大气过氧自由基测量研究进展

过氧自由基是大气中重要的氧化剂 ,其浓度的测定对于深入理解大气化学过程具有重要意义。本文总结了二十多年的研究成果 ,论述了大气过氧自由基测量的研究进展 ,介绍了带基体分离的电子自旋共振技术、远红外及毫米波发射光谱技术、激光诱导荧光技术以及化学放大法等常用测量方法及测量结果 ,并展望其未来的发展。     

米菲司酮废水处理的试验探索

对米菲司酮生产中产生的高浓度有机废水（ＣＯＤｃｒ８．８×１０＾４ｍｇ／Ｌ），采用常压蒸馏－活性炭吸附方法进行试验性处理，ＣＯＤｃｒ的去除率可达９５％以上，ＣＮ－去除率达９９．９％，并可回收乙醇等低沸点有机溶剂。     

南京市城区空气环境质量评估

依据灰色系统理论，采用灰色变权聚类方法，根据国家环境质量标准，对南京市城区近两年的空气质量进行评估。空气质量评估采用的指标包含二氧化硫、二氧化氮以及可吸入颗粒物的浓度，并对评估结果进行了分析和讨论。结果表明，南京市城区空气环境质量呈退化的趋势，尤其是经济繁华的鼓楼区以及交通拥挤的下关区，两年内空气质量明显下降。     

上海地区大气稳定度和气象区块的研究

根据１９８６年６月～１９８７年５月从上海市区４个站、郊县２个站的气象资料,研究了上海地区的大气稳定度和气象区块。采用３种方法确定稳定度的级别,并进行了比较。应用对风向、风速的聚类分析方法划定气象区块。对两站之间风的相关系数用了３种不同的公式进行计算。利用这些相关系数的结果,同时采用“最短距离法”和“最长距离法”,得到相关树枝图,并由此得出了上海地区的气象区块图。     

Monitoring of air pollution by polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans of pine needles in Korea

The atmospheric contamination levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were evaluated from the analysis of pine needles in South Korea. Pine needles were collected from 30 sampling points at five main cities in South Korea (Busan, Daegu, Gwangju, Changwon and Jeju island). The highest concentrations of PCDDs/DFs (2.19–26.88 pg I-TEQ/g of dry weight) were measured at Busan, where is the city of the highest population density and traffic volume among five cities. The lowest concentration was detected at Jeju with 0.62 pg I-TEQ/g dry weight, suggesting Jeju could be an environmental background area in Korea. The dominant homologues of PCDDs/DFs in pine needles were the lower chlorine-substituted compounds such as tetra CDDs and CDFs, and the distribution ratios of PCDDs/DFs decreased with increase of the number of chlorine substituents. Homologue profiles of pine needle samples were similar to PCDDs/DFs profiles of the vapor phase in the ambient air, and thus the pine needles absorbed the vapor phase of PCDDs/DFs from air. Results suggested that pine needles could be used as an indicator of the atmospheric contamination for PCDDs/DFs in Korea.     

Kinetics and mechanism of nitrite oxidation by hypochlorous acid in the aqueous phase

The rate coefficient for the reaction of nitrite with hypochlorite and hypochlorous acid has been studied using spectrophotometric measurements. The reaction rate has been determined in a wide range of H(+) concentration (5< or =-log[H(+)]< or =11). The kinetics were carried out as a function of NO(2)(-), H(+) and total hypochlorite ([HOCl](total)=[HOCl]+[ClO(-)]+[ClNO(2)]) concentrations. The observed overall rate law is described by: -d[HClO](T)dt=[a[NO(2)(-)](2)+b[NO(2)(-)]][H(+)](2)c+d[H(+)]+e[NO(2)(-)][H(+)](2)[HOCl](total)At T=298 K and in Na(2)SO(4) at an ionic strength (I=1.00 M), we obtained using a nonlinear fitting procedure: a=(1.83+/-0.36)x10(7) s(-1), b=(1.14+/-0.23)x10(5) Ms(-1), c=(1.12+/-0.17)x10(-13) M, d=(1.43+/-0.29)x10(-6) M(2) and e=(1.41+/-0.28)x10(3) M where the errors represent 2sigma. According to the overall rate law, a/b=k(1)/k(3), b/e=k(3), c=K(w), d/c=K(a), d=K(a)K(w) and e=K(1)K(a). In Na(2)SO(4) at an ionic strength (I=1.00 M), the values of K(1) and K(a) are (1.1+/-0.1)x10(-4) and 1.28x10(7) M(-1), respectively. A mechanism is proposed for the NO(2)(-) oxidation which involves the reversible initial step: NO(2)(-)+HOCl left harpoon over right harpoon ClNO(2)+OH(-) (K(1)), while ClNO(2) undergoes the two parallel reactions: attack by NO(2)(-) (k(1)) and hydrolysis (k(3)). ClNO(2) and N(2)O(4) are proposed as important intermediates as they control the mechanism. The rate coefficients k(1) and k(3) have been determined at different ionic strengths in NaCl and Na(2)SO(4). The influence of the ionic strength and ionic environment has been studied in this work.     

