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USGS2001

Major herbicides in ground water: Results from the National Water-Quality Assessment

To improve understanding of the factors affecting pesticide occurrence in ground water, patterns of detection were examined for selected herbicides, based primarily on results from the National Water-Quality Assessment (NAWQA) program. The NAWQA data were derived from 2227 sites (wells and springs) sampled in 20 major hydrologic basins across the USA from 1993 to 1995. Results are presented for six high-use herbicides—atrazine (2-chloro-4-ethylamino-6-isopropylamino- s -triazine), cyanazine (2-[4-chloro-6-ethylamino-1,3,5-triazin-2-yl]amino]-2-methylpropionitrile), simazine (2-chloro-4,6-bis[ethylamino]- s -triazine), alachlor (2-chloro- N -[2,6-diethylphenyl]- N -[methoxymethyl]acetamide), acetochlor (2-chloro- N -[ethoxymethyl]- N -[2-ethyl-6-methylphenyl]acetamide), and metolachlor (2-chloro- N -[2-ethyl-6-methylphenyl]- N -[2-methoxy-1-methylethyl]acetamide)— as well as for prometon (2,4-bis[isopropylamino]-6-methoxy- s -triazine), a nonagricultural herbicide detected frequently during the study. Concentrations were <1 μg L −1 at 98% of the sites with detections, but exceeded drinking-water criteria (for atrazine) at two sites. In urban areas, frequencies of detection (at or above 0.01 μg L −1 ) of atrazine, cyanazine, simazine, alachlor, and metolachlor in shallow ground water were positively correlated with their nonagricultural use nationwide ( P < 0.05). Among different agricultural areas, frequencies of detection were positively correlated with nearby agricultural use for atrazine, cyanazine, alachlor, and metolachlor, but not simazine. Multivariate analysis demonstrated that for these five herbicides, frequencies of detection beneath agricultural areas were positively correlated with their agricultural use and persistence in aerobic soil. Acetochlor, an agricultural herbicide first registered in 1994 for use in the USA, was detected in shallow ground water by 1995, consistent with previous field-scale studies indicating that some pesticides may be detected in ground water within 1 yr following application. The NAWQA results agreed closely with those from other multistate studies with similar designs.

Journal of Environmental Quality↗

USGS2002

Relating net nitrogen input in the Mississippi River Basin to nitrate flux in the Lower Mississippi River--A comparison of approaches

A quantitative understanding of the relationship between terrestrial N inputs and riverine N flux can help guide conservation, policy, and adaptive management efforts aimed at preserving or restoring water quality. The objective of this study was to compare recently published approaches for relating terrestrial N inputs to the Mississippi River basin (MRB) with measured nitrate flux in the lower Mississippi River. Nitrogen inputs to and outputs from the MRB (1951 to 1996) were estimated from state-level annual agricultural production statistics and NO y (inorganic oxides of N) deposition estimates for 20 states that comprise 90% of the MRB. A model with water yield and gross N inputs accounted for 85% of the variation in observed annual nitrate flux in the lower Mississippi River, from 1960 to 1998, but tended to underestimate high nitrate flux and overestimate low nitrate flux. A model that used water yield and net anthropogenic nitrogen inputs (NANI) accounted for 95% of the variation in riverine N flux. The NANI approach accounted for N harvested in crops and assumed that crop harvest in excess of the nutritional needs of the humans and livestock in the basin would be exported from the basin. The U.S. White House Committee on Natural Resources and Environment (CENR) developed a more comprehensive N budget that included estimates of ammonia volatilization, denitrification, and exchanges with soil organic matter. The residual N in the CENR budget was weakly and negatively correlated with observed riverine nitrate flux. The CENR estimates of soil N mineralization and immobilization suggested that there were large (2000 kg N ha −1 ) net losses of soil organic N between 1951 and 1996. When the CENR N budget was modified by assuming that soil organic N levels have been relatively constant after 1950, and ammonia volatilization losses are redeposited within the basin, the trend of residual N closely matched temporal variation in NANI and was positively correlated with riverine nitrate flux in the lower Mississippi River. Based on results from applying these three modeling approaches, we conclude that although the NANI approach does not address several processes that influence the N cycle, it appears to focus on the terms that can be estimated with reasonable certainty and that are correlated with riverine N flux.

