【作者】 王碧玲；

【导师】 谢正苗；

【作者基本信息】 浙江大学 ， 水资源利用与保护， 2008， 博士

【摘要】 土壤中有害重金属积累到一定程度，不仅会导致土壤退化、农作物产量和品质下降，而且可能直接毒害植物或通过食物链途径危害人体的健康。上虞市东关镇银山畈有一万多亩铅锌矿污染土壤和农作物特别是蔬菜受到了严重的铅（Pb）污染和中度的锌（Zn）污染。因此，研究含磷（P）物质修复铅锌矿污染土壤和蔬菜的机理，解决该修复技术中的一些根本性的基础科学问题及关键技术，具有重要的理论和实用意义，对浙江省经济和社会可持续发展和生态省建设将起积极作用。论文在评述矿区重金属污染现状和含磷物质原位修复污染土壤研究进展的基础上，以铅锌矿污染土壤为研究对象，借助X-射线衍射分析技术（XRD）和模型MINTEQ研究了含P物质原位修复污染土壤中Pb的主要机制，通过实验室模拟、盆栽以及田间小区实验，采用重金属形态分级、毒性淋溶提取（toxicity characteristicleaching procedure，TCLP）以及植物吸收等方法对含P物质（包括磷酸二氢钾、过磷酸钙、钙镁磷肥、磷矿粉）原位修复铅锌矿污染土壤的效果进行评估，获得如下主要成果：（1）采用X-射线衍射分析技术，从矿物学的角度研究了水和土壤环境中P-Pb相互作用机理，为后续铅锌矿污染土壤的有效修复研究提供理论依据。结果表明，添加P和Pb或者P、氯（Cl）和Pb溶液处理后，膨润土的XRD图谱有明显的新特征峰生成，经过物相鉴定，添加P和Pb处理后主要是生成了羟基磷酸铅盐化合物[Pb₁₀（PO₄）₆（OH）₂，PH]和磷酸氢铅盐化合物[PbHPO₄，HP]，而添加P、Cl和Pb处理后，主要是生成了氯磷酸铅盐化合物[Pb₅（PO₄）₃Cl，ClP]。添加P处理后，污染土壤的XRD图谱中有新生成的衍射峰出现，经过物相鉴定，这些衍射峰主要是氯（羟基）磷酸铅盐化合物的特征峰。上述结果说明P处理后，Pb污染环境中容易生成溶解度极低的氯（羟基）磷酸铅盐化合物，并可控制Pb的活性。理论上P可应用于铅污染土壤的修复。（2）结合Visual MINTEQ模型考察了P和Cl对铅锌矿污染土壤中Pb的生物有效性的影响。结果发现，在铅锌矿污染土壤中添加水溶性P化合物磷酸二氢钾KH₂PO₄（MPP）后，显著（p＜0．05）降低了土壤中Pb的水溶-交换态含量，降低幅度为92％～95％，显著降低了Pb的生物有效性。在相同P添加量水平时，加Cl与不加Cl比较，显著降低了土壤中Pb的水溶-交换态含量，表明添加Cl对含磷物质降低铅毒有促进作用。运用模型Visual MINTEQ计算的结果证实，添加P和Cl处理土壤后，土壤中Pb的活度主要受P的控制，尤其是氯磷酸铅盐化合物[pyromorphite，Pb₅（PO₄）₃Cl]。在使用含P物质修复Pb污染土壤技术时，添加适量的Cl，以达到最佳修复效果。（3）实验室条件下，研究了pH和P对土壤淋洗液中重金属Pb、Zn含量的交互影响以及Ca、P及pH对土壤淋洗液中重金属Pb、Zn含量的交互影响。结果表明，环境pH显著（p＜0．05）影响了MPP与污染土壤中的重金属Pb、Zn的相互作用，并且在6．0～7．4的pH环境下，MPP对Pb、Zn含量的降低效果最理想。如果同时添加碱性物质和过磷酸钙（SSP）把土壤pH调到6．5～7．5，可以使SSP修复Pb、Zn的效果达到最佳（降低幅度分别高达68％和94％）。添加P的同时添加不同Ca、pH以及P对Pb、Zn含量的交互影响分析发现，中性环境中Ca（0．03～0．60Ca／Pb摩尔比的Ca用量）促进了P对Pb／Zn的固定作用，并且Ca／P的摩尔比例为0．4～1．0（Ca剂量是0．24～0．60 Ca／Pb摩尔比，P用量是0．6 P／Pb摩尔比）时，铅锌复合污染土壤中水溶性Pb、Zn的活性同时地、最大程度地被钝化。（4）用Tessier连续分级提取法研究了不同含磷物质（磷肥）对铅锌矿污染土壤中Pb和Zn化学形态的影响。结果表明，磷矿粉（PR）、过磷酸钙（SSP）和钙镁磷肥（CMP）等3种磷肥都具有显著（p＜0．05）降低Pb的各种非残渣形态含量的作用。在P／Pb摩尔比例为7的磷肥用量水平时，从非残渣形态Pb总量的降低幅度上看，3种磷肥修复铅污染的效果顺序为：SSP（85％）、CMP（83％）＞＞PR（16％）；把Pb的形态与其生物有效性联系起来比较，3种磷肥修复Pb污染效果顺序为：CMP（94％）、SSP（92％）＞PR（61％）。结果同时显示，PR、CMP显著降低了土壤中Zn的水溶态（49％～77％）、交换态（65％～96％）、有机结合态含量（19％～35％），而SSP在降低交换态和有机结合态含量的同时增加了水溶态Zn的含量。磷肥具有原位修复铅锌矿污染土壤的潜能。3种磷肥中以磷矿粉最为经济。（5）设了0，0．6，1．2，1．8，3．0，4．0 P／Pb摩尔比等6个P剂量水平梯度，温室条件下采用TCLP、水溶以及交换态提取法评估了不同种类和水平的含P物质对铅锌矿污染土壤中重金属Pb、Zn生物有效性的影响，并参照国际标准探讨足够控制重金属毒性到限制标准以内的P用量水平。结果表明，SSP和MPP都具有显著（p＜0．05）降低土壤交换态和TCLP提取Pb含量的作用，降低TCLP含量的幅度大小顺序是：MPP（66％～93％）＞SSP（26％～69％）。MPP处理的P剂量水平在0．6、SSP处理在1．2～1．8区间时，一个月内就足以把土壤中TCLP Pb的含量降低到国际限制标准(5 mg·L^-1)以内，修复铅毒。结果同时表明，MPP对土壤中Zn的TCLP含量无显著影响，而SSP在显著降低了交换态含量的同时，微量增加了TCLP含量，但都远低于国际的限制标准(25 mg·L^-1)。各种有效性Zn（TCLP、水溶性、交换态）的含量均与土壤pH显著负相关，说明即使添加了含P物质处理，土壤中Zn的活性主要还是受土壤pH控制。上述结果进一步说明了含P物质具有显著降低铅锌矿污染土壤中Pb环境风险的作用。（6）在前一章的基础上，缩小P用量水平（P／Pb摩尔比）范围，设为：0、0．18、0．36、0．72、1．08、1．44，温室条件下开展了MPP对污染土壤中Pb、Zn和Cd在土壤固相-液相之间以及土壤-根系-地上部的迁移累积影响的研究。结果表明，与对照相比，添加MPP处理污染土壤后，显著（p＜0．05）降低了空心菜地上部吸收Pb、Zn和Cd的含量，降低幅度分别为53％～92％、35％～71％和59％～86％；降低了根系吸收累积重金属Pb的含量，增加了根系吸收的Zn的含量，但对Cd吸收量无显著影响。增加P的剂量水平，由根系向地上部转运的Pb、Zn和Cd的量的呈指数级下降趋势。地上部吸收的各元素的相关分析结果表明，Pb与Zn、Cd呈显著正相关，其中相关系数最高的是Pb与Zn（r=0．993，p＜0．01），其次是Pb与Cd（r=0．986，p＜0．01），说明Pb与Zn、Cd在空心菜从根系到地上部分转运的过程中是协作关系。添加MPP后，提高了土壤pH，从而降低了土壤水溶性Cd的含量；Zn变化不显著，但增加了土壤水溶性总Pb含量。模型Visual MINTEQ计算结果表明，土壤平衡液中Pb的主要存在形态是PbHPO₄、PbOH⁺、PbH₂PO₄⁺等3种络合形态。重金属土壤含量与植物吸收量的相关分析结果表明，根系吸收Pb的量与土壤水溶性Pb含量呈显著的负相关，相关系数为-0．