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Tetrachloroethene is a prominent groundwater pollutant that can be reductively dechlorinated by mixed anaerobic microbial populations to the nontoxic product ethene. Strain 195, a coccoid bacterium that dechlorinates tetrachloroethene to ethene, was isolated and characterized. Growth of strain 195 with H2 and tetrachloroethene as the electron donor and acceptor pair required extracts from mixed microbial cultures. Growth of strain 195 was resistant to ampicillin and vancomycin; its cell wall did not react with a peptidoglycan-specific lectin and its ultrastructure resembled S-layers of Archaea. Analysis of the 16S ribosomal DNA sequence of strain 195 indicated that it is a eubacterium without close affiliation to any known groups

The United Nations Framework Convention on Climate Change aims to stabilize the greenhouse gases that pose a threat to the world's climate. The Kyoto Protocol, which aims to reduce fossil fuel emissions and the net emissions from some terrestrial ecosystems in developed countries, is examined.

There has been much interest recently in the use of constructed wetlands for the removal of toxic trace elements from wastewaters. Wetland plants play an important role in the trace elements removal process. It is not known, however, which wetland plant species absorb specific trace elements at the fastest rates. Such knowledge is essential to maximize the efficiency of trace element removal by wetlands. In this study, we investigated the potential of duckweed (Lemna minor L.) to accumulate Cd, Cr, Cu, Ni, Pb, and Se when supplied individually in a nutrient solution at a series of concentrations ranged from 0.1 to 10 mg L-1. The results show that under experimental conditions, duckweed proved to be a good accumulator of Cd, Se, and Cu, a moderate accumulator of Cr, and a poor accumulator of Ni and Pb. The highest concentrations of each trace element accumulated in duckweed tissues were 13.3 g Cd kg-1, 4.27 g Se kg-1, 3.36 g Cu kg-1, 2.87 g Cr kg-1, 1.79 g Ni kg-1, and 0.63 g Pb kg-1. Duckweed exhibited some symptoms of toxicity (e.g., reduced growth, chlorosis) at higher levels of element supply (except for Cr). The toxicity effect of each trace element on plant growth was, in descending order of damage, Cu Se Pb Cd Ni Cr. We conclude that duckweed shows promise for the removal of Cd, Se, and Cu from contaminated wastewater since it accumulates high concentrations of these elements. Further, the growth rates and harvest potential make duckweed a good species for phytoremediation activities

Animal production results in conversion of feeds into valuable products such as meat, milk, eggs, and wool as well as into unavoidable and less desirable waste products. Intensification of animal numbers and increasing urbanization has resulted in considerable attention to odorous gases produced from animal wastes. It is clear that animal manure was, and still is, a valuable resource. However, it may be a major obstacle to future development of the animal industry if its impact on the environment is not properly controlled. Poor odor prevention and control from animal wastes is related to a lack of knowledge of the fundamental nature of odor and its production by farm animals. Odor, like noise, is a nuisance or disturbance and there is no universally accepted definition of an objectionable odor. Thus, regulation and control of odors in the environment is difficult because of the technical difficulties of defining odor limits and their measurement and evaluation. A variety of direct (sensory) and indirect (analytical instruments) methods for measuring odor intensity and determination of individual or key odor components are discussed. The biological origins of the four principal classes of odor compounds, namely branched- and straight-chain VFA, ammonia and volatile amines, indoles and phenols, and the volatile sulfur-containing compounds, are reviewed. Because more than 50% of N from animals is excreted as urea, one strategy to conserve N in waste is to inhibit the urease enzyme that converts urea to ammonia. Laboratory studies to evaluate di- and triamide compounds to control urea hydrolysis in slurries of cattle and swine wastes are presented. Finally, a brief overview of various intervention strategies is provided. Multiple combinations of nutritional management, housing systems, treatment options as well as storage and disposal of animal wastes will be required to reduce environmental pollution and provide for long-term sustainable growth

The use of granular iron for in situ degradation of dissolved chlorinated organic compounds is rapidly gaining acceptance as a cost-effective technology for ground water remediation. This paper describes the first field demonstration of the technology, and is of particular importance since it provides the longest available record of performance (five years). A mixture of 22% granular iron and 78% sand was installed as a permeable \"wall\" across the path of a contaminant plume at Canadian Forces Base, Borden, Ontario. The major contaminants were trichloroethene (TCE, 268 mg/L) and tetrachloroethene (PCE, 58 mg/L). Approximately 90% of the TCE and 86% of the PCE were removed by reductive dechlorination within the wall, with no measurable decrease in performance over the five year duration of the test. Though about 1% of the influent TCE and PCE appeared as dichloroethene isomers as a consequence of the dechlorination of TCE and PCE, these also degraded within the iron-sand mixture. Performance of the field installation was reasonably consistent with the results of laboratory column studies conducted to simulate the field behavior. However, if a more reactive iron material, or a higher percentage of iron had been used, complete removal of the chlorinated compounds might have been achieved. Changes in water chemistry indicated that calcium carbonate was precipitating within the reactive material; however, the trace amount of precipitate detected in core samples collected four years after installation of the wall suggest that the observed performance should persist for at least another five years. The study provides strong evidence that in situ use of granular iron could provide a long-term, low-maintenance cost solution for many ground water contamination problems

River sediment can be used to measure the pollution level in natural water, as it serves as one of the vital environmental indicators. This study aims to assess heavy metal pollution namely Copper (Cu), Iron (Fe), Manganese (Mn), Zinc (Zn), Nickel (Ni), Lead (Pb), and Cadmium (Cd) in Surma River. Further, it compares potential ecological risk index values using Hakanson Risk Index (RI) and Monte Carlo Simulation (MCS) approach to evaluate the environmental risks caused by these heavy metals. in the study area. With obtained results, enrichment of individual heavy metals in the study area was found in the order of Ni > Pb > Cd > Mn > Cu > Zn. Also, variance in MCS index contributed by studied metals was in the order of Cd > Pb > Ni > Zn > Cu. None of the heavy metals, except Ni, showed moderate contamination of the sediment. Risk index values from RI and MCS provide valuable insights in the contamination profile of the river, indicating the studied river is currently under low ecological risk for the studied heavy metals. This study can be utilized to assess the susceptibility of the river sediment to heavy metal pollution near an urban core, and to have a better understanding of the contamination profile of a river.

