EXTREMELY HEAVY FLOODS AND THEIR CONTROL IN THE TAIHU LAKE REGION

Based on fieldd investigations and relevant literature, this paper expounds on the cause of the extremely heavy floods in the Taihu Lake region in 1991, compares the flood-hit areas of 1954 with those of 1991, summarizes the experience on flood control and presents some useful proposals.     

西溪湿地土壤重金属分布特征及其生态风险评价

测试和研究了杭州西溪湿地土壤中铜(Cu)、锌(Zn)、铅(Pb)、镉(Cd)、汞(Hg)、砷(As)和铬(Cr)的含量与分布特征,采用内梅罗综合污染指数和Hakanson潜在生态危害指数法对湿地土壤重金属污染环境质量和潜在生态风险进行了评价。结果表明,西溪湿地土壤表层7种重金属平均含量的质量比分别为36.8 mg/kg(Cu)、91.5 mg/kg(Zn)、39.2 mg/kg(Pb)、0.23 mg/kg(Cd)、0.19 mg/kg(Hg)、6.3 mg/kg(As)和64.9 mg/kg(Cr)。由于受各种人为作用的影响,与浙江省土壤背景值相比,Cu、Pb、Cd和Zn在湿地土壤中的积累较大,有3个采样点[菜地、芦苇(Phram ites austrlis)滩地和靠马路的居民区]土壤中的Cd含量超过《土壤环境质量标准》(GB15618-1995)标准值的二级标准(pH<6.5)。湿地土壤重金属污染环境质量和生态风险评价结果显示,内梅罗综合污染指数平均值为1.73,多种重金属潜在生态风险指数平均值为114.6,说明总体上西溪湿地土壤重金属污染及其潜在生态风险为轻微级。最后,讨论了西溪湿地公园土壤重金属的可能来源,对比了重金属污染评价中不同评价标准和评价方法的差异性。     

2011年7月陕西一次区域性暴雨过程分析

为了探索陕西区域性暴雨发生发展的机制,提高暴雨预报准确率,利用实况高空观测、自动站观测资料和NCEP1°×1°格点资料,采用天气学诊断方法,对2011年7月28日陕西区域性暴雨过程进行分析。结果表明:500hPa西风槽、西太平洋副热带高压、700hPa及其以下的切变是这次暴雨的主要影响系统,低层大风速带和南海台风的远距离作用是暴雨增幅的重要因子;暴雨区具有强的能量锋和对流不稳定,降水产生在850hPa温湿能等值线密集区偏高值一侧;水汽主要来源于孟加拉湾和南海台风外围;辐合、辐散中心下移是强降水即将发生的一个信号,850hPa以下出现比湿猛增现象对位于秦岭以北的渭河流域暴雨预报有一定指导意义。     

SOIL QUALITY IN ILLINOIS—AN EXAMPLE OF A SOILS GEOGRAPHY RESOURCE ANALYSIS∗

Although acts of creation, scientific or artistic, result from metaphorical and mythological speculations, the role of metaphor and myth has largely been neglected in attempts to develop a geographical epistemology. The significance of these concepts is illustrated by the use of the frontier symbol as a means of understanding both the social structure of the contemporary black inner city and the temporal dimension of the recent expansion of human activities into nighttime.     

典型矿业城市的土壤重金属分布特征与复合污染评价——以“镍都”金昌市为例

通过对甘肃省金昌市(镍矿城市)建成区的土壤重金属调查研究,揭示了其重金属来源、污染现状及其环境风险。结果表明:当地主要矿产品Ni和Cu两种重金属的土壤污染最严重,与《土壤环境质量标准》(GB15618-1995)的III级标准比较,样品Ni和Cu的超标率分别为70%和57%,污染面积分别为26 km2和24 km2;土壤As和Cd污染主要集中在矿冶区和尾砂库附近,居民区土壤污染程度低;土壤Cr污染出现在尾砂库和采矿区附近,污染面积为3 km2。在城区土壤中,Co、Cu、Cd、Pb与Zn的污染来源及空间分布具有相似特征,而土壤As污染与Ni污染特征相近。Nemero综合指数评价结果表明,高风险区域主要分布在东部矿冶区、北部尾砂库和西南角采矿区,城市居民区的土壤重金属污染水平较低。     

