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1.
The regulatory effects of environmental factors on denitrification were studied in the sediments of Meiliang Bay, Taihu Lake, in a monthly sampling campaign over a one-year period. Denitrification rates were measured in slurries of field samples and enrichment experiments using the acetylene inhibition technique. Sediment denitrification rates in inner bay and outer bay ranged from 2.8 to 51.5 nmol N2/(g dw (dry weight)·hr) and from 1.5 to 81.1 nmol N2/(g dw·hr), respectively. Sediment denitrification rates were greatest in the spring and lowest in the summer and early autumn, due primarily to seasonal differences in nitrate concentration and water temperature. For each site, positive and linear relationships were regularly observed between denitrification rate and water columnn itrate concentration. Of various environmental factors on denitrification that we assessed, nitrate was determined to be the key factor limiting denitrification rates in the sediments of Meiliang Bay. In addition, at the two sites denitrification rates were also regulated by temperature. The addition of organic substrates had no significant effect on denitrification rate, indicating that sediment denitrification was not limited by organic carbon availability in the sediments. Nitrate in the water column was depleted during summer and early autumn, and this suppressed effective removal of nitrogen from Taihu Lake by denitrification.  相似文献   

2.
Surface sediments are closely related to lake black blooms. The dissolved oxygen (DO) distribution and its penetration depth in surface sediments as well as the migration and transformation of redox sensitive elements such as Fe and S at the sediment-water interface are important factors that could influence the formation of the black bloom. In this study, dredged and undredged sediment cores with different surface properties were used to simulate black blooms in the laboratory. The Micro Profiling System was employed to explore features of the DO and ∑H2S distribution at the sediment-water interface. Physical and chemical characteristics in sediments and pore waters were also analyzed. The results showed that sediment dredging effectively suppressed the black blooms. In the undredged treatment, DO penetration depth was only 50 μm. Fe^2+ concentrations, ∑H2S concentrations, and ∑H2S production rates were remarkably higher in surface sediments and pore waters compared to control and dredged treatments. Furthermore, depletion of DO and accumulation of Fe^2+ and ∑H2S in surface sediments and pore waters provided favorable redox environments and necessary material sources for the blooms. The study results proved that physical and chemical characteristics in surface sediments are important factors in the formation of the black bloom, and could provide scientific guidance for emergency treatment and long-term pre-control of black blooms.  相似文献   

3.
Lake littoral zones are characterized by heterogeneity in the biogeochemistry of nutrient elements. This study aimed to explore the relationship between the nitrous oxide reductase gene (nosZ)-encoding denitrifier community composition/abundance and N2O reduction. Five samples (deep sediment, near-transition sediment, transition site, near-transition land and land soil) were collected along a littoral gradient of eutrophic Baiyangdian Lake, North China. To investigate the relationship between the nosZ-encoding denitrifier community structure and N2O reduction, the nosZ-encoding denitrifier community composition/abundance, potential denitrification rate (DNR) and potential N2O production rate (pN2O) were investigated using molecular biological technologies and laboratory incubation experiments. The results showed that the average DNR of sediments was about 25 times higher than that of land soils, reaching 282.5 nmol N/(g dry weight (dw)·hr) and that the average pN2O of sediments was about 3.5 times higher than that of land soils, reaching 15.7 nmol N/(g dw·hr). In the land area, the nosZ gene abundance showed a negative correlation with the N2O/(N2O+N2) ratio, indicating that nosZ gene abundance dominated N2O reduction both in the surface soils of the land area and in the soil core of the transition site.Phylogenetic analysis showed that all the nosZ sequences recovered from sediment clustered closely with the isolates Azospirillum largimobile and Azospirillum irakense affiliated to Rhodospirillaceae in alpha-Proteobacteria, while about 92.3% (12/13) of the nosZ sequences recovered from land soil affiliated to Rhizobiaceae and Bradyrhizobiaceae in α-Proteobacteria. The community composition of nosZ gene-encoding denitrifiers appeared to be coupled with N2O reduction along the littoral gradient.  相似文献   

4.
The microscale distribution of oxygen,the nitrogen flux and the denitrification rates in sediment inhabited by chironomid larvae(Tanypus chinensis) were measured in eutrophic Lake Taihu,China.The presence of the chironomids in the sediment increased the oxygen diffusional flux from 10.4 ± 1.4 to 12.7 ± 2.5 mmol O 2 /(m 2 ·day).The burrows of the larvae represented "hot spots" and strongly influenced the nitrogen cycles and diagenetic activity in the sediment.The results indicate that the bioturbation effects of Tanypus chinensis chironomid larvae increased the capacity of the sediment as a sink for nitrate and a source for ammonium.Nitrate influx and ammonium outflux were increased 8.8 and 1.7 times,respectively.Under bioturbation,the amount of nitrate consumed was greater than the amount of ammonium released.The total denitrification rate was also enhanced from 0.76 ± 0.34 to 5.50 ± 1.30 mmol N/(m 2 ·day).The net effect was that the bioturbated sediments acted as a net sink for inorganic nitrogen under direct and indirect bioturbation effects compared to the control.  相似文献   

