实施《大气污染防治行动计划》对中国东部地区PM2.5化学成分的影响

为应对严重的大气细颗粒物(PM2.5)污染,中国于2013年发布了《大气污染防治行动计划》(以下简称"大气十条"),制定了严格的污染控制措施.大气中PM2.5化学成分的浓度变化与其前体物排放的变化直接相关,因此,分析"大气十条"实施期间中国PM2.5化学成分的时空变化有助于评估控制措施的效果,并可为未来减排政策的制订提供参考.然而目前中国尚未开展PM2.5化学成分的常规监测,对区域尺度PM2.5化学成分的时空变化特征尚不清楚.本研究融合卫星遥感数据和空气质量模型模拟,构建了中国东部地区2013~2017年时空覆盖完整的PM2.5化学成分浓度数据集,并据此分析了中国东部地区大气PM2.5化学成分的时空变化特征.结果表明, 2013~2017年间,中国东部地区PM2.5各种成分的浓度均有所下降,硫酸盐、硝酸盐、铵盐、有机碳、黑碳和其他组分的人口加权平均浓度分别从2013年的11.1、13.8、7.4、9.9、4.6和12.9μg m–3下降至2017年的6.7、13.1、5.8、8.4、3.8和9.6μg m–3.其中硫酸盐的下降幅度最大, 2017年的浓度相较于2013年下降了40%,而硝酸盐下降幅度最小,仅为5%.由此导致PM2.5中硝酸盐比例升高,硫酸盐比例下降.在区域层面,京津冀地区PM2.5及其化学成分的下降幅度最大.硫酸盐浓度的下降幅度与其前体物SO2排放的下降幅度相当,而SO2排放下降主要由工业部门减排主导.硝酸盐浓度的下降幅度较小,这主要是由于大气富氨条件下硫酸盐浓度降低,促进了大气中硝酸向硝酸盐的生成,从而部分抵消了NOx减排带来的成效.为更有效地控制PM2.5污染,未来应加强对氨的减排工作.     

气象条件和排放变化对2020年春节前后华北地区重污染过程的影响

以2020年1~2月华北地区的大气重污染过程为对象,在WRF-CMAQ模型模拟的基础上,分析了气象条件和排放变化对此次重污染过程的影响,并量化分析了为消除PM2.5重度污染,区域主要大气污染物需要进一步减排的力度.研究结果显示,与2015年以来另外两次典型重污染过程相比,京津冀及周边“2+26”城市2020年1~2月期间的重污染过程气象条件最为不利,但由于近年来区域大气污染物排放量大幅削减,且受疫情影响主要大气污染物排放量相比2019~2020年秋冬季基准水平进一步减少了约32%,所以PM2.5峰值浓度明显低于前两次重污染过程.但这样的减排程度还不能满足消除重污染的要求,在给定的区域性严重污染、重污染定义下,“2+26”城市需在2020年1~2月排放的基础上进一步削减20%以上(或相比2019~2020年秋冬季正常排放削减45%左右),才可在同等不利的气象条件下基本消除区域性严重污染,北京不再出现连续3天及以上重污染;进一步削减40%以上(或相比2019~2020年秋冬季正常排放削减60%左右),才可基本消除区域性、连续性重度污染.研究还发现,紧接此次重污染过程后的清洁过程中,大气环境容量大幅增加,污染物排放量增加10倍,才会出现区域性重污染.     

