基于CALPUFF模型的漳州市大气环境容量研究

研究表明：CALPUFF模式是运用于广域的大气扩散模型,在区域范围较大的复杂地形条件下的应用具有突出的优势.利用CALPUFF大气扩散模型模拟漳州市2009年气象场和污染物浓度场,采用监测值对模拟结果进行验证表明模型的适用性;基于现状污染源,建立大气污染物传递系数矩阵,结合线性优化法测算了不同环境空气质量标准下漳州市大气环境容量.     

Numerical simulation of water curtain application for ammonia release dispersion

Using water curtain system to forced mitigate ammonia vapor cloud has been proven to be an effective measure. Currently, no engineering guidelines for designing an effective water curtain system are available, due to lack of understanding of complex interactions between ammonia vapor cloud and water droplets, especially the understanding of ammonia absorption into water droplets. This paper presents numerical calculations to reproduce the continuous ammonia release dispersion with and without the mitigating influence of a downwind water curtain using computational fluid dynamic (CFD) software ANSYS Fluent 14.0. The turbulence models k–ɛ and RNG were used to simulate the ammonia cloud dispersion without downwind water curtain. The simulated results were compared with literature using the statistical performance indicators. The RNG model represents better agreement with the experimental data and the k–ɛ model generates a slightly lesser result. The RNG model coupled with Lagrangian discrete phase model (DPM) was used to simulate the dilution effectiveness of the water curtain system. The ammonia absorption was taken into account by means of user-defined functions (UDF). The simulated effectiveness of water curtains has good agreements with the experimental results. The effectiveness of water mitigation system with and without the ammonia absorption was compared. The results display that the effectiveness mainly depends on the strong air entrainment enhanced by water droplets movement and the ammonia absorption also enhances the effectiveness of water curtain mitigation system. The study indicates that the CFD code can be satisfactorily applied in design criteria for an effective mitigation system.     

Multi-response optimization of Fenton process for applicability assessment in landfill leachate treatment

Fenton process, as a pretreatment method, was found to be effective in the primary treatment of mature/medium landfill leachate. However, the main problem of the process is the large amount of produced sludge that requires an accurate feasibility evaluation for operational applications. In this study, the response surface methodology was applied for the modeling and optimization of Fenton process in three target responses, (1) overall COD removal, (2) sludge to iron ratio (SIR) and (3) organics removal to sludge ratio (ORSR), where the latter two were new self-defined responses for prediction of sludge generation and applicability assessment of the process, respectively. The effective variables included the initial pH, [H₂O₂]/[Fe²⁺] ratio and Fe²⁺ dosage. According to the statistical analysis, all the proposed models were adequate (with adjusted R² of 0.9116–0.9512) and had considerable predictive capability (with prediction R² up to 0.9092 and appropriate adequate precision). It was found that all the variables had significant effects on the responses, specifically by their observed role in dominant oxidation mechanism. The optimum operational conditions obtained by overlay plot, were found to be initial pH of 5.7, [H₂O₂]/[Fe²⁺] ratio of 17.72 and [Fe²⁺] of 195 mM, which led to 69% COD removal, 2.4 (l sludge/consumed mole Fe²⁺) of SIR and 16.5 (gCOD removed/l produced sludge) for ORSR in verification test, in accordance with models-predicted values. Finally, it was observed that [H₂O₂]/[Fe²⁺] ratio and Fe²⁺ dosage had significant influence on COD removal, while Fe²⁺ dosage and [H₂O₂]/[Fe²⁺] ratio had remarkable effects on SIR and ORSR responses, respectively.     

SACRAMENTO RIVER FLOW RECONSTRUCTED TO A.D. 869 FROM TREE RINGS1

ABSTRACT: A time series of annual flow of the Sacramento River, California, is reconstructed to A.D. 869 from tree rings for a long‐term perspective on hydrologic drought. Reconstructions derived by principal components regression of flow on time‐varying subsets of tree‐ring chronologies account for 64 to 81 percent of the flow variance in the 1906 to 1977 calibration period. A Monte Carlo analysis of reconstructed n‐year running means indicates that the gaged record contains examples of drought extremes for averaging periods of perhaps = 6 to 10 years, but not for longer and shorter averaging periods. For example, the estimated probability approaches 1.0 that the flow in A.D. 1580 was lower than the lowest single‐year gaged flow. The tree‐ring record also suggests that persistently high or low flows over 50‐year periods characterize some parts of the long‐term flow history. The results should contribute to sensible water resources planning for the Sacramento Basin and to the methodology of incorporating tree‐ring data in the assessment of the probability of hydrologic drought.     

