安徽省淮河流域湿地土壤养分流失及水质动态研究

以淮河流域(安徽段)湿地为研究区域,连续3a(2012—2014年)在野外调查和室内分析的基础上,采用定点实地调查、土壤和水质采样相结合的方法,研究了不同水期(平水期、丰水期和枯水期)淮河流域湿地土壤养分流失、水质动态及湿地植被多样性特征,并运用冗余分析(RDA)和偏相关分析手段揭示不同水期淮河流域湿地植被多样性与环境因子之间的关系。结果表明:(1)淮河流域湿地植被Shannon-Wiener多样性指数(H)、Pielou均匀度指数(J_P)、Margalef种类丰富度指数(d_(Ma))在丰水期达到最高,平水期和枯水期较低,基本表现为丰水期枯水期平水期,Simpson优势度指数(D)基本表现为平水期枯水期丰水期。(2)不同水期土壤pH、电导率、全盐和总孔隙度在0—40cm剖面上变化趋势基本一致,不同水期土壤pH随土层深度的增加而增加,电导率和全盐含量呈先降低后增加趋势,土壤总孔隙度呈降低趋势。(3)随着水期的变化,土壤DP、K~+、SEP和SEK呈增加趋势,在枯水期达到峰值,平水期最低,基本表现为枯水期丰水期平水期,土壤DP、K~+和SEK增加幅度逐渐增加,而土壤SEP增加幅度逐渐减小,以SEK含量波动较大。(4)水温、TN、TP、BOD5和CODCr呈一致的变化规律,随水期的变化呈先增加后降低趋势,透明度呈"V"字形变化规律,基本表现为平水期枯水期丰水期。(5)偏相关分析显示,不同水期淮河流域湿地植被多样性均与透明度呈极显著的负相关(P0.01),透明度能够反映出淮河湿地植被多样性及水质状况,影响平水期和枯水期植被多样性主要因子为BOD5浓度和CODCr浓度,影响丰水期植被多样性主要因子为TN浓度和TP浓度。     

旅游开发对湘江流域土壤重金属及水体状况的影响

以湘江流域为例,在野外调查和室内分析的基础上,调查了旅游开发区和对照区不同水期(平水期、丰水期和枯水期)不同形态土壤重金属(As、Cd、Cu、Zn、Ni和Pb)、水质(TN、TP、BOD5和CODcr)及浮游植物多样性分布状况,并运用冗余分析(RDA)的方法研究了旅游开发区和对照区浮游植被多样性与环境因子(土壤和水质)之间的关系。结果表明:(1)湘江流域旅游开发区共检出浮游植物8门273种,对照区共检出浮游植物8门203种,两者主要种类为绿藻门和硅藻门,旅游开发区和对照区浮游植物种类基本表现为丰水期枯水期平水期,局部有所波动,相同时期各藻类数目基本表现为旅游开发区对照区;(2)旅游开发区和对照区水质水温、pH、TN、TP、BOD5和CODcr浓度呈一致的变化规律,基本表现为丰水期枯水期平水期,透明度呈"V"字形变化规律;旅游开发区pH、TN、TP、BOD5和CODcr浓度均显著高于对照区(P0.05),透明度显著低于对照区(P0.05),水温并没有明显的变化趋势(P0.05),在枯水期二者之间的差距较小,说明了旅游开发对湘江流域枯水期水质的影响较小;(3)旅游开发区和对照区不同形态土壤重金属含量总体表现为丰水期枯水期平水期,旅游开发区土壤As、Cd、Cu、Zn、Ni和Pb含量分别超国家标准,其中Cd含量超标最为严重;(4)湘江流域旅游开发区和对照区土壤重金属总量与土壤有效态重金属含量均存在极显著的正线性相关关系(P0.001),说明旅游开发区和对照区土壤有效态重金属含量主要来自土壤重金属总含量。(5)冗余分析结果显示,湘江流域旅游开发区和对照区浮游植物多样性与土壤及水质状况均呈显著正相关关系(P0.01),对湘江流域旅游开发区和对照区浮游植物多样性影响最大的主要是BOD5浓度、CODcr浓度和土壤Cu、Pb含量。     

