Evaluation of pyrene sorption–desorption on tropical soils

Sorption–desorption processes control soil-pollutant interactions. These processes determine the extent of pyrene transport in soils. Understanding sorption characteristics of pyrene is necessary in ascertaining its fate in soil. Laboratory batch experiments were conducted to study the sorptions–desorption of pyrene on eight soils from varying tropical agro-ecological zones (AEZs). The results showed that pyrene sorptions equilibria were attained within 720 min. Solution pH had a reciprocal effect on pyrene sorptions. Sorption was exothermic and increased with pyrene concentration in solution. The quantities of pyrene sorbed by each soil as well as the hysteresis were proportional to the percentage organic matter, and to some degree, the clay mineralogy. Sorption isotherms showed distributed reactivity involving several linear and non-linear isotherms. The present investigation showed that pyrene is likely to be more available to biota and reach the aquifer faster in low organic matter soils than those with relatively higher organic matter and more so in warmer climes

Spatial variation in the accumulation of POPs and mercury in bottlenose dolphins of the Lower Florida Keys and the coastal Everglades (South Florida)

The bottlenose dolphin (Tursiops truncatus) is an upper trophic level predator and the most common cetacean species found in nearshore waters of southern Florida, including the Lower Florida Keys (LFK) and the Florida Coastal Everglades (FCE). The objective of this study was to assess contamination levels of total mercury (T-Hg) in skin and persistent organic pollutants (PCBs, PBDEs, DDXs, HCHs, HCB, Σ PCDD/Fs and Σ DL-PCBs) in blubber samples of bottlenose dolphins from LFK (n = 27) and FCE (n = 24). PCBs were the major class of compounds found in bottlenose dolphin blubber and were higher in individuals from LFK (Σ 6 PCBs LFK males: 13421 ± 7730 ng.g-1 lipids, Σ 6 PCBs LFK females: 9683 ± 19007 ng.g-1 lipids) than from FCE (Σ 6 PCBs FCE males: 5638 ng.g-1 ± 3627 lipids, Σ 6 PCBs FCE females: 1427 ± 908 ng.g-1 lipids). These levels were lower than previously published data from the southeastern USA. The Σ DL-PCBs were the most prevalent pollutants of dioxin and dioxin like compounds (Σ DL-PCBs LFK: 739 ng.g-1 lipids, Σ DL-PCBs FCE: 183 ng.g-1 lipids) since PCDD/F concentrations were low for both locations (mean 0.1 ng.g-1 lipids for LFK and FCE dolphins). The toxicity equivalences of PCDD/Fs and DL-PCBs expressed as TEQ in LFK and FCE dolphins is mainly expressed by DL-PCBs (81% LFK - 65% FCE). T-Hg concentrations in skin were significantly higher in FCE (FCE median 9314 ng.g-1 dw) compared to LFK dolphins (LFK median 2941 ng.g-1 dw). These bottlenose dolphins concentrations are the highest recorded in the southeastern USA, and may be explained, at least partially, by the biogeochemistry of the Everglades and mangrove sedimentary habitats that create favourable conditions for the retention of mercury and make it available at high concentrations for aquatic predators.Florida Coastal Everglades LTER Program (DBI0620409, DEB9910514, DRL0959026); Florida International University’s Marine Sciences Progra