【作者】 姜冠杰；

【导师】 胡红青；

【作者基本信息】 华中农业大学 ， 土壤学， 2011， 博士

【摘要】 土壤中的铅不能被生物分解或化学降解,只能通过渗漏进入地下水,或直接被植物吸收进入食物链,最终对生态环境及人类和动物的健康造成严重的危害。本文研究了在黄褐土、砖红壤和潮土中施加磷矿粉后铅形态变化,探讨了磷矿粉施加量、培养时间、不同磷矿粉种类以及活化磷矿粉对土壤中铅形态的影响,采用X射线衍射(XRD)、X射线光电子能谱(XPS)、傅立叶变换红外光谱(FT-IR)以及扫描电镜和能谱分析(SEM/EDS)等手段分析了草酸活化磷矿粉与未活化磷矿粉在不同pH条件下对铅的钝化机理。主要结果如下：1)黄褐土和砖红壤中施加钟祥磷矿粉(ZPR)培养2d后,均能有效的减少土壤中交换态铅含量,增加残渣态铅含量,且磷矿粉施加量越高,效果越显著。随着磷矿粉施加量由0mgP/kg,50mg P/kg,500mg P/kg,2000mg P/kg增加,黄褐土和砖红壤中交换态铅含量与对照相比降低22.5%-54.4%和61.7%-72.8%；外源铅含量为200mg/kg时,两土壤中交换态和残渣态铅变化规律与无外源铅污染时相似,随磷矿粉施加量增加,黄褐土和砖红壤中交换态铅比对照减少23.9%-86.0%和20.9%-90.2%,以在ZPR用量最大时(2000mg P/kg)钝化效果最好。污染潮土中施加钟祥磷矿粉2d后,交换态铅含量有增加趋势,但增幅很小,交换态铅含量百分比变化范围为0.7%-1.3%,残渣态铅含量增加。2)外源铅污染的黄褐土和砖红壤设置为轻度污染(Y2、L2)与重度污染土壤(Y4、L4),向其中施加2000mg P/kg的ZPR后,其交换态铅含量随时间增加先表现很小的增幅,而后趋于稳定,而残渣态铅含量随时间增加先减少后增加；潮土中残渣态铅含量随时间增加而增加,增幅为1.3%-14.5%。3)黄褐土中施加不同用量的磷矿粉后,保康磷矿粉(BPR)钝化交换态铅效果最好,开阳磷矿粉(KPR)最差；而砖红壤中对交换态铅的钝化效果为,低磷矿粉用量时(50mg P/kg),ZPR钝化效果最好,BPR最差；中(500mg P/kg)、高(2000mg P/kg)磷矿粉用量时,BPR效果最好,KPR最差。两土壤施加不同用量的四种磷矿粉后,均能显著的减少土壤中交换态铅含量,增加残渣态铅含量。但供试磷矿粉对土壤中铅的钝化效果不同,BPR效果最优,ZPR和南漳磷矿粉(NPR)效果相当,KPR次之。说明磷矿粉的全磷和有效磷含量并非是钝化土壤中铅的决定因素,很可能由于BPR具有较大的比表面积,在对铅的钝化过程中磷酸盐诱导的吸附起主要作用。4)黄褐土中施加不同用量的活化磷矿粉(APRs)后,交换态铅含量,在低APRs用量时,活化保康磷矿粉(ABPR)效果最好,活化开阳磷矿粉(AKPR)最差；中APRs用量时,活化南漳磷矿粉(ANPR)效果最好,AKPR最差；高施加量时,检测不到交换态铅。砖红壤中无论低、中、高APRs用量,ABPR的钝化效果均优于其它三种APRS。两土壤中施加四种不同用量的APRs后,部分处理残渣态铅含量减少。四种APRs均能显著降低两土壤中交换态铅含量,效果优于PRs。说明磷矿粉被草酸活化后,释放的有效磷增多,能够与铅接触的机会增多。5)供试未活化磷矿粉(PRs)和草酸活化后的磷矿粉(APRs)分别与不同pH的200mg Pb/L的铅溶液反应,在pH3.0-5.0范围内均有效吸附溶液中的铅,溶液的pH≥3时,对铅的吸附率均在90%以上。随着溶液pH的降低,溶液中溶解的磷浓度升高,但不同pH对Pb的吸附影响很小。通过XRD分析表明,供试样品均可检测到氟磷灰石和方解石衍射峰。草酸活化后,均可检测到草酸钙或水合草酸钙。PRs与铅溶液反应后形成白铅矿,APRs与铅反应后生成磷氯铅矿。XPS表面分析通过对Pb4f的终结合能(135.05-135.55eV)对比显示,APRs对铅的去除要比PRs的更有效。SEM/EDS分析表明供试PRs样品包含大的块状结晶体并含大量的Ca,P,O,F和C,验证了氟磷灰石的存在；PRs经草酸活化后,变为无定形；PRs与铅溶液反应后,形成块状物质并含有Pb；在APRs与铅溶液反应后,形成不规则的块状粒子,同时检测到Pb。FT-IR图谱表明,在PRs被草酸活化后,C032-的特征吸收峰消失,P043-的峰强度减弱,同时出现C2O42-的特征吸收峰。表明CO32-在PRs与Pb溶液的反应中起主要作用,而APRs中P043-起主要作用。由于磷氯铅矿的溶解度低,建议采用APRs钝化土壤和水中的铅。更多还原

