排序方式： 共有57条查询结果，搜索用时 31 毫秒
41.
我国历史时期的湖泊围垦与湖泊退缩 总被引：1，自引：0，他引：1
方金琪 《云南地理环境研究》1989,1(1):71-78
根据历史资料记载,我国历史时期的湖泊围垦可分为三个时期,即魏晋——南北朝、南宋和明末清初。近乎90％的古湖泊消失于这些时期。大多数学者认为,人口增长导致湖泊围垦、退缩。本文进一步的研究表明,湖泊田垦时期与气候干旱期、黄河和长江的低水位期相吻合:与此同时,湖泊也处于低水位期。 相似文献
42.
Aeolian desertification from the mid-1970s to 2005 in Otindag Sandy Land, Northern China 总被引：1，自引：0，他引：1
Aeolian desertification in Otindag Sandy Land has expanded dramatically during the past 50 years. This research explored processes
and causes of aeolian desertification in the study area. The results showed that aeolian desertification development in Zhenglan
Qi of typical region located at the center in the study area can be divided into three stages including rapid occurrence before
1987, parts of rehabilitation and most of deterioration from 1987 to 2000 and little rapid rehabilitation occurrence from
2000 to 2005, according to remote sensing images and field investigations. Gradually declining MI indicated that climate change
was not the major cause of aeolian desertification development during the last 40 years, while increasing population should
be the underlying cause of local aeolian desertification. Irrational human activities mainly including unsuitable reclamation
in the 1960s and lasting over-grazing after 1980 are direct causes contributing to local aeolian desertification, especially
over-grazing, while climate change often played a revealer of irrational human activities mainly through drought events. Over-grazing
and undesirable climate have different functions during the whole aeolian desertification process. Over-grazing gradually
changed grasslands to slight aeolian desertified lands at the initial stage, while climate with windy days or droughts often
accelerated formation of serious aeolian desertified lands. Aeolian desertification in the study area both possesses occurrence
possibility and great rehabilitative potential. At present, more integrated countermeasures combating local aeolian desertification
still are expected. 相似文献
43.
围垦对长江口横沙东滩大型底栖动物群落的影响 总被引：2，自引：0，他引：2
于2011年4—12月,采用生态学的方法,选择了长江口横沙东滩成陆区、促淤区和自然潮滩三种生境,研究了围垦对其大型底栖动物的影响。结果显示,在横沙东滩共发现大型底栖动物28种,物种分布为自然潮滩(22种)>促淤区(19种)>成陆区(7种),优势种为自然潮滩(6种)>促淤区(5种)>成陆区(2种)。大型底栖动物的年均丰度为促淤区(118.68ind/m2)>成陆区(100.67ind/m2)>自然潮滩(57.56ind/m2),而年均生物量为促淤区(35.71g/m2)>自然潮滩(27.56g/m2)>成陆区(1.52g/m2),三种生境大型底栖动物的丰度和生物量与其种类组成有关。大型底栖动物的多样性指数(H′、J、d)为自然潮滩>促淤区>成陆区。群落聚类和MDS分析显示横沙东滩三种生境的底栖动物群落之间存在较明显差异,同时ABC曲线也证实了成陆区和促淤区的底栖动物群落有明显变化,而自然潮滩的群落结构相对完整。以上结果表明,围垦导致横沙东滩大型底栖动物群落结构发生了明显改变。 相似文献
44.
Biogeochemical Characterizations and Reclamation Strategies of Saline Sodic Soil in Northeastern China 总被引：3，自引：0，他引：3
Soil salinity and sodicity is considered one of the most import impediments to agricultural development in Northeast China. The contents of TP and TK decrease with soil depth and high coefficients of variation were found in TOC, AN, and AP. Mean EC in the 0–50 cm soil layers ranged from 0.61 to 0.89 dS m?1 and the average soluble ion concentrations in the topsoil (0–10 cm) were approximately 11.38 mmol L?1 for Na+, 1.21 mmol L?1 for Ca2+, and 0.40 mmol L?1 for Mg2+. High SAR existed in the layers 10–50 cm, indicating the studied soil was bearing low salinity in the top layer and high sodic layer in the subsurface. The soil presented strong alkali reactions all through the profile with pH over 9.5. To improve and utilize saline sodic soil rationally, several strategies were put forward based on long‐term field studies and demonstration works. The results implied that ameliorating with sand, applying farm yard manure, regenerating salt tolerant grasses and leaching with groundwater, and growing rice were effective measures for improving physical and chemical qualities of saline sodic soil. 相似文献
45.
