Accumulation and Translocation of Toxic Heavy Metals in Winter Wheat (Triticum aestivum L.) Growing in Agricultural Soil of Zhengzhou, China

Bulletin of Environmental Contamination and Toxicology, Mar 2009

A field experiment was conducted to study the accumulation of toxic heavy metals by winter wheat (Triticum aestivum L.) grown in the agricultural soil in the suburb of Zhengzhou City, China. The quantities of heavy metals (Cd, Cr, Pb, As, Hg) were determined in different parts of wheat plant. The content of five toxic metals was found significantly higher in roots than in the aerial parts of wheat (stems and leaves, and grains). Additionally, wheat roots were enriched in Cd, Pb, and Hg from the soil, while Cr and As were hardly taken up by the roots. On the other hand, the winter wheat transported five toxic heavy metals very weakly from root to grain in the various irrigation regions.

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Accumulation and Translocation of Toxic Heavy Metals in Winter Wheat (Triticum aestivum L.) Growing in Agricultural Soil of Zhengzhou, China

W.-X. Liu 0 1 J.-W. Liu 0 1 M.-Z. Wu 0 1 Y. Li 0 1 Y. Zhao 0 1 S.-R. Li 0 1 0 J.-W. Liu Environmental Protection Bureau of Henan Province , Zhengzhou 450007, People's Republic of China 1 W.-X. Liu (&) M.-Z. Wu Y. Li Y. Zhao S.-R. Li Department of Environmental Sciences, Henan Agricultural University , Zhengzhou 450002, People's Republic of China A field experiment was conducted to study the accumulation of toxic heavy metals by winter wheat (Triticum aestivum L.) grown in the agricultural soil in the suburb of Zhengzhou City, China. The quantities of heavy metals (Cd, Cr, Pb, As, Hg) were determined in different parts of wheat plant. The content of five toxic metals was found significantly higher in roots than in the aerial parts of wheat (stems and leaves, and grains). Additionally, wheat roots were enriched in Cd, Pb, and Hg from the soil, while Cr and As were hardly taken up by the roots. On the other hand, the winter wheat transported five toxic heavy metals very weakly from root to grain in the various irrigation regions. - and the possibility of synergistic effects of two or more metals may be of considerable importance at some sites contaminated with heavy metals (Nan et al. 2002). These metals can be transferred and concentrated into plant tissues from the soil, and brought about significant reductions in both plant growth and grain yield of wheat (Athar and Ahmad 2002; O ncel et al. 2000). They can be toxic to photosynthetic activity, chlorophyll synthesis and antioxidant enzymes (Murzaeva 2004; Ouzounidou et al. 1997; Panda et al. 2003). Every metal and plant interacts in a specific way, which depends on several factors such as soil type, plant, growth conditions and the presence of other ions. Metal uptake by grains was directly related to the applied heavy metal with greater concentrations of metals found in cases where metals were added separately rather than in combinations (Athar and Ahmad 2002). Different tillage systems, continuous grass and agricultural crops rotation affect the uptake and distribution of heavy metals (Al-Najar et al. 2005; Lavado et al. 2001). Liu et al. (2006, 2007) reported that rice plant and vegetables accumulated heavy metals from the agricultural soil under actual natural condition. However, few studies have been carried out on the fully grown plant of wheat raised on the agricultural soil. Therefore, a field experiment was carried out to investigate accumulation and translocation of toxic heavy metal by winter wheat grown in the agricultural soil under real field condition. This has important implication in the understanding of heavy metal contamination through the food chain. Materials and Methods The crop chosen for study was winter wheat (Triticum aestivum L.) which was the main crop cultivated in the area, and its growing period was about 210 days (from November to May of the following year) in the suburb of Zhengzhou city, Henan Province, China (34 420 N; 113 450 E; altitude 110.4 m). The area has a warm spring continental weather with an annual average temperature and rainfall of 14.3 C and 640.5 mm, respectively. Wheat plants were sampled during maturity at eight sites in May 1998, which were divided into three districts: municipal sewage irrigation region (MSIR) (Chengang, Xuzhuang, and Jiagang), Yellow River irrigation region (YRIR) (Zhaolanzhuang, and Jingshuicun), and groundwater irrigation region (GWIR) (Xincun, Ershilipu and Huayuankouxiliuhuangcun). Wheat plants were selected with five points at each site, and the corresponding soils (at 020 cm in depth) were also collected. Sampled plants were separated into roots, aboveground material (stems and leaves), and grains, and then rinsed with deionized water, dried at 65 C for 48 h, grounded with an agate mill, and homogenized. Metals As, Hg, Cd, Pb and Cr were determined according to previously described methods (Liu et al. 2007). A microwave assisted digestion procedure was used. About 0.53 g of homogenized samples was digested under pressure in Teflon vessels with 4 mL of nitric acid and 1.5 mL of hydrogen peroxide. Samples with a low aqueous content were ashed at 450 C in a furnace. On completion of the digestion and after adequate cooling, solutions were filtered and made up to 50 mL with 1% nitric acid. Metals Cr, Cd, and Pb contents were analyzed by flame atomic absorption spectrometry (FAAS, Hitachi Z-8000, Hitachi Ltd., Tokyo, Japan), whereas concentrations of Hg and As were determined using coldvapor atomic absorption spectrometry (CV-AAS) with a hydride generation VA-90 model (TongJi University, China) and sodium borohydride as the reductant. All reagents were supra-pure and high-purity water was employed throughout. A sample of standard reference material (NIST SRM 2709), a blank, and a determination in duplicate were included for assurance of analytical accuracy. The analytical results showed no signs of contamination and that the precision and bias of the analysis were generally \10% (...truncated)


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W.-X. Liu, J.-W. Liu, M.-Z. Wu, Y. Li, Y. Zhao, S.-R. Li. Accumulation and Translocation of Toxic Heavy Metals in Winter Wheat (Triticum aestivum L.) Growing in Agricultural Soil of Zhengzhou, China, Bulletin of Environmental Contamination and Toxicology, 2009, pp. 343-347, Volume 82, Issue 3, DOI: 10.1007/s00128-008-9575-6