环境微界面对湖泊内源磷释放的影响研究

为揭示湖泊内源污染物释放的发生机制,从环境微界面角度出发,研究湖泊水-沉积物界面三相结构模式中磷的界面反应过程。利用微电极系统获取微界面溶氧浓度剖面,并结合Profile模型进行分析计算。计算结果表明：该湖湖心区沉积柱含氧层厚度达5mm,而湖口区则不到3mm,湖心区微界面上氧气消耗主要以自由扩散为主,而湖口区受微界面上微生物活动影响较大。同时利用梯度扩散薄膜技术获取了水-沉积物界面上分辨率高达1mm的可溶性活性磷剖面浓度分布,结果表明,在湖口区沉积物表层2cm处有强烈磷释放现象,而在湖心区则未发现,这可能     

湖泊沉积物-水微界面上磷的释放过程研究

为揭示湖泊内源污染的微界面环境行为及机制,从环境微界面角度出发,研究湖泊沉积物-水微界面磷的释放过程。利用新兴的湖泊沉积物原位高分辨率间隙水采集技术(DGT和Mini-peeper)分别获取了大纵湖、蜈蚣湖和九龙口沉积环境中生物有效磷和可溶性活性磷的垂直剖面分布,并在微尺度下发现了由局部有机质强烈降解释放磷酸盐形成的异常突变点。利用DIFS模型分析了沉积物对磷的吸附解吸特性,结果发现:疏浚后的九龙口沉积物对磷酸盐的吸附解吸能力较弱,而大纵湖和蜈蚣湖表层沉积物磷酸盐则以弱结合态为主,具有良好的磷吸附特性,表明稳定的沉积物表层环境微界面系统对内源磷的释放具有很好的缓冲作用;同时发现大纵湖和蜈蚣湖表层沉积物对间隙水中的磷具有较强的补给能力,补给源主要分布在沉积物表层2~3 cm附近,对界面磷的释放起关键的调节作用。     

典型盐碱地改良区农田排水沟水体与底泥界面氧通量研究

农田排水沟水体与底泥中的氧含量决定了底泥中各种生源要素的最终归趋,对维持农田排水沟的水环境至关重要。本论文以陕西富平县卤泊滩盐碱地改良区农田排水沟水体与底泥为研究对象,从环境微界面角度出发,根据多年监测数据构建室内试验,采用高分辨率微环境固液剖面传感系统(丹麦Unisense微电极系统),探究了研究区农田排水沟水体与底泥界面氧通量变化规律。研究结果表明:底泥中的溶解氧随深度的增加逐渐减小,直至溶解氧浓度为零,到达厌氧层;溶解氧剖面浓度的实测值与Profile模型模拟值的相关系数均在0.995以上,表明该模型能客观地描述溶解氧在农田排水沟水体与底泥扩散边界层和底泥中的分布;农田排水沟上游不同监测点位的底泥含氧层厚度在3.5～6 mm之间,而下游监测点位的底泥含氧层厚度约为1.5 mm,差异显著;通过氧浓度线性分布、剖面拐点法得到氧气扩散边界厚度,上游监测点位的氧气扩散边界层厚度基本在1 mm,而下游监测点位的氧气扩散边界层厚度减少至0.2 mm。农田排水沟水体与底泥界面氧通量的测定,对于认识农田排水沟底泥的地球化学过程及水环境作用机理具有重要意义,可为农田排水沟水环境治理提供参考依据。     

上覆水磷浓度对沉积物孔隙水中磷垂向分布的影响

为探究上覆水磷浓度对沉积物孔隙水中磷垂向分布的影响,通过室内实验,利用薄膜扩散平衡技术(DET)对孔隙水中磷浓度进行测量,分析孔隙水磷浓度的垂向变化规律,并揭示平衡时上覆水磷浓度与孔隙水磷浓度以及上覆水-沉积物界面孔隙水磷浓度的关系。结果表明:上覆水磷浓度越高,则沉积物孔隙水中磷垂向分布达到平衡所需的时间越长,相同垂向位置处孔隙水磷浓度及其浓度梯度越大;孔隙水磷浓度及其浓度梯度随深度增加而降低,表层沉积物孔隙水中磷的扩散作用最强,下层沉积物孔隙水磷浓度受上覆水磷浓度变化影响较小;吸附平衡后,沉积物孔隙水磷浓度和上覆水-沉积物界面孔隙水磷浓度均与上覆水磷浓度呈幂函数关系,而留存在沉积物孔隙水中的磷浓度仅占2.26%～3.80%,上覆水中减少的磷大部分被沉积物吸附。     

