Large-scale spatiotemporal variations, sources, and risk assessment of banned OCPs and PAHs in suspended particulate matter from the Negro river, Argentina.

Organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) threaten the environment due to their wide environmental resistance. Environmental paradigms coexist along the Negro River (NR) in Argentina, South America, which flows to the sea below the latitude of 40o S; however, this is the first environmental assessment of OCPs and PAHs in water of the NR for more than 15 years. With 21 sampling sites covering a range of 600 km of river extension, we assessed 16 OCPs and 16 PAHs in suspended particulate material (SPM) with regard to their levels, seasonality, sources, and potential biological risk assessment. Using gas chromatography-mass spectrometry and gas chromatography coupled with electron capture detection, we found an overall mean value for Σ16 OCPs of 648.56 ng. g-1, d.w. Despite a ban spanning 25 years, an increasing trend of accumulation of hexachlorocyclohexanes (HCHs) and endosulfan was shown in the lower valley. The ɑ-HCH/ɤ-HCH and ß-HCH/(ɑ + É¤)-HCH ratios indicated a prevalent usage of technical HCH over lindane and recent HCH inputs. The most abundant compound, α-endosulfan, averaged 141.64 ng. g-1, d.w. and DDX (Σ 4,4'-DDE, 4,4'-DDD, and 4,4'-DDT) averaged 99.98 ng. g-1, d.w. Winter OCP loads in the NR reflected the runoff of the heaviest pesticide application period. We estimated the total discharge of DDT into the Atlantic ocean was 96 g.day-1, added to 458 g of HCHs and 257 g of endosulfans (ɑ + ß + epoxide) adsorbed by the SPM. PAHs occurred widely along the river (38.83 ± 43.52 µg. g-1) and the highest levels coincided with locations with marked anthropogenic-related activity, such as petroleum/gas exploitation facilities. Risk quotient analysis showed a low risk posed by OCPs, but a high risk of potential effects on biota posed by the PAHs, highlighting the need for mitigation measures.

Effects of multiple stressors associated with agriculture on stream macroinvertebrate communities in a tropical catchment.

Tropical forests are declining at unprecedented rates in favour of agriculture, and streams can be severely impacted due to effects of multiple stressors that have rarely been considered together in tropical studies. We studied the effects of multiple stressors associated with agricultural practices (pesticide toxicity, nutrient enrichment and habitat alteration-quantified as TUmax, soluble reactive phosphorus concentration and sedimentation, respectively) on macroinvertebrate communities in a tropical catchment in Panama (13 stream sites sampled in 20 occasions from 2015 to 2017, with 260 samples in total). We examined how macroinvertebrate abundance, taxonomic richness, community composition and biotic indices (SPEAR and BMWP/PAN, which were specifically designed to detect pesticide toxicity and nutrient enrichment, respectively) varied depending on the studied stressors, considering their single and combined effects. Our analyses revealed significant effects of the studied stressors on macroinvertebrate communities, with two particular results that merit further attention: (1) the fact that pesticide toxicity affected BMWP/PAN, but not SPEAR, possibly because the former had been adapted for local fauna; and (2) that most stressors showed antagonistic interactions (i.e., lower combined effects than expected from their individual effects). These results highlight the need for toxicity bioassays with tropical species that allow adaptations of biotic indices, and of observational and manipulative studies exploring the combined effects of multiple stressors on tropical macroinvertebrate communities and ecosystems, in order to predict and manage future anthropogenic impacts on tropical streams.

Disentangling natural and anthropogenic influences on Patagonian pond water quality.

The water quality of wetlands is governed not only by natural variability in hydrology and other factors, but also by anthropogenic activities. Patagonia is a vast sparsely-populated in which ponds are a key component of rural and urban landscapes because they provide several ecosystem services such as habitat for wildlife and watering for livestock. Integrating field-based and geospatial data of 109 ponds sampled across the region, we identified spatial trends and assessed the effects of anthropogenic and natural factors in pond water quality. The studied ponds were generally shallow, well oxygenated, with maximum nutrient values reported in sites used for livestock breeding. TN:TP ratio values were lower than 14 in >90% of the ponds, indicating nitrogen limitation. Water conductivity decreased from de east to the west, meanwhile pH and dissolved oxygen varied associated with the latitude. To assess Patagonian ponds water status we recommend the measure of total suspended solids and total nitrogen in the water, and evaluate the mallín (wetland vegetation) coverage in a 100m radius from the pond, since those features were significantly influenced by livestock land use. To evaluate the relative importance of natural variability and anthropogenic influences as driving factors of water quality we performed three generalized linear models (GLM) that encompassed the hydrology, hydroperiod and biome (to represent natural influences), and land use (to represent anthropogenic influences) as fixed effects. Our results revealed that at the Patagonian scale, ponds water quality would be strongly dependent on natural gradients. We synthetized spatial patterns of Patagonian pond water quality, and disentangled natural and anthropic factors finding that the dominant environmental influence is rainfall gradient.

The impact of pesticides on the macroinvertebrate community in the water channels of the Río Negro and Neuquén Valley, North Patagonia (Argentina).

Agriculture represents the second most important economic activity in the North Patagonian Region of Argentina and non-selective insecticides are still being used with significant implications to the quality of the environment. The range of concentrations (µg/L) determined for azinphosmethyl, chlorpyrifos, and carbaryl in drainage channels were from non-detected to 1.02, 1.45, and 11.21, respectively. Macroinvertebrate abundance and taxon richness in drainage channels were significantly lower in November compared to the other sampling months (October, February). The decrease in taxon richness observed in November was associated with chlorpyrifos and azinphosmethyl peak concentrations. The most remarkable changes were the decrease in sensitive taxa such as Baetidae and the increase in some tolerant taxa such as Chironomidae and Gastropoda.For all three pesticides, the acute hazard quotient exceeded the risk criteria for invertebrates. The effects of the three pesticides on aquatic organisms, characterized by joint probability curves, showed that the LC50 of 10% of the species were exceeded five and three times by the concentrations of azinphosmethyl and chlorpyrifos during the study period, respectively. However, the correlation between the pesticide concentrations and both taxon richness and abundance of macroinvertebrates at each site (irrigation and drainage channels) was indicative that only chlorpyrifos was negatively correlated with both parameters (Spearman r2 - 0.61, p = 0.0051 and Spearman r2 - 0.59, p = 0.0068 for taxon richness and abundance correlation, respectively). We conclude that macroinvertebrate assemblages in drainage channels were highly affected by chlorpyrifos levels.