基于TM像元的湿地土地利用生态风险评价研究

为探讨人类活动对湿地土地利用生态风险的影响,以安徽省升金湖国家自然保护区为研究区,利用1986年、2002年、2011年TM遥感影像,将土地利用类型分为8类:建设用地、草地、耕地、林地、水域、未利用地、交通用地、园地,获取不同时期的土地利用变化信息,并结合社会经济等数据,以GIS为数据分析手段,通过多元线型回归及主成分分析,建立土地利用生态风险评价模型并将土地利用生态风险指数及社会经济因子予以像元化,分析升金湖湿地土地利用生态风险时空演变规律。结果表明:1986—2011年,升金湖地区耕地面积逐渐减少,建设用地和交通用地逐渐增加,受人类经济活动的影响,保护区土地利用生态风险不断上升,生态风险面积不断扩大,其中核心区和实验区变化剧烈,而缓冲区变化相对稳定。     

Historical Trace Metal Accumulation in the Sediments of an Urbanized Region of the Lake Champlain Watershed, Burlington, Vermont

This study documents the history ofpollution inputs in the Burlington region of LakeChamplain, Vermont using measurements of anthropogenicmetals (Cu, Zn, Cr, Pb, Cd, and Ag) in four age-datedsediment cores. Sediments record a history ofcontamination in a region and can be used to assessthe changing threat to biota over time and to evaluatethe effectiveness of discharge regulations onanthropogenic inputs.Grain size, magnetic susceptibility, radiometricdating and pollen stratigraphy were combined withtrace metal data to provide an assessment of thehistory of contamination over the last 350 yr inthe Burlington region of Lake Champlain. Magneticsusceptibility was initially used to identify land-usehistory for each site because it is a proxy indicatorof soil erosion. Historical trends in metal inputs inthe Burlington region from the seventeenth through thetwentieth centuries are reflected in downcorevariations in metal concentrations and accumulationrates. Metal concentrations increase above backgroundvalues in the early to mid nineteenth century. Themetal input rate to the sediments increases around1920 and maximum concentrations and accumulation ratesare observed in the late 1960s. Decreases inconcentration and accumulation rate between 1970 andthe present are observed for most metals. Theobserved trends are primarily a function of variationsin anthropogenic inputs and not variations in sedimentgrain size. Grain size data were used to removetexture variations from the metal profiles and resultsshow trends in the anthropogenic metal signals remain. Radiometric dating and pollen stratigraphy providewell-constrained dates for the sediments therebyallowing the metal profiles to be interpreted in termsof land-use history.     

芜湖市镜湖底泥TN、TP、重金属污染及其对上覆水体的影响

采集镜湖底泥及水样,研究底泥中重金属的污染现状,分析底泥TN、TP重金属与上覆水体相同成分的相关性,结果表明：（1）镜湖底泥TN、TP与水体TN、TP含量呈有著相关性,底泥N？P释放再悬浮是镜湖水体TN、TP来源之一。（2）镜湖除Cd严重超标外,Cu？Zn？Pb含量都很低;Cd（n）与Cd（w）有较好的负相关性,Cu（n）与Cu（w）？Zn（n）与Zn（w）？Pb（n）与Pb（w）相关性差。本研究为有关部门治理和管理镜湖提供理论依据。     

安徽省巢湖流域众兴水库小流域农业面源污染调查与评价

[目的]对安徽省巢湖流域众兴水库小流域农业面源污染情况进行调查分析和评价,了解该地区农业面源污染的现状和特征,以期为制定针对性防控措施提供参考依据。[方法]应用等标污染负荷法,通过问卷调查形式对巢湖流域众兴水库小流域内进行实地的走访调研,对水库周边3个村域的种植、养殖及人居面源污染进行分类调查和核算分析。[结果](1)众兴水库项目区周边3个村落面源污染排放源中,养殖业污染物的排放量和污负荷率最大,污染物排放量达到109.00t,污负荷率最大为57.52%;种植业化肥施用带来的面源污染物总量达25.52t,负荷率为13.47%。生活污染源污染负荷为29.01%,污染物总量达到54.97t。(2)在化学需氧量(COD),TN,TP这3个评价因子中,以COD的污染负荷率最高,达74.26%;TN污染负荷率为21.13%;TP的污染负荷率为4.61%。[结论]小流域内养殖业的污染物排放是威胁众兴水库水源地饮用水安全的主要构成因子,也是农业面源污染防控的重点。     

升金湖国家自然保护区土地利用生态风险评价

[目的]为了有效保护升金湖国家自然保护区生态环境。[方法]根据安徽省升金湖国家自然保护区1986,2002和2011年3期TM遥感影像,运用ERDAS,ArcGIS等软件,结合升金湖自然保护区土地利用现状,将升金湖自然保护区试验区、核心区、缓冲区3个功能区的影像进行监督分类,划分成建设用地、草地、耕地、林地、水域、未利用地、交通用地和园地8个地类,并统计各土地利用类型面积。采用层次分析法和模糊数学法建立土地利用生态风险评价模型,计算土地利用生态风险指数。[结果]保护区整体的土地利用生态风险等级为中级,1986—2011年,土地利用生态风险逐渐增强。其中,核心区的土地利用生态风险指数相对较低,但也呈逐渐增强趋势;试验区的土地利用生态风险指数较大,缓冲区的土地利用生态风险指数变化明显,土地利用生态风险较严重。[结论]升金湖自然保护区生态风险呈上升趋势,需要采取措施,建立预警机制,有效控制升金湖的生态风险。     

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Goal, Scope and Background

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.