盐城大纵湖疏浚前后沉积物-水界面环境化学变化

运用微电极技术,模拟盐城大纵湖疏浚前后沉积物柱状样,分析疏浚前后沉积物-水界面约2cm深度的pH、Eh和DO的剖面数值及变化规律,探讨底泥疏浚对控制浅水湖泊富营养化的作用。结果表明:采用传统方法和微电极技术测得的Eh和pH值结果相差很大,微电极技术在微尺度下更具有研究意义;疏浚前后沉积物的含氧层厚度分别为8 mm和13 mm;微尺度下疏浚前后pH、Eh和DO值的变化趋势显示疏浚有助于富营养化的控制。     

武汉城市湖泊汞的迁移与富集

对武汉远郊、城乡结合部和市区3种环境中6个湖泊的水、界面水、沉积物和生物(鱼)进行调查采样,用离心机离心出沉积物中的孔隙水,用原子荧光光谱仪进行汞含量测定。以土壤—水—界面水—孔隙水—沉积物—生物为轴线,探讨了汞在研究区土壤—沉积物系统、湖水—沉积物系统和湖水—界面水—孔隙水系统中的分配以及湖泊鲢鱼肉中汞与沉积物和水中汞的关系。建立了武汉城市湖泊汞的迁移、富集理想模式:湖泊水汞经悬浮物吸附沉淀而富集于沉积物中,沉积物中汞经化学转化传输给孔隙水;存在于悬浮物中的界面水汞,经解吸附后向湖水扩散而产生二次污染。湖水汞被鱼吸收而产生生物富集。从而得出湖水—界面水—孔隙水—沉积物、湖水—鱼的两种富集机制。     

基于涡动相关法的沉积物-水界面氧通量与水动力条件响应关系

沉积物-水界面是物质参与环境地球化学循环和生物耦合的"热区",水动力条件是沉积物-水界面物质交换的关键影响因素。溶解氧作为常用的水质评价指标,对调节生物化学进程有重要作用,因此本文采用涡动相关法这种非侵入式通量测量技术开展室内试验研究,探究沉积物-水界面氧通量与水动力条件的响应关系。结果表明:随着水体紊动增加(采用Batchelor尺度表征),扩散边界层厚度减小,氧通量增大。分析室内试验和相关研究中水动力条件、扩散边界层厚度及氧通量的关系,发现扩散边界层厚度与Batchelor尺度呈正相关关系,拟合结果表明可以用Batchelor尺度近似表示扩散边界层厚度;氧通量与扩散边界层厚度呈负相关关系,且当扩散边界层厚度小于0.5 mm时,扩散边界层厚度变化对氧通量影响更强烈,当厚度大于0.5 mm后,氧通量基本保持稳定。     

太湖湍流特征及其对表层沉积物起悬机制的影响

太湖是一个典型的浅水大湖泊且富营养化严重,动力扰动引起的水-土界面沉积物起悬与太湖蓝藻水华的暴发有密切联系。基于声学多普勒流速仪、OBS浊度仪、pH-ⅡHandheld手持式气象站等仪器监测得到的原位高频气象、水动力、水质同步数据,分析了湖泊水-土界面悬浮物浓度与风速、切应力及湍流特征的关系。研究结果表明:观测期间,湖心区底泥沉积物再悬浮过程中由波切应力起主导作用,观测的切应力临界值为0.08 N/m~2,临界风速为4 m/s。底泥再悬浮主要是由拟序结构中短时内间歇性猝发引起的,短时大振幅事件对底泥垂向扩散起关键作用。研究结果可为进一步研究与湍流密切相关的太湖内源释放发生机制提供参考。     

