河口沉积物硫的地球化学特征及其与铁和磷的耦合机制初步研究

	河口沉积物硫的地球化学特征及其与铁和磷的耦合机制初步研究
	孙启耀
学位类型	博士
导师	盛彦清
	2016-05-30
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	环境科学
关键词	河口无机硫铁和磷耦合机制
其他摘要	无机硫化物是沉积物中最活跃的硫形态之一，其地球化学循环过程与沉积物中铁、磷及部分金属元素的地球化学行为密切相关，其氧化还原过程等迁移转换过程能够在一定程度上直接影响沉积物中铁和磷的形态、活性及其环境行为。入海河口往往是陆源污染入海的最后一道屏障，同时也是典型的生态敏感区和环境脆弱带，因此探究重污染河口沉积物中无机硫化物的地球化学特征及其与铁和磷的耦合机制，对于近海及全球的硫铁磷循环机制的认识与调控具有重要的意义。本文选取中国北方典型海岸带重污染河口-烟台鱼鸟河河口不同类型沉积物为研究对象，按照不同季节采用薄膜扩散梯度技术（DGT）等原位分析技术调查了河口沉积物中溶解性S^2-、Fe²⁺和溶解态活性磷酸盐（DRP）的时空分布特征及其动态扩散过程，充分认识了这些沉积物孔隙水中S-Fe-P三者之间极为显著的相互制约或促进机制。本研究同时结合沉积物粒度、有机质和固相无机硫化物、活性铁和磷形态及无机硫化物与活性铁和磷形态之间的相关性等数据，对重污染河口沉积物中无机硫化物的地球化学特征及其与铁和磷循环的耦合机制进行了深入探讨，进一步明确了沉积物中S-Fe-P的循环耦合机制。除此之外，本研究还通过模拟实验，基本掌握了模拟自然潮汐的海水浸没和淡水浸没过程的方法，并对潮汐交替对重污染河口沉积物中硫铁磷地球化学循环的影响进行了定量表征。本文主要得到如下结论：（1）对鱼鸟河河口沉积物中溶解性S^2-的时空分布特征及其动态扩散过程的研究结果表明，鱼鸟河沉积物富含有机质，且泥质沉积物中有机质含量显著高于砂质沉积物，有机质的分布主要受细颗粒组分控制。活性有机质是鱼鸟河沉积物硫酸盐还原的控制因素，泥质沉积物硫酸还原作用显著高于砂质沉积物。沉积物表层和次表层硫酸盐还原作用较强，随深度降低硫酸盐还原作用减弱。潮间带沉积物富含可利用性硫酸盐和活性有机质，硫酸盐还原速率较高。淡水沉积物缺少可利用性硫酸盐，硫酸盐还原速率较低，沉积物中溶解性S^2-维持相对稳定的平衡状态。（2）鱼鸟河河口沉积物中无机硫化物的时空分布特征和转化机制的研究结果表明，鱼鸟河河口沉积物硫酸盐还原作用较强，还原性无机硫化物（RIS）在沉积物表层和次表层以酸可挥发性硫化物（AVS）为主，而在沉积物深处则以黄铁矿（CRS）为主。AVS和溶解性S^2-之间具有显著的相关性，即AVS中溶解性S^2-含量较高，表明鱼鸟河河口沉积物无机硫化物的活性和生物毒性较高。低黄铁矿化度（DOP）和高AVS/CRS值表明活性铁氧化物是硫酸盐还原产物H₂S向FeS转化的主要限制因素，而元素硫（ES）是AVS向CRS转化的主要限制因素。无机硫化物地球化学循环受季节性变化影响显著，夏秋季节高温促进硫酸盐的还原，从而使溶解性S^2-和AVS积累量增加；冬春季节低温限制硫酸盐的还原，导致溶解性S^2-和AVS积累量降低。夏季沉积物中ES含量和黄铁矿化程度显著高于冬季，且黄铁矿化主要以多硫化方式进行。（3）由鱼鸟河河口沉积物中溶解性Fe²⁺和活性铁的时空分布特征得知，河口沉积物中溶解性Fe²⁺和活性铁的含量较低。较高的硫化程度（DOS）表明积物中铁主要以FeS或FeS₂为主，铁的硫化程度极高。活性铁氧化物是鱼鸟河河口沉积物硫酸盐还原产物H₂S向FeS转化的主要限制因素。铁的异化还原过程和化学还原过程同时存在，但以化学还原为主，即硫酸盐还原产生的H₂S优先还原铁氧化物生成稳定的黄铁矿，限制了无机硫化物和铁的活性。（4）由鱼鸟河河口沉积物中溶解态活性磷酸盐（DRP）和磷形态的时空分布特征得知，鱼鸟河沉积物中的磷以铁结合态磷（Fe-P）和有机磷（OP）为主，两者占总磷含量的80%以上，可交换态磷（Ex-P）和钙磷（Ca-P）的含量较低。冬季Fe-P和OP的含量显著高于夏季，硫酸盐还原和铁氧化物还原是鱼鸟河沉积物Fe-P季节性变化的主要控制因素，微生物的活性则是沉积物OP季节性变化的主要控制因素。（5）通过对鱼鸟河河口沉积物无机硫化物循环与铁和磷的循环耦合机制的初步研究的结果表明，重污染河口富含活性有机质和可利用性硫酸盐，硫酸盐还原速率较高，硫酸盐还原产物H₂S使活性铁氧化物发生化学还原，生成FeS或FeS₂，限制了无机硫化物和铁的活性。随着铁氧化物的还原溶解，被铁氧化物吸附固定的磷酸盐重新释放。由于潮汐交替过程中存在盐度差，导致河口沉积物-上覆水之间溶解性物质交换扩散通量升高，溶解性磷酸盐由沉积物扩散迁移至上覆水体中，提高了水体中磷的生物可利用性，增加了河口和近海水体富营养化的风险。 ; Inorganic sulfide is one of the most active sulfur forms in sediments. The geochemical cycling of inorganic sulfide is closed related to the geochemical behavior of iron, phosphorus and heavy metals in sediments. Its transformation processes such as the oxidation-reduction, have directly effects on the form, activity and environmental behavior of iron and phosphorus in sediments. Estuary is the last barrier to prevent land-based pollutants from being washed into the sea and is typical ecologically sensitive region and environmental fragile zone. Therefore, studies on the geochemical characteristics of sulfide and its coupling mechanism with iron and phosphorus cycles in estuarine sediments is very significant for understanding the mechanism of sulfur, iron and phosphorus cycles on coastal and global scale. In this dissertation, we chose different types of sediments in the Yuniao River estuary as study objects