深圳大气湿沉降对典型屋面径流水质的影响

屋面雨水是一种重要的非常规水源,其水质受大气湿沉降影响。该研究以深圳大学城水泥砂浆材质的屋面为例,测定了2011年14场降雨的雨前大气环境质量、大气降水水质和屋面径流水质,对比了大气降水及屋面径流中组分浓度的差异,分析了湿沉降与屋面径流污染负荷的关系及其影响因素。结果表明:(1)湿沉降中NH4+、乙酸、甲酸和乙二酸等组分与屋面材料及累积物发生化学反应,使得这些组分在屋面径流中的负荷显著减少;(2)湿沉降是屋面径流中Na+、K+、Mg2+、Ca2+和SO42-组分负荷的少部分来源;(3)而湿沉降是屋面径流中TOC、F-和NO3-组分负荷的主要来源;(4)雨前大气环境质量对湿沉降组分浓度有显著影响。因此,湿沉降对屋面径流组分负荷影响显著,城市屋面径流水质管理中应充分考虑湿沉降的影响。

重庆主城区城乡结合部大气污染成因调查及污染防治对策研究

城镇与农村结合的区域由于其特殊性,其污染防治问题日益突出。从区域环境空气质量监测数据分析,污染物主要以细颗粒物(PM_(2.5))和可吸入颗粒物(PM_(10))为主,SO_2、NO_x、CO等较主城区偏高;重庆典型城乡结合区域的大气污染问题的调查结果表明,秸秆焚烧、散煤的使用以及小型生产型单位排放是城乡结合区域局地大气污染的重要来源;提出了控制扬尘、秸秆综合利用、能源结构优化等城乡结合区域污染防治对策。

矿区规划环境影响评价大气专题编制探索

针对新大气导则和矿区规划环评的具体要求,对矿区规划环评中大气预测过程中需要规范的内容进行了简述,并对大气监测布点和大气环境影响预测及矿区承载能力等进行了分析,提出了合理的建议,以供参考。

Simulated seasonal variations in nitrogen wet deposition over East Asia

The regional air quality modeling system Regional Atmospheric Modeling System–Community Multiscale Air Quality was applied to estimate the spatial distribution and seasonal variation in nitrogen wet deposition over East Asia in 2010. The simulated results were evaluated by comparing modeled precipitation rates and ion concentrations, such as ammonium（NH_4~＋）, nitrate（NO_3^-）, and sulfate, in rainwater, against observations obtained from Acid Deposition Monitoring Network in East Asia and meteorological stations in China. Comparison of simulated and observed precipitation showed that the modeling system can reproduce seasonal precipitation patterns reasonably well. For major ion species, the simulated results in most cases were in good agreement with those observed. Analysis of the modeled wet deposition distributions indicated that China experiences noticeable variation in wet deposition patterns throughout the year. Nitrogen wet deposition（NH_4~＋ ＋ NO_3^-） during summer and spring accounted for 71% of the annual total（3.9 Tg N yr^（-1））, including 42.7% in summer. Precipitation plays a larger role in the seasonal variation of wet deposition; whereas, aerosol concentrations affect its distribution patterns. In China, the amount of annual nitrogen wet deposition ranged from 1 to 18 kg N ha^（-1）. Nitrogen in wet deposition was mainly in the form of NH_4~＋, accounting for 65.76% of the total amount, and the molar ratio of NH_4~＋∕NO_3^- was mostly more than 1, indicating a relatively larger effect from agricultural activities.

Numerical Simulation of CO_2 Concentrations in East Asia with RAMS-CMAQ

The regional air quality modeling system RAMS-CMAQ(Regional Atmospheric Modeling System and Models-3 Community Multi-scale Air Quality) was developed by incorporating a vegetation photosynthesis and respiration module(VPRM) and used to simulate temporal-spatial variations in atmospheric CO2 concentrations in East Asia,with prescribed surface CO2 fluxes(i.e.,fossil fuel emission,biomass burning,sea-air CO2 exchange,and terrestrial biosphere CO2 flux).Comparison of modeled CO2 mixing ratios with eight ground-based in-situ measurements demonstrated that the model was able to capture most observed CO2 temporal-spatial features.Simulated CO2 concentrations were generally in good agreement with observed concentrations.Results indicated that the accumulated impacts of anthropogenic emissions contributed more to increased CO2 concentrations in urban regions relative to remote locations.Moreover,RAMS-CMAQ analysis demonstrates that surface CO2 concentrations in East Asia are strongly influenced by terrestrial ecosystems.

