Description
Plastic debris has frequently been found in coastal and marine environments around the world. Often times, large sized plastics in coastal beaches are cleared by beach cleanup activities. However, small plastics measuring only a few millimeters in size are not easily retrieved during these clean ups. Due to the slow degradation process of plastics, plastic debris is persistent and accumulates in the marine environment often breaking down into smaller fragments. In addition to broken down fragments of plastics, pre-production plastic pellets used to manufacture various consumer products are often lost in transit or through urban runoff working their way into marine ecosystems. Plastic pellets and fragments have been found to adsorb persistent organic pollutants (POPs). POPs are well-known toxic chemicals to humans and to organisms in marine ecosystems. POPs are persistent, easily dispersed, and are derived from human activities such as the use of pesticides, additives, and combustion. Plastic pellets and plastic fragments contaminated with POPs may also act as carriers of chemicals to wildlife interfering with ecosystem food chains. POPs also have the ability to bioaccumulate throughout the food chain with the potential to reach humans raising public health concerns. This study quantifies occurrences of small plastic debris in San Diego area beaches and their contents of POPs in order to investigate the severity of the problem in this area. This is the first study in the area to be conducted involving characterization of debris and determination of environmental toxicity of plastic pellets and fragments on San Diego beaches. Sample collection was conducted from October 2009 to April 2010 at eight locations including: Torrey Pines State Beach, La Jolla Shores, Pacific Beach, Mission Beach, Mission Bay, Ocean Beach, Coronado Beach, and Imperial Beach. A standardized sampling method was utilized using 1 m_ sampling areas distributed into nine sections on Ocean Beach. Survey sampling yielded higher amounts of samples collected than that of standardized sampling. Chemical analysis was conducted and samples analyzed include small plastic fragments ranging from <5 mm to 35 mm, pellets <5 mm, polystyrene (PS) foam ranging from <5 mm to 35 mm, and rubber ranging in <5 to 50 mm in size. Factors such as weight, quantity, type, and appearance were taken into account during analysis. The chemical analysis of POPs was conducted by gas chromatography mass spectrometry. Concentrations of PAH ranged from 212 ng/g to 210 ng/g for pellets, 30 ng/g 1200 ng/g for fragments, and 310 to 1900 ng/g for PS. PCBs concentrations ranged from 4.0 ng/g to 43 ng/g in pellets, 2.5 ng/g to 47 ng/g in fragments, and non-detect to 14 ng/g for PS foam. Chlordane concentrations ranged from 1.8 ng/g to 17 ng/g in pellets, 2.0 ng/g to 21 ng/g for fragments, and 4.7 ng/g to 60 ng/g in PS foam. DDT concentrations ranged from 0.56 ng/g to 64 ng/g for pellets, non-detected to 72 ng/g for fragments, and 7.6 ng/g to 76 ng/g in PS foam. Rubber samples were excluded due to complexity of their matrices. Relatively higher PAHs and Chlordanes were found in pellets collected in Imperial Beach. Some fragments and PS foam samples contained relatively high PAH concentrations but very low concentrations of PCBs and pesticides, suggesting that plastics contain PAHs from production.
