Variations in Spectral Slope in Lake Taihu,a Large Subtropical Shallow Lake in China

Spectral slope (S), describing the exponential decrease of the absorption spectrum over a given wavelength range, is an important parameter in the study of of chromophoric dissolved organic matter (CDOM) dynamics, and also an essential input parameter in remote sensing models. Furthermore, S is often used as a proxy for CDOM composition, including the ratio of fulvic to humic acids and molecular weight. The relative broad range in S values reported in the literature can be explained by the different spectral ranges and fitting methods used. A single exponential model is used to fit the S values for 17 investigations involving 458 samples in Lake Taihu from January to October in 2004. The average S value was 15.18 ± 1.39 μm⁻¹ for the range of 280–500 nm, which fell within the range reported in the literature. The frequency distribution of S value basically obeyed a normal distribution. Significant differences in S values between summer and other seasons showed that phytoplankton degradation was one of the important sources of CDOM in summer, whereas CDOM mainly came from the river input in other seasons. Furthermore, the estimated S value decreased with increasing wavelength range used in regression. The maximum and minimum values derived from the regression were 17.89 ± 1.25 μm⁻¹ and 13.62 ± 2.11 μm⁻¹ for the wavelength ranges of 280–380 nm and 400–500 nm, respectively, a decrease of 23.9%. S values significantly decreased with the increase of CDOM absorption coefficients. CDOM absorption coefficients could be more appropriately estimated from exponential model introducing the variation of S with absorption coefficients, making them useful for a remote sensing bio-optical model of Lake Taihu. DOC-specific absorption coefficient a*(λ) and the parameter M describing molecular size of the humic molecules could also be used as a proxy for the sources and types of CDOM. A general relationship was found between S and a*(λ), and M values. S increased with the decrease of DOC-specific absorption coefficient and the increase of M corresponding to the decrease of molecular weight.     

我国突发性水资源污染事故应急机制的若干问题评述

基于突发性水资源污染事故应急处理现状的分析,对目前我国突发性水资源污染事故防范和应急机制的建立进行探讨,指出当前工作中的三大缺陷,并有针对性地提出如何加快防范突发性水资源污染事故以及建立相关应急机制的进程的若干措施,包括突发污染事故的隐患调查、脆弱性评价、水质预报、动态监测以及应急组织机构等方面,以期能为我国减少突发性水资源污染事故及其损失提供一定的理论分析依据。     

Simulation of leachate migration in leaky aquifers

A two-dimensional cross-section finite difference model is presented to simulate density dependent leachate migration in leaky aquifers. Unlike existing models, a new approach is adopted to couple the groundwater-flow equation and the hydrodynamic dispersion equation with the elimination of the intermediate step of calculating velocities. The concept of the reference density is employed, permitting increased accuracy (over pressure-based models) in the representation of the transport process. The model is then used to study the effect of several hydraulic and transport parameters on the flow pattern and plume migration which are found to be very sensitive to most of these parameters. Equiconcentration and equipotential lines are overlapped to provide a better understanding of the coupling effect.     

MIKEII 软件系统在穆棱河流域面源污染估算中的应用

穆棱河流域面源污染入河量调查和估算采用了MIKEII软件系统，根据水质、水量实测数据，在参数率定和模型验证的基础上．对穆棱河部分河段的水质进行模拟，拟合出面源入河量和年内分布。经验证计算结果较其他方法更合理可靠。     

云南省水环境状况及问题分析

根据2000年云南省主要河流水质监测评价结果，全省评价河段总长9280km中，水质为Ⅰ－Ⅲ类的河长占76．3％，总体上，云南省内各大水系水质良好，但水污染总体上正在加重，从1985－2000年，Ⅰ类河长年均减少2．3％，V类河长年均增长0．6％，废污水直接排入江河是引起污染的重要原因。水环境问题已成为社会经济可持续发展的关键问题，要切实加强水资源的保护，科学地开发利用水土资源，为了有效地改善水环境的质量，污染控制应从源头开始并采取综合治理措施。     

Pollution Control in Open Economies: Implications of Within-period Interactions for Dynamic Game Equilibrium

This paper examines a two-country, dynamic game model of pollution control in the presence of economic interactions between countries within a period, as well as the environmental interaction between periods (i.e., a change in the stock of global pollution). These economic interactions emerge because of changes in the terms of trade of polluting goods or the market share of domestic polluting industries. It is shown that if within-period externalities exist, a noncooperative equilibrium may result in a smaller stock of global pollution in the steady state than does international cooperation. Moreover, the properties of equilibrium paths depend on the direction and size of such externalities. In addition, trigger strategy equilibria that achieve the outcome of the collusive solution are examined.     

黄浦江上游水源地突发性水污染事故应急处置预案探讨

阐述了水源地突发污染事件的概念、特点及其对于供水安全和城市经济社会系统安全运行的重要意义.论述了城市水源地突发污染事件应急研究的主要内容;以上海市黄浦江上游水源地为例,探讨了突发性污染事件应急处置体系的构建,并提出了相应的政策建议。     

Ambient Taxes Under m-Dimensional Choice Sets, Heterogeneous Expectations, and Risk-Aversion

We consider the design of ambient taxes forrisk-neutral and risk-averse polluters whenpolluters and the regulatory agency haveasymmetric information about environmentalrelationships and probabilities associatedwith random events. Unlike prior work, we showthat under these conditions, optimal ambienttaxes must be firm-specific, and accompaniedby additional incentives to influencepolluters' choices of abatement techniques.     

Particulate organic matter transport in the lower Colorado river,South-Western USA

The lower Colorado River from Laughlin, Nevada, to the border with Mexico is one of the most regulated rivers in North America. An analysis of particulate organic matter (POM) transport through the system was made to determine POM concentrations, composition and point of origin, as well as to determine the effect dams had on this transport. Particulate organic matter concentrations generally increased from upstream to downstream, and were dominated by very fine organic detritus (< 25μm size fraction). Reservoirs released more POM than they received during spring and summer, but less during autumn and winter. Reservoirs recycled POM, taking in organic detritus and discharging small limnoplankton. Backwater complexes functioned as filters during storm events, trapping coarse material and releasing fine material. Agricultural drains made only minor contributions of POM, but provided important nutrients for in-channel production of POM. Water diversions forced POM off-channel, whereas sluicing operations reduced inorganic loads in the canals. Despite the presence of six mainstem dams, the lower reaches support a diverse assemblage of detritivorous fishes, similar to that found in the lowermost reaches of natural, unregulated rivers. The food base for this fishery stems from autochthonous production of POM.     

Prevention versus Treatment under Precautionary Regulation: A Case Study of Groundwater Contamination under Uncertainty

Policy discussions on agricultural pollution problems characterize prevention as more cost effective and precautionary than ex post treatment. We derive conditions under which treatment alone is more cost effective in situations involving multiple sources of emissions, multiple sites affected, and a commonly used precautionary approach to uncertainty. We also show that a greater degree of precaution can result in less reliance on prevention. An empirical case study indicates that treatment alone is the most cost-effective means of dealing with nitrate in most Maryland community water system wells. The use of leaching prevention measures is restricted to the most intensive poultry producing areas. The incremental cost of precaution is substantial.