A study of presolar material in hydrated lithic clasts from metal-rich carbonaceous chondrites
METEORITICS & PLANETARY SCIENCE
Authors: Leitner, Jan; Hoppe, Peter; Zipfel, Jutta
Abstract
We report on the investigation of presolar grain inventories of hydrated lithic clasts in three metal-rich carbonaceous chondrites from the CR clan, Acfer 182 (CH3), Isheyevo (CH3/CB(b)3), and Lewis Cliff (LEW) 85332 (C3-un), as well as the carbon- and nitrogen-isotopic compositions of the fine-grained clast material. Eleven presolar silicate grains as well as nine presolar silicon carbide (SiC) grains were identified in the clasts. Presolar silicate abundances range from 4 to 22 parts per million (ppm), significantly lower than in pristine meteorites and interplanetary dust particles (IDP), and comparable to recent findings for CM2s and CR2 interchondrule matrix. SiC concentrations lie between 9 and 23ppm, and are comparable to the values for CI, CM, and CR chondrites. The results of our investigation suggest similar alteration pathways for the clast material, the interchondrule matrix of the CR2 chondrites, and the fine-grained fraction of CM2 chondrites. Fine-grained matter of all three meteorites contains moderate to high N-15-enrichments (similar to 50 parts per thousand N-15 similar to 1600 parts per thousand) compared to the terrestrial value, indicating the presence of primitive organic material. We observed no correlation between N-15-enrichments and presolar dust concentrations in the clasts. This is in contrast to the findings from a suite of primitive IDPs, which display in several cases enhanced bulk N-15/N-14 ratios and high presolar grain abundances of several hundred or even thousand ppm. The bulk N-15/N-14 ratios of the clasts are comparable to the range for primitive IDPs, suggesting a nitrogen carrier less susceptible to destruction by aqueous alteration than silicate stardust.
Assessment of the heavy metal bioremediation efficiency of the novel marine lactic acid bacterium, Lactobacillus plantarum MF042018
SCIENTIFIC REPORTS
Authors: Ameen, Fatma A.; Hamdan, Amira M.; El-Naggar, Moustafa Y.
Abstract
Heavy metal pollution is one of the most serious environmental and human health risk problem associated with industrial progress. The present study was conducted with the goal of isolation and characterization of metal-resistant lactic acid bacteria (LAB) from the Alexandrian Mediterranean Seacoast, Egypt, with their possible exploitation in metal remediation. Lactobacillus plantarum MF042018 exhibited high degree of resistance, up to 500 and 100 ppm, to both nickel and chromium, respectively, with multiple antibiotic resistance (MAR) index above 0.5. In an attempt to improve chromium removal by L. plantarum MF042018, Plackett-Burman followed by Box-Behnken statistical designs were applied. An initial Cr2+ concentration of 100 ppm and inoculum size of 3% presented the best conditions for the accumulation of chromium by L. plantarum MF042018. The study was also navigated to assess the biosorption capacity of L. plantarum MF042018, the maximum uptake capacity (q) of both Cd2+ and Pb2+ was recorded at pH 2.0 and a temperature of 22 degrees C after 1 hr. The biosorption process of Cd2+ and Pb2+ was well explained by the Langmuir isotherm model better than the Freundlich isotherm. Furthermore, the results revealed that the use of L. plantarum MF042018 is an effective tool for the treatment of hazardous metal-polluted battery-manufacturing effluent. Therefore, the present study implies that L. plantarum MF042018 can be applied as a promising biosorbent for the removal of heavy metals from industrial wasterwaters.