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Articles by Dennis A. Apeti
Total Records ( 3 ) for Dennis A. Apeti
  Dennis A. Apeti , Larry Robinson and Elijah Johnson
  This study aims to assess baseline concentrations of heavy metals (Cd, Cr, Cu, Pb and Zn) in the oyster soft tissue as they relate to concentrations in the water column (particulate phase) and sediment in Apalachicola Bay. In order to conduct these assessments, a total of 360 samples, collected in two seasons (winter and summer) and were analyzed using atomic absorption spectrometry. Results indicated that elemental concentrations in particulate phase correlate significantly with concentration in the tissue than those in the sediment. Moreover, assessment of seasonal and spatial variations have indicated that oysters collected in the winter have significantly higher (P<0.05) Cu, Pb and Zn concentrations than oysters collected in the summer. However, metal concentrations in sediment did not show such patterns. These observations confirmed the fact that metals in the particulate phase are more bioavailable to oysters and that the oysters can be used as good indicators of the spatial and temporal variation of the heavy metals in the aquatic system.
  Dennis A. Apeti , Elijah Johnson and Larry Robinson
  Kinetics of bioaccumulation of the trace metals (Cd and Zn) by C. virginica were investigated in this study. A computer program, Oyster Bioaccumulation Model (OBM), was developed to simulate the accumulation of the metals from both dissolved (water column) and particulate (food) phases by C. virginica. The model is based on two main attributes: (1) the oyster biological characteristics such as gill morphometry, feeding growth rate, respiration rate and lipid composition and (2) the physicochemical properties of metals, which include aqueous diffusivity and partition coefficients. For some data from Chesapeake bay, simulation results compared well with field results. Predicted Bioaccumulation Factor (BAF) parameters (1.5 x 104 for Cd and 6.6 x 104 for Zn) for Apalachicola Bay show that elemental concentrations in C. virginica are up to 4 orders of magnitude greater that that of the water column. Furthermore, the model is shown to be flexible enough to be utilized in other estuaries.
  Dennis A. Apeti and Gunnar G. Lauenstein
  Mirex is a persistent and toxic polychlorinated pesticide that has compromised environmental quality in the Great Lakes region since the 1960s. As a bioaccumulative and carcinogenic compound, mirex at its current levels in Lake Ontario is a concern because of the potential for trophic level transfer and biomagnification in top predators. As a part of the NOAA’s National Status and Trends Program (NS&T), zebra mussels and surficial sediments were surveyed throughout the Great Lakes since 1992 to monitor a broad suite of contaminants, including mirex. The non-parametric Wilcoxon test revealed that Lake Ontario consistently had the highest mirex concentrations (p < 0.0054) followed by Lake Erie while Lakes Huron and Michigan had the lowest concentrations. Current concentrations of mirex at Lake Ontario sites are at or above the NS&T benchmark of 85th percentile (2.33 ng gˉ1 dry weights) determined among all sites in the Great Lakes. The Spearman correlation statistic revealed an overall decreasing trend in tissue concentration, but this decline is only significant in Lake Ontario (p< 0.02) over the monitoring period 1992-2004. Photodegradation, volatilization, fishing and loss via the St Lawrence River are discussed as mechanisms resulting in the mirex decline.
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