Rural vulnerability to environmental change in the irrigated lowlands of Central Asia and options for policy-makers: A review

Climate change, land degradation and drought affect millions of people living in drylands worldwide. With its food security depending almost entirely on irrigated agriculture, Central Asia is one of the arid regions highly vulnerable to water scarcity. Previous research of land and water use in the region has focused on improving water-use efficiency, soil management and identifying technical, institutional and agricultural innovations. However, vulnerability to climate change has rarely been considered, in spite of the imminent risks due to a higher-than-average warming perspective and the predicted melting of glaciers, which will greatly affect the availability of irrigation water. Using the Khorezm region in the irrigated lowlands of northwest Uzbekistan as an example, we identify the local patterns of vulnerability to climate variability and extremes. We look at on-going environmental degradation, water-use inefficiency, and barriers to climate change adaptation and mitigation, and based on an extensive review of research evidence from the region, we present concrete examples of initiatives for building resilience and improving climate risk management. These include improving water use efficiency and changing the cropping patterns that have a high potential to decrease the exposure and sensitivity of rural communities to climate risks. In addition, changes in land use such as the afforestation of degraded croplands, and introducing resource-smart cultivation practices such as conservation agriculture, may strengthen the capacity of farmers and institutions to respond to climate challenges. As these can be out-scaled to similar environments, i.e. the irrigated cotton and wheat growing lowland regions in Central Asia and the Caucasus, these findings may be relevant for regions beyond the immediate geographic area from which it draws its examples.     

太湖流域农村生活污水处理技术探讨

2010年江苏省太湖流域主要污染物排放情况显示,太湖流域内的农村生活污水、农田径流和养殖污水是导致太湖水体富营养化的主要污染源。目前,在中国针对农村生活污水的处理技术已有一定研究。根据太湖流域农村生活污水的特点,人工湿地处理技术和稳定塘系统等新型污水处理技术具有良好的应用前景。     

依托北槽、建设长江口亚三角洲体系——关于长江流域开发龙头新基地的战略构想

当前正处于向长江口发展的最好时机。随着长江口深水航道整治工程的开展，长江口水流复杂、河势易变的局面正在改变，加之长江口越江通道的建成通车，在长江口外形成超深水泊位及超深水航道的条件已渐趋成熟。利用长江口外-15 m以深的天然水深建设海上人工岛，就可达到-20 m以深的航道水深，打造河口深水大港，使之成为长江流域水水中转、海陆联运的桥头堡；而整治、疏浚工程所产生的大量泥沙，又为促使横沙东滩及其邻近沙洲加快成陆创造了条件。通过疏浚、促淤、造陆的三位一体，预计可在未来20 a间长江口南港与北港之间、北槽主航道两侧形成500多km²的河口岛群，发育塑造成为长江河口的亚三角洲体系.     

Dynamic modeling of chemical fate and transport in multimedia environments at watershed scale-II: trichloroethylene test case

A multimedia environmental fate model was developed to study the temporal dynamics and spatial distribution of a chemical pollutant at watershed scale. The theoretical considerations and implementation of the model were described in the accompanying paper (Part I). This paper presents the result of a test simulation on the transport of trichloroethylene (TCE) in the Connecticut River Basin. The simulation results were reported as time series of concentrations and inter-media transport fluxes in the compartments of atmosphere, plant, soil, surface water, and sediment. Predicted concentrations from the test simulation were compared with published field data or predictions by validated models. The temporal trends in TCE predictions were evaluated by comparing the simulation results with monthly TCE concentrations in various environmental compartments and monthly fluxes of inter-media transport processes. Results indicated that the simulation results were in reasonable agreement with reported data in the literature. The results also revealed that the mass transport of TCE from the atmosphere compartment to soil and surface water was a major route of TCE dispersion in the environment.     

Dams,Floodplain Land Use,and Riparian Forest Conservation in the Semiarid Upper Colorado River Basin,USA

Land and water resource development can independently eliminate riparian plant communities, including Fremont cottonwood forest (CF), a major contributor to ecosystem structure and functioning in semiarid portions of the American Southwest. We tested whether floodplain development was linked to river regulation in the Upper Colorado River Basin (UCRB) by relating the extent of five developed land-cover categories as well as CF and other natural vegetation to catchment reservoir capacity, changes in total annual and annual peak discharge, and overall level of mainstem hydrologic alteration (small, moderate, or large) in 26 fourth-order subbasins. We also asked whether CF appeared to be in jeopardy at a regional level. We classified 51% of the 57,000 ha of alluvial floodplain examined along >2600 km of mainstem rivers as CF and 36% as developed. The proportion developed was unrelated to the level of mainstem hydrologic alteration. The proportion classified as CF was also independent of the level of hydrologic alteration, a result we attribute to confounding effects from development, the presence of time lags, and contrasting effects from flow alteration in different subbasins. Most CF (68% by area) had a sparse canopy (50% canopy cover occupied <1% of the floodplain in 15 subbasins. We suggest that CF extent in the UCRB will decline markedly in the future, when the old trees on floodplains now disconnected from the river die and large areas change from CF to non-CF categories. Attention at a basinwide scale to the multiple factors affecting cottonwood patch dynamics is needed to assure conservation of these riparian forests.     

