Khurana M P S, Bansal R L
Department of Soils, Punjab Agricultural University, Ludhiana-141 004, India.
J Environ Biol. 2008 Sep;29(5):793-8.
Analysis of soil samples collected from sewage and tube well irrigated soils of Ludhiana, Amritsar Jalandhar and Mandi Gobindgarh, revealed that Diethylene triamine pentaacetic acid extractable nickel ( DTPA-Ni) was found to be higher in sewage fed soils. Sewage irrigation increased soil DTPA-Ni content by 3.04 times over the tube well irrigated soils. The content of DTPA-Ni showed decreasing trend with depth. Hydrogen concentration (pH) was negatively and significantly correlated with DTPA-Ni nickel whereas, organic carbon and total Ni show positive and significant correlation. Sequential fractionation was carried out to partition Ni in to fractions namely exchangeable and water soluble, organic bound, carbonate bound, Mn oxides bound, amorphous Fe oxides, crystalline Fe oxides bound and residual. Plant availability of these fractions is believed to decrease in the above order. Sequential fractionation indicated that every extracted fraction exhibited increase in Ni content with sewage irrigation with most prominent increases occurring in the organic and oxide fractions. The lowest amount of Ni in exchangeable and water soluble and the highest in residual pools testify that plants grown on these soils may not suffer from Ni toxicity. Though all the crops irrigated with sewage water had appreciably higher concentration of Ni as compared to the crops raised with tube-well water yet raya (Brassica juncea) and toria (Brassica campestris) accumulated higher content of heavy metals as compared to other crops, with higher content in roots than shoots. Transport index suggested that major part of taken up Ni is translocated to top parts of plant. Based on values of transport indices, different crops maybe arranged as toria > raya = maize > bajra > lady finger. As the plants take up nickel readily and there is danger of its excessive accumulation in plant organs and devaluation of the plant products. This is topical issue particularly in crops used for direct consumption.
对从卢迪亚纳、阿姆利则、贾朗达尔和曼迪戈宾德加尔的污水灌溉土壤和管井灌溉土壤中采集的土壤样本进行分析后发现，在污水灌溉的土壤中，二乙烯三胺五乙酸可提取镍（DTPA-Ni）含量更高。与管井灌溉土壤相比，污水灌溉使土壤中DTPA-Ni含量增加了3.04倍。DTPA-Ni的含量随深度呈下降趋势。氢离子浓度（pH值）与DTPA-Ni呈显著负相关，而有机碳和总镍呈显著正相关。进行了连续分级分离，将镍分为可交换态和水溶态、有机结合态、碳酸盐结合态、锰氧化物结合态、无定形铁氧化物、结晶铁氧化物结合态和残留态等组分。据信这些组分对植物的有效性按上述顺序降低。连续分级分离表明，随着污水灌溉，每个提取组分中的镍含量均有所增加，其中有机和氧化物组分增加最为显著。可交换态和水溶态中镍含量最低，残留态中镍含量最高，这证明在这些土壤上生长的植物可能不会遭受镍毒性。尽管与用管井水灌溉的作物相比，所有用污水灌溉的作物镍浓度都明显更高，但与其他作物相比，芥菜和油菜积累的重金属含量更高，根部含量高于地上部分。转运指数表明，植物吸收的镍大部分转移到植物顶部。根据转运指数值，不同作物的排列顺序可能为：油菜>芥菜=玉米>珍珠粟>秋葵。由于植物很容易吸收镍，存在镍在植物器官中过度积累以及植物产品贬值的风险。这是一个热门问题，尤其是在用于直接消费的作物中。
