A Geographical Information System analysis of population and occurrence of drugs along the Turia

Abstract

The Anthropocene has been proposed as a new geo-stratigraphic era where humans have become a global factor affecting the ecosystems. Drugs of abuse are widely consumed by population and continuously discharged into wastewaters as part of their elimination process. Pollution by drugs of abuse at very low concentrations appears to be broad in environmental compartments near populated areas and has been demonstrated by various national and international field studies (Senta et al., 2015; Mendoza et al., 2014). Insufficiently treated municipal wastewater is identified as the route responsible for surface water contamination. The aim of this study establishes the influence and the effects of the human pressure in a typical Mediterranean River Basin as Turia River to establish accurately the point sources of contamination and its types, through an environmental forensics methodology. A total of 42 drugs of abuse and metabolites were analysed in surface water samples collected from 31 sampling sites in distributed along the river for 2 consecutive years. Analysis of the target illicit drugs was performed following a previously method based on solid phase extraction and liquid chromatography coupled mass spectrometry (SPE-LC-MS/MS). To determine spatial incidence of drugs of abuse, analytical results of target compounds were georeferenced and integrated into a geographical information systems (GIS) together with tabular data (population census and wastewater treatment plants), GIS layers (municipal boundaries and irrigation systems) and fieldwork. In 2012, 6 compounds were detected in a total of 18 sampling points. In 2013, 8 compounds were detected in a total of 30 sampling sites, 4 of them were also detected in 2012. The compound detected more frequently along the river were benzoylecgonine (BECG) (2.91 ¿ 76.76 ng/L), a cocaine metabolite, and codeine (COD) (91.38 ¿ 101.02 ng/L), in 2012 and 2013 respectively. The application of a spatial analysis using GIS provided the spatial incidence of drugs of abuse along the Turia River Basin. Bugarra was found to have the greatest number of substances (3) in 2012 and Port de Catarroja (5) in 2013. The majority compounds detected in 2012 was BECG in 9 sampling sites and BECG and COD in 2013 both in 7 sampling sites. The patterns of spatial distribution of drugs of abuse followed a clear connectivity with population distribution and wastewater treatment plants. The most obvious trends related drugs consumption in those locations constituted by a young and little established population and higher percentage of males than females. This can be helpful to establish relation between population characteristics and anthropogenic contamination.