Geochemistry of Renuka Lake and wetland sediments,Lesser Himalaya (India): implications for source-area weathering,provenance, and tectonic setting     

Brijraj K. Das  Birgit-Gaye  Parkash Kaur 《Environmental Geology》2008,54(1):147-163

The geochemical investigation of sediments deposited in the Renuka Lake basin and its adjoining wetland has shown variation in the distribution and concentration of major, trace and REEs. The major elements are depleted in the lake in relation to wetland and that of Post Archaean Australian, Shale (PAAS), except for CaO which is strikingly in excess and has a dilution effect on SiO₂ and other oxides and trace elements. The Wetland sediments, on the other hand, are enriched in Al₂O₃, Fe₂O₃, K₂O and TiO₂ and the latter three show a positive correlation with Al₂O₃ in both wetland and lake sediments suggesting their association with phyllosilicates and similar source rocks. The enrichment of Y, Zr, Ni, Th, U and Nb in wetland compared to lake and their similarity with PAAS in the former, suggests more clay fractions in the wetland. A high Zr/Hf ratio in wetland and lake sediments and a positive correlation of Zr with Y and HREE indicate Zr control on HREEs. However, higher Zr/Yb and Zr/Th ratios in wetland compared to lake indicate mineral sorting during the process of lighter particles (clays) being trapped in wetland soil. This is also reflected from negative correlation of Gd_N/Yb_N with Al₂O₃ and a strong positive correlation with SiO₂ in wetland sediments. The wetland in this context has a control on lake sediment chemistry. The chondrite normalized REE patterns are essentially the same for lake as well as wetland sediments but abundance decreases in the former. The similarity of pattern with that of PAAS and negative Eu anomaly indicates a cratonic source of sediments. In a plot of the individual samples, wetland samples cluster while lake samples are separated indicating fractionation of lake sediments. A strong positive correlation of La_N/Yb_N with Al₂O₃ and a positive correlation of Zr-∑LREE and Zr-La_N/Yb_N suggest that LREEs are controlled by both phyllosilicates and zircon. The chemical index of alteration (CIA) indices in lake sediments and in wetland are higher than PAAS indicating moderate chemical weathering in the source area. The petrography, lack of felsic magmatic rock fragments, and negative correlation between Zr-(Gd/Yb)_C indicate sedimentary source rocks for the detritus. This is in conformity with the Lesser Himalayan sedimentary sequence belonging to neo-Proterozoic–Proterozoic age and constituting lake catchment of Renuka. The tectonic delineation and discriminant function plots of lake and wetland sediments indicate their cratonic and/or quartzose sedimentary orogenic terrain source that has been deposited in a passive margin setting.  相似文献   

Policy Drivers of U.S. Wetland Conversion Rates, 1955–2009     

Roger K. Wiebusch 《社会与自然资源》2017,30(1):16-30

While conversion of wetlands to nonagricultural purposes has persisted, the five U.S. national wetland inventory reports spanning 1955–2009 show a large decline in the rate of conversion of wetlands for agriculture, especially from the mid-1970s to the mid-1990s. Through regression and path analysis, this study identifies primary policy and economic drivers of this decline in wetland conversions. The Clean Water Act §404 is strongly and negatively related to conversion rates. Crop prices affect wetland conversions both directly, by influencing returns to investments for conversion, and indirectly, by influencing Conservation and Wetland Reserve Program enrollments as well as the regulatory impact of Swampbuster. Along with the proportion of wetlands remaining, these factors explain 90–94% of the annual variation in total wetland conversions, agricultural conversions, and conversion of forested and emergent wetlands.  相似文献   

榆林市城区湿地资源调查与保护对策     

邓小明  张新兵  王茸仙  黄正 《湿地科学与管理》2017,(1):18-20

在榆林市建成区湿地资源进行全面调查的基础上,分析了湿地资源保护现状及存在的问题,并提出了合理的湿地保护措施和对策。  相似文献   

广西珍珠港红树林湿地保护与恢复对策     

何彬元 《湿地科学与管理》2017,(2):47-49

结合广西珍珠港红树林湿地保护与恢复工程项目的实施,分析了项目实施过程中存在的主要问题,探讨了广西珍珠港红树林湿地保护与恢复对策。  相似文献   

人类活动对长江中游湿地生态系统的冲击   总被引：27，自引：1，他引：26  

蔡述明  周新宇 《地理科学》1996,16(2):129-136

长江中游平原湖区是中国湿地资源的重要组成部分,由于人类对湿地资源的开发利用,给平原湖区带来了“鱼米之乡的”美誉,成为中国重要的农业生产基地和经济发达地带,同时也对生态环境带来了一系列的冲击,湿地资源与环境亟待保护。  相似文献   

