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At least 379 records · Page 21Linked to original sources
USGS2018

Bioactive contaminants of emerging concern in National Park waters of the northern Colorado Plateau, USA

Pharmaceuticals and personal care products (PPCPs), wastewater indicators (WWIs), and pesticides (herein, Contaminants of Emerging Concern [CECs]) have been documented in surface waters throughout the world and have associated risks to aquatic life. While much research has focused on temperate and urbanized watersheds, less is known about CEC presence in semi-arid landscapes, where water availability is limited and populations are low. CEC presence in water and sediment is reported for 21 sites in eight U.S. national parks in the northern Colorado Plateau region. From 2012 to 2016, at least one PPCP and/or WWI was detected at most sites on over half of sampling visits, indicating that CECs are not uncommon even in isolated areas. CEC detections were generally fewer and at lower concentrations than in urbanized or agricultural watersheds. Consistent with studies from other U.S. regions, the most frequently detected CECs in this study include DEET, caffeine, organophosphorus flame retardants, and bisphenol A in water and fecal indicators and polycyclic aromatic hydrocarbons in sediment. Maximum concentrations in this study were generally below available water quality benchmarks, sediment quality guidelines, and risk assessment thresholds associated with vertebrates. Additional work is needed to assess the potential activity of hormones, which had high reporting limits in our study, and potential bioactivity of environmental concentrations for invertebrates, microbial communities, and algae. Potential sources of CEC contamination include upstream wastewater effluent discharges and National Park Service invasive-plant-control herbicide applications. CEC occurrence patterns and similarities between continuous and isolated flow locations suggest that direct contamination from individual visitors may also occur. While our data indicate there is little aquatic health risk associated with CECs at our sites, our results demonstrate the ubiquity of CECs on the landscape and a continued need for public outreach concerning resource-use ethics and the potential effects of upstream development.

Colorado Plateau↗
USGS2018

Inferring watershed hydraulics and cold-water habitat persistence using multi-year air and stream temperature signals

Streams strongly influenced by groundwater discharge may serve as “climate refugia” for sensitive species in regions of increasingly marginal thermal conditions. The main goal of this study is to develop paired air and stream water annual temperature signal analysis techniques to elucidate the relative groundwater contribution to stream water and the effective groundwater flowpath depth. Groundwater discharge to streams attenuates surface water temperature signals, and this attenuation can be diagnostic of groundwater gaining systems. Additionally, discharge from shallow groundwater flowpaths can theoretically transfer lagged annual temperature signals from aquifer to stream water. Here we explore this concept using multi-year temperature records from 120 stream sites located across 18 mountain watersheds of Shenandoah National Park, VA, USA and a coastal watershed in Massachusetts, USA. Both areas constitute important cold-water habitat for native brook trout ( Salvelinus fontinalis ). Observed annual temperature signals indicate a dominance of shallow groundwater discharge to streams in the National Park, in contrast to the coastal watershed that has strong, apparently deeper, groundwater influence. The average phase lag from air to stream signals in Shenandoah National Park is 11 d; however, extended lags of approximately 1 month were observed in a subset of streams. In contrast, the coastal stream has pronounced attenuation of annual temperature signals without notable phase lag. To better understand these observed differences in signal characteristics, analytical and numerical models are used to quantify mixing of the annual temperature signals of surface and groundwater. Simulations using a total heat budget numerical model indicate groundwater-induced annual temperature signal phase lags are likely to show greater downstream propagation than the related signal amplitude attenuation. The measurement of multi-seasonal paired air and water temperatures offers great promise toward understanding catchment processes and informing current cold-water habitat management at ecologically-relevant scales.

Virginia↗
USGS2018

Chesapeake Bay's water quality condition has been recovering: Insights from a multimetric indicator assessment of thirty years of tidal monitoring data

