Feasibility study on high-temperature sorption of hydrogen sulfide by natural soils

In this study, seven natural soils were tested for the sorption of hydrogen sulfide from coal gasification gas at high temperature. Results indicate that the LP natural soil has the best performance and the highest sulfur sorption capacity. After extracting free iron oxides, most natural soils have no sorption efficiency. The free iron oxides, therefore, proved to be the major components that react with hydrogen sulfide to form iron sulfides. The sulfur sorption capacity, either determined by EA or breakthrough time, is very close to the theoretical value based on the stoichiometric calculation with the content of free iron oxides. Moreover, the presence of CO is a positive effect while H2 is a negative effect. This can be explained via the water-shift reaction. On the basis of the results of temperature-programmed sulfidation (TPS), the starting temperature for the sorption of hydrogen sulfide is between 623-673 K. From the analyses of temperature-programmed oxidation (TPO) and XPS, the iron polysulfides are the major products and approximately 90% regeneration efficiency can be theoretically achieved while the temperature is controlled higher than 813 K. In the regeneration tests, the results show that the LP natural soil can be regenerated and thus reused after the oxidation process. No significant degeneration occurs on the LP natural soil after five sorption/regeneration cycles. The sulfur sorption capacity of the tenth regenerated soil can be achieved at least 80% compared to the fresh one. The experimental analyzed SO2 concentration from the regeneration process is almost identical to the theoretical calculated equilibrium concentration of the process. Maghemite is the main product after the regeneration process.     

Reduced biodegradation of benzonitrile in soil containing wheat-residue-derived ash

Burning of crop residues is a common agricultural practice that incorporates the resulting particulate matter (ash) of high adsorptivity into soils. To investigate the effect of ash on the biodegradation of pesticides in soils, we measured the sorption, desorption, and biodegradation of benzonitrile in a silt loam in the presence and absence of an ash resulting from burning of wheat (Triticum aestivum L.) residue. Biodegradation experiments were conducted by inoculating sorbent slurries with a pure culture of benzonitrile-degrading bacteria (Nocardia sp.). Both liquid- and sorbed-phase benzonitrile concentrations were quantified over time. The ash was approximately 2000 times more effective per unit mass than the soil in sorbing benzonitrile. Amendment of the soil with 1% ash (by weight) resulted in a 10-fold increase in sorption. Sorption of benzonitrile by the ash significantly decreased the solution-phase concentration in the slurries of ash and ash-amended soil. Desorption of benzonitrile from the ash required approximately 60 min to complete, whereas approximately 20 min were required for desorption from the soil. Benzonitrile in the extracts of various sorbents and soil slurry was completely degraded within 500 min. However, the degradation was substantially reduced in the presence of the ash. At 2000 min, only 20% of benzonitrile in ash slurry and only 44% in ash-amended soil slurry were degraded. An acclimation period of approximately 100 min was observed in extracts and slurries containing the ash. Substantial reduction in the biodegradation of benzonitrile in the presence of wheat ash was apparently due to sorption of benzonitrile by the ash, slow desorption from the ash, and the increased acclimation period. Our results suggest that the presence of crop-residue-derived ash may increase the persistence of pesticides in agricultural soils.     

活性炭生物转盘法处理化工废水

使用固定剂将颗粒状活性炭固定在盘片上，制成了一种新型生物转盘盘片——活性炭生物转盘盘片。采用一级微型生物转盘法处理模拟化工废水，对比了活性炭、石英砂、聚丙烯3种生物转盘的处理效果。实验结果表明，活性炭生物转盘对COD的去除效果好于其他两种转盘。在进水COD为600mg／L、水力停留时间为6h、盘片转速为4r／min的条件下，活性炭生物转盘对COD的去除率可达71．3％。此外，活性炭生物转盘还有较强的耐有机负荷冲击能力。在废水处理过程中，活性炭仅在挂膜的前7天起吸附作用，挂膜成功后生物降解起主导作用。     

Effects of inorganic nutrients on the regrowth of heterotrophic bacteria in drinking water distribution systems

Three laboratory-scale water pipe systems were set up to study the effects of adding three inorganic nutrients (ammonium, nitrate or phosphate) on biofilm formation in water pipes. The results showed that the effects of adding ammonium or nitrate on the biofilm formation were insignificant when levels below 0.1 mg N/l were added. Analogous results were observed when phosphate was added at levels below 0.005 mgP/l. However, as the addition of ammonium increased to 0.5 mgN/l, significant effects on biofilm formation were observed. Similar results were obtained phosphate was added at levels above 0.01 mgP/l. Batch tests were also conducted using water samples collected from a Taiwanese drinking water distribution system. The results indicated that the addition of ammonium, nitrate or phosphate to treatment plant effluent stimulates bacterial growth. In the distributed water of an urban area, the addition of nitrate or phosphate stimulated bacterial growth. The bacterial growth in the distributed water of a suburban area was not stimulated by adding any of these three inorganic nutrients.     

