On-going nitrification in chloraminated drinking water distribution system (DWDS) is conditioned by hydraulics and disinfection strategies

Within the drinking water distribution system (DWDS) using chloramine as disinfectant, nitrification caused by nitrifying bacteria is increasingly becoming a concern as it poses a great challenge for maintaining water quality. To investigate efficient control strategies, operational conditions including hydraulic regimes and disinfectant scenarios were controlled within a flow cell experimental facility. Two test phases were conducted to investigate the effects on the extent of nitrification of three flow rates (Q = 2, 6, and 10 L/min) and four disinfection scenarios (total Cl₂=1 mg/L, Cl₂/NH₃-N=3:1; total Cl₂=1 mg/L, Cl₂/NH₃-N=5:1; total Cl₂=5 mg/L, Cl₂/NH₃-N=3:1; and total Cl₂=5 mg/L, Cl₂/NH₃-N=5:1). Physico-chemical parameters and nitrification indicators were monitored during the tests. The characteristics of biofilm extracellular polymetric substance (EPS) were evaluated after the experiment. The main results from the study indicate that nitrification is affected by hydraulic conditions and the process tends to be severe when the fluid flow transforms from laminar to turbulent (2300<Re<4000). Increasing disinfectant concentration and optimizing Cl₂/NH₃-N mass ratio were found to inhibit nitrification to some extend when the system was running at turbulent condition (Q = 10 L/min, Re = 5535). EPS extracted from biofilm that was established at the flow rate of 6 L/min had greater carbohydrate/protein ratio. Furthermore, several nitrification indicators were evaluated for their prediction efficiency and the results suggest that the change of nitrite, together with total organic carbon (TOC) and turbidity can indicate nitrification potential efficiently.     

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.     

Particulate matter pollution in Kunshan High-Tech zone: Source apportionment with trace elements, plume evolution and its monitoring

Particulate matter(PM) in the Kunshan High-Tech zone is studied during a three-month campaign. PM and trace elements are measured by the online pollution monitoring, forecastwarning and source term retrieval system AS3. Hourly measured concentrations of PM_(10), PM_(2.5) and 16 trace elements in the PM_(2.5) section(Ca, Pb, Cu, Cl, V, Cr, Fe, Ti, Mn, Ni, Zn, Ga, As, Se, Sr, Ba)are focused. Source apportionment of trace elements by Positive Matrix Factorization modeling indicates that there are five major sources, including dust, industrial processing, traffic,combustion, and sea salt with contribution rate of 23.68%, 21.66%, 14.30%, 22.03%, and 6.89%,respectively. Prediction of plume dispersion from concrete plant and traffic emissions shows that PM_(10) pollution of concrete plant is three orders of magnitude more than that of the traffic. The influence range can extend to more than 3 km in 1 hr. Because the footprint of the industrial plumes is constantly moving according to the local meteorological conditions, the fixed monitoring sites scattered in a few hundred meters haven't captured the heaviest pollution plume at the local scale of a few km~2. As a more intensive monitoring network is not operationally possible, the use of online modeling gives accurate and quantitative information of plume location, which increases the spatial pollution monitoring capacity and improves the understanding of measurement data. These results indicate that the development of the AS3 system, which combines monitoring equipment and air pollution modeling systems, is beneficial to the real-time pollution monitoring in the industrial zone.     

海榄雌瘤斑螟的生物学特性及Bt对其幼虫的毒力和防效

海榄雌瘤斑螟(Acrobasis sp.)是危害马鞭草科澳洲海榄雌(Avicennia marina var.austrasica)的主要害虫.在深圳红树林一年发生6~7代,每个世代25~32d,其中幼虫历期13~16d,蛹5~6d,成虫7~10d,卵3~5d.幼虫剥食海榄雌的叶肉,8月低龄幼虫蛀食嫩芽及种子,10月低龄幼虫开始在嫩芽内越冬,翌年3月上中旬,越冬幼虫开始活动.每年4月下旬至6月中旬爆发的第2代和第3代密度较大,造成海榄雌大面积危害.在室内,用Bt感染2龄海榄雌瘤斑螟,致死浓度(C)-死亡几率值(Y)测定的回归线为Y=4.66 1.78C,80%的致死浓度LC80为4.60IU/mL;致死时间(T)-死亡几率值(Y)测定的回归线为Y=4.305T-1.51,80%的致死时间LT80为50.86h.在林间,用8~10IU/mL的Bt稀释液喷雾对海榄雌瘤斑螟进行防治实验,平均防效为90.61%.图3表5参8     