磷在沉积物-生物膜-上覆水之间迁移转化特征

以野外采样和室内模拟试验相结合,探究了生物膜附着对滇池底泥内源磷释放的影响。结果表明:(1)自然生物膜对上覆水体中的磷有较强的吸附能力和去除效果,有生物膜存在的上覆水中TP、DTP、DP含量比没有生物膜存在的上覆水中各形态磷含量分别减少36.68%,37.23%,36.12%。(2)上覆水中各形态磷含量随时间变化呈现明显的季节变化特征,夏季呈缓慢上升,秋季上升明显加快,冬季急剧降低后维持在一个较低的水平(0.094mg/L),春季又有所回升。(3)模拟试验中,沉积物中各形态磷含量均有不同程度的下降,TP、Fe/Al-P、OP和Ca-P含量分别下降了19.93%,28.03%,27.8%3和6.47%,且有生物膜存在的处理组各形态磷含量均高于对照组,说明生物膜存在可有效减少沉积物中各形态磷向上覆水的释放。     

汾河河岸带土壤氮、磷的时空分布规律及其影响因素研究

为明晰汾河临汾段河岸带土壤氮、磷时空分布规律及其影响因素,采用现场检测、空间分析及数理统计方法,探讨了自然河岸带及强人工干扰河岸带土壤氮、磷的化学计量学特征、时空分布特征及其与土壤、水文特性的相关性。结果表明:(1)各水期强人工干扰河岸带土壤TN、TP储量及其变异系数均大于自然河岸带,自然河岸带土壤氮、磷元素的生态化学计量存在弱稳态性;(2)汾河临汾段河岸带土壤TN、TP含量随枯水期—平水期—丰水期表现为先减小后增大的趋势,横向来看河岸带近岸土壤TN、TP含量大于远岸部分,土层深度方向上TN、TP含量随土层深度增加而减小;(3)河流水质、土壤容重和土壤孔隙度是影响汾河河岸带土壤TN含量的相关因子,土壤容重、土壤孔隙度和N/P是影响河岸带土壤TP含量的相关因子。研究结果表明汾河河岸带土壤氮分布与河流水文特性有一定的响应关系,土壤磷分布与河流水文特性无明显的响应关系。     

不同类型岩溶湿地表层沉积物碳氮磷生态化学计量学特征时空分布

为了厘清湿地生态系统碳汇潜力和生态系统对环境变化的响应。以滇东南典型岩溶流域普者黑为研究对象,将岩溶湿地划分为河流湿地、湖泊湿地、沼泽湿地和库塘湿地4种类型,研究湿地沉积物碳、氮和磷的平衡关系,探讨了丰水期、枯水期和平水期不同水期湿地表层沉积物碳、氮、磷的分布及生态化学计量学特征。结果表明:(1)普者黑流域不同类型湿地表层沉积物SOC,TN-S,TP-S含量在不同时期的变化规律不一致,SOC含量在平水期的库塘湿地最高,为47.81 g/kg,丰水期的沼泽湿地最低,为12.77 g/kg;TN-S含量在枯水期的沼泽湿地最高,为2.93 g/kg,丰水期的库塘湿地最低,为1.22 g/kg;TP-S含量在河流湿地最高,为1.32 g/kg,丰水期的沼泽湿地最低,分别为0.43 g/kg;且不同类型湿地表层沉积物SOC,TN-S,TP-S之间呈显著正相关(p0.05);(2)不同类型湿地表层沉积物C/N-S,C/P-S和N/P-S在不同时期下的变化规律基本一致,从枯水期、丰水期至平水期除湖泊湿地外均呈上升趋势,C/N-S和C/P-S在平水期的库塘湿地最高,分别为25.43,94.49,N/P-S在平水期的沼泽湿地最高,为4.04;C/N-S,C/P-S和N/P-S在枯水期的河流湿地最低,分别为9.17,14.85,1.62,且不同类型湿地表层沉积物C/N-S,C/P-S,N/P-S与TN-S,TP-S及水质N/P-W之间呈显著正相关(p0.05);(3)总体上看,丰水期的SOC,TN-S,TP-S含量均低于枯水期和平水期,平水期的C/N-S,C/P-S和N/P-S值均高于枯水期。     