To protect the aquatic living resources of Chesapeake Bay, the Chesapeake Bay Program partnership has developed guidance for state water quality standards, which include ambient water quality criteria to protect designated uses (DUs), and associated assessment procedures for dissolved oxygen (DO), water clarity/underwater bay grasses, and chlorophyll-a. For measuring progress toward meeting the respective states' water quality standards, a multimetric attainment indicator approach was developed to estimate combined standards attainment. We applied this approach to three decades of monitoring data of DO, water clarity/underwater bay grasses, and chlorophyll-a data on annually updated moving 3-year periods to track the progress in all 92 management segments of tidal waters in Chesapeake Bay. In 2014–2016, 40% of tidal water segment-DU-criterion combinations in the Bay (n = 291) are estimated to meet thresholds for attainment of their water quality criteria. This index score marks the best 3-year status in the entire record. Since 1985–1987, the indicator has followed a nonlinear trajectory, consistent with impacts from extreme weather events and subsequent recoveries. Over the period of record (1985–2016), the indicator exhibited a positive and statistically significant trend ( p < 0.05), indicating that the Bay has been recovering since 1985. Patterns of attainment of individual DUs are variable, but improvements in open water DO, deep channel DO, and water clarity/submerged aquatic vegetation have combined to drive the improvement in the Baywide indicator in 2014–2016 relative to its long-term median. Finally, the improvement in estimated Baywide attainment was statistically linked to the decline of total nitrogen, indicating responsiveness of attainment status to the reduction of nutrient load through various management actions since at least the 1980s.

Chesapeake Bay watershed↗
USGS2018

Examination of contaminant exposure and reproduction of ospreys (Pandion haliaetus) nesting in Delaware Bay and River in 2015

A study of ospreys ( Pandion haliaetus ) nesting in the coastal Inland Bays of Delaware, and the Delaware Bay and Delaware River in 2015 examined spatial and temporal trends in contaminant exposure, food web transfer and reproduction. Concentrations of organochlorine pesticides and metabolites, polychlorinated biphenyls (PCBs), coplanar PCB toxic equivalents, polybrominated diphenyl ethers (PBDEs) and other flame retardants in sample eggs were generally greatest in the Delaware River. Concentrations of legacy contaminants in 2015 Delaware Bay eggs were lower than values observed in the 1970s through early 2000s. Several alternative brominated flame retardants were rarely detected, with only TBPH [bis(2-ethylhexyl)-tetrabromophthalate)] present in 5 of 27 samples at <5 ng/g wet weight. No relation was found between p,p ′-DDE, total PCBs or total PBDEs in eggs with egg hatching, eggs lost from nests, nestling loss, fledging and nest success. Osprey eggshell thickness recovered to pre-DDT era values, and productivity was adequate to sustain a stable population. Prey fish contaminant concentrations were generally less than those in osprey eggs, with detection frequencies and concentrations greatest in white perch ( Morone americana ) from Delaware River compared to the Bay. Biomagnification factors from fish to eggs for p,p ′-DDE and total PCBs were generally similar to findings from several Chesapeake Bay tributaries. Overall, findings suggest that there have been improvements in Delaware Estuary waterbird habitat compared to the second half of the 20th century. This trend is in part associated with mitigation of some anthropogenic contaminant threats.

Delaware Bay and River↗
USGS2018

Quantifying anthropogenic contributions to century-scale groundwater salinity changes, San Joaquin Valley, California, USA

Total dissolved solids (TDS) concentrations in groundwater tapped for beneficial uses (drinking water, irrigation, freshwater industrial) have increased on average by about 100 mg/L over the last 100 years in the San Joaquin Valley, California (SJV). During this period land use in the SJV changed from natural vegetation and dryland agriculture to dominantly irrigated agriculture with growing urban areas. Century-scale salinity trends were evaluated by comparing TDS concentrations and major ion compositions of groundwater from wells sampled in 1910 (Historic) to data from wells sampled in 1993-2015 (Modern). TDS concentrations in subregions of the SJV, the southern (SSJV), western (WSJV), northeastern (NESJV), and southeastern (SESJV) were calculated using a cell-declustering method. TDS concentrations increased in all regions, with the greatest increases found in the SSJV and SESJV. Evaluation of the Modern data from the NESJV and SESJV found higher TDS concentrations in recently recharged (post-1950) groundwater from shallow (< 50 m) wells surrounded predominantly by agricultural land uses, while premodern (pre-1950) groundwater from deeper wells, and recently recharged groundwater from wells surrounded by mainly urban, natural, and mixed land uses had lower TDS concentrations, approaching the TDS concentrations in the Historic groundwater. For the NESJV and SESJV, inverse geochemical modeling with PHREEQC indicated that weathering of primary silicate minerals accounted for the majority of the increase in TDS concentrations, contributing more than nitrate from fertilizers and sulfate from soil amendments combined. Bicarbonate showed the greatest increase among major ions, resulting from enhanced silicate weathering due to recharge of irrigation water enriched in CO2 during the growing season. The results of this study demonstrate that large anthropogenic changes to the hydrologic regime, like massive development of irrigated agriculture in semi-arid areas like the SJV, can cause large changes in groundwater quality on a regional scale.

