Differences in risks and consequences of salmon louse, Lepeophtheirus salmonis (Kroyer), infestation on sympatric populations of Atlantic salmon, brown trout, and Arctic charr within northern fjords     

Bjorn  P. A.; Finstad  B.; Kristoffersen  R.; McKinley  R. S.; Rikardsen  A. H. 《ICES Journal of Marine Science》2007,64(2):386-393

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Sedimentary record of redox-sensitive elements (U, Mn, Mo) in a transitory anoxic basin (the Thau lagoon, France)   总被引：4，自引：0，他引：4  

Franoise Elbaz-Poulichet  Jean Luc Seidel  Didier Jzquel  Edouard Metzger  Franois Prvot  Caroline Simonucci  Grard Sarazin  Eric Viollier  Henri Etcheber  Jean-Marie Jouanneau  Olivier Weber  Olivier Radakovitch 《Marine Chemistry》2005,95(3-4):271-281

In order to further document the relation between redox conditions and the sedimentary record of Mn, U and Mo in a transitory anoxic water basin, their distribution has been studied along two profiles in the Thau lagoon (France). Sediments and pore-water have been sampled at two contrasting sites located, respectively, in the shellfish-farming area and in the centre of the lagoon. In the shellfish-farming area, the particulate organic carbon (POC) data indicate a more rapid organic matter mineralisation compared to the centre of the lagoon. This results in a sharper redox gradient characterized by the appearance of H₂S in pore-water a few millimetres below the sediment–water interface. In the centre of the lagoon, H₂S appears at a depth of 35 cm.In both cores, sedimentary Mn is relatively depleted through out the whole sedimentary column and varies with the proportion of clay minerals. After an initial release into solution at the sediment–water interface in relation to Mn-oxide reductive dissolution, authigenic U is immobilized when sulphides appear. Despite the occurrence of anoxic conditions at the sediment–water interface at the site influenced by shellfish farming, the burial of U is reduced by bioturbation, which raises reducing sediments to the surface. In the centre of the lagoon, Mo profiles reflect continuous diffusion into pore water and immobilization at 15 cm probably in anoxic microenvironments. At shellfish farms, dissolved Mo undergoes removal with sulphides but contrary to U, sedimentary Mo does not appear to be strongly affected by bioturbation. The profile indicates an increase in the frequency of anoxia crises during the second half of the 20th century.  相似文献   

甘肃某生活垃圾填埋场地下水污染特征及污染途径分析          下载免费PDF全文

宁天祥  韩雪 《甘肃地质》2023,(2):56-63

依据实际调查数据,采用单因子污染指数分析法确定了生活垃圾填埋场地下水中主要污染物、污染程度和污染范围,并进行了土壤和地下水污染耦合性分析,研究结果表明：该生活垃圾填埋场地下水污染物主要为氨氮、总氮、高锰酸盐、锰、挥发酚和氟化物,其污染指数最大值分别为1 407.24、745.00、137.12、97.50、3.60和1.68,污染区总面积0.168 km²;填埋场下游沟谷纵向上,总氮、锰两项指标在土壤中的含量与地下水中浓度变化趋势一致;其污染途径主要为库区防渗层破损,渗滤液垂向沿基岩风化裂隙进入地下含水层,以连续渗漏的方式不断污染地下水,污染物在地下水径流作用下向拦挡坝下游不断迁移。  相似文献   

城乡土地利用中的传统文化保护     

许庆福  许梦  吴汉涛 《山东国土资源》2015,31(7)

传统文化是物质生活和精神生活的历史积淀,是一个民族共有精神家园,而土地则是传统文化的重要物质载体。随着经济社会的快速发展,一些优秀的传统文化也伴随着城乡土地利用变化而随之消失。在建设社会主义文化强国的背景下,城乡土地利用应结合现代农业发展,注重农耕文化的传承;结合新农村建设,强化对传统村落的保护;结合城市更新,加强对传统街区、历史建筑的保护。  相似文献   

居民家庭日常出行碳排放的发生机制与调控策略——以北京市为例   总被引：3，自引：0，他引：3  

柴彦威  肖作鹏  刘志林 《地理研究》2012,31(2):334-344

根据2007年北京市居民活动日志调查数据,利用Amos7.0软件建立单效标因素的路径分析模型,试图在"社区-家庭"层面上挖掘"空间利用-出行特征-碳排放"的内在发生机理,藉此寻找城市空间组织低碳化的调控路径。研究发现:影响居民家庭日常出行碳排放的主要因素是出行距离和出行方式。社区空间利用特征对家庭出行的距离总量有显著影响,对小汽车出行比率则没有明显作用效果;私家车的购置对居民家庭出行行为的高碳化具有不可逆的作用特点;在现有设施条件、空间环境和车辆使用政策下,公共交通对私人交通出行没有替代性。研究认为,城市空间组织和调控优化应通过土地混合利用、设施供给等物质空间组织与再组织手段,形成空间行为组织和行为规划策略,引导居民降低交通发生量,优化居民交通发生的时空结构,建构低碳的城市空间结构。  相似文献   

