用离子交换树脂柱法观测长春市大气氮沉降

为了解城市环境中大气氮沉降的特点,于2008年9月—2009年9月,使用离子交换树脂柱法对长春市大气氮沉降进行了观测. 结果表明:观测期间,长春市大气硝态氮沉降量月均值为5.33 mg/m2>/sup>,亚硝态氮沉降量月均值为1.67 mg/m2>/sup>. 大气硝态氮和亚硝态氮沉降量有明显的局部分异特点,沉降量大的地点主要分布在交通干线和热电厂周边地区,显示了大气硝态氮的点源和线源特征. 大气氨氮沉降量月均值为3.10 mg/m2>/sup>; 各观测点间大气氨氮沉降量变化明显小于硝态氮和亚硝态氮,显示了大气氨氮的面源特征.      

贵州省六冲关流域大气沉降和地表水化学特征

对比贵州六冲关森林小流域1992─1994年和2001─2005年2个时期穿透水沉降(TF)和地表水的化学组成,以分析大气沉降对森林小流域生物地球化学过程的影响. 结果表明:2001─2004年硫沉降量较1992─1994年有显著下降,但自2005年起硫沉降量又显著增加. 六冲关流域无机氮(尤其是NH₄+-N)沉降量较历史时期显著增加,说明贵阳市大气污染正在由硫酸型向硫酸-硝酸混合型过渡. 长期的大气沉降导致地表水中SO₄2-和NO₃-等阴离子质量浓度的增加,加剧了Ca,Mg和K等营养元素的流失,使地表水的酸中和能力在2002年为负值. 长期观测发现,地表水酸中和能力与穿透水中Ca和Mg的沉降通量密切相关,说明大气沉降已经对六冲关流域的相关生物地球化学过程造成了潜在的影响.      

高镁铝合金在喷射成形过程中显微组织的变化

研究了高镁铝合金在喷射成形过程中显微组织的变化。沉积态高镁铝合金基体呈全部等轴晶组织并存在少量显微孔洞是沉积态组织的主要特征。分析了等轴晶组织和显微孔洞在喷射成形中生成的机制。     

国内外硫磺回收工业发展现状对比与展望

通过对国内外硫磺回收工业发展现状的对比分析，提出了２０００－２０１５年我国硫回收工业的发展战略目标。     

A Coupled Land-Surface and Dry Deposition Model and Comparison to Field Measurements of Surface Heat,Moisture, and Ozone Fluxes

We have developed a coupled land-surface and drydeposition model for realistic treatment of surface fluxes ofheat, moisture, and chemical dry deposition within acomprehensive air quality modelling system. A new land-surfacemodel (LSM) with explicit treatment of soil moisture andevapotranspiration and an indirect soil moisture nudging schemehas been added to a mesoscale meteorology model. The new drydeposition model uses the same aerodynamic and bulk stomatalresistances computed for evapotranspiration in the LSM. Thisprovides consistent land-surface and boundary layer propertiesacross the meteorological and chemical components of the system. The coupled dry deposition model also has the advantage of beingable to respond to changing soil moisture and vegetationconditions. Modelled surface fluxes of sensible and latent heatas well as ozone dry deposition velocities were compared to twofield experiments: a soybean field in Kentucky during summer 1995and a mixed forest in the Adirondacks of New York in July 1998.(on assignment to the National Exposure Research Laboratory, U.S. Environmental Protection Agency) (author for correspondence, e-mail(on assignment to the National Exposure Research Laboratory, U.S. Environmental Protection Agency)     

Effects of Nitrogen Deposition on Bryophyte Species Composition of Calcareous Grasslands

