Heavy metals in soils and forage grasses irrigated with Vieira River water, Montes Claros, Brazil, contaminated with sewage wastewater

Matheus Mendes Reis,Leonardo David Tuffi Santos,Ariovaldo José Da Silva,Leonardo Michel Rocha,Gevany Paulino De Pinho

doi:10.4136/ambi-agua.2440

Abstract

There is great concern with soil and plant contamination by heavy metals due to the use of polluted water in agricultural irrigation. In this study, areas irrigated with Vieira River water were evaluated as to contamination by As, Cr, Cu, Ni, Pb and Zn. The Vieira River receives effluent from Montes Claros city, state of Minas Gerais, Brazil. To do so, two irrigated areas were selected, one upstream and one downstream of the Montes Claros city. Wastewater discharge increased the concentration of As and Ni in the water of Vieira River, and consequently, of As, Cr, Cu, Ni, Pb and Zn in the soil and of As and Zn in forage grasses. However, the content of heavy metals in the soil did not exceed the internationally recommended limits. Pollution load index (PLI) and contamination factor (CF) indicated the existence of pollution and moderate contamination in downstream soils of the city of Montes Claros. Potential ecological risk index (RI) and ecological risk factor (Er) indicated a low ecological risk, but these indicators were higher in downstream soils of Montes Claros. Arsenic (As) was the only heavy metal that featured a transfer factor (TF) higher than the widespread values found in literature and positive geoaccumulation index (Igeo), indicative of anthropogenic pollution.

Highlights

The dispersal of heavy metals in irrigated agricultural areas is growing, which results in food contamination that can be harmful for animals and humans
None of the concentration values of heavy metals found in the two farms (F1 and F2) were higher than the international limits recommended for water use in irrigation (USEPA, 2012; WHO, 2006)
It is important to emphasize that the water can be inappropriate for irrigation and superficial flooding depending on the use and occupation of the soil, once this irrigation method can favor the direct contact of animals and humans with the contaminated water

Summary

Introduction

The dispersal of heavy metals in irrigated agricultural areas is growing, which results in food contamination that can be harmful for animals and humans. Heavy metals have low solubility, and are not degradable in water, which contributes to their accumulation in soil, and in plants cultivated on these irrigated areas with contaminated water. Heavy metals’ transfer from soils to plants is one of the main ways of humans exposure through the food chain (Chopra and Pathak, 2015). Until 2010, Vieira River was the main river receiving untreated sewage produced in the city of Montes Claros, state of Minas Gerais, Brazil. The river still receives city sewage; there is a prior treatment process, carried out in the wastewater treatment plant (WWTP) of Montes Claros. In the margins of Vieira River, there are farms that use its water for the irrigation of pastures; there are no studies on heavy metal contamination of soil and plants irrigated with the river water

Methods

Results

Conclusion