2013~2017年中国重点区域颗粒物质量浓度和化学成分变化趋势

对大气颗粒物浓度及其化学组分精准观测有助于探究大气霾污染的成因与来源解析,评价环境空气质量控制策略的合理性.文章基于CARE-China观测网中中国重点区域典型站点大气PM2.5膜采样和分不同粒径段颗粒物采样及化学成分数据,结合同期中国环境监测总站发布的环境空气质量数据,评估分析了中国2013~2017年《大气污染防治行动计划》实施期间,全国及重点区域大气颗粒物质量浓度的变化及其相应化学组成的演变.研究结果表明:(1)研究期内,中国环境空气颗粒物年平均浓度整体呈明显下降趋势,但仍有64%的城市PM2.5年平均浓度未达到中国现行标准(GB3095-2012).太行山东麓、汾渭平原和新疆乌昌等地区大气PM2.5浓度负荷依然较高,秋冬季重霾污染频发.(2)秋冬季重污染期间,颗粒物中硫酸盐和有机组分质量浓度下降明显.京津冀、珠三角、成渝和汾渭平原地区PM2.5中SO42-平均浓度分别下降了76%、12%、81%和38%;OM平均浓度分别下降70%、44%、48%和31%;NH4+平均浓度分别下降68%、1.6%、38%和25%. EC平均浓度在京津冀和成渝分别下降84%和20%,在珠三角和汾渭平原地区分别上升61%和11%;矿尘及未解析的化学成分(MI)平均浓度在京津冀、珠三角和汾渭平原地区下降了70%、24%和13%. PM2.5中化学成分的变化量,总体上与PM2.5质量浓度的下降量相一致.(3)相比2013年, 2015年京津冀、长三角、珠三角和成渝地区粗颗粒物中OM平均浓度下降46~57%,MI分别下降31~60%和39~73%,是颗粒物浓度下降的最主要因素. 2013~2015年,不同粒径段化学组分中,粗粒径段峰值降低显著,并且随着不同粒径段中颗粒物质量浓度的降低,其SO42-、NO3-和NH4+的细粒径段峰值从0.65~1.1μm转移到更细的0.43~0.65μm粒径段.     

2013~2017年中国PM2.5污染的快速改善及其健康效益

大气细颗粒物(PM2.5)污染对公众健康造成严重危害. 2013年,中国发布了《大气污染防治行动计划》,开始实施严格的污染控制措施,空气质量随之迅速改善.在此背景下,本研究评估了2013~2017年中国地区PM2.5暴露及其健康影响的变化情况.首先结合地面观测数据、卫星遥感数据和大气化学传输模型模拟,构建了2013~2017年中国高时空分辨率PM2.5浓度数据集,基于该数据集评估了PM2.5暴露的时空变化,并结合PM2.5暴露的长期和短期健康效应模型评估了中国PM2.5暴露导致的超额死亡人数的变化情况.研究显示, 2013~2017年间中国人口加权的PM2.5年均浓度从67.4μg m-3降至45.5μg m-3,下降幅度达到32%.在此期间, PM2.5浓度的快速降低使得与PM2.5长期暴露相关的超额死亡人数下降了14%,从2013年的120万人/年(95%置信区间:100, 130;占总死亡人数的13%)降至2017年的100万人/年(95%置信区间:90, 120;占总死亡人数的10%).目前中国大多数地区的PM2.5暴露依然处于较高水平,由于在高浓度区间PM2.5暴露水平下降带来的健康效益改善幅度要小于暴露下降幅度,虽然2013~2017年间PM2.5浓度迅速下降,但带来的健康效益却相对有限.研究还发现由于重污染天数迅速减少,PM2.5急性暴露导致的超额死亡人数在2013~2017年间降低了61%.本研究表明中国的清洁空气政策有效缓解了当前空气污染所导致的健康危害,但未来仍需要继续大幅减少大气污染物排放,以进一步保护公众健康.     

京津冀“治霾路线图”前瞻

"大气十条"要求,"复合型大气污染"严重的京津冀地区要考核PM2.5年均浓度下降程度。2014、2015、2016年度PM2.5年均浓度下降比例须达到核定空气质量改善目标的10%、35%、65%,2017年度终期考核完成核定PM2.5年均浓度下降目标。PM2.5年均浓度与上年相比不降反升的,将以零分计。可谓"一项考核定生死"。这是大气治理的短期目标,那么,生死攸关的大气污染治理到2017年过后又将如何治理呢?6月15日,京津冀及周边地区大气污染联防联控国际研讨会在京召开。讨论通过京津冀区域大气污染治理的"路线图",即《区域大气污染防治中长期规划》将于6月正式启动编制。该规划是我国首个"区域空气质量达标规划"。此外,今年,京津冀及周边地区大气污染治理投入的资金将达59亿元。     

“大气十条”第三年成绩单 亚洲清洁空气中心《大气中国2016:中国大气污染防治进程》详解

正2013年,国务院印发《大气污染防治行动计划》(简称"大气十条"),被称为"史上最严"的大气污染治理计划。"大气十条"共提出了10条35项重点任务措施,并明确要求到2017年,全国地级及以上城市可吸入颗粒物PM10浓度比2012年下降10%以上;京津冀、长三角、珠三角等重点区域细颗粒物PM2.5浓度分别下降25%、20%、15%;其中,北京市PM2.5年均浓度控制在60微克/立方米左右。     

