Atrazine promotes biochemical changes and DNA damage in a Neotropical fish species

The effects of Atrazine, an herbicide used worldwide and considered as a potential contaminant in aquatic environments, were assessed on the Neotropical fish Prochilodus lineatus acutely (24 and 48 h) exposed to 2 or 10 μg L⁻¹ of atrazine by using a set of biochemical and genetic biomarkers. The following parameters were measured in the liver: activity of the biotransformation enzymes ethoxyresorufin-O-deethylase (EROD) and glutathione S transferase (GST), antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), content of reduced glutathione (GSH), generation of reactive oxygen species (ROS) and occurrence of lipid peroxidation (LPO); in brain and muscle the activity of acetylcholinesterase (AChE) and DNA damage (comet assay) on erythrocytes, gills and liver cells. A general decreasing trend on the biotransformation and antioxidant enzymes was observed in the liver of P. lineatus exposed to atrazine; except for GR, all the other antioxidant enzymes (SOD, CAT and GPx) and biotransformation enzymes (EROD and GST) showed inhibited activity. Changes in muscle or brain AChE were not detected. DNA damage was observed in the different cell types of fish exposed to the herbicide, and it was probably not from oxidative origin, since no increase in ROS generation and LPO was detected in the liver. These results show that atrazine behaves as enzyme inhibitor, impairing hepatic metabolism, and produces genotoxic damage to different cell types of P. lineatus.     

Developmental exposure to diuron causes splenotoxicity in male Sprague-Dawley rat pups

This study investigated whether perinatal exposure to diuron [3-(3,4-dichlorophenyl)-1-1-dimethylurea] might exert adverse effects on rat lymphoid organs. Pregnant Sprague-Dawley (SD) rats were exposed to diuron at 500, 750 or 1250 ppm in the diet from gestational days (GD) 12-21 and during lactation. At postnatal day (PND) 42, male pups were euthanized and thymus, spleen, mesenteric lymph node and femur were collected for histopathological analysis. Food consumption and body weight gain were significantly reduced in dams exposed to 1250 ppm during gestation period. Also, Diuron at 750 and 1250 ppm produced: (1) increased relative spleen weight associated histologically with severe congestion in red pulp, (2) enhanced extramedullary hematopoiesis and hemosiderosis as well as (3) depletion of lymphoid follicles in white pulp. Flow cytometric analysis revealed a significant reduction in B lymphocytes (CD45RA+) in male pups but T lymphocytes (CD4+, CD8+ and CD4+/CD8+) were not markedly affected. Thus, data suggest that Diuron-induced maternal toxicity in dams exposed to high dose and perinatal exposure to this herbicide produced spleen toxicity as evidenced by a reduction in B lymphocyte number in male SD pups.     

Agricultural pesticide residues of farm runoff in the Okanagan Valley, British Columbia, Canada

The objectives of this study were to determine environmental occurrence and concentrations of selected currently-used-pesticides and some transformation products in agricultural farms in the Okanagan Valley (OKV), and to conduct a simple risk assessment of environmental pesticides levels detected in OKV on non-target aquatic organisms. The OKV is the tree fruit country of the Province of British Columbia where considerable amount of pesticides are applied annually. Water, sediment and soil samples were collected at eleven sites in early June and late September following rainfall events and/or extended periods of irrigation from drainage ditches and/or from small streams. Undisturbed reference sites were also sampled. Study results showed that forty of the eighty chemicals analyzed, including organochlorine, nitrogen-containing and organophosphate pesticides commonly used for OKV crops, were detected in runoff and small stream water samples. Among which, endosulfan-sulfate was the most frequently detected chemical. Also, azinophos-methyl (0.699-25.5 ng/L), diazinon (0.088-214 ng/L) exceeded, and α-, β- endosulfan, endosulfan sulphate approached the guidelines for the protection of aquatic life.     

Climate change impacts on the leaching of a heavy metal contamination in a small lowland catchment

The Keersop catchment (43km(2)) in the south of The Netherlands has been contaminated by the emissions of four zinc ore smelters. The objective of this study was to assess the effects of future projected climate change on the hydrology and the leaching of heavy metals (i.e. Cd and Zn) in the catchment. The numerical, quasi-2D, unsaturated zone Soil Water Atmosphere Plant model was used with 100-year simulated daily time series of precipitation and potential evapotranspiration. The time series are representative of stationary climates for the periods 1961-1990 ("baseline") and 2071-2100 ("future"). The time series of future climate were obtained by downscaling the results of eight regional climate model (RCM) experiments, driven by the SRES A2 emissions scenario, using change factors for a series of climate statistics and applying them to stochastic weather generator models. The time series are characterized by increased precipitation in winter, less precipitation in summer, and higher air temperatures (between 2°C and 5°C) throughout the year. Future climate scenarios project higher evapotranspiration rates, more irrigation, less drainage, lower discharge rates and lower groundwater levels, due to increased evapotranspiration and a slowing down of the groundwater system. As a result, lower concentrations of Cd and Zn in surface water are projected. The reduced leaching of heavy metals, due to drying of the catchment, showed a positive impact on a limited aspect of surface water quality.     

