A study of polycyclic aromatic hydrocarbons concentrations and source identifications by methods of diagnostic ratio and principal component analysis at Taichung chemical Harbor near Taiwan Strait

Fine (PM(2.5)) and Coarse (PM(2.5-10)) particulates concentrations of ambient air particle-bound polycyclic aromatic hydrocarbons (PAHs) were measured simultaneously from February 2004 to January 2005 at the Taichung Harbor (TH) sampling site near Taiwan of central Taiwan. Particle-bound polycyclic aromatic hydrocarbons (PAHs) were collected on quartz filters, the collected sample used soxhlet analytical method extracted with a dichloromethane (DCM)/n-hexane mixture (50/50, v/v) for 24h, and then the extracts were subjected to gas chromatography-mass spectrometric (GC-MS) analysis. The results indicated that vehicle emissions, coal combustion, incomplete combustion and pyrolysis of fuel and oil burning were the main source of PAHs near Taiwan Strait of central Taiwan. Diagnostic ratio and principal component analysis (PCA) were also used to characterize and identify PAHs emission source in this study.     

Effects of metsulfuron-methyl on the microbial population and enzyme activities in wheat rhizosphere soil

The effects of metsulfuron-methyl, a sulfonylurea herbicide, on the wheat soil microorganisms were evaluated by the methods of microbial inoculation culture, and the activities of three enzymes were measured using the colorimetric method. The tolerant microorganisms that can resist 500 microg x g(-1) metsulfuron-methyl in the counting culture medium were studied specially. Metsulfuron-methyl distinctly inhibited the common aerobic heterotriphic bacteria, but the effects on common fungi and common actinomycete were not evident. In the meantime, the number of tolerant fungi increased greatly in the rhizosphere after the application of metsulfuron-methyl in contrast to the significant decrease of the amount of tolerant actinomycete. It indicates that fungi might turn into the dominant microbial type and actinomycete is the sensitive factor in the soil polluted by sulfonylurea residues. The population of aromatic compounds-decomposing bacteria, aerobic azotobacter, and nitrite bacteria all increased in the earlier period, but the aerobic azotobacter decreased rapidly in number 30 days later, and the amount of nitrite bacteria also showed a temporary decrease with time 15 days later. However, the denitrifying bacteria just began to increase significantly after the crops had grown for 50 days. The amount of sulfur-oxidizing bacteria gradually decreased with the growth of crops, and so were the sulfate-reducing bacteria after metsulfuron-methyl application. To all types of microorganisms, there were more microbes in rhizosphere samples than those in nonrhizosphere except aerobic azotobacter. It means the growth of wheat root system can stimulate the growth of most microorganisms. The activities of hydrogen peroxidase and polyphenol oxidase in soil samples after metsulfuron-methyl application were notably lower than those in the control, and the difference of the activities between the samples of rhizosphere and nonrhizosphere was evident. On the contrary, the activity of dehydrogenase was not inhibited by the application of metsulfuron-methyl, and the rhizosphere effect was not obvious either.     

冰雪灾害中的个体防护问题

2008年1月中旬以来，我国南方一些地区遭受了严重的低温雨雪冰冻灾害，造成上海、江苏、浙江、湖南等20个省、市、自治区不同程度受灾。发生了大面积停电、停运，大批旅客、物资滞留，有的地区甚至停水、缺粮，受灾人数过亿，群众生活困难。据有关报道，截止到2月下旬，全国范围电网因灾害停运电力线共35，710条，停运变电站2，007座。1，662家景区暂时关闭，824家景区受灾。死亡129人，失踪4人。因灾害直接经济损失达1，516．5亿元。面对灾害，全党全军全国人民总动员，开展了大规模的抗灾救灾斗争，并取得了决定性的胜利。认真总结这场突发的自然灾害，就能更好地应对今后可能发生的重大自然灾害和突发事件。同时，我们看到在这场冰雪灾害中也暴露出了一个非常重要的问题．就是个体防护问题。下面，本文就冰雪灾害中个体防护问题，谈几点意见和建议。     