5.
Algae-caused black bloom (also known as black water agglomerate) has recently become a critical problem in some Chinese lakes.It has been suggested that the occurrence of algae-caused black bloom was caused by the cooperation of nutrient-rich sediment with dead algae,and sludge dredging was adopted to control black bloom in some lakes of China.In this article,based on the simulation of black bloom using a Y-shape apparatus for modeling natural conditions,both un-dredged and dredged sites in three areas of Taihu Lake,China were studied to estimate the effects of dredging on the prevention and control of black bloom.During the experiment,drained algae were added to all six sites as an additional organic load;subsequently,the dissolved oxygen decreased rapidly,dropping to 0 mg/L at the sediment-water interface.Black bloom did not occur in the dredged sites of Moon Bay and Nan Quan,whereas all three un-dredged sites at Fudu Port,Moon Bay and Nan Quan experienced black bloom.Black bloom also occurred at the dredged site of Fudu Port one day later than at the other sites,and the odor and color were lighter than at the other locations.The color and odor of the black water mainly result from the presence of sulfides such as metal sulfides and hydrogen sulfide,among other chemicals,under reductive conditions.The color and odor of the water,together with the high concentrations of nutrients,were mainly caused by the decomposition of the algae and the presence of nutrient-rich sediment.Overall,the removal of the nutrient-rich sediment by dredging can prevent the occurrence and control the degree of algae-caused black bloom in Taihu Lake.  相似文献   

6.
Estuarine ecosystems in SE Asia have been poorly studied when compared to other tropical environments. Important gaps exist particularly in the understanding of their biogeochemical function and contribution to global change. In this work we looked into N-turnover in the water column and sediments of the Bangpakong estuary(13°N). A seasonal sampling program was performed along the salinity gradient covering different stretches of the estuary(68 km).Key physical and chemical characteristics were also monitored in order to unravel possible environmental controls. Results showed the occurrence of active denitrification in sediments(5.7–50.9 nmol N-N2/(cm3·hr)), and water column(3.5–1044 pmol N-N2/(cm3·hr)). No seasonal or spatial variability was detected for denitrification potential in sediment samples. However, in the water column, the denitrification activity peaked during the transition season in the downstream sites coinciding with high turbidity levels. Therefore, in that period of the year, the water column compartment may be an important contributor to nitrate reduction within the estuary. The rather low nitrification rates detected were not always measurable, probably due to the reduced oxygen content and high siltation. This study is one of the few dealing simultaneously with sediments and water column processes in a highly turbid tropical estuary.Therefore, it emerges as a valuable contribution for the understanding of the dynamics of the nitrogen cycle in tropical environments by exploring the role of estuarine N microbial activity in reducing the effects of increased nitrogen loads.  相似文献   

7.
A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis.Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition(N, NH4Cl100, 200, 400 mg/kg, respectively) were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, which may be related to the reason that the root growth was affected by N addition.Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH4+may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.  相似文献   

8.
Mercury contamination and accumulation in sediments of the East China Sea   总被引:1,自引:0,他引:1  
Mercury (Hg) concentrations in sediment samples collected from the inner and middle shelves of the East China Sea (ECS) were analyzed to evaluate Hg contamination levels and to calculate Hg sedimentation rates and total accumulation in the ECS. The range of Hg concentrations in surface sediments of the inner shelf was 26.5–47.6 ng/g, and that for the middle shelf was 4.1–13.9 ng/g. Hg concentrations correlated well with organic carbon contents but varied inversely with sediment grain size. Enrichment factors indicated that the whole inner shelf and a small portion of the middle shelf were slightly contaminated by Hg. Hg accumulation rates in the ECS ranged between 0.42–48.7 ng/(cm2·yr), with higher values observed in the inner shelf. Total Hg accumulation in the calculated area (accounting for 80% of the ECS continental shelf area) ranged from 25 to 30 tons/yr; approximately 51% and 17% of the accumulated Hg mass was deposited in the Yangtze estuarine zone and the inner shelf, respectively.  相似文献   

9.
Three active barrier materials (zeolite, ceramicite and light porous media) were applied for preventing nitrogen (N) release from eutrophic lake sediments. Long term experiment of two di erent lake sediments were carried out and the e ect of zeolite dose was evaluated. The results indicated that about 90%–100% of total N in overlying water was eliminated by using zeolite. While the N removal e ciency by ceramic was lower than that by zeolite, and light porous media present the lowest e ciency of 59%. Long term sediment incubation experiments indicated that two eutrophic sediments were both e ective in preventing N release in spite of di erent release characteristics. Bio-zeolite capping technology was able to e ectively inhibit the release of N from the sediment, and the zeolite dose was independently from N removal.  相似文献   