California↗
USGS2020

Relation of fish intersex to contaminants in riverine sport fishes

Endocrine active compounds (EACs) are pollutants that have been recognized as an emerging and widespread threat to aquatic ecosystems globally. Intersex, the presence of female germ cells within a predominantly male gonad, is considered a biomarker of endocrine disruption caused by EACs. We measured a suite of EACs and assessed their associated impacts on fish intersex occurrence and severity in a large, regulated river system in North Carolina and South Carolina, USA. Our specific objective was to determine the relationship of contaminants in water, sediment, and fish tissue with the occurrence and severity of the intersex condition in wild, adult black bass ( Micropterus ), sunfish ( Lepomis ), and catfish (Ictaluridae) species at 11 sites located on the Yadkin-Pee Dee River. Polycyclic aromatic hydrocarbons (PAHs), ethinylestradiol (EE2), and heavy metals were the most prevalent contaminants that exceeded effect levels for the protection of aquatic organisms. Fish intersex condition was most frequently observed and most severe in black basses and was less frequently detected and less severe in sunfishes and catfishes. The occurrence of the intersex condition in fish showed site-related effects, rather than increasing longitudinal trends from upstream to downstream. Mean black bass and catfish tissue contaminant concentrations were higher than that of sunfish, likely because of the latter's lower trophic position in the food web. Principal component analysis identified waterborne PAHs as the most correlated environmental contaminant with intersex occurrence and severity in black bass and sunfish. As indicated by the intersex condition, EACs have adverse but often variable effects on the health of wild sport fishes in this river, likely due to fluctuations in EAC inputs and the dynamic nature of the riverine system. These findings enhance the understanding of the relationship between contaminants and fish health and provide information to guide ecologically comprehensive conservation and management decisions.

North Carolina, South Carolina↗
USGS2018

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants in water, sediment, and tissue from Rocky Mountain National Park, 2012–2013

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants (BCs) are commonly detected in surface water and bed sediment in urban and suburban areas, but these contaminants are understudied in remote locations. In Rocky Mountain National Park (RMNP), Colorado, USA, BCs may threaten the reproductive success and survival of native aquatic species, benthic communities, and pelagic food webs. In 2012–2013, 67 water, 57 sediment, 63 fish, 10 frog, and 12 quality-control samples (8 water and 4 sediment) were collected from 20 sites in RMNP. Samples were analyzed for 369 parameters including 149 pharmaceuticals, 22 hormones, 137 pesticides, and 61 other chemicals or conditions to provide a representative assessment of BC occurrence within RMNP. Results indicate that BCs were detected in water and/or sediment from both remote and more accessible locations in RMNP. The most commonly detected BCs in water were caffeine, camphor, para-cresol, and DEET; and the most commonly detected BCs in sediment were indole, 3-methyl-1H-indole, para-cresol, and 2,6-dimethyl-naphthalene. Some detected contaminants, including carbaryl, caffeine, and oxycodone, are clearly attributable to direct local human input, whereas others may be transported into the park atmospherically (e.g., atrazine) or have local natural sources (e.g., para-cresol). One or more pharmaceuticals were detected in at least 1 sample from 15 of 20 sites. Most of the 29 detected pharmaceuticals are excreted primarily in human urine, not feces. Elevated net estrogenicity was observed in 18% of water samples, and elevated vitellogenin in blood was observed in 12% of male trout, both evidence of potential endocrine disruption. Hormone concentrations in sediment tended to be greater than concentrations in water. Most BCs were observed at concentrations below those not expected to pose adverse effects to aquatic life. Results indicate that even in remote locations aquatic wildlife can be exposed to pharmaceuticals, hormones, pesticides, and other bioactive contaminants.

