太湖表层沉积物中多磷酸盐检出的环境意义

在氮限制型富营养化湖泊中,沉积多磷酸盐(Poly-P)可以用来示踪营养盐磷的输入和湖泊的富营养化过程。太湖是一个典型的磷限制型富营养化湖泊,通过对太湖表层沉积物中总有机碳(TOC)、总氮(TN)、总磷(TP)、氢氧化钠可提取磷(NaOH-P)以及Poly-P的提取分析,初步探讨了太湖营养盐磷输入的历史记录,并揭示了该湖Poly-P的主要来源和保存机制。太湖Poly-P的质量浓度较低,变化范围为0.004~0.065mg·g-1。NaOH-P占TP组成的22%,是太湖沉积物总磷的主要组成部分之一。结果显示,在湖泊水体藻类生物量较大和NaOH-P是沉积物TP重要组成部分的磷限制型湖泊中,Poly-P也是沉积物磷汇组成的一个重要部分,同时还是一个可以反映由人为磷输入增大导致湖泊富营养化程度加剧的敏感指标。     

湖泊沉积物对磷酸盐的负吸附研究

分别在高、低两种磷酸盐质量浓度下，研究了6个湖泊沉积物对磷酸盐的负吸附。结果表明，(1)污染严重的湖泊沉积物不仅在上覆水体水质好转时，可能向上覆水体释放磷，即使上覆水体水质没有好转，在一定条件也可能释放；而较为清洁的湖泊沉积物，在上覆水体水质下降时，可能从上覆水体中吸附磷。在水质好转情况下，也可能向上覆水体中释放磷。(2)湖泊沉积物吸附磷酸盐过程中存在负吸附，吸附研究中使用较高质量浓度磷溶液是负吸附现象被掩盖的原因；在吸附研究中不仅要重视负吸附，而且初始磷酸盐质量浓度不能太高。(3)沉积物对磷酸盐的吸附／解吸平衡质量浓度与其有机质、CEC、总氮、总磷以及各形态磷含量均有显著的正相关关系，相比而言。与总磷以及各形态磷含量的相关性最高。污染较为严重的沉积物对磷酸盐的吸附／解吸平衡质量浓度也较高。     

太湖不同湖区无机氮转化潜力

采集太湖梅梁湾和东太湖的水样和积物,在实验室内模拟研究不同湖区水体中溶解性无机氮(DIN)短期内的转化潜力.研究结果表明,太湖藻型湖区(梅梁湾)和草型湖区(东太湖)水体中存在着强烈的硝化作用,NH 4-N和NO3-N含量之间表现出显著的负相关关系(P＜0.05或P＜0.01),NH 4-N质量浓度下降速率为0.08～0.19 mg·L-1·d-1.在同样的试验条件下,藻型湖区硝化速率高于草型湖区.NH 4-N初始浓度越高则硝化速率也越高,不添加外源氮时硝化速率随着时间的推移而逐渐降低.藻型湖区的反硝化作用强于草型湖区.室内模拟试验20 d后,沉积物中TN含量平均下降了3.7%,东太湖水样中平均下降26.7%,梅梁湾平均下降42.2%.湖泊沉积物是进行反硝化作用的重要场所.短期内DIN的转化潜力反映了不同湖区氮素转化速率,也反映了不同生态类型水体对湖泊氮素转化的影响.     