滇池沉积物内源磷释放初步研究

沉积物内源磷释放是湖泊富营养化重要的污染来源。本次研究在滇池20个采样点进行了原状柱状沉积物样品的采集。分析测试了分层沉积物样品的总磷、总氮、总有机质含量，揭示了滇池全湖沉积物中营养组分的含量特征和分布规律。为估算沉积物磷释放的通量水平和初步解释滇池磷释放的主要作用机制，现场提取出了沉积物间隙水，并分析了间隙水以及采样点湖水中溶解总磷、溶解磷酸盐和溶解有机磷的含量，根据实测运用费克扩散定律计算了沉积物-水界面之间磷的交换通量。同时对代表性样点进行了原样沉积物柱磷释放的实验室模拟。通量计算和模拟实验的结果表明，滇池沉积物具有较强的向水体的释磷能力，全湖沉积物平均磷释放通量为0．095mg／cm^2／a，沉积物磷释放成为全湖磷负荷的重要部分。实验数据相关性分析表明，滇池表层沉积磷活化释放的主要机制是表层沉积物有机质矿化降解，有机磷分解形成的浓度梯度驱动了溶解磷从沉积物向水体扩散。     

洱海沉积物磷的化学赋存形态研究

本文对洱海沉积物磷的含量、空间分布以及沉积剖面上沉积磷的化学赋存形态进行了研究。结果发现，洱海表层（5cm）沉积物中总磷的含量范围为736．40～1602．50mg／kg，平均为964．60mg／kg；北部湖区高于南部，弥苴河是湖泊的主要磷来源；洱海沉积物中各形态磷的含量高低顺序为：钙结合态磷，碎屑态磷，有机态磷，铁结合态磷，吸附态磷，磷形态的剖面变化反映了埋藏作用对沉积磷的强烈改造作用。     

Phosphorus loading to Lake Erie from the Maumee,Sandusky and Cuyahoga rivers: The importance of bioavailability

Lake Erie has undergone re-eutrophication beginning in the 1990s, even though total phosphorus (TP) loads to the lake continued to slowly decline. Using our 1982 and 2007–10 studies of the bioavailability of dissolved and particulate phosphorus export from major Ohio tributaries, together with our long-term TP and dissolved reactive phosphorus (DRP) loading data, we estimated long-term annual export of dissolved and particulate bioavailable phosphorus. DRP was found to adequately represent dissolved bioavailable export while 26–30% of the particulate phosphorus (PP) was extractable by 0.1 N NaOH, a frequently used indicator of PP bioavailability. During the period of re-eutrophication (1991–2012), DRP export from nonpoint sources in the Maumee and Sandusky rivers increased dramatically while NaOH-PP export had a slight decline for the Maumee and a small increase in the Sandusky. For the Cuyahoga River, both DRP and NaOH-PP increased, but these changes were small in relation to those of the Maumee and Sandusky. During this period, whole lake loading of both non-point and point sources of phosphorus declined. This study indicates that increased nonpoint loading of DRP is an important contributing factor to re-eutrophication. Although nonpoint control programs in the Maumee and Sandusky have been effective in reducing erosion and PP export, these programs have been accompanied by increased DRP export. Future target loads for Lake Erie should focus on reducing bioavailable phosphorus, especially DRP from nonpoint sources. Agricultural P load reduction programs should address both DRP and PP, and take into account the lower bioavailability of PP.     

Lagrangian analysis of the transport and processing of agricultural runoff in the lower Maumee River and Maumee Bay

Lagrangian analyses is used to evaluate the processing of nutrients and sediments during storm runoff events as water moved from the Maumee River loading station at Waterville, OH through the lower river, Maumee Bay and into Lake Erie's western basin. Chemical signatures of storm water at Waterville were used in combination with frequent collections of water at transects along the flow paths to evaluate processing. These signatures consisted of the contrasting chemographs of conservative parameters (chloride and sulfate), dissolved nutrients (dissolved reactive phosphorus (DRP) and nitrate) and particulate substances (suspended solids (SS) and particulate phosphorus (PP)). During low flow, sharp drops in concentrations of chloride and sulfate indicated that mixing zones between river water and bay/lake water occurred at the river mouth. During high flows, the location of the mixing zone between riverine and bay/lake water was indicated by the margin of storm-event sediment plumes, with larger storms extending further into the lake. Steep concentration gradients of DRP and nitrate between high storm water concentrations and low bay/lake water concentrations were also present at the plume margin. The large areas of storm water inside the plume margin contained high DRP and nitrate concentrations but relatively low SS and PP concentrations, due to SS and PP deposition along the flow paths. Because this deposition occurred in water with high DRP concentrations, little of the bioavailable PP was likely to have been released prior to deposition. This storm runoff water provides excellent media for algal growth.     

