东北三省农作物洪涝时空风险评估

仅考虑空间差异的灾害风险评估已经满足不了灾害风险管理向精细化方向发展的要求,增加时间维度的时空风险评估分析有利于增强风险评估结果,对提升风险管理的准确性与针对性起着重要的作用.以东北三省为研究区,在气象数据、地形数据、农作物灾情数据和种植面积数据的支撑下,以县和月为单位的时空两个维度开展农作物洪涝时空风险评估研究.在方法上,采用反距离权重法(IDW),利用与县行政区最临近的3个气象站点的日降雨数据插值出县级行政区的日降雨数据;利用二元回归建立农作物洪涝受灾率与过程降雨量、县平均高程之间的农作物洪涝脆弱性函数;分县分月提取过程降雨量,构建非参数核密度的信息扩散模型拟合降雨量的概率分布;综合概率分布与脆弱性函数,计算出分县分月的农作物洪涝条件期望受灾率,实现风险时空差异表达.最后,制作出东北三省县级尺度下4至9月的农作物洪涝风险差异图,并对风险时空差异规律进行分析.     

渤海湾可溶性无机氮时空变异状况分析

以渤海湾17个监测点11年来可溶性无机氮(DIN)监测数据为研究对象,采用箱线图,相关分析,Mann-Kendall及样条插值等技术方法,分析渤海湾1996—2006年17个监测点ρ(DIN)的统计学特征、季节差异性和时空变化状况,以及引起ρ(DIN)时空变化的原因.结果表明:各监测时期渤海湾ρ(DIN)大多表现为正偏态分布. 在33个监测时段内,2号,4号和6号监测点所在海区ρ(DIN)最高,说明陆源污染及港口发展对渤海湾ρ(DIN)的贡献不容忽视. 丰水期ρ(DIN)与平水期显著相关,而枯水期ρ(DIN)与丰水期和平水期的相关性不显著. 在时间特征上,ρ(DIN)表现为先增加后平稳而后快速增加的趋势;在空间分布上,ρ(DIN)表现为北高南低,近岸高离岸低的趋势.      

Temporal and geographical variations of mercury and selenium in eggs of Larus michahellis and Larus audouinii from central Mediterranean islands

In this study, we determined mercury and selenium levels in abandoned unhatched eggs of the yellow-legged gull (Larus michahellis) and Audouin’s gull (Larus audouinii) collected during 2004–2005 from the Tuscan archipelago and Sardinia (Italy). The different feeding habits of the two species probably determine the different uptakes of trace elements, as the study shows highly significant differences for selenium and mercury levels as well as shell thickness and Hg:Se molar ratio values. Audouin’s gulls nesting on the coasts of the Tuscan archipelago showed significantly higher selenium levels than did gulls from colonies from the islands around Sardinia. Comparisons with a similar investigation previously conducted in the same area suggested that mercury and selenium concentrations, although in line with reports in the literature, were significantly lower than levels encountered in gulls in the early 1980s. Mercury (mg/kg d.w.) dropped from 8.631 to 5.030 in Audouin’s gulls and from 2.509 to 0.828 in yellow-legged gulls. The regional decline in mercury levels following reduced use of the metal in industry and the probable food depletion effects linked to the overfishing of fish prey of these two gull species are discussed as hypotheses that could explain the decrease in mercury levels found in eggs.     

黄河流域水分亏缺时空格局变化研究

针对黄河流域水资源匮乏日益严重的状况,根据国家气象局整编的1957~2001年(45a)黄河流域93个气象站点气象资料,应用1998年FAO最新推荐的Penman-Monteith法计算潜在蒸散量,研究黄河流域水分变化特点,尤其是水分亏缺时空格局。 同时,应用克里格(Kriging)插值法生成黄河流域区域的水分亏缺分布图。研究结果显示黄河流域水分亏缺的空间分布格局变化十分复杂,受气候、地形和地貌等多种因素影响,具有明显的地域特点。总体上,水分亏缺由北向南逐步递减,流域北部水分亏缺由西北向东南依次递减;流域水分亏缺在年际间的变幅具有增大趋势,在年内也表现出明显的季节变化特点,春季、夏季的亏缺量比较大,而冬季和秋季的亏缺量比较小,且在不同区域之间存在明显差别。     

黄河下游河道萎缩成因分析

基于原型定位观测资料分析，结合河工动床模型试验和数学模型计算，研究了黄河下游河道的萎缩成因，并提出了河道萎缩的含义，以及表征河道萎缩的因素及其判别因子。研究表明，河道萎缩的根本原因是水沙过程变异与河道边界因素共同作用的结果；主河槽过水断面面积变化量、同流量水位变化量、河底平均高程抬升速率和横断面形态等可作为河道萎缩的表征因子。     

Seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi

We present the diurnal and seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi, India. Ambient NH3, NO and NO2 were measured continuously during winter, summer and autumn seasons using NH3- and NOx-analyzer, which operates by chemiluminescence method with a higher estimation e ciency (> 90%) than the chemical trap method (reproducibility 4.7%). Prominent diurnal, day-to-day and seasonal variations of ambient mixing ratio of NH3, NO, NO2 and SO2 were observed during the study period. Seasonal variation with higher mixing ratio in winter was observed for all measured trace gases except NO. Day-night variation of all measured trace gases observed was higher in winter in comparison with summer. Late morning increase in NO2 mixing ratio might be attributed to conversion of NO to NO2 with the interaction of O3.     