达里诺尔湖磷赋存特征及底泥释放影响因素

[目的]揭示封闭性内陆湖磷组成特点及底泥释放影响因素,为控制达里湖磷元素污染提供理论支持。[方法]对达里诺尔湖水体总磷(TP)、溶解性总磷(DTP)、溶解性无机磷(DIP),沉积物形态磷进行监测,并利用因子分析的方法对影响沉积物底泥释放的因素分类讨论。[结果]达里湖上覆水总磷(TP)均值2.00±0.02mg/L,间隙水TP均值2.50±0.02mg/L,沉积物TP在206.09~940.49mg/kg之间。沉积物中无机磷(IP)占TP的47.9%,是沉积物主要的磷形态之一。钙磷(Ca-P)是IP中含量最多的形态磷(217.76±47.01mg/kg),其次为铁铝结合态磷(Fe/Al-P,62.73±28.34mg/kg)和交换态磷(Ex-P,36.50±19.13mg/kg),有机磷(OP,200.28±135.13mg/kg)含量占TP的41.8%;通过因子分析法将影响底泥释放的因素分为三类:沉积物TP,Ca-P,Fe/Al-P和生物有效性磷含量归为沉积物磷因子;水体pH,DO,Eh值以及间隙水磷含量归为界面影响因子;湖水水深归为湖泊自身特征因子。[结论]达里湖存在沉积物磷底泥释放的风险,根据因子分析的结果可知,影响沉积物底泥释放的因素分为沉积物磷、水—沉积物界面理化指标和湖水水深3大类。     

不同土地利用方式下土壤无机磷形态与酶活性空间变异特征

对陇东黄土高原不同土地利用方式下黄绵土和黑垆土土壤磷形态、无机磷形态和土壤酶活性的空间分布特征及其相关性进行了研究。研究结果表明,土壤无机磷（Pi）含量随土层加深均呈下降趋势;有机磷（Po）含量在果园黑垆土和菜园土中呈下降趋势;农田、苜蓿地全磷（TP）含量随土层加深呈上升趋势;各利用方式0-20cm,2040cm土层速效磷（Polt）与TP．Po呈极显著的正相关。各无机磷形态平均含量依次为Ca10—P〉Ca8-P〉A1P〉Fe-P〉Ca2-P〉O-P。黄绵土利用中Ca8-P,Al-P和Ca2-P随土层加深呈下降趋势。黑垆土农田、果园和菜园土则呈上升趋势。土壤酶活性与土壤无机磷形态相关性强弱依次为：果园〉菜园〉农田、撂荒地〉沙棘林、苜蓿地、烤烟地;与酶活性的相关性强弱的无机磷形态依次为Al-P〉Calo-P〉Ca2P〉Ca8-P〉FeP,O-P。     

基于流域尺度的农业用地景观-水质关联分析

基于Landsat遥感影像进行九龙江流域不同坡度类型的农业用地景观与水质指标（CODMn、NH4+-N、TP）的相关性分析,并分别对丰水期、枯水期、平水期的农业用地类型百分比与各水质指标进行线性回归。结果显示,坡度小于15°和大于25°的农业用地占总农业用地的面积比例与各水质指标呈较强的正相关。景观聚集度指数（CONTAG）与水体中TP浓度呈显著正相关,决定系数为0.565;香农多样性指数（SHDI）与水体中TP浓度呈显著负相关,相关系数为-0.527。丰水期和枯水期是九龙江流域水质变化较大的时期。对河流近岸100 m范围内的农业用地类型组成进行统计发现,坡度小于15°的农业用地面积平均比例为74.3%。河岸缓冲区和陡坡农业用地的数量及分布是影响该地区水质及控制农业非点源污染的关键。     