Materials and Methods

Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.

Results

PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K _oc) for PAHs with log K _ow<5 were positively correlated with their octanol-water partition coefficients (log K _ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K _oc′) for all PAHs were also significantly correlated with their log K _ow values (n=48, r=0.82, p<0.0001).

Discussion

In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K _oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K _oc values to log K _ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K _oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.

Conclusions

The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K _ocs and log K _ows.

Recommendations and Perspectives

Concentration, particle size and composition of resuspended particles could affect the relationship between log K _ocs and log K _ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

     

农田氮素管理模式对洱海流域大蒜生长和氮素流失风险的影响

为探求能有效提高洱海流域土壤生产力并降低氮素流失风险的适宜氮素管理模式,采用田间试验方法,研究了5种氮素管理模式对大蒜农艺性状、产量与经济效益、氮素利用率、土壤硝态氮含量及氮素表观平衡的影响。结果表明,与习惯施肥处理相比,优化施肥结合免耕秸秆覆盖可提高大蒜产量7.9%,增加经济效益14.1%,氮肥利用率增加约20个百分点,达42.3%,降低0-30cm土壤无机氮残留44.3%;优化施肥结合秸秆翻埋和优化施肥处理的大蒜产量较习惯施肥处理无显著性差异,但经济效益分别增加5.7%和3.4%,氮肥利用率分别增加约11和13个百分点,分别为32.7%和34.5%,0-30cm土壤无机氮残留分别降低60.9%和41.1%;氮素调控处理产量较习惯施肥无显著性差异,经济效益降低3.2%,氮肥利用率提高18个百分点,为40.3%,0-30cm土壤无机氮残留降低53.0%;与习惯施肥处理相比,单施牛粪处理虽然可降低0-30cm土壤无机氮残留92.4%,但大蒜减产22.8%,经济效益降低19.1%。综合研究结果可知,有机无机配施结合免耕秸秆覆盖或秸秆翻埋是洱海流域氮素管理的优化模式,是保证作物产量、提高经济效益、降低环境风险的重要措施。     

基于生态适宜度模型的城乡土地利用分区与优化布局——以鄱阳湖生态经济区为例

开展城乡土地利用功能分区和空间布局优化,是促进城乡一体化发展的有效途径。以鄱阳湖生态经济区为例,通过构建城乡土地利用生态位适宜度模型,对鄱阳湖生态经济区土地利用生态位适宜度进行了分区,并在此基础上提出了优化布局策略。结果表明:(1)鄱阳湖生态经济区布局优化为商业发展主导区、工业发展主导区和农业发展主导区以及环境保护主导区;(2)鄱阳湖生态经济区城乡土地利用空间布局可划分为核心增长极、区域中心城市、一级扩散圈、二级扩散圈和二级扩散带;(3)应从发展高新技术产业、提升都市圈核心竞争力、保障城乡用地需求、加快农田水利建设和优化生态开发利用模式等方面优化城乡土地利用空间布局。基于生态适宜度模型探讨城乡土地利用布局,为实现区域城乡均衡发展提供了新视角。     

混合浮床对南海湖湿地富营养化水体修复的作用

[目的]探究植物的交互作用对生态浮床去除N,P效率的影响,为后期南海湖湿地规模化建设提供理论依据。[方法]在自然开放水域条件下,选取适合于北方生长的3种挺水植物水葱、千屈菜、风车草为浮床植物,以高密聚乙烯空心塑料基盘为植物载体,建立单一种植与交叉混合种植两种浮床体系,在南海湖湿地保护区进行为期90 d的水质处理,研究植物生长特性及浮床净化效果。[结果] 10月份收割时,混合浮床中水葱和风车草的分蘖数分别达26和30株,生物量(鲜重)分别为1.43和1.98 kg/株。风车草浮床N累积量最好,达110.6 g/m~2,水体TN去除率34.9%。混合浮床P累积量最好,达26.02 g/m~2,水体TP去除率43.3%。[结论]植物的交互作用对植株的分蘖繁殖有一定促进作用,但不改变植物自身N,P吸收能力,植物体对N,P的累积量受生物量影响较大,3种植物在混合浮床中的整株N,P累积量要高于单植物浮床,混合浮床可作为针对南海湖富营养化水体修复的浮床形式推广使用。     

骆马湖滨岸缓冲带土壤性质的空间异质性分析

通过野外调查、采样以及地统计学的方法,研究了骆马湖东南岸有草和无草两块滨岸缓冲区土壤的氮、磷、有机质含量的异质性特征,探讨植物带对污染物的富集、截留作用.结果表明:有草区土壤的TN、TP及有机质的平均含量均大于无草区;在骆马湖滨岸缓冲带,不同的植物群落对氮、磷元素的截留、富集效率差异不大;植物群落对有机质的截留作用不明显,有草区和无草区的有机质含量的性质较为接近.滨岸缓冲带植物能够通过吸收、截留、吸附、分解等作用减少湖泊水体中的碳、氮、磷的含量.研究结果可为骆马湖非点源的治理提供理论参考,为湖泊滨岸缓冲带的研究和构建提供借鉴.