Pesticide occurrence in a water course impacted by intensive horticultural production in the outskirts of La Plata, Argentina

MAC LOUGHLIN, TOMÁS M.; MARINO DAMIÁN; LETICIA PELUSO

Congreso; 8 TH YOUNG ENVIRONMENTAL SCIENTISTS MEETING; 2019

La Plata (Argentina) has one of the most important horticultural greenbelts in the country, where highly diversified and intensiveproduction systems predominate. Despite a production highly dependent on pesticide use, their impact on the surrounding environment remains largely unknown. The objective of the current study is to investigate on the occurrence and concentrations of pesticides in the different environmental matrices of a representative watercourse surrounded by horticultural production. For that purpose, five sites along the Carnival creek were studied during six sampling campaigns (C1-C6) encompassing 3 years. Surface water (total) were extracted by liquid-liquid extraction, suspended particulate matter (SPM, filtered in situ through 0.45 µm) by ultrasonication, and sediments by QuEChERS. Precolumnderivatization with FMOC-Cl was performed for glyphosate (GLY) and its environmental metabolite, the aminomethylphosphonic acid (AMPA). Instrumental analysis was carried out by gas or liquid chromatography coupled with mass spectrometry in selective ion mode. For each matrix 30 samples were analyzed, bringing it to a total of 180 samples. Surprisingly, GLY + AMPA were detected in all matrices in all samplingcampaigns, except for one. Other herbicides, such as atrazine and trifluralin, were detected at frequencies >25%. In C2 and C4, insecticide concentrations were above the guideline for aquatic life protection. In SPM, GLY + AMPA were detected in 75% of the samples. Azoxystrobin was detected in water and sediment samples (>25%). In sediments, C4 presented the highest total pesticide mass, 12725 ng/g: 63% due to herbicides and 32% due to insecticides. While in C1, 72% of the 5163 ng/g found were due to insecticides, and 21% due to herbicides. The highest concentrations found were 4634 ng/g of GLY + AMPA (C4), 2258 ng/g of chlorpyrifos (C1), and 2605 ng/g of λ-cyhalothrin (C4). Maximum pesticide loads were as it follows: C4>C1>C2>C6>C5>C3. From the headwater, as the horticultural activity intensifies, surface water concentrations reflect on the pesticide use trend in the area: herbicide concentrations decreased as insecticide concentrations increased. Up to 12 pesticides were detected in the same campaign (C2). One of the most relevant findings is the detection of herbicides in a horticultural setting. Pesticides used in this productive activity can effectively reach nearby watercourses and have the potential to negatively affect the aquatic life.