白洋淀柱状沉积物磷形态及其分布特征研究

应用淡水沉积物磷形态的标准测试方法（SMT）,调查了白洋淀6个典型湖区柱状沉积物中的磷形态分布、垂向及在两种沉积物粒级（砂土和粉砂/粘土）上的变化特征,分析了各形态磷之间的相关性。结果表明,白洋淀各湖区柱状沉积物总磷（TP）的平均含量为531~1223mg.kg-1DW,无机磷（IP）是白洋淀沉积物中磷的主要成分,占TP的72~83。湖区水体的污染及富营养化程度影响着生物可利用的铁/铝结合态磷（Fe/Al-P）在白洋淀不同湖区沉积物中的分布,从各形态磷含量和百分含量的变化幅度来看,均是Fe/Al-P〉有机磷（OP）〉钙结合态磷（Ca-P）。在垂向分布和两种粒级沉积物颗粒上,白洋淀沉积物各形态磷都有一定的变化规律,但不同磷形态的变化趋势不同,差异性也不一致。各形态磷相关性分析表明,在平均含量、垂向及粒级分布上,IP和Ca-P之间呈较好相关性,说明稳定的Ca-P是IP的主体;而在平均含量和垂向分布上,TP与IP和Ca-P之间都存在着较好的相关性,说明沉积物中TP的含量主要来自IP中的Ca-P。研究结果对于探讨白洋淀水污染沉积历史及内源磷释放对水体富营养化的贡献具有重要意义。     

巢湖沉积物磷的形态及其与间隙水磷的关系

采用磷形态的连续提取法,研究了巢湖沉积物中磷的地球化学形态及间隙水中总溶解性磷（DTP）、可溶性磷酸盐（DIP）、可溶性有机磷（DOP）含量的垂向分布特征。结果表明,西湖区的沉积物总磷含量明显高于东湖区。表层沉积物中活性磷含量占总磷的44％-81％,金属氧化物结合态磷（NaOH—P）作为活性磷的主要存在形式,在西湖区含量比例达到47％-60％,对磷释放起重要贡献;磷形态剖面表明,西湖区的金属氧化物结合态磷、可还原态磷（BD—P）含量高于东湖区。金属氧化物结合态磷、可还原态磷、钙结合态磷（HCl-P）受人类活动影响较大,有机磷（Org—P）受外源磷污染影响很小;BD—P、NaOH—P随深度增加而减小,说明巢湖近期磷负荷有增加的趋势;DTP、DIP、DOP在水-沉积物界面的浓度梯度反映它们有自间隙水向上覆水扩散的趋势;巢湖间隙水不同形态磷与BD—P、NaOH—P显著相关（α=0．01）。这项研究可为巢湖内源污染和富营养化的控制与治理提供理论参考。     

盐碱地农田排水对查干湖承泄区的水质影响评价

为了评价盐碱地农田排水对承泄区的水质影响,该文选取吉林省前郭灌区的农田排水和查干湖承泄区为研究对象,通过2009－2010年水稻生长季每月定期的野外取样、实验分析水样的K+、Na+、Ca2+、Mg2+、SO42-、Cl-、CO32-、HCO3-、总氮、总磷和化学需氧量,研究了查干湖灌溉灌排系统至承泄区相关排水水质的时空变化,并对查干湖水质进行了评价。结果表明,查干湖承泄区对灌排系统的各水质指标有一定的累积效应。目前查干湖水体pH值平均在7.87;钠吸附比最大值（3.59 (mmolc/L)1/2）出现在5月份泡田洗盐期;总氮含量为1.22 mg/L,低于近12年平均值1.56 mg/L;6月份总磷含量最高,达0.28 mg/L。除化学需氧量超标外,其他水质参数未达到浓度限值,但在丰水期查干湖水体已属IV类水质。该研究可为查干湖承泄区的生态环境预警提供理论基础。     

