| Heavy metals contamination in soils and road-deposited sediments is becoming hore and more serious while economy is developing quickly. The related problems have been focused by people. Besides transporting in soil-plant system and influencing growth of plant as well as safety of agricultural product,heavy metals in contaminated soils can also be transported to waterbody(including surface waterbody and ground waterbody) by surface runoff, leaching and so on. Water quality of waterbody and environment is influenced consequently.Soil matters can be transported and deposited on road in different ways,and heavy metals in road-deposited sediments can also be transported again to waterbody with surface runoff in proper conditions. The aim of this study was to learn about release potential, transportation law, influencing factors for the release of heavy metals in soil and road-deposited sediment,as well as methods for characterizing the release potential of heavy metals and decreasing the release potential of soil heavy metals. By analyzing samples,simulating experiment and observing in fields,potential influence on waterbody of accumulation of heavy metals in soils and road-deposited sediment was researched. Accordingly,the release and transporting law of heavy metals as well as the relation between release,tran-sporting and soil properties were researched. Furthermore,amendment methods for immobilizing heavy metals were researched. The obtained preliminary results are meaningful for assessing risk of heavy metals in soils and road-deposited sediment to waterbody as well as founding characterizing method based on water quality saftety and controlling the harm of soil heavy metals to waterbody. The main results and conclusions were:1Sixteen paddy soils were collected and a one year indubating experiment was conducted by adding Cd and Pb to them. Release behavior of Cd and Pb in contaminated soils was assessed by determining water-soluble and exchangeable Cd and Pb. The results showed that the percentage of water-soluble and exchangeable Cd and Pb usually increased while the content of Cd and Pb in soil increased. Without adding Cd.the average percentage of water-soluble and exchangeable Cd in total Cd were0.16%and7.24%,respectively. In the treatment of adding Cd by0.2?0.5?1.0?2.0and5.0mg·kg-1,the percentage of water-soluble Cd were0.14%?0.25%?0.34%?0.50%and0.81%,respectively,and the percentage of exchangeable Cd were10.73%?11.61%?14.11%?12.55%and10.67%,respectively. Without adding Pb,the average percentage of water-soluble and exchangeable Pb were0.006?and0.70%,respect-ively. In the treatment of adding Pb by20.0,50.0?100.0?200.0and500.0mg· kg-1, the percentage of water-soluble Pb respectively were0.008%?0.014%?0.027%?0.036%and0.047%, and the percentage of exchangeable Pb were1.03%?1.71%?2.67%?3.74%and3.84%,respectively. The increasement of water-soluble and exchangeable Cd and Pb with accumulation of soil Cd and Pb varied greatly in different soils. Relation analysis showed that water-soluble Cd and Pb mainly were related with the pH and base saturation; whereas, exchangeable Cd and Pb mainly were related with pH,base saturation,CEC and texture. The increasement of water-soluble and exchangeable Cd and Pb were lower in soils with high pH,CEC,base saturation and in more clayey soils,and the release potential of Cd and Pb can be decreased more greatly in the soils. The effect of decreasing mobile speicies of Pb is bigger than that of Cd.2Five different land-use zones (industrial, residential, commercial, park, and countryside) were selected in Hangzhou,and25road-deposited sediments were collected. The concentrations of heavy metals (Cd,Co,Cr,Cu,Fe,Mn,Ni,Pb and Zn) in these samples were determined, and chemically fractionated according to the BCR (the European Community Bureau of Reference) sequential extraction procedure. According to the enrichment factor(EF),there were anthropogenic pollution sources,concerning Cu?Cd?Pb and Zn. The high heavy metal concentration levels were detected in the samples from industrial zone and commercial zone which were influenced by heavy traffic,and so on. While the concentrations of the heavy metals were lower in the samples from residential zone,park and countryside zone. Based on the BCR sequential extration procedure Zn,Cd,Cu and Pb were more mobile and had more threat to waterbody.In addition,sixty-three representative sites of paddy field, orchard,vege-table land, nursery and urban land in north Zhejiang plain were selected. Surf-ace runoff were collected, and water-soluble Cd,Co,Cr,Ni,Pb,Cu,Zn,Mn and Fe in the runoff samples were determined. Surface soil samples were also collected in the corresponding sites. Total heavy metals and water-soluble heavy metals were determined by extracting with0.01mol·L-1CaCl2. The results showed that the co-ncentrations of heavy metals in the runoff samples varied greatly. The water-soluble mean values for Cd?Co?Cr?Ni?Pb?Cu?Zn?Mn and Fe respectively were0.19.0.46?1.04?1.73?4.98?88.47?184.52?609.52and1135.21?g·L-1, and Cu? Zn?Pb had bigger threat to waterbody envrionment. Land use change had an impact on the concentrations of water-soluble heavy metals in runoff samples. Maximum concentrations of Cd,Co,Cr,Ni,Pb and Zn were present in the runoff from urban area, whereas those of Mn and Fe were present in the runoff from paddy field. However, orchard land had the highest concentration Cu of runoff. The results showed that the release capacity of heavy metals is related with land use. The concentrations of water-solube heavy metals in the runoff had significantly negative correlation with pH.and significantly(or dramatically siginificantly) positive correlation with total content and water-soluble heavy metals of the corresponding soils. CaCl2-extractable heavy metals can better represent the release potential of heavy metals in surface runoff,compared with the total content. There were more heavy metals which can run off with surface runoff and threaten waterbody quality when heavy metals were concentrated in the soils, especially when mobile heavy metals were increased.3Thirteen undisturbed soil columns in different contamination level were collected using PVC tubes. The soil columns were leached by deionized water in10mm·h-1simulating