Colorado↗
USGS2018

Temporal evaluation of estrogenic endocrine disruption markers in smallmouth bass (Micropterus dolomieu) reveals seasonal variability in intersex

A reconnaissance project completed in 2009 identified intersex and elevated plasma vitellogenin in male smallmouth bass inhabiting the Missisquoi River, VT. In an attempt to identify the presence and seasonality of putative endocrine disrupting chemicals or other factors associated with these observations, a comprehensive reevaluation was conducted between September 2012 and June 2014. Here, we collected smallmouth bass from three physically partitioned reaches along the river to measure biomarkers of estrogenic endocrine disruption in smallmouth bass. In addition, polar organic chemical integrative samples (POCIS) were deployed to identify specific chemicals associated with biological observations. We did not observe biological differences across reaches indicating the absence of clear point source contributions to the observation of intersex. Interestingly, intersex prevalence and severity decreased in a stepwise manner over the timespan of the project. Intersex decreased from 92.8% to 28.1%. The only significant predictor of intersex prevalence was year of capture, based on logistic regression analysis. The mixed model of fish length and year-of-capture best predicted intersex severity. Intersex severity was also significantly different across late summer and early spring collections indicating seasonal changes in this metric. Plasma vitellogenin and liver vitellogenin Aa transcript abundance in males did not indicate exposure to estrogenic endocrine disrupting chemicals at any of the four sample collections. Analysis of chemicals captured by the POCIS as well as results of screening discrete water samples or POCIS extracts did not indicate the contribution of appreciable estrogenic chemicals. It is possible that unreported changes in land-use activity have ameliorated the problem, and our observations indicate recovery. Regardless, this work clearly emphasizes that single, snap shot sampling for intersex may not yield representative data given that the manifestation of this condition within a population can change dramatically over time.

Vermont↗
USGS2019

Effects of ferric sulfate and polyaluminum chloride coagulation enhanced treatment wetlands on Typha growth, soil and water chemistry

Land surface subsidence is a concern in many deltas worldwide as it contributes to water quality degradation, loss of fertile land and increased potential for levee failure. As a possible solution to these concerns, on-site coagulation enhanced treatment wetlands(CETWs), coagulation water treatment followed by wetland passage serving as a settling basin, were implemented in a field-scale study located on a subsided island of the Sacramento-San Joaquin Delta in northern California under three treatments; coagulation with polyaluminum chloride (PAC), coagulation with ferric sulfate and an untreated control. Because CETWs offer a relatively novel solution for water quality improvement and subsidence reversal due to its low-infrastructure requirements and in-situ nature, effects from these systems remain uncharted and they may have adverse effects on plant biomass production that also contribute to sediment accretion. This study focuses on the effect CETWs had on the growth of Typha spp .; the dominant vegetation in the wetlands. Plant growth parameters and nutrient content were measured in conjunction with soil, pore waterand surface water chemistry. Soil analysis indicated there was no intermixing of newly formed flocs and original soil material. Where there was significant deposition of floc, PAC treatment reduced phosphate concentrations and ferric sulfate treatment increased total Fe concentrations in surrounding water compared to the control. Results indicated coagulation treatments had no negative effects on Typha leaf nutrient content, Typha growth or allometric parameters. Additionally, no signs of plant toxicity such as necrosis, wilting or chlorosis were observed in any of the treatments. Overall, this study suggests that CETWs are viable treatment option for water quality improvement and sediment accretion while having no negative impact on the growth of Typha plants.

Science of the Total Environment↗
USGS2019

Tracing the cycling and fate of the munition, Hexahydro-1,3,5-trinitro-1,3,5-triazine in a simulated sandy coastal marine habitat with a stable isotopic tracer, 15N-[RDX]

Coastal marine habitats become contaminated with the munitions constituent, Hexahydro-1,3,5-trinitro-1,3,5-trazine (RDX), via military training, weapon testing and leakage of unexploded ordnance. This study used 15 N labeled RDX in simulated aquarium-scale coastal marine habitat containing seawater, sediment, and biota to track removal pathways from surface water including sorption onto particulates, degradation to nitroso-triazines and mineralization to dissolved inorganic nitrogen (DIN). The two aquaria received continuous RDX inputs to maintain a steady state concentration (0.4 mg L −1 ) over 21 days. Time series RDX and nitroso-triazine concentrations in dissolved (surface and porewater) and sorbed phases (sediment and suspended particulates) were analyzed. Distributions of DIN species (ammonium, nitrate + nitrite and dissolved N 2 ) in sediments and overlying water were also measured along with geochemical variables in the aquaria. Partitioning of RDX and RDX-derived breakdown products onto surface sediment represented 13% of the total added 15 N as RDX ( 15 N-[RDX]) equivalents after 21 days. Measured nitroso-triazines in the aquaria accounted for 6–13% of total added 15 N-[RDX]. 15 N-labeled DIN was found both in the oxic surface water and hypoxic porewaters, showing that RDX mineralization accounted for 34% of the 15 N-[RDX] added to the aquaria over 21 days. Labeled ammonium ( 15 NH 4 + , found in sediment and overlying water) and nitrate + nitrite ( 15 NO X , found in overlying water only) together represented 10% of the total added 15 N-[RDX]. The production of 15 N labeled N 2 ( 15 N 2 ), accounted for the largest individual sink during the transformation of the total added 15 N-[RDX] (25%). Hypoxic sediment was the most favorable zone for production of N 2 , most of which diffused through porous sediments into the water column and escaped to the atmosphere.

