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根据杭州市40个土壤全铅和38个可溶相铅的统计分析,土壤中全铅平均含量为49.6×10-6,可溶相铅平均为21.4×10-6,城区表土的全铅高达76.1×10-6,显著高于全国土壤平均值。分析结果还显示,从农村→远郊→近郊→公路旁,土壤可溶相铅含量逐渐增加,且土壤的可溶相铅含量与深度具明显的负相关关系。表明杭州市土壤受到了不同程度的铅污染,污染程度由农村→远郊→近郊→公路旁→城区有明显的增高趋势。通过对茶园土壤中可溶相铅、残渣态铅及城区表土全铅的同位素组成对比分析发现,从土壤残渣态(代表土壤背景)→土壤可溶相→城区表层土壤全铅206Pb/207Pb比值有明显的降低。208Pb/(206Pb+207Pb)也有类似的变化趋势。将土壤与杭州市的汽车尾气、大气等环境样品进行对比发现,随着土壤受污染程度的增加,铅同位素组成逐渐向汽车尾气铅漂移,表明汽车尾气排放的铅为其主要污染源。 相似文献
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在第四纪的末次冰期、新冰期和小冰期期间,位于大峡谷入口处的则隆弄跃动冰川发生多次的快速前进,多次发生阻塞雅鲁藏布江事件,在大峡谷以上河段形成4期(Ⅳ~Ⅰ)的林芝古堰塞湖。14 C测年结果指示第2次、第3次和第4次堰塞湖分别发生在9760~11300aB.P.,1220±40~1660±40aB.P.和287±93~394±83aB.P.。估计Ⅳ~Ⅱ期堰塞湖库容量约2150km3,835km3和81km3。冰川阻塞湖坝的溃决释放突发性洪水,对下游的雅鲁藏布大峡谷河段及下游地区的环境产生巨大的影响。 相似文献
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国土空间开发适宜性评价是国土空间规划编制的重要基础,市县是落实主体功能区划的基本单元,市县级国土空间开发适宜性评价可为国土资源与空间更精细化的管理提供有效支撑。本研究从自然因素和社会经济因素两个方面构建了国土空间开发适宜性评价指标体系,对宜昌市农业生产适宜性及城镇建设适宜性进行了评价,划分出适宜、较适宜、一般适宜、较不适宜和不适宜5类区域。结果表明宜昌市适宜开展农业生产的土地面积为3412 km2,不适宜土地面积为7143 km2;适宜进行城镇建设的土地面积为748 km2,不适宜土地面积为14679 km2。农业生产和城镇建设适宜性评价结果均呈现出典型的区域特征,适宜区主要分布在东部的平原区,区域整体的国土空间开发条件好;不适宜区主要分布在西部山区,区域整体的国土空间开发难度大。适宜性评价结果与规划数据有部分出入,与土地利用现状相差不大,农业生产适宜等级的土地面积比耕地保有量红线面积多132 km2,分布于农业生产适宜和较适宜区的现状耕地占耕地总面积的73.98%;城镇建设适宜等级的土地面积比建设用地底线面积少611 km2,分布于城镇建设适宜和较适宜区的现状建设用地占建设用地总面积的77.99%。将评价结果叠加在谷歌卫星图上,在空间上观察是否与土地现状一致,结果表明农业生产适宜区的评价结果准确率达100%,不适宜区的准确率为93%;城镇建设适宜区和不适宜区评价结果准确率达100%。 相似文献
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本文根据类似荒漠境况的出现是判断荒漠化发生与否的重要标志这一原则,并结合在中国南方开展的一些研究,对湿润地区的荒漠化进行了初步的探讨。研究表明,湿润地区的荒漠化并不包含所有存在侵蚀作用的退化土地,而专指人为侵蚀作用导致的出现了具类似荒漠境况的退化土地。中国南方湿润地区土地荒漠化分布最显著的特征为斑点状分布于丘陵山区或河、湖、海滨的冲积平原,面积为1．98×105km2,其中流水作用导致的荒漠化面积为1．78×105km2,风力作用的为0．11×105km2,其它0．09×105km2。自然因素,特别是气候和地貌因素对荒漠化的形成和发展起着积极的影响作用,但不是决定作用。人为不合理的经济活动,才是造成荒漠化的主要原因。文章最后还简要介绍了湿润地区荒漠化的防治问题。 相似文献
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为了响应国际地球化学旗图计划(ICCP259)中的全球地球化学采样子计划的实施,研制超低密度地球化学采样的最佳方法,1989～1990年在江西省开展了一项试点研究.在约15.7万平方公里的可采面积内采集了121件河漫滩沉积物样品.平均采样密度约为五个点/1300km2.采样覆盖度为24%.采样点主要布置在100-500km2的汇水盆地口上,其中有33个采样点控制的汇水盆地面积在400～2000km2之间.河漫滩沉积物样品来自深度在0.5m以下到1.2m的柱状剖面.样品定量分析了38种元素.文章从多方面讨论了超低密度河漫滩沉积物地球化学术样的代表性,并得出以下主要结论:1.在400-2000km2的汇水盆地口上采集河漫滩沉积物样品能较好地反映上游汇水盆地中的主要矿化.2.超低密度采样和以2个点/km2采集水系沉积物样品所获得的W、Sn、Cu、Pb和Zn五个元素的地球化学趋势相似.3.超低密度样品中W、Ph、Be、Rb等元素的分布特征与省内花岗岩的分布相吻合.4.超低密来样品中“3Ni+Cr+V”的分布能较好地反映扬子准地台与华南加里东精皱系在省内的分界线. 相似文献