rainfall for one time. The amount of the leachate was50mm. The results showed that the percentage of water-soluble Cu, Cd, Pb and Zn in total amount were25.25%,47.52%,15.45%and35.65%, respectively. Most concentrations of water- soluble heavy metals were lower than particulate heavy metals. Water-soluble, particulate and total Cu,Cd,Pb and Zn were negatively correlated with bulk density. Water-soluble, total Cu,Cd,Pb and Zn usually were highly significant with pH. Particulate Cu,Cd,Pb and Zn were not significantly correlated with pH. Water-soluble, particulate and total Cu,Cd,Pb and Zn were negatively correlated with calcium carbonate,clay particles,organic carbon and CEC. The results indicated that soil heavy metals were leached mainly in particulate phase. Bulk density, pH,CEC,clay-particles and organic carbon were important properties which can influence leaching phase of soil heavy metals.For researching the influence of the treatment of adding oranic material and acidifing on species and release potential of soil heavy metals,one soil samples contaminated by Cu,Cd,Pb,Zn and Cr was collected.The organic material was added in4levels:0?50?100and200g·kg-1. The acidification included control and decreasing pH to6,5,4. The soil was leached after incubating for1year. The leaching experiment was conducted for17d. The samples were leached1time every4d,and were leached5times totally. They were leached by50mm deionized water. The results showed that soil pH respectively decreased from7.1to7.0,6.8,6.8,6.7after adding0,50,100,200g·kg-1organic material without acidifing. The results indicated that accumulation of organic material can decrease soil pH slightly. The percentage of exchangeable heavy metals could increased apparently while pH decreased, especially for Cd,Zn. Pb and Cu in the leachates increased by46%-128%compared to the contol.when pH decreased to6.0,and Cd,Zn increased by219%-630%,and Cr increased by10%-119%. Cu,Cd,Pb,Zn and Cr in the leachates respectively increased by165%-555%,156%-940%,196%-475%,214%-746%and70%-444%compared to the control,when pH decreased to5.0. When pH decreased to4.0,the concentrations of heavy metals of every treatments reached to very high level. It was showed that acifification could increase acitivity and release of heavy metals. Effect of organic matter accumulation on release potential of heavy metals was related with soil pH and degree of organic matter accumulation. When pH was relatively high, low level accumulation of organic matter can increase the release of heavy metals,and high level accumulation of organic matter can decrease the release of heavy metals. However,when pH was relatively low,accumulation of organic matter can decrease the release of heavy metals. It is concluded that pH and organic matter content are important factors which influence release potential of soil heavy metals. The influence of organic materials accumulation and acidification created by afforestation when afforestation is implemented for amending contaminated soils on release potential of soil heavy metals should be concerned.4Immobilizing effects of6mineral amendments(apatite, agricultural limestone,palysorskite,Ca-Mg-P fertilizer,zeolite and Fe(OH)3) to heavy metals in2contaminated urban soils (including a acidic soil and a calcareous soil),and4mineral amendments (kaolinite.bentonite, zeolite and apatite) to heavy metals in one Pb-contaminated agricultural soil were studied by incubating experiments, and so on. Sorption-desorption experiment showed that the6mineral amendments could strongly adsorbed Cu,Cd,Pb and Zn. The adsorption rates were more than97.2%. The6mineral amendments had strong adsorption ability for heavy metals as the remained heavy metals retained on the minerals were still more than96.8%after2times of desorption.The Amacher sequential extraction procedure showed that the exchangeable heavy metals were gradually transformed to more stable carbonate-bound,oxide-bound and residual heavy metals after appling the6amendments,and the transformation varied with different amendments. The sequence of decrease level of exchangeable heavy metals was Ca-Mg-P fertilizer, palysorskite>Fe(OH)3, zeolite> agricultural limestone>apatite. It was showed that amendments could apparently reduce water-soluble heavy metals extracted with0.02mol·L-1CaCl2. The effect on the acidic soil was apparently better than the effect on the calcareous soil. Compared to the control,water-soluble Cu,Cd,Pb and Zn respectivley were decreased by21-53%,18%-35%,22%-47%and16%-33%,with adding amendments in the calcareous soil. Compared to the control,water-soluble Cu,Cd,Pb and Zn respectively were decreased by36%-68%?33-59%?41-69%and33-62%with adding amendments in the acidic soil. The effect for decreasing water-soluble heavy metals was best for Ca-Mg-P fertilizer,palygorskite and apatite. The amendments could apparently decrease mobility of the heavy metals. It is feasible to immobilize Cu,Cd,Pb,Zn and decrease release potential of heavy metals with the6mineral amendments.The results showed that.adding amendments also could reduce mobile Pb (water-soluble and exchangeable Pb) in Pb-contaminated agricultural soil app-arently. The effects were related with amendments type,applied amount and the size of the amendments. In the treatment of adding Pb (added amount is100mg· kg-1), after adding kaolinite.bentonite,zeolite or apatite a-nd incubating for100d,water-soluble Pb decreased respectivley by38.11%-49.70%,64.33%-71.34%,73.48%-83.23%,83.84%-90.24%,and exchangeable Pb decreased by25.45%-36.99%,53.29%-60.13%,64.42%-70.02%,76.19%-80.26%,compared to the control. The sequence of the effects for decreasing mobile Pb in Pb-contaminated agricultural soil of the minerals was:apatite>zeolite>Bentonite>kaolinite. The immobilizing eff-ect of the minerals sieved with100#mesh was apparently better than the min-erals sieved with18#mesh. The reduction of water-soluble Pb by adding the m-inerals was bigger than the reduction of exchangeable Pb. The release potenti-al of Pb in the contaminated agricultural can be effectively decreased,by us-ing the minerals. In the contaminated soil with lower level of Pb,recommended amount of minerals for amending soil is20g·kg-1... |
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