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91.
为了评价氮沉降对我国亚热带河口区淡水感潮沼泽湿地CO_2、CH_4排放通量的影响,在福建闽江口道庆洲淡水感潮短叶茳芏沼泽湿地,设置对照CK[0 g·(m~2·a)~(-1)]及3个梯度的氮沉降处理:N1[24 g·(m~2·a)~(-1)]、N2[48 g·(m~2·a)~(-1)]和N3[96 g·(m~2·a)~(-1)],采用静态箱-气相色谱法测定短叶茳芏湿地CO_2、CH_4排放通量,并同步观测相关环境因子.结果表明,(1)与对照相比,N1处理CO_2排放通量增加20.30%,N2处理CO_2排放通量减少10.05%,N3处理CO_2排放通量增加4.06%,除了12月的N2、N3处理CO_2排放通量与对照间有显著差异外(P0.05),其它时间各处理间CO_2排放通量差异性不显著(P0.05).(2)与对照相比,N1处理CH_4排放通量提高64.51%,N2处理CH_4排放通量提高30.23%,N3处理CH_4排放通量提高80.57%,但是各处理间CH_4排放通量的差异性未达到显著水平(P0.05).(3)CO_2、CH_4排放通量与土壤温度具有显著的正线性相关关系(P0.05),与土壤EC、土壤p H的相关性不显著(P0.05). 相似文献
92.
长江口潮滩沉积物的性状对重金属累积的影响 总被引:13,自引:0,他引:13
采集长江口无明显点源污染的崇明东滩和九段沙潮滩56个沉积物样品,测定沉积物原样和粘粒中Cu.Zn,Pb,Cr,Cd和Ni的含量以及沉积物的主要性状(粒径分布、游离铁、活性铁、总铁、游离锰、总锰、有机碳和磁化率等),以相关分析和偏相关分析研究沉积物中重金属含量与沉积物主要性质之间的关系.结果表明,沉积物中粘粒的Cu,Zn,Pb,Cr和Ni含量分别是相应沉积物原样的2.3,3.3,2.0,1.7和2.1倍.潮滩沉积物粘粒的含量是影响重金属累积的主要因素.潮滩沉积物中的磁化率与重金属含量呈显著相关性,表明利用磁信息研究潮滩重金属污染的可行性. 相似文献
93.
Almeida CM Mucha AP Vasconcelos MT 《Environmental science and pollution research international》2005,12(5):271-277
Goal, Scope and Background The presence or absence of vegetation can condition sediment characteristics. The main aim of this work was to investigate
the influence of the sea rush Juncus maritimus on metal (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) availability to organisms living
on or in estuarine sediments, from Douro River (NW Portugal), by comparing the characteristics and chemical behaviour of rhizosediments
(collected within the plant assemblage) and those of sediment (collected around the plant). In order to evaluate whether and
how sediment characteristics condition the role of plants on metal availability, sandy and muddy sediments colonised by J.
maritimus were studied in parallel.
Methods Metal availability was estimated by enzymatic digestion with pepsin (ED), which may provide an estimate of metal availability
to organisms living at estuarine sediments. Nevertheless, since no consensus exists yet on the most suitable methodologies
to estimate metal bioavailability in sediments, two more conventional approaches, BCR sequential extraction (SE) and AVS/SEM
model, were also used, in parallel, and the information these approaches provided was compared with that provided by ED. Total-recoverable
metal contents were determined by atomic absorption spectrophotometry after sediment digestion using a high-pressure microwave
system.
Results and Discussion Plants could concentrate metals around its roots and rhizomes. In addition, they were capable of oxidizing (release of oxygen
by the roots) the anaerobic medium surrounding their roots in muddy sediment (reducing AVS). As sulphide oxidation renders
metals (Cd, Cu, Ni, Pb and Zn) into more soluble forms, according to the AVS/SEM model, metals from muddy sites would be more
available in rhizosediment than in sediment. The SE approach led to a similar conclusion. Nevertheless, the results provided
by ED pointed at opposite conclusion, particularly for Cd and Zn, indicating less availability at rhizosediments than in the
surrounding sediment. ED results were interpreted as a consequence of an enrichment of the rhizosediment in organic ligands
exuded by the roots or liberated by dead plants. The effect of complexation of metals by organic compounds, which ED could
not decompose/dissolve, seemed to overcome that caused by sediment oxidation. In general, a comparison of the information
about metal availability by ED, SE, AVS/SEM, showed that it did not always match and in few cases it was even contradictory.
Conclusion and Outlook Therefore, a thorough evaluation of the metal availability in sediments requires a combination of different chemical approaches,
so as to take into consideration differences in ways of organism exposure (interstitial water and/or ingestion of sediment
particles).
- * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August
to 1 September 2004, Bordeaux, France. 相似文献
94.