872（p＜0．05）。含P物质具有显著降低复合污染土壤中Pb、Zn和Cd植物毒性的作用。（7）在田间条件下，以青菜（上海青，Brassica campestris L．chinensis）为指示植物，结合XRD、重金属形态分级、TCLP、土壤无机磷形态分级法，研究了3种磷肥包括SSP、CMP和PR修复铅锌矿污染土壤的田间示范效果，同时探讨了磷肥对铅锌矿污染土壤的修复机理。实验结果表明，磷肥显著（p＜0．05）降低了Pb的非残渣态含量（34％～64％）、植物吸收量（16％～58％）和TCLP提取量（25％～59％），并且在0．8 P／Pb摩尔比的P用量水平时，CMP和SSP处理六个月后土壤中Pb的TCLP量低于国际限制标准。XRD分析发现，土壤中有新的氯（羟基）磷酸铅盐化合物[Pb₁₀（PO₄）₆（OH／Cl）₂]、含铁的磷酸铅化合物[PbFe₃（SO₄）（PO₄）（OH）₆]和含钙的磷酸铅化合物[Ca_2.5Pb_7．5（OH）₂（PO₄）₆]生成。CMP和PR显著（p＜0．05）降低了Zn的各种非残渣态含量（27％～79％）、植物吸收量（39％～73％）和TCLP提取含量（4％～39％）。SSP处理在降低Zn的植物吸收量（1％～12％）的同时，增加了TCLP提取量，但都远低于国际限制标准。进一步的相关分析表明，Ca₈-P是降低土壤重金属Pb、Zn的生物有效性即水溶-交换态、植物吸收量、TCLP Pb、Zn含量的磷的主要形式。上述结果说明了田间条件下磷肥具有显著修复铅锌矿污染土壤中重金属Pb毒的作用，其修复机理是通过在土壤中形成氯（羟基）磷酸铅盐化合物和Pb-P-Ca/Fe化合物。（8）田间条件下，结合XRD、TCLP和土壤无机磷形态分级法从时间的角度探讨了磷肥SSP、CMP和PR修复铅锌矿污染土壤效果的稳定性。XRD图谱分析结果表明，氯（羟基）磷酸铅盐化合物和Pb-P-Fe化合物的衍射特征峰的峰强逐渐增加，说明随着反应时间的延长，土壤中这两种新生成的化合物的量在不断增加。土壤TCLP评价结果表明，磷肥处理后随着反应时间的延长，土壤中重金属Pb的毒性逐渐降低，并且在处理时间为24个月时，3种磷肥处理均能将TCLP Pb降低到国际限制标准以下，这与XRD分析结果相吻合。上述结果表明，随着处理时间的延长，磷肥原位固定修复中国铅锌矿污染土壤的田间效果是稳定的。从长远和经济的角度考虑，3种磷肥中PR是最经济有效的修复材料，建议推广使用。更多还原

【Abstract】 Heavy metal such as lead （Pb）is toxic to humans,especially young children,and toanimals.Metal-contaminated soil is a primary source of metals exposure to youngchildren.One of the primary sources of metals contamination is industrial activityincluding mining tailing,leading to metals accumulation in the soils and risk to human’shealth through soil ingestion and the food chain such as vegetables.The previous reportby our research group showed that there were thousands hectares of soil and plant heavilycontaminated by Pb and Zn in Shangyu,Zhejiang Province,China.Therefore,increasingawareness of the hazard that heavy metals can cause to humans make it necessary toremediate metal contaminated soils.This dissertations aimed to understand the mechanism of phosphorus （P）inducedlead immobilization in the soil contaminated by Pb/Zn mining tailings in Shangyu,Zhejiang Province,China,to assess the effects on the toxicity and bioavailability of Pband Zn after P application,and to figure out the most cost-effective P source and itsapplication rate,using X-ray diffraction （XRD）,model MINTEQ,toxicity characteristicleaching procedure （TCLP）,sequential extraction procedure,and plant indicator.Themain experiments and conclusion are as follows:（1）XRD pattems were analyzed to observe the mineralogy of P with orwithout chlorine （Cl）induced Pb immobilization in water and soil environment.It wasfound that occurrence of pyromorphite [Pb₅（PO₄）₃Cl,ClP] and lead phosphate hydroxide[Pb₁₀（PO₄）₆（OH）₂,PH] was evident in the treated bentonite each for P addition with orwithout Cl 24 hours later.Furthermore,pyromorphite like compounds were alsoidentified in the P treated soils one month later.It was determined that the primarymineralogy of P induced Pb immobilization was through pyromorphite like compoundsformation after P addition.Therefore,it was theoretically proved to apply P materials for remediation of soil which was contaminated by Pb/Zn mining tailings in Shangyu,Zhejiang Province,China.