Heavy metals pollution level in wastewater and soils in the alto balsas sub-basin in tlaxcala and puebla, Mexico

Abstract

The objective of this work was to determine if metals and As contained in agricultural soils irrigated with wastewater are of anthropic or natural origin. For this, the geoaccumulation index and the enrichment factor were calculated from the content of Cd, Pb, Ni, Cu, Co, Cr, Zn and As, in the irrigated soils with the wastewater of the Atoyac and Zahuapan rivers, as well as the Valsequillo channel. Samples of wastewater and soil were collected in 16 sites grouped into four zones in two seasons of the year (summer and spring). The determination of metals and As was carried out with a plasma optical emission spectrometer with inductive coupling (ICP-OES) after digestion in a microwave equipment. The differences (p < 0.05) between sources of wastewater coincide with their origin, where the Atoyac river has the highest concentration of Pb. The metals and As in water did not exceed the levels allowed by the NOM-001-ECOL-1996 and the regulations of the Canadian Council of Ministers of the Environment and only the Cu was higher than the value established by the legislation of Spain. The soils showed a metal and arsenic content in decreasing order: Zn (22.8) > Cr (17.7) > Ni (14.8) > Pb (14.7) > Cu (13.06) > Co (5.5) > As (5.3) > Cd (1.2) mg/kg. The geoaccumulation index was 0.003 to 3.0, Cd the one with the highest geoaccumulation. The enrichment factor fluctuated from 1.84 to 6.0. Both indices show the existence of anthropic contamination of agricultural soils in the Alto Balsas sub-basin.