Association between plant species diversity and edaphic factors in the lower reaches of the Heihe River,northwestern China

The lower reaches of the Heihe River, in northwestern China, is characterised by unique local edaphic conditions that have influenced the development of local desert riparian forests. This study examines the variations in spatial variation patterns to reveal the relationships between plant species diversity and soil moisture/salinity/texture gradients at different soil depths, providing insights into the management and restoration of vegetation in ecosystems in the study area. The species–environmental relationships are investigated by redundancy analysis based on the plant species diversity matrix and the edaphic gradient matrix. A survey of 61 sampling plots identified 37 plant species in the study area. The distribution pattern of the plant species diversity are mainly affected by soil moisture, soil salinity, and soil texture at different soil depths. These edaphic factors are able to explain 98.47% of the total variation in the analysed vegetation dataset. Soil moisture, salinity, and texture content vary in terms of both the soil depths and the vegetation types in the study area. The plant community Class IV, xeric shrub, has the lowest soil water content among different vegetation types. The surface soil salinity differs for different plants and follows the order: Sophora alopecurides?>?Tamarix chinensis?>?Populus euphratica.     

Photodegradation of bisphenol A in Fe(Ⅲ)-oxalate complexes solution

The aqueous photodegradation of bisphenol A (BPA) in the presence of Fe(Ⅲ)-oxalate complexes (Fe(Ⅲ)-Ox), which are common compositions of natural water, was investigated in this study. BPA underwent rapid indirect photolysis in Fe(Ⅲ)-Ox solution under simulated solar irradiation, proceeding pseudo-first-order kinetics. The photolysis rate increased with decreasing pH or initial processes of Fe(Ⅲ)-Ox complexes and contributed to the photooxidation of BPA, were determined by molecular probe and electron spin resonance (ESR) methods with the steady-state concentration of 2.56 × 10-14 mol/L. Superoxide anion radical (O2.-) was consistructural analysis of the intermediate photoproducts of BPA in Fe(Ⅲ)-Ox complexes solution, the possible degradation pathways of of Fe(Ⅲ) may affect the environmental fate of BPA in natural water significantly.     

酸雨环境对轻质土的工程性质的影响

酸雨是在大气环境发生变化后引起的环境污染之一,其特征是分布范围广、作用时间长。轻质土作为一种新型的地基基础材料,在建设工程具有广泛的应用前景。探讨酸雨环境对轻质土工程性质的影响,对于掌握轻质土的基本特性具有重要意义。     

活性炭滤池深度处理水中有机物

生物活性炭滤池能有效去除常规工艺出水中CODMn、UV254、三氯甲烷生成势和一溴二氯甲烷生成势,但在相同水力停留时间下,新鲜活性炭滤池对这些有机物去除效果更显著。生物活性炭滤池出水二溴一氯甲烷生成势升高,而新鲜活性炭滤池对二溴一氯甲烷生成势有时有一定的去除效果。     

Performance Evaluation of the SLEUTH Model in the Shenyang Metropolitan Area of Northeastern China

Performance evaluation is crucial for the development and improvement of an urban cellular automata model, such as SLEUTH. In this paper, we employed multiple methods for map comparison and model validation to evaluate the simulation performance of the SLEUTH urban growth model in the Shenyang metropolitan area of China. These multiple methods included the relative operating characteristic (ROC) curve statistic, multiple-resolutions error budget, and landscape metrics. They were used to quantitatively examine model performance in terms of the amount and spatial location of urban development, urban spatial pattern and prediction ability. The assessment results showed that SLEUTH performed well in the way of the quantitative simulation of urban growth for this case study. Similar to other urban growth models, however, the simulation accuracy for spatial location of new development at the pixel scale and urban spatial pattern still needs to be improved greatly. These inaccuracies might be attributed to the structure and nature of SLEUTH, local urban development characteristics, and the temporal and spatial scale of its application. Finally, many valuable suggestions had been put forward to improve simulation performance of SLEUTH model for spatial location of urban development in the Shenyang metropolitan area.     

