Effect of sediment pH and redox conditions on degradation of benzo(a)pyrene     

R.D. Delaune  W.H. Patrick  M.E. Casselman 《Marine pollution bulletin》1981,12(7):251-253

A study was conducted using an estuarine sediment maintained under controlled pH and redox potentials to determine the effect of these parameters on the degradation of benzo(a)pyrene. Degradation was strongly influenced by sediment pH and redox potential. Highest degradation rates occurred in sediment maintained at pH 8.0 and the lowest at pH 5.0. At all pH values degradation of benzo(a)pyrene increased with increasing redox potential. Up to a hundredfold difference in degradation rates could be attributed to changes in sediment pH and redox potential.  相似文献   

Use of Cu isotopes to distinguish primary and secondary Cu mineralization in the Ca?ariaco Norte porphyry copper deposit, Northern Peru     

Ryan Mathur  Joaquin Ruiz  Michael J. Casselman  Peter Megaw  Robert van Egmond 《Mineralium Deposita》2012,47(7):755-762

A significant proportion of the copper in the Ca?ariaco Norte porphyry copper deposit in northern Peru occurs in chalcocite and covellite-rich veins and disseminations that exist from the surface to depths greater than 1?km. The overall range of Cu isotopic ratios of 42 mineral separates from Ca?ariaco varies from ?8.42 to 0.61?‰, with near-surface chalcocite and Fe oxides having isotopically depleted values compared to chalcocite, covellite, and chalcopyrite from deeper levels. The majority (34 of 36) of measured Cu sulfides have a typical hypogene copper isotope composition of δ⁶⁵Cu?=?0.18?±?0.38?‰, with no enriched isotopic signature existing in the Ca?ariaco Norte sulfide data. Thus, the copper isotope data indicate that most of the chalcocite and covellite formed from high-temperature hypogene mineralization processes and that only a minor portion of the deposit is enriched by supergene processes. The nonexistence of an enriched δ⁶⁵Cu reservoir suggest the presence of an undiscovered lateral/exotic Cu occurrence that enriched ⁶⁵Cu that remained in solution during weathering. Regardless of the cause, the comparative analysis of the Cu isotope dataset reveals that little exploration potential for an extensive supergene enrichment blanket exists because the weathering history at Ca?ariaco Norte was not conducive to preservation of enriched Cu at depth beneath the leach cap.  相似文献