北京大气中NO、NO2和O3浓度变化的相关性分析

臭氧（O₃）是城市污染大气中的首要光化学污染物,其变化规律与氮氧化物(NO_x=NO+NO₂)关系密切.采用49C臭氧分析仪和42CTL氮氧化物分析仪对北京城区O₃和NO_x浓度进行了连续观测,时间为2004-08～2005-07.结果显示,O₃和OX（O₃+NO₂）浓度在午后15:00左右出现峰值,NO_x呈双峰态日变化,在07:00和23:00左右出现峰值.不同季节污染物的浓度变化存在差异,O₃和NO_x浓度分别在夏季和冬季达到最大.NO_x浓度存在100×10^-9(体积分数)的“分界点”,NO_x低浓度时以NO₂为主,NO_x高浓度时NO占大部分.OX区域贡献和局地贡献存在明显的季节变化,前者主要受区域背景O₃的影响,在春季最大,后者主要受局地NO_x光化学反应的制约,在夏季最强,同时OX组分呈现显著的昼夜差异.     

Nocturnal atmospheric chemistry of NO3 and N2O5 over Changzhou in the Yangtze River Delta in China

Comprehensive observations of the nocturnal atmospheric oxidation of NO₃ and N₂O₅ were conducted at a suburban site in Changzhou in the YRD using cavity ring-down spectroscopy (CRDS) from 27 May to 24 June, 2019. High concentrations of NO₃ precursors were observed, and the nocturnal production rate of NO₃ was determined to be 1.7 ± 1.2 ppbv/hr. However, the nighttime NO₃ and N₂O₅ concentrations were relatively low, with maximum values of 17.7 and 304.7 pptv, respectively, illustrating the rapid loss of NO₃ and N₂O₅. It was found that NO₃ dominated the nighttime atmospheric oxidation, accounting for 50.7%, while O₃ and OH only contributed 34.1% and 15.2%, respectively. For the reactions of NO₃ with volatile organic compounds (VOCs), styrene was found to account for 60.3%, highlighting its dominant role in the NO₃ reactivity. In general, the contributions of the reactions between NO₃ and VOCs and the N₂O₅ uptake to NO₃ loss were found to be about 39.5% and 60.5%, respectively, indicating that N₂O₅ uptake also played an important role in the loss of NO₃ and N₂O₅, especially under the high humidity conditions in China. The formation of nitrate at night mainly originated from N₂O₅ uptake, and the maximum production rate of NO₃⁻ reached 6.5 ppbv/hr. The average NO_x consumption rate via NO₃ and N₂O₅ chemistry was found to be 0.4 ppbv/h, accounting for 47.9% of the total NO_x removal. The predominant roles of NO₃ and N₂O₅ in nitrate formation and NOx removal in the YRD region was highlighted in this study.     

铜川市秋冬季大气VOCs特征及其O3和SOA形成潜势分析

VOCs是O₃和SOA形成的重要前体物,可增强大气氧化性,促进二次污染物形成,影响区域空气质量和人体健康.为研究铜川市秋冬季VOCs特征及其对O₃和SOA生成的潜力,利用TH-300B在线监测系统监测了铜川市区102种VOCs的体积分数,并结合最大增量反应活性系数法和气溶胶生成系数法分别计算VOCs的O₃及SOA生成潜力.结果表明,铜川市秋季和冬季φ（TVOC）分别为（50.52±16.81）×10^-9和（63.21±35.24）×10^-9,O₃生成潜势分别为138.43×10^-9和137.123×10^-9, SOA生成潜势分别为3.098μg·m^-3和0.612μg·m^-3.秋季VOCs中含量最多的2种组分为烷烃（26.19%）和芳香烃（26.04%）,冬季VOCs中含量最多的组分为烷烃（48.88%）.反-2-戊烯、甲苯和间/对-二甲苯是秋季OFPs最大的3个成分,...     

上甸子区域背景站VOCs污染特征及其对臭氧生成贡献

大气中的挥发性有机物(volatile organic compounds,VOCs)作为对流层臭氧和二次有机气溶胶的前体物,在光化学反应和细颗粒物污染中发挥着重要的作用.本研究于2017年9月1～27日在上甸子区域背景站开展VOCs的连续在线观测,对VOCs的浓度水平,时空变化特征,化学反应活性及其对臭氧生成的贡献进行了研究,并运用特征物种比值法对初始VOCs的来源进行了分析.结果表明, 2017年9月上甸子站总VOCs平均体积分数为12.53×10^-9,其中,烷烃是体积分数最大的组分,占到了总VOCs的65.3%,其次是烯烃和芳香烃,分别占到了总VOCs的26.7%和6.5%.从大气化学活性来看,上甸子站总的L^·OH(·OH损耗率)为5.2 s^-1,其中C4～C5烯烃占到了61%,其次是C2～C3烯烃,占到了12.8%.VOCs的臭氧生成潜势平均值为36.5×10^-9,烯烃是贡献最大的组分,占到了71.2%.烯烃中又以C4～C5烯烃的贡献最为突出,而体积分数较大的烷烃对臭氧生成的贡献却不大.对特...     

