacterial community overlap existed between the Root River mouth and nearshore/offshore sites. These results suggest the constructed wetland can accommodate the climate-related changes observed in this study. Future restoration activities could be directed towards upstream tributary sources in order to minimize microbial contaminants entering Lake Michigan.

Wisconsin↗

USGS2022

Spatial social value distributions for multiple user groups in a coastal national park

Managing public lands to maximize societal benefits requires spatially explicit understanding of societal valuation, and public participation geographic information systems (PPGIS) are increasingly used in coastal settings to accomplish this task. Social Values for Ecosystem Services (SolVES), a PPGIS tool that systematizes the mapping and modeling of social values and cultural ecosystem services, is promising for use in coastal settings but has seen relatively limited applications relative to other PPGIS approaches; it has also, to our knowledge, not yet been applied in a barrier island setting. In this study, we surveyed two visitor groups and residents living near Cape Lookout National Seashore (North Carolina, USA) to understand their social values in the context of the park's management needs. We developed social-value models to evaluate differences between three user groups (fall visitors, summer visitors, and residents) and to evaluate how respondents' experiences, attitudes, and recreational activities influence the locations they value and their most strongly held value types, which included aesthetic, recreation, biodiversity, future, therapeutic, and historic values. We found that accessibility, user types and the seasonality of major recreational activities, and the linear configuration of the barrier island system at Cape Lookout are important influences on the social values held by visitors and residents. The modeling results provide information relevant to management at Cape Lookout and can inform the design of future PPGIS studies in coastal and marine settings.

North Carolina↗

USGS2005

The Younger Dryas phase of Great Salt Lake, Utah, USA

Field investigations at the Public Shooting Grounds (a wildlife-management area on the northeastern shore of Great Salt Lake) and radiocarbon dating show that the Great Salt Lake rose to the Gilbert shoreline sometime between 12.9 and 11.2 cal ka. We interpret a ripple-laminated sand unit exposed at the Public Shooting Grounds, and dated to this time interval, as the nearshore sediments of Great Salt Lake deposited during the formation of the Gilbert shoreline. The ripple-laminated sand is overlain by channel-fill deposits that overlap in age (11.9-11.2 cal ka) with the sand, and by wetland deposits (11.1 to 10.5 cal ka). Consistent accelerator mass spectrometry radiocarbon ages were obtained from samples of plant fragments, including those of emergent aquatic plants, but mollusk shells from spring and marsh deposits yielded anomalously old ages, probably because of a variable radiocarbon reservoir effect. The Bonneville basin was effectively wet during at least part of the Younger Dryas global-cooling interval, however, conflicting results from some Great Basin locations and proxy records indicate that the regional effects of Younger Dryas cooling are still not well understood. ?? 2005 Elsevier B.V. All rights reserved.

Palaeogeography, Palaeoclimatology, Palaeoecology↗

USGS2018

An introduction and practical guide to use of the Soil-Vegetation Inventory Method (SVIM) data

Long-term vegetation dynamics across public rangelands in the western United States are not well understood because of the lack of large-scale, readily available historic datasets. The Bureau of Land Management’s Soil-Vegetation Inventory Method (SVIM) program was implemented between 1977 and 1983 across 14 western states, but the data have not been easily accessible. We introduce the SVIM vegetation cover dataset in a georeferenced, digital format; summarize how the data were collected; and discuss potential limitations and biases. We demonstrate how SVIM data can be compared with contemporary monitoring datasets to quantify changes in vegetation associated with wildfire and the abundance of exotic invasive species. Specifically, we compare SVIM vegetation cover data with cover data collected by BLM’s Assessment, Inventory, and Monitoring (AIM) program (2011–2016) in a focal area in the northern Great Basin. We address issues associated with analyzing and interpreting data from these distinct programs, including differences in survey methods and potential biases introduced by spatial and temporal variation in sampling. We compared SVIM and AIM survey methods at 44 plots and found that percent cover estimates had high correspondence for all measured functional groups. Comparisons between historic SVIM data and recent AIM data documented significant declines in the occupancy and cover of native shrubs and native perennial forbs , and a significant increase in exotic annual forbs. Wildfire was a driver of change for some functional groups, with greater change occurring in AIM plots that burned between the two time periods compared with those that did not. Our results are consistent with previous studies showing that many native shrub-dominated plant communities in the Great Basin have been replaced by exotic annuals. Our study demonstrates that SVIM data will be an important resource for researchers interested in quantifying vegetation change through time across public rangelands in the western United States.

