Trace-elements monitoring of single rainwaters for the environmental risks assessment in the “Land of Fires” located between the provinces of Naples and Caserta

Abstract

Since rainwater chemical composition can provide valuable information on sources of local air pollution in urbanized and industrialized areas, rainwaters have been collected in the southern Plain of the region known as Campania (located between Caserta and Napoli provinces, Southern Italy). This area is characterized by the presence of heavy traffic, industries, high activity of intensive agriculture and recently sadly known as “Land of Fires” due to illegal uncontrolled burnings. Monitoring of major elements and trace elements of each single rainy event was conducted from May 2016 to January 2017 in four sampling sites long the perpendicular to the coastline, taking into account the main direction of local winds, influenced by sea breeze, to study chemical evidences. Samples were divided in the field into two aliquots: one for the analysis of anions (Cl−, NO3− and SO42−) and cations (Na+, K+, Mg2+ and Ca2+) by ion chromatography, and another one filtered and acidified for the analysis of trace elements (B, Al, Si, Mn, Fe, Cu, Zn, Rb, Sr and Ba) by ICP-MS. Moreover, electrical conductivity (EC) and pH were determined just after the rainfall by a portable instrument and total alkalinity (as HCO3−) was determined in the field by titration with 0.01 M HCl and methyl orange as indicator. Results and data processing confirm that the vertical wash-out of the atmospheric layers closest to the soil is the main mineralization process. There is also chemical evidence linked to the hardest environmental risks, probably just to the illegal uncontrolled burnings and to the agriculture activity. In fact, the maximum values of NO3− and of SO42− obtained in this study are, respectively, 51.6 mg/l and 19.5 mg/l. Moreover, sea breeze has a lavage effect, as well as morphology can save the atmospheric composition despite polluting sites closeness. Therefore, this research has tried to find an innovative experimental design in the environmental risks assessment, which may lead to differently unknown results due to the diversity of sources and/or extension and/or morphology of the territories studied. This is due to the simultaneous application of points only recently introduced in other similar studies, which are the monitoring of trace elements, of single rainfall and the study of air dynamics too through water data. This experimental design has proven to be a first step very suitable for locating and detailing the hardest environmental risks despite geographical extension and complexity of the investigated region: all the trace elements have shown high R correlations with both NO3− and SO42− for specific individuated groups of data, as well as due to the specific probable polluting processes above. In the future, there should be a study on trace elements in air to compare with the values obtained in rainwater.