Evaluation of pesticide pollution in the Gualeguay Basin: An extensive agriculture area in Argentina.

The current agricultural production model was established in the 1990s based on the use of genetically modified organisms and agrochemicals, mainly pesticides. Despite pesticide spread and prevalence, data on the associated concentrations in surface watercourses are comparatively scarce. The aim of this work was to evaluate to what extent the >20 years of agricultural activity with the use of pesticides has impacted on the Gualeguay-River basin, with respect to the different stream orders: the tributary streams and main channel. Thirteen sites within the lower Gualeguay basin were sampled once every season (autumn, winter, spring, and summer) in 2017-2018. The samples were analyzed by gas chromatography time-of-flight mass-spectrometry (GC-TOF-MS) and ultraperformance liquid chromatography tandem mass-spectrometry (UPLC-MS/MS). The most frequently detected pesticide was glyphosate along with its metabolite (aminomethyl)phosphonic acid (AMPA), at 82 % and 71 % of surface water samples and 97 % and 92 % of bottom sediments, respectively; followed by atrazine in 73 % of the water samples. The concentrations of these compounds, each in their respective matrices, did not present sufficient statistically significant differences for differentiating a tributary stream from the main channel. Regardless of glyphosate's affinity for the suspended particulate and bottom sediments, over the entire basin the soluble fraction contributed on average to >80 % of the total concentration in surface water. Despite not being so frequently detected, certain insecticides, mostly deltamethrin, were likewise detected at concentrations above their water-quality guidelines for the protection of aquatic life, even in samples from the main channel. Upon comparison of the pesticide profiles of extensive- and horticultural-production systems in the country, atrazine emerged as a prime candidate to be used as a tracer of extensive agriculture contamination in the environment. Further research is required to establish to what degree pesticides used in agriculture and mobilized by watercourses have an impact on their associated wetland ecosystems.

Impact of Intensive Agricultural Production on the Ecotoxicologic Quality of Associated Medium-Order Streams: Cereal and Oilseed versus Horticultural Production.

Streams associated with agroecosystems receive inputs of chemicals used within a basin that negatively impact its environmental quality. In this work, we aimed at comparing, through a battery of ecotoxicological tests, the relative impact of the cereal and/or oilseed and vegetable and/or flower agricultural-production models on the ecotoxicologic quality of both the water column and the bottom sediments of medium-order streams. The study, performed over 4 years, involved two major agroproductive areas of Argentina, one predominating in cereal and/or oilseed crops (Area 1), the other in vegetable and/or flower agriculture (Area 2). Both productive systems impacted the associated surface water bodies negatively, with the intensive production of vegetables and flowers producing greater ecotoxicologic effects on diagnostic organisms. The intensive-agriculture systems associated with Area 2 caused greater negative impacts on the water column than those of Area 1, with this pattern occurring in reverse for the bottom sediments. Furthermore, the samples from the sites associated with horticulture were more frequently toxic than those from Area 1. Of the organisms used to assess sample toxicity-Lactuca sativa, Daphnia magna, and Hyallela curvispina-L. sativa was the most sensitive to the type of contaminants associated with the form of agricultural land use; whereas no differences in sensitivity were observed between the two crustaceans. We found that the sublethal effects were significantly more sensitive than the lethal. The findings from this work would strongly advocate more sustainable agricultural-management plans that employed phytosanitary products whose action were more environmentally sustainable.

Multiple pesticides occurrence, fate, and environmental risk assessment in a small horticultural stream of Argentina.

Peri-urban horticulture is crucial to local populations, but a global paucity of information exists regarding the contamination of the associated waterways because of this activity. The aim of this study was to assess pesticide pollution of surface water, suspended particulate matter and bottom sediments from the Carnaval Creek Basin (La Plata, Buenos Aires, Argentina) - a representative system of waterways surrounded by horticultural production - by over 40 selected herbicides, insecticides, and fungicides by gas-chromatography-time-of-flight mass spectrometry and ultraperformance liquid chromatography tandem mass spectrometry. Six sampling campaigns were conducted biannually from 2015 to 2017. Glyphosate and (aminomethyl)phosphonic acid (AMPA), surprisingly, were the most frequently detected pesticides, in concentrations comparable to those reported in areas with genetically modified extensive crops (maximum in water, 20.04 and 4.86 µg·L-1; in sediment, 1146.5 and 4032.7 µg·kgdw-1, respectively). The insecticides chlorpyrifos, cypermethrin and λ-cyhalothrin were detected in more than 30% of the samples. The concentrations tended to greatly exceed those previously reported - by up to more than 800 times for chlorpyrifos in water (maximum 2.645 µg·L-1) and more than 400 times for lambda-cyhalothrin in sediments (maximum 2607.7 µg·kgdw-1). The total pesticide concentration in surface water was found to be influenced by precipitation regimes but was independent of the season of the year, with precipitations of more than 140 mm diluting the pesticide concentrations to levels below detection limits. An environmental risk assessment performed with the pesticide concentrations of pesticides in surface water revealed that the surrounding horticultural activity posed a high risk for aquatic biota, with 30% of the samples exceeding the threshold value by more than a thousand times. We conclude that pesticides from horticultural use are a major threat to small streams and their biodiversity. This work provides valuable information that is scarce regarding the impact on watercourses exclusively as a consequence of horticulture.

Contribution of soluble and particulate-matter fractions to the total glyphosate and AMPA load in water bodies associated with horticulture.

Glyphosate-based herbicides are used in horticulture to prepare the soil for planting and to remove weeds surrounding greenhouses. Superficial runoff from production units can lead to glyphosate reaching nearby water bodies. Previous publications reported glyphosate's high affinity for suspended solids. The aim of the present work was to investigate the occurrence and concentrations of glyphosate and aminomethylphosphonic acid (AMPA) in soluble and suspended-particulate-matter fractions within the basin of the Carnaval-Stream, a water body traversing a horticultural greenbelt. Glyphosate and AMPA were detected in 67% and 83% of the samples, occurring in both fractions simultaneously at respective maximum concentrations of 17.0 and 4.5 µg.L1 in the soluble fraction and 35,620 and 19,586 µg.kg1 in the particulates. Although the calculated partition coefficients Kd confirmed that these compounds had tended to be associated with the particulate matter, the soluble glyphosate and AMPA contributed, on the average, to more than 90% of the total water volume. Although the analysis of suspended particulates is considered a more sensitive strategy for glyphosate and AMPA detection in surface water, these results demonstrate the need to analyze the soluble phase. The continual occurrence throughout a 3-year sampling was sufficient evidence demonstrating the use of glyphosate in horticulture.