Rangeland Ecology and Management↗

USGS2026

Spatial variation in effectiveness and costs of sagebrush restoration treatments across the western United States

Natural resource managers strive to improve restoration efficiency across the vast network of public lands of the United States, seeking the best return on investment through innovation, geographic prioritization, and adaptive management. This challenge is exemplified by ecosystems dominated by sagebrush ( Artemisia spp.), which occur across the western United States and have been degraded by increasing wildfire frequency driven by invasive plant spread, among other factors. However, both costs and effectiveness of sagebrush restoration can vary spatially due to management practices in addition to biotic and abiotic factors, and characterizing this variation could inform broad-scale planning. We leveraged published models of sagebrush recovery and treatment costs to predict and evaluate cost-effectiveness of aerial and drill seeding Artemisia spp. across 429 718 km 2 that overlapped 12 US states. Compared to natural recovery, effectiveness for both methods was generally low, yet effectiveness was often greater, and costs were always greater, for drill than aerial seeding, resulting in slightly higher cost-effectiveness on average for drill seeding. Cost-effectiveness for both treatments increased near major roads and in areas with more repeated burns. Cost-effectiveness also increased with predisturbance cover of sagebrush but decreased with herbaceous cover. However, we also identified areas where aerial seeding was more cost-effective than drill seeding, particularly with greater slope. Our results provide spatially explicit estimates and potential mechanisms of cost-effectiveness for two common seeding methods for sagebrush, which can help prioritize limited resources, guide land use, and improve restoration efficiency and effectiveness across public rangelands of the western United States.

western United States↗

USGS2008

Effectiveness of household reverse-osmosis systems in a Western U.S. region with high arsenic in groundwater

It is well known to the public in Lahontan Valley in rural Nevada, USA, that local aquifers produce water with varied, but sometimes very high concentrations of arsenic (> 4??ppm). As a result, many residents of the area have installed household reverse-osmosis (RO) systems to produce drinking water. We examined performance of RO systems and factors associated with arsenic removal efficiency in 59 households in Lahontan Valley. The sampling results indicated that RO systems removed an average of 80.2% of arsenic from well water. In 18 of the 59 households, arsenic concentrations exceeded 10??ppb in treated water, with a maximum in treated water of 180??ppb. In 3 of the 59 households, RO treatment had little effect on specific conductance, indicating that the RO system was not working properly. Two main factors lead to arsenic levels in treated water exceeding drinking-water standards in the study area. First, arsenic concentrations were high enough in some Lahontan Valley wells that arsenic levels exceeded 10??ppb even though RO treatment removed more than 95% of the arsenic. Second, trivalent As+ 3 was the dominant arsenic species in approximately 15% of the wells, which significantly reduced treatment efficiency. Measurements of specific conductance indicated that efficiency in reducing arsenic levels did not always correlate with reductions in total dissolved solids. As a consequence, improvements in taste of the water or simple measurements of specific conductance made by technicians to test RO systems can mislead the public into assuming the water meets safety standards. Actual measurements of treated water are necessary to assure that household RO systems are reducing arsenic concentrations to safe levels, particularly in areas where groundwater has high arsenic concentrations or where As+ 3 is the dominant species. ?? 2007 Elsevier B.V. All rights reserved.

Science of the Total Environment↗

USGS2014

Factors affecting temporal variability of arsenic in groundwater used for drinking water supply in the United States

The occurrence of arsenic in groundwater is a recognized environmental hazard with worldwide importance and much effort has been focused on surveying and predicting where arsenic occurs. Temporal variability is one aspect of this environmental hazard that has until recently received less attention than other aspects. For this study, we analyzed 1245 wells with two samples per well. We suggest that temporal variability, often reported as affecting very few wells, is perhaps a larger issue than it appears and has been masked by datasets with large numbers of non-detect data. Although there was only a slight difference in arsenic concentration variability among samples from public and private wells (p = 0.0452), the range of variability was larger for public than for private wells. Further, we relate the variability we see to geochemical factors—primarily variability in redox—but also variability in pH and major-ion chemistry. We also show that in New England there is a weak but statistically significant indication that seasonality may have an effect on concentrations, whereby concentrations in the first two quarters of the year (January–June) are significantly lower than in the second two quarters (July–December) (p < 0.0001). In the Central Valley of California, though not statistically significant (p = 0.4169), arsenic concentration is lower in the first quarter of the year but increases in subsequent quarters. In both regions, these changes appear to follow groundwater levels. It is possible that this difference in arsenic concentrations is related to groundwater level changes, pumping stresses, evapotranspiration effects, or perhaps mixing of more oxidizing, lower pH recharge water in wetter months. Focusing on the understanding the geochemical conditions in aquifers where arsenic concentrations are concerns and causes of geochemical changes in the groundwater environment may lead to a better understanding of where and by how much arsenic will vary over time.

