A GIS Framework for Regional Modeling of Riverine Nitrogen Transport: Case Study,San Antonio and Guadalupe Basins

This article presents a framework for integrating a regional geographic information system (GIS)‐based nitrogen dataset (Texas Anthropogenic Nitrogen Dataset, TX‐ANB) and a GIS‐based river routing model (Routing Application for Parallel computation of Discharge) to simulate steady‐state riverine total nitrogen (TN) transport in river networks containing thousands of reaches. A two‐year case study was conducted in the San Antonio and Guadalupe basins during dry and wet years (2008 and 2009, respectively). This article investigates TN export in urbanized (San Antonio) vs. rural (Guadalupe) drainage basins and considers the effect of reservoirs on TN transport. Simulated TN export values are within 10 percent of measured export values for selected stations in 2008 and 2009. Results show that in both years the San Antonio basin contributed a larger quantity than the Guadalupe basin of delivered TN to the coastal ocean. The San Antonio basin is affected by urban activities including point sources, associated with the city of San Antonio, in addition to greater agricultural activities. The Guadalupe basin lacks major metropolitan areas and is dominated by rangeland, rather than fertilized agricultural fields. Both basins delivered more TN to coastal waters in 2009 than in 2008. Furthermore, TN removal in the San Antonio and Guadalupe basins is inversely related to stream orders: the higher the order the more TN delivery (or the less TN removal).     

关于重点排污单位名录制定和使用过程中存在的问题及建议

2017年11月,原环境保护部办公厅发布《关于印发重点排污单位名录管理规定(试行)的通知》,对重点排污单位的基本管理要求和筛选条件作出了详细规定。重点排污单位是国家重点监控企业的替代和延续,成为当前排污许可制度尚未完全成熟阶段环境管理的重要抓手。重点排污单位名录聚焦影响环境质量的主要污染物、排污大户和重大风险源,由设区的市级地方人民政府生态环境主管部门确定,有利于压实地方环保责任。在名录制定和使用过程中存在着部分指导性文件存疑、名录重点不突出、部分重点排污单位无法安装自动监测设备、不能满足新的环境监管需求、名录更新时间滞后、缺少罚则等问题,本文就此进行了深入分析并提出了几点建议。     

排污许可审计式合规核查研析——以火电企业为例

针对排污单位证后守法情况,以火电企业为例,设计了三阶段的“审计式”合规核查机制,主管部门可以依次对执行报告及其支撑材料、自行监测和台账记录等内容进行完整性、规范性、逻辑性核查,以识别企业在按证守法方面存在的问题,发现企业存在的未按期提交执行报告、未按技术规范要求计算排放量、台账数据不合逻辑等潜在的线索,为下一步进行现场检查及现场执法提供指引。     

排污许可量核算方法与体系研究——以沈阳市为例

为给沈阳市排污许可证发放与管理提供技术支持,提出了产排污系数法、标准限值法、物料衡算法、环评资料复用法、实测法结合应用的核算方法作为沈阳市排污许可证量核算方法,并对核算方法的使用条件及核算结果进行技术分析,为环境保护部门"一证式"管理提供了科学的执法依据,为企业按证排污提供技术指导。     

Efficient degradation of chlorobenzene in a non-thermal plasma catalytic reactor supported on CeO2/HZSM-5 catalysts

Chlorobenzene removal was investigated in a non-thermal plasma reactor using CeO₂/HZSM-5 catalysts. The performance of catalysts was evaluated in terms of removal and energy efficiency. The decomposition products of chlorobenzene were analyzed. The results show that CeO₂/HZSM-5 exhibited a good catalytic activity, which resulted in enhancements of chlorobenzene removal, energy efficiency, and the formation of lower amounts of by-products. With regards to CO₂ selectivity, the presence of catalysts favors the oxidation of by-products, leading to a higher CO₂ selectivity. With respect to ozone, which is considered as an unavoidable by-product in air plasma reactors, a noticeable decrease in its concentration was observed in the presence of catalysts. Furthermore, the stability of the catalyst was investigated by analyzing the evolution of conversion in time. The experiment results indicated that CeO₂/HZSM-5 catalysts have excellent stability: chlorobenzene conversion only decreased from 78% to 60% after 75 hr, which means that the CeO₂/HZSM-5 suffered a slight deactivation. Some organic compounds and chlorinated intermediates were adsorbed or deposited on the catalysts surface as shown by the results of Fourier Transform Infrared (FT-IR) spectroscopy, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses of the catalyst before and after the reaction, revealing the cause of catalyst deactivation.     