Science of the Total Environment↗
USGS2019

Geochemical sourcing of runoff from a young volcanic watershed to an impacted coral reef in Pelekane Bay, Hawaii

Runoff of sediment and other contaminants from developed watersheds threatens coastal ecosystems and services. A sediment geochemical sourcing study was undertaken on a sediment-impacted coral reef flat to identify terrestrial sediment sources and how these changed over time. Geochemical signatures were identified for watershed soils that formed on Hawaiian basaltic and alkalic lavas using relatively immobile compatible (Ni, Sc) and incompatible (Nb, REE , Th) elements quantified by ICP-MS in total decompositions of the fine fraction of surface soils. Some soils also contained ash from late-erupting cinder cones that added alkalic geochemical signatures, resulting in distinctive mixed signatures near these geologic features. Sediment was collected in Pelekane Bay using sediment traps during winter 2010–2011 and a sediment core in order to geochemically source runoff entering the bay. Geochemical signatures in trapped sediment showed that runoff predominantly originated from the lower watershed along a highway corridor rather than from the upper watershed or areas with alkalic lavas. Soil in the highway corridor also contained Zn above levels of concern for aquatic organisms and anthropogenic Pb, indications that runoff control measures could reduce the exposure of the reef community to potentially toxic metals and other road-associated contaminants. The upper portion of a 60-yr long sediment record from Pelekane Bay was disturbed by tsunamigenic waves from the Tohoku earthquake , and the remainder was likely subject to mixing by winter waves that averaged out geochemical variations. On average, watershed regions with basaltic soils were the predominant source of runoff to the bay over the past 60 years. By linking sediment runoff to geographic regions or features in watersheds, geochemical sourcing can provide insights that allow resource managers to direct runoff mitigation and soil conservation efforts to areas where they will be most effective.

Hawaii↗
USGS2019

Human-induced and natural carbon storage in floodplains of the Central Valley of California

Active floodplains can putatively store large amounts of organic carbon (SOC) in subsoils originating from catchment erosion processes with subsequent floodplain deposition. Our study focussed on the assessment of SOC pools associated with alluvial floodplain soils that are affected by human-induced changes in floodplain deposition and in situ SOC mineralisation due to land use change and drainage. We evaluated depth-dependent SOC contents based on 23 soil cores down to 3 m and 10 drillings down to 7 m in a floodplain area of the lower Cosumnes River. An estimate of 266 Mg C ha −1 or about 59% of the entire SOC stored within the 7 m profiles was found in the upper 2 m. Most profiles (n = 25) contained discrete buried A horizons at depths of approximately 0.8 m. These profiles had up to 130% higher SOC stocks. The mean δ 13 C of all deep soil profiles clearly indicated that arable land use has already altered the stable isotopic signature in the first meter of the profile. Radiocarbon dating showed that the 14 C age in the buried horizon was younger than in overlaying soils indicating a substantial sedimentation phase for the overlaying soils. An additional analysis of total mercury contents in the soil profiles indicated that this sedimentation was associated with upstream hydraulic gold mining after the 1850s. In summary, deep alluvial soils in floodplains store large amounts of SOC not yet accounted for in global carbon models. Historic data give evidence that large amounts of sediment were transported into the floodplains of most rivers of the Central Valley and deposited over organically rich topsoil, which promoted the stabilization of SOC, and needs to be considered to improve our understanding of the human-induced interference with C cycling.