水动力过程后湖泊水体磷素变化及其对富营养化的贡献

对水动力过程后水体磷素的变化作了研究，并就其对富营养化的贡献作了分析探讨。研究表明，水动力过程后，TP的质量浓度因重力对含磷颗粒的作用而随沉降时间的延长而渐渐变小，且初期幅度大，后期则趋于平稳；而TDP的质量浓度则在初期因悬浮物的脱附作用而增大，继而随着悬浮物的粘带作用沉降而减少，但经足够长的静置沉降，其又由于水底沉积物的释放作用而增加，有初期“汇”，后期“源”的特点。而分析则表明：水动力过程后。水体磷素会因沉降而变小，但在相当长(50min)的时间里，其质量浓度仍处于高值，从而为湖泊的富营养化提供了最为必要的营养成分，加上不停地受到包括风动力在内的影响，这应是浅水湖泊富营养化，并难以治理的根源。     

绿潮藻类暴发对天鹅湖水体和沉积物磷含量的影响

在荣成天鹅湖藻类暴发区域采集新鲜沉积物和丝状硬毛藻（Chaetomorpha spp.）,进行室内模拟试验,监测了生长过程中硬毛藻的生物量、磷富集量以及不同处理水体总磷（TP）和可溶性磷（SRP）质量浓度的变化,并分析了藻类生长对沉积物中各形态磷含量的影响。结果表明,当水体磷含量较高时,硬毛藻生长较快,相对生长速率高达14.88%,之后随着水体磷浓度的下降,生长速率逐渐减小。不同处理间硬毛藻的生物量相差很大,高磷含量处理显著高于低磷处理,最大差值可达26.50 g。随着藻类的生长,水体TP和SRP含量明显降低,其中高磷含量处理的TP质量浓度由0.93 mg·L-1降至0.01 mg·L-1,低磷含量处理水体SRP质量浓度均降至0.006 mg·L-1以下。当水体磷含量降至一定水平,沉积物中磷可向水体释放,其中可还原态磷和铁铝结合态磷的降幅分别为23.98%和12.61%。在高磷含量处理组,藻体中磷的富集量显著升高,且当水体磷含量相同的条件下,有沉积物处理的富集量显著高于无沉积物处理。相关分析表明,藻体生物量与水体TP和SRP的相关性较好,其中高磷含量处理组生物量与水体TP、SRP呈高度负相关,而相对生长速率与之呈显著正相关。结果说明,水体及沉积物中磷均可作为硬毛藻生长的营养来源;另一方面,藻类生长可明显降低水体磷含量,并促进沉积物中磷的释放。     

化学物添加控制湖泊内源磷负荷的有效性研究

利用太湖五里湖湖水和未受破坏原柱状沉积物样组成的系统进行投加生石灰、铁盐和铝盐的湖水脱磷效果的实验室研究。分别一次性向各柱状样上覆水体中投加6种不同质量浓度的铝盐、钙盐和铁盐溶液,经过一段时间的观察和测定。结果表明,3种化学物的添加均能使实验上覆水体中总磷质量浓度大幅度降低,并且随着投加的生石灰、铁盐和铝盐的量的增加,上覆水体中总磷的质量浓度下降幅度越大,水体中总磷的去除率越高,同时这3种化学物的添加对湖泊沉积物内源磷的释放有一定的抑制作用。     

鄱阳湖沉积物中磷吸附释放特性及影响因素研究

沉积物是氮磷营养盐的主要蓄积库,它不仅是外来污染物的归宿地,同时其自身营养盐的释放也可对水环境产生重大影响。针对鄱阳湖存在的沉积物磷释放问题,关键环境因子对基质磷吸附的影响规律进行了探讨。通过控制在不同环境因素条件下,上覆水中磷的变化规律探讨,阐明磷在上覆水-底泥界面迁移转化的规律和环境因素对迁移转化过程的影响。研究结果表明,吸附初始阶段,两者含量相差较大,起始吸附速率很高;随着反应时间的推进,两者含量差随之减小;当吸附时间达到30 min时,此时上覆水的平衡质量浓度为8.648 mg·L^-1,两者含量达成平衡。由磷的吸附等温试验同样可看出,随着平衡质量浓度逐渐增加,土壤吸磷量刚开始增加较快,随后增加趋势逐渐减缓直至磷饱和。pH越小,上覆水质量浓度越低,沉积物对磷的吸附作用越强;pH越大,上覆水中TP质量浓度越大,强碱条件下,TP吸收量剧减。在好氧条件下,沉积物对磷的吸附远远高于厌氧条件下沉积物的吸附。好氧条件下,反应在4 h内,沉积物对磷的吸附速率最高,随后吸附量很小直至逐渐饱和。厌氧条件下,吸附作用不明显;当反应时间达到24 h后,上覆水磷质量浓度保持不变,此时沉积物磷吸附达到饱和。高溶解氧水平对于控制底泥向上覆水体释放磷,维持水体较低总磷是必要的。温度为30℃,20℃和5℃3种条件下,当反应24 h后,三者均达到吸附平衡。因此,当上覆水的磷质量浓度较低时,高温条件下基质的磷释放速度会高于低温条件下的磷释放速度。研究结果旨在为正确认识、合理评估环境因素对湖泊水体磷的影响提供更为充分恰当的试验依据和理论解释。     