（2）Effect of chlorine （Cl）on in situ lead immobilization using phosphorus ina soil contaminated by lead and zinc mining tailings was evaluated.The results showedthat water soluble and exchangeable Pb was reduced by 92.0 %～95.1% in the soil after Papplication.It was also suggested that application dosage of phosphorus at the P / Pbmolar ratio of 0.6,was enough to remediate Pb toxicity in the soil.Compared to withoutCl treatment at the level of molar ratio of 0.6 P / Pb,water soluble and exchangeable Pbin the soil treated with Cl was reduced markedly.It was concluded that the effectschlorine addition on in situ lead （Pb）immobilization using phosphate were improved.Visual MINTEQ model was employed to figure out Pb and P species distribution andsaturation indices for minerals in the soils treated by P and Cl.The results showed that Pbactivity was controlled by lead phosphate in the soil,especially pyromorphite[Pb₅（PO₄）₃Cl],which would be the reason for Pb bioactivity reduction in the soil afterapplication of Cl and P.The effective Pb bioactivity reduction indicated that addition ofCl was necessary to improve in situ lead immobilization using phosphorous in thelead-contaminated soil.（3）The objective of this work was to evaluate the efficiency of calcium （Ca）,pH,and phosphorus on the leachability of Pb and Zn in the contaminated soil.It wasfound out that the effects of phosphorus on the leachability of Pb and Zn wassignificantly affected by pH,and pH of 6.0～7.4 would be the best condition for metalimmobilization by phosphorus.It was worthwhile to noted that there would be a biggestreduction of Pb and Zn leachability （up to 68 % and 94 %）when the condition pH wasadjust to 6.5～7.5 after SSP application,and that would be useful for in situ technique.Itwas evidently that Zn was mobilized by Ca treatments with various pH conditions,but noPb.In neutral condition,the bioavailability of Pb and Zn in the contaminated soil couldbe synchronously farthest reduced after combined used of Ca and P with a 0.4～1.0 mole ratio of Ca/P application rate.（4）The effects of three phosphorus fertilizers （single superphosphate-SSP,calcium magnesium phosphate-CMP,and phosphate rock-PR）on chemical fractions oflead （Pb）in a soil contaminated by Pb/Zn mining tailings using a sequential extractionprocedure were evaluated.All three phosphorus fertilizers reduced Pb solubility andbioavailability effectively.It was suggested that application rate of phosphorus fertilizersat the level of 7.0 molar ratio of P / Pb,was enough to remediate Pb toxicity in the soil.At the level of 7.0 molar ratio of P / Pb,the effect of Pb remediation by phosphorusfertilizers followed the order in terms of the sum of decreased nonresidual fractions:SSP（85 %）≈CMP （83 %）＞＞PR （16 %）.If linking up chemical fractions of Pb in soil withits bioavailability,the effect of Pb remediation by three phosphorus fertilizers followedthe order:CMP （94 %）≈SSP （92 %）＞PR （61%）.Meanwhile,all three phosphorusfertilizers treatments effectively transformed soil Zn from water soluble （excluding SSP）,exchangeable,and organic fractions to the residual fraction relative to the control.PR wasthe most economic amendment in terms of the most bioavailable （exchangeable）fractionof Pb （up to 79 %）,and Zn （up to 66 %）in soil.It was suggested that the effectiveconversion of Pb and Zn from potentially available fractions to the residual fractionindicated a potential of phosphorus fertilizers for in-situ Pb immobilization in soilscontaminated by Pb/Zn mining tailings.