Spatial Variation Of Pollutants Research Articles

Unexpected biotic homogenization masks the effect of a pollution gradient on local variability of community structure in a marine urban environment

Urbanization of coastal habitats, often exemplified by harbors and marinas, has led to various ecological paradigms, questioning the functioning of these new ecosystems. In the present study we investigated, in a large Mediterranean harbor, whether spatial variation of pollution is present and if this variability drives the structure of the sessile community. We hypothesized locations to have significantly different communities, based on the assumption on the occurrence of environmental gradients of pollution that would constitute selective filters. Three distinct community types were identified in June, coinciding with spatially variable contaminants in sediments. We observed then an unexpected shift of the community between June and August associated to a sharp decrease in biodiversity and a decline of most species, masking the effects of local variation and thus leading to the homogenization of the biodiversity within the harbor. This shift coincided with successive heatwaves (the longest lasting 13 days over 25 °C, with a thermal peak at 28 °C) which might potentially be associated with a die-off in the harbor communities, regardless of location.

Application of a mobile laboratory using a selected-ion flow-tube mass spectrometer (SIFT-MS) for characterisation of volatile organic compounds and atmospheric trace gases

Abstract. Over the last 2 decades, the importance of emissions source types of atmospheric pollutants in urban areas has undergone significant change. In particular, there has been a considerable reduction in emissions associated with road vehicles. Understanding the role played by different source sectors is important if effective air pollution control is to be achieved. Current atmospheric measurements are made at fixed monitoring sites, most of which do not include the measurement of volatile organic compounds (VOCs), so our understanding of the temporal and spatial variation of pollutants is limited. Here we describe the application of a mobile laboratory using a selected-ion flow-tube mass spectrometer (SIFT-MS) and other trace gas instrumentation to provide on-road, high-spatial- and temporal-resolution measurements of CO2, CH4, VOCs and other trace gases. We then illustrate the potential of this platform for developing source characterisation methods that account for the similarity in correlation between species. Finally, we consider the benefits of high-spatial- and temporal-resolution measurements in characterising different types of sources, which would be difficult or impossible for single-species studies.

Study of speciation and spatial variation of pollutants in Anzali Wetland (Iran) using linear regression, Kriging and multivariate analysis.

Multivariate statistical techniques and geostatistical methods are among the important tools used in surface water quality management. They are widely used in interpreting data, identifying the pollution sources, understanding the spatial variation of parameters, and determining the places of monitoring stations. Therefore, in this study, spatial variation of water quality and pollutants in the Anzali Wetland water (Iran) was evaluated using multivariate statistical and Kriging methods. The values of different water quality parameters measured in six stations in the wetland water were subjected to cluster analysis (CA) and principal component analysis (PCA). Cluster analysis reduced the number of stations from six to four. The results of PCA showed that industrial and agricultural pollution sources could be responsible for the Anzali Wetland water quality. Then, the spatial variation maps of the PCA scores were generated using Kriging geostatistical method in the geographical information system (GIS) to investigate the pollution sources affecting the wetland parts. These maps illustrated that a great part of the wetland body was under the effect of agricultural sources, while the industrial sources affected the outlet and central parts. Finally, a comparison between two models (multiple linear regression (MLR) and Kriging) was made to assess their ability in predicting water quality parameters in the study area. The results showed the improvement of prediction using MLR, which was by 25%-97%, compared with Kriging. The results of the present study can be effectively used in the planning and implementation of future monitoring networks in the Anzali Wetland and other similar aquatic systems.

