Shrnutí

Popis

In the springs of 1992 and 1993 ten clutches of wood duck eggs were collected from the lower Roanoke River below a kraft process pulp paper mill that had historically bleached with molecular chlorine. In addition, one clutch was collected from Pocosin Lakes National Wildlife Refuge PDNWR, a site with no known history of dioxin contamination. Embryos only, with no yolk sacs, and a limited number of companion yolk sacs were analyzed for the seventeen 2,3,7,8substituted polychlorinated dibenzodioxins PCDDs and polychlorinated dibenzofurans PCDFs. The 2,3,7,8tetrachlorodibenzopdioxin 2,3,7,8TCDD isomer was found in all eggs sampled from the Roanoke River 0.32 to 26.6 pgg wet weight but was not detected in the sample from PLNWR 0.15 pgg. The 2,3,7,8tetrachlorinated dibenzofuran 2,3,7,8TCDF isomer was detected in all samples from the Roanoke River 0.92 to 393 pgg as well as the sample from PLNWR 1.6 pgg. We calculated 2,3,7,8TCDD equivalencies TEQs using the international toxicity equivalency factors ITEFs. TEQs were calculated for embryos and yolk sacs; a regression curve was derived to predict yolk sac TEQs in the samples for which only embryos were analyzed. Total TEQs approximated for two whole eggs 22 and 82 pgg were within a range reported in the literature as deleterious to wood ducks 2050 pgg. Liver monooxygenase activities of three dealkylases, benzyloxyresorufinOdealkylase BROD, ethoxyresorufinOdealkylase EROD, and methoxyresorufin0dealkylase MROD, were induced in some clutches for the Roanoke River but not in all clutches. The hatching success of two nests were below 75, the remainder ranged from 75 to 100. Three clutches had 10day survival rates below 75, the others ranged from 75 to 100. No relationship was found between hatching success or survivorship and PCDDPCDF burdens. One embryo had multiple deformities including being a conjoined twin, a bill deformity and exencephaly. Although the deformities observed are consistent with those that can be caused by dioxin, available data do not indicate that dioxins were a causative factor. Data indicate that enticing wood ducks to nest boxes within two kilometers downstream of the mill may not be prudent. The areal extent of habitat adjacent to the mill where concentrations of PCDDs and PCDFs may cause eggs to exceed reproductive effects levels should be determined along with a characterization of the diversity and abundance of waterfowl and other avian species at risk in the immediate vicinity.