Atmospheric nitrogen deposition in south-east Scotland: Quantification of the organic nitrogen fraction in wet,dry and bulk deposition

Water soluble organic nitrogen (WSON) compounds are ubiquitous in precipitation and in the planetary boundary layer, and therefore are a potential source of bioavailable reactive nitrogen. This paper examines weekly rain data over a period of 22 months from June 2005 to March 2007 collected in 2 types of rain collector (bulk deposition and “dry + wet” deposition) located in a semi-rural area 15 km southwest of Edinburgh, UK (N55°51′44″, W3°12′19″). Bulk deposition collectors are denoted in this paper as “standard rain gauges”, and they are the design used in the UK national network for monitoring precipitation composition. “Dry + wet” deposition collectors are flushing rain gauges and they are equipped with a rain detector (conductivity array), a spray nozzle, a 2-way valve and two independent bottles to collect funnel washings (dry deposition) and true wet deposition. On average, for the 27 weekly samples with 3 valid replicates for the 2 types of collectors, dissolved organic nitrogen (DON) represented 23% of the total dissolved nitrogen (TDN) in bulk deposition. Dry deposition of particles and gas on the funnel surface, rather than rain, contributed over half of all N-containing species (inorganic and organic). Some discrepancies were found between bulk rain gauges and flushing rain gauges, for deposition of both TDN and DON, suggesting biological conversion and loss of inorganic N in the flushing samplers.     

How and why is Aquatic Quality Changing at Nahanni National Park Reserve, nwt, Canada?

Nahanni National Park Reserve is located at southwestern NWT-Yukon border. One of the first UNESCO World Heritage sites, Nahanni lies within Taiga Cordillera and Taiga Shield Ecozones. Base and precious metal mining occurred upstream of Nahanni prior to park establishment. Nahanni waters, sediments, fish, and caribou have naturally elevated metals levels. Baseline water, sediment and fish tissue quality data were collected and analyzed throughout Nahanni during 1988–91 and 1992–97. These two programs characterized how aquatic quality variables are naturally varying in space and time, affected by geology, stream flow, seasonality, and extreme meteorological and geological events. Possible anthropogenic causes of aquatic quality change were examined. Measured values were compared to existing Guidelines and site-specific objectives were established.     

A Global Overview of Atmospheric Acid Deposition Fluxes

This paper presents a summary of globalacid deposition flux data taken from a globalassessment report on acid deposition prepared forUNEP/WMO (Whelpdale and Kaiser, 1996). There is a largevariation in the spacial coverage and reliability ofmonitoring around the world. Many more stationsmeasure wet deposition than collect appropriate datafor estimating dry deposition. The widespread regionswith highest precipitation concentrations anddeposition fluxes of sulphate and nitrate coincideclosely with the regions of highest density ofSO₂ and NO_x precursor emissions occurringprimarily in the mid-latitude, northern hemispherebelt where a large fraction of the worlds fossilfuels is consumed. Organic acids in precipitation makea minor contribution to acidity (<20%) inindustrial regions, but in the rest of the world theyare of same order, or even exceed, inorganic acids.Less is known about dry deposition, but it appears topredominate near strong emission sources with wetdeposition predominating farther downwind. The molarratio of the N/S contribution to acidic deposition isclose to 1.0 over large areas of Europe and NorthAmerica, but is highly variable elsewhere, beinghighest in equatorial regions due to biomass burningand lowest near smelters and other large sources of SO₂.     

成都冬季一次持续污染过程气象成因及气溶胶垂直结构和演变特征

基于气溶胶激光雷达观测和环境监测站污染物浓度数据、气象观测资料及HYSPLIT后向轨迹模式,分析了2017年12月中下旬,成都市一次本地积累和沙尘输送影响的持续污染过程中污染物浓度、污染物来源、天气系统和气溶胶消光系数的垂直分布及演变.结果表明：①此次污染过程持续时间长,根据气象条件和主要污染物种类,分为本地污染累积、北方沙尘输送和混合影响3个阶段.②本地污染积累阶段,消光系数垂直分布不均匀,受湿度、太阳辐照与逆温层等气象因子的影响,垂直结构变化较大.消光系数最大值多出现在250 m附近,此阶段退偏比数值很小.③沙尘影响阶段,消光系数较前期明显下降,高值区位于250 m及2 km处.退偏比显示沙尘粒子于29日午后开始逐渐抵达成都市2 km高空,并于夜间达到峰值.退偏比相较本地污染累积阶段明显增大,各时段退偏比结构类似,近地面数值略低于高空.④混合影响阶段,消光系数强度小幅回升,退偏比显示有部分沙尘粒子漂浮在1~2 km高度上.     

