黄淮海平原小麦吸收镉与土壤可浸提镉间关系研究

土壤重金属镉浸提量与小麦吸收镉量关系是评价浸提方法以及土壤中镉有效性的重要依据,为了给黄淮海平原小麦产区土壤镉污染评价提供科技支撑。分别采用0.43 mol·L~(-1)HNO_3、0.1 mol·L~(-1)HCl、0.05 mol·L~(-1)EDTA浸提土壤镉的方法对黄淮海平原11个不同地点大田土壤样品和24个小麦植株样品进行了测定,并对3种不同浸提剂浸提的土壤有效态镉量间的相互关系,及土壤浸提镉含量与小麦镉含量间的关系进行了探讨。结果表明:不同浸提剂浸提的土壤Cd含量、全量间的相关关系均达极显著水平;3种浸提剂的Cd浸提率为58.7%(0.43 mol·L~(-1)HNO_3)53.2%(0.05 mol·L~(-1)EDTA)25.9%(0.1 mol·L~(-1)HCl),不同浸提剂浸提的土壤有效态Cd含量与小麦植株Cd含量的相关性顺序为r=0.74(0.05 mol·L~(-1)EDTA)r=0.64(0.43 mol·L~(-1)HNO_3)r=0.49(0.1 mol·L~(-1)HCl);在pH为7.71~8.59和土壤全Cd含量范围为0.107~0.212 mg·kg~(-1)条件下,以EDTA浸提的土壤Cd含量及土壤Cd全量结合土壤pH值建立的方程可以较好地预测小麦籽粒Cd含量;经推算,EDTA浸提的土壤Cd和土壤Cd全量的安全临界值可分别为0.671 mg·kg~(-1)和1.02 mg·kg~(-1)。

The relationship between cadmium in wheat plant and cadmium extracted by EDTA and diluted acids in soil in Huanghuaihai Plain

The relationship between the concentrations of soil extractable cadmium(Cd) and Cd taken up by wheat plant is important to evaluate soil testing for extractability and availability of Cd in soil. In the present study, the concentrations of soil Cd extracted by 0.43 mol·L^-1 HNO₃, 0.1 mol·L^-1 HCl and 0.05 mol·L^-1 EDTA, as well as related to the concentration of Cd in wheat plant was investigated using 11 field soil samples and 24 wheat varieties collected from Huanghuaihai plain. The results showed that the percentage of extractable Cd to total Cd in soils was found in the order:58.7%(0.43 mol·L^-1 HNO₃) > 53.2%(0.05 mol·L^-1 EDTA) > 25.9%(0.1 mol·L^-1 HCl). However, the correlations between the concentrations of soil Cd extracted by the 3 extractants themselves were significant. It was also found that the correlation coefficients(r) between soil Cd extracted by these extractants and Cd in wheat plant in the order:r=0.74(0.05 mol·L^-1 EDTA)>r=0.64(0.43 mol·L^-1 HNO₃)>r=0.49(0.1 mol·L^-1 HCl), which indicated that chelating agents, such as EDTA, are better than diluted acids, such as HNO₃ or HCl, because most of soils in this area are calcareous soils. In the specific area where soil pH ranged from 7.71 to 8.59 and soil total Cd ranged from 0.107 to 0.212 mg·kg^-1, the regression equations of EDTA extractable Cd combined with the soil pH were developed and can be used to predict the concentrations of Cd in wheat plants very well although soil total Cd also worked well. According to the regression equations and the limits of Cd in wheat grains, the safety critical values of EDTA extractable and total Cd in soil were estimated as 0.671 mg·kg^-1 and 1.02 mg·kg^-1, respectively. These results are very helpful for risk assessment of Cd in soils and wheat grains in the main wheat producing area-Huanghuaihai Plain.