Journal of Environmental Quality↗

USGS2021

Clothianidin decomposition in Missouri wetland soils

Neonicotinoid pesticides can persist in soils for extended time periods; however, they also have a high potential to contaminate ground and surface waters. Studies have reported negative effects associated with neonicotinoids and nontarget taxa, including aquatic invertebrates, pollinating insect species, and insectivorous birds. This study evaluated factors associated with clothianidin (CTN) degradation and sorption in Missouri wetland soils to assess the potential for wetland soils to mitigate potential environmental risks associated with neonicotinoids. Solid-to-solution partition coefficients ( K d ) for CTN sorption to eight wetland soils were determined via single-point sorption experiments, and sorption isotherm experiments were conducted using the two most contrasting soils. Clothianidin degradation was determined under oxic and anoxic conditions over 60 d. Degradation data were fit to zero- and first-order kinetic decay models to determine CTN half-life ( t 0.5 ). Sorption results indicated CTN sorption to wetland soil was relatively weak (average K d , 3.58 L kg –1 ); thus, CTN has the potential to be mobile and bioavailable within wetland soils. However, incubation results showed anoxic conditions significantly increased CTN degradation rates in wetland soils (anoxic average t 0.5 , 27.2 d; oxic average t 0.5 , 149.1 d). A significant negative correlation was observed between anoxic half-life values and soil organic C content ( r 2 = .782; p = .046). Greater CTN degradation rates in wetland soils under anoxic conditions suggest that managing wetlands to facilitate anoxic conditions could mitigate CTN presence in the environment and reduce exposure to nontarget organisms.

Missouri↗

USGS2021

Phosphorus sources, forms, and abundance as a function of streamflow and field conditions in a Maumee River tributary, 2016-2019

Total phosphorus (TP), dissolved P (DP), and suspended sediment (SS) were sampled in Black Creek, Indiana, monthly during base flow and for 100 storm events during water years 2016–2019, enabling analysis of how each of these varied as a function of streamflow and field conditions at nested edge-of-field sites. Particulate P was normalized for SS (P SS = [TP − DP]/SS). Streamflow events were differentiated by maximum TP concentrations co-occurring with maximum SS (SED) or DP (SOL). The combination of new precipitation and high antecedent soil-water storage during months when fields were exposed coincided with higher streamflow that drove SED events. These SED events carried more SS, including sediment eroded from streambanks that added sediment P but also may have provided for sorption of DP. During SOL events, DP was higher and contributed approximately half of TP; SS was lower. These SOL events had higher P SS , more similar to that in base flow as well as composited samples of overland flow and tile-drain discharge from fields. Base-flow samples had significantly higher P SS concentrations than most event samples, with ≤25 times enrichment relative to soil P concentrations in fine-grained source material. Combining base-flow and event samples showed that P SS integrates SS, DP, and streamflow. Addition of new suspended sediment during events may provide for sorption of DP during and after events and storage in the system, delaying delivery of this P to Lake Erie relative to what would be expected for the dissolved form but adding to the legacy P stored in the stream system.

Indiana↗

USGS2022

Fate and seasonality of antimicrobial resistance genes during full-scale anaerobic digestion of cattle manure across seven livestock production facilities

