Pesticide pollution from the agricultural activity in the Gualeguay river basin, Entre Ríos, Argentina

MAC LOUGHLIN TOMÁS MARIANO; PELUSO, MARÍA LETICIA; MARINO, DAMIÁN J. G.

Workshop; 8th Latin American Pesticide Residue Workshop (LAPRW2021); 2021

Agriculture in Argentina has undergone major transformations in recent decades with the incorporation of biotechnological packages. Despite the agro-industrial relevance of the province of Entre Ríos. Few studies evaluate the entry and dynamics of pesticides in waterbodies of the region, considering their contribution to the Paraná Delta, the second largest wetland in Latin America. The objective of this work was to study the occurrence of pesticide residues in surface waters and bottom sediments in the lower zone of the Gualeguay River, a representative basin of the region. Four sampling campaigns were carried out over 2 years, covering the 4 seasons. Samples were collected from 7 tributary streams to the Gualeguay River and from 6 sites on the main course. Water samples were extracted by LLE with dichloromethane and sediments by QuEChERS. Multi-residue analysis was carried out on a Perkin Elmer GC-MS1. For glyphosate (GLY) and AMPA, 1 mL of water was adjusted to pH 9 with borate buffer and derivatized with FMOC-Cl. For sediments, 7 g were extracted with borate buffer by sonication and 1 mL of the supernatant was derivatized. Instrumental analysis was performed using a Waters ULPC-MS/MS2. GLY was detected in 71% and 97% of the water and sediment samples, while AMPA was detected in 63% and 87%, respectively. While atrazine (ATZ) was detected in 73% of the waters. The spatial analysis regarding the origin of the sample revealed that there were no statistically significant differences between the concentrations in the tributaries and those quantified on the main course for GLY and AMPA in water and sediment, and for ATZ in water. Still, the maximum concentrations were found on the tributaries: water: GLY=10.90 μg·L-1, AMPA=9.60 μg·L-1, ATZ=2.113 μg·L-1; sediment: GLY=208.6 μg·kg-1, AMPA=104.7 μg·kg-1. The GLY:AMPA relationship provides information on the source, destination, and transport of glyphosate in the environment. In the water samples, most of the GLY:AMPA ratios were >1. These results suggest short transport times and mobilization distances from the application zone to the analyzed waterbodies. Pyrethroids insecticides bifenthrin, cypermethrin, deltamethrin and λ-cyhalothrin were detected in water, with frequencies lower than 10%. Nevertheless, concentrations were above their respective guideline for the protection of aquatic life, up to more than 200 times the guideline, even in samples from the main course. The homogeneity in the distribution of pesticide concentrations shows not only the large volume of these that is used in agriculture, but also the mobility of pesticides in the environment, being able to be quantified in water bodies with flows greater than 200 m3·s-1, such as that of the Gualeguay River.