Metal stress and decreased tree growth in response to biosolids application in greenhouse seedlings and in situ Douglas-fir stands

To assess physiological impacts of biosolids on trees, metal contaminants and phytochelatins were measured in Douglas-fir stands amended with biosolids in 1982. A subsequent greenhouse study compared these same soils to soils amended with fresh wastewater treatment plant biosolids. Biosolids-amended field soils had significantly higher organic matter, lower pH, and elevated metals even after 25 years. In the field study, no beneficial growth effects were detected in biosolids-amended stands and in the greenhouse study both fresh and historic biosolids amendments resulted in lower seedling growth rates. Phytochelatins - bioindicators of intracellular metal stress - were elevated in foliage of biosolids-amended stands, and significantly higher in roots of seedlings grown with fresh biosolids. These results demonstrate that biosolids amendments have short- and long-term negative effects that may counteract the expected tree growth benefits.     

Toxicity persistence in runoff and soil from experimental soybean plots following insecticide applications

Persistence of toxicity in runoff water and soil was investigated in experimental soybean plots subjected to successive runoff events following pesticide application. Runoff events were produced by irrigation using a sprinkler system. The pesticides applied were cypermethrin and endosulfan, which are widely used in soy production in Argentina. Toxicity tests were performed on two abundant components of the regional fauna, the amphipod Hyalella curvispina and the fish Cnesterodon decemmaculatus. Runoffs from two pesticide applications were assayed at different stages of the growing season: an early application when the soil was almost bare and a late one close to harvest, when the ground was covered by vegetation and just before soy leaves fell. Toxicity to H. curvispina in runoff ceased almost one month after the early application of the two pesticides, while it persisted for over three months after the late application. Soil toxicity to H. curvispina and runoff toxicity to C. decemmaculatus followed the same pattern. Higher temperatures and solar radiation are likely to have enhanced insecticide degradation after the early application. Lower temperatures and solar radiation in combination with increased organic matter from litter probably contributed to the longer persistence of toxicity recorded after the late application, as compared with the early application. Cypermethrin caused no mortality to C. decemmaculatus after the early application, while endosulfan toxicity persisted for almost four months after the late one.     

PCE dissolution and simultaneous dechlorination by nanoscale zero-valent iron particles in a DNAPL source zone

While the capability of nanoscale zero-valent iron (NZVI) to dechlorinate organic compounds in aqueous solutions has been demonstrated, the ability of NZVI to remove dense non-aqueous phase liquid (DNAPL) from source zones under flow-through conditions similar to a field scale application has not yet been thoroughly investigated. To gain insight on simultaneous DNAPL dissolution and NZVI-mediated dechlorination reactions after direct placement of NZVI into a DNAPL source zone, a combined experimental and modeling study was performed. First, a DNAPL tetrachloroethene (PCE) source zone with emplaced NZVI was built inside a small custom-made flow cell and the effluent PCE and dechlorination byproducts were monitored over time. Second, a model for rate-limited DNAPL dissolution and NZVI-mediated dechlorination of PCE to its three main reaction byproducts with a possibility for partitioning of these byproducts back into the DNAPL was formulated. The coupled processes occurring in the flow cell were simulated and analyzed using a detailed three-dimensional numerical model. It was found that subsurface emplacement of NZVI did not markedly accelerate DNAPL dissolution or the DNAPL mass-depletion rate, when NZVI at a particle concentration of 10g/L was directly emplaced in the DNAPL source zone. To react with NZVI the DNAPL PCE must first dissolve into the groundwater and the rate of dissolution controls the longevity of the DNAPL source. The modeling study further indicated that faster reacting particles would decrease aqueous contaminant concentrations but there is a limit to how much the mass removal rate can be increased by increasing the dechlorination reaction rate. To ensure reduction of aqueous contaminant concentrations, remediation of DNAPL contaminants with NZVI should include emplacement in a capture zone down-gradient of the DNAPL source.     

Bacterial community profiles from sediments of the Anacostia River using metabolic and molecular analyses

Background aim and scope  

Though the tidal Anacostia River, a highly polluted riverine system, has been well characterized with regard to contaminants, its overall resident bacterial populations have remained largely unknown. Improving the health of this system will rely upon enhanced understanding of the diversity and functions of these communities. Bacterial DNA was extracted from archived (AR, year 2000) and fresh sediments (RE, year 2006) collected from various locations within the Anacostia River. Using a combination of metabolic and molecular techniques, community snapshots of sediment bacterial diversity and activity were produced.     

Simultaneous immobilization of metals and arsenic in acidic polluted soils near a copper smelter in central Chile

Introduction  

Acidic and metal(oid)-rich topsoils resulted after 34 years of continuous operations of a copper smelter in the Puchuncaví valley, central Chile. Currently, large-scale remediation actions for simultaneous in situ immobilization of metals and As are needed to reduce environmental risks of polluted soils. Aided phytostabilization is a cost-effective alternative, but adequate local available soil amendments have to be identified and management options have to be defined.