Anaerobic digestion has been suggested as an intervention to attenuate antibiotic resistance genes (ARGs) in livestock manure but supporting data have typically been collected at laboratory scale. Few studies have quantified ARG fate during full-scale digestion of livestock manure. We sampled untreated manure and digestate from seven full-scale mesophilic dairy manure digesters to assess ARG fate through each system. Samples were collected biweekly from December through August (i.e., winter, spring, and summer; n = 235 total) and analyzed by quantitative polymerase chain reaction for intI1 , erm (B), sul1 , tet (A), and tet (W). Concentrations of intI1 , sul1 , and tet (A) decreased during anaerobic digestion, but their removal was less extensive than expected based on previous laboratory studies. Removal for intI1 during anaerobic digestion equaled 0.28 ± 0.03 log 10 units (mean ± SE), equivalent to only 48% removal and notable given intI1 ’s role in horizontal gene transfer and multiple resistance. Furthermore, tet (W) concentrations were unchanged during anaerobic digestion ( p > 0.05), and erm (B) concentrations increased by 0.52 ± 0.03 log 10 units (3.3-fold), which is important given erythromycin's status as a critically important antibiotic for human medicine. Seasonal log 10 changes in intI1 , sul1 , and tet (A) concentrations were ≥50% of corresponding log 10 removals by anaerobic digestion, and variation in ARG and intI1 concentrations among digesters was quantitatively comparable to anaerobic digestion effects. These results suggest that mesophilic anaerobic digestion may be limited as an intervention for ARGs in livestock manure and emphasize the need for multiple farm-level interventions to attenuate antibiotic resistance.

Journal of Environmental Quality↗

USGS2022

Vegetative buffer strips show limited effectiveness for reducing antibiotic transport in surface runoff

Vegetative buffer strips (VBS) have been demonstrated to effectively reduce loads of sediment, nutrients, and herbicides in surface runoff, but their effectiveness for reducing veterinary antibiotic (VA) loads in runoff has not been well documented. The objective of this study was to determine the effectiveness of VBS vegetation and width on surface runoff loads of the VAs sulfamethazine (SMZ) and lincomycin (LIN). Experimental design of the plots (1.5 × 25 m) was a two-way factorial with four vegetation treatments (tall fescue [ Festuca aruninacea Schreb.]; tall fescue with switchgrass [ Panicum virgatum L.] hedge; warm-season native grass mix; and continuous fallow control), and four buffer widths (0, 2, 5, and 9 m). Turkey litter spiked with SMZ and LIN was applied to the source area (upper 7 m) of each plot, and runoff was collected at each width. Runoff was generated with a rotating boom simulator. Results showed VA loads in runoff at the 0-m sampler ranged from 3.8 to 5.9% of applied, and overall VA transport in runoff was predominately in the dissolved phase (90% for SMZ and 99% for LIN). Among vegetation treatments, only tall fescue significantly reduced loads of SMZ and LIN compared with the control, with load reductions of ∼30% for both VAs. Estimated field-scale reductions in VA loads showed that source-to-buffer area ratios (SBARs) of 10:1 to 20:1 reduced VA loads by only 7 to 16%. Overall, the grass VBS tested here were less effective at reducing SMZ and LIN loads in surface runoff than has been previously demonstrated for sediment, nutrients, and herbicides.

Journal of Environmental Quality↗

USGS2023

Microbial source tracking and land use associations for antibiotic resistance genes in private wells influenced by human and livestock fecal sources

Antimicrobial resistance is a growing public health problem that requires an integrated approach among human, agricultural, and environmental sectors. However, few studies address all three components simultaneously. We investigated the occurrence of five antibiotic resistance genes (ARGs) and the class 1 integron gene ( intI1 ) in private wells drawing water from a vulnerable aquifer influenced by residential septic systems and land-applied dairy manure. Samples ( n = 138) were collected across four seasons from a randomized sample of private wells in Kewaunee County, Wisconsin. Measurements of ARGs and intI1 were related to microbial source tracking (MST) markers specific to human and bovine feces; they were also related to 54 risk factors for contamination representing land use, rainfall, hydrogeology, and well construction. ARGs and intI1 occurred in 5–40% of samples depending on target. Detection frequencies for ARGs and intI1 were lowest in the absence of human and bovine MST markers (1-30%), highest when co-occurring with human and bovine markers together (11-78%), and intermediate when co-occurring with just one type of MST marker (4-46%). Gene targets were associated with septic system density more often than agricultural land, potentially because of the variable presence of manure on the landscape. Determining ARG prevalence in a rural setting with mixed land use allowed an assessment of the relative contribution of human and bovine fecal sources. Because fecal sources co-occurred with ARGs at similar rates, interventions intended to reduce ARG occurrence may be most effective if both sources are considered.