A five-year climatology of back-trajectories from the Izaña baseline station,Tenerife, Canary Islands

As a contribution to the climatological characterization of the Izaña baseline observatory (Tenerife, Canary Islands, Spain), back-trajectories were calculated and an air mass climatology was developed for a 5-year period. On a daily basis, 5-day back-trajectories were computed for the 850- and 700-HPa levels from January 1983 to December 1987. Trajectories were separated into long- and short-range flows and classified into categories depending on the path followed by the air masses. Flows from the North Atlantic Ocean were much more frequent than flows from continental sectors. In addition, seasonal variations of the sector frequencies were studied and synoptic meteorological patterns were associated with each trajectory category.     

威海市夏季臭氧及大气氧化性特征分析

威海市属于我国北方典型沿海城市,近年来的持续观测发现夏季易出现臭氧(O3)污染.以2023年夏季观测数据为约束,利用零维盒子模式分析威海市夏季O3及大气氧化性特征,给出O3污染防治的建议.2023年5月30日-6月30日,威海市污染天的首要污染物是O3,烷烃是挥发性有机物(VOCs)中浓度占比最高的组分,烯烃则是活性占比最高的组分.从清洁日到污染日烯烃活性增强最显著,O3的化学生成和大气氧化性在污染日均有增加,促进了二次污染过程的发生.威海夏季大气氧化性水平较强,O3对前体物的敏感区处于氮氧化物(NOx)和VOCs的过渡区,O3污染防控需结合NOx和VOCs进行协同防控.O3对前体物烯烃减排的变化最敏感,因此其污染防控过程需结合VOCs反应活性开展.基于威海市夏季观测数据分析O3及大气氧化性特征,从O3敏感性区域变化及VOCs反应活性角度为O3污染防治策略提供了思路.     

Development and application of a three-dimensional aerosol chemical transport model,PMCAMx

A three-dimensional chemical transport model (PMCAMx) is used to simulate PM mass and composition in the eastern United States for a July 2001 pollution episode. The performance of the model in this region is evaluated, taking advantage of the highly time and size-resolved PM and gas-phase data collected during the Pittsburgh Air Quality Study (PAQS). PMCAMx uses the framework of CAMx and detailed aerosol modules to simulate inorganic aerosol growth, aqueous-phase chemistry, secondary organic aerosol formation, nucleation, and coagulation. The model predictions are compared to hourly measurements of PM_2.5 mass and composition at Pittsburgh, as well as to measurements from the AIRS and IMPROVE networks. The performance of the model for the major PM_2.5 components (sulfate, ammonium, and organic carbon) is encouraging (fractional errors are in general smaller than 50%). Additional improvements are possible if the rainfall measurements are used instead of the meteorological model predictions. The modest errors in ammonium predictions and the lack of bias for the total (gas and particulate) ammonium suggest that the improved ammonia inventory used is reasonable. The significant errors in aerosol nitrate predictions are mainly due to difficulties in simulating the nighttime formation of nitric acid. The concentrations of elemental carbon (EC) in the urban areas are significantly overpredicted. This is a problem related to both the emission inventory but also the different EC measurement methods that have been used in the two measurement networks (AIRS and IMPROVE) and the actual development of the inventory. While the ability of the model to reproduce OC levels is encouraging, additional work is necessary to confirm that that this is due to the right reasons and not offsetting errors in the primary emissions and the secondary formation. The model performance against the semi-continuous measurements in Pittsburgh appears to be quite similar to its performance against daily average measurements in a wide range of stations across the Eastern US. This suggests that the skill of the model to reproduce the diurnal variability of PM_2.5 and its major components is as good as its ability to reproduce the daily average values and also the significant value of high temporal resolution measurements for model evaluation.     

城市近地层气态污染物的垂直分布特征

为研究大气污染物在近地层内的垂直分布规律,2009年2月10-25日利用被动采样器在北京325 m气象铁塔10个高度（8、15、47、80、120、160、200、240、280、320 m）对SO2、NO2、O3、NH3和苯系物（苯benzene、甲苯toluene、乙苯ethylbenzene和二甲苯xylene）共8种大气污染物浓度进行了同步观测.结果表明,北京城区冬季污染物浓度具有明显的垂直变化特征,污染物浓度从近地面开始逐渐上升,在80-160 m以内的某一高度到达峰值后逐渐下降;200-300 m范围内,大气污染物浓度的垂直变化幅度相对较小,浓度值与地面接近;200 m以下各种污染物浓度的变化比较剧烈,浓度极大值出现的高度有所不同,O3、SO2和NH3极大值位于160 m,苯和NO2极大值出现在120 m,甲苯、乙苯和二甲苯极大值在80 m处.污染物在不同高度富集可能与污染源排放高度、城市冠层的热动力作用和气象因素有关,区分这些因素的各自贡献尚需进一步研究.