低温等离子体技术在汽车尾气净化中的应用

介绍了低温等离子体技术及在汽车尾气净化中的应用和发展现状,阐述了低温等离子体产生的方法,讨论了其在汽车尾气净化过程中的机理,并提出了目前该技术在实际应用中还存在的一些局限性。     

关于“总量”问题的思考

对有关总量（水体纳污总量、污染物排放总量和目标断面通量）的内涵及总量监测技术的关键环节（布点采样、项目频次、实验室分析和数据处理方法）进行了论述     

Simplified multiple equations' inverse problem of vented vessels subjected to internal gas explosions

This paper analyses the experimental data reported by Höchst and Leuckel (1998) for combustion in partially confined vessels and uses the data from these experiments to establish the burning rate based on a simplified model for the combustion process in such vessels. The model establishes three fundamental parameters which are necessary in characterizing the combustion process. These are: i) the burning rate, ii) the fraction of vent area occupied by burnt gas (or discharge sub-model), and iii) the vent area model (if cover mechanisms with variable vent areas are utilized). A set of independent equations is derived to determine the burning rate according to conservation of mass and volume for each gas fraction separately along with a general equation based on general volume conservation. Using this method we are able to describe the combustion process and examine the effect of various discharge models. The advantages of the model presented here include rapid applicability and a valuable analysis to derive mass burn rate and other useful parameters using experimental data from vented explosions with reasonable residual reactant values. Based on these results, the correct interpretation of the obtained burning rate can be used in order to explain the correct prediction of flame velocity and position according to a reasonable discharge model. The paper also evaluates the suitability of several discharge models for phenomenological models of vented explosions. The most appropriate is a Heaviside step function which considers that only unburnt gas is initially expelled, with that component decreasing and the burnt gas component increasing until finally only burnt gas is expelled. The obtained results in this study can be used to predict the burning rate behavior and the combustion process of similar problems.     

Numerical study of choked two-phase flow of hydrocarbons fluids through orifices

Valves and orifices are the most widely devices of flow control used in oil and gas industry. In particular, they are installed in relief piping system in order to control the discharge flow during potential plant overpressuring scenarios, thus ensuring plant safety. It is a common practice to flow liquid and gas mixtures through such restriction devices.Rigorous models are available to precisely size pressure relief devices operating in single phase flow; however for two-phase flow, no models are considered sufficiently reliable for predicting the relevant flow conditions.In the present paper, two-phase flow of hydrocarbons fluids through an orifice under critical conditions has been numerically investigated.The existing literature has been analyzed and data on two-phase flow of highly volatile mixtures of hydrocarbons through openings have been collected. A comparison has been carried out with numerical simulations carried out by the multiphase flow simulation tool OLGA by SPT.The Henry–Fauske model has been used as orifice choke model and the orifice discharge flow coefficient, required as input by OLGA, has been calculated by Chisholm's model.Comparison between OLGA's results and experimental data shows that Henry–Fauske model markedly underestimates the mass flow rate through the orifice, if Chisholm's model is used to calculate discharge coefficient. It was found that the error of the model could be minimized using different values of orifice discharge coefficient (C_d).A new discharge flow coefficient model, suitable for choked two-phase flow across orifices, is proposed in this study and it has been determined to match the above mentioned experimental measurements.     

Effluents from MBT plants: Plasma techniques for the treatment of VOCs

Mechanical–biological treatments (MBTs) of urban waste are growing in popularity in many European countries. Recent studies pointed out that their contribution in terms of volatile organic compounds (VOCs) and other air pollutants is not negligible. Compared to classical removal technologies, non-thermal plasmas (NTP) showed better performances and low energy consumption when applied to treat lowly concentrated streams. Therefore, to study the feasibility of the application of NTP to MBTs, a Dielectric Barrier Discharge reactor was applied to treat a mixture of air and methyl ethyl ketone (MEK), to simulate emissions from MBTs. The removal efficiency of MEK was linearly dependent upon time, power and specific input energy. Only 2–4% of MEK was converted to carbon dioxide (CO₂), the remaining carbon being involved in the formation of byproducts (methyl nitrate and 2,3-butanedione, especially). For future development of pilot-scale reactors, acting on residence time, power, convective flow and catalysts will help finding a compromise between energy consumption, desired abatement and selectivity to CO₂.