硫酸盐还原菌（SRB）对长江口典型植被根系重金属的固定及其生物有效性研究

发布时间：2018-01-02 01:15

本文关键词：硫酸盐还原菌（SRB）对长江口典型植被根系重金属的固定及其生物有效性研究　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：通常认为,潮滩湿地是河口系统中金属沉降的一个重要"汇"。河口地区经济发达,工业活动密集,承接有大量的城市污水处理厂排水和工业废水等,进入环境的金属最后也将汇集到河口环境中。潮汐作用下,大量金属进入潮滩湿地环境。随着植物生长,金属富集、转移至植物地上及地下组织。金属在水相、沉积物及植物的再分配现象,是生物地球化学以及生态自我修复的一个重要方面。本文在调查了 13种金属浓度在潮滩环境中时间、空间、物种以及组织间的分布基础上,结合不同形态硫、硫酸盐还原菌(SRB)在植物根系土及表层沉积物中的分布及其时间、空间分布差异,通过相关性分析研究了天然环境下植物根系土中SRB对金属的固定作用及生物有效性。最后,结合室内短期暴露控制实验,以硝酸银、纳米银为例,揭示在SRB的参与下,潮滩植被叇草根部对金属银的固定及生物有效性。本文通过对长江口 8个采样点位植物根系土中金属浓度分析,发现植物根系沉积物环境中1月份总的金属平均含量最低,4月份最高,金属Fe、Ti、Mn浓度水平均居于主导,比其它金属元素含量高2-3个数量级,金属Cd含量最低;总体来说,污水处理厂出水口附近的采样点吴淞口、石洞口以及垃圾填埋场下游废水排放口附近的采样点朝阳,金属含量最高;种间差异表现为,叇草根系沉积物中重金属的平均含量最低,Cu在芦苇根系沉积物浓度最高,其它12种重金属则在互花米草根系沉积物种累积最多;除金属锰外,植物组织中金属含量分布为:根茎叶。1月、4月植物不同组织根、茎、叶中累积金属的浓度水平,均高于7月、10月。总体来说,叇草、芦苇不同组织中金属元素在石洞口、吴淞口累积较多,互花米草不同组织中金属含量则是在吴淞口、东海农场较高。扫描电镜表征植物组织中颗粒形态、大小,结果显示三种植物不同组织中吸附的颗粒多种多样,尺寸、形态不一,有圆形、四边形、长条形,颗粒多以多个元素组成的团聚体的形式出现,这也说明纳米金属颗粒广泛存在于河口植被环境。本文通过对8个采样点位植物根系沉积物、表层沉积物中不同形态硫分析,发现叇草.根系沉积物环境.中不同形态硫含量分布为.SO42S酸可挥发性硫。(AVS);根系沉积物环境中SRB的丰度分布为根系沉积物表层沉积物;时间分布上,4月份SRB的丰度、不同形态硫浓度水平均为最高;空间上看,污染较为严重的样点如吴淞口、朝阳农场等,其浓度水平相对高于其它点。通过对天然环境下叇草根系土中重金属与SRB丰度相关性分析,结果表明以APS-a为靶标基因定量SRB丰度时,除Fe外,其余12种重金属均与SRB丰度显著相关,以APS-b为靶标基因定量SRB丰度时,只有元素Mn、Pb与SRB丰度显著相关,这表明SRB在某种程度上可以有效的去除根系沉积物环境中的金属。也存在一些样点如浏河口、七丫口,SRB丰度越高,SO42-含量越低,这很有可能就是SRB将硫酸盐还原表现出来的结果。扫描电镜表征结果显示,因SRB的参与AgN03处理组营养液中形成了金属硫化物颗粒,颗粒尺寸大小也是随暴露浓度的升高而增大。不论是Ag+暴露组,还是Ag NPs暴露组,SRB参与均使得营养液中残留的Ag含量低于其对照组。四个不同实验暴露处理组,植物组织根、茎中均累积了大量的银离子,且植物组织中累积的Ag浓度均随着时间的推移、暴露浓度的增加而增加,其中Ag+处理实验组,植物组织中累积Ag的浓度水平最高。对Ag+处理组而言,SRB的参与使得植物根、茎中累积的Ag低于其对照组;对AgNPs暴露实验组而言,SRB的参与使得植物根、茎中累积的Ag高于其对照组。然而,实验结果表明SRB的参与否,对叇草组织中Ag的传输因子并没有表现出显著影响,总体上来说,除Ag+与SRB暴露组外,其余3个暴露实验组,不同暴露时间的TF值随着暴露浓度的增加而降低。扫描电镜表征说明暴露后叇草根、茎中均附着Ag颗粒,但叇草茎的顶端却没有发现颗粒,这可能是因为短期极性暴露,银颗粒向上传输较慢。酶消解暴露后叇草组织,经SP-ICP-MS分析,结果表明植物组织中累积了大量的AgNPs,且颗粒尺寸小于60nm,这与SEM表征结果一致。综上所述,就室内暴露试验而言,SRB的参与的确对Ag+暴露实验组植物根系环境中的Ag起到了固定作用,而AgNPs实验组中SRB并没有对Ag表现出显著固定作用,这可能与实验周期、颗粒尺寸大小、根系分泌物等均有关联,关于这点仍需日后继续探讨。
[Abstract]:Generally, the intertidal wetland is the settlement of metal estuarine systems an important sink. Estuary area developed economy, intensive industrial activities, to undertake a large number of city wastewater and industrial wastewater into the environment, finally will also converge to the metal in estuarine environment. Under the effect of tide, a large number of metal into the tide the beach wetland environment. With the growth of plants, metal enrichment plants transferred to the ground and underground organization. Metal in water, sediments and redistribution of plants, biological geochemistry and ecological restoration is an important aspect. This paper investigated 13 kinds of metal concentrations in the tidal environment in time and space distribution. Based on the species and between organizations, with different forms of sulfur, sulfate reducing bacteria (SRB) distribution and time in root soil and sediments in plants, the differences of spatial distribution, based on correlation analysis study Plant root soil natural environment in SRB of metal fixation and biological effectiveness. Finally, combined with the indoor exposure control experiment, using silver nitrate, silver nanoparticles were revealed in a SRB, the grass root of beach vegetation cloudy sky silver fixing and biological effectiveness. This article through to the Yangtze River in 8 sampling points of metal concentration of plant roots in soil analysis, found in January in the total sediment environment of plant roots average metal content was the lowest, the highest in April, Ti, metal Fe, Mn concentration levels were dominant, than other metal elements with high content of 2-3 orders of magnitude, the metal content of Cd was the lowest; overall, factory outlet near the sampling point of Wusong sewage treatment, landfill and Shidongkou Wastewater Discharge downstream near the mouth of the sampling point in Chaoyang, the highest content of metal; interspecific differences, the average content of root system in cloudy sky of heavy metals in the sediments Low Cu was the highest in the reed root sediment concentration, the other 12 kinds of heavy metals in Spartina alterniflora sediments accumulated most species; except manganese metal, metal content in plant tissue distribution: the rhizome and leaf of.1 