Modelling and mapping long-term risks due to reactive nitrogen effects: an overview of LRTAP convention activities

Long-range transboundary air pollution has caused severe environmental effects in Europe. European air pollution abatement policy, in the framework of the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP Convention) and the European Union Clean Air for Europe (CAFE) programme, has used critical loads and their exceedances by atmospheric deposition to design emission abatement targets and strategies. The LRTAP Convention International Cooperative Programme on Modelling and Mapping Critical Loads and Levels and Air Pollution Effects, Risks and Trends (ICP M&M) generates European critical loads datasets to enable this work. Developing dynamic nitrogen flux models and using them for a prognosis and assessment of nitrogen effects remains a challenge. Further research is needed on links between nitrogen deposition effects, climate change, and biodiversity.     

Critical loads and their exceedances at intensive forest monitoring sites in Europe

Intensive forest monitoring by means of harmonised methods has been conducted in Europe for more than a decade. Risks of atmospheric nitrogen and sulphur deposition are assessed by means of calculations of critical loads and their exceedances. In the present study throughfall and bulk deposition of nitrate (N-NO(3)), ammonium (N-NH(4)) and sulphate (S-SO(4)) show marked spatial patterns and temporal trends. In the period of observation (1999-2004), sulphate deposition on intensive monitoring plots decreased by about one quarter. This is in line with the reduction of S deposition by 70% since 1981 in Europe as a result of successful air pollution control politics under the Convention on Long-range Transboundary Air Pollution (CLRTAP). However, sulphate and especially nitrate and ammonium deposition were found to still exceed critical loads at many forest sites, indicating a continued need for further implementation of air pollution abatement strategies.     

Lichen and bryophyte distribution on oak in London in relation to air pollution and bark acidity

Epiphytic lichen and bryophyte distribution and frequency were investigated on the trunks of 145 young oak trees throughout London and surrounding counties, and compared with pollution levels and bark pH. Sixty-four lichen and four bryophyte species were recorded. Three major zones were identified: (i) two central regions with a few lichens, bryophytes absent; (ii) a surrounding region with a more diverse flora including a high cover of nitrophyte lichens; and (iii) an outer region, characterised by species absent from central London, including acidophytes. Nineteen species were correlated with nitrogen oxides and 16 with bark pH, suggesting that transport-related pollution and bark acidity influence lichen and bryophyte distribution in London today. Lichens and bryophytes are responding to factors that influence human and environmental health in London. Biomonitoring therefore has a practical role to assess the effects of measures to improve London's air quality.     

Deposition of fixed atmospheric nitrogen and foliar nitrogen content of bryophytes and Calluna vulgaris (L.) Hull

Atmospheric deposition of fixed nitrogen as nitrate and ammonium in rain and by dry deposition of nitrogen dioxide, nitric acid and ammonia has increased throughout Europe during the last two decades, from 2-6 kg N ha(-1) year(-1) to 15-60 kg N ha(-1) year(-1). The nitrogen contents of bryophytes and the ericaceous shrub Calluna vulgaris have been measured at a range of sites, with the objective of showing the degree to which nitrogen deposition is reflected in foliar plant nitrogen. Tissue nitrogen concentrations of herbarium bryophyte samples and current samples of the same species collected from the same sites were compared. No significant change in tissue nitrogen was recorded at a remote site in north-west Scotland where nitrogen inputs are small (< 6 kg N ha(-1) year(-1)). Significant increases in tissue N occurred at four sites ranging from 38% in central Scotland to 63% in Cumbria where nitrogen inputs range from 15 to 30 kg N ha(-1) year(-1). The relationships found between the estimated input of atmospheric nitrogen and the tissue nitrogen content of the selected bryophytes and Calluna at the sites investigated were found to be generally linear and fitted the form N(tissue) = 0.62 + 0.022 N(dep) for bryophytes and N(tissue) = 0.83 + 0.045 N(dep) for Calluna. There was thus an increase in total tissue nitrogen of 0.02 mg g(-1) dry weight for bryophytes and 0.045 mg g(-1) dry weight for Calluna for an increase in atmospheric nitrogen deposition of 1 kg ha(-1) year(-1). The lowest concentrations were found in north-west Scotland and the highest in Cumbria and the Breckland heaths of East Anglia, both areas of high atmospheric nitrogen deposition (30-40 kg N ha(-1) year(-1)). The implications of increased tissue nitrogen content in terms of vegetation change are discussed. Changes in atmospheric nitrogen deposition with time were also examined using measured values and values inferred from tissue nitrogen content of mosses. The rate of increase in nitrogen deposition is not linear over the 90-year period, and the increases were negligible over the period 1880-1915. However, during the period 1950 to 1990 the data suggest an increase in nitrogen deposition of 2 kg N ha(-1) every 10 years.     

