State and potential management to improve water quality in an agricultural catchment relative to a natural baseline

Land use change and the expansion of dairying are perceived as the cause of poor water quality in the 1881 km² Pomahaka catchment in Otago, New Zealand. A study was conducted to determine the long-term trend at four sites, and current state in 13 sub-catchments, of water quality. Drains in 2 dairy-farmed sub-catchments were also sampled to determine their potential as a point source of stream contamination. Data highlighted an overall increase in the concentration of phosphorus (P) fractions at long-term sites. Loads of contaminants (nitrogen (N) and P fractions, sediment and Escherichia coli) were greatest in those sub-catchments with the most dairying. Baseline (without human influence) contaminant concentrations suggested that there was considerable scope for decreasing losses. At most sites, baseline concentrations were <20% of current median concentrations. Contaminant losses via drainage were recorded despite there being no rainfall that day and attributed to applying too much effluent onto wet soil. Modelling of P concentrations in one dairy-farmed sub-catchment suggested that up to 58% of P losses came from point sources, like bad effluent practice and stock access to streams. A statistical test to detect “contaminated” drainage was developed from historical data. If this test had been applied to remove contaminated drainage from samples of the two dairy-farmed sub-catchments, median contaminant concentrations and loads would have decreased by up to 58% (greater decreases were found for E. coli, ammoniacal-N and total P than other contaminants). This suggests that better uptake of strategies to mitigate contamination, such as deferred effluent irrigation (and low rate application), could decrease drainage losses from dairy-farmed land and thereby improve water quality in the Pomahaka catchment.     

纳板河保护区生态旅游资源分析与评价

在总结调查资料的基础上,以西双版纳纳板河流域国家级自然保护区的生态旅游资源为研究对象,对其进行分类并评价,以期为今后保护区旅游开发提供科学依据。     

基于GIS的滇池流域景观格局优化

景观格局优化是景观生态学中的难点和热点问题。选择滇池流域为研究区域,在RS和GIS的支持下对2008年Landsat TM影像进行解译判读,获得景观类型图,运用最小耗费距离模型对区域景观格局进行优化。结合景观各组分生态系统服务功能价值和空间作用,构建了生态源地、生态廊道和生态节点等景观组分,以加强生态网络的空间连通性,提高景观格局稳定性,完善生态功能。源地具有较高的生态系统服务功能,需要维持和增大源斑块面积。所构建城市区域廊道、森林生态廊道、农业生产廊道应采取保持廊道规模,建立缓冲区,加强植被绿化,减少污染物的排放等措施以提高整个廊道的连通性。节点位于景观生态流和连通的重要位置上,需要加强控制。该研究对流域生态规划和土地利用优化布局有一定的参考价值。     

近50a玛纳斯河流域土地利用/覆被变化对碳储量的影响

土地利用变化对碳收支的影响是当前全球变化研究领域的重点内容之一,中国西北干旱区土地利用变化对陆地生态系统碳收支的影响尚不清楚。论文以西北干旱区流域绿洲水土开发的典范--玛纳斯河流域为研究区,基于Bookkeeping模型,利用多期土地覆被类型图、植被和土壤碳密度历史文献及实地调查资料,开展玛纳斯河流域近50 a荒漠转变为绿洲农田和农田弃耕两种主要土地覆被变化对碳收支的影响研究。玛纳斯河流域的垦殖活动有利于碳储量的增加,在1962-2008年的46 a间,土地利用变化导致流域植被碳储量增加6.34×10⁵ t,土壤碳储量增加3.14×10⁶ t,总碳储量增加3.77×10⁶ t。受土地覆被变化面积和转换类型碳密度差异的影响,不同土地覆被类型转换对碳储量的影响存在显著差异:荒漠草地、裸地开垦为耕地均引起植被和土壤碳储量显著增加;林地开垦为耕地引起植被碳储量减少,土壤碳储量增加,总碳储量减少;而耕地弃耕通常会导致流域碳储量减少。     

太湖流域城市化水平及外来人口影响测评

太湖流域属于我国东部沿海经济较发达的地区,2000年城市化水平达到66.17%,接近全国平均水平的两倍。自改革开放以来,该地区工业化发展迅速,由以乡镇企业为主过渡到外资和民营企业的大力发展,吸引了来自全国各地的就业迁移人口,成为全国流动人口的主要集中区。同时使得外来人口成为地区社会经济发展规划不可忽视的重要因素。以第五次人口普查资料为基础分析了太湖流域外来人口来源的地域和城乡构成,计算了外来人口数量及分布情况,指出外来人口的城乡非均衡分布促成地区城镇化率的小幅上升,太湖流域各地区的上升幅度在2%左右,部分解释了隐性城镇化率的产生。在城市市区,外来人口平均占到总城市人口的18%。对于50万人口以上城市,外来人口比重与城市规模表现出良好的相关性,可用于指导城市人口规模及地区城镇化水平预测。     