month, April plants in different tissues of root, stem, leaf metal accumulation concentration level, higher than in July. October. Overall, cloudy sky grass, reed of different metal elements in the stone cave, Wusong accumulated more metal content of different tissues in Spartina alterniflora is in Wusongkou, Donghai farm is higher. The particle morphology, scanning electron microscopy in plant tissues showed a variety of particle size, adsorption in different tissues of three species of plants in the various dimensions form a circle, square, rectangular, appeared in aggregates of many elements of the form, which also shows that the nano metal particles exist widely in estuarine vegetation environment. Based on the 8 sampling points Plant root sediment, analysis of different forms of sulfur in the surface sediments, found the cloudy sky grass. Root sediment. The sulfur content of different forms of distribution in the volatile sulfur acid..SO42S (AVS); abundance distribution of root sediment SRB for root surface sediment sediment; time distribution, abundance of different forms of SRB in April. Sulfur concentrations were the highest; the space, the more serious pollution samples such as Wu, Chaoyang farm, its concentration level is relatively higher than other points. Through the analysis of the correlation between soil heavy metals and SRB abundance in the natural environment under cloudy sky roots, the results showed that the APS-a target gene quantitative SRB abundance, except Fe the rest, 12 kinds of heavy metals were significantly related with the abundance of SRB, with APS-b as the target gene quantitative SRB abundance, only the elements of Mn, Pb was significantly correlated with the abundance of SRB, suggesting that SRB can be effectively removed in some extent Root sediments of metal in the environment. There are some samples such as Liuhekou, seven Yakou, SRB abundance is higher, the lower the content of SO42-, it is likely that the SRB will show the sulfate reduction results. SEM results show that by participating in the SRB AgN03 group in nutrient solution to form a metal sulfide particle size, but also with the exposure concentration increased. Either Ag+ or Ag exposure group, NPs exposure group, SRB were involved in the Ag content of the residual in the nutrient solution is lower than the control group. Four different experimental exposure group, the tissue of root, stem had accumulated a lot of silver ion the concentration of Ag, and accumulated in plant tissues were with the passage of time, the exposure concentration increased, the treatment of Ag+ experimental group, plant tissue accumulated in the concentration level of Ag. The highest Ag+ treatment group, SRB in the roots and stems The cumulative Ag less than that of the control group; the experimental group exposed to AgNPs, SRB the roots and stems of the accumulation of Ag is higher than that of the control group. However, the experimental results show that SRB is involved in not on the transmission factor of Ag and cloudy sky grass tissue showed no significant effect on the whole, in addition to Ag+ and SRB exposure group, the remaining 3 exposure to the experimental group, different exposure time TF values decreased with increasing exposure concentration. Scanning electron microscopy shows that after exposure to cloudy sky roots, Ag particles were attached to the stem, but the top of the cloudy sky grass stems but did not find the particles, this may be because the polarity of short-term exposure the silver particles to transmit the cloudy sky slowly. Grass tissue enzyme digestion after exposure by SP-ICP-MS analysis, the results showed that plant tissue accumulated a large amount of AgNPs, and the particle size is less than 60NM, which is consistent with the SEM results. In summary, indoor exposure test, the participation of SRB Indeed to Ag+ exposure in experimental group of plant root Ag in the environment play a fixed role, while AgNPs and SRB in the experimental group showed no significant fixed effects on Ag, which may be related to the period of the experiment, particle size, root exudates were associated, on this day to still need.

【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X17

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