The relationship between atmospheric pollutant emissions and fuel qualities of inland vessels in Jiangsu Province,China

Air pollution caused by ship exhaust emission is receiving more and more attention. The physical and chemical properties of fuels, such as sulfur content and PAHs content, potentially had a significant influence on air pollutant emissions from inland vessels. In order to investigate the effects of fuel qualities on atmospheric pollutant emissions systematically, a series of experiments was conducted based on the method of actual ship testing. As a result, SO2, PM and NOx emission rates all increased with the increase of main engine rotating speed under cruise mode, while PM and NOx emission factors were inversely proportional to the main engine rotating speed. Moreover, SO2 emission factor changed little with the increase of the main engine rotating speed. In summary, the fuel-dependent specific emission of SO2 was a direct reflection of the sulfur content in fuel. The PM emission increased with the increase of sulfur content and PAHs content in fuel. However, fuel qualities impacted little on NOx emissions from inland vessels because of NOx formation mechanisms and conditions.

Implications: Ship activity is considered to be the third largest source of air pollution in China. In particular, air pollutants emitted from ships in river ports and waterways have a direct impact on regional air quality and pose threat on the health of local residents owing to high pollutants concentration and poor air diffusion. The study on the relationship between air pollutant emissions and fuel quality of inland vessels can provide foundational data for local authority to formulate reasonable and appropriate policies for reducing atmospheric pollution due to inland vessels.     

中国主要湖泊营养氮沉降临界负荷的研究

水体营养氮沉降临界负荷是不致使水体产生富营养化的最高氮沉降量。文中探讨了一种依据湖泊氮质量平衡原理计算营养氮沉降临界负荷的方法。用该方法计算表明 ,我国主要湖泊的营养氮沉降临界负荷比较低 ,大部分小于 1keq· hm- 1 · a- 1 ,部分已为目前的氮沉降量或者两者相当接近 ,意味着只接受氮沉降也能导致这些湖泊产生富营养化。但实际统计结果表明 ,氮沉降在导致受工农业生产和生活影响很大的城市和郊区湖泊的水质富营养化的所有氮污染源中所占比例较低 ,而其它来源的氮输入如河道入湖、工业生活废水和农田径流等才是导致富营养化的最主要因素 ,它们的量已远远超过了这些水体可随最高允许氮负荷。因此 ,对控制这些湖泊的水质富营养化而言 ,控制氮沉降并不是目前最紧迫的任务 ,而其它人为污染源的控制才是最急需的。但氮沉降临界负荷在湖泊富营养化的中长远控制中仍具有十分重要的意义。     

An overview of selected emerging outdoor airborne pollutants and air quality issues: The need to reduce uncertainty about environmental and human impacts

ABSTRACT

According to the literature, it is estimated that outdoor air pollution is responsible for the premature death in a range from 3.7 to 8.9 million persons on an annual basis across the world. Although there is uncertainty on this figure, outdoor air pollution represents one of the greatest global risks to human health. In North America, the rapid evolution of technologies (e.g., nanotechnology, unconventional oil and gas rapid development, higher demand for fertilizers in agriculture) and growing demand for ground, marine and air transportation may result in significant increases of emissions of pollutants that have not been carefully studied so far. As a result, these atmospheric pollutants insufficiently addressed by science in Canada and elsewhere are becoming a growing issue with likely human and environmental impacts in the near future. Here, an emerging pollutant is defined as one that meets the following criteria: 1) potential or demonstrated risk for humans or the environment, 2) absence of Canada-wide national standard, 3) insufficient routine monitoring, 4) yearly emissions greater than one ton in Canada, 5) insufficient data concerning significant sources, fate, and detection limit, and 6) insufficiently addressed by epidemiological studies. A new methodology to rank emerging pollutants is proposed here based on weighting multiple criteria. Some selected emerging issues are also discussed here and include the growing concern of ultrafine or nanoparticles, growing ammonia emissions (due to rapid expansion of the agriculture), increased methane/ethane/propane emissions (due to the expanding hydraulic fracturing in the oil and gas sector) and the growing transportation sector. Finally, the interaction between biological and anthropogenic pollution has been found to be a double threat for public health. Here, a multidisciplinary and critical overview of selected emerging pollutants and related critical issues is presented with a focus in Canada.

