Probing the debromination of the flame retardant decabromodiphenyl ether in sediments of a boreal lake.

After decades of use of polybrominated diphenyl ethers (PBDEs) as flame retardants, a large reservoir of these toxins has accumulated in ecosystems worldwide. The present study used an innovative approach to examine whether the fully brominated PBDE decabromodiphenyl ether (decaBDE) degrades to more toxic congeners in aquatic environments. The authors incubated intact sediment microcosms with high-purity [(13)C]decaBDE in a remote boreal lake to assess its debromination under ambient conditions. Although the addition of [(13)C]decaBDE increased total PBDE concentrations in sediment more than 10-fold, the relative amount of [(13)C]decaBDE in sediment did not change significantly over a 1-mo incubation. However, observation of small quantities of lower-brominated [(13)C]BDEs lent support to the hypothesis that decaBDE is slowly debrominated. The authors observed a significant increase in octaBDEs and nonaBDEs in profundal, but not littoral, sediment over 30 d. A second experiment in which sediment was incubated under different light and oxygen regimes yielded a surprising result-oxygen significantly stimulated the formation of octaBDEs and nonaBDEs. The authors also conducted a large-scale in situ enclosure experiment in which they followed the fate of experimentally added decaBDE in sediment over 26 mo, but that study yielded little evidence of decaBDE debromination. Overall, the authors suggest that the debromination of decaBDE occurs very slowly, if at all, in natural sediment of boreal lakes, in contrast to the rapid degradation kinetics reported by most laboratory-based studies, which are usually conducted by dissolving decaBDE in organic solvents. The findings reinforce the need for field studies on contaminant fate to inform environmental policy decisions.

Lead bioaccumulation in earthworms, Lumbricus terrestris, from exposure to lead compounds of differing solubility.

This study examined the relative effects of soluble and less soluble Pb compounds on Pb accumulation by Lumbricus terrestris. The earthworms were exposed to composted cattle manure contaminated with a range of concentrations of either soluble lead acetate trihydrate (PbAc) (14.5, 72.2, 137, 257, and 603 microg/g) or less soluble lead carbonate (Pb(CO(3))(2)) (5.09, 171, 575, and 710 microg/g). Relative Pb bioaccumulation rates in earthworms from the PbAc and Pb(CO(3))(2) lead carbonate trials were compared over time (0, 20, 40, and 60 days). The two molecular forms of Pb were heavily adsorbed onto the organic matter. Relative soluble Pb concentrations in the manure pore water were very low, at 0.049% and 0.022% of total Pb for PbAc and Pb(CO(3))(2), respectively. There was a significant uptake of lead by earthworms from both the readily soluble and less soluble forms of Pb. Regression surfaces relating organic matter total Pb concentration to exposure time and Pb body burden were compared. For the PbAc trial, the following equation was fitted: Body burden=2.3429+0.0014 x--0.0632 y+0.0008 xy (R(2)=0.8494, p<0.0001). For the Pb(CO(3))(2) trial, the equation was: Body burden=-2.0760--0.0067 x-0.2297 y-0.0038 y(2)+0.0003 xy (R(2)=0.5686, p<0.0001) (for x=organic matter Pb concentration in microg/g and y=time in days). The Pb bioaccumulation resulting from the PbAc exposure was significantly higher than that from Pb(CO(3))(2). Body burdens of earthworms exposed to PbAc were linearly related to exposure time and total Pb concentration. Worms exposed to Pb(CO(3))(2) had non-linear Pb accumulation over time that suggested a decrease in Pb bioavailability with increasing exposure time. The results indicate that L. terrestris feeding on detritus in the upper soil levels can mobilize and accumulate Pb from the principal transformation products of metallic Pb, as at shooting ranges and lead smelter sites.

The distribution of outdoor shooting ranges in Ontario and the potential for lead pollution of soil and water.

The distribution of outdoor shotgun shooting ranges in Ontario was determined to assess their potential for contributing to lead contamination of soil and water. Provincial soil maps were used to identify the soil type(s) occurring on each range, and to record their soil pH, organic matter content and clay content. Topographic maps (scale 1:50000) were used to identify any surface waters that existed on each range. At least 211 active shooting ranges exist in Ontario, of which 135 cater to shotgun sports. This number far exceeds earlier estimates. Soil pH data existed for 67 ranges, of which 50 had soil pH values >or=6.0, and 17 had pH values less than 6.0. Data for organic matter and or clay content were available for only 59 ranges. Approximately 10% of the ranges are on soils with low levels of both clay and organic matter. Seven of these ranges had a combination of low pH, and low clay and organic matter content, suggesting that they have a high potential for lead dissolution and mobilization. Surface waters that could potentially receive shot fall-out occurred on 94% of the ranges surveyed, although the precise location of the water with respect to the shot fall area at each range could not be determined. The majority of shooting ranges in the province occur on luvisolic soils: most of the ranges with a higher potential for lead solubilization occur on podzolic and brunisolic soils. This indirect approach to assessing the potential for lead pollution and mobility at shooting ranges allows a large number of ranges to be examined quickly, so that ranges with a high potential for lead contamination of soil and water can be selected for on-site measurements. This broad scale approach has allowed for the first time the point loading of metallic lead into the Ontario environment from shooting ranges to be determined, as well as the locations of ranges that may warrant investigation of lead pollution.