Wisconsin↗

USGS2024

Influence of irrigation water and soil on annual mercury dynamics in Sacramento Valley rice fields

Methylmercury (MeHg) is a human and environmental toxin produced in flooded soils. Little is known about MeHg in rice ( Oryza Sativa L.) fields in Sacramento Valley, California. The objectives of this study were to quantify mercury fractions in irrigation water and within rice fields and to determine their mercury pools in surface water, soil, and grain. Soil, grain, and surface water (dissolved and particulate) MeHg and total mercury (THg) were monitored in six commercial rice fields throughout a winter fallow season and subsequent growing season. Both dissolved and particulate mercury fractions were higher in fallow season rice field water. Total suspended solids and particulate mercury concentrations were positively correlated ( r = 0.99 and 0.98 for THg and MeHg, respectively), suggesting that soil MeHg was suspended in the water column and potentially exported. Dissolved THg and MeHg concentrations were positively correlated with absorbance at 254 nm ( r = 0.47 and 0.58, respectively) in fallow season field water. In the growing season, fields with higher irrigation water MeHg concentrations (due to recycled water use) had elevated field-water MeHg ( r = 0.86) and grain MeHg concentrations ( r = 0.96). Based on a mass balance analysis, soil mercury pools were orders of magnitude larger than surface water or grain mercury pools; however, fallow season drainage and grain harvest were the primary pathways for MeHg export. Based on these findings, reducing (1) discharge when water is turbid, (2) straw inputs, and (3) use of recycled irrigation water could help reduce mercury exports in rice field drainage water.

California↗

USGS2024

The LTAR Grazing Land Common Experiment at the Jornada Experimental Range: Old genetics, new precision technologies, and adaptive value chains

Rangelands and the supply chains connected to them are central to the agrifood systems of the Southwestern United States. Local ranchers are simultaneously arid lands managers, herd managers, and marketing managers. To stay in business, they must constantly adapt to unpredictable forage resources and markets while conserving soils and vegetation resources for the long term. As climate warming and drying exacerbate the complexity and difficulty of day-to-day production, producers and policy-makers are seeking alternatives to “business as usual”. To meet this need, the LTAR-Jornada team has developed a package of strategies to help producers adapt to the local and inter-regional challenges. The package includes heritage cattle, precision ranching systems, and adaptive value chains. Five ranches across the Southwest have adopted different combinations of the strategies and are partnering to measure their benefits and drawbacks in real-world conditions. Opportunities for controlled experimentation differ among the ranches, so we use LTAR’s indicator system to assess and compare results. Even as we invest in co-producing knowledge about these three strategies, we recognize that progressive aridification and urbanization of Southwestern rangelands create challenges for which a single “silver bullet” agricultural innovation is unlikely to provide durable solutions. We are learning from our customers and stakeholders about ways to adjust the development of new options.

New Mexico↗

USGS2025

Exploring management and environment effects on edge-of-field phosphorus losses with linear mixed models

Evaluating how weather, farm management, and soil conditions impact phosphorus (P) loss from agricultural sites is essential for improving our waterways in agricultural watersheds. In this study, rainfall characteristics, manure application timing, tillage, surface condition, and soil test phosphorus (STP) were analyzed to determine their effects on total phosphorus (TP) and dissolved phosphorus (DP) loss using 125 site-years of runoff data collected by the University of Wisconsin Discovery Farms and Discovery Farms Minnesota. Three linear mixed models (LMMs) were then used to evaluate the influence of those factors on TP and DP losses: (1) a model that included all runoff events, (2) manured sites only, and (3) precipitation events only. Results show that the timing of manure application relative to the timing of a runoff event only had a marginal association with P loads and concentrations, although the majority of the runoff events were collected after 10 days of manure application. Tillage was as influential factor, with greater DP loads and concentrations associated with no-till, especially during frozen conditions. Fields in this study had high STP values, but the model results only showed positive associations between DP load and DP flow-weighted mean concentration (FWMC) loss at the 0- to 15-cm depth. The precipitation event LMM (which included precipitation characteristics) was the model that resulted in the largest R 2 value. While the predictive capacity of the LMMs was low, they did illuminate the relative importance of management and environmental variables on P loss, and can be used to guide future research on P loss in this region.

