| In this study,a series of field experiments were carried out in a heavy metal contaminated dryland soil(Pb,Cd,Cu and Zn)near Shuikoushan Mine Zone in Hengyang City(Soil A),and another near Shizhuyuan Mine Zone in Chenzhou City(Soil B),southern Hunan Province,respectively.This study included four sets of experiments,which were a dryland soil experiment of heavy metal accumulation in different vegetables cultivars,a pot experiment of screening amendment for remedying heavy metal soils,a dryland soil experiment of applying combined amendments to regulated heavy metal contaminated soils and planting vegetables,and an environmental risk assessment after applying combined amendments to dryland soil.The main objectives of this study were to investigate the differences of heavy metal accumulation in different vegetable cultivars,to screen the lower heavy metals in edible parts of vegetable cultivars which were main food for the local residents,to screen the combined amendments which can efficiently reduce the heavy metal bioavailability and study the mechanism of passivation heavy metal by combined amendments,to investigate the effects of screening combined amendments on the bioavailability of heavy metals in rhizosphere soil and the effects of combined amendments on heavy metal uptake and accumulation in vegetables,to investigate the effect of the vegetable environmental risk after the application of combined amendments,and to discuss the heavy metal transfer rules of "soil-vegetable" system in the whole research process.The main results were as follows:(1)For the melon and fruit vegetables cultivated in Shuikoushan Mine Zone,the range of Cd,Cu and Zn contents in the edible parts are 0.02-0.65,0.20-0.54,1.59-5.86 mg-kg-1,respectively.For the leafy vegetables,the range of Pb,Cd,Cu and Zn contents are 0.28-6.94,0.00-8.11,0.35-1.79,3.22-118.61 mg-kg-1,respectively.For the melon and fruit vegetables cultivated in Shizhuyuan Mine Zone,the range of Cd,Cu and Zn contents in the edible parts are 0.003-0.302,0.31-1.01,1.21-2.98 mg-kg-1,respectively.For the leafy vegetables,the range of Pb,Cd,Cu and Zn contents are 0.36-5.08,0.03-2.92,0.34-3.18,7.07-97.76 mg-kg-1,respectively.(2)In the experiment,six kinds of single amendments and eight different combined amendments had different degrees of reduction in leachate contents and MgCl2 exchangeable contents of Pb,Cd,Cu and Zn in soil.Comparing all the amendments selected in this experiment,it was found that the LS(2:1)and HZ(2:1)combination amendments had the best effect on the bioavailability of heavy metals in the soil,taking into account price factors and soil heterogeneity,LS(2:1)and HZ(2:1)were selected to investigate their actual effects for soil remediation(3)LS and HZ were applied in Soil A and Soil B which cultivated capsicum,water spinach,and amaranth.Soil pH values and CEC values increased significantly,but soil OM reduced slightly.The effect of LS increasing soil pH values and CEC values was greater than that of HZ.Two combined amendments LS and HZ significantly decreased the exchangeable contents,TCLP extraction contents and available contents of soil Pb,Cd,Cu and Zn,indicating that LS and HZ had a good ability to inactivate soil heavy metal,and the effect of LS on reducing heavy metal bioavailability was better than that of HZ.(4)There were significant relationships among soil pH value and CEC and contents of MgCl2 exchangeable and TCLP extractable heavy metals.Soil pH value and CEC were found in a significant negative relationship with the MgCl2 exchangeable Pb,while soil pH value and CEC also exhibited a negative relationship with the exchangeable and available contents of Cd,Cu and Zn,the TCLP extractable contents of Pb,Cd,Cu and Zn in soil.The relationship analysis showed that the combined action of increasing in soil pH value,soil colloid CEC,and soil adsorption capacity decreased significantly exchangeable,TCLP extractable and available contents of soil Pb,Cd,Cu and Zn after application of LS and HZ,and the main factor was increased soil pH value.