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土地荒漠化是当前的一个重大生态环境问题。我国土地荒漠化的发展速度十分惊人,在60年代每年为1600km2,到90年代中期达2460km2。吉林省西部平原的面积为47000km2,半个世f己以来已有1／4的草地和耕地荒漠化,土地完全丧失了生产能力。粗略估计,近30年吉林西部耕地碱化速率为2．64％／a,沙化速率为066％／a;草地碱化速率为2．47％／a,沙化速率为0.83％／a。若任其发展,50年后将有二分之一的土地沦为荒漠,百年之后大部分土地将变为荒漠。土地荒漠化的形成与古气候、古地理环境密切相关,但更重要的是受到当代人类活动的影响,随着人口的不断增长,人类对土地资源掠夺性的开发,加速了土 相似文献
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滑坡危险性评价是减灾防灾的重要措施之一。通过野外调查,陕西省清涧县城区周边斜坡地带共发育滑坡138处,严重威胁县城安全。为了准确评价清涧县城区滑坡危险性,按照河流沟谷的发育情况和地形地貌的完整性,将清涧县城区及周边区域的斜坡地带共划分为925个斜坡单元,将斜坡单元按照不同的坡度、坡高和坡型分别进行不同土体含水率工况下的斜坡稳定性计算。计算结果表明,随着斜坡土体含水率的逐渐增加,城区内稳定斜坡的面积逐渐减少,不稳定斜坡的面积逐渐增大。依据陕北地区黄土斜坡土体含水率监测数据,分析计算土体含水率（w）的出现概率,w≤0.15出现的概率为0.622（概率很高）,0.15<w≤0.2出现的概率为0.2963（概率高）,0.2<w≤0.25出现的概率为0.0816（概率中）,w>0.25出现的概率为0（概率低）。结合斜坡稳定性计算结果和含水率出现概率,评价斜坡单元危险性。评价结果表明,清涧县城区危险性很高区面积3.27 km2,包含斜坡单元112个,已发生滑坡点92个;危险性高区面积4.19 km2,包含斜坡单元128个,已发生滑坡点36个;危险性中区面积8.75 km2,包含斜坡单元251个,已发生滑坡点6个;危险性低区面积15.20 km2,包含斜坡单元434个,已发生滑坡点4个。 相似文献
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对直流电阻率法异常产生干扰的地电体有地形、接触面和浮土等。浮土也可称为地表电性不均匀体[1]。我们对地形改正方法[2]直立接触面量板[3]作过研究后,应用电阻网络模拟机和电子计算机,研究了浮土的视电阻率异常。 相似文献
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青藏高原冻土退化的研究 总被引：21，自引：2，他引：21
青藏高原从70年代后期气温持续转暖,导致高原多年冻土呈区域性退化趋势。年平均地温升高0.1～0.5℃,在边缘地带垂向上形成不衔接冻土和融化夹层,多年冻土分布下界上升40～80 m,高原多年冻土总面积约减少10×104km2。 相似文献
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The coastal zone of the Sagar island has been studied. The island has been subjected to erosion by natural processes and to
a little extent by anthropogenic activities over a long period. Major landforms identified in the coastal area of the Sagar
island are the mud flats/salt marshes, sandy beaches/dunes and mangroves. The foreshore sediments are characterized by silty,
slightly sandy mud, slightly silty sand and silty sand. Samples 500 m inland from high waterline are silty slightly sandy
mud, and by clayey slightly sandy mud. The extent of coastline changes are made by comparing the topographic maps of 1967
and satellite imageries of 1996, 1998 and 1999. Between 1967 and 1999 about 29.8 km2 of the island has been eroded and the accreted area is only 6.03 km2. Between 1996 and 1998 the area underwent erosion of 13.64 km2 while accretion was 0.48 km2. From 1998 to 1999, 3.26 km2 additional area was eroded with meager accretion. Erosion from 1997 to 1999 was estimated at 0.74 km2 /year; however, from 1996 to 1999, the erosion rate was calculated as 5.47 km2/year. The areas severely affected by erosion are the northeastern, southwestern and southeastern faces of the island. As
a consequence of coastal erosion, the mud flats/salt marshes, sandy beaches/dunes and mangroves have been eroded considerably.