California↗
USGS2019

Towards globally customizable ecosystem service models

Scientists, stakeholders and decision makers face trade-offs between adopting simple or complex approaches when modeling ecosystem services (ES). Complex approaches may be time- and data-intensive, making them more challenging to implement and difficult to scale, but can produce more accurate and locally specific results. In contrast, simple approaches allow for faster assessments but may sacrifice accuracy and credibility. The ARtificial Intelligence for Ecosystem Services (ARIES) modeling platform has endeavored to provide a spectrum of simple to complex ES models that are readily accessible to a broad range of users. In this paper, we describe a series of five “Tier 1” ES models that users can run anywhere in the world with no user input, while offering the option to easily customize models with context-specific data and parameters. This approach enables rapid ES quantification, as models are automatically adapted to the application context. We provide examples of customized ES assessments at three locations on different continents and demonstrate the use of ARIES' spatial multi-criteria analysis module, which enables spatial prioritization of ES for different beneficiary groups. The models described here use publicly available global- and continental-scale data as defaults. Advanced users can modify data input requirements, model parameters or entire model structures to capitalize on high-resolution data and context-specific model formulations. Data and methods contributed by the research community become part of a growing knowledge base, enabling faster and better ES assessment for users worldwide. By engaging with the ES modeling community to further develop and customize these models based on user needs, spatiotemporal contexts, and scale(s) of analysis, we aim to cover the full arc from simple to complex assessments, minimizing the additional cost to the user when increased complexity and accuracy are needed.

Science of the Total Environment↗
USGS2019

Water-quality trends in U.S. rivers, 2002 to 2012: Relations to levels of concern

Effective management and protection of water resources relies upon understanding how water-quality conditions are changing over time. Water-quality trends for ammonia, chloride, nitrate, sulfate, total dissolved solids (TDS), total nitrogen (TN) and total phosphorus (TP) were assessed at 762 sites located in the conterminous United States between 2002 and 2012. Annual mean concentrations at the start and end of the trend period were compared to an environmentally meaningful level of concern (LOC) to categorize patterns in water-quality changes. Trend direction, magnitude, and the proximity of concentrations to LOCs were investigated. Of the 1956 site-constituent combinations investigated, 30% were above the LOC in 2002, and only six (0.3%) crossed the LOC threshold, either from above or below, indicating that waterquality conditions are not substantially improving, nor are they degrading, in relation to the LOCs. The concentrations of ammonia, nitrate, sulfate, chloride, and TDS tended to be below the LOC, and in cases where the trend was increasing (concentrations approached the LOC from below), the increases were varied and small in magnitude. In contrast, concentrations of TN and TP tended to be above the LOC, and where the trend was decreasing (concentrations approached the LOC from above), the decreases were larger in magnitude and more consistent. These results indicate that if water-quality conditions continue to trend in the same direction, at the same rate, for all sites and constituents studied, elevated concentrations are more likely to drop below an LOC before low concentrations will exceed an LOC.

Science of the Total Environment↗
USGS2019

Fate and transport of nitrapyrin in agroecosystems: Occurrence in agricultural soils, subsurface drains, and receiving streams in the Midwestern US

Nitrapyrin is a nitrification inhibitor that is co-applied with nitrogen fertilizer in agroecosystems. There is limited information on the fate of nitrapyrin after it is applied to agricultural soils. Over the course of one year (March 2016 to June 2017), 192 water samples from seven streams across Iowa and Illinois were analyzed for nitrapyrin, its metabolite 6‑chloropicolinic acid (6‑CPA), and three widely used herbicides acetochlor, atrazine , and metolachlor. Additional environmental samples were collected and analyzed in spring 2017: 63 water samples from eight subsurface drains in Illinois, and 33 soil samples from a field in Iowa that received direct application of nitrapyrin. Nitrapyrin was detected in all seven streams (56% detection) with concentrations ranging from less than LOD to 1200 ng/L; 6‑CPA was detected in six of the seven streams (13% detection) with concentrations ranging from less than LOD to 13 ng/L. Nitrapyrin was detected in 10% of the subsurface drain samples with concentrations ranging from less than LOD to 12 ng/L; 6‑CPA was detected in six of the eight subsurface drains and in 33% of drain samples with concentrations ranging from less than LOD to 6 ng/L. Nitrapyrin was detected in 67% of the soil samples collected, and concentrations ranged from less than LOD to 42 ng/g. Generally, all three herbicides were detected more frequently and at higher concentrations than nitrapyrin in the streams, subsurface drains, and soils. The environmental fate of nitrapyrin after application is dominated by sorption to soil and off-field transport via leaching and overland flow.