Regular additions of NH₄NO₃ (35–140 kg N ha⁻¹ yr⁻¹) and (NH₄)₂SO₄ (140 kg N ha⁻¹ yr⁻¹) to a calcareous grassland in northern England over a period of 12 years have resulted in a decline in the frequency of the indigenous bryophyte species and the establishment of non-indigenous calcifuge species, with implications for the structure and composition of this calcareous bryophyte community. The lowest NH₄NO₃ additions of 35 kg N ha⁻¹ yr⁻¹ produced significant declines in frequency of Hypnum cupressiforme, Campylium chrysophyllum, and Calliergon cuspidatum. Significant reductions in frequency at higher NH₄NO₃ application rates were recorded for Pseudoscleropodium purum, Ctenidum molluscum, and Dicranum scoparium. The highest NH₄NO₃ and (NH₄)₂SO₄ additions provided conditions conducive for the establishment of two typical calcifuges – Polytrichum spp. and Campylopus introflexus, respectively. Substrate-surface pH measurements showed a dose-related reduction in pH with increasing NH₄NO₃ deposition rates of 1.6 pH units between the control and highest deposition rate, and a further significant fall in pH, of >1 pH unit, between the NH₄NO₃ and (NH₄)₂SO₄ treatments. These results suggest that indigenous bryophyte composition may be at risk from nitrogen deposition rates of 35 kg N ha⁻¹ yr⁻¹ or less. These effects are of particular concern for rare or endangered species of low frequency.     

二氧化硫在潮湿气溶胶表面的氧化速率研究

将稳定同位素方法应用于闽南地区SO₂在潮湿气溶胶表面氧化动力学研究中,在对大气中SO₂的稳定硫同位素及大气气溶胶中可溶性硫的硫稳定同位素丰度的测定的基础上,用硫稳定同位素动力学方程计算SO₂在潮湿气溶胶表面氧化速率与均相氧化速率比?结果表明:漳州地区潮湿气溶胶表面SO₂非均相和均相氧化速率之比:K非/K均为1.13,厦门地区SO₂非均相和均相氧化速率之比:K_非/K_均为0.36,这种差异主要是由相对湿度不同引起的。      

华南地区酸沉降的硫同位素组成及其环境意义

为探讨华南珠江三角洲和湘桂走廊及其周边地区的酸沉降硫源,分别对大气降水、大气SO₂、气溶胶和工业用煤、重油及其燃烧产物进行了硫同位素组成测定.研究结果表明,珠江三角洲和湘桂走廊地区的大气降水硫同位素组成有明显的差异,其大气降水δ³⁴S值的变化范围分别为1.9‰～10.3‰和-4.8‰～-0.1‰.湘桂走廊地区大气降水明显的富集轻硫同位素(32S),而珠江三角洲地区则富集重硫同位素(34S).在煤、重油燃烧过程中硫同位素分馏效应研究基础上,将该地区酸雨硫源区分为4种类型,即人为成因硫、天然生物硫、海雾硫和远距离传输硫.在定量计算不同硫源对酸雨贡献的基础上.提出人为成因硫是珠江三角洲和湘桂走廊地区最强的污染硫源,而生物硫在夏季贡献突出,其贡献率分别为47%和52%.传输硫在冬季贡献率可达49%.上述结果,对研究治理华南地区的酸雨具有重要意义.     

Large-scale mercury variations in Lake Vänern (Sweden) 1974-98

Lake V?nern, the largest lake in Sweden, has been seriously contaminated with mercury during the 20th century. In the 1970's and 80's the direct load, mainly from a chlor-alkali industry in the area, of mercury was drastically reduced as a response to new legislation, from three to five tons down to between five and ten kg yr(-1). Large amounts of the disposed pollutant have accumulated in the sediments. The question posed in this work is now, is the effect of the drastic load reduction after more than two decades visible in the sediments? The question is relevant as large areas still are blacklisted for fishing, but also as a follow-up of a major remedy action. The lake also serves as a freshwater reservoir for even Sweden's second largest city. This work synthesises and compares data of mercury in the sediments from three major field programs, in 1974, 1984 and 1998. The interest is focused on both spatial heterogeneity and temporal trends. In 1974, the surface concentrations are significantly higher than in subsequent surveys. Significant differences are also found between 1984 and 1998. Significant spatial differences within the lake are found for respective year. The most contaminated area is located in the north, close to the major point source (a former chlor-alkali industry). This is also the area with the largest improvement, as a direct response to the reduction in load. Further from the outlet, the recovery is more affected by burial and transport processes out into the deeper basins.