A new environmental chamber for evaluation of gas-phase chemical mechanisms and secondary aerosol formation

A new state-of-the-art indoor environmental chamber facility for the study of atmospheric processes leading to the formation of ozone and secondary organic aerosol (SOA) has been constructed and characterized. The chamber is designed for atmospheric chemical mechanism evaluation at low reactant concentrations under well-controlled environmental conditions. It consists of two collapsible 90 m³ FEP Teflon film reactors on pressure-controlled moveable frameworks inside a temperature-controlled enclosure flushed with purified air. Solar radiation is simulated with either a 200 kW Argon arc lamp or multiple blacklamps. Results of initial characterization experiments, all carried out at 300–305 K under dry conditions, concerning NO_x and formaldehyde offgasing, radical sources, particle loss rates, and background PM formation are described. Results of initial single organic–NO_x and simplified ambient surrogate–NO_x experiments to demonstrate the utility of the facility for mechanism evaluation under low NO_x conditions are summarized and compared with the predictions of the SAPRC-99 chemical mechanism. Overall, the results of the initial characterization and evaluation indicate that this new environmental chamber can provide high quality mechanism evaluation data for experiments with NO_x levels as low as 2 ppb, though the results indicate some problems with the gas-phase mechanism that need further study. Initial evaluation experiments for SOA formation, also carried out under dry conditions, indicate that the chamber can provide high quality secondary aerosol formation data at relatively low hydrocarbon concentrations.     

Formation of Nitrate and Sulfate in the Plume of Berlin (8 pp)

Background, Aims and Scope Secondary inorganic aerosol (SIA), i.e. particulate sulphate (S(VI)), ammonium and nitrate (N(V)) is formed from gaseous precursors i.e., sulfur dioxide (S(IV)), ammonia and nitrogen oxides, in polluted air on the time-scale of hours to days. Besides particulate ammonium and nitrate, the respective gaseous species ammonia and nitric acid can be formed, too. SIA contributes significantly to elevated levels of respirable particulate matter in urban areas and in strongly anthropogenically influenced air in general. Methods The near-ground aerosol chemical composition was studied at two stationary sites in the vicinity of Berlin during a field campaign in summer 1998. By means of analysis of the wind field, two episodes were identified which allow to study changes within individual air masses during transport i.e., a Lagrangian type of experiment, with one station being upwind and the other downwind of the city. By reference to a passive tracer (Na+) and estimates on dry depositional losses, the influences of dispersion and mixing on concentration changes can be eliminated from the data analysis. Results and Discussion Chemical changes in N(-III), N(V) and S(VI) species were observed. SIA i.e., N(V) and S(VI), was formed from emissions in the city within a few hours. The significance of emissions in the city was furthermore confirmed by missing SIA formation in the case of transport around the city. For the two episodes, SIA formation rates could be derived, albeit not more precise than by an order of magnitude. N(V) formation rates were between 1.4 and 20 and between 1.9 and 59 % h-1 on the two days, respectively, and S(VI) formation rates were > 17 and > 10 % h-1. The area south of the city was identified as a source of ammonia. Conclusion The probability of occurrence of situations during which the downwind site (50 km downwind of Berlin) would be hit by an urban plume is > 7.4%. Furthermore, for the general case of rural areas in Germany it is estimated that for more than half of these there is a significant probability to be hit by an urban plume (> 8%). The S(VI) formation rates are higher than explainable by homogeneous gas-phase chemistry and suggest the involvement of heterogeneous reactions of aerosol particles. Recommendation and Outlook The possible contribution of heterogeneous processes to S(VI) formation should be addressed in laboratory studies. Measurements at more than two sites could improve the potential of Lagrangian field experiments for the quantification of atmospheric chemical transformations, if a second downwind site is chosen in such a way that, at least under particular stability conditions, measurements there are representative for the source area.     