Water scarcity problems in Israel     

Amnon Kartin 《GeoJournal》2001,53(3):273-282

The demand for scarce fresh water requires Israel to cease squandering this limited resource on agriculture, at present consuming about 70% of the annual supply. Environmental pollution must cease as well, for untreated urban water effluent contaminates ground water. All Israel's 700 million cubic metres sewage water must be suitably purified to irrigate about one hundred thousand hectares. Climatically controlled greenhouses and advanced agricultural research will reduce the amount of water and land required for the cultivation of the fresh vegetables and fruit, and small proportion of the dry fodder needed for the country's consumption. Israeli agriculture's association with moral, ideological and social ideas obstructs meaningful reduction in the allocation of water to agriculture. The Zionist movement has always seen transforming land into a means of production as the index of its success. Failure in this would signify an inability to adapt to adverse environmental conditions and be a sweeping repudiation of Zionism. The protracted Israeli-Arab national conflict also affects water policy. Israeli Jewish society has always considered rural settlement, agricultural activity, as part of the substance of its national identity and power, bonding the people with the land and consolidating territorial sovereignty. Since the 1970s, capitalism, which has dominated Israeli ideology, has favoured the individual's interests over the community's. Thus agriculture is mobilized to accommodate the private struggle for the good of the farming sector against the needs of the national collective.  相似文献   

西藏高原农户的投资行为——以达孜县为例   总被引：7，自引：0，他引：7  

王慎强  刘伟 《山地学报》2001,19(3):243-247

根据农户调查资料和有关的统计数据对西藏达孜县农户的投资行为进行了研究。结果表明：该县农户的投资主要以直接投资为主，间接投资所占的比重较低；在直接投资中，又以家庭经营投资和固定资产投资为主；农户对科技教育、文化娱乐方面的投资较少，而对宗教信仰方面的投资相对较多；其投资资金来源主要是自有资金。其次是银行贷款和其他资金，国家财政拨款所占的比重不大；受投资结构等因素的影响，该县农户的投资效益基本上呈农年降低趋势。  相似文献   

三峡库区坡耕地退耕与粮食安全的空间分异   总被引：9，自引：3，他引：9  

冯仁国  王黎明  杨燕风  欧阳宏斌 《山地学报》2001,19(4):306-311

坡耕地退耕还林还草作为生态环境建设的一项重要措施，已在全国逐步开展。坡耕地退耕使耕地数量减少，并影响到退耕地区粮食产量减少，尤其在坡耕地分布集中、交通不便地区的尤为突出。本文利用GIS技术对三峡库区坡耕地空间分布进行了分析，探讨了三峡库区坡耕地退耕后粮食安全隐患产生的原因，初步揭示了粮食供需矛盾的空间差异，并结合交通便利状况，划分粮食安全区、警戒区，危机区等三种不同类型的区域。  相似文献   

Gender,Work, and Household Survival in South Indian Fishing Communities: A Preliminary Analysis     

Holly M. Hapke 《The Professional geographer》2001,53(3):313-331

This article examines the interplay of gender, caste‐religion, and household survival strategy formation among Christian and Muslim fisher folk in the south Indian state of Kerala. The methodology consisted of surveys of forty‐one households in two villages in which data pertaining to male and female work patterns and other household level data were collected in the summer of 1999. My analysis demonstrates how particular ideologies of gender and work associated with different caste‐religion communities influence the strategies individual households adopt. I discuss intersections between gender and caste‐religion with other socioeconomic factors and illustrate the manner in which gender then gets reworked in particular ways in the course of economic transformation.  相似文献   

Agricultural performance on marginal land in Eastern Inner Mongolia,China – Development in the pre- and post-1978 reform periods     

Sara Brogaard  Xiubin Li 《GeoJournal》2005,64(3):163-175

Rapid economic development in the aftermath of the Chinese post-1978 reforms has resulted in a shrinking of grain grown area in the southern and eastern regions of the country which in turn is believed to have put the marginal northern regions under increased pressure. This paper examines key indicators of agricultural performance as well as cultivated land area development of the pre- and post-1978 reform periods focusing on the agro-pastoral Tongliao City Prefecture, eastern Inner Mongolia. The results are related to the village level development through a case study as well as to the provincial level. Average annual grain per capita production increased from about 400 kg in the late 1970s to more then 1000 kg in the late 1990s. This was achieved through a combination of intensification and reclamation of cropland, with the latter restricted to pastoral classified counties. Production variability, in particular for the low producing counties, has also increased possibly as an effect of the substitution of traditional mixed pattern of crops with HYV monocultures. Average living standards have improved but have been accompanied by widening income gaps. Poor farmers’ livelihoods continue to be insecure, particularly during dry years. Concern is raised regarding the sustainability of the rapid agricultural development; an increased use of costly fertilisers constrains poorer farmer’s economy and may lead to deteriorating water quality while increasing irrigation depletes water resources.  相似文献