【Abstract】 Lead in soil will percolate into ground water or enter the food chain by plant absorbing, instead of being decomposed by living organisms or degraded through chemical methods, hence doing severe harm to the health of human beings and animals and the ecology environment. In this study, changes of Pb forms in yellow cinnamon soil, latosol and meadow soil after being added with phosphorus rocks (PRs) were determined and the effects of PRs addition amount, incubation time and kinds of PRs on Pb forms in the soils were studied, to study the immobilization mechanism of activated and inactivated PRs to Pb under different pH conditions using the means of X-ray diffraction (XRD), X ray photoelectron spectrum (XPS), Fourier Transform Infrared (FTIR) and scanning electron microscope with X-ray energy dispersive spectroscopy (SEM/EDS), etc. The main results are described below.1) For both the yellow cinnamon soil and the latosol after being added with Zhongxiang PR for2days, the exchangeable Pb content decreased effectively while the residue Pb content increased, which was positively correlated with the PR addition amount. Compared with the control experiment, the exchangeable Pb content in yellow cinnamon soil decreased from22.5%to54.4%, while the decreasing range of exchangeable Pb content in latosol was61.7%-72.8%, with the increase of the PRs amount from0mg P/kg,50mg P/kg,500mg P/kg to2000mg P/kg; when the exogenous Pb content was at200mg/kg, the exchangeable and residue Pb contents in the two soils showed a similar result to the condition that the soils were not Pb pollution, and the exchangeable Pb content decreased from86.0%to23.9%for yellow cinnamon soil,90.2%-20.9%for latosol, reaching the optimum immobilization effect with the PR addition amount of2000mg P/kg. After the contaminated meadow soil was added with Zhongxiang PR for2days, its residue Pb content tended to rise, and the reduction range of its exchangeable Pb content was only0.7%-1.3%.2) The yellow cinnamon soil and the latosol polluted by exogenous lead were set as light pollution (Y2, L2) and heavy pollution (Y4, L4) soils respectively. After they were added with Zhongxiang PR of2000mg P/kg, as time went by, their exchangeable Pb contents increased slightly first and then tended to be stable, while the residue Pb contents revealed contrary trend; the increasing range of the residue Pb content in meadow soil was1.3%-14.5%.3) After four kinds of PRs were added into the yellow cinnamon soil and the latosol, the exchangeable Pb content in the soils was reduced remarkably and the residue Pb content increased. The immobilization effects can be summarized as follows:Baokang PR (BPR) was the best, Zhognxiang PR (ZPR) was not better than Nanzhang PR (NPR), and Kaiyang PR (KPR) was inferior to others. Although KPR contains the most amount of total and available phosphorus, it showed the worst effects to immobilize Pb in soils, which proved that the total and available phosphorus contents in PRs were not the determinants in the immobilization process, and most probably for the reason that high specific surface area of PRs could absorb Pb2+4) Different amount activated PRs (APRs) was added into the yellow cinnamon soil, the changes of exchangeable Pb contents were:with low APRs addition amount, the effect of activated Baokang PR (ABPR) was the best and activated Kaiyang PR (AKPR) was the worst; with medium APR addition amount, the effect of activated Nanzhang PR (ANPR) was the best while AKPR was worse than others; when the APR addition amount was high, little exchangeable Pb was detected. Whatever APR amount was applied to the latosol, ABPR showed the best immobilization effect among all the APRs. After different kinds and amount APRs were added to the two soils, some of the residue Pb content was reduced. The exchangeable Pb content in both the soils decreased remarkably after being added with four APRs, and the effects was much better than that with PR, which demonstrated that PRs could release more available phosphorus and provide more opportunities to react with Pb after activated by oxalic.5) Reacting with200mg Pb/L Pb solution with different pH, both the PRs and the PRs activated by oxalic (APRs) could absorb Pb effectively with the pH of3.0-5.0; and when pH≥3, the Pb adsorption rate was over90%. With the solution pH deceased, more phosphorus was dissolved but pH had a little effect on Pb adsorption. XRD analysis showed that clearly defined fluorapatite and calcite peaks could be observed in all samples. The formation of weddellite or whewellite was observed in all samples after treatment with oxalic. The presence of cerussite was detected in all raw PRs reacting with the Pb solution, whereas the peaks of pyromorphite were observed in all APRs. XPS surface analysis confirmed that the Pb removal was more efficient with APRs than PRs by comparing the end BE of Pb4f(135.05-135.55eV). The SEM/EDS indicated that the tested sample of raw PR powders contained large agglomerate crystals containing a significant amount of Ca, P, O, F and C, which proved the existence of fluorapatite; after PR was treated with oxalic acid, the original cluster crystal structures were changed to amorphous; a mass was formed after raw PR reacted with the Pb solution; after the oxalic acid-treated PR reacted with the Pb solution, anomalous block shaped particles and Pb was observed. The FT-IR spectra showed that after PR was activated by oxalic acid, the absorption patterns of CO32-disappeared, peak intensity of PO43-decreased greatly, and corresponding characteristic absorption patterns of C2O42-began to appear. It suggested that CO32-played a key role in the reaction between PR and Pb solution, while PO43-determined the reaction between APR and lead solution. APRs were recommended as an adsorbent to immobilize Pb in soils and remove Pb from aqueous solution because of the low solubility of pyromorphite.更多还原