YIC-IR  > 中国科学院烟台海岸带研究所知识产出
滨海河流沉积物的典型重金属质量基准确定及 Cd 污染原位修复研究
刘群群
Subtype博士
Thesis Advisor盛彦清
2021-05
Training institution中国科学院烟台海岸带研究所
Degree Grantor中国科学院大学
Place of Conferral中国科学院烟台海岸带研究所
Degree Name工学博士
Degree Discipline环境工程
Keyword滨海河流 沉积物 重金属 环境质量基准 原位修复
Abstract沉积物是水生生态系统重金属迁移转化重要的源和汇。近年来,沉积物重金属污染已经成为一个亟待解决的全球性环境问题。目前,我国河流沉积物重金属污染形势不容乐观,时刻威胁着水生生态系统及人体健康的安全。因此,重金属污染沉积物的有效管控迫在眉睫。然而,我国尚没有相应的河流沉积物环境质量基准或标准对沉积物重金属污染进行有效的监管与评价,重金属有效治理的技术研究也相对滞后。鉴于上述现状,本研究分别从重金属污染沉积物的评估和治理两个角度,探究基于改进的相平衡分配法建立流域尺度沉积物重金属环境质量基准(SQG)的可行性,再结合质量基准开展了Cd污染沉积物的原位修复技术研究,以期为重金属污染沉积物的有效管控提供科学依据。主要研究结果如下: (1)滨海河流沉积物典型重金属质量基准的确定:以胶莱河(JL)和夹河(JH)沉积物为研究对象,并结合地表水水质标准(GB 3838-2002),建立了流域尺度的Cd、Cu、Pb和Zn沉积物环境质量基准。此外,还探究了两条河流沉积物和间隙水中重金属的空间分布、赋存形态、分配系数和环境风险。结果表明,JH沉积物中重金属含量高于JL,而间隙水中重金属含量则呈相反趋势。重金属赋存形态分析表明,沉积物中大部分重金属以残渣态为主。重金属在沉积物和间隙水中的分配主要受沉积物和间隙水性质以及外源重金属输入的影响。污染因子法分析表明,JH和JL沉积物大部分站位Cd呈高或极高污染水平;间隙水标准毒性单位和Nemerow指数表明,两条河流沉积物大部分站位间隙水单一重金属均不会对生物产生毒性。结合地表水水质标准改进的间隙水水质标准,采用改进的相平衡分配法建立了流域尺度的重金属SQG。可以发现,流域尺度的重金属SQG可以合理地对不同水功能区的沉积物进行不同等级的划分。基于SQG的沉积物重金属评价结果表明,两条河流沉积物重金属的潜在生物毒性效应较低。由此可见,依据不同的水功能区划而建立流域尺度的重金属SQG是可行的。 (2)不同材料负载纳米零价铁前后对Cd污染沉积物的原位固定修复:采用沸石、海泡石、赤泥(RM)和生物炭(BC)负载纳米零价铁(nZVI)后,然后将它们用于Cd污染沉积物的原位固定修复(90 d),并探究了修复后沉积物理化性质、Cd稳定性和细菌群落的变化。实验结果表明,修复后沉积物理化性质发生了显著改变(P < 0.05);与对照组相比,处理组沉积物Cd弱酸溶解态占比减少了11%~47%,而残渣态占比增加了50%~1000%,Cd稳定性得到提高。在4种原材料中,RM和BC对Cd污染沉积物的固定化效果明显高于海泡石和沸石;特别地,相对于原材料而言,改性材料对Cd的固定化效率更高,浸出毒性比原材料修复下降低了15%~22%。固定化修复提高了沉积物细菌群落的丰富度和多样性。在所有材料中,nZVI/RM和nZVI/BC的修复效果最好;相比于对照组,其浸出毒性分别下降了42%和44%。此外,固定化修复还可以通过增加Fe(III)还原细菌和硫酸盐还原菌的丰度来分别促进Fe(III)和硫酸盐的还原,从而有利于沉积物Cd的固定。总体来看,BC(nZVI/BC)对沉积物Cd的固定化效果好,且对沉积物的不良影响小,可作为Cd污染沉积物固定修复的首选材料。 (3)nZVI/BC和BC原位固定修复Cd污染沉积物的效率及细菌响应:为探究修复时间和修复剂量对BC和nZVI/BC修复效果的影响,采用不同剂量BC和nZVI/BC对沉积物Cd进行了更长时间的原位固定(140 d),研究了BC和nZVI/BC对沉积物Cd稳定性和细菌群落的影响,并探讨了它们在不同pH值下的修复效果。结果表明,施用BC和nZVI/BC可使沉积物Cd向上覆水和间隙水的释放分别降低了31%~69%和26%~73%。与对照组相比,修复后沉积物Cd的稳定性得到提高,Cd浸出毒性降低了7%~29%。这直接证明了原位固定修复后沉积物Cd对上覆水和间隙水的风险降低,沉积物Cd的生态风险下降。这说明经过一段的修复时间后,沉积物Cd可能会满足相应的重金属SQG。Cd可移动性的降低与BC或nZVI/BC的添加剂量密切相关,呈现剂量依赖性。值得注意的是,在所有pH值处理下,nZVI/BC对沉积物Cd释放的抑制效果明显优于BC。在碱性条件下,BC和nZVI/BC的修复效果明显优于酸性和中性条件。细菌群落分析表明,低剂量的修复材料提高了细菌群落的丰富度和多样性;但是,由于沉积物理化性质的变化和修复材料毒性的影响,施用高剂量的修复材料会对沉积物细菌群落产生不利影响。 (4)BC负载纳米Fe2O3原位覆盖Cd高度污染沉积物的效率:由于nZVI复合材料合成成本较为昂贵,且固定化修复见效较慢;因此,进一步采用了BC和BC负载的纳米Fe2O3(nFe2O3@BC)原位覆盖Cd高度污染沉积物,并探究了BC和nFe2O3@BC的覆盖性能、适用条件和修复机理。结果表明,覆盖60 d后,BC和nFe2O3@BC均一定程度上抑制了Cd从沉积物向上覆水和间隙水的释放(抑制效率> 99%),表明沉积物Cd对间隙水和上覆水造成的风险经原位覆盖后降低。在上覆水所有不同pH和干扰强度处理下,nFe2O3@BC覆盖的效果均优于BC覆盖。特别地,低pH值和高水力扰动均会削弱BC和nFe2O3@BC原位覆盖的效果。鉴于Cd的高毒性,不适合在酸性和中性水体(pH = 3、5和7)中使用BC原位覆盖Cd污染沉积物,而在所有pH处理组中均可使用nFe2O3@BC覆盖。BC和nFe2O3@BC覆盖在高水力干扰下(搅拌速度= 150 rpm)会失效,但nFe2O3@BC覆盖在低水力干扰下(搅拌速度= 0和100 rpm)仍然有效。薄膜扩散梯度技术的分析结果表明,BC和nFe2O3@BC覆盖均抑制了沉积物Cd向间隙水的释放。在BC(98.74%)和nFe2O3@BC(98.10%)覆盖层中吸附的大部分Cd可能会重新释放到水体中,因此需要及时处理覆盖层。另外,过量使用nFe2O3@BC作为覆盖材料可能会增加Fe释放的风险。
Other AbstractSediment acts as an important source and sink of heavy metals in aquatic ecosystem. In recent years, heavy metal pollution in sediments has become a global environmental problem that needs to be handled. At present, the pollution of heavy metals in sediments in China is not optimistic, threatening the safety of aquatic ecosystems and human health. Therefore, the effective controlling of heavy metals polluted sediments is very imminent. However, there is no river sediment environmental quality guidelines (or standards) to effectively supervise and evaluate heavy metal pollution in sediment until now, and research on effective treatment methods of heavy metals contaminated sediments is also relatively backward. In view of the above situation, from the perspectives of evaluation and remediation of heavy metal pollution in sediments, this study firstly explored the feasibility of the establishment of heavy metal environmental quality guidelines for river sediments (SQG) combined with modified equilibrium partitioning approach, and then carried out in-situ remediation of