北运河流域植被覆盖度变化及其生态环境质量评估

北运河流域作为北京城市副中心建设涉及的重要自然地理单元,流域内人类活动剧烈,生态问题突出,植被覆盖率下降.基于植被覆盖度快速实现流域内生态环境质量的全面评价,是打造生态和谐宜居示范区的重要支撑,也是实现新时期首都生态文明建设的关键.本文选取1990年、2004年、2018年时相相近的3期Landsat TM/OLI数据,首先采用线性光谱混合模型进行植被覆盖度(FVC)的计算,再利用主成分分析法构建遥感生态指数(RSEI),并对二者时空变化规律及相关性进行探究.结果表明,1990—2018年,研究区平均植被覆盖度与遥感生态指数均呈现先增后减的趋势,植被覆盖度由0.36增长至0.43再降至0.41,遥感生态指数由0.545增加为0.584后又降至0.545.1990—2004年生态质量下降的区域集中分布在北京市主城区四周,环境质量改善的区域集中分布在北运河流域北部、中心城区及东南部,而2004—2018年生态质量下降的重点区域则向东南部流域下游转移,环境质量改善的区域则大面积减少.流域内生态质量保持稳定的区域大幅增加,生态质量差与较差区域占比连续降低,表明研究区大部分区域生态系统状况趋于稳...     

基于长期观测的淮河流域农田背景区灰霾污染气溶胶光学特性和类型分析

利用2015—2019年寿县国家气候观象台的CE-318型太阳光度计观测数据,比较分析了淮河流域农田背景区及其灰霾污染日、非灰霾污染日的气溶胶光学特性和类型的差异和联系.结果表明：①淮河流域农田背景区及其灰霾污染日、非灰霾污染日的AOD₄₄₀平均值为0.60~0.86,以细粒子气溶胶为主,气溶胶散射能力强,吸收能力弱;②细粒子气溶胶增加在淮河流域农田背景区灰霾污染中占主导作用,灰霾污染发生时,AOD₄₄₀平均值增大0.26,散射能力增强,吸收能力减弱,污染的气溶胶类型占比增加17.79%;③2015—2019年,淮河流域农田背景区及其灰霾污染日、非灰霾污染日的气溶胶光学厚度、细模态粒子体积浓度整体呈减小趋势,气溶胶散射能力逐年增强,吸收能力逐年减弱;④淮河流域农田背景区及其灰霾污染日,随着污染等级的增加,气溶胶光学厚度和污染的气溶胶类型占比增大,重度污染时颗粒物向大粒径方向移动,但仍为细粒子;⑤受气溶胶来源、吸湿增长和高温的影响,春夏季气溶胶光学厚度和单次散射反照率较高,秋冬季主要由雾霾污染造成,细粒子比例高,气溶胶光学厚度和单次散射反照率较低.     

黄河流域绿色创新效率空间格局演化及其影响因素

绿色创新作为培育经济增长新动能,是促进黄河流域生态保护和高质量发展的重要动力。采用网络DEA模型测度2003—2018年黄河流域79市（州、盟）绿色创新效率,进而运用核密度估计、重心—标准差椭圆分析效率的空间演化规律,采用空间计量模型探究其影响因素。结果表明：（1）黄河流域绿色创新效率水平较低,但表现为波动上升的时间趋势;（2）绿色创新效率具有显著的空间非均衡性,呈现出“下游>上游>中游”的空间分异格局,效率重心整体向东南方向移动,表现出南北方向相对稳定、东西方向集聚发展的趋势;（3）黄河流域绿色创新效率存在正向的空间溢出效应,人均收入、产业结构、师资力量、外资利用和环境规制是影响绿色创新效率的重要因素。     

南亚高压对四川盆地夏季区域持续性O3污染的影响

基于2015~2020年四川盆地臭氧（O₃）浓度监测数据,构建O₃区域性持续性污染过程个例库,并进一步时空匹配高低空气象资料,探究夏季南亚高压系统对四川盆地地面气象要素及O₃污染生成的影响机制.结果表明：（1）2015~2018年四川盆地O₃区域性持续性污染（ORPP）逐年加重,2018~2020年保持相对稳定的污染态势,且ORPP多集中于春、夏两季.盆地中南部成都、重庆、泸州等城市O₃污染形势最为严峻,且高值区逐渐向南北方向转移.（2）基于南亚高压（系统存在率、中心离散度与东西振荡量）对地面气象要素的影响阐释ORPP的生成机制：系统存在率均值偏低且位置偏东时,平均气温、气温日较差及日照时数偏高,相对湿度偏低,利于O₃生成;南亚高压东模态中心显著聚集时,气温日较差与日照时数激增,易造成O₃异常高值;西模态剧烈振荡时,气温日较差、日照时数及相对湿度改变,易使O₃浓度波动.（3）对比清洁期与污染期,南亚高压系统存在率、中心离散度与东西振荡量综合作用于清洁期,而污染期则主要受中心离散度与东西振荡量影响.当南亚高压西模态剧烈振荡与东模态显著聚集配合出现时,极易诱发四川盆地内ORPP二级过程.     

赣江源头流域植被变化的水文响应模拟研究

应用2个分布式水文模型（SWAT和Topmodel模型），对赣江流域的源头——梅江流域20年内的植被变化所造成的生态水文响应做出了模拟研究。根据2个模型不同的特点，设计了不同的模拟方案，使用SWAT模型模拟径流量的变化，Topmodel模型模拟汇流过程的变化。模拟得到的结果是：排除研究时间段内流域气候变化的影响，仅变换流域下垫面的属性，植被的变化对流域水文特征产生了明显影响，在整个梅江流域的范围内，2000年的年径流总量比1987年增加了146%；在其子流域——琴江流域，1995~2000年的7次洪峰峰值径流出现时间比1987年延迟，峰值径流量减少约5%。这说明从上世纪80年代开始在该流域内进行的植树造林和国土整治工作,即江西省“山江湖工程”，对流域的生态健康具有良好的回馈效应。