Seasonal Variations in Arsenic Distributions and Mobility in a Shallow Pampean Lagoon

CHIODI BOUDET, L. N.; DOLAGARATZ CARRICAVUR, ARANTXA; POLIZZI PAULA; ROMERO, M.B; BUZZI, N.; COSTA AGUSTIN; MEDICI SANDRA; BRAMBILLA, E.; FERNANDEZ, EDUARDO; MARCOVECCHIO, JORGE EDUARDO; GERPE MS

Valdivia

Congreso; SETAC Latin America 14th Biennial Meeting-; 2021

Society of Environmental Toxicology and Chemistry (SETAC) LATINAMERICA

The presence of arsenic (As) in surface and groundwater is a serious environmental concern because of its high toxicity and global occurrence in the environment. The Chaco-Pampean plain, is one of the largest areas in the world with elevated As levels (geogenic origin), as well as one of the most important agricultural-livestock regions of Argentina, constituting a high risk for the human health. The pampean lagoons are shallow and highly dynamic, where there are wide range of physical, chemical, and biological factors that affect the mobilization of As in the freshwater?sediment interface. The mobility of As in such water bodies can be of concern, particularly in water bodies with probable use as drinking water, livestock water and/or crop irrigation. The aims of this research were to elucidate: 1) the seasonal variations in the distribution of total and labile As fractions in the surface sediments of Los Padres lagoon located in Buenos Aires province, Argentina 2) their mobility to water column in relation to its availability in sediments, and 3) the possible risk of using this resource of water. Surface sediment and water samples were taken from the lagoon and associated streams during the four seasons of the year (2018-2019). Arsenic were determined by atomic absorption spectroscopy. Total As in sediments did not show a clear seasonal pattern, with a range between 3.6-14.8 mg/kg and a positive linear relationship (r2=0.79, p spring (29%)> winter (26%)> autumm (16%). The close relationship between As - Fe, under the oxidant conditions and alkaline pH of the lagoon, would suggest As co-precipitation and adsorption on Fe oxides as probable route of immobilization in sediments, determining its low lability. The As levels in water varied between 10.9-24.8 µg/L, with maximum values during summer, in accordance with that reported for other shallow lakes. This increase coincided with the maximum lability in sediments (44%), evidencing the release of As into the water column. All water samples exceeded the limit establish in Argentina for human consumption (10µg/L) while not those of livestock (67µg/L) and crop irrigation (100µg/L), but were very close to Canadian limit for livestock (25µg/L). These results constitute the first report on seasonal variations of As concentrations in a pampean lagoon.