Laboratory-Scale Investigation of Ferrihydrite-Modified Diatomite as a Phosphorus Co-precipitant

The potential of ferrihydrite-modified diatomite as a phosphorus co-precipitant was investigated at a laboratory scale. Ferrihydrite-modified diatomite was demonstrated to effectively remove phosphorus from lake water as well as strongly bind phosphorus in sediment under anoxic conditions. Phosphorus removal from the lake water proceeded primarily through phosphorus adsorption onto ferrihydrite-modified diatomite and further phosphorus consumption by stimulated diatom growth. A total phosphorus removal efficiency of 85% was achieved when lake water was dosed with 250 mg/L ferrihydrite-modified diatomite; the residual total phosphorus concentration was 17.0 µg/L, which falls within the range for oligotrophic phosphorus levels. During a 30-day anoxic incubation period, total phosphorus concentrations in lake water treated with 400, 500, or 600 mg/L of ferrihydrite-modified diatomite slightly decreased and maximum total phosphorus concentrations remained below 15 µg/L. Addition of ferrihydrite-modified diatomite resulted in a marked increase in the iron-bound phosphorus fraction, a pronounced decrease in labile phosphorus and organic-bound phosphorus fractions, and stable aluminum-bound phosphorus, calcium-bound phosphorus, and residual phosphorus fractions in the anoxic sediments. Comparable iron-bound phosphorus concentration in the sediment treated by 400 mg/L of ferrihydrite-modified diatomite relative to that of the sediment treated by the combination of 400 mg/L of ferrihydrite-modified diatomite and alum solution at the concentration less than 532 mg/L indicated that ferrihydrite-modified diatomite exhibited a stable phosphorus-binding capacity when dosed at a similar amount. Ferrihydrite-modified diatomite had the potential to be used as an effective phosphorus co-precipitant.     

Bottom sediments in a humic lake with artificially increased calcium content: sink or source for phosphorus?

Lake Flosek (north-eastern part of Poland) is a small shallow and without outflow lake which has been limed in 1970. The concentration of Ca was increased from 3-4 mg L-1 to 17 mg L-1 in the water and from 0.2-0.3% dry weight to 0.9-1.7% dry weight in sediments (5 cm upper layer) due to CaCO3 addition to the lake. In the spring-summer seasons of 1992 and 1993, an experimental study was conducted in Lake Flosek to assess the capacity of bottom sediments to uptake and release mineral phosphorus. The rate of phosphorus exchange between sediments and near-bottom water was experimentally measured under conditions of high (100%), and of reduced (10%) oxygen saturation in near-bottom water. To determine the component of sediments responsible for the uptake of most phosphorus, the proportions of phosphorus forms in sediments were analysed. Sediments of Lake Flosek showed a slight tendency to release phosphates. The rate of this process was similar under high (100%) and low (10%) oxygen saturations ranging from - 0.161 to + 0.200 mg P m-2 d-1. This is much lower (by 1-2 orders of magnitude) than reported from other harmonic, non-humic lakes. In the total phosphorus pool, the highest content of phosphorus was found in the organic and residual phosphorus fractions (over 70% of the total phosphorus in sediments). The largest part of the readily extractable phosphorus was found in the fraction bound to Al and humic substances (41%). Both these fractions determine a weak exchange of phosphorus between sediments and water. No difference in P-release related to P-fraction compound was found in the cores taken from three sites in the lake.     

滇池沉积物的功能: 磷源还是磷库?

