Dynamic of heavy metals in wheat grains collected from the Liangfeng Irrigated Area, Beijing and a discussion of availability and human health risks
北京市凉凤灌区小麦重金属含量的动态变化及健康风险分析——兼论土壤重金属有效性测定指标的可靠性

Irrigation using wastewater containing elevated levels of heavy metals can result in steadily increasing soil concentrations which, in turn, can contribute to elevated tissue levels in crops. A field experiment was conducted in the Liangfeng Irrigated Area in Beijing to investigate the effects of wastewater irrigation on heavy metal concentrations in wheat grain. In addition, the study explored the relationship between total and extractable concentrations of heavy metals in soil and concentrations in grain. Twenty-one soil samples and corresponding wheat grain samples were collected, and the concentration of As, Cr, Cd, Cu, Hg, Ni, Pb and Zn were measured. The concentrations of Ni, Pb, and Zn in wheat grain were 38.1, 28.6 and 4.8% higher, respectively, than the China National Hygienic Standards for Food. The concentrations of Hg and Cd in some samples were near, although still lower than, the China National Hygienic Standards for Food. Concentrations of Hg, Pb and Cu in wheat grain were significantly higher than concentrations measured during investigations in the same area in the 1970s. These data indicate that the accumulation of some heavy metals has accelerated and there may be human health risks associated with consumption of the grain of wheat grown in the Liangfeng Irrigated Area. Despite the elevated levels of some metals in wheat, there were no significant correlations between either the total or the extractable metal concentrations in soils and metal concentrations in wheat grains. It might indicate that using the extractable heavy metal to evaluate the effect of heavy metal to the crop in soil was not more convictive than total heavy metals.