不同土地利用分布格局下的岩溶泉水化学变化研究

利用多参数自动记录仪CTDP300对具有不同土地利用分布格局的贵州普定陈旗和灯盏河两个岩溶泉域的降雨量、泉水位、水温、pH值和电导率进行了一个完整水文年的连续监测,并依据化学平衡热力学原理进行计算,得到连续的水的CO2分压(PCO2)和方解石饱和指数(SIc)。结果表明这两个泉的这些水化学指标均呈现出明显的季节变化和暴雨动态变化。然而,两泉水的这些变化具有明显的差异:对于土壤分布较多和水田分布在排泄区的陈旗泉而言,HCO3-和PCO2较高,而pH和SIc值明显低于土壤分布较少且水田分布于补给区的灯盏河泉,且变幅较小。此外在暴雨后,陈旗泉pH升高、PCO2降低,而灯盏河泉pH降低、PCO2升高。这些反映了不同土地利用分布格局对岩溶水化学调节作用的差异。灯盏河泉Ca2+、SO2-4、Mg2+和EC较高主要是其流域中石膏和白云岩含量较多的缘故。这些发现说明,pH、电导率、HCO3-、Ca2+、SO42-、Mg2+、PCO2和SIc等岩溶水化学参数可以作为不同土地利用分布格局和环境变化的重要指标。     

长江上游植被覆盖的时空分异季节变化及其驱动因子研究

以GIMMS/NDVl为基础,结合气候与人类活动数据,研究了1982～2003年间长江上游植被覆盖季节变化的空间分布.结果表明,近22年来,长江上游春季、夏季植被覆盖呈增加趋势,以春季最显著;秋季、冬季植被覆盖呈降低趋势,以秋季降低最显著.春季、夏季降雨与气温的同步增加,致使植被覆盖增加;秋季降雨减少,以及气温的增加导致植被覆盖降低;另外,作物播种面积的增加是春季、夏季植被覆盖增加,秋季、冬季植被覆盖减少的重要原因.春季→夏季→秋季→冬季NDVI增加的区域在窄问上大致呈现低纬度向高纬度转移的趋势.春季、夏季所有植被类型的NDVI均有增加趋势;而秋季所有植被类型的NDVI均降低;冬季植被除针叶林的NDVI略有增长外,其余植被类型的NDVI均降低.     

长春市1998-2008年玉米虚拟水量动态变化研究

长春市玉米种植面积约占全市粮食种植面积的60%。通过对长春市1998-2008年玉米虚拟水量的计算与分析,探讨其时空分异规律,为长春市玉米生产的可持续发展提供科学依据。11年来长春市玉米虚拟水量呈现不断波动趋势,分别在1999年、2004年和2007年出现高峰值,2003年呈现最低值。对比分析1998年、2004年和2008年五县市区玉米虚拟水量的空间分布,1998年五县市区虚拟水量只分为四个等级,没有达到第五等级;2004年农安县达到第五等级,位居首位,榆树市虚拟水量仍然为第三等级,排名第2,德惠市和九台市均由第一等级上升为第二等级,排名第三,市区位于第一等级,排名最末。到2008年,榆树市由第三等级上升到第四等级,九台市由第二等级下降到第一等级,其他各县市区虚拟水量等级没有变化。     

Occurrence and ecotoxicological risk assessment of pesticides in sediments of the Rosetta branch, Nile River, Egypt

This study aimed to (1) monitor the occurrence and spatiotemporal variations of 100 pesticides in sediments collected monthly from July 2018 to June 2019 from sampling sites in El-Rahawy, Sabal, and Tala, along the Rosetta branch of the Nile River, Egypt, and (2) perform an ecological risk assessment for aquatic organisms upon exposure to the detected sediment pesticides based on the risk quotient (RQ) method. Out of the 100 pesticides monitored, 16 pesticides belonging to seven chemical families were detected, and 55% of the sediment samples were contaminated with one or more pesticide residues. The mean concentration (mg/kg dry weight (dw)) and detection frequency (%) of the four most frequently detected pesticides in the sediment samples were as follows: chlorpyrifos (0.18 mg/kg dw and 34%), p,p′-DDE (0.018 mg/kg dw and 30%), cypermethrin (0.03 mg/kg dw and 14%), and deltamethrin (0.026 mg/kg dw and 13%). The spatial distribution exhibited that El-Rahawy had the highest pesticide load (2.86 mg/kg dw) among the studied sites, whereas the temporal variations revealed that the highest total pesticide concentrations were detected in winter season (1.73 mg/kg dw). Meanwhile, 12 pesticides showed high RQs (>1), posing a potential ecological risk to aquatic species that live and feed on such sediments.