Temporal and spatial relationships in fine particle strong acidity, sulphate, PM1O, and PM2.5 across multiple canadian locations

The Canadian Acid Aerosol Measurement Program (CAAMP) was established in 1992 to gain a better understanding of the atmospheric behaviour of fine particle strong acidity (“acid aerosols”) and to facilitate an assessment of the potential health risks associated with acid aerosols and particles in general. During 1992. 1993 and 1994, annular denuder and filter measurements were taken at four sites in Ontario, two in Quebec, three in the Atlantic Provinces and one in the greater Vancouver area. Mean fine particle sulphate concentrations (SO₄²⁻) were highest in southern Ontario (annual average ranged from 40–70 nmol m⁻³), lowest at a site in the Vancouver area (average = 16 nmol m⁻³) and second lowest in rural Nova Scotia. However, mean fine particle strong acid concentrations (H⁺) were geographically different. The highest mean concentrations were at the east coast sites (annual average of up to 30 nmol m⁻³). Acidities were lower in areas where the fine particle acidity experienced greater neutralization from reaction with ammonia. This included the major urban centres (i.e. Toronto and Montréal) and areas with greater amounts of agricultural activity, as in rural southern Ontario. On average, ambient concentrations of fine and coarse particle mass were larger in the urban areas and also in areas where SO₄²⁻ levels were higher. All the particle components were episodic. However, compared to SO₄²⁻ and fine particles (PM_2.5 or PM_2.1, depending upon inlet design), episodes of H⁺ tended to be less frequent and of shorter duration, particularly in Ontario. Saint John, New Brunswick, had the highest mean annual H⁺ concentration, which was 30 nmol m⁻³. H⁺ episodes (24 h concentration > 100 nmol m⁻³) were also the most frequent at this location. The high levels in Saint John were partially due to local sulphur dioxide sources and heterogeneous chemistry occurring in fog, which, on average, led to a 50% enhancement in sulphate, relative to upwind conditions.There was a substantial amount of intersite correlation in the day to day variations in H⁺, SO₄²⁻ , PM_2.5 and PM₁₀ (fine + coarse particles) concentrations, which is due to the influence of synoptic-scale meteorology and the relatively long atmospheric lifetime of fine particles. Sulphate was the most regionally homogenous species. Pearson correlation coefficients comparing SO₄²⁻ between sites ranged from 0.6 to 0.9, depending on site separation and lag time. In many cases, particle episodes were observed to move across the entire eastern portion of Canada with about a two-day lag between the SO₄²⁻ levels in southern Ontario and in southern Nova Scotia.     

Experimental verification for real-time environmental emergency response system: WSPEEDI by European tracer experiment

Japan Atomic Energy Research Institute has developed an emergency response system WSPEEDI to forecast long-range atmospheric dispersions of radionuclides discharged into the atmosphere. The latest version of WSPEEDI consists of an atmospheric dynamic model MM5 for calculating meteorological fields and a particle random-walk model for atmospheric dispersion. The performance of WSPEEDI was evaluated by data obtained from a field tracer experiment over Europe (ETEX) in this paper. The model validation was done with respect to the following points: (1) the dependence of model accuracy on the temporal and spatial resolutions of the meteorological fields and (2) the superiority of an atmospheric dynamic model over a mass-consistent wind model. Regarding (1), it was shown that the calculation accuracy of the new version with high temporal resolution was improved, especially at the edge of the plume. Moreover, although the increase in horizontal spatial resolution of the old version had no substantial effect on the model performance, increase in horizontal resolution of the new version contributed to the significant improvement of the calculation accuracy. These results showed that the dynamically calculated meteorological field with the spatial resolution of the meso-β–γ scale greatly improved calculation accuracy.