Dianchi Lake is a highly eutrophic lake in southwestern China where phosphorus (P) is the limiting element for eutrophication and where lake sediments play an important role in the P cycle. One hundred and eighteen sites were sampled throughout Dianchi Lake in 2002 to investigate the P loading of the lake sediments, while fresh surface sediments were studied in the laboratory to clarify its role for phosphorus. The results showed that concentrations of total phosphorus (TP) in sediments were very high, with a maximum value of 6.66 g kg^-1, and decreased with sediment depth. P adsorption on surface sediments was rapid with adsorption amounts higher in acidic than in alkaline conditions. The release experiments showed that P release increased as pH rose from 7.0 to 10.5. Additionally, compared with aerobic conditions, P release was much higher under anaerobic: conditions, especially with low P content in the lake water. At present, the sediments in Dianchi Lake still function as a sink for phosphorus at high P levels in lake water. However, if the external P load was reduced and P content in lake water became low, the sediment would have a large potential for P release under anaerobic conditions.     

Lake Sediments from Dianchi Lake： A Phosphorus Sink or Source？

Dianchi Lake is a highly eutrophic lake in southwestern China where phosphorus (P) is the limiting element for eutrophication and where lake sediments play an important role in the P cycle. One hundred and eighteen sites were sampled throughout Dianchi Lake in 2002 to investigate the P loading of the lake sediments, while fresh surface sediments were studied in the laboratory to clarify its role for phosphorus. The results showed that concentrations of total phosphorus(TP) in sediments were very high, with a maximum value of 6.66 g kg^-1, and decreased with sediment depth. P adsorption on surface sediments was rapid with adsorption amounts higher in acidic than in alkaline conditions. The release experiments showed that P release increased as pH rose from 7.0 to 10.5. Additionally, compared with aerobic conditions, P release was much higher under anaerobic conditions, especially with low P content in the lake water. At present, the sediments in Dianchi Lake still function as a sink for phosphorus at high P levels in lake water. However, if the external P load was reduced and P content in lake water became low, the sediment would have a large potential for P release under anaerobic conditions.     

太湖人工恢复湿地区植物群落建植对沉积物中氮、磷空间分布的影响

采用地统计学与GIS相结合的方法,以太湖百渎港湿地植被恢复区为研究区,研究了人工湿地植物群落沉积物中全氮、全磷和有效磷的空间分布特征,阐明了不同植物群落建植对氮、磷的拦截、沉积作用效果,以期为太湖水污染控制和湿地环境保护与修复提供科学依据。结果表明：（1）研究区全氮变化范围为0.37～5.42g/kg,全磷为1.01～9.06g/kg,有效磷为150～760mg/kg,全氮、全磷和有效磷都存在空间上中等程度的变异性。（2）芦苇群落对氮和磷的拦截、沉积效果最好,香蒲群落、茭草群落、荷花群落以及沉水植物群落由于受植物密度、分布位置以及自身生物学等因素的影响,表现出一定的差异性,但都强于分布植物较少的对照区。     

连环湖敖包泡沉积物磷形态垂向分布特征

应用SMT连续提取法对连环湖敖包泡北部(AB1)和南部(AB2)柱状沉积岩芯中磷形态的含量和垂向分布特征进行对比分析,结合沉积岩芯年代测定,探讨了该湖区沉积物中磷的演化特征与人为污染历史以及内源磷的释放风险。结果表明,AB1、AB2沉积物中磷形态的含量和垂向变化不同,AB1沉积物中各形态磷含量均高于AB2,且随深度变化波动较大。20世纪40年代中期至1981年,AB1沉积物各形态磷和OM含量波动较大;AB2沉积物中Ca-P、IP、TP含量呈先增加后减少之势,Fe/Al-P、OP、OM含量变化较稳定。1981—2009年,AB1沉积物Ca-P、IP、OM含量变化较小,Fe/Al-P、OP、TP含量相对波动较大;AB2沉积物Ca-P、Fe/Al-P、TP含量不同程度上先增加后减少,IP、OP、OM含量变化均呈增加趋势。连环湖敖包泡沉积物磷人为来源以工业废水、居民生活污水和农药化肥的流失为主。湖泊北部磷含量高于南部,这与人类活动强度密切相关,敖包泡北部附近村落密集而南部没有村落。应用单一因子标准指数法对湖泊表层沉积物磷素进行生态风险评价表明,湖区北部表层沉积物总磷含量超标,存在一定的安全风险,同时AB1沉积物上部较底部活性磷(Fe/Al-P和OP)增加较多、且活性磷(Fe/Al-P和OP)是AB1沉积物磷增加的主要形态,因此连环湖敖包泡沉积物中磷向上覆水体释放的风险增加,对湖泊水体的富营养化的影响应予以关注。     

