大气边界层中起尘、降尘过程的模拟实验的相似性原则

风洞模拟实验是研究起、降尘过程最有效的手段。前人只研究了低湍流度气流中,平坦表面的实际起尘过程。作者提出一组扩展的相似性原则,用于模拟大气边界层湍流及复杂地形对趋、降尘过程的影响及防尘风障在此条件下的减尘效率,并得到一系列有意义的结果。      

Characterization particulate matter from several Chinese cooking dishes and implications in health effects

Cooking fume produced by oil and food at a high temperature releases large amount of fine particulate matter(PM) which have a potential hazard to human health. This chamber study investigated particle emission characteristics originated from using four types of oil(soybean oil, olive oil, peanut oil and lard) and different kinds of food materials(meat and vegetable). The corresponding emission factors(EFs) of number, mass, surface area and volume for particles were discussed. Temporal variation of size-fractionated particle concentration showed that olive oil produced the highest number PM concentration for the entire cooking process. Multiple path particle dosimetry(MPPD) model was performed to predict deposition in the human respiratory tract. Results showed that the pulmonary airway deposition fraction was the largest. It was also found that particles produced from olive oil led to the highest deposition. We strongly recommend minimizing the moisture content of ingredients before cooking and giving priority to the use of peanut oil instead of olive oil to reduce human exposure to PM.     

重庆远郊丰都雪玉洞流域大气无机氮湿沉降变化特征与来源分析

以重庆市远郊的丰都雪玉洞流域为研究对象,利用气象站和大气氮沉降仪获取2015年7月~2017年12月的大气降水、NH_4~+-N和NO_3~--N等数据,通过NH_4~+-N/NO_3~--N比以及气团后向轨迹模拟探讨了流域大气无机氮湿沉降来源.结果表明:(1)在观测期内,流域DIN总沉降通量为21.37×103kg·a-1,单位面积沉降通量为14.25 kg·(hm~2·a)~(-1),其中NH_4~+-N和NO_3~--N分别为7.72 kg·(hm~2·a)~(-1)和6.53 kg·(hm~2·a)~(-1),分别占DIN湿沉降量的54%和46%;(2)DIN湿沉降通量和浓度表现出明显的季节变化,春夏季DIN湿沉降量比秋冬季节高50%,而秋冬季湿沉降的DIN浓度比春夏季高30%;(3)NH_4~+-N/NO_3~--N介于0.29~2.27之间,雨季(4月~9月)NH_4~+-N/NO_3~--N1,旱季(10月~次年3月)NH_4~+-N/NO_3~--N1,表明流域雨季DIN湿沉降主要来源农业源,旱季主要来源于城市源;(4)流域雨季主要受东南风的影响,大气湿沉降的NH_4~+-N来源于当地与流域东南方向的农业源,旱季主要受西南风影响,大气湿沉降的NO_3~--N来源于流域西南方向的重庆市区和涪陵等城市源.     

Analysis and improving ways for water condition in winter wheat field of dryland in subhumid areas of the loess plateau

Based on the soil moisture data from the locating experiments from 1986-1990, and using the water balance method, the water supply and demand state in the field of winter wheat, and the ways for improving water condition in dryland of subhumid by dry area of the Loess Plateau were studied. The results suggested that a low precipitation satisfying ratio of 42.9%-58.8% appears in the growing period of winter wheat, and the yield, to a great extent depends on the water that was stored in deep soil layer in the previous rainy season. The filed trial results showed that tillage in the summer fallow period,straw cover, soil moisture regulation with adequate fertilization, crop rotation and proper croppingsystem could be the efficient ways for improving the water condition,and for the exploitation and utilization of natural water resources(both precipitation and soil water) in the winter wheat field of dryland.     

