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

发布时间：2018-05-02 12:06

本文选题：河口 + 无机硫　；参考：《中国科学院烟台海岸带研究所》2016年博士论文

【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-)、Fe~(2+)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Fe~(2+)和活性铁的时空分布特征得知,河口沉积物中溶解性Fe~(2+)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FeS_2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H_2S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H_2S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H_2S使活性铁氧化物发生化学还原,生成FeS或FeS_2,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。
[Abstract]:Inorganic sulfide is one of the most active sulfur forms in the sediments. Its geochemical cycle is closely related to the geochemical behavior of iron, phosphorus and some metal elements in the sediments. The transformation process, such as redox process, can directly affect the form, activity and environmental behavior of iron and phosphorus in the sediments. The sea mouth is often the last barrier of land source pollution to the sea, and it is also a typical ecological sensitive zone and environmental fragile zone. Therefore, it is important to explore the geochemical characteristics of inorganic sulfide and the coupling mechanism of iron and phosphorus in the sediments of the heavily polluted estuary, which is important for the understanding and regulation of the mechanism of the circulation of iron and phosphorus in the near sea and the world. In this paper, the different types of sediment in the estuary of the Yantai fish bird River, the heavily polluted estuary of the typical coastal zone of northern China, were studied. The temporal and spatial distribution of dissolved S~ (2-), Fe~ (2+) and dissolved active phosphate (DRP) in the estuarine sediments was investigated by using the in-situ analysis technique of film diffusion gradient (DGT) in different seasons. This study combines sediment granularity, organic matter and solid inorganic sulfides, the form of active iron and phosphorus, and the correlation between the inorganic sulphides and the forms of the active iron and phosphorus in the sediments, and the dynamic diffusion process is fully recognized. The study is combined with the grain size, organic and solid inorganic sulphides, the form of active iron and phosphorus and the correlation between the inorganic sulphides and the forms of the active iron and phosphorus. The geochemical characteristics of inorganic sulfide and the coupling mechanism of the iron and phosphorus cycle in the sediments of the polluted estuaries are deeply discussed, and the cyclic coupling mechanism of S-Fe-P in the sediments is further clarified. The influence of the tidal alternation on the geochemical cycle of sulfur, iron and phosphorus in the sediments of the heavily polluted estuaries was quantitatively characterized. The main results were as follows: (1) the spatial and temporal distribution characteristics of dissolved S~ (2-) in the sediment of the fish and bird River Estuary and its dynamic diffusion process showed that the sediment of the fish and bird river was rich in machine and mud. The content of organic matter in the sediments is significantly higher than that of sandy sediments. The distribution of organic matter is mainly controlled by the fine particles. The active organic matter is the controlling factor of sulfate reduction in the sediment of the fish bird River, and the sulfate reduction of the muddy sediments is significantly higher than that of the sandy sediments. Low sulfate reduction. Intertidal sediments are rich in available sulfate and active organic matter, with higher sulfate reduction rate. The lack of available sulphate in freshwater sediments, low sulfate reduction rate and relatively stable S~ (2-) in sediments. (2) inorganic sulphide in the sediments of the fish bird River Estuary The spatial and temporal distribution characteristics and transformation mechanism of the sediment show that the sulfate reduction of the sediment is stronger in the estuary of the fish and bird River, and the reductive inorganic sulfide (RIS) is dominated by acid volatile sulfide (AVS) in the surface and subsurface of the sediment, while in the depth of the sediment, there is a significant difference between the.AVS and the dissolved S~ (2-) of the pyrite (CRS). The high content of dissolved S~ (2-) in AVS indicates that the activity and biological toxicity of inorganic sulfide in the sediment of the fish and bird River estuary are higher. The low pyrite salinity (DOP) and high AVS/CRS value indicate that the active iron oxide is the main limiting factor for the transformation of the sulfate reduction product H2S into FeS, and the elemental sulfur (ES) is the main restriction of AVS to CRS transformation. Factors. The geochemical cycle of inorganic sulfides is significantly affected by seasonal changes. In summer and autumn season, high temperature promotes the reduction of sulfate, which makes the accumulation of dissolved S~ (2-) and AVS increase. In winter and spring, low temperature limits the reduction of sulphate, resulting in the decrease of the accumulation of dissolved S~ (2-) and AVS. The content of ES and the degree of pyrite mineralization in the summer sediments are significant. (3) the spatial and temporal distribution of dissolved Fe~ (2+) and active iron in the sediments of the estuary of the fish and bird river has been found to be higher than that in winter. The content of dissolved Fe~ (2+) and active iron in the estuarine sediments is lower. The higher vulcanization degree (DOS) indicates that the iron is mainly FeS or FeS_2, and the degree of iron vulcanization. Active iron oxide is the main limiting factor for the conversion of sulfate reduction product H_2S to FeS in the sediment of the fish and bird River Estuary. The process of dissimilation reduction and chemical reduction of iron exists simultaneously, but the chemical reduction mainly, that is, the H_2S preferential reduction iron oxide produced by sulfate reduction, produces a stable pyrite, which restricts the inorganic sulfide. (4) the spatial and temporal distribution of dissolved active phosphate (DRP) and phosphorus in the sediments of the fish bird River Estuary showed that the phosphorus in the sediment of the fish and bird river was dominated by iron bound phosphorus (Fe-P) and organophosphorus (OP), which accounted for more than 80% of the total phosphorus content, and the content of exchangeable phosphorus (Ex-P) and calcium phosphorus (Ca-P) was lower. In winter, the contents of Fe-P and OP in the sediments were low. The amount of sulphate reduction and iron oxide reduction is the main controlling factor for the seasonal variation of Fe-P in the sediment of the yubird River, and the activity of microorganism is the main controlling factor for the seasonal change of the sediment OP. (5) through the preliminary study on the cyclic coupling mechanism of the inorganic sulfides in the sediment of the fish and bird River Estuary with iron and phosphorus The results show that the heavy polluted estuary is rich in active organic matter and available sulphate, and the rate of sulfate reduction is higher. The sulfate reduction product H_2S makes the active iron oxide chemical reduction, producing FeS or FeS_2, limiting the activity of inorganic sulphides and iron. Salt is released again. Due to the difference of salinity in the process of tidal alternation, the exchange and diffusion flux of dissolved matter between the sediment and the overlying water in the estuary is increased, and the dissolved phosphate is transferred from the sediment to the overlying water body, which increases the bioavailability of phosphorus in the water body and increases the risk of eutrophication in the estuarine and offshore waters.

【学位授予单位】：中国科学院烟台海岸带研究所
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X55;X52

【参考文献】