Cd polluted sediments combined with SQGs, aiming to provide scientific basis for the effective controlling of heavy metals contaminated sediments. The major findings are as follows: (1) Determination of quality guidelines for typical heavy metals in coastal river sediments: Taking sediments from Jiaolai River (JL) and Jiahe River (JH) as the research objects, the environmental quality guidelines of heavy metals (Cd, Cu, Pb and Zn) in sediments at watershed scale were established combining with the surface water quality standard (GB 3838-2002). Additionally, the spatial distribution, speciation, partition coefficient, and environmental risk of heavy metals in sediment and interstitial water in the two rivers were also studied. The results exhibited that the contents of heavy metals in sediments in JH were higher than those in JL, while the contents of heavy metals in interstitial waters showed a opposite trend. The speciation analysis of heavy metals showed that most heavy metals in the sediments were dominated by residual speciation. The distribution of heavy metals in sediments and interstitial water was mainly influenced by the properties of sediment and interstitial water, and the input of exogenous heavy metals. The results of contamination factor presented that Cd in sediments from JL and JH exerted a high or very high contamination level. The heavy metals in sediment interstitial water in most sites presented no toxicity to aquatic organisms according to the interstitial water criteria toxicity units and Nemerow index. Based on the interstitial water quality standards modified by surface water quality standards, the SQG of heavy metals at watershed scale were calculated by the modified EqPA. It can be found that SQG at watershed scale can reasonably classify the sediments of different water function areas into different grades. Heavy metals in sediments exerted a low potential toxicity of the two rivers in view of SQG. Totally, it is feasible to establish SQG of heavy metals at watershed scale according to different water function regionalization. (2) In-situ immobilization of Cd contaminated sediments using different materials loaded with nano-zero-valent iron: zeolite, sepiolite, red mud (RM), and biochar (BC) were performed to load nano-zero-valent iron (nZVI), and then used for in-situ immobilization of Cd polluted sediment (90 d). The physicochemical properties, remediation efficiency, and bacterial community of the sediments after the immobilization were explored. The experimental results showed that the sediment properties significantly changed after immobilization (P < 0.05). The proportions of weak acid soluble speciation of Cd in the treated sediments were reduced by 11% to 47% compared to the control; conversely, and the proportions of residual speciation were increased by 50% to 1000%, indicating the Cd stability was enhanced. Among the four raw materials, the immobilization effects of RM and BC on Cd contaminated sediments were significantly higher than those of sepiolite and zeolite. In particular, the modified materials possessed higher immobilization efficiencies for Cd in sediments, and the leaching toxicities were reduced by 15%~22% compared with the raw material treatments. The remediation efficiencies of nZVI/RM and nZVI/BC were the best among all the materials, and their leaching toxicities were reduced by 42% and 44%, respectively, compared with the control. Immobilization treatment improved the richness and diversity of bacterial communities in sediments. In addition, the reductions of Fe(III) and sulfate were promoted by enhancing Fe(III) reducing bacteria and sulfate reducting bacteria after immobilization treatment, advancing the Cd immobilization in sediments. Overall, BC (nZVI/BC) could be considered as the most ideal materials for the immobilization of