基于新空气质量标准的全国大气环境承载力评价

随着中国环境问题特别是大气环境问题的凸显,环境承载能力研究成为国内各界关注的热点。采用大气污染物年均质量浓度与新的空气质量标准比较的方法即超标倍数法,对全国330个地级城市进行大气环境承载力评价。评价结果表明,有70%的城市大气环境超载,大气环境承载形势严峻。超载最严重地区为京津冀及周边区域,长三角地区、中部大部分地区。PM2.5为大多数重点城市超载的首要污染物。通过对比大气环境承载指数与污染物排放总量、污染排放强度、人口、第二产业、地形、气象等因素的相关关系发现,不同地区主要影响因素不同,应该采取分区域、季节等差别化手段控制污染物排放,提高环境承载能力。     

全国及重点区域臭氧污染现状

分析2013—2016年中国开展臭氧(O_3)监测的338个城市(港、澳、台不在统计范围)O_3污染现状和时空变化特征,结果表明:中国城市O_3污染日益突出,2015年54个城市O_3超标,75.9%的O_3超标城市位于京津冀及周边、长三角、珠三角区域,O_3区域污染特征显著。74个城市O_3浓度整体呈上升趋势并向高值区集中,京津冀区域O_3污染最为严重。O_3污染季节变化特征明显,O_3污染主要集中于5—10月,京津冀、长三角和珠三角区域O_3最高超标天数分别出现在6、5、10月。建议加强O_3成因分析,建立O_3污染控制策略,有效应对O_3污染,实现科学减排。     

于桥水库浮游植物群落特征

于桥水库是天津市惟一饮用水水源地,为了研究该水库浮游植物群落特征,于2012年春、夏、秋对于桥水库浮游植物进行了监测分析。结果表明:该水库共鉴定出绿藻(Chlorophyta)、蓝藻(Cyanophyta)、硅藻(Diatoms)、裸藻(Euglenophyta)、甲藻(Pyrrophyta)、隐藻(Cryptophyta)和黄藻(Xanthophyta)7门114种,群落组成以绿藻-硅藻门为主;浮游植物细胞密度具有明显的季节变化规律,表现为春季较低,夏季急剧增长,到了秋季又有所回落。优势种对于桥水库水质的评价结果表明,春季为中营养水体,夏季为富营养化水体,秋季为中富营养水体。春、夏、秋季于桥水库香农-韦弗多样性指数平均值分别为3.22、2.51和3.17,说明2012年于桥水库春季、秋季为贫营养水体,夏季为中营养水体,且有暴发水华的危险。     

北京市主要水污染物排放特征及水质改善对策

污染排放信息是环境决策的重要依据。分析了北京市水环境质量的现状,基于最新源排放清单,解析北京市当前主控污染物COD、氨氮排放的结构特征和空间特征,以期为北京市开展基于流域综合治理的水污染控制和水环境管理提供依据。按照工业源、农业源、生活源和集中处理设施的环境统计口径,2013年,COD、氨氮的排放构成分别为2.7%、37.1%、35.0%、25.3%和1.5%、20.1%、54.8%、23.6%。其中,农业源中畜禽养殖排放是主要来源,COD、氨氮总排放分别占农业源总排放量的94.7%和87.0%。在北京市五大水系中,北运河流域排放量最大,COD、氨氮排放量分别占全市总排放量的53.3%和57.4%。为改善北京市水环境质量,建议从加快污水处理厂提标改造、推动面源污染治理、加强水利联通、合理规划城市规模布局等4个方面入手。     

考虑水温变化的变降解系数在北京市北运河水质模拟中的应用

综合降解系数是水质模拟预测、水环境容量计算中的关键参数之一,并且受温度影响较大。首先基于北京市北运河代表站2010年逐日水温资料,根据描述氨氮降解系数与温度之间数量关系的经验公式,得到随水温变化的动态降解系数以及年均水温对应的恒定降解系数,并采用模型试错法进行修正。然后基于MIKE11模型,模拟了采用变降解系数和恒定降解系数2种情景下北运河榆林庄断面氨氮浓度的变化。结果表明:2种情景均能较好地模拟氨氮浓度的年变化趋势,但采用变降解系数下大多月份模拟得到的月均质量浓度相对实测值误差较小,尤其是4—12月各月平均质量浓度模拟误差控制在15%以内,全年日均质量浓度模拟误差不足4%,模型表现更为稳定。