Minnesota, Wisconsin↗

USGS2025

Optimizing sampling across transect-based methods improves the power of agroecological monitoring data

Transect-based monitoring has long been a valuable tool in ecosystem monitoring to measure multiple ecosystem attributes. The line-point intercept (LPI), vegetation height, and canopy gap intercept methods comprise a set of core methods, which provide indicators of ecosystem condition. However, users often struggle to design a sampling strategy that optimizes the ability to detect ecological change using transect-based methods. We assessed the sensitivity of each of these core methods to transect length, number, and sampling interval in 1-ha plots to determine: (1) minimum sampling required to describe ecosystem characteristics and detect change; and (2) optimal transect length and number to make recommendations for future analyses and monitoring efforts. We used data from 13 National Wind Erosion Research Network locations, including five LTAR sites, spanning the western United States, which included 151 plot sampling events over time across five biomes. We found that longer and increased replicates of transects were more important for reducing sampling error than increased sample intensity along fewer transects per plot. For all methods and indicators across biomes plots, three 100-m transects reduced sampling error such that indicator estimates fell within a 95% confidence interval of ±5% for canopy gap intercept and LPI-total foliar cover, ±5 cm for height, and ±2 species for LPI-species counts. For the same criteria at 80% confidence intervals, two 100-m transects are needed. Site-scale inference was strongly affected by sample design, consequently our understanding of ecological dynamics may be influenced by sampling decisions.

western United States↗

USGS2025

Satellite assessment of winter cover crop and conservation tillage outcomes to support adaptive management in working landscapes

The use of winter cover crops and conservation tillage are agricultural practices promoted to reduce nutrient and sediment loss from cropland, improve soil health, increase infiltration, and support farm nutrient cycling and ecosystem services. However, environmental performance of these practices is variable in the working farm landscape. The Lower Chesapeake Bay research project within the USDA Long-Term Agroecosystem Research (LTAR) network has collaboratively developed satellite remote sensing algorithms to measure the performance and phenology of winter cover crops (aboveground biomass, nitrogen content, fractional cover, and emergence and termination dates) using no-cost Harmonized Landsat and Sentinel-2 multispectral satellite imagery. This research supports annual operational assessment of >28,000 fields per year in four states. Results document the impacts of agronomic management on conservation outcomes, support adaptive management of incentive payment structures, and can reduce the workload for conservation district staff by remotely verifying cover crop management. Additionally, super-spectral satellite applications have been developed to accurately map crop residue cover by measuring lignocellulose absorption in shortwave infrared wavelengths, producing a 7-year time series of tillage intensity maps for the Delmarva Peninsula. These remote sensing products can be used in decision support and modeling to estimate changes in nutrient, sediment, and carbon cycling resulting from conservation practice implementation in the working farm landscape. This manuscript provides an overview of remote sensing research findings and applications associated with the USDA LTAR and Conservation Effects Assessment Projects (CEAP), documenting a variety of previously published outcomes with update and expansion of techniques using additional unpublished data and analyses as appropriate.

Maryland↗

USGS2025

Assessing the topographic distribution of legacy soil phosphorus in agricultural fields of the Delmarva Peninsula, Mid-Atlantic Coastal Plain, USA

