ENERGY BALANCE OF A CORN RESIDUE-COVERED FIELD DURING SNOWMELT1

ABSTRACT: Transport of agricultural chemicals in runoff and recharge waters from snowmelt and soil thawing may represent a significant event in terms of annual contaminant loadings in temperate regions. Improved understanding of the melt dynamics of shallow snowpacks is necessary to fully assess the implications for water quality. The objective of this study was to measure the energy balance components of a corn (Zea mays L.) stubble field during the melting of its snowcover. Net radiation (Rn), soil (G), sensible (H), and latent (Q) heat fluxes were measured in a field near Ames, Iowa, during the winter of 1994–1995. Energy consumed by melting including change in energy storage of the snowpack was determined as the residual of the measured energy balance. There was continuous snowcover at the field site for 71 days (maximum depth = 222 mm) followed by an open period of 11 days before additional snowfall and a second melt period. The net radiation and snow melt/energy storage change (5) terms dominated the energy balance during both measurement intervals. Peak daily sensible and latent heat fluxes were below 100 W m^?2 on all days except the last day of the second melt period. There was good agreement between predicted and measured values of H and Q during the melting of an aged snow layer but poorer agreement during the melt of fresh snow. Both snowpacks melted rapidly and coincident changes in soil moisture storage were observed. Improved estimates of Q and H, especially for partially open surfaces, will require better characterization of the surface aerodynamic properties and spatially-representative surface temperature measurements.     

渤海湾南部沿岸海区1992—1995年结冰特征与分析

本文对渤海湾南部沿岸海区１９９２－１９９５年冬季现场海冰的实测资料进行了分析总结，探讨研究了该海区海冰的外貌特征，冰情特性及生消变化情况，并对影响该海区冰情的最重要因素－气温与海冰的关系进行了分析。     

松花江有机污染物的污染特征研究

松花江地处寒冷地区,每年冰封期长达5个月之久,其环境污染特征与国内其它大江河有着明显的不同.冰封期有机毒物污染加重是松花江最重要的环境污染特征;松花江流域存在着工业企业的点源污染和地表径流带来的面源污染,研究表明,松花江流域的有机毒物污染是以点源污染为主;有机毒物对江水中CODMn的贡献值极小,甚至不产生贡献.江水中CODMn值不能反映出有机毒物的污染状况.     

斜面结构上二维冰力计算模型的物理模拟实验研究

介绍了应用模型冰进行45°、60°、75°斜面墙冰作用力模拟实验装置、安装和结果，描述了冰排在不同倾角结构前的冰排破碎过程，以45°倾角结构的水平和垂直冰力-时间曲线分析作用力过程，并统计了各实验的冰力特征值。利用这些实测冰力与二维理论计算冰力的比较阐明该理论模型在浅水条件下应用的可行性，并用水平冰力同垂直冰力比值分析碎冰堆积对冰力的影响。     

现代环境事件的冰芯记录

1997年9月，在喜马拉雅山中段希夏邦马峰北坡达索普冰川海拔7000m冰雪平台钻取14m冰芯一支。1990年以来冰芯中主要离子浓度的变化表明，现代环境事件在达索普冰川雪冰中有一定的记录。已有的证据表明1991年达索普冰芯中SO^2-4浓度的最高值最大可能是由海湾战争引发的1991年春季科威特油井燃烧污染物所致。冰芯中陆源离子（如Ca^2 和SO^2-4等）记录与我国西北地区春季沙尘暴具有某些相关性，其逐年变化趋势与新疆13个城市的降尘变化有一定的共性。     

Prediction of aqueous solubility of PCBs based on molecular structure

The thermodynamic relationships among aqueous solubility and molar volume (MV) , total molecular surface area (TSA) and molecular connectivity index (MCI) for highly hydrophobic chemicals. PCBs are established and discussed, respectively. Good linear relationships exist among In Cs and MV, TSA or MCI.     

Low intensity ultrasound stimulates biological activity of aerobic activated sludge

This work aims to explore a procedure to improve biological wastewater treatment efficiency using low intensity ultrasound. The aerobic activated sludge from a municipal wastewater treatment plant was used as the experimental material. Oxygen uptake rate (OUR) of the activated sludge (AS) was determined to indicate the changes of AS activity stimulated by ultrasound at 35 kHz for 0–40 min with ultrasonic intensities of 0–1.2 W/cm². The highest OUR was observed at the ultrasonic intensity of 0.3 W/cm² and an irradiation period of 10 min; more than 15% increase was achieved immediately after sonication. More significantly, the AS activity stimulated by ultrasound could last 24 h after sonication, and the AS activity achieved its peak value within 8 h after sonication, or nearly 100% higher than the initial level after sonication. Therefore, to improve the wastewater treatment efficiency of bioreactors, ultrasound with an intensity of 0.3 W/cm² could be employed to irradiate a part of the AS in the bioreactor for 10 min every 8 h. Translated from Environmental Science, 2005, 26(4): 124–128 [译自: 环境科学]     

Effect of acidic deposition on productivity of forest ecosystem and estimation of its economic losses in southern suburbs of Chongqing, China

ＥｆｅｃｔｏｆａｃｉｄｉｃｄｅｐｏｓｉｔｉｏｎｏｎｐｒｏｄｕｃｔｉｖｉｔｙｏｆｆｏｒｅｓｔｅｃｏｓｙｓｔｅｍａｎｄｅｓｔｉｍａｔｉｏｎｏｆｉｔｓｅｃｏｎｏｍｉｃｌｏｓｅｓｉｎｓｏｕｔｈｅｒｎｓｕｂｕｒｂｓｏｆＣｈｏｎｇｑｉｎｇ，ＣｈｉｎａＷｕＧａｎｇ...     

Effect of acidic deposition on productivity of forest ecosystem and estimation of its economic losses in southern suburbs of Chongqing

In accordance with principle sand methods of ecology,this paper studied the effects of acidic deposition on productivity and volume increment of masson pine and Cinnamomum campora forest which are widely distributed in southern suburbs of Chongqing. Based on the field data and measurements, a multivariable stepwise regression model was established to analyze the effects of multiple environmental factors on the productivity of the forest ecosystems. This model was used to assess the volume and economic losses of these two forest ecosystems caused by acidic deposition. The results showed that, among the environmental factors, pH value of precipitation, soil depth, soil organic contents and slope are the dominant ones influencing the growth of masson pine forest. It is also shown that the acidic deposition has no clear relation to the growth of C.Campora forest, so development of such broad-leaved forest is suitable in the area.     

酸沉降对重庆南岸马尾松针叶林年生物生产量的影响及其经济损失的估算

利用生态学方法研究了酸沉降对重庆南岸马尾松针叶林和樟树阔叶林年生物生产量及年材积生长量的影响．在野外调查观测的基础上，用多元逐步回归法分析了诸多环境因子对两种森林生态系统年生物生产量的影响，并估算了酸沉降引起的重庆南岸（酸雨严重危害地区）马尾松针叶林的年材积损失量和生态经济损失值．结果表明，在诸多环境因子中，土壤有机质含量、降水ｐＨ值、土层厚度及坡度是影响马尾松针叶林生长的主导因子，其与生物量的相关系数分别为０．９９４０、０．９７６２、０．９７３８、０．９４３６．由此引起的重庆南岸马尾松针叶林的直接经济损失达３０３．３２万元／ａ；酸沉降对樟树阔叶林无显著影响，建议在该地区发展樟树阔叶林．