Heavy Metal Accumulations In Different Crops And Their Responses To Pollution Stress

Based on the reclaimed soil in Nansha, heavy metal accumulations in differentcrops and their responses to pollution stress were investigated through field surveyand the potted experiment, in order to provide a scientific support for the safe use ofpolluted soil.The results show that:(1) average contents of Cu,Zn,Pb,Ni,Cr and Cd in thetopsoils are 59.57,277.91,81.96,43.50,157.29 and 2.60mg/kg respectively. Amongthem, Cd is the major pollutant and its maximum content exceeds the second grade ofsoil environmental quality standard 25.93 times;(2)Excepted for Cu and Zn,Pb,Ni,Cr and Cd in crops all exceed the permitted level.(3)The cumulated rate of heavymetals: Cd＞Zn＞Cu＞Ni＞Pb＞Cr; (4) The order of the cumulate abilities of crops is:leafy vegetables＞rhizome class vegetables＞fruits.The potted experiment results show that:(1) With the increase of heavy metalsconcentrations, the growth of vegetables are stressed more seriously, and theconcentration of chlorophylls and dissolved sugar are decreased significantly;(2) Theactivity of PPO showes an increasing trend as a whole, while the activeity of PODincreases firstly and then decreases. (3) The effect of heavy metals on vegetables isdependent on discrepancy of vegetable species.The same type of vegetable has different responses to different heavy metals.Different vegetables have different accumulations for the same heavy metal. Thebioaccumulation factor(BF) of the vegetables for Cu,Zn,Pb,Ni,Cr and Cd are0.0040-0.0278,0.0046-0.0186,0.0050-0.0290,0.0034-0.0107,0.0024-0.0196,0.0222-0.0977, respectively. Cd is the element accumulated by plants most easily.Moreover, the enrichment abilites of various vegetables for heavy metals are differentamong the species. Water spinach has the strongest ability of uptaking heavy metalsfrom soil, while the cumulated ability of tomato is lowest.