丽水市大气环境中的城市干、湿岛效应初探

利用丽水城区中心及其近郊2个站点的逐时水汽压资料,定义了干(湿)岛强度指数及干(湿)岛强度等级,并发现了丽水小城区干(湿)岛变化强度、频次及时空分布规律,研究发现城区中心的干岛现象与热岛现象之间存在着正相关.湿岛的形成与露、雾、结冰、霜、雨等天气现象有关.     

CO2 transportation for carbon capture and storage: Sublimation of carbon dioxide from a dry ice bank

Climate change is being caused by greenhouse gases such as carbon dioxide (CO₂). Carbon capture and storage (CCS) is of interest to the scientific community as one way of achieving significant global reductions of atmospheric CO₂ emissions in the medium term. CO₂ would be captured from large stationary sources such as power plants and transported via pipelines under high pressure conditions to underground storage. If a downward leakage from a surface transportation system module occurs, the CO₂ would undergo a large temperature reduction and form a bank of “dry ice” on the ground surface; the sublimation of the gas from this bank represents an area source term for subsequent atmospheric dispersion, with an emission rate dependent on the energy balance at the bank surface. Gaseous CO₂ is denser than air and tends to remain close to the surface; it is an asphyxiant, a cerebral vasodilator and at high concentrations causes rapid circulatory insufficiency leading to coma and death. Hence a subliming bank of dry ice represents safety hazard. A model is presented for evaluating the energy balance and sublimation rate at the surface of a solid frozen CO₂ bank under different environmental conditions. The results suggest that subliming gas behaves as a proper dense gas (i.e. it remains close to the ground surface) only for low ambient wind speeds.     

重庆地区大气干降尘化学组分及其在中和降雨酸度中的作用

用直径50cm 的聚乙烯漏斗,在冬夏两季分别截获了白天和夜间的干降尘。结果表明,干降尘中主要阳离子是钙,虽然它吸附二氧化硫,但不酸。计算表明城区干降尘能中和降水中11.8％的酸,四面山中和6.2％。     

Suppression effects of powder suppressants on the explosions of oxyhydrogen gas

Suppression tests of oxyhydrogen gas explosions were performed in an explosion tube with five types of dry powder used as the suppressants. The experimental results showed that the powder with large dust cloud density and small radius has better suppression effect, which agrees well with previous correlative results. Moreover, our results also showed that particles with chemical activity and light material density, their suppression effect are more prominent than that of the inert particles with heavy density. To discover the detailed suppression process of dust powder, governing equations were developed based on the homogeneous reactive two-phase flow. The TVD scheme and the Lax–Wendroff–Rubin scheme were adopted to solve the reactive gas phase and particle phase, respectively. The time splitting technique was employed to handle the stiffness of the coupled equations. Our calculated results showed that the dust cloud has the suppression effect on the explosion of oxyhydrogen gas, and with the increase of dust cloud density or the decrease of particle diameter, its suppression effect become more evident, which is in good agreement with our experimental results, in addition, the numerical results showed that with the same particle diameter, the suppression performance is enhanced with the reduction in particle material density.     

分流制泵站旱流放江对受纳河道水质的影响

为了探明分流制泵站旱流放江对受纳河道的影响,以上海市中心城区典型分流制系统Z泵站为例,研究了旱流放江对受纳河道水质的影响。结果显示:（1）受泵站放江的影响,河道COD、硫化物以及氨氮的增幅分别为0.23%～37.68%、7.4%～76.19%、10.60%～76.15%;（2）旱流放江污染物对河道水质的影响有显著差异,其中COD与氨氮浓度的下降主要源于水体的稀释扩散作用;而H₂S、FeS等硫化物浓度的降低则更多的受到氧化还原反应的影响;（3）Z泵站旱流放江对Z河水质的显著影响范围为泵站排放口上下游40 m范围内,对黄浦江水质的影响则总体不大。     

岷江干旱河谷甜樱桃发展优势及栽培技术研究

岷江上游干旱河谷特有的生态环境条件适宜发展优质特色水果.甜樱桃作为该区域新兴特色水果之一,近5年来发展面积已超过了400hm2.甜樱桃的引种和规模化栽培表明,岷江上游干旱河谷区发展优质、高产甜樱桃具有独特的优势.总结了岷江干旱河谷栽培甜樱桃的成熟技术和管理措施,探讨了发展甜樱桃的巨大潜力,同时对存在的问题进行了分析,以期为汶川地震灾害农业产业的恢复重建和结构调整提出新的思路.     

Contribution of atmospheric nitrogen deposition to diffuse pollution in a typical hilly red soil catchment in southern China

Atmospheric nitrogen （hi） deposition is currently high and meanwhile diffuse N pollution is also serious in China. The correlation between N deposition and riverine N export and the contribution of N deposition to riverine N export were investigated in a typical hilly red soil catchment in southern China over a two-year period. N deposition was as high as 26.1 to 55.8 kg N/（ha-yr） across different land uses in the studied catchment, while the riverine N exports ranged from 7.2 to 9.6 kg N/（ha-yr） in the forest sub-catchment and 27.4 to 30.3 kg N/（ha.yr） in the agricultural sub-catchment. The correlations between both wet N deposition and riverine N export and precipitation were highly positive, and so were the correlations between NH-N or NO2-N wet deposition and riverine NH4-N or NO3-N exports except for NH-N in the agricultural sub-catchment, indicating that N deposition contributed to riverine N export. The monthly export coefficients of atmospheric deposited N from land to river in the forest sub-catchment （with a mean of 14%） presented a significant positive correlation With precipitation, while the monthly contributions of atmospheric deposition to riverine N export （with a mean of 18.7% in the agricultural sub-catchment and a mean of 21.0% in the whole catchment） were significantly and negatively correlated with precipitation. The relatively high contribution of N deposition to diffuse N pollution in the catchment suggests that efforts should be done to control anthropogenic reactive N emissions to the atmosphere in hilly red soil regions in southern China.     

Size and elemental composition of dry-deposited particles during a severe dust storm at a coastal site of Eastern China

Dry-deposited particles were collected during the passage of an extremely strong dust storm in March, 2010 at a coastal site in Qingdao(36.15°N, 120.49°E), a city located in Eastern China. The size, morphology, and elemental composition of the particles were quantified with a scanning electron microscope equipped with an energy dispersive X-ray instrument(SEM–EDX). The particles appeared in various shapes, and their size mainly varied from 0.4to 10 μm, with the mean diameters of 0.5, 1.5, and 1.0 μm before, during, and after the dust storm, respectively. The critical size of the mineral particles settling on the surface in the current case was about 0.3–0.4 μm before the dust storm and about 0.5–0.7 μm during the dust storm. Particles that appeared in high concentration but were smaller than the critical size deposited onto the surface at a small number flux. The elements Al, Si and Mg were frequently detected in all samples, indicating the dominance of mineral particles. The frequency of Al in particles collected before the dust storm was significantly lower than for those collected during and after the dust storm. The frequencies of Cl and Fe did not show obvious changes, while those of S, K and Ca decreased after the dust arrival. These results indicate that the dust particles deposited onto the surface were less influenced by anthropogenic pollutants in terms of particle number.