Phosphorus (P) management remains a challenge in agricultural watersheds. The Choptank River Conservation Effects Assessment Project watershed, located in Maryland and Delaware and draining to the Chesapeake Bay, contains legacy soil P from historical dairy and poultry manure applications. These practices elevated soil P beyond crop needs, contributing to persistent P export to aquatic ecosystems. We assessed spatial P distribution and analyzed GIS (Geographic Information Systems)-derived landscape features driving legacy P movement on a farm (47 ha). We hypothesized that P accumulates in drained lowlands and depressional areas due to gravity-driven processes that accelerate P-enriched water to receiving waters via overland flow. In collaboration with the US Department of Agriculture Legacy P project, we collected 105 soil samples (0- to 5-cm and 5- to 15-cm depths) and 14 ditch sediment samples across five topographic openness classes from a farm with >100 years of dairy manure application. Average Mehlich-III P concentrations were 218 and 179 mg kg −1 at 0- to 5-cm and 5- to 15-cm depths, respectively, with legacy areas defined by P content > 100 mg kg −1 . Soil P and clay particle size were positively correlated ( r = 0.42, p < 0.05), increased as landscape openness decreased, and were negatively correlated with topographic openness (ranging from −0.2 to −0.4, p < 0.05), indicating accumulation of P and clay in low-lying areas. These patterns suggest that historical field-level managements have primarily shaped P distribution, while hydrologic and landscape properties further influence its redistribution via transport pathways and drainage. These findings support the development of landscape models to map critical source areas in low-relief watersheds and guide targeted mitigation in high-risk P export zones.

Maryland↗

USGS2026

Quantitative microbial risk assessment with microbial source tracking for enteric pathogens in southwest Wisconsin private wells

Private wells supply drinking water for many households, and their contamination by fecal microbes presents a risk of acute gastrointestinal illness (AGI). Risk is thought to vary by contaminating fecal source, but specific associations with fecal source are unknown for most private wells in the United States. This study characterizes AGI risk in Grant, Iowa, and Lafayette counties in southwestern Wisconsin. AGI risk was assessed for 10 viral, bacterial, and protozoan pathogens detected in private wells using quantitative microbial risk assessment. Exposure assessment was based on sampling 138 private wells in the study area, and risk was associated with fecal source by microbial source tracking (MST). Median Monte Carlo estimates indicated 4450 AGI cases/year in the study area associated with drinking water from contaminated private wells (95% confidence interval: 90–37,990). Most annual cases were associated with detection of human MST markers, including median estimates of 2550 associated with only human markers and 880 with human and livestock MST markers detected together. Note that 50 AGI cases/year were associated with detection of only livestock markers, and nearly 1000 cases were estimated to occur in the absence of detectable MST markers. This study characterizes AGI risk for households served by private wells in southwestern Wisconsin. It illustrates that human fecal sources can predominate risk associated with drinking water from private wells, even in a rural region characterized by substantial agricultural activity. MST can characterize the relationship between risk and fecal source; contributions of fecal sources to risk cannot be assumed from land use.

Wisconsin↗

USGS1981

Influence of PCBs in water on uptake and elimination of DDT and DDE by lake trout

Researchers predicted that several hundred years would be required before DDT (1,1,1 trichloro-2,2-bis [P-chlorophyl] ethane) and its metabolites were likely to decrease to nondetectable levels in Lake Michigan. But following the ban on DDT in 1970, residues of total DDT in Lake Michigan lake trout ( Salvelinus namaycush ) declined rapidly from 10.5 µ g/g in 1970 to 5.7 µ g/g in 1976. During this period, polychlorinated biphenyls (PCBs) were being detected in lake trout tissues at about 20 µ g/g. It was hypothesized that the high level of PCBs being accumulated by fish may have influenced uptake and elimination of DDT and DDE (1,1-dichloro-2,2-bis [ p -chlorophenyl] ethylene) by fish. To test this hyphophesis, fingeriing lake trout were exposed to various combinations of DDT, DDE (100 ng/liter), and PCBs (100 and 500 ng/liter) in water for 12 weeks. After DDT and DDe exposures were completed, exposure to PCBs was continued for an additional 16 weeks to measure any effect PCBs may have on the elimination of DDT and DDE by fish. Accumulation and elimination rates of DDT and DDE were compared. It was found that PCBs did not influence the accumulation or elimination rates of DDT or DDE in lake trout and therefore should not have had a major influence on the decline of DDT in lake trout.