Assessment of ambient air quality in the port of Naples

Two experimental monitoring campaigns were carried out in 2012 to investigate the air quality in the port of Naples, the most important in southern Italy for traffic of passengers and one of the most important for goods. Therefore, it represents an important air pollution source located close to the city of Naples. The concentrations of sulfur dioxide (SO2), nitrogen dioxide (NO2), and BTEX (benzene, toluene, ethylbenzene, and xylenes) in the air were measured at 15 points inside the Naples port area through the use of passive samplers. In addition, a mobile laboratory was positioned in a fixed point inside the port area to measure continuous concentration of pollutants together with particulate matter, ambient parameters, and wind direction and intensity. The pollution levels monitored were compared with those observed in the urban area of Naples and in other Mediterranean ports. Even though the observation time was limited, measured concentrations were also compared with limit values established by European legislation. All the measured pollutants were below the limits with the exception of nitrogen dioxide: its average concentration during the exposition time exceeded the yearly limit value. A spatial analysis of data, according to the measured wind direction and intensity, provided information about the effects that ship emissions have on ambient air quality in the port area. The main evidence indicates that ship emissions influence sulfur dioxide concentration more than any other pollutants analyzed.Implications: Two monitoring campaigns were carried out to measure BTEX, SO2, NO2, and PM10 (particulate matter with an aerodynamic diameter <10 μm) air concentrations in the port of Naples. NO2 hourly average and PM10 daily average comply with European legislative standards. Spatial variation of pollutants long the axis corresponding to the prevailing wind direction seems to indicate a certain influence of ship emissions for SO2. For NO2 and PM10, a correlation between concentrations in the harbor and those measured by the air quality monitoring stations sited in the urban area of Naples was observed, indicating a possible contribution of the near road traffic to the air pollution in the port of Naples.

Modelling the dispersion and transport of reactive pollutants in a deep urban street canyon: Using large-eddy simulation

This study investigates the dispersion and transport of reactive pollutants in a deep urban street canyon with an aspect ratio of 2 under neutral meteorological conditions using large-eddy simulation. The spatial variation of pollutants is significant due to the existence of two unsteady vortices. The deviation of species abundance from chemical equilibrium for the upper vortex is greater than that for the lower vortex. The interplay of dynamics and chemistry is investigated using two metrics: the photostationary state defect, and the inferred ozone production rate. The latter is found to be negative at all locations within the canyon, pointing to a systematic negative offset to ozone production rates inferred by analogous approaches in environments with incomplete mixing of emissions. This study demonstrates an approach to quantify parameters for a simplified two-box model, which could support traffic management and urban planning strategies and personal exposure assessment.

Utilizing multiobjective analysis to determine an air quality monitoring network in an industrial district

An industrial district with polluting factories operating inside poses a potential threat to the air quality in the surrounding areas. Therefore, establishing a proper air quality monitoring network (AQMN) is essential for assessing the effectiveness of imposed pollution controls, strategies, and facilities in reducing pollutants. The geographic layout of such an AQMN should assure the quality of the monitored data. Monitoring stations located at inappropriate sites will likely affect data validity. In this study, a multiobjective approach was explored for configuring an AQMN for an industrial district. A dispersion model was employed to simulate hourly distribution of pollutant concentrations in the study area. Models optimizing pollution detection, dosage, coverage, and population protection were established. Alternative AQMNs with varied station numbers and spatial distributions were obtained using the models. The resulting AQMNs were compared and evaluated for effectiveness in monitoring the temporal and spatial variation of pollutants. Discussion of the differences among the AQMNs is provided. This multiobjective analysis is expected to facilitate a decision-making process for determining an appropriate AQMN.

A study of the dispersion and transport of reactive pollutants in and above street canyons—a large eddy simulation

Abstract This study extends a large eddy simulation model used to simulate turbulent flow in an urban street canyon to the dispersion and transport of reactive pollutants (NO, NO2 and O3). The original model, based on the regional atmospheric modelling system, has previously been validated against wind tunnel experiments for wind flow and turbulence. A real scale street canyon with an aspect ratio of one was studied with a neutrally stratified atmosphere and initial wind perpendicular to the street axis. After initialising and running the model to generate a stationary turbulent flow a constant discharge source of NOx was specified to imitate steady traffic flow through the street canyon. Line and area emissions sources for low and medium emissions of NOx were considered. A background concentration of ozone was specified and the gases were allowed to mix and react. Spatial variation of pollutants within the canyon was calculated to be significant. The photostationary state defect, ( δ ps = k [ NO ] [ O 3 ] / J NO 2 [ NO 2 ] - 1 ) , was found to be a sensitive indicator of reactive mixing within the canyon, the greater the defect the greater the local state of chemical instability. Low values for δ ps were found at the centre of the street canyon, within the primary vortex, and at the ground level corner of the windward wall, where a secondary eddy was predicted. High values were found above ground level along the windward wall, where air was entrained into the canyon along the outer edge of the primary vortex, and downstream of, and close to the NOx emission. Above the canyon a region of high δ ps corresponds to the edge of the escaping canyon plume.