Enhanced atmospheric phosphorus deposition in Asia and Europe in the past two decades

磷是植物生长必需的元素,磷缺乏将限制植被生产力及碳汇功能.为厘清全球大气磷沉降的时空格局,本文收集了1959-2020年发表的396条观测资料.结果发现,全球大气磷沉降的几何均值为0.32 kg ha~(-1)yr~(-1),全球大气磷库约4.4 Tg yr~(-1).与1959-2000年相比,近20年亚洲和欧洲大气磷沉降呈现上升趋势,主要来源是农业活动,沙尘传输和燃烧源排放.碳中和背景下,清洁空气行动是否会改变磷沉降的途径和形态,进而影响到生态系统的结构和功能,是需要回答的科学问题.

Revisiting the Concentration Observations and Source Apportionment of Atmospheric Ammonia

While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly,aerosol ammonium nitrate remains high in East China.As the high nitrate abundances are strongly linked with ammonia,reducing ammonia emissions is becoming increasingly important to improve the air quality of China.Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions,long-term surface observation of ammonia concentrations are sparse.In addition,there is still no consensus on whether agricultural or non-agricultural emissions dominate the urban ammonia budget.Identifying the ammonia source by nitrogen isotope helps in designing a mitigation strategy for policymakers,but existing methods have not been well validated.Revisiting the concentration measurements and identifying source apportionment of atmospheric ammonia is thus an essential step towards reducing ammonia emissions.

Optical,Radiative and Chemical Characteristics of Aerosol in Changsha City,Central China

Industrial pollution has a significant effect on aerosol properties in Changsha City,a typical city of central China.Therefore,year-round measurements of aerosol optical,radiative and chemical properties from 2012 to 2014 at an urban site in Changsha were analyzed.During the observation period,the energy structure was continuously optimized,which was characterized by the reduction of coal combustion.The aerosol properties have obvious seasonal variations.The seasonal average aerosol optical depth(AOD)at 500 nm ranged from 0.49 to 1.00,single scattering albedo(SSA)ranged from 0.93 to 0.97,and aerosol radiative forcing at the top of the atmosphere(TOA)ranged from−24.0 to 3.8 W m^−2.The chemical components also showed seasonal variations.Meanwhile,the scattering aerosol,such as organic carbon,SO42−,NO3−,and NH4+showed a decrease,and elemental carbon increased.Compared with observation in winter 2012,AOD and TOA decreased by 0.14 and−1.49 W m^−2 in winter 2014.The scattering components,SO42−,NO3−and NH4+,decreased by 12.8μg m^−3(56.8%),9.2μg m^−3(48.8%)and 6.4μg m^−3(45.2%),respectively.The atmospheric visibility and pollution diffusion conditions improved.The extinction and radiative forcing of aerosol were significantly controlled by the scattering aerosol.The results indicate that Changsha is an industrial city with strong scattering aerosol.The energy structure optimization had a marked effect on controlling pollution,especially in winter(strong scattering aerosol).

Trends in particulate matter and its chemical compositions in China from 2013–2017

Accurate determination of the atmospheric particulate matter mass concentration and chemical composition is helpful in exploring the causes and sources of atmospheric enthalpy pollution and in evaluating the rationality of environmental air quality control strategies.Based on the sampling and chemical composition data of PM2.5 in different key regions of China in the CARE-China observation network,this research analyzes the environmental air quality data released by the China National Environmental Monitoring Centre during the studied period to determine the changes in the particulate matter mass concentration in key regions and the evolution of the corresponding chemical compositions during the implementation of the Action Plan for Prevention and Control of Air Pollution from 2013-2017.The results show the following.(1)The particulate matter mass concentration in China showed a significant downward trend;however,the PM2.5 annual mass concentration in 64%of cities exceeds the New Chinese Ambient Air Quality Standard(CAAQS)GradeⅡ(GB3095-2012).The region to the east of the Taihang Mountains,the Fenhe and Weihe River Plain and the Urumqi-Changji regions in Xinjiang,all have PM2.5 concentration loading that is still high,and heavy haze pollution occurred frequently in the autumn and winter.(2)During the heavy pollution in the autumn and winter,the concentrations of sulfate and organic components decreased significantly.The mean SO42-concentration in PM2.5 decreased by 76%,12%,81%and 38%in Beijing-Tianjin-Hebei(BTH),the Pearl River Delta(PRD),the Sichuan-Chongqing region(SC)and the Fenhe and Weihe River Plain,respectively.The mean organic matter(OM)concentration decreased by 70%,44%,48%and 31%,respectively,and the mean concentration of NH4+decreased by 68%,1.6%,38%and 25%,respectively.The mean elemental carbon(EC)concentration decreased by 84%and 20%in BTH and SC,respectively,and it increased by 61%and 11%in the PRD and Fenhe and Weihe River Plain,respectively.The mean concentration of mineral and unresolved chemical components(MI)dropped by 70%,24%and 13%in BTH,the PRD and the Fenhe and Weihe River Plain,respectively.The change in the PM2.5 chemical composition is consistent with the decrease of the PM2.5mass concentration.(3)In 2015,the mean OM concentration contributions to fine particles and coarse particles were 13-46%and 46-57%,respectively,and the mean MI concentration contributions to fine particles and coarse and particles were 31-60%and 39-73%,respectively;these values are lower than the 2013 values from the key regions,which is the most important factor behind the decrease of the particulate matter mass concentration.From 2013 to 2015,among the chemical components of different particle size fractions,the peak value of the coarse particle size fraction decreased significantly,and the fine particle size fractions of SO42-,NO3-,and NH4+decreased with the decrease of the particulate matter mass concentration in different particle size fractions.The fine-particle size peaks of SO42-,NO3-and NH4+shifted from 0.65-1.1μm to the finer size range of0.43-0.65μm during the same time frame.