Air Pollution Potential: Regional Study in Argentina

/ Air pollution potential is a measure of the atmospheric conditions that are unable to transport and dilute pollutants into the air, independently of the existence of sources. This potential can be determined from two atmospheric parameters: mixing height and transport wind. In this paper a statistical analysis of the mixing height and transport wind, in order to determine the areas with high or poor atmospheric ventilation in Argentina, is presented. In order to achieve this, meteorological data registered during 1979-1982 at eight meteorological stations were used. Daily values of the maximum mixing height were calculated from observations of daily temperatures at different heights and maximum surface temperature. At the same time as the maximum mixing height, the values of the transport wind were determined from the surface windspeed and the characteristics of the ground in the surroundings of each meteorological station. The mean seasonal values for both parameters were obtained. Isopleths of the mean seasonal of the maximum mixing heights were drawn. The percentage of seasonal frequencies of poor ventilation conditions were calculated and the frequency isopleths were also drawn to determine areas with minor and major relative frequencies. It was found that the northeastern and central-eastern regions of Argentina had a high air pollution potential during the whole year. Unfavorable atmospheric ventilation conditions were also found in the central-western side of the country during the cold seasons (37.5% in autumn and 56.9% in winter). The region with the greatest atmospheric ventilation is located south of 40 degrees S, where the frequency of poor ventilation varies between 8.0% in summer and 10.8% in winter.     

Modelling impacts of alternative farming management practices on greenhouse gas emissions from a winter wheat–maize rotation system in China

Agricultural production plays an important role in affecting atmospheric greenhouse gas concentrations. Field measurements were conducted in Quzhou County, Hebei Province in the North China Plains to quantify carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions from a winter wheat–maize rotation field, a common cropping system across the Chinese agricultural regions. The observed flux data in conjunction with the local climate, soil and management information were utilized to test a process-based model, Denitrification–Decomposition or DNDC, for its applicability for the cropping system. The validated DNDC was then used for predicting impacts of three management alternatives (i.e., no-till, increased crop residue incorporation and reduced fertilizer application rate) on CO₂ and N₂O emissions from the target field. Results from the simulations indicated that (1) CO₂ emissions were significantly affected by temperature, initial SOC, tillage method, and quantity and quality of the organic matter added in the soils; (2) increases in temperature, initial SOC, total fertilizer N input, and manure amendment substantially increased N₂O emissions; and (3) temperature, initial SOC, tillage, and quantity and quality of the organic matter added in the soil all had significant effects on global warming. Finally, five 50-year scenarios were simulated with DNDC to predict their long-term impacts on crop yield, soil C dynamics, nitrate leaching losses, and N₂O emissions. The modelled results suggested that implementation of manure amendment or crop residue incorporation instead of increased fertilizer application rates would more efficiently mitigate GHG emissions from the tested agro-ecosystem. The multi-impacts provided a sound basis for comprehensive assessments on the management alternatives.     

再生水水质环境中典型水华藻的生长特性

基于微藻的生长潜力试验,研究了再生水回用于景观水体时的水华风险.结果表明,在天然混合藻种接种体系中,铜绿微囊藻(Microcystis aeruginosa)在再生水水质条件下的生长潜力大于其他受试藻种,其在3种二级出水(A2O、氧化沟和活性污泥)中的最大藻密度均可大于106个.mL-1,比生长速率0.39 d-1.A2O-超滤膜过滤-活性炭吸附-氯消毒深度处理工艺没有有效减低铜绿微囊藻的生长潜力,难以减小水华风险.再生水中的TP浓度能够明显影响铜绿微囊藻的最大密度(Kmax)和最大种群增长速率(Rmax),且符合Monod方程.     

基于WOFOST模型的京津冀地区冬小麦生产潜力评价

研究利用近40年的逐日气候数据,借助WOFOST作物模型模拟分析了京津冀地区冬小麦的生产潜力,通过与实际产量的比较,探讨了提高冬小麦产量的潜力与措施。研究表明：①京津冀地区(除张家口和承德地区)冬小麦光温潜力介于6934~9143kg/hm²之间,从冀中南部向京津地区和冀东北地区逐渐增大,区域平均生产潜力为8037kg/hm²;②冬小麦雨养潜力介于4515~6639kg/hm²之间,由东部和南部随降水量降低依次向西北递减,到冀西北区降至最低,区域平均产量为5771kg/hm²;③影响冬小麦产量的自然因子中,水分是关键限制要素,北部地区也受低温霜冻的影响;④京津冀中部和南部地区的冬小麦生产潜力年际变化波动相对较小,东北部变化波动相对较大;⑤2005-2007年研究区冬小麦的实际单产在2721~7300kg/hm²之间,区域平均5247kg/hm²,相当于潜在产量的50%~80%,其中石家庄地区附近实际产量达到潜在产量的80%以上,天津和沧州地区以及邯郸地区,实际产量与潜在产量的差距较大。     

