Mapping anthropogenic and natural volatile organic compounds around estarreja chemical industrial complex

Abstract

In the region of Estarreja, since the middle of century XX has settled one of the largest complexes of basic chemical industries in Portugal. During the 80s of the last century, the air quality started to be monitored in this region, but only the classic pollutants were addressed. This region never was submitted to a VOC survey, a group of compounds together NOx with a strong impact in ozone production at surface level. Every year ozone exceedances are observed in this region. Adding to this environmental problem, volatile organic compounds include several compounds with negative human health effects, like aromatic compounds. Due to a complexity of sources, industrial, traffic, agriculture and natural, that can drive air quality in the region, field campaigns were planned involving VOCs and NO2 measurements with passive tubes. A set of passive tubes were distributed for 32 sampling locations in an area of ~100 km2. Radiello passive tubes and Palmes type tubes were used for VOCs and NO2 concentration measurements respectively. Four sampling campaigns with a weekly duration were performed between March and June 2012. The values obtained show that toluene was the VOC (C5 to C12), which in general, showed higher concentrations in all campaigns. The highest concentrations of many VOCs like BTEX, and NO2 were observed close to the vicinity of the industrial complex. The high ratio of toluene/benzene pinpoint a heavy influence by emissions from industry, even the ratio of xylene/benzene suggests that this region is also influenced by transport of pollutants from other regions. The high correlations between the xylenes and ethylbenzene in the entire area indicate a single emission source, most likely vehicular emissions, in opposition to what isobserved for toluene and benzene. The analysis of the PEC (Propylene Equivalent Concentration) reveals that the biogenic VOCs presents a potential for ozone formation greater than the anthropogenic emissions.