（5）A pot experiment was conducted to evaluated the effects of P amendmentson the toxicity and bioavailability of Pb and Zn in a soil contaminated by mining tailingsusing toxicity characteristic leaching procedure （TCLP）and water soluble,exchangeableleaching procedure,and to find out the appropriate application rate to reduced the soilTCLP Pb to below the EPA regulatory limit level.The results showed that TCLP Pbconcentrations were significantly decreased by up to 93.3 % for MPP treatments and upto 68.5 % for SSP treatments after P application,and the dose required to reduceleachable Pb below the EPA regulatory limit level was found to be around the molar ratio P/Pb=0.6 for MPP and 1.8 for SSP.Both MPP and SSP were found to reduce theexchangeable Pb and Zn concentrations,but variable in water soluble Pb and Zn.It wassuggested that all bioavailable Zn concentrations including water soluble,exchangeable,and TCLP in soil were significantly negative correlated to soil pH values,which mayindicate that the activity of Zn in the soil was mostly controlled by soil pH value evenafter P application.These results suggest that P as MPP and SSP successfully decreasedthe toxicity and bioavailability of Pb and Zn in the contaminated soil.（6）A pot experiment was conducted to determine the influence of phosphorus（P）application on the translocation and accumulation of lead （Pb）,zinc （Zn）,andcadmium （Cd）in a soil solid-liquid-plant system using a plant Swamp Morningglory（Ipomoea aquatica,Forsk）as indicator and Visual MINTEQ model.A contaminated soilcontaining 22830 mg·kg^-1Pb,746 mg·kg^-1Zn,and 10 mg·kg^-1Cd was amended with P asKH₂PO₄ at 0:1,0.18:1,0.36:1,0.72:1,1.08:1,and 1.44:1 P:Pb mole ratios.The resultsshowed that Pb concentration in the root was significantly decreased after P application,while the Zn concentration were increased,but no impact on Cd concentration after Papplication,compared to the control.Further more,concentrations of Pb,Zn,and Cd inplant tissue were sharply reduced after P application by 53 %～92 %,35 %～71%,and 59%～86 %,respectively;Concentrations decreased exponentially with increasing amount ofP;Relationship between Pb and Zn （r=0.993,p＜0.01）,between Pb and Cd （r=0.986,p＜0.01）suggested that there was a positive relationship between the mechanismscontrolling the phytoavailability of Pb,Zn,and Cd.It was suggested that Cdconcentrations in the soil solution were reduced generally by P application as a result ofthe increased soil pH,and Zn concentrations were no changed,but Pb concentrationswere increased.Species distribution showed that PbHPO₄,PbOH⁺ and PbH₂PO₄⁺ werethe main complexation species of Pb in the soil equilibrium solution after P application.Itwas also suggested that Pb accumulation by root were negatively correlated to Pb in soilsolution with coefficient of-0.872 （p＜0.05）,and that water soluble Zn and Cd concentrations were reduced while the concentrations in root tissues were increased afterP addition.These results indicate the difference between Zn,Cd and Pb and suggest thatP as KH₂PO₄ successfully decreased the phytotoxicity of Pb,Zn,and Cd in thecontaminated soil.