长江上游小型水库枯水期水质对景观组成、配置和水库特征的响应

长江流域小型水库数量多分布广,具有重要的生态经济效益,探明小型水库水质对环境变量的响应规律对于提升水库水质具有非常重要的意义.基于长江上游36个小型水库枯水期水质数据,运用相关分析和冗余分析等研究方法,将环境变量划分为景观配置指标、景观组成指标和水库特征指标这三大类,探明其对水质指标变化的影响.结果表明：(1)旱地是NO^-₃-N、TN和TP的主要来源;居民点是TP物质的主要来源;水田、林地和荒草地对水库N、P的截留和净化具有正向作用;(2)旱地最大斑块指数与水库TN和NO^-₃-N浓度显著正相关,水田散布与并列指数、林地散布与并列指数与水库NO^-₃-N和TN浓度显著负相关;旱地斑块密度与TP物质含量显著正相关;林地最大斑块指数与TP含量显著负相关;(3)水库库容、水库平均深度和水库形状指数对水库水质提升具有显著的正向作用;(4)水库环境变量中,景观配置指标对水库水质指标变化的解释率最高(24%),其次是水库特征指标(11%),最后为景观组成指标(9%).流域...     

大气污染物对流垂直输送作用的探讨

利用一个欧拉型硫沉降模式探讨了积云对硫污染物的对流垂直输送作用．结果表明,积云引起的垂直气流是造成大气污染物浓度分布及输送通量变化的重要因素．对流垂直输送可使硫污染物在高层出现大浓度区,浓度的增加率为５０％—４００％,中层和低层的浓度相应也有所变化．积云区内南北剖面上的通量也因对流输送作用在高层出现了大值中心．     

改进的BP算法在黄河下游枯季径流预测中的应用

本在黄河下游地区应用多层前向人工神经网络理论,通过改进BP算法,建立下游枯季径流预测的BP神经网络模型,使用花园口-利津水站26年的完整序列测流资料训练和检验网络并用于预测,结果表明,通过本次研究建立的BP网络模型是合理的,可靠的,它较好地反映了黄河下游的枯季径流规律,可为今后黄河流域水资源的统一调度,管理,尤其是预防黄河下游再次出现断流提供科学依据。     

多因素作用下同庭湖洪水调蓄量的变化

用实测资料分析比较了出口水位31．0m时,洞庭湖调蓄量的变化趋势及影响调蓄量的各种因素。用多元线性回归方法建立了调蓄量经验公式,并用该公式计算分析了各因素对调蓄量变化的影响。结果表明,该公式能够较全面地反映调蓄量变化的原因,且能够近似区分淤积和围垦对调蓄量的影响。     

Deposition of reactive nitrogen during the Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study

Increases in reactive nitrogen deposition are a growing concern in the U.S. Rocky Mountain west. The Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study was designed to improve understanding of the species and pathways that contribute to nitrogen deposition in Rocky Mountain National Park (RMNP). During two 5-week field campaigns in spring and summer of 2006, the largest contributor to reactive nitrogen deposition in RMNP was found to be wet deposition of ammonium (34% spring and summer), followed by wet deposition of nitrate (24% spring, 28% summer). The third and fourth most important reactive nitrogen deposition pathways were found to be wet deposition of organic nitrogen (17%, 12%) and dry deposition of ammonia (14%, 16%), neither of which is routinely measured by air quality/deposition networks operating in the region. Total reactive nitrogen deposition during the spring campaign was determined to be 0.45 kg ha⁻¹ and more than doubled to 0.95 kg ha⁻¹ during the summer campaign.     

Soil type affects migration pattern of airborne Pb and Cd under a spruce-beech forest of the UN-ECE integrated monitoring site Zöbelboden, Austria

Anthropogenic trace element emissions have declined. However, top soils all over the world remain enriched in trace elements. We investigated Pb and Cd migration in forest soils of a remote monitoring site in the Austrian limestone Alps between 1992 and 2004. Large spatial variability masked temporal changes in the mineral soil of Lithic Leptosols (Skeltic), whereas a significant reduction of Pb concentrations in their forest floors occurred. Reductions of concentrations in the less heterogeneous Cambisols (Chromic) were significant. In contrast, virtually no migration of Pb and Cd were found in Stagnosols due to their impeded drainage. Very low element concentrations (<1 μg l⁻¹) in field-collected soil solutions using tension lysimeters (0.2 μm nylon filters) imply that migration largely occurred by preferential flow as particulate-bound species during intensive rainfall events. Our results indicate that the extent of Pb and Cd migration in soils is largely influenced by soil type.