Evolution Of Pollutant Concentrations Research Articles

Математическое моделирование физических процессов в электромагнитных фильтрах воды и теплообменных установках

The paper proposes a complex mathematical model designed to analyze the processes taking place in electromagnetic water filters and heat exchangers in terms of scale formation and removal. The formed mathematical model includes models of fluid flow taking into account thermal effects, the evolution of pollutant concentration with the reflection of convection-diffusion processes and electrostatic effects to take into account filtration effects. The software implementation of the computational algorithm for three-dimensional geometry is based on the finite volume grid method and parallel computing. The results of model calculations were obtained for the problem of electromagnetic water cleaning and the problem of scale contamination of the heat exchanger using the developed software package.

Spatial-temporal variation characteristics of air pollution and apportionment of contributions by different sources in Shanxi province of China

With the implementation of the Air Pollution Prevention and Control Action Plan (APPCAP) since 2013, significant declines in pollutants concentrations have achieved in nationwide of China. However, as one of the major coal-production bases and intensive energy-consuming provinces in China, Shanxi has still been suffering from severe air quality problems in recent years. In this study, by combining a detailed bottom-up emission inventory and the weather research and forecasting (WRF) model/comprehensive air quality model with extensions (CAMx) model, the evolution of pollutant concentrations, source apportionment, and migration potentials from 2012 to 2015 in Shanxi are investigated. Estimated primary air pollutants emission declined significantly during 2012–2015. Compared with 2012, the simulated concentrations of PM2.5, PM10, SO2 and NO2 in January of 2015 are reduced by 24.7%, 24.1%, 23.0% and 18.0%, respectively. In contrast, heavy contaminated areas have shown negligible variations, which are highly concentrated in Taiyuan, Linfen, Jincheng, Changzhi, Lvliang, Yangquan and Jinzhong cities. In terms of contribution by source categories, the other industries and residential sources are identified as the most significant local contributors for PM2.5 and PM10, while SO2 and NO2 are mainly emitted by other industries and power plants. Scenarios analysis of 50% emission mitigation suggests that the emission reduction measures are generally more effective in summer than in winter. Moreover, the mitigation potential for each city varies from each other. These results indicate that more appropriate seasonal-specific emission reduction measures in each prefecture-level city should be implemented to further improve regional air quality and thus better protect public health.

The Evolution of Pollutant Concentrations in a River Severely Affected by Acid Mine Drainage: Río Tinto (SW Spain)

The Río Tinto, located in the Iberian Pyrite Belt (SW Spain), constitutes an extreme case of pollution by acid mine drainage. Mining in the area dates back to the Copper Age, although large-scale mining of massive sulfide deposits did not start until the second half of the 19th century. Due to acidic mining discharges, the Río Tinto usually maintains a pH close to 2.5 and high concentrations of pollutants along its course. From a detailed sampling during the hydrological year 2017/18, it was observed that most pollutants followed a similar seasonal pattern, with maximum concentrations during autumn due to the washout of secondary soluble sulfate salts and minimum values during large flood events. Nevertheless, As and Pb showed different behavior, with delayed concentration peaks. The dissolved pollutant load throughout the monitored year reached 5000 tons of Fe, 2600 tons of Al, 680 tons of Zn, and so on. While most elements were transported almost exclusively in the dissolved phase, Fe, Pb, Cr, and, above all, As showed high values associated with particulate matter. River water quality data from 1969 to 2019 showed a sharp worsening in 2000, immediately after the mine closure. From 2001 on, an improvement was observed.

