- Email: [email protected]
Uptake rate and efficiency of uptake of hexachlorobenzene from water and sediment by tellinid clam, Macoma nasuta
120
Abstracts
thought to be the causative factors in a number of neoplastic and other pathological disorders. Studies on metabolism of PAHs, both in mammals and in aquatic species, have either relied on in vitro metabolic studies using microsomes or a reconstituted cytochrome P-450 enzyme system, or on in vivo studies involving PAH administration followed by collection and hydrolysis of metabolite conjugates. The metabolites are usually extracted then analyzed by high-performance liquid chromatography (HPLC), or metabolites are derivatized and analyzed by capillary gas chromatography (capillary GC) and capillary GC/mass spectrometry (capillary GC/MS). Direct analysis of conjugates of PAH metabolites has not been an attractive technique so far, primarily because of a lack of sophistication in HPLC separation and HPLC/MS. In our institute, HPLC has been successfully interfaced with a quadrupole MS. A number of benzo[a]pyrene metabolites have been analyzed by HPLC/chemical ionization MS using direct liquid introduction and thermospray interfaces. We have also developed conditions for the HPLC separation of conjugates of PAH metabolites.
Uptake Rate and Efficiency of Uptake of Hexaehlorobenzenefrom Water and Sediment by TeHinid Clam, M a c o m a nasuta. B. L. BOESE, H. L E E II, D. T. SPECHT & R. C. RANDALL. US Environmental Protection Agency, Mark Hatfield Marine Science Center, Newport, Oregon 97365, USA. The rate and efficiency uptake of a fungicide, 14C-hexachlorobenzene (HCB), from water and sediment by a deposit-feeding clam (Macoma nasuta) was examined. Efficiency was defined as the percent of HCB extracted from water by the gills, or from sediment by the gut. An exposure chamber (clambox) that separated the inhalant and exhalant siphons allowed the collection of fecal pellets and ventilated water. For HCB water exposures, clams were exposed to one of three temperatures (12, 17 or 22°C) to vary the ventilation rate of the clams. Whole-body HCB extraction efficiency from water (EPW) averaged 82%. After correcting for sorption to surface tissues, gill EPW averaged 65% and did not decrease with increasing ventilation rate. HCB tissue residues were strongly related (R a =0"93) to the total amount of HCB that passed over the gills. These results indicate that environmental factors which increase ventilation rate, such as low oxygen concentrations, would result in a more rapid uptake and, possibly, a greater equilibrium body burden of contaminants such as HCB. In sediment exposures, clams were exposed to clean water and either to a fine (< 0-125 mm) or a bulk (0.125-1.0 mm) sediment fraction labeled with 14CHCB. Fecal pellets were collected from the exhalant side of the clambox. The clams accumulated significant amounts of HCB, indicating that the particle-
Abstracts
121
associated HCB was bioavailable to the clams. However, HCB tissue residues were not significantly correlated with the sediment processing rate, though they were positively correlated with the concentration of HCB in the voided fecal pellets. These results indicate that although HCB was taken up from the sediment, there was considerable variation among clams in the HCB concentration on the particulates they ingested. This particulate selectivity by the clams makes it difficult to calculate an efficiency of uptake from sediments (EPS).
Abstracts
thought to be the causative factors in a number of neoplastic and other pathological disorders. Studies on metabolism of PAHs, both in mammals and in aquatic species, have either relied on in vitro metabolic studies using microsomes or a reconstituted cytochrome P-450 enzyme system, or on in vivo studies involving PAH administration followed by collection and hydrolysis of metabolite conjugates. The metabolites are usually extracted then analyzed by high-performance liquid chromatography (HPLC), or metabolites are derivatized and analyzed by capillary gas chromatography (capillary GC) and capillary GC/mass spectrometry (capillary GC/MS). Direct analysis of conjugates of PAH metabolites has not been an attractive technique so far, primarily because of a lack of sophistication in HPLC separation and HPLC/MS. In our institute, HPLC has been successfully interfaced with a quadrupole MS. A number of benzo[a]pyrene metabolites have been analyzed by HPLC/chemical ionization MS using direct liquid introduction and thermospray interfaces. We have also developed conditions for the HPLC separation of conjugates of PAH metabolites.
Uptake Rate and Efficiency of Uptake of Hexaehlorobenzenefrom Water and Sediment by TeHinid Clam, M a c o m a nasuta. B. L. BOESE, H. L E E II, D. T. SPECHT & R. C. RANDALL. US Environmental Protection Agency, Mark Hatfield Marine Science Center, Newport, Oregon 97365, USA. The rate and efficiency uptake of a fungicide, 14C-hexachlorobenzene (HCB), from water and sediment by a deposit-feeding clam (Macoma nasuta) was examined. Efficiency was defined as the percent of HCB extracted from water by the gills, or from sediment by the gut. An exposure chamber (clambox) that separated the inhalant and exhalant siphons allowed the collection of fecal pellets and ventilated water. For HCB water exposures, clams were exposed to one of three temperatures (12, 17 or 22°C) to vary the ventilation rate of the clams. Whole-body HCB extraction efficiency from water (EPW) averaged 82%. After correcting for sorption to surface tissues, gill EPW averaged 65% and did not decrease with increasing ventilation rate. HCB tissue residues were strongly related (R a =0"93) to the total amount of HCB that passed over the gills. These results indicate that environmental factors which increase ventilation rate, such as low oxygen concentrations, would result in a more rapid uptake and, possibly, a greater equilibrium body burden of contaminants such as HCB. In sediment exposures, clams were exposed to clean water and either to a fine (< 0-125 mm) or a bulk (0.125-1.0 mm) sediment fraction labeled with 14CHCB. Fecal pellets were collected from the exhalant side of the clambox. The clams accumulated significant amounts of HCB, indicating that the particle-
Abstracts
121
associated HCB was bioavailable to the clams. However, HCB tissue residues were not significantly correlated with the sediment processing rate, though they were positively correlated with the concentration of HCB in the voided fecal pellets. These results indicate that although HCB was taken up from the sediment, there was considerable variation among clams in the HCB concentration on the particulates they ingested. This particulate selectivity by the clams makes it difficult to calculate an efficiency of uptake from sediments (EPS).