Seasonal trend of ambient PCDD/Fs in Tianjin City, northern China using active sampling strategy

The spatial concentrations, seasonal trends, profiles and congener pairs of ambient polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were investigated within a seasonally active sampling scheme during Jun 2008 and Jan 2009 in Tianjin City, northern China. The PCDD/F concentrations ranged 14.2-172 fg I-TEQ/m³ (average 69.3 fg I-TEQ/m³) in summer and (89.8-1.01) × 10³ fg I-TEQ/m³ (average 509 fg I-TEQ/m³) in winter, respectively, except for the E-waste dismantling site where much higher values were observed (1.04 × 10³ fg I-TEQ/m³ in summer and 7.123 × 10³ fg I-TEQ/m³ in winter). The results indicated a significantly seasonal trend with higher TEQ values in winter as compared with summer, which could be related to increased emission sources and seasonal variations of the atmospheric boundary layer height. 2,3,4,7,8-PeCDF was the dominant contributor to the total PCDD/F toxic equivalents, and 2,3,7,8-TCDD was detected at almost all the sampling sites in winter. Most of the similarly substituted PCDD/F congener pairs exhibited high correlations, suggesting that they might have similar environmental fate or sources. But different seasonal and spatial distributions of PCDD/F concentrations indicated that the emission sources might be intermittent.     

Measurement of air exchange rates in different indoor environments using continuous CO2 sensors

A new air exchange rate (AER) monitoring method using continuous CO₂ sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m³ environmental chamber at different AERs (0.1-10.0 hr^-1). AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO₂ sensors coupled with data loggers. Indoor temperature, relative humidity (RH), and CO₂ concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved: duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr^-1 in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr??1 in fall, and 0.12 to 1.39 hr^-1 in winter with a median AER of 1.15.     

城区地表径流面源污染和河道水环境治理的研究

河流为人类提供了多样的生态服务功能,然而城市化对河流生态系统健康状况造成严重的影响。随着点源污染的有效管理控制,非点源污染降雨径流己成为造成城市地表水环境污染的主要原因。为了改善河道水质,引调清水激活城市内河水体,提高河道的水环境自净能力,有效改善城市水环境。文章以南京河西水系为例,利用Saint-Venant方程组对水系建立一维水动力模型,并通过汇流结点水位法对方程组进行数值求解;对WASP5水质模型进行二次开发用于水质模拟;建立水质模型和一维河网水动力模型的耦合模型,将水动力模型计算所得到的水动力参数耦合到WSAP5水质模型中,模拟降雨过程以及引调清水过程的河网各河段的水质变量浓度,得出降雨径流对河流的污染程度以及引清冲污措施对河流水质改善的效果并优化调水过程。     

硬叶空气凤梨对铅的富集特征研究

空气凤梨是一类生长在空气中、不需要土壤的特殊植物,是有效的监测环境变化的指示植物。文章以硬叶空凤为材料,以环境中最典型的污染物—铅对其进行胁迫处理后,发现硬叶空凤对铅具有很强的耐性,而且可对铅进行有效的富集,是一种合适的指示铅污染的植物。扫描电镜和能谱分析表明,不论何种铅浓度处理植物体,硬叶空凤叶表鳞片中都可检测到铅元素的存在,进一步表明叶表鳞片很可能是铅等重金属元素的主要富集结构。另外,硬叶空凤叶表鳞片的3类细胞在富集铅时所起的作用是不同的,最内部的碟状细胞中铅的含量要大于中间的环状细胞,更大于最外部的翼状细胞,暗示铅的迁移是一种代谢性主动吸收过程。     

黄土高原坡耕地沟蚀土壤质量评价

黄土高原坡耕地沟蚀广泛而严重。科学评价沟蚀土壤质量是侵蚀环境下土壤保育和利用的重要基础。论文以沟间土壤为对照,分析了坡耕地沟蚀对土壤质量单因子的影响并建立了沟蚀土壤质量综合评价模型。利用加权和法对黄土高原坡耕地不同沟蚀深度下土壤质量进行综合评价。结果表明：①沟蚀对坡耕地不同土壤质量因子的影响有较大差异。沟蚀导致土壤硬化,pH值增加,而土壤团聚体和养分含量（除全磷）随着沟蚀深度增加表现出明显的层次性,近似呈＂W＂型变化规律。②沟蚀深度对土壤质量的影响可以用幂函数y=0.866 8 x-0.142（R2=0.877）较好地拟合。微度侵蚀（〈5 cm）、中度侵蚀（5～30 cm）和重度侵蚀（30～50 cm）的土壤质量指数较沟间土壤分别降低了10.6%、27.9%和36.5%。沟蚀深度5 cm和30 cm是土壤质量显著下降的两个关键点。③反映沟蚀土壤质量的指标可以归为肥力因子、质地因子和结构因子三类。土壤有机质、水稳性团聚体、土壤比表面积和容重4项指标能够很好地反映土壤质量状况,可作为坡耕地沟蚀土壤质量的表征指标。     