CFD evaluation of mean pollutant concentration variations in step-down street canyons

Atmospheric pollution became a big issue in densified urban areas where the ventilation in streets is not sufficient. It is particularly the case for street surrounded by high buildings so-called street canyons. The ventilation and, thus, the concentrations in this kind of street are highly relying on geometric properties of the street (width of the street, heights of the buildings, etc.). Reynolds-averaged Navier-Stokes equations are used to investigate the impact of two geometric street ratios on pollutant dispersion: the ratio of the leeward to the windward building height (H1/H2) and the ratio of the street width to the windward building height (W/H2). The aim is to quantitatively assess the evolution of mean pollutant concentrations in the case of step-down street canyons with H1/H2 ranging from 1.0 to 2.0 and street width ratios W/H2 ranging from 0.6 to 1.4. Three types of recirculation regimes could be established, depending on the number and the direction of the vortices occurring inside and outside the canyon. Evolution of pollutant concentrations as a function of both ratios is provided as well as the recommended regimes in the perspective of reducing pollutant concentration in step-down street canyons at pedestrian level and near building faces.

Partial degradation of five pesticides and an industrial pollutant by ozonation in a pilot-plant scale reactor

Aqueous solutions of a mixture of several pesticides (alachlor, atrazine, chlorfenvinphos, diuron and isoproturon), considered PS (priority substances) by the European Commission, and an intermediate product of the pharmaceutical industry (α-methylphenylglycine, MPG) chosen as a model industrial pollutant, have been degraded at pilot-plant scale using ozonation. This study is part of a large research project [CADOX Project, A Coupled Advanced Oxidation-Biological Process for Recycling of Industrial Wastewater Containing Persistent Organic Contaminants, Contract No.: EVK1-CT-2002-00122, European Commission, http://www.psa.es/webeng/projects/cadox/index.html [1]] founded by the European Union that inquires into the potential coupling between chemical and biological oxidations for the removal of toxic or non-biodegradable contaminants from water. The evolution of pollutant concentration, TOC mineralization, generation of inorganic species and consumption of O 3 have been followed in order to visualize the chemical treatment effectiveness. Although complete mineralization is hard to accomplish, and large amounts of the oxidant are required to lower the organic content of the solutions, the possibility of ozonation cannot be ruled out if partial degradation is the final goal wanted. In this sense, Zahn–Wellens biodegradability tests of the ozonated MPG solutions have been performed, and the possibility of a further coupling with a secondary biological treatment for complete organic removal is envisaged.

A Composite Modeling Study of Civil Aircraft Impacts on Ozone and Sulfate over the Taiwan Area

Aircraft induced ozone and sulfate perturbations calculated from a Lagrangian plume model were composed into a regional distribution to quantify the impacts of aircraft emissions at the international and domestic flight altitudes of about 11.5 and 6.5 km, respectively, over Taiwan. The evolution of pollutant concentrations within a Lagrangian aircraft plume was first calculated with consideration of gas-phase chemistry and mixing of ambient air. Due to reaction with high concentration of aircraft emitted NO, the O 3 concentration in fresh aircraft plumes rapidly decreased by more than 15 ppb during the first few hours after emissions. Then, becauseof mixing with the ambient air that contained higher O 3 and lower NO x concentrations, as well as the conversion of NO into NO 2 , the O 3 concentrations in aged plumes increased and became somewhat (up to 2 ppb) higher than in the ambient air as the plumes were transported further downwind. The sulfate concentration within the aircraft plumes, on the other hand, was enhanced due to chemical conversion of the emitted SO 2 . At both the domestic and international flight altitudes, enhancements of up to 10 and 5 ppt greater than in the background were achieved a couple of days after emissions. In the aged and diluted plumes, however, the production of sulfate can be lower than in the ambient because of the lower OH concentration. The plume results were converted into regional-scale distributions by including all flight frequencies at each international and domestic flight corridor, as well as the probability distribution of the wind speed at the cruising altitudes to account for the advection effect. These composite results indicated that aircraft emissions led to negative perturbation of O 3 concentration at and just downwind of the flight corridors, with maximum O 3 reduction of about 1 and 4% at the international and domestic flight altitudes, respectively. The total column (vertically integrated through troposphere) O 3 , however, was enhanced because the emitted aircraft plumes were transported by various wind speeds and those plumes that stay longer