Deposition is experienced mainly on the western and southern part of the island. The island is built primarily by silt and
clay, which can more easily be eroded by the waves, tides and cyclonic activities than a sandy coast. Historic sea level rises
accompanied by land subsidence lead to differing rates of erosion at several pockets, thus periodically establishing new erosion
planes. 相似文献
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青藏高原东部长江流域盆地陆地化学风化研究 总被引：4，自引：0，他引：4
长江河水主要离子由流域盆地碳酸盐岩的风化所控制,沱沱河和楚玛尔河受蒸发盐岩影响较为明显;河水溶质载荷Si,Si/TZ *,Si/(Na* K)等指标表明,长江流域盆地地表硅酸盐岩风化还是浅表层次的;金沙江地表化学剥蚀速率为1.74×103mol/yr.km2,雅砻江为1.69×103mol/yr.km2,大渡河为1.57×103mol/yr.km2,岷江为1.88×103mol/yr.km2,长江河源区楚玛尔河为2.32×103mol/yr.km2,沱沱河为1.37×103mol/yr.km2,流域地表化学剥蚀速率可与世界上其它造山带的河流进行对比。 相似文献
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Estimation of areas of sand and dust emission in the Hexi Corridor from a land cover database: an approach that combines remote sensing with GIS 总被引：1，自引：0，他引：1
The present study combined remote sensing with geographical information system (GIS) technology to interpret Landsat TM images
from 1996 to 2000 and establish a land cover database for the Hexi Corridor of China’s Gansu Province. The areas of sand and
dust emission and trends in their change were extracted by analyzing the database, with the following results: In 2000, the
source area for sand and dust storms totaled nearly 170,000 km2, accounting for 75.1% of the study region. The emission area decreases from as much as 70,000 km2 in winter and spring to around 58,000 km2 in summer and autumn, accounting for 41.1 and 34.1% of the source area, respectively. During the 4 years of the study period,
the emission area decreased by nearly 57 km2 in winter and spring (a 0.1% change); however, the vulnerability of the land surface to wind erosion increased in ca. 190 km2 and decreased in ca. 102 km2. Although the area of dust emission decreased from 1996 to 2000, the area vulnerable to wind erosion increased by ca. 87 km2, and the increased number of sand and dust storm days in the region between 2000 and 2003 appears to be correlated with this
increase. 相似文献
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Monitoring the spatiotemporal changes in wetlands and assessing their causal factors is critical for developing robust strategies for the conservation and restoration of these ecologically important ecosystems. In this study, the spatiotemporal changes in the land cover system within a Himalayan wetland and its catchment were assessed and correlated using a time series of satellite, historical, and field data. Significant changes in the spatial extent, water depth, and the land system of the Hokersar wetland were observed from the spatiotemporal analysis of the data from 1969 to 2008. The wetland area has shrunk from 18.75 km2 in 1969 to 13 km2 in 2008 with drastic reduction in the water depth of the wetland. The marshy lands, habitat of the migratory birds, have shrunk from 16.3 km2 in 1969 to 5.62 km2 in 2008 and have been colonized by various other land cover types. The land system and water extent changes within the wetland were related to the spatiotemporal changes in the land cover and hydrometeorological variables at the catchment scale. Significant changes in the forest cover (88.33–55.78 km2), settlement (4.63–15.35 km2), and water bodies (1.75–0.51 km2) were observed in the catchment. It is concluded that the urbanization, deforestation, changes in the hydrologic and climatic conditions, and other land system changes observed in the catchment are the main causes responsible for the depleting wetland extent, water depth, and biodiversity by adversely influencing the hydrologic erosion and other land surface processes in the catchment. All these causes and effects are manifest in the form of deterioration of the water quality, water quantity, the biodiversity changes, and the decreasing migratory bird population in the wetland. 相似文献
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陕甘宁接壤区气候暖干化及其生态环境意义 总被引：9，自引：0，他引：9
应用陕甘宁接壤区1951-2000年气温、降水及1956-2000年陕甘宁接壤区 7条主要河流径流量实测记录,在实地调研的基础上对气象数据和水文数据分析后得出结论,陕甘宁接壤区近年来气候呈现暖干化趋势,全区增温线性倾向值为 0．194℃／10 a,高于全球近百年的趋势（0．05℃／10 a）,区内增温趋势强弱差异显著。陕甘宁接壤区气候变干表现在 2个方面：①年降水量减少;②地表径流量减少。降水线性倾向值平均为－1．0759 mm／a,地表径流总量1956-2000年减少速率为 0．4844 m3／a。陕甘宁接壤区生态环境在暖干化的气候背景下继续恶化,生态贫水化严重,水土流失加剧,沙漠扩大。 相似文献
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《China Geology》2021,4(2):353-363
