Carl J. Mohrherr

Trace metal assessment in soils in a small city and its rural surroundings, Pensacola, FL, USA

This study assesses the origin and pollution of trace metals in surface soils in a region with contrasting land uses (urban vs. rural). Principal component analysis (PCA) reveals that Cr and Ni are predominantly of geogenic origin. These two trace metals are also the only ones with statistically significant correlations with soil particle size and organic matter content. Copper, Pb and Zn, and possibly Hg, are of anthropogenic origin, but their concentrations rarely reach levels described as strongly polluted by pollution indexes. The concentrations of these anthropogenic trace metals are statistically not different in urban and rural areas, except for Pb that is higher in the urban area. This general lack of a difference between the two land uses indicates that the influence of this small urban area on trace metal concentrations in soils is minor. Lead and Zn have the most, but still a modest number, of strongly polluted sites, mainly in an industrial part of the city. GIS analysis shows that, based on the pollution load index (PLI), overall concentrations of trace metals also reach their highest levels in that industrial area. These observations indicate that the influence of industry on trace metal pollution in soil exceeds that of other urban activities in the region. Local background concentrations were found to be very different from general crustal background concentrations. This demonstrates the importance of the careful selection of a background type in studies like this.

Polychlorinated Biphenyl (PCB) Profiles, Degradation, and Aroclor Origin in Sediments of Escambia Bay, Florida

Polychlorinated biphenyls (PCBs) are anthropogenic substances that have been detected in many parts of the environment and can have major negative impacts on ecosystem and human health. A documented release of PCBs from a nylon plant occurred in 1969 on the Escambia River just upstream of the Escambia Bay estuary along the north coast of the Gulf of Mexico. Other unreported releases of PCBs also likely occurred in the river and bay. The present study sampled sediments in the river and bay and assessed the predominant parent Aroclor of PCBs, and the changes in congener profile and toxic equivalents (TEQ) since the release. United States Environmental Protection Agency (US EPA) method 1668A, which provides quantitative data for 168 elutions, was employed for the analysis according to National Environmental Laboratory Accreditation Program procedures. Correlation analysis and principal component analysis of the PCB congener profiles for the sediments and Aroclors showed that the sedimentary PCB congeners are most similar to that of early production Aroclor 1254 made prior to 1971. Chronologically the use of the early production Aroclor 1254 corresponds to the time of the release. Since the release, overall chlorination of the sedimentary PCBs has decreased by 3% as a result of a shift in chlorination homolog profile to lesser-chlorinated congeners that presumably originated from dechlorination of Aroclor PCBs and from non-Aroclor source(s) of PCB 11, a dichlorobiphenyl. Despite a likely overall decrease in the quantity of dioxin-like PCBs, the TEQ/mole of sediment PCBs, did not substantially change because of a highly toxic congener (PCB 126) that was present at trace amounts in the sediments. There was a modest increase in lesser-chlorinated O,P-congeners that are suspected to have some toxicity to mammals. These findings have relevance for the evolution of environmental PCBs, which has not been studied in this system.

Research Article: DDT, Dioxins, and PCBs in Sediments in a Historically Polluted Estuary along the Gulf of Mexico

This study assessed current profiles of organochlorine pollutants in sediment of Escambia Bay and River in northwest Florida, United States (US), which experienced catastrophic environmental collapse in the 1970s as a result of unregulated industrial and domestic sewage releases. Fifty-seven composite sediment samples were collected with a ponar grab sampler. Organochlorines were extracted with United States Environmental Protection Agency (USEPA) Method 3550 and concentrations were determined with USEPA Method 1668A for polychlorinated biphenyls (PCBs), USEPA Method1613B for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and USEPA Method 8081A for 4,4′-dichlorodiphenyltrichloroethane (DDT), 4,4′-Dichlorodiphenyldichloroethane (DDD), and 4,4′-Dichlorodiphenyldichloroethylene (DDE). For PCBs, 12 (21%) out of the 57 samples exceed the Florida threshold effects level (TEL) of 21.6 μg/kg and no sample exceeds the Florida probable effects level (PEL) of 189 μg/kg. The 17 PCDD/F congeners that are considered to have significant toxicity have a mean of 1.9 μg/kg and a range of 0.022–11 μg/kg. The mean total toxic equivalence value (TEQ) of PCDD/Fs and dioxin-like PCBs for the sediments is 2.6 ng/kg. About 56% of the samples exceed the US National Oceanic and Atmospheric Administration (NOAA) TEL for total TEQ, 23% of which also exceed the NOAA TEL, implying that these total TEQ toxicities can impact sediments adversely. DDT was detected in 25% of the samples. All but one of the detections were in the river and adjacent wetlands. The detected DDT concentrations exceed the Florida PEL (4.77 μg/kg) except for one sample that only exceeds the TEL (1.19 μg/kg). The common DDT degradation products, DDD and DDE, were not detected in the river and wetland sediments.