河水-地下水交互带内砷及金属的自然衰减过程

在简单介绍污染物自然衰减作用定义的基础上,重点分析了河水-地下水交互带内As和以矿山废水为来源的金属污染物的自然衰减行为:主要包括吸附作用,氧化还原作用,生物转化作用等。其中详细介绍了金属Fe、Al的氢氧化物/氧化物对As化合物和其他金属如Cd、Cu和Zn等的吸附作用;Ca2+、Fe2+、磷酸盐、重碳酸盐等阴阳离子和天然有机质对吸附作用的影响;金属微生物氧化还原作用以及微生物作用下As(V)与As(III)的相互转化过程。研究发现,阳离子可以增强金属的吸附作用,阴离子主要是参与竞争吸附;天然有机质对金属吸附过程的抑制作用阻碍金属的固定;交互带内氧化还原条件的变化可以引起一系列的氧化还原反应;微生物催化还原不利于As的自然衰减。最后指出目前河水-地下水交互带内金属污染物衰减过程研究存在的问题以及今后的发展方向。     

月亮泡底泥中元素的分布及其生态风险评价

对吉林省西部月亮泡底泥中元素的空间分布、来源以及重金属的潜在生态风险进行了研究。与吉林省中西部土壤中元素平均值相比,月亮泡表层底泥中明显富Hg、Pb、Ca、N,而相对贫As、Co、Mn、Th、Cl、Na。在湖底表层底泥中,As、Hg、U、Cd、Cu、Zn、Cr、Se、Mo、Co、Ni、Mn、N、P、MgO、Fe2O3、CaO、有机碳与Al2O3呈明显的正相关关系,表明它们的地球化学性质与粘土矿物的含量密切相关。表层底泥中Hg、Cd、As、Cr、Cu、Zn、Pb的潜在生态危害性均很小。在月亮泡的两个沉积柱中,元素含量随深度的变化不尽相同。在沉积柱1中,Fe2O3、Mn、P、Zn、Cu、Ni、Co、Cr、Cd等元素含量随深度变化不大,表明其沉积环境较为稳定。在沉积柱2中,元素含量波动较大,表明该沉积柱的沉积环境较为动荡,并在76～80cm和104～108cm处,As、Fe2O3、Mn、P、Cu、Zn、Co、Ni、Cd、Th、U等含量急剧增高;在70～90cm处Mn/Fe比值高,表明当时干旱少雨、沉积环境较为氧化,在104～108cm处Rb/Sr比高,可能反映当时高温多雨、化学风化作用较为强烈。两个沉积柱的Cr/Th比基本相似,表明沉积柱的物源基本相同。沉积柱中重金属的潜在生态危害程度也很小,表明从垂向上进入月亮泡水体的重金属污染物数量也很少。     

深圳河流沉积物中重金属累积特征及污染评价

为了解深圳河流沉积物中重金属的污染现状和污染程度,对1996～2007年深圳河、布吉河、龙岗河和茅洲河4条河流沉积物中重金属元素(Cu、As、Cd、Cr、Hg、Pb和Zn)的含量和年际变化进行了调查和研究,并利用地累积指数和潜在的生态危害指数对其进行了综合评价。结果表明,4条河流均不同程度地受到了重金属的污染,并呈逐年增加的趋势。地累积指数和潜在的生态危害指数的研究显示,4条河流的污染程度大致为:龙岗河布吉河深圳河茅洲河,其中尤以Cu、Cd、Cr和Zn的污染程度最重。龙岗河和布吉河的污染和潜在的生态危害基本上达到了严重的程度,龙岗河多年平均地累积指数高达6.36,潜在的生态危害指数多年平均值为2333.2;而深圳河则大致为中度或者重度污染;茅洲河的污染程度最轻,其潜在的生态危害指数多年均值为274.1,除Cd和Hg处于中度和强度潜在的生态危害外,其余元素大都是轻度污染和轻度危害。     

长岛县海岛潮间带沉积物重金属及潜在生态风险评价

以2007年长岛县海岛调查资料为基础,分析了长岛县海岛潮间带沉积物中重金属含量特征及其与有机质含量等之间的相关关系,并对其潜在生态危害进行了评价。结果表明,所有海岛潮间带重金属元素含量均未超过环境背景值;不同海岛间潮间带沉积物中重金属元素与有机质的关系略有差异;长岛县海岛潮间带重金属具有轻微生态危险,该海区可适当发展养殖业和旅游业。     

基于Zeta电位的硅藻土复配剂强化混凝研究

采用硅藻土与传统无机絮凝剂复配处理模拟生活污水,考察硅藻土复配剂强化混凝过程中絮体Zeta电位的变化,以及浊度和COD的去除情况,研究絮体Zeta电位与强化混凝效果的关系。实验结果表明,絮体的Zeta电位与复配剂的强化混凝效果密切相关,可用于反映硅藻土复配剂的混凝处理效果。研究发现,氯化铝复配剂强化混凝时絮体Zeta电位在加药后迅速上升,25min后趋于稳定;絮体Zeta电位在pH值等于7时接近等电点,此时浊度与COD去除率最高,分别达到99.05%和45.77%;用硅藻土复配剂强化混凝时Zeta电位的控制值为-9.0～0mV之间,不同无机絮凝剂与硅藻土复配混凝时获得较好混凝效果的Zeta电位控制值略有差异。     

用自动电位滴定仪测定水的总硬度实验

水的总硬度测定采用EDTA进行络合滴定。实验中用自动电位滴定仪代替人工进行样品分析,由颜色突变判断滴定终点改为电位突变,具有高硬度样品预判断、滴定干扰小、准确度高、节省人力、便于数据记录统计比较等优点。