Implications: This overview paper provides a selection methodology for emerging pollutants in the atmospheric environment. It also provides a critical discussion of some related issues. The ultimate objective is to inform about the need to 1) address emerging issues through adequate surface monitoring and modeling in order to inform the development of regulations, 2) reduce uncertainties by geographically mapping emerging pollutants (e.g., through data fusion, data assimilation of observations into air quality models) which can improve the scientific support of epidemiological studies and policies. This review also highlights some of the difficulties with the management of these emerging pollutants, and the need for an integrated approach.     

Some aspects of air pollution in Buenos Aires city

This paper presents three aspects of air pollution in the city of Buenos Aires (Argentina). First, we describe the main features of air pollution climatology in the city: the characteristics of wind flow, atmospheric stability and mixing heights. Then, we present the results of the application of DAUMOD and ISCST3 atmospheric dispersion models to calculate spatial and temporal distributions of carbon monoxide and nitrogen oxides background concentrations. Finally, we present the main features of carbon monoxide concentrations observed in a narrow street canyon located downtown.     

Physiological indicators and susceptibility of plants to acidifying atmospheric pollution: a multivariate approach

Plant susceptibility to acidifying atmospheric pollution was investigated for a wide range of plant species under normal environmental conditions. Physiological and biochemical parameters were recorded for each plant species. Multivariate analysis using hierarchical clustering, principal component analysis ordination, as well as regression analysis were used to interpret the data. Analysis of the data separated plants into pioneer tree species, ruderal herbaceous species and climax, slow growing species. Pioneer and ruderal species showed higher potential for foliar nitrate assimilation coupled with higher base cation content and a tendency to a more neutral leaf pH than climax species. Acidic buffering capacities for leaf tissue from pioneer and ruderal species were higher than those of climax species. Nitrate assimilation produces hydroxyl ions, which in conjunction with high base cation content and more neutral leaf pH, provides better metabolic buffering and therefore make pioneer and ruderal species less susceptible to acidifying inputs. Climax species are less able to buffer against acidifying inputs and are subsequently more prone to acidifying air pollution damage.     

重庆主城区大气重污染形势的激光雷达探测与分析

2013年1月12日-26日,利用大气超级站ALS300型激光雷达对重庆主城区大气进行了连续探测,分析了重污染形势期间的大气扩散条件及大气颗粒物时空分布等探测结果。分析表明,大气层结持续稳定,扩散条件差使得大气颗粒物浓度居高不下,大气能见度持续恶化;大气重污染期间PBL高度较低,平均为320～350m;大气颗粒物污染带处于100～400m高度范围;全国范围内异常的大气环流形势和重庆主城区独特的地形、气候特征是造成持续大气重污染形势的原因。     

南京市区植物叶片氮、硫、铅含量与大气污染评价

通过对南京市区的各功能区植物叶片中的氮、硫、铅元素含量的分析，研究了植物大气环境污染指数，探讨了植物叶片的氮、硫、铅元素含量的季节变化，以及与城市大气环境污染之间的关系。结果表明，植物叶片中，硫、铅元素的含量随季节变化不断增加，而氮元素含量相应减少；各功能区的硫、铅元素含量明显高于清洁对照区；用植物污染指数可以综合评价大气环境的质量状况。     

Assessing the Impacts of Long-Range Sulfur and Nitrogen Deposition on Arctic and Sub-Arctic Ecosystems