10.
Persistent organochlorine compounds were analyzed by means of GC-ECD in surface sediment samples from two selected rivers in Tianjin, Haihe River and Dagu Drainage River. A total of 16 surface sediment sites were selected along the both rivers. The frequency of detection of T-HCH and T-DDT in sediment samples both was up to 100%, which illustrated that the contamination of HCH and DDT was widespread in Haihe and Dagu Drainage Rivers. Results indicated that the concentrations of various pesticides in sediments from Haihe River were in the range of 3.30-75.96 ng/g dw for T-HCH and 1.57-211.57 ng/g dw for T-DDT. Compared with Haihe River, Dagu Drainage River was contaminated by HCHs and DDTs along the all locations and the values of T-HCH and T-DDT residues in sediments ranged from 2.30 to 124.61 ng/g dw and from 11.28 to 237.30 ng/g dw, respectively, The possible pollution sources were analyzed through monitoring results of organochlorine pesticides(OCPs) residues in sediments from the two rivers. The investigation also indicated that HCH was still used as pesticide in Tianjin partial area.  相似文献   

11.
在清淤底泥中添加碱性粉煤灰、燃煤炉渣进行钝化处理后,通过浸出毒性实验、重金属形态分级实验及植物生长实验对底泥基质中重金属的活性及生物有效性进行了研究.结果表明:清淤底泥中添加粉煤灰、燃煤炉渣等碱性物质后显著降低了底泥基质中可溶态重金属含量,其中,交换态、有机结合态Pb、Zn所占比例显著降低;碱性物质的加入缓解了重金属的浸出危害,钝化底泥基质中粉煤灰、炉渣对Cu的稳定率可达90.34%~96.88%;与此同时也抑制了底泥中重金属在植物体内的富集与迁移,降低了重金属的生物有效性.相关性分析表明,底泥基质中交换态重金属含量、浸出浓度、植物茎叶中重金属含量及植物根伸长抑制率之间存在显著正相关关系(p0.01).  相似文献   

12.
疏浚对湖泛的影响:以太湖八房港和闾江口水域为例   总被引:3,自引:0,他引:3  
通过采集太湖八房港和闾江口疏浚后与未疏浚沉积物柱状样于室内模拟“湖泛”的发生与消退过程来研究底泥疏浚对藻源性“湖泛”形成和消退的影响.结果发现,疏浚能有效的延缓“湖泛”发生的时间,八房港和闾江口疏浚后沉积物柱状样水体色度均要低于未疏浚对照样,水体泛黑的时间也分别比未疏浚对照样延迟6d和2d.疏浚沉积物对上覆水柱中营养盐的含量也有较好的控制,试验过程中八房港和闾江口疏浚后沉积物柱状样水体中 NH4+-N的含量仅分别未疏浚对照组的40%和77.1%,PO43--P的含量也仅分别为未疏浚对照组的41.4%和78.1%.值得注意的是,疏浚沉积物所对应的水柱中Fe2+和S2-的含量均要高于未疏浚对照组.八房港和闾江口疏浚沉积物中亚铁的含量分别是未疏浚对照样的78.1%和76.4%,而闾江口疏浚后沉积物中酸挥发性硫化物(AVS)的含量则是未疏浚对照的1.36倍.沉积物中铁、AVS的含量没有表现出明显的垂向分布特征.  相似文献   

13.
底泥疏浚对竺山湖底栖生物群落结构变化及水质影响   总被引:5,自引:2,他引:3  
结合2008年年底在竺山湖进行的底泥清淤工程,调查了底泥疏浚6个月后对大型底栖动物的群落结构的影响及水质变化.结果表明,疏浚区和未疏浚区底栖动物均以霍普水丝蚓、摇蚊和铜锈环棱螺3种生物为主;同未疏浚区相比,疏浚后生物多样性降低,但生物量增加.受外源污染影响,上覆水体中TN、TP含量变化幅度分别为1.64~4.45mg/L和0.133~0.258mg/L,较高的水体营养盐含量,使得疏浚后的新生底泥仍处于营养盐较高的状态,从而使得底栖动物群落组成以生活于污染较重的物种为主.采用Shannon-Weaver、Simpson和Goodnight指数对底栖生物进行评价,结果表明疏浚区处于中度污染,未疏浚区处于中-重度污染状态.结合底栖动物调查和水质监测结果,只有在严格控制外源污染对水体的影响后,底泥疏浚才能起到应有的作用.  相似文献   