Science of the Total Environment↗

USGS2016

Hg concentrations in fish from coastal waters of California and Western North America

The State of California conducted an extensive and systematic survey of mercury (Hg) in fish from the California coast in 2009 and 2010. The California survey sampled 3483 fish representing 46 species at 68 locations, and demonstrated that methylHg in fish presents a widespread exposure risk to fish consumers. Most of the locations sampled (37 of 68) had a species with an average concentration above 0.3 μg/g wet weight (ww), and 10 locations an average above 1.0 μg/g ww. The recent and robust dataset from California provided a basis for a broader examination of spatial and temporal patterns in fish Hg in coastal waters of Western North America. There is a striking lack of data in publicly accessible databases on Hg and other contaminants in coastal fish. An assessment of the raw data from these databases suggested the presence of relatively high concentrations along the California coast and in Puget Sound, and relatively low concentrations along the coasts of Alaska and Oregon, and the outer coast of Washington. The dataset suggests that Hg concentrations of public health concern can be observed at any location on the coast of Western North America where long-lived predator species are sampled. Output from a linear mixed-effects model resembled the spatial pattern observed for the raw data and suggested, based on the limited dataset, a lack of trend in fish Hg over the nearly 30-year period covered by the dataset. Expanded and continued monitoring, accompanied by rigorous data management procedures, would be of great value in characterizing methylHg exposure, and tracking changes in contamination of coastal fish in response to possible increases in atmospheric Hg emissions in Asia, climate change, and terrestrial Hg control efforts in coastal watersheds.

Science of the Total Environment↗

USGS2017

A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA

Intense demand for water in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource. To assess contamination risk in the region, we developed a hybrid, non-linear, machine learning model within a statistical learning framework to predict nitrate contamination of groundwater to depths of approximately 500 m below ground surface. A database of 145 predictor variables representing well characteristics, historical and current field and landscape-scale nitrogen mass balances, historical and current land use, oxidation/reduction conditions, groundwater flow, climate, soil characteristics, depth to groundwater, and groundwater age were assigned to over 6000 private supply and public supply wells measured previously for nitrate and located throughout the study area. The boosted regression tree (BRT) method was used to screen and rank variables to predict nitrate concentration at the depths of domestic and public well supplies. The novel approach included as predictor variables outputs from existing physically based models of the Central Valley. The top five most important predictor variables included two oxidation/reduction variables (probability of manganese concentration to exceed 50 ppb and probability of dissolved oxygen concentration to be below 0.5 ppm), field-scale adjusted unsaturated zone nitrogen input for the 1975 time period, average difference between precipitation and evapotranspiration during the years 1971–2000, and 1992 total landscape nitrogen input. Twenty-five variables were selected for the final model for log-transformed nitrate. In general, increasing probability of anoxic conditions and increasing precipitation relative to potential evapotranspiration had a corresponding decrease in nitrate concentration predictions. Conversely, increasing 1975 unsaturated zone nitrogen leaching flux and 1992 total landscape nitrogen input had an increasing relative impact on nitrate predictions. Three-dimensional visualization indicates that nitrate predictions depend on the probability of anoxic conditions and other factors, and that nitrate predictions generally decreased with increasing groundwater age.

California↗

USGS2019

Pesticides and pollinators: A socioecological synthesis

The relationship between pesticides and pollinators , while attracting no shortage of attention from scientists, regulators, and the public, has proven resistant to scientific synthesis and fractious in matters of policy and public opinion. This is in part because the issue has been approached in a compartmentalized and intradisciplinary way, such that evaluations of organismal pesticide effects remain largely disjoint from their upstream drivers and downstream consequences. Here, we present a socioecological framework designed to synthesize the pesticide-pollinator system and inform future scholarship and action. Our framework consists of three interlocking domains-pesticide use, pesticide exposure, and pesticide effects–each consisting of causally linked patterns, processes, and states. We elaborate each of these domains and their linkages, reviewing relevant literature and providing empirical case studies. We then propose guidelines for future pesticide-pollinator scholarship and action agenda aimed at strengthening knowledge in neglected domains and integrating knowledge across domains to provide decision support for stakeholders and policymakers. Specifically, we emphasize (1) stakeholder engagement, (2) mechanistic study of pesticide exposure, (3) understanding the propagation of pesticide effects across levels of organization, and (4) full-cost accounting of the externalities of pesticide use and regulation. Addressing these items will require transdisciplinary collaborations within and beyond the scientific community, including the expertise of farmers, agrochemical developers, and policymakers in an extended peer community.