2017治霾战绩榜:几家惊喜 几家尴尬

正《大气污染防治行动计划》(简称"大气十条")于2013年应运而生,提出了治霾的"两个五年计划",还确立了空气污染严重的重点地区大气治理的具体目标值:经过五年努力,全国空气质量总体改善,重污染天气较大幅度减少;京津冀、长三角、珠三角等区域空气质量明显好转;力争再用五年或更长时间,逐步消除重污染天气,全国空气质量明显改善;京津冀、长三角、珠三角等区域细颗粒物浓度分别下降25%、20%、15%左右,     

2013年1月我国中东部强霾污染的数值模拟和防控对策

利用自主研制的嵌套网格空气质量数值预报模式（NAQPMS）模拟研究2013年1月我国中东部的持续强灰霾天气,初步评估灰霾天气下大气细颗粒物（PM2.5）时空分布特征、传输规律和防控力度．结果表明：这一模式能够合理反映灰霾天气下中东部PM2．5,的时空分布特征和演变规律．发现静稳天气京津冀地区仍旧存在显著的区域输送,并直接造成京津冀地区PM2．5浓度的累积,来自区域外的跨城市群输送对京津冀PM2．5浓度贡献为20％-35％,区域内输送的贡献为26％-35％,两者之和与局地污染源贡献相当．针对这次强霾的控制试验表明,当京津冀周边区域省份污染源不控制,河北、天津和北京的污染物排放需要消减90％,90％和60％以上才能实现京津冀区域PM2．5达标（二级标准）,表明京津冀灰霾污染防控不仅需要重视区域内的联防联控,同时也需要其他城市群的协同控制．气象一大气污染双向反馈机制对强霾的形成也有非常重要影响,可使京津冀部分地区细颗粒物月均浓度增加30％,忽视这种耦合作用会导致模式对重污染期间污染物浓度的低估．     

城市冬、夏季大气污染气、粒态复合型相关空间特征

利用2003年冬、夏季北京城市大气环境现场科学试验(BECAPEX,BeijingCityAirPollutionObservationExperiment)综合观测资料,采用点-面结合的研究途径,探讨城市建筑群“冠层”边界观测“点上”与城市区域“面上”大气动力-化学过程时空变化信息,研究观测点大气污染气、粒态的季节性相关结构与转化特征,采用“一维空间EOF”主成分分析模型,分析城市边界层复杂结构背景下气溶胶气、粒态季节变化以及污染物种间关联特征;通过粒子浓度、气体污染物种及其气象条件“主成分”综合分析,揭示城市大气污染气、粒态复杂的组合成分与结构特征的季节变化.以进一步追踪城市区域气溶胶污染面源影响特征及其源影响大气污染成分结构季节差异.研究结果表明:冬、夏季城市大气污染气、粒态时间演变NOx,CO,SO2均呈“同位相”,且与O3呈“反位相”,具有显著“非独立性”特征.总体上,夏季气体污染物CO,SO2,NOx浓度相对于冬季明显偏低,其中CO浓度减少最为明显,其次为SO2和NOx,但夏季O3浓度却高于冬季2倍以上,而冬、夏季PM2.5,PM10粒子浓度季节性差异相对不显著,这一研究结果表明PM10,PM2.5浓度变化对冬、夏季采暖期排放源差异的响应远不如NOx,SO2,CO那样明显.冬、夏季气、粒态相关特征描述出PM10,PM2.5均与NOx有显著的相关性,且此气、粒相关性较其它污染物更为显著.采用主成分分析,发现冬、夏季PM10,PM2.5粒子各污染物种主成分组合结构存在显著差异,冬季PM10,PM2.5粒子主成分结构以SO2,NOx为主,夏季PM10,PM2.5粒子主成分结构则以CO,NOx为主,冬、夏季PM10,PM2.5粒子可能存在此类“非独立”性污染物种的不同“组合”气、粒态相关结构.研究结果还揭示出气、粒态相互影响过程亦与城市边界层垂直结构有关,即城市边界层O3浓度的低值厚度层与大气垂直结构的逆温、逆湿和低空风速低值区“配置”特征相关,其描述了夏季边界层大气特征,即风、温、湿要素的非独立因子“组合”及其配置结构对不同气体污染物浓度变化的复合影响,此类边界层O3异常低值厚度结构与其它气体污染物种的“反位相”关系特征吻合.有关PM10,PM2.5粒子浓度的气象因子主成分分析亦可揭示出PM10,PM2.5浓度变化对局地气象条件“组合”特征的敏感性.     

