title: A decadal trend study (1998-2008) of POPs in marine sediments at the south of the Southern California Bight.
abstract: In this study we present a temporal analysis of two groups of persistent organic pollutants. We compare dichlorodiphenyltrichloroethane (DDT) collected in coastal sediment samples during 1998 and 2008 at the southern end of the Southern California Bight. Other group of organochlorine compounds (OCs) compared in this decadal analysis is the polychlorinated biphenyls (PCBs). For DDTs, the most abundant isomer was dichlorodiphenyldichloroethylene DDE followed by DDT. Although no statistically significant differences in total concentration were noticeable, composition-wise some differences were still observable. The fraction parameter FDDTe=p,p'-DDT/(p,p'-DDT+p,p'-DDE) used as a measure of freshness of DDT use, is utilized here to show changes in composition. These changes are due to natural degradation of p,p-DDT under mostly oxic conditions. These changes indicate a slow transformation of DDT residues to DDE. In addition, during 1998, several stations (12 stations) showed concentrations above Effect Range Low (ERL) for the sum of DDTs while only six showed exceedance during 2008. The number of extreme values was also less frequently found in 2008 samples. For PCBs, we detected statistically significant changes, however, in both years the most abundant congeners were mostly heavy congeners (>PCB # 77) which may indicate old residues. PCBs concentrations were found in very low concentrations and do not appear to represent a danger to ecosystems. Possible explanations are offered as to the lack of observable temporal changes in concentration for DDTs in this important region.
authors.affiliation: Instituto de Investigaciones Oceanológicas, UABC, Carretera Tijuana-Ensenada No. 3917, Fraccionamiento Playitas, Ensenada CP 22860, Baja California, Mexico. Electronic address: vmacias@uabc.edu.mx.
authors.forename: J V
authors.initials: JV
authors.lastname: Macías-Zamora
authors.affiliation: Instituto de Investigaciones Oceanológicas, UABC, Carretera Tijuana-Ensenada No. 3917, Fraccionamiento Playitas, Ensenada CP 22860, Baja California, Mexico. Electronic address: nancy.ramirez@uabc.edu.mx.
authors.forename: N
authors.initials: N
authors.lastname: Ramírez-Álvarez
authors.affiliation: Instituto de Investigaciones Oceanológicas, UABC, Carretera Tijuana-Ensenada No. 3917, Fraccionamiento Playitas, Ensenada CP 22860, Baja California, Mexico. Electronic address: lsanchez@uabc.edu.mx.
authors.forename: J L
authors.initials: JL
authors.lastname: Sánchez-Osorio
mesh_terms: D002140:California; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D006843:Hydrocarbons, Chlorinated / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data*
chemical_list: D006843:Hydrocarbons, Chlorinated; D014874:Water Pollutants, Chemical
keywords: DDTs; Marine sediments; PCBs; Persistent organic pollutants; South California Bight