Levels of drugs of abuse in superficial waters of the Oliva-Pego marsh (Valencia, Spain)

Abstract

The use of drugs of abuse is increasing worldwide and causes not only a well-known serious social problem but also concern as environmental emerging contaminants. Data provided by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) estimate that, in the last year, 22.5 million Europeans (between 15 and 64 years) smoked cannabis (22% of European adults), 12 million sniffed cocaine, 11 million took amphetamines and 9.5 million took ecstasy. Regarding opiates, the report did not show a decline in the epidemic problems linked to heroin. Drugs of abuse are excreted unmetabolized or as metabolites in urine and feces, in fact, most consumed ones have been determined in the sewage systems and in natural waters [1,2]. However, due to the limited extent of research undertaken in this field, there is limited data and minimal understanding of the environmental occurrence, transport, fate and exposure for these compounds. One of the most important environments in the Mediterranean areas of Spain are saltmarshes. The aim of the present work is to expand the range of Spanish wetlands investigated to the Oliva-Pego marsh. This area, with an approx. area of 1,290 ha, is found in the extreme south of the Gulf of Valencia, bounded to the north by the Mustalla mountains and the Bullent river, bounded to the east by the alluvial delta of the Pego plain and to the west by the Mediterranean Sea. In order to check the levels of drugs of abuse, twenty-three samples were taken in this wetland, on April 2009. Samples were taken from the lagoon and from the most important channels that flow in itself. A simple and robust method using solid-phase extraction (SPE) and liquid chromatography tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of 14 drugs of abuse and their metabolites (cocainics, amphetamine-like compounds, cannabinoids, and opiates) in surface waters was developed. The highest recoveries, as well as the simplest protocol, were obtained for Oasis HLB cartridges (6 mL/200 mg) using 250 mL of water. The proposed method was linear in a concentration range from 0.03¿6 ng/L to 300¿60,000 ng/L depending on the compound, with correlation coefficients higher than 0.998. Matrix effects have been studied in surface water samples, and several isotope-labelled internal standards have been evaluated as a way to compensate the signal suppression observed. Limits of quantification (LOQs) ranged from 0.03 to 5.13 ng/L, respectively. Recoveries were 71¿102% at the LOQ level and 77¿104 at 50 ng/L. Many of the tested substances were found at concentrations in the range of ng/L. The results of these samples confirmed that the method is suitable for screening these compounds in the environment, highlighting the convenience to carry out a better treatment of residual waters before its discharge in the environment.