Occurrence and distribution of organochlorinated pesticides and flame retardants in Spain and China

Abstract

In the present thesis, analytical methods based on gas chromatography coupled with mass spectrometry, both single (GC-MS) or tandem (GC-MS/MS), have been developed and optimized for the detection and quantification of persistent organic pollutants (POPs) such as organochlorinated pesticides (OCPs) and polychlorinated byphenils (PCBs) and emerging pollutants such as organophosphate esters (OPEs), which are currently used as flame retardants, additives and plasticizers. Another family of flame retardants, also classified as POPs, polybrominated diphenil ethers (PBDEs), was also studied and quantified using already optimized and validated methods.

The presence of target POPs in environmentally protected areas of the Iberian Peninsula has been evaluated using seagull eggs as bioindicators. Two species, namely yellow-legged gull (Larus michahellis) and Audouin´s gull (Larus Audouinii), have been selected for this purpose. The former is an abundant and widely distributed species with scavenging and opportunistic behavior, while the later is more vulnerable, even though the population is growing during recent years and new colonies are emerging, and showed a strict fish-based diet. Pollution levels detected in gull eggs were dominated by PCBs, followed by various OCPs. Among OCPs, high levels of dichlorodiphenyldichloroethylene (DDE) were found, which is a metabolic and degradation product of dichlorodiphenyltrichloroethane (DDT), a pesticide widely used during the last decades of the 20th century, which showed high toxicity for birds, being able to reduce the reproduction success because it may affect the eggshell thickness and prevent hatching when present at high enough levels. PBDEs were also widespread in the marine environments of the Iberian Peninsula but at lower levels. Audouin´s gull eggs showed higher pollution levels than yellow-legged gulls from the same colonies, suggesting differences in their feeding habits and their bioaccumulation capacity of POPs. In general, Atlantic colonies were less exposed to POPs pollution than Mediterranean ones.

POPS and OPEs were also found in soil and sediment samples from four different protected areas in southern China. Protected areas such as national parks and natural reserves are of especial importance to preserve biodiversity and the natural evolution of ecosystems and are supposed to be pristine because human activities are restricted or forbidden within their geographic boundaries. However, OPEs were commonly found in the samples studied, and were the dominant pollutants, probably due to their current use and related to human activities in the surroundings of the protected areas or the touristic activities that take place within these areas. POPs were detected at lower levels than OPEs, but the alfa isomer of hexachlorocyclohexane, as well as the decabrominated PBDE congener, BDE 209, were the most frequently detected pollutants, being widespread in the environment due to their high production and consumption volumes in China during last decades.

The occurrence of POPs and OPEs was also evaluated in soils, sediments and free ranged hen eggs collected in Baihe village, Qingyuan County, Guangdong province of China. This is a hotspot for pollution, associated with electrical and electronic equipment waste (e-waste) because several non-formal workshops were set there. The disassembling of e-waste and

recovering of valuable metals became the principal economic activity at the end of the last century and beginning of the present century. Non valuable residues, mostly plastics, have been dumped for years in a little pond that was identified as the main source of pollution of the surrounding ecosystem. The migration of OPEs from the plastic dump to the water and their accumulation in the sediment of the polluted pond has been evidenced, as well as the spread of pollution to other water bodies in the same area. Moderate to high environmental risks were estimated for the presence of target pollutants in abiotic matrixes. Human consumption of free-ranged hen eggs from Baihe village was found to be a route of exposure to pollutants through the diet, posing considerable risks to human health regarding the levels of PCBs and PBDEs found.

En la presente tesis doctoral se ha estudiado la presencia y distribución de pesticidas organoclorados y retardantes de llama en áreas ambientalmente protegidas de España y China y en una zona afectada por residuos electrónicos en China.

Para ello se han desarrollado y aplicado métodos multiresiduo basados en cromatografía de gases acoplada a espectrometría de masas, tanto simple como en tándem, para la detección y cuantificación de, por un lado, contaminantes cuyo uso ha sido restringido y prohibido bajo las directrices del Convenio de Estocolmo y conocidos por sus características fisicoquímicas como compuestos orgánicos persistentes (COPs), los cuales incluyen pesticidas organoclorados (OCPs por sus siglas en inglés), bifenilos policlorados (PCBs) y polibromodifenil éteres (PBDEs) y, por otro lado, una familia de contaminantes emergentes utilizados como plastificantes, aditivos y retardantes de llama como son los ésteres organofosforados (OPEs).

En España, el estudio de COPs se ha llevado a cabo mediante el uso de huevos de gaviota como bioindicadores de la contaminación ambiental y se han evaluado los niveles de estos compuestos antropogénicos en las mayores colonias de gaviotas de la península Ibérica, constituidas en zonas con diferentes grados de protección ambiental. Los compuestos detectados a mayor nivel fueron los OCPs, y más en concreto el dicloro difenil tricloroetano (DDT) y sus productos de degradación, seguidos por los PCBs y a menores niveles los PBDEs.

En China, se ha detectado la presencia tanto de COPs como de OPEs en suelos y sedimentos de zonas protegidas como parques nacionales y/o reservas naturales que, en principio, deberían ser prístinas. Los contaminantes detectados a mayores niveles fueron los OPEs, probablemente debido a su uso actual. Sin embargo, el isómero alfa del hexaclorociclohexano, así como el PBDE 209 demostraron ser ubicuos en el medio ambiente, lo cual concuerda con los grandes volúmenes de producción y consumo de los mismos en el país asiático.

Los OPEs fueron identificados a muy elevadas concentraciones en aguas, suelos, sedimentos y huevos de gallina muestreados en Baihe, un pueblo del sur de China cuya principal actividad económica ha sido, durante las últimas décadas, el reciclaje de residuos electrónicos para la recuperación de metales valiosos. Esta actividad ha conllevado la acumulación de plásticos en un pequeño lago, que se ha identificado como la fuente de contaminación de los compartimentos ambientales del ecosistema. PCBs y PBDEs también se detectaron a elevadas concentraciones en suelos y sedimentos, e incluso en huevos lo cual permitió identificar riesgos, no sólo ambientales, sino también para la salud humana.