Heavy Metal Content in Soils under Different Wastewater Irrigation Patterns in Chihuahua, Mexico

Abstract

An area near the city of Chihuahua has been traditionally irrigated with wastewater to grow forage crops. It has been hypothesized that metal levels could be found in these soils high enough to cause potential health problems to the population. The objective of this study was to determine heavy metal concentrations in different soils due to irrigation practices. Four soil types were evaluated; a soil with a past and present history of wastewater irrigation (S1), a soil with a history of wastewater irrigation until 2003 (S2), a soil with no irrigation history (S3), and a soil similar to S1 and adjacent to the river where the wastewater is transported (S11). Three soil depths were evaluated; 0–15, 15–30 and 30–50 cm. Consequently, a total of 150 soil samples were analyzed evaluating pH, EC, OM and the following elements; Na, K, Cd, Pb, Ni, Cr, Cu and Fe. The pH (P=0.000) and EC (P=0.000) were different for each soil type but no differences were noted for soil depth and the interaction. Maximum pH levels were noted in S3 with a value of 8.74 while maximum EC was observed in S1 with a value of 0.850 dSm−1. The OM level was different for soil type (P=0.000), soil depth (P=0.005) and the interaction (P=0.014). S1 and S11 obtained maximum levels of OM while minimum levels were noted in S3. Maximum OM levels were observed at the 0–15 cm depth followed by the 15–30 cm depth and finally at the 30–50 cm depth. The highest concentration of metals was as follows: K in S1 (359.3 mg kg−1); Cd in S1 (4.48 mg kg−1); Pb in S11 (155.83 mg kg−1); Ni in S1 (10.74 mg kg−1); Cu in S1 (51.36 mg kg−1); B in S3 (41.5 mg kg−1); Fe in S3 (20,313.0 mg kg−1), Cr in S3 (44.26 mg kg−1) and Na in S3 (203.0 mg kg−1). The conclusion is that some metals are present in the soils due to anthropogenic activities but others are present in natural forms.

Socio-economic background of wastewater irrigation and bioaccumulation of heavy metals in crops and vegetables

“…High concentration of various heavy metals in WW and CW might be the outcome of industrial effluent discharged without treatment (Galavi et al, 2010;Aftab et al, 2011) and its application for growing crops, over a long period, built up heavy metals in the soil (Maldonado et al, 2008). Physical and chemical properties of soil (texture, bulk density, porosity, pH, EC, organic matter, CEC, type of clay minerals, redox potential, oxides content such as Fe, Mn, aluminum and calcium carbonate) had a great role for heavy metal accumulation in ground water (Aydinalpi and Marinova, 2003).…”

Heavy Metal Pollution of Lakes along the Mid-Lower Reaches of the Yangtze River in China: Intensity, Sources and Spatial Patterns

“…Other lakes near urban areas, such as Xuanwu Lake, Mochou Lake, Bali Lake and Ci Lake, have high concentrations of Pb, Zn and Cu. Today much of the anthropogenic Cu, Zn and Pb originates from smelters, fossil fuel uses, industrial discharges, mining and wastewaters [27,28]. Heavy metals have been used by humans for a variety of purposes throughout the 20th century.…”

“…The discrepancy indicated that the distributions of Cr, Ni, Fe and Mn were influenced by mixed factors. Previous studies also had found that Fe and Mn were more sensitive to redox-reactions than the other elements and showed high concentrations in the surface sediments in many lakes [27]. …”

Water Resource Management in Five Mexican States

“…Long-standing practice has been for forage crops situated near the city of Chihuahua to be irrigated with wastewater (Maldonado et al, 2008). This sounds like a solid approach to getting the most possible out of water, but it is not clear what role residential wastewater plays in the irrigation of agricultural produce.…”