南京市幕府山地区矿区环境地质整治恢复建议 总被引：1，自引：0，他引：1
列举幕府山地区基岩山区因采矿活动带来的主要环境地质问题及对其处理的意义,提出了环境地质整治与恢复的建议。 相似文献
46.
J.T.K. Chan H.M. Leung P.Y.K. Yue C.K. Au Y.K. Wong K.C. Cheung W.C. Li K.K.L. Yung 《Marine pollution bulletin》2017,114(1):587-591
The up-to-date concentration of polycyclic aromatic hydrocarbons (PAHs) in sediment materials of Victoria Harbour was investigated so as to evaluate the pollution potential associated with the reclamation projects in Hong Kong. A total of 100 sediment samples were collected at 20 locations. Except the control point in reservoir, the PAHs concentrations were detectable levels all sites (131–628.3 ng/g, dw) and such values were higher than Dutch Target and Intervention Values (the New Dutch standard in 2016). The PAHs concentration indicating that construction waste and wastewater discharges were the main pollutant sources. Results of correlation in single cell gel electrophoresis assay (comet assay) studies also revealed that the PAHs concentration was highly correlated (< 0.01) with DNA migration (i.e. the length of tail moment of fish cells) in 5 mg/ml of PAHs. The above observation indicates that the PAHs present in the sediment may substantially effect the marine ecosystem. Although the dredged sediment can be a useful sea-filling material for land reclamation; however, the continuing leaching of PAHs and its impact on the aquatic environment need to be studied further. 相似文献
47.
48.
为加强对围填海开发的管理,提高围填海利用率及经济效益,基于遥感影像、统计资料与第一次全国海洋经济调查数据,文章对1990—2015年以来河北省围填海规模发展状况、产业开发特征以及围填海经济效益进行研究。结果显示,1990年以来河北省累计围填海总面积达6.21万hm2,以港口、工业和城镇建设围填海为主,围填区实体项目所涉产业主要包括农林牧渔业、交通运输与仓储业、制造业。围填海未利用面积占比达53.14%,其中计划用于制造业的围填海未利用面积较大。2015年河北省围填区域生产总值达296.23亿元,对全省GDP的贡献率达0.99%,但单位面积经济效益低于邻近省、市。分析认为,河北省围填海未利用率高、经济效益较低的主要因素包括腹地支撑程度不高、基础设施不完善、产业形势低迷及港口竞争优势不足等。当前河北省应重点从区域协同发展、区域规划、基础设施建设、优惠政策等方面加强围填海开发管理,不断优化围填海开发格局,带动沿海社会经济的发展。 相似文献
49.
填海空间作为连接陆地与海洋的重要部分,是陆海统筹发展的关键一环。文章以深圳为例,通过整理1980—2020年深圳市域的Landsat遥感影像,对填海规模及海岸线变化进行分析,结合发展背景将深圳填海历程分为4个阶段：试点发展下的临港企业自主建设(1980—1986年)、政企分离中的地方产业基建铺开(1986—1996年)、资源短缺下的政府双重角色强化(1996—2010年)和存量优化中的填海多元利益考量(2010—2020年)。最终填海总面积达91.68 km2,自然岸线保有率下降49.92%,且持续多年的填海对海岸带生态安全状况造成了负面影响。基于此,文章指出政府作为利益导向政策主体对其自身及企业和公众关于填海的行为观念产生了重要影响,最终推动了填海发展符合城市社会整体利益。最后,以深圳填海空间演变过程为鉴,其他沿海城市的空间发展应关注历史填海项目的生态修复与利益补偿和新增填海项目的经济与生态利益权衡。 相似文献
50.
针对填海造地巨大的工程影响和极其缺乏平面设计准则的现实需要,引入海洋生态约束的核心价值判断标准和环境流体动力学模型,通过对不同填海造地平面设计方案的海洋环境扰动能力模拟,评判填海造地平面设计准则和方法。在具体模拟过程中,按照填海造地平面设计的要素分为形态类要素、间距类要素、组合方式类要素3大类别5个模拟组19种工况,依次对比模拟了不同工况在水动力学特征(流场和流速)和水体交换能力上的影响差异。进而通过评判工况优劣,分析不同规划要素条件变量对海洋环境的影响,从而总结了5组工况下的相关填海造地区域平面设计在形态类要素、间距类要素、组合方式类要素方面的准则。 相似文献