用于生产过程的故障诊断专家系统

讨论了利用人工智能技术来实现生产过程故障检测与诊断的原理。以液位控制系统为例，说明了“基于规则”和“规则架＋ 规则体”两种方法建立专家系统的过程及知识表达的思路     

青海湖地区历史时期以来的气候变化

利用青海湖流域及邻近地区树木年轮资料重建的历史时期气候资料序列，讨论了湖我近六百年来的气候变化，给出了主要冷，暖，湿潮，并对湖区１９５８～１９９５年器测时期的气候变化趋势和气候突变现象作了统计分析，指出了近百年来气候暖干化是造成湖水位下降的主要原因。     

农业病虫害的灾变预测及预报精度分析

在农业病虫害突变规律的研究基础上,建立了定性与定量的尖角突变模型,确定了各病虫的突变区域。根据综合控制变量所确定的边界值,对未来病虫发生发展趋势进行预测。经多年历史资料检验和1992年农业病虫害发生突变的趋势预报证明:准确率高,覆盖面广。     

电工安全技术问答(连载之四)

第四章安全维修 (六十一)母线对地距离要求最低值为多少? 380伏为15毫米;10千伏为125毫米; 3千伏为75毫米;35千伏为290毫米; 6千伏为100毫米;110千伏为800毫米: (六十二)在带电设备附近检修时,施工人员与带电体之间的安全距离要求至少是多少? 3千伏为0.35米; 6～10千伏为0.6米; 35千伏为1.O米; 110千伏为1.5米。 (低压不作规定,可用绝缘挡板)。 (六十三)铜与铝直接连接时,为什么客易发生故障?     

九华山国内客源市场空间结构与出游行为研究

在实地调查的基础上，分析了九华山国内客源市场空间结构及其演变特征，得出国内客源市场集中程度降低、客源吸引力不断增强、波浪式推进的演变结论，并探讨了九华山旅游行为空间模式主要以单一目的地旅游模式和区域旅游模式为主，根据旅游意向调查结果显示，九华山与黄山在客源市场方面具有较强的互补性。     

Long-Term Effects of Fertilization on Soil Organic Carbon Changes in Continuous Corn of Northeast China: RothC Model Simulations

Soil organic C (SOC) content can increase by managing land use practices in which the rates of organic C input exceed those of organic C mineralization. Understanding the changes in SOC content of Black soils (mainly Typic Halpudoll) in northeast China is necessary for sustainable using of soil resources there. We used the RothC model to estimate SOC levels of Black soils under monoculture cropping corn in a long-term fertilization trial at Gongzhuling, Jilin Province, China. The model outputs for the changes in SOC were compared with measured data in this long-term fertilization/manure trial. The sound performance of model in simulating SOC changes suggests that RothC is feasible with Black soils in the temperate climatic region of northeast China. The modeled and measured results indicated that the treatment without fertilizer/farmyard manure (FYM) addition led to a continuous decline in SOC during the study period and N and NPK fertilization were inadequate to maintain the SOC levels in the plow layer (upper 20 cm) unless FYM was added under the current conventional management associated with no above-ground crop residues returning into the soil. Soil organic carbon could follow the same path of decline if the same management practices are maintained. Model results indicate that returning above-ground crop residues to the soil from 2002 to 2022 would increase SOC by 26% for the treatment without fertilization addition, 40% for N treatment, 45% for NPK treatment, and 38% and 46% for N and NPK treatments with FYM addition, compared to the levels in the corresponding treatments in 2002. The simulation results suggest that the RothC model is a feasible tool to assess SOC trend under different management practices, and returning above-ground crop residues into the soil would lead to a remarkable increase in SOC of Black soils in the region.     

Coupled oxidation of aromatic hydrocarbons by horseradish peroxidase and hydrogen peroxide

The oxidation capability of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) coupled oxidation of aromatic hydrocarbons (o-xylene-d10 and naphthalene-d8) was investigated. Batch experiments were conducted using horseradish peroxidase prepared in potassium phosphate buffer in the presence of H2O2. The oxidation of aromatic hydrocarbon was tested as a function of HRP at a fixed concentration of H2O2, and as a function of the concentration of H2O2 at a constant HRP activity (4000 units/ml). The mass removal of o-xylene-d10 and naphthalene-ds increased with increasing HRP enzymatic activity, and up to 54% and 51% of mass removal were observed for o-xylene-d10 and naphthalene-d8, respectively. Increasing the concentration of H2O2 resulted in increased mass removal of aromatic hydrocarbons.