利用黏土矿物计算背景值评估沉积物重金属污染

综合考虑样品性质及粒度的影响,提出利用黏土矿物计算背景值的方法。实例研究表明,研究区沉积剖面不同深度样品的背景值存在一定的差异。将实测值与背景值之比视为富集因子,发现As、Cr、Cu在剖面的中下部弱富集;Pb在剖面中部弱富集;Zn与Cd在剖面的不同位置的富集程度变化较大,在中部显著富集,表层及底部中度富集。与传统方法相比,该方法综合考虑了粒度和样品性质的影响,并且可以计算出不同位置样品的背景值,使得评估结果更加准确。     

强暴雨系统中湿位涡异常的诊断分析

2012年和2013年夏季有两个高原低涡向东北方向移出青藏高原,随后在西北地区引发暴雨天气,其中2013年的高原低涡移动路径更加偏东,其暴雨强度更强、落区偏东且范围更广。基于ERA-Interim再分析资料和台站降水资料,对比分析两次高原低涡移动过程中的大尺度环流以及低涡对强降水的影响,并结合湿位涡进行诊断分析。结果表明：500 hPa河套高压脊与200 hPa西风急流对高原低涡的移动存在显著影响,两者位置及强度的差异是造成两次高原低涡移出位置不同的主要原因。低涡高（低）层辐散（辐合）结构有利于垂直运动的发展,为暴雨提供了有利的动力条件。低涡的低层辐合有利于水汽向暴雨区输送。正压湿位涡诊断结果表明2013年低涡过程暴雨区有更强的不稳定条件;斜压湿位涡诊断表明2013年低涡过程有来自西太平洋的暖湿气流向暴雨中心输送。

     

东亚梅雨系统的天气-气候学研究

利用NCEP/NCAR逐日再分析资料、上海观测站降水资料,对上海2020年超强梅雨特征及成因进行了分析,并对基于大气低频特征的延伸期预报效果进行了评估。结果表明：（1）2020年上海梅雨量为2000年以来最多。（2）受夏季赤道中东太平洋冷水位相和热带印度洋海温异常偏暖的影响,西北太平洋异常反气旋强盛且稳定少动,其西侧转向的水汽输送偏强加之中高纬地区Rossby波列的传播引起中低层天气系统（槽、脊等）的变化,引发冷空气活动,也对副高的北抬起到了抑制作用,造成梅雨期偏长,雨量偏多。（3）2020年梅雨期降水过程表现出明显的准双周振荡特征,4次强降水过程均对应低频降水的峰值。沿Rossby波低频活动通量方向移动的低频波列南下,并与低频反气旋对峙于长江流域,导致多轮强降水。基于大气低频特征研发的延伸期预报方法较为准确地预报出2020年上海入梅首场强降水过程。

     

Heavy metal concentrations of agricultural soils and vegetables from Dongguan, Guangdong

A total of 118 of agricultural soil and 43 of vegetable samples were collected from Dongguan City, Guangdong, China. The spatial distribution, sources, accumulation characteristics and potential risk of heavy metals in the agricultural soils and vegetables were depicted in details by three different approaches, including total contents of eight metal elements in soils and vegetables, GIS maps and multivariate analysis of heavy metals in soils in the study. The results show that there are higher accumulation of heavy metals such as Cu, Zn, Ni, Pb, Cd and Hg in agricultural soils, and the contents of Pb (65.38 mg kg?1) and Hg (0.24 mg kg?1) are 1.82 and 2.82 times of the background contents of the corresponding heavy metals in soils of Guangdong Province, respectively. There are about 3.4% of Cu, 5.9% of Ni, 1.7% of Cd and 28% of Hg in all collected soil samples from all investigated sites which have overran the contents for heavy metals of the China Environmental Quality Standard for Soils (GB15618-1995, Grade Ⅱ). The pollution characteristics of multi-metals in soils are mainly reflected by Hg. There are different sources to eight metal elements in soils, Cu, Zn, Ni, Cr and As are predominantly derived from parent materials, and Pb, Hg and Cd are affected by anthropogenic activities. The spatial distribution shows that the Cu, Zn, Ni, Cr, Pb, As and Hg contents of agricultural soils are high in the west and low in the east, and Cd contents are high in the northwest, southeast and low in the southwest in Dongguan. The ratios of vegetable samples which Ni, Pb and As concentrations higher than the Maximum Levels of Contaminants in Foods (GB2762-2005) are 4.7%, 16.3% and 48.8%, respectively. The order of bio-concentration factors (BCF) of heavy metals in vegetables is Cd > Zn > Cu > As > Ni > Hg > Cr > Pb. It is necessary to focus on potential risk of heavy metals for food safety and human’s health from agricultural soils and vegetables in Dongguan City, Guangdong Province.