Implications of simultaneity in a physical damage function

A modeler must often rely on highly simplified representations of complex physical systems when analyzing associated economic issues. Herein, we consider a management problem in which a bioeconomic system exhibits simultaneity in processes governing productivity and damage. In this case, it may benefit the producer to sacrifice productivity to reduce the costs associated with increased damage. We specify empirically a structural damage relationship that explains the biological process by which an invasive species damages a host and estimate the structural model and its reduced form with an exceptional dataset on infestation of olives by the olive fruit fly. We contrast the results of these models with the approach typically taken in the economic literature, which expresses damage as a function of pest density. The population-based approach introduces significantly greater bias into the individual grower's choice of damage-control inputs than estimates based on the structural model.     

Characterizing sources of nitrate leaching from an irrigated dairy farm in Merced County, California

Dairy farms comprise a complex landscape of groundwater pollution sources. The objective of our work is to develop a method to quantify nitrate leaching to shallow groundwater from different management units at dairy farms. Total nitrate loads are determined by the sequential calibration of a sub-regional scale and a farm-scale three-dimensional groundwater flow and transport model using observations at different spatial scales. These observations include local measurements of groundwater heads and nitrate concentrations in an extensive monitoring well network, providing data at a scale of a few meters and measurements of discharge rates and nitrate concentrations in a tile-drain network, providing data integrated across multiple farms. The various measurement scales are different from the spatial scales of the calibration parameters, which are the recharge and nitrogen leaching rates from individual management units. The calibration procedure offers a conceptual framework for using field measurements at different spatial scales to estimate recharge N concentrations at the management unit scale. It provides a map of spatially varying dairy farming impact on groundwater nitrogen. The method is applied to a dairy farm located in a relatively vulnerable hydrogeologic region in California. Potential sources within the dairy farm are divided into three categories, representing different manure management units: animal exercise yards and feeding areas (corrals), liquid manure holding ponds, and manure irrigated forage fields. Estimated average nitrogen leaching is 872 kg/ha/year, 807 kg/ha/year and 486 kg/ha/year for corrals, ponds and fields respectively. Results are applied to evaluate the accuracy of nitrogen mass balances often used by regulatory agencies to assess groundwater impacts. Calibrated leaching rates compare favorably to field and farm scale nitrogen mass balances. These data and interpretations provide a basis for developing improved management strategies.     

GIS网络服务区分析在重庆市主城区夜间施工噪声投诉处置中应用

通过对重庆市主城区夜间施工噪声投诉处置现状分析,以主城区道路交通网络、环境监察机构分布等数据专题建模,采用G IS的网络服务区功能的分析结果,提出车辆调度合理化建议方案,为环境监察部门的夜间施工噪声投诉处置车辆部署调度提供辅助技术支持。     

APPLICATION OF A SEDIMENT ROUTING MODEL TO A MIDDLE EUROPEAN WATERSHED1

ABSTRACT: A simulation model that computes sediment yield due to sheet and rill erosion at the outlet of a large watershed requires daily precipitation and the soil, topographic, and vegetative characteristics of the watershed. An important problem, particularly in a large watershed, is the transport of sediment produced in the sub-watersheds to the outlet of the whole watershed. This problem is approached mathematically by a sediment routing model that is used as a component of the total model.     

WATER USE REDUCTIONS FROM RETROFIHNG INDOOR WATER FIXTURES1

ABSTRACT: A water use model was developed to estimate water savings from installation of low-flow showerheads and toilet displacement devices in residential housing. The model measures household water use in per capita terms with adjustments for age of occupants, household income, if occupants responsible for direct payment of water bill, and type of water fixtures. Detailed data on 308 single family residences involved with a pilot retrofit program in the Seattle, Washington, area were analyzed. We estimated per capita indoor water use to decline by 6.4 and 2.1 percent from complete installation of low-flow showerheads and toilet displacement devices, respectively.     

Integrated assessment: Missing link in the acid rain debate?

The United States is finding it difficult to develop a coherent policy on acid rain. Despite more than a decade of scientific research and policy initiatives, no clear course of action has been identified. This article argues that what is missing is an integrated assessment of the scientific knowledge that will guide the political process. The role of the integrated assessment is described, and a conceptual framework presented that would accomplish the desired goal. Currently available acid rain assessment models are compared against this framework and found to be less than satisfactory. The article concludes by stressing the opportunity now available to the National Acid Precipitation Assessment Program to perform such an assessment and break the logjam.