(5)The biomass of capsicum,water spinach and amaranth increased greatly when LS and HZ were applied at 8 g·kg-1,and this biomass increased gradually with amounts of amendments additive.Application of LS and HZ(2-8 g-kg-1)decreased significantly contents of Pb,Cd,Cu and Zn in various organs of capsicum,water spinach and amaranth.Compared with the control,Pb contents in edible parts of capsicum,water spinach and amaranth in Soil A decreased 30.9%-74.4%,22.1%-26.9%,17.5%-26.8%,respectively;Cd contents decreased 30.0%-62.0%,10.9%-34.1%,7.1%-26.9%,respectively;Cu contents decreased 55.4%-76.0%,59.6%-80.8%,0.8%-27.4%,respectively;and Zn contents decreased 37.8%-77.4%,76.6%-89.8%,17.2%-40.0%,respectively.Pb contents in edible parts of capsicum,water spinach and amaranth in Soil B decreased 54.4%-97.1%,14.7%-22.8%,45.8%-59.0%,respectively;Cd contents decreased 53.7%-77.1%,24.4%-51.8%,30.1%-83.3%,respectively,;Cu contents decreased 0%,11.2%-17.7%,14.4%-60.4%,respectively;and Zn contents decreased 37.9%-44.8%,24.6%-38.6%,36.3%-78.6%,respectively,as a result of 0.2 g·kg-1 to 0.8 g·kg-1 addition of LS.Compared with the control,Pb contents in edible parts of capsicum,water spinach and amaranth in Soil A decreased 0.1%-94.0%,6.3%-32.7%,20.5%-37.3%,respectively;Cd contents decreased 68.2%-98.6%,3.9%-12.8%,6.9%-30.1%,respectively;Cu contents decreased 79.3%-84.3%,17.7%-81.7%,33.1%-58.9%,respectively;and Zn contents decreased 4.4%-27.0%,14.5%-85.9%,20.3%-81.9%,respectively.Pb contents in edible parts of capsicum,water spinach and amaranth in Soil B decreased 28.4%-91.0%,37.0%-55.9%,15.6%-35.6%,respectively;Cd contents decreased 9.2%-59.2%,27.7%-47.6%,7.1%-40.7%,respectively;Cu contents decreased 81.7%-93.6%,0.2%-50.1%,15.2%-42.2%,respectively;and Zn contents decreased 23.3%-89.4%,2.6%-31.6%,4.6%-11.2%,respectively,as a result of 2 g-kg-1 to 8 g-kg-1 addition of HZ.Two combined amendments LS and HZ reduced contents of heavy metals in vegetables to some extent,and the contents of Pb and Cd in edible parts of capsicum,water spinach and amaranth were lower than the Tolerance Limit of Contaminants in Foods of China National Standards,when addition of LS and HZ was 8.g-kg-1.(6)Application of LS and HZ decreased contents of Pb,Cd,Cu and Zn in vegetables,and also gradually reduced the bioaccumulation factor(BCF)and translocation factor(TF)of heavy metals in vegetables from root to straw and from straw to grain.Different organs of vegetable had different abilities of accumulation and translocation heavy metals.The accumulation abilities of Pb,Cd,Cu and Zn in three vegetables(capsicum,water spinach,and amaranth)ranked as follows:Cd>Cu>Zn>Pb.The translocation factors of Cu and Zn in capsicum from root to straw,from straw to leaf and from straw to grain were always greater than those of Pb and Cd,but the translocation factors of Pb,Cd,Cu and Zn in water spinach and amaranth from root to straw ranked as follows:Cd>Zn>Cu>Pb.The highest translocation factor of Pb,Cd,Cu and Zn in the three vegetables was from straw to leaf,and this rank was the same with increasing amounts of LS and HZ.(7)The hazard quotient(HQ)for Pb and Cd in capsicum,water spinach and amaranth in Soil A was greater than 1,indicating a higher health risk.However,application of LS and HZ made the HQ for Pb and Cd in these three vegetables became lower than 1,implying there was no health risk.The HQ for Pb and Cd in capsicum and water spinach in Soil B was greater than 1,showing no health risk;but the HQ for Pb and Cd in amaranth was greater than 1,suggesting a higher health risk.Application of LS and HZ could reduce the HQ for Pb and Cd in amaranth to less than 1.The health risk for heavy metals in leafy vegetable was generally higher than melon and fruit vegetables,suggesting that melon and fruit vegetables with lower contents of Pb and Cd in their edible parts were more suitable for planting in these two local contaminated area Soil A and Soil B,and combination of LS and HZ applying and melon and fruit vegetables planting could reach the aim of decreasing the health risk of Pb and Cd for the local people via vegetables. |
PDF Full Text Request