Cadmium accumulation, translocation factor, and health risk potential in a wastewater-irrigated soil-wheat (Triticum aestivum L.) system.

The accumulation of trace elements in wastewater-irrigated soils may introduce them to the food chain and therefore can threaten human health. The present study investigated the accumulation, translocation factor, and health risk potential of cadmium (Cd) in a soil-wheat system irrigated with treated wastewater compared with a reference soil (irrigated with fresh water). All treated wastewater-irrigated soils showed significantly higher levels of electrical conductivity (EC) than that of reference soil by 75-143%. Irrigation with treated wastewater increased both available and total Cd content in soil by 2-4 times. In all irrigated sites, Cd content was about twice as great as the maximum acceptable rate. Bioconcentration factor (BCF) and translocation factor (TF) indicated that Cd was mainly accumulated in the roots (BCF = 2.2-3.1), while little mobilization from roots to stems and grains was noted (TFshoot/root = 0.07-0.21; TFgrain/root = 0.18-0.24). The average hazard quotient (HQ) for different age groups of the population varied in the range of 0.1-1.0, implying low non-carcinogenic health risk of Cd to local wheat-consuming residents. The risk of Cd to cause carcinogenic health risk (CR) was in the range of 1 × 10-5 to 1 × 10-4, indicating low to moderate potential risk. CR for different age groups was in the order: individuals above 18 years old > individuals 7-18 years old > individuals 0-6 years old. For reducing potential health risks to local people, it is imperative to continuously monitor heavy metal levels in the wheat-soil system and urgently adopt more efficient managerial strategies to reduce Cd contamination.

Heavy metal bioavailability and accumulation in winter wheat (Triticum aestivum L.) irrigated with treated wastewater in calcareous soils.

Irrigation with raw or diluted wastewater increases in many developing countries, but the increasing availability and use of wastewater generates challenges for public agencies charged with minimizing potential impacts on public health and the environment. In this study, the available (DTPA-extractable) concentration of Zn, Cu, Cd, Pb, and Ni in the surface soil was measured in five sites irrigated with treated wastewater as compared with a site irrigated with freshwater (control). The major sources of wastewater were municipal wastewater, household, commercial, and industrial effluents, which were treated to settle and remove solids prior its use for irrigation. In addition, the concentration of the above five heavy metals and their accumulation and mobilization characteristics were determined in the roots, shoots, and grains of winter wheat (Triticum aestivum L.) grown in treated wastewater-irrigated soils. Irrigation with treated wastewater resulted in a remarkable build-up of metal concentrations in the soil (averaged over five sites) in the order of Cd (178.2%) > Ni (105.1%) > Cu (66.4%) > Zn (66.0%) > Pb (40.9%) compared with control. However, only Cd concentration exceeded the permissible range. The concentration of heavy metals was significantly greater (P < 0.05) in wheat roots than in shoots and grains (root ≫ shoot > grain). The highest concentrations were found in the roots in the order of Cu > Zn > Pb > Cd > Ni. The maximum concentrations of Zn, Cu, Ni, Cd, and Pb in wheat grains were 3.20, 1.20, 0.52, 0.31, and 0.21 mg kg-1, respectively. The bioconcentration and translocation factors of wheat showed that heavy metals quantitatively accumulated in the roots and were poorly translocated to the grains. The potential health risks, calculated as hazard quotients (HQ), were less than unity for most heavy metals, indicating that local people are within the safe limit regarding non-carcinogenic risks. However, the HQ value of Cd exceeded 1 for both children and adults, indicating a high health hazard for the whole exposed population by this metal.