湿地生态系统模型研究进展   总被引：17，自引：3，他引：17  

崔保山  杨志峰 《地球科学进展》2001,16(3):352-358

介绍了湿地生态系统模型概念及类型 ,重点分析了河流湿地、沼泽及河漫滩湿地、湿地退化模型。在河流湿地中 ,重点讨论了水文水动力学模型、泥沙冲淤模型、河流水质模型 ;在沼泽及河漫滩湿地中 ,阐述了水量模型、生物量模型、P模型和 N模型 ;最后在分析湿地退化的数学模型基础上 ,探讨了湿地大型植物的控制模型。  相似文献   

Monitoring the recovery of a previously exploited surf-zone fish community in the St Lucia Marine Reserve,South Africa,using a no-take sanctuary area as a benchmark     

BQ Mann  H Winker  JQ Maggs  SN Porter 《African Journal of Marine Science》2016,38(3):423-441

Limiting accessibility to a fishing area can reduce fishing effort effectively and may therefore promote local recovery of depleted stocks. In January 2002, beach driving was banned in South Africa, thereby reducing angler access to large areas of the coastline, particularly in less-developed areas. In November 2001 a project had been established in the St Lucia Marine Reserve, on the east coast of South Africa, to compare surf-zone fish populations inside a no-take sanctuary zone with those in an adjacent exploited area. Subsequent to the ban, the aim of the project was adapted such that surf-zone fish populations were monitored for potential recovery in what had been the exploited area, located to the north of Cape Vidal, which anglers could no longer access easily, because of the prohibition on beach driving. Standardised research fishing was conducted at two sites in the previously exploited area and two sites in the no-take sanctuary. Conventional stock-status indicators showed evidence of recovery in the four most common species caught in the previously exploited area, in terms of both abundance and biomass. Generalised additive mixed models were used to account for the influence of targeting specific species; however, subtle differences in habitat between the sampling sites, improved angling skill over time, variability in recruitment, and differential species-specific responses complicated interpretation of results. The implications of the findings are discussed in terms of the future monitoring and management of marine protected areas both within the St Lucia Marine Reserve and farther afield.  相似文献   

饮马河流域典型湿地植物净化河流水环境效果研究   总被引：1，自引：0，他引：1  

李廷超  王咏  张刚  王肇钧 《湿地科学与管理》2016,(2):41-45

采取单种及混种方式,通过小型湿地模拟实验,研究松花江支流饮马河流域河流湿地中常见的芦苇、香蒲、槽秆荸荠、藨草、慈姑、花蔺、菱角、紫背浮萍和金鱼藻9种湿地植物及其组合对河流水体中化学需氧量(COD_(cr))、氮、磷等的净化效果。结果表明:所选湿地植物,在模拟环境条件下均能有效提升取自河流水体的水质;不同的湿地植物对污水中各污染物净化具有明显的差异,花蔺对总磷(TP)、COD_(cr)和氨氮(NH_3-N)净化效果最好,去除率依次为99.65%、68.22%和99.54%;香蒲、菱角、金鱼藻混合组对总氮(TN)的净化效果最好,去除率是66.19%;槽杆荸荠、芦苇和金鱼藻对亚硝酸盐氮(NO_2-N)的净化效果最好,去除率是83.64%。两种植物混种后对某一种污染物指标的处理效果弱于分别独种时的处理效果,但对多种污染物指标的综合处理效果一般要好于独种时的处理效果。  相似文献   

傅疃河流域综合治理与湿地恢复保护研究     

郭建和  安丰敬  秦兰香  申延鹏  张平  李永强 《湿地科学与管理》2016,(3):32-34

积极采取封山育林、退耕还林还湿,规划建设省级湿地公园,加大流域内污染企业的治理,引导居民改变生活习惯,采取生物技术建设人工浮岛等多种措施,对傅疃河流域进行综合治理,实现流域内湿地生态系统的恢复和保护。  相似文献   

甘肃黑河中游湿地保护利用现状及对策初探   总被引：1，自引：0，他引：1  

付宗斌  韩涛  梁光明  王钰婷 《湿地科学与管理》2016,(3):40-42

在对甘肃黑河中游湿地保护利用现状进行全面分析评价的基础上,针对湿地保护利用中存在的问题,提出了保护恢复黑河中游湿地及可持续开发利用的对策。  相似文献