中国东部浅水湖泊沉积物总氮总磷基准阈值研究

受人类活动的影响,东部浅水湖泊沉积物中总氮、总磷负荷很高,当外来污染源得到控制时,底泥中的营养盐会逐渐释放出来,对湖泊水质与生态系统影响很大。为合理削减湖泊内源污染,控制沉积物中营养盐向上覆水体释放,研究制定东部浅水湖泊沉积物总氮、总磷基准阈值,分别测定了100个湖泊的896个表层沉积物样品和8个典型湖泊11个柱芯的沉积物总氮（TN）、总磷（TP）含量,分析了沉积物TN、TP浓度剖面分布特征。通过频度分布法对100个湖泊沉积物总氮总磷的污染状况进行评价,通过背景值比较法确定了8个典型湖泊沉积物的TN、TP背景值。结果表明,100个湖泊的表层沉积物TN浓度范围在479.70~5 573.65 mg·kg-1,TP浓度范围在248.44~1000.33 mg·kg-1,不同湖泊表层沉积物中TN、TP值差异较大。8个典型湖泊沉积物总氮、总磷含量整体上表现出随着深度增加而下降变化趋势,在深层沉积物中含量保持稳定。所调查8个湖泊TN均值为1443.83 mg·kg-1,变化范围为247.45~3719.46 mg·kg-1,各湖泊中TN均值表现为：沱湖〉焦岗湖〉花园湖〉七里湖〉北民湖〉大通湖〉城东湖〉瓦埠湖;TP均值为519.62 mg·kg-1,变化范围为225.41~1944.89 mg·kg-1,各湖泊中TP均值表现为：北民湖〉大通湖〉七里湖〉焦岗湖〉沱湖〉瓦埠湖〉城东湖〉花园湖。不同湖泊沉积物总氮、总磷背景值差异很大。通过对100个湖泊表层沉积物TN、TP的频度分析发现,沉积物营养盐含量上25%点位对应的TP质量浓度398.51mg·kg-1,TN质量浓度为1106.24 mg·kg-1,沉积物营养盐含量下25%点位对应的TP质量浓度664.58 mg·kg-1,TN质量浓度为2916.66 mg·kg-1。通过互相之间的比较分析,推荐采用背景值比较法确定的各湖泊沉积物总氮、总磷背景值均值与频度分步法25%点位对应的总氮值和40%点位对应的总磷值作为东部浅水湖泊沉积物总氮、总磷基准阈值。因此,?     

菹草生长对沉积物间隙水中各形态磷浓度的影响

通过人工构建湖泊生态系统,用湖泊沉积物的上层泥和下层泥分别代表清淤前后的2种基质,研究菹草(Potamogeton crispus)生长对沉积物不同层次间隙水中各形态磷浓度的影响.垂直方向上,将2种基质中的间隙水分为表层、中层和底层3个层次.结果表明,菹草生长能够不同程度地降低各层间隙水中磷浓度,上层泥和下层泥2种基质均表现为表层间隙水溶解性总磷(DTP)和溶解性活性磷(SRP)含量降低幅度最大,DTP含量分别降低68.97％和83.09％,SRP含量分别降低54.57％和96.02％.菹草的吸收作用使得各层间隙水中磷浓度均低于无沉水植物的对照组.试验结束时,2种沉积物中TP含量降低幅度差异不显著,说明疏浚前后种植菹草均可有效控制湖泊内源磷污染.     