Cd polluted sediments due to them showed better immobilization effects and little adverse effects on sediments. (3) Efficacies and microbial responses of BC and nZVI/BC during in-situ immobilization of Cd contaminated sediments: To explore the effects of time and dose on the remediation efficacies of BC and nZVI/BC, BC and nZVI/BC with different doses were used to immobilize Cd polluted sediments in situ for a longer time (140 d). The remediation efficiencies of BC and nZVI/BC under different pH values and responses of bacterial communities in sediments were studied. The results showed that Cd releases in overlying water and interstitial water were decreased by 31%~69% and 26%~73% with BC and nZVI/BC treatments compared to the control, respectively. Moreover, the Cd stability in the sediments was strengthened after treatment, and the leaching toxicities in treated groups were reduced by 7% to 29%. This directly proved that the risk of sediment Cd to overlying water and interstitial water was limited after in-situ immobilization, and the ecological risk of sediment Cd was reduced. It can be seen that after a period of remediation time, Cd in sediments may meet the corresponding SQG. The increase of Cd stability was intimately linked to the dosage of BC or nZVI/BC, showing a dose-dependent manner. Notably, at different pH values, nZVI/BC showed a higher inhibitory efficiency than BC on the release of Cd from the sediment. Under alkaline conditions (pH = 9), both BC and nZVI/BC presented the higher remediation efficiencies compared to those in acidic and neutral conditions. Application of low-dose remediation materials increased the abundance and diversity of bacterial communities. However, high-dose remediation materials posed some adverse effects on bacterial communities because of the changes of sediment properties and toxicites of BC and nZVI/BC. (4) In-situ capping of Cd highly contaminated sediments by BC loaded with nano-Fe2O3: Due to the high cost of nZVI composite and the slow effect of immobilization, BC and nano-Fe2O3 modified BC (nFe2O3@BC) were further performed to cover Cd-contaminated sediments in situ. The performances, applicable conditions, and mechanisms of BC and nFe2O3@BC capping were investigated. The results showed that both BC and nFe2O3@BC capping partly inhibited Cd release from sediment to overlying water (reduction rates > 99%) after 60 d capping. This indicated that the risk of sediment Cd to interstitial water and overlying water was reduced after in-situ capping. Under all different pH and interference intensity treatments of the overlying water, the effect of nFe2O3@BC capping is superior to those of BC capping. Notably, both low pH value and high hydraulic disturbance could lower the effect of BC and nFe2O3@BC in-situ capping. Given high toxicity of Cd, BC capping was inapplicable in acidic and neutral water bodies (pH = 3, 5, and 7), while nFe2O3@BC capping was available in all pH treatments. Both BC and nFe2O3 were ineffective under high hydraulic disturbance (stirring speed = 150 rpm), but nFe2O3@BC still worked in low hydraulic disturbance (stirring speed = 0 and 100 rpm). The analysis of diffusive gradient in thin films showed that BC and nFe2O3@BC capping inhibited Cd release from sediment to porewater. Notably, most adsorbed Cd in BC (98.74%) and nFe2O3@BC (98.10%) capping layers was potential to be re-released into water bodies. Therefore, it is necessary to treat the covering layer in time. Additionally, excessive application of nFe2O3@BC capping could increase the risk of Fe release.
Pages152
Language中文
Document Type学位论文
Identifierhttp://ir.yic.ac.cn/handle/133337/34388
Collection中国科学院烟台海岸带研究所知识产出
Recommended Citation
GB/T 7714
刘群群. 滨海河流沉积物的典型重金属质量基准确定及 Cd 污染原位修复研究[D]. 中国科学院烟台海岸带研究所. 中国科学院大学,2021.
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