降水空间异质性对非点源关键源区识别面积变化的影响

针对地形起伏和降水空间差异较大的农业区非点源污染问题,基于SWAT模型评估了阿什河流域在异质性降水和均匀降水两种情景下总氮、总磷关键源区空间变化规律,统计了两种情景下识别的关键源区面积变化,并分析其与降水特征参数的关系.结果表明,降水量一定时,两种情景下识别的总氮、总磷关键源区面积变化趋势大致相同,且总磷关键源区面积不易受降水空间异质性的影响,但总氮关键源区面积却明显受到其影响.对各年份总氮和总磷关键源区面积与降水特征参数的相关分析表明,总磷关键源区面积与当年降水量呈显著正相关,而总氮关键源区面积却与前一年降水量呈显著正相关.研究结果对进一步探讨降水这一重要驱动因子的不确定性对非点源污染关键源区的影响,以及农业非点源污染的治理具有重要意义.     

基于静止卫星GOCI传感器的大气污染过程AOD监测

针对北京及周边地区2017年11月2~8日的一次污染过程,利用韩国静止卫星COMs1GOCI数据,对北京地区进行AOD监测.AOD反演采用时间序列迭代算法,根据地表反射率随时间慢变而大气气溶胶随时间快变的理论,采取最小值拟合的方式,获取气溶胶光学厚度数据.反演结果与地基AERONET监测结果具有很好的一致性,两者的相关系数R²大于0.89.AOD监测结果表明,GOCI传感器1次/h的监测频率,可以很好地展现北京地区大气污染过程的开始,发展及消散过程,可以展示出一天之内AOD的变化,为大气污染监测以及气候变化研究提供依据.     

Factors influencing Aerosol Characteristics over Urban Environment

Atmospheric aerosols are an important contributing factor to turbidity in urban areas besides having impact on health. Aerosol characteristics show a high degree of variability in space and time as anthropogenic share of total aerosol loading is quite substantial and is essential to monitor the aerosol features over long time scales. In the present study extensive observations of columnar aerosol optical depth (AOD), total columnar ozone (TCO) and precipitable water content (PWC) have been carried over a tropical urban city of Hyderabad, India. Significant variations of AOD have been observed during course of the day with low values of AOD during morning and evening hours and high values during afternoon hours. Spectral variation of AOD exhibits high AOD at smaller wavelengths and vice versa except a slight enhancement in AOD at 500 nm. Anomalies in AOD, particulate matter and black carbon concentrations have been observed during May, 2003. Back trajectory analysis of air mass during these episodes suggested variation in air mass trajectories. Analysis of the results suggests that air trajectories from land region north of study area cause high loading of atmospheric aerosols. The results are discussed in the paper.     

Sulphate, Nitrogen and Base Cation Budgets at 21 Forested Catchments in Canada, the United States and Europe

To assess the concern over declining base cation levels in forest soils caused by acid deposition, input-output budgets (1990s average) for sulphate (SO₄), inorganic nitrogen (NO₃-N; NH₄-N), calcium (Ca), magnesium (Mg) and potassium (K) were synthesised for 21 forested catchments from 17 regions in Canada, the United States and Europe. Trend analysis was conducted on monthly ion concentrations in deposition and runoff when more than 9 years of data were available (14 regions, 17 sites). Annual average SO₄ deposition during the 1990s ranged between 7.3 and 28.4 kg ha⁻¹ per year, and inorganic nitrogen (N) deposition was between 2.8 and 13.8 kg ha⁻¹ per year, of which 41–67% was nitrate (NO₃-N). Over the period of record, SO₄ concentration in deposition decreased in 13/14 (13 out of 14 total) regions and SO₄ in runoff decreased at 14/17 catchments. In contrast, NO₃-N concentrations in deposition decreased in only 1/14 regions, while NH₄-N concentration patterns varied; increasing at 3/14 regions and decreasing at 2/14 regions. Nitrate concentrations in runoff decreased at 4/17 catchments and increased at only 1 site, whereas runoff levels of NH₄-N increased at 5/17 catchments. Decreasing trends in deposition were also recorded for Ca, Mg, and K at many of the catchments and on an equivalent basis, accounted for up to 131% (median 22%) of the decrease in acid anion deposition. Base cation concentrations in streams generally declined over time, with significant decreases in Ca, Mg and K occurring at 8, 9 and 7 of 17 sites respectively, which accounted for up to 133% (median 48%) of the decrease in acid anion concentration. Sulphate export exceeded input at 18/21 catchments, likely due to dry deposition and/or internal sources. The majority of N in deposition (31–100%; median 94%) was retained in the catchments, although there was a tendency for greater NO₃-N leaching at sites receiving higher (<7 kg ha^-1 per year) bulk inorganic N deposition. Mass balance calculations show that export of Ca and Mg in runoff exceeds input at all 21 catchments, but K export only exceeds input at 16/21 sites. Estimates of base cation weathering were available for 18 sites. When included in the mass balance calculation, Ca, Mg and K exports exceeded inputs at 14, 10 and 2 sites respectively. Annual Ca and Mg losses represent appreciable proportions of the current exchangeable soil Ca and Mg pools, although losses at some of the sites likely occur from weathering reactions beneath the rooting zone and there is considerable uncertainty associated with mineral weathering estimates. Critical loads for sulphur (S) and N, using a critical base cation to aluminium ratio of 10 in soil solution, are currently exceeded at 7 of the 18 sites with base cation weathering estimates. Despite reductions in SO₄ and H⁺ deposition, mass balance estimates indicate that acid deposition continues to acidify soils in many regions with losses of Ca and Mg of primary concern. The U.S. Government's right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. The Canadian Crown reserves the right to retain a non-exclusive, royalty free licence in and to any copyright.     