生态修复对浅水湖泊沉积物磷形态特征及湖水磷浓度的影响

以恢复沉水植物为主要手段在浅水富营养化湖泊修复中得到广泛应用,但修复后水质差异很大,可能与沉积物特征有关.暨南大学南湖是浅水富营养化湖泊,在削减外源负荷后,实施了沉水植物恢复等修复工程.本研究选择具有不同水质的区域,采集水样与沉积物,分析沉积物NH4Cl-P(弱结合态磷)、Fe-P(铁结合态磷)、Al-P(铝结合态磷)、Bio-P(细菌可利用性磷)、Ca-P(钙结合态磷)和Ref-P(残渣磷)6种形态的磷,并检测水质差异,以探讨生态修复对沉积物磷形态及水体磷浓度的影响.结果显示,沉水植物较丰富的2号点沉积物密度显著高于沉水植物较少的1号点,2号点沉积物中Fe-P、Al-P和Ref-P含量较高,沉积物磷最大释放潜力(P-MSP)为4.87 mg/L,大幅高于1号点的2.58mg/L,然而2号点水体磷浓度却低于1号点,1号点水体的总磷、颗粒态磷、总溶解性磷和溶解活性磷浓度分别为2号点的1.29倍、1.11倍、1.17倍和1.14倍,水质较2号点差.本研究说明沉水植物能抑制沉积物中磷的释放,提高沉积物对磷的滞留能力,从而降低水体磷含量,改善水质.     

Source identification and prediction of nitrogen and phosphorus pollution of Lake Taihu by an ensemble machine learning technique

● A machine learning model was used to identify lake nutrient pollution sources. ● XGBoost model showed the best performance for lake water quality prediction. ● Model feature size was reduced by screening the key features with the MIC method. ● TN and TP concentrations of Lake Taihu are mainly affected by endogenous sources. ● Next-month lake TN and TP concentrations were predicted accurately. Effective control of lake eutrophication necessitates a full understanding of the complicated nitrogen and phosphorus pollution sources, for which mathematical modeling is commonly adopted. In contrast to the conventional knowledge-based models that usually perform poorly due to insufficient knowledge of pollutant geochemical cycling, we employed an ensemble machine learning (ML) model to identify the key nitrogen and phosphorus sources of lakes. Six ML models were developed based on 13 years of historical data of Lake Taihu’s water quality, environmental input, and meteorological conditions, among which the XGBoost model stood out as the best model for total nitrogen (TN) and total phosphorus (TP) prediction. The results suggest that the lake TN is mainly affected by the endogenous load and inflow river water quality, while the lake TP is predominantly from endogenous sources. The prediction of the lake TN and TP concentration changes in response to these key feature variations suggests that endogenous source control is a highly desirable option for lake eutrophication control. Finally, one-month-ahead prediction of lake TN and TP concentrations (R² of 0.85 and 0.95, respectively) was achieved based on this model with sliding time window lengths of 9 and 6 months, respectively. Our work demonstrates the great potential of using ensemble ML models for lake pollution source tracking and prediction, which may provide valuable references for early warning and rational control of lake eutrophication.     