The Structure of a Typical Mei-Yu Front Identified by the Equivalent Temperature

In China's Mainland, the summer monsoon rainy band is referred to as the mei-yu precipitation front, which extends northward from South China to the Yangtze River, Huaihe River, and Yellow River, depending on the season. This paper describes the structure of the mei-yu front associated with a persistent heavy rainfall event that occurred in the summer of 2007. The mei-yu front occurs when the subtropical oceanic warm, moist air mass and the extra tropical continental dry, cold air mass converge on the lee side of the Tibetan Plateau. The authors defined the equivalent temperature using two terms of dry-air temperature and the specific humidity and calculated its horizontal gradient to indicate the mei-yu front. The vertical structure of the mei-yu front and the moist thermal winds surrounding it were examined based on the equivalent temperature.

Calculation of stratosphere–troposphere exchange in East Asia cut-off lows:cases from the Lagrangian perspective

In this study,the authors focus on the cut-off low pressure systems（COLs）lingering over East Asia in late spring and early summer and quantify the two-way stratosphere–troposphere exchange（STE）by 3D trajectory integrations,achieved using a revised version of the UK Universities Global Atmospheric Modelling Programme Offline Trajectory Code（Version 3）.By selecting 10 typical COLs and calculating the cross-tropopause air mass fluxes,it is found that stratosphere-to-troposphere transport（STT）fluxes exist in the center of COLs;and in the periphery of the COL center,troposphereto-stratosphere transport（TST）fluxes and STT fluxes are distributed alternately.Net transport fluxes in COLs are from stratosphere to troposphere,and the magnitude is about 10-4 kg m-2 s-1.The ratio between the area-averaged STT and TST fluxes increases with increasing strength of the COLs.By adopting appropriate residence time,the spurious transports are effectively excluded.Finally,the authors compare the results with previous studies,and find that the cross-tropopause fluxes（CTFs）induced by COLs are about one to two orders of magnitude larger than global CTFs.COLs play a significant role in local,rapid air mass exchanges,although they may only be responsible for a fraction of the total STE.

Practical Paths towards Lowering Black Carbon Emissions

Black carbon （BC） aerosol, accounting for a minor fraction of atmospheric aerosols, is attracting increased attentio1 due to its impact on air quality, human health, and climate change. Focusing on BC emission reduction, this paper give1 a brief introduction to the sources and global distribution of BC. Along with the decrease of BC emissions from sue1 actions as the reduction of global greenhouse gases （GHGs） and regulating local air quality, it also highlights othet BC reduction approaches such as control and improvement of combustion conditions, the elimination of open biomas burning, and the sequestration of BC by biomass pyrolysis. Finally, it is stressed that at this moment there is no enougt reason to push BC reduction into any climate change related negotiations, although BC has been included in some o so-called win-win reduction targets for the quick response to both climate and non-climate appeals.

The seasonal cycle of redistribution of atmospheric mass between continent and ocean in the Northern Hemisphere

Using NCEP/NCAR and ERA-40 reanalyses,we studied the seasonal cycle of redistribution of air mass between continents and oceans over the Northern Hemisphere.Our results demonstrate that air mass in the Northern Hemisphere shifts clearly between continents and oceans when the season cycles.In July,the air mass reaches its lowest over Eurasia and its highest over the Pacific,and the opposite occurs in January.However,a different scenario is observed over the north Atlantic;the accumulated air mass reaches its maximum there in May.The maintenance of the accumulation or loss of air mass in a region is found to be related to the areal mean air mass flux divergence and the difference between precipitation and evaporation in an air column.The zonal-vertical circulations change with season,with the air ascent and decent reversed between land and sea.Besides,there also exists a noticeable difference of water vapor content of the air between continents and oceans,and this difference is season-dependent.Physically,the vapor content is able to significantly affect the atmosphere in absorbing solar short-and earth’s long-wave radiations,hence influencing atmospheric thermal conditions.The land-sea thermal contrasts inclusive of the diabatic heating rate changes their signs with season going on,resulting in the reversal of orientations of the temperature gradient.These thermal forcings not only facilitate the formation of the monsoons but also indirectly induce the seasonal cycle of the air mass exchanging over regions between continents and oceans.