Quantifying the effects of fumarate on in situ reductive dechlorination rates

In situ methods are needed to evaluate the effectiveness of chemical amendments at enhancing reductive dechlorination rates in groundwater that is contaminated with the priority pollutant, trichloroethene (TCE). In this communication, a method that utilizes single-well, “push–pull” tests to quantify the effects of chemical amendments on in situ reductive dechlorination rates is presented and demonstrated. Five push–pull tests were conducted in each of five monitoring wells located in a TCE-contaminated aquifer at the site of a former chemical manufacturing facility. Rates for the reductive dechlorination of the fluorinated TCE-surrogate, trichlorofluoroethene (TCFE), were measured before (test 1) and after (test 5) three successive additions (tests 2–4) of fumarate. Fumarate was selected to stimulate the growth and activity of indigenous microorganisms with the metabolic capability to reduce TCFE and TCE. In three wells, first-order rate constants for the reductive dechlorination of TCFE increased by 8.2–92 times following fumarate additions. In two wells, reductive dechlorination of TCFE was observed after fumarate additions but not before. The transformation behavior of fumarate was also monitored following each fumarate addition. Correlations between the reductive dechlorination of TCFE and the reduction of fumarate to succinate were observed, indicating that these reactions were supported by similar biogeochemical conditions at this site.     

Exposure of insects and insectivorous birds to metals and other elements from abandoned mine tailings in three Summit County drainages, Colorado

Concentrations of 31 metals, metalloids, and other elements were measured in insects and insectivorous bird tissues from three drainages with different geochemistry and mining histories in Summit Co., Colorado, in 2003, 2004, and 2005. In insect samples, all 25 elements that were analyzed in all years increased in both Snake and Deer Creeks in the mining impacted areas compared to areas above and below the mining impacted areas. This distribution of elements was predicted from known or expected sediment contamination resulting from abandoned mine tailings in those drainages. Element concentrations in avian liver tissues were in concordance with levels in insects, that is with concentrations higher in mid-drainage areas where mine tailings were present compared to both upstream and downstream locations; these differences were not always statistically different, however. The lack of statistically significant differences in liver tissues, except for a few elements, was due to relatively small sample sizes and because many of these elements are essential and therefore well regulated by the bird's homeostatic processes. Most elements were at background concentrations in avian liver tissue except for Pb which was elevated at mid-drainage sites to levels where delta-aminolevulinic acid dehydratase activity was inhibited at other mining sites in Colorado. Lead exposure, however, was not at toxic levels. Fecal samples were not a good indication of what elements birds ingested and were potentially exposed to.