它比PM2.5更可怕 臭氧连续5个月成最大污染物

<正>10月21日,环保部发布了今年第三季度京津冀、长三角、珠三角区域及74个城市空气质量状况。其中,京津冀区域空气质量达标天数同比明显增加,PM2.5、PM10、二氧化硫等主要污染物浓度同比明显下降,仅臭氧污染略上升。第三季度,74个城市达标天数比例在43.5%~100%之间。超标天数中,以臭氧为首要污染物的天数最多,其次是PM2.5。这是自今年5月以来,臭氧连续第五个月取代PM2.5,成为空气品质超标的"元凶"。臭氧成了最     

Changes in sediment transport in the Kuye River in the Loess Plateau in China

In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January.     

Variations in trace gas concentrations in different environments in India

Observations of trace gases (SO₂, NH₃, NO₂ and O₃) were made during the period 1981 to 1984 at 6 different locations representative of urban industrial, urban, nonurban, thermal power plant and marine environment. Diurnal variations of the trace gases were studied in an urban environment. Except in the urban industrial environment, the concentration of NH₃ was found in the range of background values. Also, the average concentrations of NO₂ and O₃ at the different environments were in the order of background values. However, the concentrations of SO₂ were substantially higher by about 7 times, in urban industrial and thermal power plant environments. The diurnal variations of SO₂, NH₃ and NO₂ showed anitphase relationship with surface temperature at the urban environment station which is relatively free of industrial pollution. Discussion is centred on trace gas variations in different environments in India together with the values reported for various countries in the world.     

TritiogenicHe in groundwater in Takaoka

³He/⁴He ratios up to 3.5 times the ratio of atmospheric He were found in groundwater samples. The³He enrichment can be attributed to radiogenic³He produced by in-situ beta-decay of³H. This shows that tritiogenic³He is accumulating in confined waters. From tritiogenic³He and³H concentrations, ages of groundwaters can be calculated. Detection of tritiogenic³He gives a tool to trace a tritium contamination which occurred in the past and cannot be assessed only by the³H counting method.     

Projected changes in flood indices in selected catchments in Poland in the 21st century

The aim of this study is to estimate likely changes in flood indices under a future climate and to assess the uncertainty in these estimates for selected catchments in Poland. Precipitation and temperature time series from climate simulations from the EURO-CORDEX initiative for the periods 1971–2000, 2021–2050 and 2071–2100 following the RCP4.5 and RCP8.5 emission scenarios have been used to produce hydrological simulations based on the HBV hydrological model. As the climate model outputs for Poland are highly biased, post processing in the form of bias correction was first performed so that the climate time series could be applied in hydrological simulations at a catchment-scale. The results indicate that bias correction significantly improves flow simulations and estimated flood indices based on comparisons with simulations from observed climate data for the control period. The estimated changes in the mean annual flood and in flood quantiles under a future climate indicate a large spread in the estimates both within and between the catchments. An ANOVA analysis was used to assess the relative contributions of the 2 emission scenarios, the 7 climate models and the 4 bias correction methods to the total spread in the projected changes in extreme river flow indices for each catchment. The analysis indicates that the differences between climate models generally make the largest contribution to the spread in the ensemble of the three factors considered. The results for bias corrected data show small differences between the four bias correction methods considered, and, in contrast with the results for uncorrected simulations, project increases in flood indices for most catchments under a future climate.     

Changes in thermal extremes in Poland

Changes in thermal extremes of the climate of Poland in 1951–2010 are examined. Warm extremes have become more frequent, while cold extremes have become less frequent. In the warming climate of Poland, the increase in the number of extremely warm days in a year and the decrease in the number of extremely cold days in a year have been observed. Also the increase of the maximum number of consecutive hot days in a year and the decrease of the maximum number of consecutive very cold and extremely cold days in a year have been observed. However, the trends are not of ubiquitous statistic significance, as the natural variability is strong.     

Copper in natural waters in Transbaikalia

Cu concentrations in surface (river and lake) and subsurface waters are determined. The geographic pattern of Cu distribution in natural water is identified. This pattern is controlled by the difference between its concentrations in drained rocks and soils and the geochemical redox conditions of its migration. Territories with low, medium, and elevated Cu concentrations in natural waters are identified. The concentrations of Cu in natural waters of the region are found to be generally lower than the Clarke values.     

Hydrological changes in the Ganges system in Bangladesh in the post-Farakka period

Abstract

The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly.