上海市浅层地下水环境地球化学背景值研究

文章就文章在简要介绍上海市浅层地下水水文地质条件的基础上,就上海市浅层地下水环境地球化学调查的方法进行了论述。针对浅层地下水环境背景值进行分析,指出本市浅层地下水环境的主要污染类型属综合性有机污染。     

温度对海洋硅藻吸收或释放一氧化氮的影响

基于全球变暖的背景,研究了温度对三角褐指藻(Phaeodactylumtricornutum)、小新月菱形藻(Nitzschiaclosteriumf.minutissima)和中肋骨条藻(Skeletonemacostatum)生长的影响,并初步探讨了温度对海洋硅藻生长过程中吸收或释放一氧化氮(NO)的影响。培养温度分别为20℃和25℃。结果显示,温度升高,中肋骨条藻的比生长速率降低(P0.05),而对三角褐指藻和小新月菱形藻的生长没有明显影响。不同种类硅藻对高温的适应能力不同,且在不同生长阶段对NO呈现不同的吸收或释放规律。与20℃培养条件相比,25℃条件下三角褐指藻对NO的净吸收速率在指数生长期、生长平台期和衰亡期分别升高了40.2%、98.2%和16.0%;小新月菱形藻对NO的净吸收速率在生长的平台期升高了5.7倍;中肋骨条藻对NO的净释放速率在生长的平台期升高幅度最大,为11.5倍。结果表明全球变暖对不同种类的硅藻代谢NO的促进程度不同。     

对流层NO2柱浓度卫星遥感反演综述

NO2是主要的大气痕量气体, 对流层NO2垂直柱密度分布图已经用于诸如污染排放和污染物分布的科学应用研究。就NO2柱浓度的卫星差分光谱吸收反演算法(DOAS)进行了评述, 包括误差分析、验证和发展趋势。对DOAS算法中的主要技术环节进行了详细的阐述, 如ring效应算法、平流层NO2浓度算法和大气质量因子(AMF)问题。论文描述了影响卫星反演NO2浓度, 如云、NO2廓线的先验数据和气溶胶等不确定性因素。针对NO2反演应用需求提出了今后应该加强的内容, 如进一步加强NO2算法研究、发展空气质量探测的静止卫星、重视基于地基多轴被动DOAS和机载平台成像DAOS观测对卫星反演结果的验证。     

Studies of Oxidant Production at the Weybourne Atmospheric Observatory in Summer and Winter Conditions

Detailed studies have been made of the behaviour of gases and radicals involved in the production of oxidants at the Weybourne Atmospheric Observatory in both summertime and wintertime conditions. In June 1995 the range of meteorological conditions experienced varied such that ozone destruction was observed in clean northerly air flows reaching Weybourne down the North Sea from the Arctic, and ozone production was observed in varying degrees in air with different loadings of nitrogen oxides and other precursors. The transition point for ozone destruction to ozone production occurred at a nitric oxide concentration of the order of 50 pptv. Plumes of polluted air from various urban areas in the U.K. were experienced in the June campaign at Weybourne. Quantitative studies of ozone production in a plume from the Birmingham conurbation on 18 June 1995 showed that the measurement of ozone production agreed well with calculated production rates from the product of the nitric oxide and peroxy radical concentrations (r2=0.9). In wintertime conditions (October–November 1994) evidence was also found for oxidant production, defined as the sum of O3+NO2. At this time of year the peroxy radical concentrations (RO2) were much lower than observed in the summertime and the nitric oxide (NO) was much higher. There was still sufficient RO2 during the day, however, for a slow accumulation of oxidant. Confirmatory evidence for this comes from the diurnal co-variance of (O3+NO2) with PAN, an excellent tracer of tropospheric photochemistry. The same type of covariance occurs in summer between PAN and ozone. The results obtained in these series of measurements are pertinent to understanding the measures necessary to control production of regional photochemical air pollution, and to the production of ozone throughout the northern hemisphere in winter.     

An optimized chemiluminescence detector for tropospheric NO measurements

A detector for the chemiluminescent measurement of NO in background air is described. A large reduction of interferences is achieved by using a stabilized ozone generator which allows operation of the instrument at lower O₃ concentrations. Purification and humidification of the O₃ stream further reduces interferences and shortens the instrumental clean-up time, which is important for aircraft missions. From a series of laboratory tests and from measurements performed aboard an aircraft it is demonstrated that the remaining interferences are acceptable for measurements in the undisturbed troposphere. In particular, no remnant NO signal is observed in clean air at night. During flight, a detection limit (2) of 20 ppt is achieved for a 1 min integration time.     

Mixing Ratios and Photostationary State of NO and NO2 Observed During the POPCORN Field Campaign at a Rural Site in Germany

Ambient mixing ratios of NO, NO2, and O3 were determined together with the photolysis frequency of NO2, JNO2, at a rural, agricultural site in Germany. The data were collected during the POPCORN-campaign from August 1 to August 24, 1994, in a maize field 6 m above ground. The medians of the NO, NO2, and O3 mixing ratios between 10:00 and 14:00 UT were 0.25, 1.09, and 45 ppbv, respectively. The corresponding median of JNO2 was 6.0 · 10–3 s–1. NOx = NO + NO2 showed a strong diurnal variation with maximum mixing ratios at night, suggestive of a strong local surface source of NO, probably by microbial activity in the soil. The estimated average emission rate was 40 ng(N) m–2 s–1 of NOx, the major part of it probably in the form of NO. The available measurements allowed the estimation of the local NOx budget. At night the budget is almost closed and the measured NOx mixing ratios can be explained by the local source, local dry deposition of NO2, formation of NO3 and N2O5, and vertical exchange of air across the nocturnal inversion. During day-time, the local surface source of NO is not sufficient to explain the measured mixing ratios, and horizontal advection of NOx to the site must be included. The NO2/NO ratio during the morning und late afternoon is lower than predicted from the photostationary state owing to the local NO surface source, but is regulary higher during the hours around noon. For noon, August 10, 1994, the NO2/NO ratio was used to derive the momentary lower limit for the concentration of the peroxy-radicals of 2.2 · 109 cm–3 (86 pptv).     

强降水天气对南宁市气溶胶主要组分的影响程度

分别对比分析了晴天无云和台风影响出现强降水条件下南宁市气溶胶的变化特征。结果表明：大的降水和大的风速对南宁市气溶胶有较大的清除作用,风速的作用要大于降水的作用;在一定的风速条件下,降水对气溶胶的冲刷作用有限,当降水量达到一定程度之后,降水对气溶胶主要组分的清除作用不再明显;降水和风速对PM10的影响比SO2的明显;晴天条件下,PM10浓度占主要优势,强降水条件下SO2浓度占优势;强降水天气未能屏蔽交通活动对南宁市气溶胶的影响。     

宣城市大气污染与气象分析

用 2003-2005 年宣城市环境保护监测中心PM10、NO2、SO2自动监测资料、宣城市气象台地面观测资料和美国NCEP/NCAR全球日平均再分析资料,分析了宣城市区空气污染浓度、典型大气持续高污染过程形成的气象条件.结果表明,PM10、SO2平均浓度从春季到冬季逐渐增大,NO2平均浓度冬季明显偏小;PM10、NO2、SO2浓度存在准12 d周期变化.典型大气持续高污染过程的环流形势是500 hPa沿海为低槽,槽后为弱冷平流区;地面为宽广的均压区.1000～925 hPa主要为下沉气流;且上层增温明显大于低层,气层稳定度增大,这两种因素均使污染物扩散受阻;1000～700 hPa各层风力微弱,不能将污染物输送至远处,造成污染大气长时间维持.     

A study to explain the emission of nitric oxide from a marsh soil

In the period 18–21 September 1989, soil NO emission was studied at Halvergate Marshes, Norfolk (U.K.) within the framework of the BIATEX-LOVENOX joint field experiment. Using a dynamic chamber technique, 186 measurements at four plots were performed showing a net NO flux of 7.2–14.6×10^–12 kgN m^–2 s^–1. Soil samples from a soil profile (1.0 m) at a representative site and from the uppermost layer (0.1 m) of each of the four plots were sent to the laboratory for (a) detailed physical and chemical soil analysis, (b) determination of NO production rates, NO uptake rate constants, and NO compensation mixing ratios, and (c) characterization of the microbial processes involved. A diffusive model (Galbally and Johansson, 1989) was applied to the laboratory results to infer NO fluxes of the individual soil samples. When we compared these fluxes with those measured in the field, we found agreement within a factor 2–4. Furthermore, laboratory studies showed, that NO was produced and consumed only in the upper soil layer (0–0.1 m depth) and that the NO production and consumption activities observed in the Halvergate marsh soil were most probably due to the anaerobic metabolism of denitrifying bacteria operating in anaerobic microniches within the generally aerobic soil.     

Studying air pollution with kitt peak solar flux atlas — analysis method and results of observation

For the measurement of atmospheric NO2 vertical column density (VCD), Kitt Peak Solar Flux Atlas can be substituted as an extraterrestrial solar radiation. Compared with differential analysis method, the Taylor expansion of integrated transfer equation underestimates the VCD. This underestimation is as large as 35% when the amount of NO2 is 1 × 1017 cm－2 and observation is conducted with an air mass factor of 10. Even when the VCD is 2 × 1016 cm－2 and the air mass factor is 4, the relative error of the retrieved VCD is still no less than 3%. If the observation is restricted under the small air mass factor condition (≤4), with Kitt Peak Solar spectrum as an extraterrestrial solar radiation, only an atmospheric layer of 2 km thick from ground can be studied, which will make the absorption too weak to be detected by normal instruments.The VCD in winter Tokyo area was observed and analyzed by differential method, which shows a good precision even when the absorption is as low as 3%. The largest average VCD was about 1.3 × 1017 cm－2, and the lowest was about 1.3 × 1016 cm－2. The trend of its variation was almost the same as the ground level observation by Saltzman reagent method.