大型水库热分层的水质响应特征与成因分析

为研究大型水库热分层期间水质的响应特征及成因,于2018年4月-2018年12月对大黑汀水库坝前水体的水温及溶解氧等理化指标进行了连续性垂向监测,在此基础上分析了大黑汀水库季节性热分层变化规律以及各水质指标的响应特征.结果表明:(1)大黑汀水库水体呈典型的单循环混合模式,热分层期间,溶解氧在垂向分布同样表现出季节性变化...     

Water Quality Changes in Lake Erie, 1968–1980

Data on chlorophyll a, total phosphorus, and hypolimnetic dissolved oxygen concentration, which were collected by Canada Centre for Inland Waters during the period 1968 to 1980, are statistically analyzed to evaluate the changes in the water quality of Lake Erie. There are strong evidences of a decreasing trend in the value of chlorophyll a and total phosphorus in the western, central, and eastern basins of the lake between 1970 and 1980. Furthermore, a statistical model is developed for the hypolimnetic dissolved oxygen concentration in the central basin. The model shows that the increase in depletion is related to the increase in the level of total phosphorus. Hence, it is possible to improve the anoxic conditions in the lake by controlling total phosphorus loadings.     

A Post Audit of a Lake Erie Eutrophication Model

A post audit of a eutrophication-dissolved oxygen model of Lake Erie is presented. The model had been calibrated using data from 1970 and 1975. Projections were then made for use in establishing the IJC target loadings for phosphorus that would essentially eliminate the anoxia in the central basin. In the latter 1970s the phosphorus discharges to Lake Erie dropped substantially due to increased removal from point sources. The observed response of the lake to this change in loading is compared to the predicted response. A 10-year computation from 1970 to 1980 is made using measured lake loadings. Concentrations of total and dissolved phosphorus, nitrate, chlorophyll, dissolved oxygen, and anoxic area are compared to observations. Both agreements and deviations are examined. It is concluded that the IJC target loadings were reasonably accurate forecasts of the loadings required to achieve the goal of elimination of anoxia.     

Vertical Distribution of Profundal Benthos in Lake Superior Sediments

Layers of sediment in box cores from 10 Lake Superior open lake sites were sieved at 250 μm to retain benthos. The average density of benthic organisms, 3,055/m², was higher than has previously been reported for profundal regions of the lake, suggesting that biological mixing is important in the sediments. Bottom fauna were distributed from the water-sediment interface to a depth of 1.7 cm in firm glacial till and to a depth of 15 cm in soft clay. There was variability between sampling sites: oligochaetes and nematodes penetrated further into loose sediments than into compacted sand or clay. Ninety-six percent of the profundal benthos was found within the first four centimeters of sediment, with 47% between 0 and 0.5 cm (mostly Pontoporeia hoyi, naidids, sphaeriids, copepods, ostracods, and neorhabdocoels); 49% between 0.5 and 4 cm (mostly nematodes and oligochaetes); and 4% below 4 cm. The location of oligochaete cocoons containing embryos indicated that enchytraeid positions in the cores often represented their in situ vertical distribution, whereas some of the lumbriculids and tubificids migrated downward during the sampling procedures. The density and vertical distribution of Pontoporeia indicated that the potential depth and rate of biological mixing of sediment may exceed the sediment accumulation rate in Lake Superior.     

Nutrient concentrations in the surface sediments of Lake Chivero,Zimbabwe: A shallow,hypereutrophic, subtropical artificial lake

A lake‐wide survey in Lake Chivero, Zimbabwe, was performed to (i) examine the spatial distribution of three sediment grain sizes; (ii) determine their nutrient concentrations; and (iii) analyse the relationships between the measured surface sediment variables in the three sediment grain sizes. The results of this study indicated sand, silt and mud sediments occupied about 24, 22 and 54%, respectively, of the lake area. All the measured physicochemical variables varied significantly among the three sediment grain sizes (P < 0.05, anova ). High values for pH, dissolved oxygen and NO₃ were observed in the sand sediments, while water depth, electrical conductivity, soluble reactive phosphorus, NH₄, total phosphorus, total nitrogen and total organic carbon were observed in the mud sediments. In the silt sediments, most measured variables showed intermediate values. Intervariable correlation indicated varied correlation patterns among the three sediment grain sizes. Information generated in this study is essential for an accurate delineation of the spatial extent of nutrient and contaminant distribution in the sediment of Lake Chivero and will facilitate the ability of lake managers to derive a comprehensive nutrient budget of the lake as a means of establishing realistic target conditions for lake restoration.