渭河和泾河流域浅层地下水水化学特征和控制因素

渭河和泾河流域是黄河流域的重要支流,了解这两个流域地下水的水质状况对于黄河流域生态保护和高质量发展具有重要意义.本文利用Piper图、Gibbs模型、Na端元图和离子相关关系等方法,解释了两流域地下水水化学组成特征及其控制因素的特征与差异.并利用WQI法、Wilcox图、USSL图和Doneen图等方法,评估研究区地下水水质的饮用和灌溉适宜性.结果表明,渭河和泾河流域浅层地下水均以淡水为主,呈弱碱性;除Na⁺外,渭河流域地下水离子浓度整体上均大于泾河流域;两流域优势阴阳离子均为HCO₃^-和Na⁺;渭河流域水化学类型以HCO₃-Ca-Mg为主,占50%,而泾河流域以HCO₃-Ca-Mg和HCO₃-Na-K为主,各占32.5%.渭河和泾河流域水化学组成均主要受岩石风化作用控制,其中又以硅酸盐岩石风化为主;其次,研究区地下水水化学组成受到工矿活动的影响,且农业活动中化肥的施用也是其重要的控制因素;此外,渭河流域的浅层地下水水化学特征受到了明显的阳离子交替吸附作用的影响,而泾河流域有些地区却并不明显.对于饮用水水质评价而言,两流域地下水水质整体较好,且泾河流域地下水整体上优于渭河流域;根据SSP、SAR和PI指标对地下水作为灌溉水水质评价表明,研究区部分地区地下水不能直接进行灌溉,否则会造成盐害进而引起抑制植物生长,南部的水质优于北部;此外,3种灌溉水质评判方法均表明泾河流域地下水作为灌溉水水质整体上优于渭河流域.本研究能对渭河和泾河流域地下水水资源可持续利用、科学开发治理提供依据,并为黄土高原主要流域和其他类似地区水质管理及评价提供借鉴.     

Urbanization reduces resource use efficiency of phytoplankton community by altering the environment and decreasing biodiversity

Urbanization often exerts multiple effects on aquatic and terrestrial organisms, including changes in biodiversity, species composition and ecosystem functions. However, the impacts of urbanization on river phytoplankton in subtropical urbanizing watersheds remain largely unknown. Here, we explored the effects of urbanization on phytoplankton community structure（i.e., biomass, community composition and diversity） and function（i.e., resource use efficiency） in a subtropical river at watershed sca...     

江西仙女湖流域大型底栖动物群落结构及水质评价

以典型的亚热带大型山地丘陵湖泊——江西省仙女湖研究为例,2014~2015年每月对仙女湖湖区及主要入湖河流进行了大型底栖动物群落的周年动态研究。经鉴定得底栖动物111种,隶属3门53科77属。其中软体动物40种,节肢动物61种,环节动物10种。优势种为中华颤蚓、梨形环棱螺、河蚬、锯齿新米虾、羽摇蚊、粗腹摇蚊属、前突摇蚊属、霍甫水丝蚓。仙女湖大型底栖动物年平息栖息密度为346 ind./m2,年平均生物量为54.26 g/m2;不同区域和季节底栖动物的栖息密度与生物量有显著差异(P0.05),河流型生境R2年平均栖息密度最大,为722 ind./m2。湖泊型生境L4年平均栖息密度最小,为251 ind./m2。1月的平均栖息密度最高,为567 ind./m2,5月平均栖息密度最低,为163 ind./m2。用辛普森多样性指数对不同区域水质进行评价,结果表明,入湖河流和钤阳湖为轻度污染,舞龙湖为中度污染。系统聚类和MDS排序分析表明,大型底栖动物的分布具有环境空间异质性,可以划分为2个群落。     

Optimal water quality monitoring network design for river systems

Typical tasks of a river monitoring network design include the selection of the water quality parameters, selection of sampling and measurement methods for these parameters, identification of the locations of sampling stations and determination of the sampling frequencies. These primary design considerations may require a variety of objectives, constraints and solutions. In this study we focus on the optimal river water quality monitoring network design aspect of the overall monitoring program and propose a novel methodology for the analysis of this problem. In the proposed analysis, the locations of sampling sites are determined such that the contaminant detection time is minimized for the river network while achieving maximum reliability for the monitoring system performance. Altamaha river system in the State of Georgia, USA is chosen as an example to demonstrate the proposed methodology. The results show that the proposed model can be effectively used for the optimal design of monitoring networks in river systems.