太湖地区地表水氮污染源的评论

The nitrogen （N） pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system （GPS）. The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region.     

鄱阳湖湿地生态系统功能评价及其利用保护对策

鄱阳湖国家级自然保护区位于中国第一大淡水湖———鄱阳湖西北角,是生物多样性非常丰富的国际重要湿地。保护区总面积22400hm2,栖息的鸟类有310种,数量多达数100000只。论述了鄱阳湖湿地的生物多样性,对其功能进行了综合概述和评价,针对其面临的主要生态问题,提出了相应的合理利用和保护对策。     

环太湖耕地利用变化与驱动机制研究——以苏州市吴中区为例

以环太湖苏州市吴中区为样区,利用统计资料、遥感数据和典型调查数据,结合RS和GIS技术,分析18年来耕地利用变化特点与驱动机制。结果表明:研究区耕地年递减率为1.6%,表现出以水域和各类非农建设用地大量占用耕地为突出特点的区域土地动态变化特征;耕地数量变化与区位和地形有关;种植业对耕地利用强度出现波动下降趋势,作物生产由粮食作物生产为主转化为粮食与经济作物生产并重;其变化机制主要是经济发展、人口增长、农业结构调整和政策因素驱动。最后,并在此基础上提出相关建议。     

洞庭湖区不同土地利用方式耕作土壤氮素含量与循环

通过对洞庭湖典型地区的密集采样分析和农户调查,研究了4种利用方式耕作土壤全N、微生物生物量氮(MB-N)含量、两者关系和N素循环特征。结果表明:耕作土壤全N、MB-N含量平均值为3.00±0.48g/kg和101.4±49.2mg/kg。双季稻、一季稻、水田旱作和旱地全N平均含量依次为3.12±0.40g/kg、3.03±0.39g/kg、2.79±0.43g/kg2、.10±0.46g/kg。4种利用方式的MB-N含量分别为124.0±56.6mg/kg、96.4±39.2mg/kg、108.0±48.6mg/kg、75.2±30.5mg/kg。除水田旱作外,MB-N与全N之间存在极显著的正相关关系(P<0.01)。土壤N素盈余量依次为双季稻(105.0kg/hm2.a)>一季稻(75.1kg/hm2.a)>水田旱作油菜(64.5kg/hm2.a)>旱地苎麻(51.9kg/hm2.a)。     

近20年太湖流域典型区土壤养分时空变化及驱动机理

长期的定位采样试验研究了近 2 0年锡山市甘露乡土壤表层 ( 0～ 2 0cm)中有机质、全氮、速效氮、速效磷、速效钾等土壤养分的时空变化趋势 ,并分析了土壤养分波动与国家政策、耕作方式、农业投入和单位面积农业纯收益之间的相互关系。结果表明 :2 0年间土壤养分质量总体上呈现先减后增的变化趋势。有机质呈现先减后增的变化趋势 ,且与耕作措施的改变有密切关系。全氮和速效氮呈持续上升趋势 ,上升幅度大于 1 0 0 % ,与氮肥使用量不断上升密切相关。速效磷、速效钾呈持续下降趋势 ,与磷肥、钾肥使用过少有关。国家政策和耕作方式、种植制度对SNQI影响十分明显 ,标准农业投入与土壤养分质量指数呈正相关关系 ,单位面积标准农业纯收益与土壤养分质量指数呈负相关关系     

Turf-banked terrace treads and risers, turf exfoliation and possible relationships with advancing treeline

Fine-scale geomorphic/pedogenic processes at alpine treeline may facilitate the initial stages of conifer invasion of alpine tundra. Turf-banked terraces and turf exfoliation associated with solifluction may provide both the topographic protection and the seedbed necessary for conifer establishment above treeline. The morphometry, stoniness and surface penetrability of turf-banked terraces were recorded. Whereas differences among sites exist due to topographic constraints, differences in soil penetrability depend on turf exfoliation. Exfoliated turf risers are significantly more penetrable than non-exfoliated solifluction risers and adjacent treads. These penetrable microsites provide favorable conditions for seed germination. The process of turf exfoliation may play a role in conifer advance into tundra during climatic change.     

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.

     

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。     

巢湖流域土地利用程度变化及其空间异质性分析

基于GIS和遥感平台提取巢湖流域范围,分析了2000-2013近15年来的巢湖流域土地利用程度及其空间异质性特征。研究表明:①近15年来,巢湖流域的土地利用结构变化较大,呈现"三减一增"的变化趋势,即林地、农地和水体呈下降趋势,建设用地呈上升趋势,其中,农地面积下降明显,建设用地面积增幅较大;②土地利用程度变化两极分化,弱土地利用程度显著下降,强土地利用程度明显增加。分析表明,2000—2013年的近15年间,弱和较弱土地利用程度的流域面积下降3 429 km~2,占总流域面积24.61%;较强和强土地利用程度的流域面积上升729 km~2,占总流域面积5.23%;③土地利用程度空间异质性分析表明,2000年和2013年巢湖流域土地利用程度全局空间自相关的Moran's I值分别为0.802 2和0.753 9,呈显著的正相关关系,表明巢湖流域土地利用程度不是无序的,而是具有明显的空间集聚性;局部空间自相关分析表明,LISA图显示土地利用程度的高高值区主要集聚在以合肥市区为核心的周围,低低值区主要集聚在以西南部的大别山森林地区和中部巢湖及沿湖周边。     

基于TM影像的升金湖湿地生态安全研究

[目的]分析安徽省升金湖湿地景观格局动态变化过程,建立升金湖湿地生态安全(PSR)模型,并探讨其驱动力,为进一步开展升金湖湿地保护及其恢复研究提供科学依据。[方法]在遥感和GIS技术支持下,用1986,2003,2011年的3期TM影像为基本信息源进行分析。[结果]景观格局变化幅度较大,草地和水域面积减幅较显著;多样性指数呈上升趋势而优势度指数呈下降趋势,破碎化程度加剧,斑块类型呈多样性发展;随着景观破碎化程度增强,斑块数增加,将造成湿地生态系统片断化越严重,也会影响到湿地的调蓄能力,改变整个湿地的水文情势,减弱湿地的生态效益;另外,景观格局变化下的湿地生态安全指数趋于逐年下降状态,湿地生态安全形式处于预警状态,形势不容乐观。[结论]近年来,随着经济的发展,人口数量的增加,围垦等活动的加剧,人类活动对研究区的改造导致了自然湿地面积相对减少,升金湖湿地生态功能不断下降,经济增长和人口增长成为湿地格局变化主要驱动力。