Pollution and assessment of soil heavy metal Cd, Cr, Pb and Hg in greenhouse vegetable fields of Xinxiang suburb, China

To evaluate heavy metal pollution of greenhouse vegetable soil is of great significance to ensure food security and public health in China. Heavy metal Pb, Cd, Cr and Hg content in greenhouse vegetable soils in Xinxiang suburb were studied by using atomic absorption spectrometry and cold atomic absorption spectrometric method. According to the Environmental Quality Evaluation Standard for Farmland of Greenhouse vegetable production(HJ 333—2006), the pollution situation of heavy metals Cd, Pb, Cr and Hg in greenhouse vegetable soil were also evaluated. The results showed that the contents of Cd, Pb Cr and Hg in greenhouse vegetable soils were 25.64, 156.18, 992.38 and 0.316 mg·kg-1, respectively, which were higher than the official standard, suggesting that greenhouse vegetable soils were seriously contaminated by heavy metal Pb, Cd and Cr. Cd pollution was the most serious in Houhetou sampling sites, which the average content was 33.78 mg·kg-1, 111.6 times exceed the concentration limit of the official standard for Cd, followed by 66 times in Dongshuidong sampling site. Hg content in Qianxinzhuang sampling sites were exceed the standard 127%, while under the official standard in other sampling sites. In different layers of soils, heavy metals Hg content in 0 to 10 cm in depth was higher than in 10 to 20 cm in depth, while showed no obvious regularity for other heavy metals. In different seasons, Contents were gradually increased for Cr from spring to autumn, and decreased for Hg, with no consistent trend for Pb and Cd. Comprehensive pollution index was the highest in Houhetou(82.49), following by Qianhetou(66.01), Qianxinzhuang(63.30), Dongheidui(52.50), and Dongshuidong(49.32). Generally speaking, comprehensive pollution indexes of heavy metals were far more than the V grade limit(≥3.0), which implied that greenhouse vegetable soils were heavily polluted by heavy metal Pb, Cd, Cr and Hg. It was suggested that the greenhouse vegetable soil is of high ecological risk in Qianhetou, Houhetou and Qianxinzhuang, and moderate risk in Dongshuidong and Dongheidui sampling sites.