The environmental change in the wetlands in the southern Mongolian Plateau has important impacts on the environment of North China and even the entire Northeast Asia, from which the global climate change can be understood on a large scale, especially the climate change in the Mongolian Plateau. This study extracted the information on the wetlands from three stages of remote sensing images (also referred to as RS images) of the study area, including Enhanced Thematic Mapper Plus (ETM+) images of 2000, TM images of 2010, and Landsat 8 Operational Land Imager (OLI) images of 2018. As indicated by the extraction results, the area of wetlands decreased from 796.90 km2 of 2000 to 666.24 km2 of 2018 at a rate of 7.26 km2/a. The reduced area is 130.66 km2, which is about 16.4% reduction. And the patch number of wetlands decreased from 731 of 2000 to 316 of 2018 in the study area, approximately 56.8% reduction (415 patches), and the decrease in the area of the wetlands mainly occurred in the northwest endorheic region. In terms of wetland types, the change of the wetlands was dominated by the decrease of lacustrine wetlands, of which the area and patch number decreased by 106.2 km2 and 242, respectively. Furthermore, the area of the lacustrine wetlands decreased at the highest rate of 8.70 km2/a in 2010–2018. From the perspective of spatial distribution, the wetlands in the western part shrunk more notably than those in the eastern part as a whole in the study area. According to local meteorological data, the precipitation gently decreased and the temperature increased (about 1.7°C) from 1975–2018. Overall, the decrease in the area of the wetlands and the temperature rises in the study area were mainly driven by the Mongolian monsoon climate, reduction in precipitation, and human activities. 相似文献
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Coastal Wetlands of China: Changes from the 1970s to 2007 Based on a New Wetland Classification System 总被引：1，自引：0，他引：1
A new classification of coastal wetlands along the coast of China has been generated that is compatible with the Ramsar Convention of 1971. The coastal wetlands have been divided into two broad categories with overall nine subcategories. On this basis, a series of coastal wetland maps, together covering the coast of mainland China, have been produced based on topographic maps acquired in the 1970s and satellite images acquired in 2007. These document substantial wetland losses over this period. In the 1970s, the total coastal wetland area in China was 5.76?×?104?km2, whereas in 2007, it was 5.36?×?104?km2, indicating a loss of 7 %. Over this approximately 40-year period, the area of natural coastal wetlands decreased from 5.74?×?104 to 5.09?×?104?km2, while that of artificial coastal wetlands increased from 240 to 2,740 km2. Due to shoreline and sea-level changes, newly formed coastal wetlands amounted to 2,460 km2, while coastal wetland loss amounted to 6,310 km2 in the period from the 1970s to 2007. When excluding shallow coastal waters (depths between 0 and ?5 m), nearly 16 % of Chinese coastal wetlands have been lost between the 1970s and 2007. 相似文献
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Batsuren Dorjsuren Denghua Yan Hao Wang Sonomdagva Chonokhuu Altanbold Enkhbold Davaadorj Davaasuren Abel Girma Asaminew Abiyu Lanshu Jing Mohammed Gedefaw 《Environmental Earth Sciences》2018,77(20):725
Land cover and vegetation in Lake Baikal basin (LBB) are considered to be highly susceptible to climate change. However, there is less information on the change trends in both climate and land cover in LBB and thus less understanding of the watershed sensitivity and adaptability to climate change. Here we identified the spatial and temporal patterns of changes in climate (from 1979 to 2016), land cover, and vegetation (from 2000 to 2010) in the LBB. During the past 40 years, there was a little increase in precipitation while air temperature has increased by 1.4 °C. During the past 10 years, land cover has changed significantly. Herein grassland, water bodies, permanent snow, and ice decreased by 485.40 km2, 161.55 km2 and 2.83 km2, respectively. However, forest and wetland increased by 111.40 km2 and 202.90 km2, respectively. About 83.67 km2 area of water bodies has been converted into the wetland. Also, there was a significant change in Normalized Difference Vegetation Index (NDVI), the NDVI maximum value was 1 in 2000, decreased to 0.9 in 2010. Evidently, it was in the mountainous areas and in the river basin that the vegetation shifted. Our findings have implications for predicting the safety of water resources and water eco-environment in LBB under global change. 相似文献