Comparison of Solid-Phase and Pore-Water Approaches for Assessing the Quality of Marine and Estuarine Sediments

As part of our continuing evaluation of the pore-water approach for assessing sediment quality, we made a series of side-by-side comparisons between the standard 10-day amphipod whole sediment test with the corophiid Grandidierella japonica and a suite of tests using pore water extracted from the same sediments. the pore-water tests evaluated were the sea urchin (Arbacia punctulata) sperm cell test and morphological development assay, the life-cycle test with the polychaete Dinophilus gyrociliatus, and acute exposures of red drum (Sciaenops ocellatus) embryo-larval stages. Sediment and surface microlayer samples were collected from contaminated sites. Whole-sediment, pore-water, and surface microlayer toxicity tests were performed. Pore-water toxicity tests were considerably more sensitive than the whole-sediment amphipod test, which is currently the most sensitive toxicity test now recommended for determining the acceptability of dredged material for open ocean disposal.     

Toxicological assessment of chlorinated diphenyl ethers in the rat, Part II

Chlorinated diphenyl ethers (CDE's) are environmental contaminants that have been found in Great Lakes fish. Because of the paucity of toxicity data and potential for human exposure, the present short-term study was conducted to assess their potential toxic effects. Groups of 10 male and 10 female rats were administered the three CDE congeners (2,2',4,4',5-pentachlorodiphenyl ether (PCDE), 2,2',4,4',5,5'-hexachlorodiphenyl ether (HCDE), 2,2',3,4,4',6,6'-heptachlorodiphenyl ether (HPCDE] in diets at levels of 0.5, 5.0, 50 or 500 ppm for a period of 4 weeks. Decreased food consumption was observed with male and female rats fed the diet containing 500 ppm HPCDE. Treatment with the three isomers at the highest dose level produced an increase in liver weight in both sexes. While administration of PCDE produced an increase in hepatic aminopyrine demethylase activity, HCDE caused a significant increase in aminopyrine demethylase, aniline hydroxylase and ethoxyresorufin de-ethylase activities. HPCDE caused a significant increase in ethoxyresorufin de-ethylase activity. HPCDE at the highest dose level also caused a significant reduction in circulating lymphocytes in male rats. The 3 CDE's produced mild and adaptative histological changes in the liver and thyroid, but only HPCDE elicited mild changes in the thymus, bone marrow, and spleen. The above data indicate that HPCDE is immunosuppressive and that all three CDE isomers are considered to be moderately toxic in rats. The no-observable effects levels appear to be between 5-50 ppm in diet (0.36-3.0 mg/kg b.w.) for the three CDE's.     

Petroleum biodegradation in soil: The effect of direct application of surfactants

The direct application of surfactants to petroleum-contaminated soil has been proposed as a mechanism to increase the bioavailability of insoluble compounds. Solubilization of hydrophobic compounds into the aqueous phase appears to be a significant rate limiting factor in petroleum biodegradation in soil. Nonionic surfactants have been developed to solubilize a variety of compounds, thus increasing the desorption of contaminants from the soil. In this study, laboratory scale land treatment scenarios were used to monitor the bioremediation of petroleum contaminated soils. In efforts to achieve the lowest levels of residual petroleum hydrocarbons in the soil following biotreatment, 0.5 and 1.0% (volume/weight) surfactant was blended into soils under treatment. Two soil types were studied, a high clay content soil and a sandy, silty soil. In both cases, the addition of surfactant (Adsee 799®, a blend of ethoxylated fatty acids, Witco Corporation) stimulated biological activity as indicated by increased heterotropbic colony forming units per gram of soil. However, the increased activity was not correlated with removal of petroleum hydrocarbons. The results suggest that the application of surfactants directly to the soil for the purpose of solubilizing hydropbobic compounds was not successful in achieving greater levels of petroleum hydrocarbon removal.     

Watershed surveys to support an assessment of the regional effects of acidic deposition on surface water chemistry

Through the Direct/Delayed Response Project (DDRP), the United States Environmental Protection Agency is attempting to assess the risk to surface waters from acidic deposition in three regions of the eastern United States: the Northeast Region, the Southern Blue Ridge Province, and the Mid-Appalachian Region. The central policy question being addressed by the DDRP is: Within the regions of concern, how many surface water systems (lakes, streams) will become acidic due to current or altered levels of acidic sulfur deposition, and on what time scales? The approach taken by the DDRP is to select a statistically representative set of watersheds in each region of concern and to project the future response of each watershed to various assumed levels of acidic deposition. The probability structure will then be used to extrapolate the watershed-specific results to each region. The data will be used also for statistical investigation of hypothesized relationships between current surface water chemistry and watershed characteristics. Because the needed terrestrial data base was not available, regional watershed surveys were conducted to meet the specific data needs of the DDRP. Maps (1∶24,000) of soils, vegetation, land use, depth to bedrock, and bedrock geology were made for each watershed. The soils were grouped into sampling classes based on their hypothesized response to acidic deposition. Randomized sampling of these classes provided regional means and variances of soil properties that can be applied to individual watersheds. Because of DDRP's need for consistency within and among regions, unique quality control/quality assurance activities were developed and implemented. After verification and validation, the DDRP data base will be made publicly available. This will be a unique and useful resource for others investigating watershed relationships on a regional scale. The results of these surveys and the conclusions of the DDRP will be presented in several future papers. The current paper gives an overview of the context, rationale, logistical considerations, and implementation of these surveys, with special emphasis on the field activities of watershed mapping and soil sampling. This discussion should be useful to those planning, implementing, and managing survey activities in support of regional assessments of other environmental concerns, who are likely to face similar choices and constraints.