For more than a decade, anthropogenic sulfur (S) and nitrogen (N) deposition has been identified as a key pollutant in the Arctic. In this study new critical loads of acidity (S and N) were estimated for terrestrial ecosystems north of 60° latitude by applying the Simple Mass Balance (SMB) model using two critical chemical criteria (Al/Bc = 1 and ANC_le = 0). Critical loads were exceeded in large areas of northern Europe and the Norilsk region in western Siberia during the 1990s, with the more stringent criterion (ANC_le = 0) showing the larger area of exceedance. However, modeled deposition estimates indicate that mean concentrations of sulfur oxides and total S deposition within the Arctic almost halved between 1990 and 2000. The modeled exceeded area is much reduced when currently agreed emission reductions are applied, and almost disappears under the implementation of maximum technically feasible reductions by 2020. In northern North America there was no exceedance under any of the deposition scenarios applied. Modeled N deposition was less than 5 kg ha⁻¹ y⁻¹ almost across the entire study area for all scenarios; and therefore empirical critical loads for the eutrophying impact of nitrogen are unlikely to be exceeded. The reduction in critical load exceedances is supported by observed improvements in surface water quality, whereas the observed extensive damage of terrestrial vegetation around the mining and smelter complexes in the area is mainly caused by direct impacts of air pollution and metals.     

Application of back-trajectory techniques to the delimitation of urban clean air zones

Following a request by environmental authorities in New Zealand, atmospheric modelling has been applied to delimitation of clean air zones for urban areas. This approach involved the integration of a kinematic trajectory model with an atmospheric mesoscale model to identify the spatial extent of the catchment of air affecting air pollution concentrations in Christchurch on nights of high air pollution. The Regional Atmospheric Modelling System (RAMS) was configured for the region and idealised simulations performed to obtain predicted wind fields for synoptic situations typical of winter smog events. The predicted surface wind fields on two grids, with horizontal resolutions of 1.5 and 0.5 km, respectively, were then used to derive back-trajectories from the late evening peak of pollution over the central city (around 2200 NZST) to the time at which people tend to first light their domestic fires (around 1800 NZST). The results indicate that although winds are often light, the air tends to travel from a significant distance outside the city boundary over this time period. In particular, cold air typically travels up to 20 km from the Canterbury Plains to the west into the city during these air pollution events, as well as from small valleys in the Port Hills to the south of the city. This research illustrates the significance of upstream sources of air for providing relatively clean air to the city, and acting as buffer zones. It is, therefore, possible to identify the area around the city to which urban air quality is particularly sensitive. This area could either be designated as a buffer zone, or included within the clean air zone of the city. This technique also provides a useful tool for identifying the role of different components of the local wind field responsible for air pollution dispersion and transport in different parts of the area.     

Regional and historical variation in the nitrogen content of Racomitrium lanuginosum in Britain in relation to atmospheric nitrogen deposition

The moss Racomitrium lanuginosum (Hedw.) Brid. is an important component of the drier parts of ombrotrophic mires and montane heaths in north-western Britain. The extent and quality of the montane heaths dominated by R. lanuginosum has declined in recent decades, perhaps in part due to the effects of acidic deposition at high elevations. This paper examines the effect of atmospheric nitrogen deposition, which has increased during this century, on the nitrogen content of R. lanuginosum in Britain. The nitrogen content of the moss reflects the magnitude of the atmospheric supply being least in north-western Scotland and greatest (as much as six-fold greater) near to urban centres in northern England. This regional difference was less marked (only approx. two-fold) during the 19th century (as revealed from the analysis of herbarium specimens) when nitrogen concentrations were appreciably lower. Transplant studies both between regions and between sites within a mountain system demonstrated the importance of atmospheric deposition in determining the tissue nitrogen concentration of the moss. The results are discussed in relation to the potential importance of the enhanced atmospheric nitrogen supply to the normally nitrogen-impoverished montane heaths, and to the growth and persistence of the moss.     

北京空气重污染红色预警期间污染物与气象因子特征

揭示空气重污染红色预警期间污染物与气象因子的变化特征对空气质量预报和污染减排措施评估具有重要参考价值。利用大气污染和气象观测资料,研究了北京2015年11-12月空气重污染红色预警时期污染物浓度、气候特征及气象因子对空气质量影响。结果表明,PM2.5在大气颗粒物中占有较大比重,为首要空气污染物;在重污染峰值时段,城郊PM2.5与PM10比值（R）相差不大,可达0.9以上,空气呈均匀混合的高PM2.5浓度特征,而空气质量较好时城区R值明显高于郊区;研究时段气候特征与历史同期相比有明显差异,其中平均风速偏小19%,平均气温偏高0.23 ℃,气温日较差减小,而多次小型降水增加了空气湿度,导致相对湿度值偏高40%,垂直方向上的逆温层或等温层则加剧了空气重污染的形成和发展,重污染过程中的红色预警措施明显降低了颗粒物浓度;风速与污染物浓度呈指数相关,城郊风速分别低于2.0和2.5 m·s-1时,空气质量较差、污染物浓度随风速升高快速下降,而当城郊风速大于2.0和2.5 m·s-1时变化特征则相反;相对湿度与污染物浓度呈幂相关,相对湿度在65%左右为空气质量特征发生变化的转折点;由于气温日较差存在季节变化,其与空气质量相关关系不太显著。     