Illinois, Iowa↗
USGS2019

Point sources and agricultural practices control spatial-temporal patterns of orthophosphate in tributaries to Chesapeake Bay

Orthophosphate (PO 4 ) is the most bioavailable form of phosphorus (P). Excess PO 4 may cause harmful algal blooms in aquatic ecosystems. A major restoration effort is underway for Chesapeake Bay (CB) to reduce P, nitrogen, and sediment loading to CB. Although PO 4 cycling and delivery to streams has been characterized in small-scale studies, regional drivers of PO 4 patterns remain poorly understood because most water quality trend assessment focus on total P. Moreover, these trend assessments are usually at an annual timestep. To address this research gap, we analyzed PO 4 patterns over a 9-year period at 53 monitoring stations across the CB watershed to: 1) characterize the role of PO 4 in total P fluxes and trends; 2) describe spatial and temporal patterns of PO 4 concentrations across seasons and streamflow ; and 3) explore factors explaining these patterns. Agricultural watersheds exported the most total P compared with watersheds under different land uses (e.g., urban or forest), with PO 4 comprising up to 50% of those exports. Although PO 4 exports are declining at many sites, some agricultural regions are experiencing increasing trends at a rate sufficient to drive total P trends. Regression modeling results suggest that point source load reductions are likely responsible for decreasing PO 4 concentrations observed at many sites. Watersheds with more Conservation Reserve Program enrollment had lower summer PO 4 concentrations, highlighting the effectiveness of this practice. Manure inputs strongly predicted PO 4 concentrations at high flows across all seasons. Both manure applications and conservation tillage were correlated with changes in PO 4 concentrations at high flow, suggesting these activities could contribute to increasing PO 4 concentrations. This study highlights the effectiveness of point source control for reducing PO 4 exports and underscores the need for management strategies to target sources, practices, and landscape factors determining PO 4 loss from soils where manure inputs remain high.

Delaware, Maryland, New York, Pennsylvania, Virgin↗
USGS2019

Identification of conservation and restoration priority areas in the Danube River based on the multi-functionality of river-floodplain systems

Large river-floodplain systems are hotspots of biodiversity and ecosystem services but are also used for multiple human activities, making them one of the most threatened ecosystems worldwide. There is wide evidence that reconnecting river channels with their floodplains is an effective measure to increase their multi-functionality, i.e., ecological integrity, habitats for multiple species and the multiple functions and services of river-floodplain systems, although, the selection of promising sites for restoration projects can be a demanding task. In the case of the Danube River in Europe, planning and implementation of restoration projects is substantially hampered by the complexity and heterogeneity of the environmental problems, lack of data and strong differences in socio-economic conditions as well as inconsistencies in legislation related to river management. We take a quantitative approach based on best-available data to assess biodiversity using selected species and three ecosystem services (flood regulation, crop pollination , and recreation), focused on the navigable main stem of the Danube River and its floodplains. We spatially prioritize river-floodplain segments for conservation and restoration based on (1) multi-functionality related to biodiversity and ecosystem services, (2) availability of remaining semi-natural areas and (3) reversibility as it relates to multiple human activities (e.g. flood protection, hydropowerand navigation). Our approach can thus serve as a strategic planning tool for the Danube and provide a method for similar analyses in other large river-floodplain systems.

Danube River↗
USGS2019

Financing agricultural drought risk through ex-ante cash transfers

Despite advances in drought early warning systems, forecast information is rarely used for triggering and financing early actions, such as cash transfer. Scaling up cash transfer pay-outs , and overcoming the barriers to actions based on forecasts, requires an understanding of costs resulting from False Alarms, and the potential benefits associated with appropriate early interventions. On this study, we evaluate the potential cost-effectiveness of cash transfer responses, comparing the relative costs of ex-ante cash transfers during the maize growing season to ex-post cash transfers after harvesting in Kenya. For that, we developed a forecast model using Fast-and Frugal Trees that unravels early warning relationships between climate variability, vegetation coverage, and maize yields at multiple lead times. Results indicate that our models correctly forecast low maize yield events 85% of the time across the districts studied, some already six months before harvesting. The models’ performance improves towards the end of the growing season driven by a decrease of 39% in the probability of False Alarms. Overall, we show that timely cash transfers ex-ante to a disaster can often be more cost-effective than investing in ex-post expenditures. Our findings suggest that early response can yield significant cost savings, and can potentially increase the effectiveness of existing cash transfer systems.

Science of the Total Environment↗