characterized by heavy pollution in the northern China. The spatial and temporal variations of distributions of dissolved S^2-, Fe²⁺ and dissolved active phosphates (DRP) and their dynamic diffusion process were systematically studied by the diffusive gradients in thin-films technique (DGT). The results indicated that the interactional and promoting mechanisms of S-Fe-P were remarkable. In this study, the geochemical characteristics of sulfide and its coupling mechanism with iron and phosphorus cycles in heavily polluted coastal sediments were deeply investigated by combining the data of date of the grain sizes, organic matter, solid inorganic sulfide, active iron, phosphorus forms and the correlations among them for further understanding the coupling mechanism of S-Fe-P cycles. A simulation experiment of tidal process was conducted for understanding the immersion process of seawater and fresh water in natural tide, and for quantifing the influence of tide on the geochemical cycles of sulfur, iron and phosphorus in heavily polluted estuarine sediments. Major results are as follows: （1）The spatial and temporal distributions of sulfide and its dynamic diffusion process were studied in estuarine sediment of the Yuniao River. The results showed that a large amount of organic matters existing in the sediments were controlled by fine particles. The content of organic matter in the muddy sediments was obviously higher than that in sandy sediments. Sulfate reduction was controlled by the organic matters which concentrations were much higher in the mud sediments than those in sandy sediments. The rate of sulfate reduction was relatively higher in the surface and subsurface sediments and gradually decreased with depth. Due to the available sulfate and active organic matter sediments were rich in the intertidal sediments, the rate of sulfate reduction was relatively high. Because of the lower content of available sulfate, sulfate reduction rate was relatively low in freshwater sediments and the dissolved S^2- maintained a relatively stable equilibrium. （2）The spatial and temporal distributions of inorganic sulfide and its transfer mechanism were studied in the estuarine sediments of the Yuniao River. We found that the sulfate reduction rate was relatively high in the sediment. Reducing inorganic sulfide (RIS) acid existed as volatile sulfide (AVS) in the surface and subsurface sediments, while the RIS was pyrite (CRS) in the deep sediment. Significant correlation between dissolved S^2-and AVS was found, indicating that AVS was dominated by dissolved S^2-, and the activity and biological toxicity of inorganic sulfide was very high in the sediment of the Yuniao River. Low degree of pyritization (DOP) and high ratio of AVS/CRS suggested that the active iron oxide was the major control factor of conversion from H₂S to FeS, while the elemental sulfide (ES) was the major control factor of conversion from AVS into CRS. The geochemical