曲面零件在拉深过程中内皱时刻及影响因素

进一步推导了曲面零件悬空区上的应力分布及临界失稳公式。然后通过计算机编程 ,求解了临界失稳方程 ,得到了拉深系数、相对锥顶半径、相对圆角半径、材料相对厚度与临界失稳时刻间的关系曲线 ,并对曲线变化的规律进行了分析。     

地气溶胶测量──一种寻找隐伏矿床、研究深部构造地质的新方法、新技术

介绍了地气溶胶测量的概念及其测量方法，从地气溶胶组分及元素的赋存状态、来源及其可能的迁移特性，讨论了地气溶胶测量的原理。根据最近几年在矿区外围及未知地区所测量的一些实例，论述了利用该方法寻找隐伏矿床的效果，认为地气溶胶测量在寻找隐伏矿床、研究深部构造地质方面具有广阔的应用和发展前景。     

秦山核电站邻近水域海水光的穿透性能变化研究

本文运用水体可见光的传输机理，讨论了光的传输特性与水中悬浮泥沙，色素和黄色物质的定量关系。同时简述了在秦山核电站邻近海域１９９５年１０月￣１９９６年７月间４个航次的有关水光学特征现场测量过程和实验室分析方法。最后，通过水体中太阳光透透深度和真空层，研究了该邻近海域的光穿透性能的季节性变化。研究表明，核电站运行以来，秦山核电站邻近海域水的光穿透性能变化很小。     

膜生物反应器膜污染的水力学控制实验研究

叙述了膜污染是影响膜-生物反应器处理技术推广应用的关键因素，采用水动力学方法是控制膜污染的有效方法。在不同污泥浓度条件下。对不同曝气强度下膜污染的发展速率及其形成机理进行了试验研究，研究结果表明：对应于不同污泥浓度均存在一个经济曝气强度，其大小随污泥浓度升高呈线性增加，膜生物反应器在经济曝气强度条件下运行可控制膜污染的发展；并从理论上推导出一个临界污泥浓度，其值为5．15g／L。对应于临界污泥浓度，并且污泥絮体在膜面可形成比较稳定的动态膜，膜过滤压差上升的速率最慢，膜生物反应器在此临界污泥浓度条件下运行膜污染发展最为缓慢。     

确定不同保证率下的中国酸沉降临界负荷

在进行中国酸沉降临界负荷区划时 ,通常以 1°× 1°(经纬度 )的网格为单位进行计算 ,难以反映网格内不同生态系统对酸沉降敏感性的差异 .为了便于决策者根据临界负荷确定酸沉降控制对策 ,也为了使 1°× 1°的结果更具代表性和实用性 ,本研究确定了 0 1°× 0 1°网格为单位计算的中国酸沉降临界负荷 ,并在此基础上通过引入保证率的概念 ,得到了一系列与一定的经济技术水平相适应的、允许有一定损失的 1°× 1°的中国酸沉降临界负荷图 .利用累积分布函数 ,本研究还确定了不同保证率下的中国酸沉降超临界负荷分布和各省、市、自治区的酸沉降临界负荷 .     

中国红树林湿地资源及其保护

红树林是我国海岸湿地类型之一，自然分布于海南、广西、广东、福建、台湾等省区。现有面积约1．5万hm^2，包括26种真红树，11种半红树。中国红树林湿地直接经济价值不高，而防浪护岩、维持海岸生物多样性和渔业资源、净化水质、美化环境等生态环境功能显，属于特别容易被价值低估的海岩生态关键区。1960年代以来的毁林转海造田或盐田，毁林围塘养殖，毁林围海搞城市建设等人类不合理开发活动，使红树林面积剧减，环境恶化，红树林湿地资源濒危，急需加强管理和保护。现已建成各级红树林自然保护区18个，还需要吸收科学家积极参与，加强科学研究和宣传教育，以尽快扭转退化趋势，实现红树林湿地生态系统的恢复和可持续发展。