基于实测高光谱数据的太湖悬浮物浓度与透明度分区

通过实地测量太湖水体的反射光谱和表层水质,利用实测数据以及水-气界面辐射传输模型计算其遥感反射率,并根据太湖的实际水质状况将其划分为3个区域,分别分析太湖总体和分区的反射光谱曲线,建立太湖不同区域水体悬浮物浓度和透明度的反演模型。结果表明,就悬浮物浓度和透明度而言,太湖3个区域中以东太湖水质最佳,贡湖、梅梁湖和竺山湖次之,南部和西部最差;对太湖进行分区研究能够更好地反应太湖水质的差异性,拟合各区域的水质状况,分区模型精度较全湖区模型高,误差也普遍较小,能够提高研究结果的可信度和可行性。     

Impact of climate factors on cyanobacterial dynamics and their interactions with water quality in South Taihu Lake,China

Cyanobacterial bloom events in South Taihu Lake cause serious water quality problems and disturb aesthetic view of lake’s environment. In this study, correlations between cyanobacterial blooms and hydro-meteorological factors, including water quality, temperature and precipitation were investigated. Results demonstrated that South Taihu Lake was heavily affected by cyanobacteria and the proliferation of cyanobacteria due to variations in hydro-meteorological factors and water quality conditions. Water quality parameters, including COD, NH₃-N, TN and TP improved significantly since 2008 even at an elevated cyanobacterial bloom situation. Correlation analyses have shown that the development of cyanobacterial density and chlorophyll a concentration was sensitive to a wider temperature variation. The optimum temperature for cyanobacteria was 20°C, while extremely low and high temperatures were found to suppress their growth. Moreover, unusual rainfall patterns were measured during the study period (2003–2009), which showed an adverse impact on cyanobacterial development. Findings from this study suggested that seasonal lake’s water quality monitoring; suitable treatment of cyanobacterial blooms and strict policy implementation can solve the water quality issues in highly eutrophic lakes like Taihu.     

太湖重污染湖区和水源地水质概况及藻毒素污染环境风险

近年来太湖流域局部水质状况有所改善,但太湖藻型生境条件还未根本改变,水污染防治任务依然艰巨。确保太湖湖体水质稳定达标,尤其是加强对太湖重点湖区和水源地重点污染物的调查研究十分重要。在此背景下,本文调研了太湖重点湖区和水源地水质概况、藻毒素污染时空分布特征、环境影响因子和迁移转化规律,并总结了藻毒素的环境和健康风险研究的最新进展,指出了太湖西部湖区和饮用水源地的主要环境风险,以及未来太湖藻毒素污染相关研究需解决的关键技术问题,以期为促进太湖流域重点污染物的控制和治理,确保太湖饮用水源地安全提供有益借鉴。     

外源性污染对太湖梅梁湾水质影响的定量化

通过太湖的水量水质数学模型,模拟了梅梁湾内主要的入湖污染源———直湖港、武进港和梁溪河排入的污染物质的迁移、转化规律;分析了梅梁湾中梅园、小湾里、闾江口、拖山4个监测点水质浓度受直湖港、武进港和梁溪河排污影响程度的大小;并分别建立了监测点污染物浓度与排污口排污量的响应关系曲线和响应关系表达式。通过这些结论可以方便的定量的计算出在排污口排污量发生变化的情况下监测点水质浓度的变化量,为合理控制外源污染物质的入湖量提供了技术支持。     

Assessment of nutrients and heavy metals enrichment in surface sediments from Taihu Lake,a eutrophic shallow lake in China

Concentrations of the nutrients (TN and TP), phosphorus fractions and heavy metals (Co, Cr, Cu, Mn, Ni, Pb, Sr, Ti, V, Zn and Hg) in 40 surface sediment samples collected from Taihu Lake, a eutrophic shallow lake in China, were determined. The results showed that the northwest region of the lake possessed higher concentrations of TN and TP, as well as the similar spatial distribution trend in the water column. This should be related to excessive anthropogenic input from industrial effluents and domestic sewage in surrounding areas. Similarly, the concentrations of P fractions exhibited significant regularity. In addition, except for Sr showing low concentration, the rest of the heavy metals in the surface sediments had two- to four-folds of magnitude of the concentrations compared with the reference values in earth's crust. In the past decade, concentrations of heavy metals had undergone different levels of variations. Principal component analysis (PCA) and enrichment factors (EFs) of the compositional data aiming at heavy metals showed that Taihu Lake was slightly exposing to heavy metal contamination except Sr. High concentrations of heavy metals were ascribed to the discharge of untreated and partially treated industrial waste water via rivers. Co, Cr, Cu, Mn, Ni, Pb, V and Zn positively correlated with each other (R = 0.78–0.92), that indicated they had analogous sources and/or kindred geochemistry characteristics. Differing from nutrients, randomness in the space indicated that heavy metals had a complex distribution.     