（7）A field demonstration was conducted at a mining tailings-contaminatedsite to assess the effectiveness of P-induced Pb immobilization using XRD,TCLP,sequential extraction procedure,inorganic P fractionation procedure,and cabbage（Brassica campestris L.chinensis）as a plant indicator.Three phosphorus fertilizers（single superphosphate-SSP,calcium magnesium phosphate-CMP,and phosphaterock-PR）were applied as P amendments in the field demonstration.Lead immobilizationwas attributed to the P-induced formation of pyromorphite like compounds[Pb₁₀（PO₄）₆（OH/Cl）₂] and Pb-P-Ca/Fe compounds,which were identified in the treatedsoils.It was found that the addition of all three P fertilizers significantly decreased thepercentage of non-residual fraction （by 34 %～64 %）and TCLP （7 %～59 %）soil Pb,andthen reduced the uptake of Pb （16 %～58 %）by the cabbage compared to the control （CK）.In addition,at a 0.8 molar ratio of P / Pb application rate,SSP and CMP treatmentsreduced TCLP Pb to below EPA regulatory limits level in the soils.The results showedthat the concentration of Zn in non-residual fraction （by 27 %～79 %）,TCLP （4 %～39 %）,and plant uptake （39 %～73 %）were significantly reduced after CMP and PR application.Zn concentrations in plant uptake （1%～12 %）were decreased after SSP application,while the TCLP concentrations were slightly increased,which were far below the EPAregulatory limits level.Results of regression analysis indicated that Ca₈-P was theprimary form of P fertilizers to decrease the bioavailability of Pb and Zn in the soil-plantsystem.Therefore our field trial demonstrated that it was effective and feasible to reducePb,Zn availability in soil and cabbage contaminated by mining tailings using P fertilizersin China.（8）The objective of this study was to assess the stability of P-induced lead immobilization in the field scale using XRD,TCLP,and inorganic P fractionationprocedure.Lead immobilization was attributed to the P-induced formation ofpyromorphite like compounds [Pb₁₀（PO₄）₆（OH/Cl）₂] and Pb-P-Ca/Fe compounds,whichwere identified in the treated soils.Intensity of those peaks was increased along with theincreasing of treated time from 1 m to 6 m～24 m.It was found that there was an increasein TCLP Pb reduction along with the increasing of treated time from 1 m to 6 m～24 m,and that all three P fertilizers reduced TCLP Pb concentration in the treated soils to belowthe EPA regulatory limits level 24 months after P fertilizers application,which stronglydemonstrated that it was stable for P-induced lead and zinc immobilization in thecontaminated soil in the field.It was concluded that PR was the most cost-effectivematerial for lead immobilization considering both its long-term effectiveness and price.更多还原