Accumulation and Translocation of Toxic Heavy Metals in Winter Wheat (Triticum aestivum L.) Growing in Agricultural Soil of Zhengzhou, China
W.-X. Liu
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J.-W. Liu
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M.-Z. Wu
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Y. Li
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Y. Zhao
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S.-R. Li
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J.-W. Liu Environmental Protection Bureau of Henan Province
, Zhengzhou 450007,
People's Republic of China
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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.
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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)