太湖流域水源地多氯联苯分布特征与污染水平

为系统了解太湖流域主要水源地多氯联苯(PCBs)的污染现状,于2012年3月和6月分别采集水相、悬浮颗粒物和沉积物样品,并利用气相色谱-质谱联用仪(GC-MS)对PCBs的浓度进行了分析。结果表明,3月水相、悬浮颗粒物和沉积物中均未检测出PCBs类物质。6月水相中PCBs质量浓度在ND~1.04 ng·L~(-1)之间,平均值为0.57 ng·L~(-1),悬浮颗粒物和沉积物中PCBs质量浓度分别在0.96~2.72 ng·g-1和0.47~1.29 ng·g-1之间。Aroclor 1016和Aroclor 1260在3种介质中均有检出,且Aroclor1016浓度均为最高。与国内外研究相比较,太湖流域主要水源地PCBs污染水平较低。水相中PCBs浓度水平低于我国地表水环境质量标准;悬浮颗粒物和沉积物中PCBs浓度水平均低于加拿大保护水生环境沉积物化学品风险评价标准的LEL值,说明各样点PCBs对底栖动物无毒性影响。     

固定化藻膜去除水中氮磷的模拟研究

针对富营养化水体生物修复和污水深度处理氮磷的去除,将细颤藻、水绵、水网藻、栅裂藻固定在纤维填料上,形成固定化藻膜。用固定化藻膜处理模拟富营养化湖水、实际富营养化湖水、城市污水二级出水、低质量浓度生活污水,考察固定化藻膜去除氮磷的效果。实验结果表明,固定化藻膜具有良好的去除磷、氨氮能力,对水中有机物去除也有一定的促进作用。对TP质量浓度小于5.0mg·L-1,NH4 -N质量浓度小于34.0mg·L-1的污染水体,四种藻膜都有良好的去除氮磷能力,其中栅裂藻去除TP、NH4 -N的能力最强。综合除污能力和藻细胞的可固定性,水绵应是最佳的备选藻种。研究结果显示,固定化藻膜具有良好的除污性能,预示了悬浮载体将在水体生物修复、氧化塘污水处理方面具有重要的潜在应用价值。     

A study on physicochemical parameters of an aquaculture body in Mysore city, Karnataka, India

Monthly changes in water quality parameters (physicochemical) of a rain fed lake (Bilikere) in Mysore city, were investigated for two calendar years (2002 and 2003) to assess the suitability of this lake for pisciculture. Although there were monthly fluctuations in water temperature, total suspended solids (TSS), dissolved oxygen (DO), nitrite and ammonia, they were within the desirable limits. On the other hand, total alkalinity and hydrogen sulphide throughout the study period and pH for a major part, were higher than the desirable limits. Other parameters viz; turbidity, biological oxygen demand (BOD), phosphate, and nitrate in a few months were higher than the desirable limits for waters used for fish culture. The high levels of these factors are due to the entry of agricultural run off and occasional flow of sewage into the lake. In addition dense algal growth was noticed at times of the year which is caused by surge in nutrients level whenever there was a rainfall. Since, the lake has a great aquacultural potential, it is suggested that control of nutrient load that enters the lake occasionally, might help the lake to continue its mesotrophic status.