Journal of Environmental Quality↗

USGS1982

Acid rain, air pollution, and tree growth in southeastern New York

Whether dendroecological analyses could be used to detect changes in the relationship of tree growth to climate that might have resulted from chronic exposure to components of the acid rain-air pollution complex was determined. Tree-ring indices of white pine ( Pinus strobus L.), eastern hemlock ( Tsuga canadensis (L.) Cart.), pitch pine ( Pinus rigida Mill.), and chestnut oak ( Quercus prinus L.) were regressed against orthogonally transformed values of temperature and precipitation in order to derive a response-function relationship. Results of the regression analyses for three time periods, 1901–1920, 1926–1945, and 1954–1973 suggest that the relationship of tree growth to climate has been altered. Statistical tests of the temperature and precipitation data suggest that this change was nonclimatic. Temporally, the shift in growth response appears to correspond with the suspected increase in acid rain and air pollution in the Shawangunk Mountain area of southeastern New York in the early 1950's. This change could be the result of physiological stress induced by components of the acid rain-air pollution complex, causing climatic conditions to be more limiting to tree growth.

New York↗

USGS1982

Heavy metal concentrations in earthworms from soil amended with sewage sludge

Metal concentrations in soil may be elevated considerably when metal‐laden sewage sludge is spread on land. Metals in earthworms ( Lumbricidae ) from agricultural fields amended with sewage sludge and from experimental plots were examined to determine if earthworms are important in transferring metals in soil to wildlife. Earthworms from four sites amended with sludge contained significantly ( P < 0.05) more Cd (12 times), Cu (2.4 times), Zn (2.0 times), and Pb (1.2 times) than did earthworms from control sites, but the concentrations detected varied greatly and depended on the particular sludge application. Generally, Cd and Zn were concentrated by earthworms relative to soil, and Cu, Pb, and Ni were not concentrated. Concentrations of Cd, Zn, Cu, and Pb in earthworms were correlated ( P < 0.05) with those in soil. The ratio of the concentration of metals in earthworms to the concentration of metals in soil tended to be lower in contaminated soil than in clean soil. Concentrations of Cd as high as 100 ppm (dry wt) were detected in earthworms from soil containing only 2 ppm Cd. These concentrations are considered hazardous to wildlife that eat worms. Liming soil decreased Cd concentrations in earthworms slightly ( P < 0.05) but had no discernible effect on concentrations of the other metals studied. High Zn concentrations in soil substantially reduced Cd concentrations in earthworms.

Pennsylvania↗

USGS1984

Contamination of the O2 soil horizon by zinc smelting and its effect on woodlouse survival

Samples of litter from the O2 horizon of Dekalb soil (loamy-skeletal, mixed, mesic Typic Dystrochrept) were collected from 18 ridgetop sites on a transect that ran by two Zn smelters in Palmerton, Pa. Metal concentrations increased by regular gradations from a minimum at a site 105 km west of the smelters (67 mg/kg Zn, 0.85 mg/kg Cd, 150 mg/kg Pb, 11 mg/kg Cu) to a maximum 1.2 km east of the smelters (35 000 mg/kg Zn, 1300 mg/kg Cd, 3200 mg/kg Pb, 280 mg/kg Cu), and then decreased until they reached an eastern minimum at the easternmost site, 19 km from the smelters. An increase in the P concentrations near the smelters showed that the emissions were disrupting nutrient flow through the ecosystem. An increase in the pH near the smelters was attributed to the high concentrations of Zn. The log of the distance of the sites from the smelters was significantly correlated ( r = −0.80, p < 0.05) with the mortality of woodlice ( Porcellio scaber Latreille) fed samples of the litter during an 8-week test. There was substantial mortality of woodlice observed even in the O2 litter collected 19 km east of the smelters. Zinc, cadmium, lead, copper, and sulfur were experimentally added, alone or in combination, to O2 litter collected far from any known source of metal emissions. The highest concentration of Zn added (20 000 mg/kg) was toxic enough to account for the mortality observed in the earlier test. A lower concentration of Zn (5000 mg/kg) as well as the concentration of Cd (500 mg/kg) tested also significantly ( p < 0.05) increased the mortality of woodlice.

Journal of Environmental Quality↗