By: Roger Renstrom
January 16, 2013
SAN DIEGO -- A marine biology doctoral candidate's study found that pellets of polyethylene and polypropylene absorbed more organic contaminants than PET or PVC during submersion in the waters of San Diego Bay.
Concern about marine plastic pollution was a driver for the study.
Chelsea Rochman and another student, Shawn Kaye, deployed mesh bags with pellets of high density and low density PE, PP, PET and PVC at five locations and retrieved the material at varying intervals over 12 months ended June 2010. Portions of the 250 samples were studied at one, three, six, nine and 12 months.
The researchers extracted chemicals from the commodity thermoplastics and used gas chromatography and mass spectrometry techniques with equipment from Agilent Technologies Inc. of Santa Clara, Calif., to measure, in particular, the presence of polychlorinated biphenyls and polycyclic aromatic hydrocarbons. HDPE, LDPE and PP pellets continued to absorb contaminants throughout the 12 months and in greater concentrations than PET and PVC.
Locations included five docks and piers around the bay for San Diego harbor excursions, the Shelter Island neighborhood, Scripps Institution of Oceanography's Nimitz marine facility, the Coronado Cays community and the City of Chula Vista. Despite location variability, Rochman found relative differences in PCB and PAH sorption among the five polymers were consistent over space and time.
The study also measured the presence of metals absorbed into the pellets. "We are working on writing about them," Rochman said.
The website of the American Chemical Society's Environmental Science & Technology journal posted the nine-page study results on Dec. 27.
The National Science Foundation's graduate research fellowship program in Washington provided funds for the study with additional support from the Society of Environmental Toxicology and Chemistry of Pensacola, Fla., San Diego State University's research foundation and the PADI Foundation of Beverly Hills, Calif.
Rochman estimated about $20,000 was expended excluding internship stipends and other salaries.
Rochman, whose family lives in Tucson, Ariz., is pursuing a joint doctoral degree in marine biology from the University of California, Davis and San Diego State University.