Mapping farmers’ vulnerability to climate change and its induced hazards: evidence from the rice-growing zones of Punjab,Pakistan

Environmental Science and Pollution Research - In developing countries like Pakistan, agriculture constitutes the primary source of support for the majority of rural and the adjacent urban...     

深圳福田红树林无瓣海桑与海桑群落的重金属累积和循环

研究了深圳福田红树林无瓣海桑与海桑群落对重金属Cu、Pb、Zn、Cr、Ni元素的吸收、累积、分布和循环.结果表明,该林地表层土壤(0～30cm)Cu、Pb、Zn、Cr、Ni元素的储量关系为Zn＞Pb＞Ni＞Cr＞Cu;群落中3种植物对土壤中5种重金属元素富集能力的大小依次为海桑＞无瓣海桑＞秋茄.该群落Cu、Pb、Zn、Cr、Ni的现存累积量分别为:23019.61、23429.65、117870.41、6835.79、12995.08μg/m²;年吸收量分别为:6592.20、266     

整地施肥对尾叶桉生长及土壤性状的影响

整地施肥试验结果表明，全垦、带垦和穴垦三种整地方式以及施肥对尾叶按造林成活率和保存率均无明显的影响，成活率在９５％－９８．８％之间，保存率在９２．１％－９７．７％之间．整地能改变土壤性状，如土壤孔隙度全垦为５７．８８％。穴垦为４９．４２％；对林木生长有促进作用，但作用效果很快减少，如造林３年后的林木材积全垦、带垦分别为穴垦的１３６．４％和１２０．０％，５年后却分别下降到１１６．５％和１０８．３％．施肥可提高土壤养分，促进林木生长．造林５年后的调查结果，穴垦施肥林地的土壤有机质、速效Ｎ分别为１５．４４７ｇ／ｋｇ和４９．２３０ｍｇ／ｋｇ，林木年均树高生长为１．２５ｍ；不施肥处理的有机质、速效Ｎ分别为１０．３８８ｇ／ｋｇ和３５．７１５ｍｇ／ｋｇ，林木年平均生长量为０．３５ｍ；林木材积施肥处理的为不施肥的９．８倍．整地施肥还可提高林木叶片的养分含量．     

汽油添加剂MTBE的最新研究及替代品

随着国家对环境保护的日趋重视，目前我国大部分城市禁止销售加铅汽油，使用TMBE作为汽油添加剂，可以提高汽油含氧量减少汽车尾气中的污染物，但由于其本身的性质，对环境可能带来的一些问题，也正被人们所重视。     

低温热氧化法强化剩余污泥微生物燃料电池的产电特性

城市污水处理厂污泥因有机物含量高而成为微生物燃料电池(MFC)应用研究的主要方向之一,而污泥中有机质的释放成为限制其发展的主要因素.本实验利用低温热解和过氧化氢氧化处理的耦合方法预处理城市污水处理厂污泥,分析了其作为燃料对MFC产电性能的影响.研究表明,利用预处理后的污泥上清液作为燃料,预处理温度、时间、pH值和过氧化氢投加量对MFC的产电性能影响大.当温度、时间、pH值和过氧化氢分别为100℃、90 min、11和500 g·kg TSS~(-1)的预处理条件下,MFC功率密度最大,分别为235、287、233.2、280 mW·m~(-3).采用热氧化法预处理污泥,可有利于污泥的破解,使能被产电菌利用的营养物质增多,提高了MFC产电特性,可为污泥资源化利用提供有益的参考.     

Effects of mangrove plant species on accumulation of heavy metals in sediment in a heavily polluted mangrove swamp in Pearl River Estuary,China

Environmental Geochemistry and Health - The present study compared accumulation of heavy metals in a mangrove swamp dominated by Kandelia obovata with that by Sonneratia apetala in Pearl River...