Science of the Total Environment↗

USGS2020

Economic, land use, and ecosystem services impacts of Rwanda's Green Growth Strategy: An application of the IEEM+ESM platform

We develop and link the Integrated Economic-Environmental Modeling (IEEM) Platform to ecosystem services modeling (ESM). The IEEM+ESM Platform is an innovative decision-making framework for exploring complex public policy goals and elucidating synergies and trade-offs between alternative policy portfolios. The IEEM+ESM approach is powerful in its ability to shed light on (i) change in land use and ecosystem services driven by public policy and the supply and demand responses of businesses and households; and (ii) impacts on standard economic indicators of concern to Ministries of Finance such as gross domestic product and employment, as well as changes in wealth and ecosystem services. The IEEM+ESM approach is being adopted rapidly and by the end of 2020, IEEM+ESM Platforms will be implemented for about 25 countries. To demonstrate the insights generated by the IEEM+ESM approach, we apply it to the analysis of alternative green growth strategies in Rwanda, a country that has made strong progress in reducing poverty and enhancing economic growth in the last 15 years. The case of Rwanda is particularly compelling as it faces intense pressure on its natural capital base and ecosystem services, already with the highest population density in Africa, which is projected to double by 2050. In applying IEEM+ESM and comparing the outcomes of Rwanda’s green growth policies, increasing fertilization of agricultural crops shows the largest economic gains but also trade-offs in environmental quality reflected through higher nutrient export and reduced water quality. Combining crop fertilization with forest plantations better balances critical ecosystem services and their role in underpinning economic development as Rwanda progresses toward its target of middle-income status by 2035. This application to Rwanda’s green growth strategy demonstrates the value-added of the IEEM+ESM approach in generating results that speak to both economic outcomes and impacts on market and non-market ecosystem services.

Science of the Total Environment↗

USGS2024

A brief note on substantial sub-daily arsenic variability in pumping drinking-water wells in New Hampshire

Large variations in redox-related water parameters, like pH and dissolved oxygen (DO), have been documented in New Hampshire (United States) drinking-water wells over the course of a few hours under pumping conditions. These findings suggest that comparable sub-daily variability in dissolved concentrations of redox-reactive and toxic arsenic (As) also may occur, representing a potentially critical public-health data gap and a fundamental challenge for long-term As-trends monitoring. To test this hypothesis, discrete groundwater As samples were collected approximately hourly during one day in May and again in August 2019 from three New Hampshire drinking-water wells (2 public-supply, 1 private) under active pumping conditions. Collected samples were assessed by laboratory analysis (total As [As Tot ], As(III), As(V)) and by field analysis (As Tot ) using a novel integrated biosensor system. Laboratory analysis revealed sub-daily variability (range) in As Tot concentrations equivalent to 16 % – 36 % of that observed in the antecedent 3-year bimonthly trend monitoring. Thus, the results indicated that, along with previously demonstrated seasonality effects, the timing and duration of pumping are important considerations when assessing trends in drinking-water As exposures and concomitant risks. Results also illustrated the utility of the field sensor for monitoring and management of As Tot exposures in near-real-time.

Science of the Total Environment↗

USGS2026

Legacy of the fumigant 1,2-dibromo-3-chloropropane (DBCP) in California groundwater

The fumigant pesticide 1,2-dibromo-3-chloropropane (DBCP) was widely used in California agriculture during the 1960s and 1970s before being banned in 1979. Despite this ban, DBCP continues to contaminate groundwater due to its persistence and mobility. This study evaluates the distribution, historical trends, and projected persistence of DBCP in California using data from over 13,000 public supply wells and additional domestic, irrigation, and observation wells (1980-2022). Since 2010, DBCP has been detected in 9% of public supply wells statewide, with higher frequencies in the San Joaquin Valley (21%) and upper Santa Ana River watershed (13%), where DBCP use was most prevalent. Approximately 70% of wells had decreasing concentration trends, whereas increases were more common in deeper wells, indicating downward vertical migration of the DBCP front. Groundwater age estimates show that recharge timing aligns with the 1960s–1970s loading period, enabling reconstruction of peak inputs and providing a basis for age based modeling. To estimate future persistence, we applied a one dimensional advection–dispersion model that simulates long term declines in peak concentrations based on groundwater age, historical loading, and a 38 year degradation half life. Model projections suggest that concentrations above the maximum contaminant level may persist in a declining number of wells until approximately 2080 (range: 2048–2109), with longer persistence in the San Joaquin Valley. The simplified modeling framework, based on age distributions typical of wells capturing peak concentrations, can provide practical regional scale assessment of non-point source contaminants where long-term monitoring exists. This study highlights how the legacy of DBCP contamination will likely affect California's groundwater resources throughout the 21st century.

California↗