温榆河浮游动物多样性及水质改善效果评价

为评价自2010年5月罗马东湖示范工程运行后温榆河水质变化情况,于2010年5月-2011年2月间,定期采集该流域大型浮游动物,并从浮游动物种类、敏感种数量以及Shannon-Weaver生物多样性指数(H')等3个方面对温榆河流域大型浮游动物多样性进行分析。2010年5月-10月,罗马东湖大型浮游动物种类增加,敏感种数量上升,Shannon-Weaver生物多样性指数(H')由0.650 1升至2.134 2,水质由重污型改善为β-中污型;2010年11月-2011年2月,H'降低,说明季节变化对生物多样性影响较大。下游苇沟桥由于接受示范工程水域敏感种,H'与罗马东湖具有相同变化趋势,但受到清河水体影响,实际水质较差。苇沟桥下游北关闸敏感种再次消失,H'降低。其他位点H'明显较低,并受季节变化影响。结果表明:温榆河水质改善示范工程对局部水域的水质改善效果明显。要实现河流健康目标,必须控制污染源,由点到面,逐步由局部生态修复过渡到流域生态系统的恢复。     

东南沿海生物气溶胶的扩散模拟研究

将沿海扩散模式OCD与区域输送模式相嵌套,集成在区域空气质量模拟系统RegAQMS中,由天气研究和预报模式WRF提供气象场,大气边界层模式计算湍流场和边界层特征参数,并引入生物气溶胶的干湿沉积、生物学衰变、温度和湿度衰减、紫外辐射衰减等过程,使得RegAQMS具备模拟生物气溶胶浓度分布的能力.利用改进后的RegAQMS,以2008年7、8月为例,针对东南沿海地区,进行了口蹄疫病毒生物气溶胶扩散有关物理和生物过程的敏感性试验,对地面口蹄疫病毒浓度进行模拟和风险等级评估.敏感性试验表明,考虑干湿沉积、温度、湿度和生物学衰减过程之后,7、8月地面病毒平均浓度(≥0.01μg.m-3的网格点平均)分别减小61.9%和65.6%,污染区面积分别减小25.6%和50.1%,温度衰减是影响夏季病毒浓度的最主要过程,生物学衰减和干湿沉积也起着较大的作用,湿度衰减的影响很小.风险和感染评估结果表明,在与前人研究类似的源释放条件下,研究区域大部分为低等风险区和安全区,高等风险区以上的面积较小,呈条状分布在两个主要风频的下风向,7月和8月的风险区面积分别占整个区域面积的61.6%和54.2%,感染区面积占整个区域面积的不到1%.受海洋大气和海峡地形作用的影响,流场规则、日风向变化和水平湍流强度小,这些是引起病毒较高传播风险和感染的主要原因.     

1980—2010年温榆河的水环境质量时空演变特征

以温榆河流域的主要超标污染物 COD 和氨氮为研究对象,通过历史数据和现场调查,系统研究了1980—2010年间温榆河的水环境质量时空演变特征.结果表明,温榆河流域水环境质量经历了清洁-污染-重度污染-污染遏制的过程,但水质现状均不达标;温榆河流域水环境质量好坏依次是上段>下段,温榆河>坝河>清河,并且Pearson相关分析表明,温榆河下段COD和NH+4-N浓度主要受清河影响;温榆河流域COD污染逐步遏制(超标倍数<1)、NH+4-N污染凸显(超标倍数8～20),耗氧物质处于从COD为主向NH+4-N为主转换的阶段;支流清河和坝河不仅是温榆河干流入河污染负荷的首要输入途径,而且支流上污水集中处理设施的排水是温榆河干流的首要补给来源(70.1%),其运行状况与升级改造对改善温榆河水环境质量至关重要.     

An air quality forecasting system in Beijing - Application to the study of dust storm events in China in May 2008

An air pollution forecast system, ARIA Regional, was implemented in 2007-2008 at the Beijing Municipality Environmental Monitoring Center, providing daily forecast of main pollutant concentrations. The chemistry-transport model CHIMERE was coupled with the dust emission model MB95 for restituting dust storm events in springtime so as to improve forecast results. Dust storm events were sporadic but could be extremely intense and then control air quality indexes close to the source areas but also far in the Beijing area. A dust episode having occurred at the end of May 2008 was analyzed in this article, and its impact of particulate matter on the Chinese air pollution index (API) was evaluated. Following our estimation, about 23 Tg of dust were emitted from source areas in Mongolia and in the Inner Mongolia of China, transporting towards southeast. This episode of dust storm influenced a large part of North China and East China, and also South Korea. The model result was then evaluated using satellite observations and in situ data. The simulated daily concentrations of total suspended particulate at 6:00 UTC had a similar spatial pattern with respect to OMI satellite aerosol index. Temporal evolution of dust plume was evaluated by comparing dust aerosol optical depth (AOD) calculated from the simulations with AOD derived from MODIS satellite products. Finally, the comparison of reported Chinese API in Beijing with API calculated from the simulation including dust emissions had showed the significant improvement of the model results taking into account mineral dust correctly.     

Air quality management in China: Issues, challenges, and options

This article analyzed the control progress and current status of air quality,identified the major air pollution issues and challenges in future,proposed the long-term air pollution control targets,and ...