14.
我国河湖众多,水体疏浚底泥具有污染物含量较高、成分复杂、量大的特点。介绍了国内疏浚底泥利用现状,提出了能源化利用底泥处理方向。热解技术具有处理彻底、固化重金属、基本无污染气体排放、可进行能源回收等优点,而催化热解能够促进提高底泥热解效率并控制反应产物分布。通过对底泥添加合适金属氧化物催化剂后进行热解处理,发现在热解低温段(<300℃),添加催化剂剂量>2%时,热解气态产物中氢占比可提高约50%。催化热解后固相产物热解半焦的产率为40%~45%,热解处理后底泥减容效果好。  相似文献   

15.
上海市郊河流底泥氮磷释放规律的初步研究   总被引:37,自引:0,他引:37  
上海市郊河流底泥有很高的氮、磷负荷。为了研究底泥氮、磷释放规律,取一定量的新鲜底泥在室内进行通气和厌气培养试验;同时,用鱼塘底泥作对照。结果表明:(1)厌气条件下,底泥NH3-N释放速率和释放量高于通气条件,培养液NH3-N可在较长时间内维持峰值水平;通气条件下,由于硝化作用较强,培养液NH3-N含量达到峰值后,迅速下降。(2)厌气条件下,底泥水溶态磷的释出量远远高于通气条件。厌气条件下释放的正磷酸盐大部分源自Fe-P的还原解吸。(3)鱼塘底泥氮、磷释放量高于河流底泥,但其氮、磷负荷却非最高,这与其含有大量的易降解性有机质有关。  相似文献   

16.
上海黄浦江沉积物中的重金属污染趋势   总被引:1,自引:0,他引:1  
根据200~2009年黄浦江疏浚物(沉积物)样品分析结果,对上海黄浦江沉积物污染情况进行分析,结果表明,2007~2009年黄浦江沉积物中Cu、Pb、Zn、Cd、As平均含量均大于1978~1980年的上海市市土壤背景值,表明黄浦江沉积物受到一定污染.对沉积物中各污染要素污染趋势进行研究,各要素污染趋势各有差异,除Pb...  相似文献   

17.
污染底泥是水体最主要的内源,存在污染物二次释放的风险,而环保疏浚可以有效地清除污染底泥、降低内源污染负荷及其释放风险,因此近年来该技术在水环境治理中得到广泛的应用.环保疏浚的主要目的是有效清除河流、湖泊(水库)水体污染底泥中累积的污染物,并对浚后污泥进行安全处理处置,为污染河流、湖泊(水库)水质改善与生态修复发挥工程作用.作为湖泊、河流水污染综合治理技术体系的重要组成部分,环保疏浚是生态环境工程技术之一,也是湖泊河流水污染治理的重要手段;但底泥疏浚同时也存在疏浚效果不理想、可能造成原位扰动与异地污染、改变水生态系统的结构与功能等生态风险.研究显示,未来环保疏浚的主要发展方向应包括:① 基于调查评估基础上的污染底泥分区、分类环保疏浚及处理处置研究;② 污染底泥环保疏浚与区域生态修复一体化设计研究;③ 污染底泥环保疏浚-浚后干化-处理处置-资源化集成技术研究;④ 污染底泥环保疏浚、处理和资源化全过程监管评估技术研究.   相似文献   

18.
官厅水库坝前疏浚底泥的理化特征和土地利用研究   总被引:10,自引:1,他引:10  
用环保疏浚船抽取官厅水库坝前表层底泥,在田间脱水池进行自然脱水,研究脱水后底泥的理化性质和污染物特征,底泥无害化处理方式和处理后底泥的土地利用效果.结果表明,官厅水库坝前疏浚底泥中黏粒含量高,容重高达1.89  g·cm-3,孔隙度只有23.8%,干后龟裂且非常坚硬,植物不能在上面生长.底泥中含有大量的还原性物质和速效性氮、磷,但重金属和有机氯农药含量均低于二级土壤环境质量标准.通过加入砂性土壤和作物秸杆等材料可以降低底泥容重和还原性物质含量,提高底泥的孔隙度并固持底泥中的速效性氮、磷.经过处理后的底泥可以成为良好的植物生长介质,玉米、苜蓿和杏树苗在上面生长良好.  相似文献   

19.
疏浚底泥的资源化利用   总被引:9,自引:1,他引:9  
各种各样的疏浚工程产生的疏浚底泥量日益增加,以往的底泥堆放,吹填和抛海等常规处置方式对环境造成了潜在的不利影响.因而,疏浚底泥资源化越来越为人们所重视.本文总结了疏浚底泥资源化的途径,对土地利用、制造填方材料和建筑材料等资源化利用进行了讨论,并对疏浚底泥的资源化利用提出一些建议.  相似文献   

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