Internal Phosphorus Loading from the Bottom Sediments of a Dimictic Lake During Its Sustainable Restoration

The ribbon type Lake Durowskie (Western Poland) is currently undergoing a sustainable restoration process due to water quality deterioration, manifested in water blooms, low transparency, and oxygen deficits near the bottom sediments. Three restoration methods were applied: (i) hypolimnion aeration using two wind-driven pulverizing aerators installed at the deepest places, (ii) phosphorus inactivation using small doses of iron sulfate and magnesium chloride several times a year, and (iii) biomanipulation using pike fry stocking. Research on the exchange of phosphorus in the sediment-water interphase was conducted in the years 2009–2016 to determine the multiannual changes of internal phosphorus loading from bottom sediments during the restoration process. The sustainable approach resulted in a decrease of internal phosphorus loading and a gradual increase in the sorption capacity of bottom sediments, particularly noticeable in the last 2 years. The content of phosphorus in the sediment and in the interstitial water fluctuated, showing an increase during the first years of restoration and then a gradual decrease. It was proved that the process of sustainable restoration is cheap and does not interfere strongly with the ecosystem, although it is long-lasting. It should be continued for many years, especially in the case of continuous external loading of the lake with nutrients from the catchment area, i.e., until the water quality in the main tributary improves and the lake ecosystem stabilizes.     

Effect of Lake Management Efforts on the Trophic State of a Subtropical Shallow Lake in Lakeland, Florida, USA

For more than a decade, Lakeland, FL, has invested in restoring its urban Lake Hollingsworth from a hypereutrophic state to its natural eutrophic state. The lake bottom was dredged of nearly 2 million m³ of accumulated organic sediments, and treatment wetlands, storm water curb inlet strainers, and a storm water baffle box were installed within the lake’s catchment area to reduce the loading of dirt, leaves, and trash to the lake. After dredging ceased, the lake was dosed one time with alum to improve water clarity and reduce phosphorus recycling from its sediments. Water quality surrogates for algal biomass— Secchi disk transparency and water column total nitrogen, total phosphorus, and chlorophyll-α concentrations— were reviewed to assess Lakeland’s progress towards its goal. In the years since dredging has stopped, algal biomass concentration in Lake Hollingsworth has significantly declined. Even with these improvements, however, the lake still remains hypereutrophic.     

Development of a fugacity/aquivalence model of mercury dynamics in lakes

A simple, mechanistic model of mercury (Hg) dynamics in a lake has been developed, based on the fugacity/aquivalence approach of Mackay (1991) and Mackay and Diamond (1989) and its extension to treat several interconverting chemical species (Diamond et al., 1992). The model considers the distribution of inorganic (HgII), elemental (Hg°) and methyl (MeHg) mercury species between dissolved and particle-sorbed phases, and fate and transport in a system consisting of a well-mixed water column and an active sediment layer. Hg can enter the lake from watershed runoff and by atmospheric deposition directly to the lake surface. Once in the lake, Hg exchanges between water and air, and water and sediments, and exits by sediment burial, advective flow and volatilization. The model was applied to a hypothetical drainage lake on the Canadian Shield. Model estimates of water and sediment concentrations compare well with measured values. The results suggest that the three Hg species experience significantly different fates and persistence, with overall Hg dynamics dominated by the fate of HgII (the predominant species). A sensitivity analysis illustrates the importance of physical/chemical properties and lake characteristics on the total amount and behavior of Hg in the lake.