Interaction between Cd and Pb in the soil-plant system: a case study of an arid oasis soil-cole system

The Hexi Corridor,our study area,is located in Northwest China and is also the most developed area of oasis farming in arid regions of Northwestern China.However,the rapid development of metallurgy and chemical industries in this region poses a great threat to the accumulation of heavy metals in crops.The objectives of this study are(1)to determine the influence of heavy metals on plant growth;(2)to assess the translocation capability of heavy metals in soil-plant system;and(3)to investigate the interaction between heavy metals.Pot experiments were conducted on cole(Brassica campestris L.)grown in the arid oasis soils singly and jointly treated with cadmium(Cd)and lead(Pb).Nine treatments were applied into the pots.Under the same planting conditions,three scenarios of Cd,Pb and Cd–Pb were designed to compare the interaction between Cd and Pb.The results showed that the response of cole weights to Cd,Pb and Cd–Pb treatments was slight,while Cd and Pb uptakes in cole were more sensitive to the single effects of Cd and Pb concentration in soils from the lower treatment levels.Under the influence of the single Cd,Pb and joint Cd–Pb treatments,Cd concentrations were lower in the cole roots than in the shoots,while for Pb,the results were opposite.Comparison studies revealed that the interaction of Cd and Pb could weaken the cole’s ability to uptake,concentrate and translocate heavy metals in arid oasis soils.

Bioaccumulation and translocation of cadmium in cole (Brassica campestris L.) and celery (Apium graveolens) grown in the polluted oasis soil,Northwest of China

A pot experiment was conducted to study the bioaccumulation and translocation of cadmium （Cd） in cole （Brassica campestris L.） and celery （Apium graveolens） grown in the Cd-polluted oasis soil, Northwest of China. The results showed that Cd in the unpolluted oasis soil was mainly bound to carbonate fraction （F2） and Fe-Mn oxide fraction （F3）. However, marked change of Cd fractions was observed with increasing soil Cd concentrations, in which the concentration of Cd in F1 （exchangeable fraction）, F2 and F3 increased significantly （p 〈 0.001 for F1, F2 and F3）. The growth of cole and celery could be facilitated by low concentrations of Cd, but inhibited by high cortcentmdons. The correlation analysis between the fraction distribution coefficient of Cd in the soil and Cd concentration accumulated in the two vegetables showed that Cd in F1 in the soil made the greatest contribution on the accumulation of Cd in the two vegetables. The high bio-eoncentration factor and the translocation factor of Cd in both cote and celery were observed, and Cd had higher accumulation in the edible parts of the two vegetables. Therefore, both cole and celery grown in Cd-polluted oasis soil have higher risk to human health. And the two vegetables are not suitable to be cultivated as vegetables consumed by human in the Cd-polluted oasis soil.

Chemical fractionations and bioavailability of cadmium and zinc to cole (Brassica campestris L.) grown in the multi-metals contaminated oasis soil,northwest of China

A pot experiment was conducted to study the relationship between distribution of cadmium （Cd） and zinc （Zn） and their availability. to cole （Brassica campestris L.） grown in the multi-metal contaminated oasis soil in northwest of China. The results showed that Cd and Zn in the unpolluted oasis soil was mainly found in the residual fractionation, however, with increasing contents of Cd and Zn in the oasis soil, the distribution of Cd and Zn changed significantly. The growth of cole could be promoted by low Cd and Zn concentration, but significantly restrained by high concentrations. There was antagonistic effect among Cd and Zn in the multi-metals contaminated oasis soil. Stepwise regression analysis between fractionations distribution coefficients of the two meals in the soil and their contents in cole showed that both Cd and Zn in the exchangeable fractionation in the oasis soil made the most contribution on the uptake of Cd and Zn in cole. The bio-concentration factor （BCF） of Cd was greater than Zn in cole, and BCFs of the two metals in leaves were greater than those in roots. The translocation factors of the two metals in cole were greater than 1, and the two metals mainly accumulated in the edible parts in cole. Therefore, cole is not a suitable vegetable for the oasis soil because of the plants notable contamination by heavy metals.