Environmental Impact of Undular Tidal Bores in Tropical Rivers 总被引:3,自引:1,他引:3
A tidal bore impacts significantly on the estuarine ecosystem, although little is known on the flow field, mixing and sediment
motion beneath tidal bores. In the absence of detailed systematic field measurements, a quasi-steady flow analogy was applied
to investigate undular tidal bores with inflow Froude numbers between 1.25 and 1.6. Experimental results indicated that rapid
flow redistributions occur beneath the free-surface undulations, with significant variations in bed shear stress between wave
crests and troughs. Dynamic similarity was used to predict detailed flow characteristics of undular tidal bores. The effects
of periodic loading on river sediments, scour of river bed and flow mixing behind the bore are discussed. A better understanding
of these processes will contribute to better management practices in tidal bore affected rivers, including the Styx and Daly
rivers in tropical Australia. 相似文献
95.
This paper reports the fluvial fluxes and estuarine transport of organic carbon and nutrients from a tropical river (Tsengwen River), southwestern Taiwan. Riverine fluxes of organic carbon and nutrients were highly variable temporally, due primarily to temporal variations in river discharge and suspended load. The sediment yield of the drainage basin during the study period (1995–1996, 616 tonne km–2 year–1) was ca. 15 times lower than that of the long-term (1960–1998) average (9379 tonne km2 year–1), resulting mainly from the damming effect and historically low record of river water discharge (5.02 m3 s–1) in 1995. The flushing time of river water in the estuary varied from 5 months in the dry season to >4.5 days in the wet season and about 1 day in the flood period. Consequently, distributions of nutrients, dissolved organic carbon (DOC) and particulate organic carbon (POC) were of highly seasonal variability in the estuary. Nutrients and POC behaved nonconservatively but DOC behaved conservatively in the estuary. DOC fluxes were generally greater than POC fluxes with the exception that POC fluxes considerably exceeded DOC fluxes during the flood period. Degradation of DOC and POC within the span of flushing time was insignificant and may contribute little amount of CO2 to the estuary during the wet season and flood period. Net estuarine fluxes of nutrients were determined by riverine fluxes and estuarine removals (or additions) of nutrients. The magnitude of estuarine removal or addition for a nutrient was also seasonally variable, and these processes must be considered for net flux estimates from the river to the sea. As a result, nonconservative fluxes of dissolved inorganic phosphorus (DIP) from the estuary are –0.002, –0.09 and –0.59 mmol m–2 day–1, respectively, for dry season, wet season and flood period, indicating internal sinks of DIP during all seasons. Due to high turbidity and short flushing time of estuarine water, DIP in the flood period may be derived largely from geochemical processes rather than biological removal, and this DIP should not be included in an annual estimate of carbon budget. The internal sink of phosphorus corresponds to a net organic carbon production (photosynthesis–respiration, p–r) during dry (0.21 mmol m–2 day–1) and wet (9.5 mmol m–2 day–1) seasons. The magnitude of net production (p–r) is 1.5 mol m–2 year–1, indicating that the estuary is autotrophic in 1995. However, there is a net nitrogen loss (nitrogen fixation–denitrification < 0) in 1995, but the magnitude is small (–0.17 mol m–2 year–1). 相似文献
96.
97.
基于2011年洪季在南支河道从小潮至大潮连续8天现场定点观测所获得水沙观测数据(包括潮流、悬沙浓度、悬沙粒度和表层沉积物样品),通过对悬沙浓度、悬沙粒度和沉积物在不同时刻的组成分析,以及流速、悬沙和底床切应力的相互影响分析,对长江河口南支河道悬沙随时间变化特性和河床沙再悬浮作用进行了研究。结果表明:观测期间南支主槽下段落潮水动力强于涨潮;落潮悬沙浓度高于涨潮,并由小潮至大潮逐渐增加;落潮悬沙粒径粗于涨潮,并随小潮至大潮不断粗化;河床沉积物颗粒较粗,细砂类组成达到90%以上;流速、悬沙及底床切应力之间存在显著相关性;河床泥沙再悬浮强度较强,其量值有限。而近期研究区域悬沙浓度和水沙关系发生变化,与流域来沙出现锐减有关。 相似文献
98.
99.
100.
基于合作博弈论的感潮河网区污染物排放总量削减分配模型研究 总被引:1,自引:0,他引:1
在给定污染物削减目标的情况下,如何确定各排污区域的分配比例一直是污染物总量分配技术的核心问题,博弈论是解决这一问题的有效尝试。采用合作博弈论方法,以感潮河网区各排污区域为研究对象,充分考虑各区域的污染治理成本、排污策略与环境质量的相互影响,建立了在给定污染物总削减比例条件下各区域环境合作的博弈模型,计算了各种可能联盟的特征函数值,利用Shapley值法进行合作收益的公平分配。结合珠江三角洲西江-石岐河河网区3个区域的环境合作案例说明削减合作的可行性,在总削减比例为15%的约束下,3区域合作削减比例是20.77%、12.82%和12.99%,与合作前相比,3个区域合作后环境成本分别减少了11.83%、2.13%和2%。 相似文献