1,4-Dioxane biodegradation at low temperatures in Arctic groundwater samples.

1,4-Dioxane biodegradation was investigated in microcosms prepared with groundwater and soil from an impacted site in Alaska. In addition to natural attenuation conditions (i.e., no amendments), the following treatments were tested: (a) biostimulation by addition of 1-butanol (a readily available auxiliary substrate) and inorganic nutrients; and (b) bioaugmentation with Pseudonocardia dioxanivorans CB1190, a well-characterized dioxane-degrading bacterium, or with Pseudonocardia antarctica DVS 5a1, a bacterium isolated from Antarctica. Biostimulation enhanced the degradation of 50 mg L(-1) dioxane by indigenous microorganisms (about 0.01 mg dioxane d(-1) mg protein(-1)) at both 4 and 14 degrees C, with a simultaneous increase in biomass. A more pronounced enhancement was observed through bioaugmentation. Microcosms with 50 mg L(-1) initial dioxane (representing source-zone contamination) and augmented with CB1190 degraded dioxane fastest (0.16 +/- 0.04 mg dioxane d(-1) mg protein(-1)) at 14 degrees C, and the degradation rate decreased dramatically at 4 degrees C (0.021 +/- 0.007 mg dioxane d(-1) mg protein(-1)). In contrast, microcosms with DVS 5a1 degraded dioxane at similar rates at 4 degrees C and 14 degrees C (0.018 +/- 0.004 and 0.015 +/- 0.006 mg dioxane d(-1) mg protein(-1), respectively). DVS 5a1 outperformed CB1190 when the initial dioxane concentration was low (500 microg L(-1), which is representative of the leading edge of plumes). This indicates differences in competitive advantages of these two strains. Natural attenuation microcosms also showed significant degradation over 6 months when the initial dioxane concentration was 500 microg L(-1). This is the first study to report the potential for dioxane bioremediation and natural attenuation of contaminated groundwater in sensitive cold-weather ecosystems such as the Arctic.

Effect of percutaneous nephrolithotomy on differential renal function as measured by mercaptoacetyl triglycine nuclear renography.

OBJECTIVES: To determine the impact on differential renal function of percutaneous nephrolithotomy for complex renal calculi. METHODS: From July 1999 to December 2000, 45 patients underwent percutaneous nephrolithotomy. Of these, 19 agreed to participate in the study. All patients completed a quantitative assessment of differential renal function preoperatively and postoperatively with technetium 99m mercaptoacetyl triglycine nuclear renography and serum creatinine measurements. RESULTS: The mean patient age was 49 years (range 11 to 75) for the 13 female and 6 male patients. The mean stone burden was 1432 mm(2) (range 156 to 5220). The mean surgical time was 2.57 hours (range 1.17 to 5.08). The median hospital stay was 2.0 days (range 1 to 19). Of the 19 patients, 13 (68%) were stone free after one procedure. Four patients underwent ureteroscopy with stone extraction for residual fragments. One patient underwent secondary extracorporeal shock wave lithotripsy. One patient underwent nephrectomy for poor renal function. Renal function, for the entire group, increased from 36.8% preoperatively to 38.5% postoperatively. Renal function was preserved in 16 (84%) of 19 patients, including improvement of function in 7 (37%) of 19 patients. Serum creatinine was unchanged in the two groups. CONCLUSIONS: Percutaneous nephrolithotomy does not result in loss of renal function when treating complex renal calculi as measured by nuclear scintigraphy. Operative and hospitalization times were decreased compared with historical open nephrolithotomy and stone clearance was similar.