cycling of inorganic sulfide was significantly influenced by seasonal cycle. The accumulation of dissolved S^2- and AVS increased in summer and autumn and decreased in winter and spring caused by temperature related sulfate reduction. The value of DOP and content of ES in summer were obviously higher than those in winter, and the multi-sulfofication was the main pathway of the pyritization. （3）The spatial and temporal distributions of active iron and dissolved Fe²⁺ were investigated in the estuarine sediments of the Yuniao River. The results showed that the concentrations of active iron and dissolved Fe²⁺ were low in estuarine sediment of the Yuniao River. The high degree of sulfidization (DOS) indicated that FeS and FeS₂ were the dominant iron form in the sediments and the degree of sulfidization of iron was extremely high. The activity of iron oxide became the main factor controlling conversion of H₂S to FeS. Although the dissimilatory iron reduction and the chemical iron reduction existed simultaneously, the process of iron reduction was dominated by chemical iron reduction. （4）The spatial and temporal distributions of dissolved active phosphate (DRP) and phosphorus speciation were studied in the estuarine sediments of the Yuniao River. Our results showed that the iron phosphorus (Fe-P) and organic phosphorus (OP) were the main speciation of phosphorus, accounting for more than 80% of total phosphrus, while the contents of exchangeable phosphorus (Ex-P) and calcium bound phosphorus (Ca-P) were relatively low. The contents of Fe-P and OP in winter were significantly higher than those in summer. The seasonal variations of Fe-P were obviously influenced by sulfate reduction and iron reduction while the microbial activity played an important role in seasonal variations of OP. （5）The results of geochemical cycle of inorganic sulfide and the coupling mechanism of S-Fe-P cycles in estuarine sediments of the Yuniao River showed that the heavy polluted estuarine sediments were rich in available sulfate and organic matter, and the sulfate reduction rate in it was very high. The H₂S, generated by sulfate reduction, could react with iron oxide to form FeS and FeS₂and which limit the activity of iron and inorganic sulfide. Phosphate was released from absorption and fixed by iron oxide. Due to the salinity difference during the tidal alternation, the exchange diffusion fluxes of dissolved S^2-, Fe²⁺ and DRP increased between the overlying water and sediment, resulting in promotting the migration and diffusion of phosphate from sediment to the overlying water and the biological availability of phosphorus, indicating that the risk of eutrophication increased in the coastal area.
语种	中文
文献类型	学位论文
条目标识符	http://ir.yic.ac.cn/handle/133337/13831
专题	中国科学院烟台海岸带研究所知识产出_学位论文
作者单位	中国科学院烟台海岸带研究所
第一作者单位	中国科学院烟台海岸带研究所
推荐引用方式 GB/T 7714	孙启耀. 河口沉积物硫的地球化学特征及其与铁和磷的耦合机制初步研究[D]. 北京. 中国科学院大学,2016.

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