Why air quality in the Alps remains a matter of concern. The impact of organic pollutants in the alpine area

In the middle of Europe, the Alps form a geographical and meteorological trap for atmospheric pollutants including volatile and semi-volatile organic compounds emitted in the surrounding lowlands. This is due to their barrier effects, high precipitation rates, and low ambient temperatures. Also the pollutants emitted in the cities inside the Alps spread in the region depending on orographic and meteorological conditions. Although a number of studies on the distribution and effect of pollutants in the Alps has been published, comprehensive information on potential hazards, and ways to improve this sensible environment are lacking. This opinion paper is the result of a discussion during the Winterseminar of the AlpsBioCluster project in Munich. It summarizes the current literature and presents some case studies on local pollution sources in the Alps, and the possibility of using biomonitoring techniques to assess critical pollution loads and distributions.     

上海河流氮负荷的年际变化及其水体富营养化的原因探讨

利用1990-2002年水质监测数据,分析了上海河流水体中氮负荷(总氮和氨氮)的年际变化特征：从整体上来看,上海河流水体氮负荷较大,氮污染严重:苏州河、黄浦江下游河段氮负荷明显高于上游河段,市区河流氮负荷明显高于郊区河流;从年际变化上看,苏州河、黄浦江、市区河流(除龙华港)水体历年氮含量有降低趋势,郊区河流水体历年氮含量有增长趋势。在此基础上,从六个方面讨论了造成上海河流水体富营养化的原因,以期为上海市河流综合整治的规划决策提供重要的科学依据。     

The effect of nitrogen additions on oak foliage and herbivore communities at sites with high and low atmospheric pollution

To evaluate plant and herbivore responses to nitrogen we conducted a fertilization study at a low and high pollution site in the mixed conifer forests surrounding Los Angeles, California. Contrary to expectations, discriminant function analysis of oak herbivore communities showed significant response to N fertilization when atmospheric deposition was high, but not when atmospheric deposition was low. We hypothesize that longer-term fertilization treatments are needed at the low pollution site before foliar N nutrition increases sufficiently to affect herbivore communities. At the high pollution site, fertilization was also associated with increased catkin production and higher densities of a byturid beetle that feeds on the catkins of oak. Leaf nitrogen and nitrate were significantly higher at the high pollution site compared to the low pollution site. Foliar nitrate concentrations were positively correlated with abundance of sucking insects, leafrollers and plutellids in all three years of the study.     

Phenolic compounds content in Pinus halepensis Mill. needles: a bioindicator of air pollution

Foliar phenol concentrations (total and simple phenols) were determined in Aleppo pine (Pinus halepensis Mill.) needles collected in June 2000, from 6 sites affected by various forms of atmospheric pollutants (NO, NO(2), NO(x), O(3) and SO(2)) monitored during two months. Results show an increase in total phenol content with exposure to sulphur dioxide and a reduction with exposure to nitrogen oxide pollution. p-Coumaric acid, syringic acid and 4-hydroxybenzoic acid concentrations increase with exposure to nitrogen oxide pollution, whereas gallic acid and vanillin decrease in the presence respectively of sulphur dioxide and ozone. This in situ work confirms the major interest of using total and simple phenolic compounds of P. halepensis as biological indicators of air quality.     

The atmospheric chemistry of sulphur and nitrogen in power station plumes

Emissions of sulphur and nitrogen compounds from power stations represent a significant fraction of the total emissions of these elements to the atmosphere. Understanding their subsequent chemical reactions in the atmosphere is of fundamental importance as without it, a quantitative assessment of their contribution to local and regional scale air pollution is not possible. Here the atmospheric chemistry of sulphur dioxide and the oxides of nitrogen, and their resultant likely behaviour in the plumes of power stations are reviewed.