中国能源金三角NO2时空格局及其驱动因子

利用臭氧监测仪(OMI)提供的大气污染监测数据,结合产业结构、汽车保有量、国家政策措施等,通过城乡NO₂浓度差异的排放源分析方法提取能源金三角(EGT)地区2005~2019年对流层NO₂垂直柱浓度时空变化特征并探讨影响区域大气NO₂浓度驱动因素.结果表明,EGT煤炭化工源NO₂浓度与第二产业产值增速的相关系数为0.71(P<0.05),说明本文方法所提取的长时序煤炭化工源NO₂浓度能有效地指示产业结构调整和政策措施变化.NO₂浓度从2005~2011年的90.56molc/m²增加至2012~2015年的720.77molc/m²,再下降至2016~2019年的247.36molc/m²,反映EGT经济发展模式经历了从小规模、中污染的点模式逐步发展成大范围、重污染的粗放模式,再到大范围、低污染的精工模式.与京津冀、华中、长三角等地区相比,EGT交通和工业排放对城市源NO₂污染贡献的变化特征进一步反映城镇化水平的发展和产业结构的优化.与OMI相比,高分辨率对流层观测仪(TROPOMI)能在短时序上提供丰富的影像细节信息,且随着观测时长的增加,有望增强长时序大气NO₂污染的精准监测.     

Observations of N2O5 and NO3 at a suburban environment in Yangtze river delta in China: Estimating heterogeneous N2O5 uptake coefficients

The nitrate radical(NO₃) and dinitrogen pentoxide(N_2.5) play an important role in the nocturnal atmosphere chemistry.Observations of N03 radicals and N₂ O₅ were performed in a semirural ground site at Tai’Zhou in polluted southern China using cavity ring down spectroscopy(CRDS) from 23 May to 15 June 2018.The observed N03 and N₂ O₅ concentrations were relatively low,with 1 min average value of 4.4±2.2 and 26.0±35.7 pptV,respective...     

Emissions of SO2, NO and N2O in a circulating fluidized bed combustor during co-firing coal and biomass

This paper presents the experimental investigations of the emissions of SO2, NO and N2O in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The influence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N2O were proposed.     

长株潭城市群PM2.5和O3浓度时空分布特征及影响因素分析

基于2015~2019年长株潭城市群PM_2.5和O₃遥感浓度数据,利用空间自相关指数和地理加权回归（GWR）等方法探究PM_2.5和O₃浓度的时空分布特征及相关因素对其影响强度.结果表明：① PM_2.5浓度整体呈现出冬季和春季高,夏季和秋季低的"U"型特征,而O₃浓度则表现为夏季和秋季高,冬季和春季低的"M"型特征,PM_2.5与O₃年均浓度高低排序为：长沙市>湘潭市>株洲市.② PM_2.5与O₃浓度在夏季呈现正相关,秋冬季为负相关,且具有显著的空间集聚特征,O₃浓度高-高集聚区的面积呈现逐年增加的趋势.③GWR结果显示：夜间灯光强度和人口密度都对PM_2.5与O₃具有正相关效应,其中,植被指数（NDVI）、风速和温度对PM_2.5浓度的影响最为显著,而风速和温度对O₃影响强度更为突出,不同因素对PM_2.5和O₃浓度影响具有显著的空间异质性.     

主体功能区视角下的环境污染时空格局及驱动因素——基于广东省121个县域的实证分析

基于县域污染物排放和人口社会经济数据库,运用熵权法构建水气污染综合指数测度广东省水气环境污染状况,在解析2012—2016年水气环境污染时空变化与主体功能区分异特征的基础上,采用空间计量模型考察水气环境污染的驱动因素及其在不同类型主体功能区之间的差异.研究结果表明：① 2012—2016年,广东省水气污染综合指数降幅达到46.93%,处于污染指数高值区间的县域数量大幅减少,并呈现由边缘向核心收缩的空间变化特征;② 4类主体功能区的水气环境污染均有明显改善,但相对而言,城市化地区和农产品主产区仍是广东省水气污染物排放的主要承压区;③人口规模是各类主体功能区水气环境污染的共性驱动因素,此外,城市化地区、农产品主产区和重点生态功能区还分别受到工业化水平、社会固定资产投资和财政收入分权程度的影响.建议从引导城乡居民绿色生活、持续提升清洁生产技术、增加地方财政分权激励机制中的环境效益考核入手强化区域环境污染综合治理.     

Vertical and temporal distribution of nitrogen and phosphorus and relationship with their influencing factors in aquatic-terrestrial ecotone： a case study in Taihu Lake, China

Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone （ATE） of Taihu Lake were investigated, and the relations among N, P, ORP （oxidation reduction potential）, TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3^--N, DON （dissolved organic nitrogen） and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4^＋-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3^--N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3^--N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation ofTN, TP, NO3^--N, NH4^＋-N and DON is significant, of which the variation coefficient of NO3^--N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment.