甲基对硫磷在水-气界面挥发的动力学研究

研究了挥发时间、温度和气流量对农药甲基对硫磷在水-气界面挥发行为的影响.研究结果表明,随着温度升高、气流量增大甲基对硫磷挥发量明显增大,温度和气流量是影响甲基对硫磷挥发的主要因素;挥发时间在0～8 h内甲基对硫磷挥发量的变化较大,8h之后甲基对硫磷的挥发量基本不变化.研究了农药甲基对硫磷在水-气界面的挥发动力学.建立了甲基对硫磷在水-气界面挥发的动力学模型,模型计算所得的预测值与实测值基本吻合,相对误差≤5%,表明可用该动力学模型来预测甲基对硫磷在水-气界面的挥发行为.     

闽江河口表层水体氧化亚氮释放时空变化特征及其影响因素

以闽江口水体为研究对象,研究了闽江河口上段(城市河口段)、河口中段和河口下段(口外海滨段)不同季节水体N₂O的溶存浓度、水-气界面通量及其环境影响因子.结果表明,闽江口水体N₂O溶存浓度为0.99～55.92 nmol·L^-1,N₂O饱和度为8.0%～396%,水-气界面N₂O释放通量为-5.21～7.91μg·m^-2·h^-1.从季节差异看,7月(夏季)、9月(秋季)和12月(冬季)水体中N₂O过饱和,表现为N₂O的排放“源”;4月(春季)水体中N₂O不饱和,表现为N₂O“汇”.水-气界面N₂O释放通量呈夏、秋和冬季高,春季低的季节变化规律.在空间变化上,水-气界面N₂O释放通量从河口上段到下段降低,与氮含量变化趋势一致.N₂O间接性释放因子为0.004%～0.128%,低于IPCC...     

Spatial and seasonal variations of polycyclic aromatic hydrocarbons in Haihe Plain, China

A dynamic fugacity model was developed to simulate the spatial and seasonal variations of PAHs in Haihe Plain, China. The calculated and measured concentrations exhibited good consistency in magnitude with deviations within a factor of 4 in air and 2 in soil. The spatial distributions of PAHs in air were mainly controlled by emission while the seasonal variations were dominated by emission and gas-particle partition. In soil, the spatial distributions of PAHs were controlled by the soil organic carbon content while the seasonal variations were insignificant. The severest soil contamination was observed in Shanxi and followed by the southwest of Hebei province. Transfer fluxes of total PAHs between air and soil were calculated. The spatial distribution of air-to-soil flux was closely related to the landcover while the soil-to-air flux changed with soil organic matter content. Monte Carlo simulation was done to evaluate the uncertainty of the estimated results in air.     

可燃物填充比对火蔓延影响的实验研究

提出了一种可精确控制燃料床填充比的方法.以刨花为燃料,开展了可燃物填充比对火蔓延影响的系统性实验研究.分析了火焰长度、火焰倾斜角、火蔓延速率、质量损失速率和热流密度随填充比的变化规律.研究发现,随填充比增大,火焰长度逐渐减小,火焰倾斜角逐渐增加,导致火焰热辐射降低、火蔓延速率减小.当填充比小于0.06时,燃料消耗率接近...     

基于COD通量的钱塘江流域水污染生态补偿量化研究

水污染生态补偿是解决流域跨界水污染纠纷的重要措施。以行政单元为补偿主体,通过交界断面水质目标确立上下游政府间的水污染生态补偿责任,建立基于污染物通量的生态补偿量化计算方法,并提出了生态补偿运作模式。以钱塘江流域为例,根据2004年钱塘江流域水质状况,在75%保证率的水文条件下,基于COD通量估算了流域内各县（市）间水污染生态补偿量。结果表明,生态补偿量反映区域污染特点,上游地区基本上都是接受补偿者,而呈结构性污染的地区是生态补偿支付者,部分区域补偿强度超过当地经济发展水平,表明其发展不具有可持续性。钱塘江流域水污染生态补偿模式可以是政府层面上的财政支助,也可以通过项目支持、技术支持等形式实现区域间的补偿。通过生态补偿机制的实施,将对流域水环境保护起到积极的激励作用。     

Copper availability and bioavailability are controlled by rhizosphere pH in rape grown in an acidic Cu-contaminated soil

We evaluated how root-induced changes in rhizosphere pH varied and interacted with Cu availability and bioavailability in an acidic soil. Rape was grown on a Cu-contaminated acidic soil, which had been limed at 10 rates. Soil Cu bioavailability was not influenced by liming. However, liming significantly decreased CaCl₂-extracted Cu for pH between 3.7 and 5.1. Little effect was found for pH above 5.1. For soil pH < 4.4, CaCl₂-Cu contents were smaller in rhizosphere than uncropped soil. Rhizosphere alkalisation occurred at pH < 4.8, while acidification occurred at greater pH. This explained the changes of CaCl₂-Cu in the rhizosphere at low pH and the absence of pH dependency of Cu bioavailability to rape. In addition, apoplastic Cu in roots increased with increasing soil pH, most probably as a result of increased dissociation and affinity of cell wall compounds for Cu.     

Factors affecting nitrate distribution in shallow groundwater under a beef farm in South Eastern Ireland

Groundwater contamination was characterised using a methodology which combines shallow groundwater geochemistry data from 17 piezometers over a 2 yr period in a statistical framework and hydrogeological techniques. Nitrate–N (NO₃-N) contaminant mass flux was calculated across three control planes (rows of piezometers) in six isolated plots. Results showed natural attenuation occurs on site although the method does not directly differentiate between dilution and denitrification. It was further investigated whether NO₃-N concentration in shallow groundwater (<5 m below ground level) generated from an agricultural point source on a 4.2 ha site on a beef farm in SE Ireland could be predicted from saturated hydraulic conductivity (K_sat) measurements, ground elevation (m Above Ordnance Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and distance from a dirty water point pollution source. Tobit regression, using a background concentration threshold of 2.6 mg NO₃-N L⁻¹ showed, when assessed individually in a step wise procedure, K_sat was significantly related to groundwater NO₃-N concentration. Distance of the point dirty water pollution source becomes significant when included with K_sat in the model. The model relationships show areas with higher K_sat values have less time for denitrification to occur, whereas lower K_sat values allow denitrification to occur. Areas with higher permeability transport greater NO₃-N fluxes to ground and surface waters. When the distribution of Cl⁻ was examined by the model, K_sat and ground elevation had the most explanatory power but K_sat was not significant pointing to dilution having an effect. Areas with low NO₃ concentration and unaffected Cl⁻ concentration points to denitrification, low NO₃ concentration and low Cl⁻ chloride concentration points to dilution and combining these findings allows areas of denitrification and dilution to be inferred. The effect of denitrification is further supported as mean groundwater NO₃-N was significantly (P < 0.05) related to groundwater N₂/Ar ratio, redox potential (Eh), dissolved O₂ and N₂ and was close to being significant with N₂O (P = 0.08). Calculating contaminant mass flux across more than one control plane is a useful tool to monitor natural attenuation. This tool allows the identification of hot spot areas where intervention other than natural attenuation may be needed to protect receptors.     

基于污染物来源的洞庭湖水环境生态补偿主客体研究

生态补偿主客体研究是制定及实施生态补偿政策的核心要素之一。本研究从系统分析的角度出发,基于2014年洞庭湖主要入湖河流水质、水量情况,核算了主要入湖河流总氮、总磷通量,并结合2014年洞庭湖生态经济区污染物排放情况,详细分析了洞庭湖总氮、总磷的来源,以此为依据界定了洞庭湖水环境生态补偿的主体与客体。结果显示,洞庭湖水体中总氮、总磷的贡献以洞庭湖生态经济区之外地区,通过四水、三口排入洞庭湖为主。基于此,本研究建议洞庭湖水环境生态补偿的主体省级层面应为湖南省和湖北省,而省外层面则为国家作为补偿主体对洞庭湖生态经济区进行补偿。     

三峡水库上空甲烷浓度时空变化及与水库甲烷通量的关系

2010年,对三峡水库水-气界面上空05m处和岸边甲烷的浓度进行全年的观测,并采用静态浮箱-气相色谱法测定水库水-气界面上的甲烷通量,研究了三峡水库上空的甲烷浓度的背景值及其与甲烷排放强度之间的关系。结果表明：三峡水库上空甲烷浓度的年平均值为2216±0224 mL/m3,岸边甲烷浓度的年平均值为2211±0206 mL/m3,两者差异不显著;除夏季时云阳上空的甲烷浓度较高外（2850 mL/m3）,其余地点上空的甲烷浓度都接近年平均值;三峡水库上空的甲烷浓度存在明显的空间差异,上游地区（云阳）上空的甲烷浓度（231±033 mL/m3）显著高于下游地区（秭归：214±013 mL/m3,巫山：220±018 mL/m3）,坝后河流（三斗坪：221±016 mL/m3）上空的甲烷浓度高于坝前秭归处,但差异不显著。这一格局与水库中甲烷通量的空间变异基本相同,即从上游到下游（云阳、巫山、秭归）江面上甲烷通量依次为0454,0260和0115 mg/（m2·h）,呈下降趋势,坝后三斗坪处的甲烷通量（0280 mg/（m2·h））显著高于坝前秭归处通量,这表明：水库的水-气界面上的甲烷排放强度是影响水库上空甲烷浓度变化的主要因素     

湘中地区2010年5月两次暴雨过程的雷达特征对比分析

2010年5月5~6日和5月12~13日,湘中发生了两次区域性暴雨。运用了自动站降水资料、多普勒天气雷达基本反射率和基本径向速度资料以及NCEP提供的FNL资料,分析了这两次暴雨的雷达回波特征,并从水汽和地形两方面分析了两次暴雨的影响因素。结果表明：两次暴雨的环流形势场不同。 “100506”暴雨强降水回波呈带状自西南向东北扫过娄底,而“100513”暴雨强降水回波呈块状自西往东范围逐渐加强;两次暴雨都有逆风区存在,逆风区的范围和强度对应着强降水的范围与强度。两次暴雨水汽主要来自孟加拉湾和南海,“100506”暴雨发生在切变线附近;“100513”暴雨发生在切边线南侧的辐合区内。娄底西部、北部、中部山地的阻挡和抬升作用以及冷暖气流交汇也是暴雨产生的重要原因之一