Development pressures in rural mountainous areas of the United States hold crucial implications for water quality. Especially important are changes in the extent and pattern of various land uses. We examine how position along an urban-rural gradient affects landscape patterns in a southern Appalachian watershed, first by testing for the effect of distance from an urban center on land-cover change probabilities and then simulating the implied development of a landscape at regular distance intervals. By simulating a common hypothetical landscape we control for variable landscape conditions and define how land development might proceed in the future. Results indicate that position along the urban-rural gradient has a significant effect on land-cover changes on private lands but not on public lands. Furthermore, position along the gradient has a compounding effect on land-cover changes through interactions with other variables such as slope. Simulation results indicate that these differences in land-cover changes would give rise to unique \"landscape signatures\" along the urban-rural gradient. By examining a development sequence, we identify patterns of change that may be most significant for water quality. Two locations along the urban-rural gradient may hold disproportionate influence over water quality in the future: (1) at the most remote portion of the landscape and (2) at the outer envelope of urban expansion. These findings demonstrate how landscape simulation approaches can be used to identify where and how land use decisions may have critical influence over environmental quality, thereby focusing both future research and monitoring efforts and watershed protection measures.

Most P losses from surface-irrigated fields occur via runoff, are associated with eroded sediment, and can be minimized by eliminating irrigation-induced erosion. A convenient new practice that eliminates furrow irrigation-induced soil losses uses a high molecular weight, furrow irrigation-induced soil losses uses a high molecular weight, anionic polyacrylamide (PAM) applied to initial irrigation inflows. We hypothesized that, compared to control furrows, PAM treatment would reduce field losses of ortho P, total P, NO3, and lower tailwater chemical oxygen demand (COD). Two PAM treatments were tested: I10 applied 10 mg L-1 PAM only during the furrow advance (i.e., the application was halted after runoff began) and C1 applied 1 mg L-1 PAM continuously throughout the irrigation. Soil was Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthid) with 1.6% slope. Initial inflows were cut back from 23 to 15 L min-1 after 1.5 to 6 h. Total soil loss over four irrigations was 3.06 Mg ha-1 for control furrows vs. 0.33 (C1) and 0.24 (I10) for PAM-treated furrows. Ortho-P and total P concentrations in control tailwaters were five to seven times that of PAM treatments, and COD levels were four times those of PAM treatments. Runoff in controls was two times that of PAM-treated furrows. PAM-I10 lowered furrow stream nutrient concentrations more than did PAM-C1, but owing to disparities in runoff, the two treatments produced similar cumulative sediment and nutrient mass losses. The PAM is effective, convenient, and economical, and greatly reduces P and organic material (COD) losses from surface-irrigated fields

Nitrate (NO3) contamination of groundwater can cause pollution of receiving waters. We examined the mechanisms by which a \"denitrification wall\" removed NO3 from shallow groundwater. The denitrification wall was constructed by digging a trench (35 m long, 1.5 m deep, and 1.5 m wide) that intercepted groundwater. The excavated soil was mixed with sawdust (30% v/v) as a C source then returned to the trench. We assessed NO3 removal and denitrification in the wall for 1 yr. Incoming concentrations of NO3 in groundwater ranged from 5 to 16 mg of N L-1 but these decreased to 2 mg N L-1 in the denitrification wall. Total N in the wall declined during the year demonstrating that N immobilization was not a large sink for NO3. Denitrifying enzyme activity (DEA) reached a maximum of 906 ng of N g-1 h-1 after 6 mo of operation, indicating that denitrification was an important mechanism for NO3 removal. We calculated a maximum rate of NO3 removal by denitrification of 3.6 g N m-3 d-1. Substrate-amendment experiments showed that denitrification in the wall was primarily limited by NO3 concentration and not C. During the study there was no significant decrease (P 0.05) in total C but the availability of the remaining C declined. Despite this decrease, the DEA and microbial biomass were stable during the last 6 mo. This study demonstrated that denitrification walls can effectively remove NO3 from groundwater thereby protecting receiving waters

Heavy metal contamination can impact soil ecosystems sufficiently to result in significant losses in soil quality. The negative impact of heavy metals results from their toxicity to biological processes, including processes catalyzed by soil microorganisms. Therefore, it is postulated that the soil microbial community could serve as an indicator of losses in soil quality due to heavy metal contamination and of changes in soil quality resulting from reclamation. In this study, the size, activity, and structure of microbial communities from remediated and unremediated soils in the vicinity of a Zn smelter were evaluated. Both total and soluble metal loadings in these soils increased with proximity to the smelter. Indicators of microbial activity (dehydrogenase activity) and viable population size (plate counts) were negatively affected by the elevated metal levels. Microbial community structure also varied with increasing contamination, as indicated by cluster analysis and principal component analysis of BIOLOG community metabolic profiles. Remediated soils at this site were treated by surface application of a mixture of sewage sludge and fly ash. Remediation resulted in a decrease in soluble metals and an increase in indicators of biological activity and viable population size. Remediated soils also showed metabolic profiles that were more similar to the least contaminated site, suggesting recovery of the microbial populations. These data suggest that the microbial community may be a useful indicator of changes in soil quality with management of these highly contaminated soils