Vapor Extraction/Bioventing Sequential Treatment of Soil Contaminated with Volatile and SemiVolatile Hydrocarbon Mixtures

A cost-effective removal strategy was studied in bench-scale columns that involved vapor extraction (SVE) and bioventing (SBV) sequential treatment of toluene- and decane-contaminated soil. By using GC analysis to measure hydrocarbon concentrations, CO₂, and O₂ content values in the outlet gas, the removal kinetics were determined as was the contribution of evaporation and biodegradation to the removal of contaminants from soil. The effect of operating mode on treatment performance was studied at a continuous air flow and consecutively at two different flow rates, and compared with an intermittent (pulse) flow rate. The two-rate flow was required due to the inhibitory effect of toluene on indigenous microorganisms at above 75% of the toluene saturation concentrations in the gas phase. The intermittent flow was controlled by the O₂ content values in the soil gas, which at above 4% did not limit biodegradation. To reach comparable removal efficiency at the constant flow, about three times less air was required for toluene than for decane. This air volume could be reduced, in the case of decane, by a factor of 1.6 and 2.9, at the two-rate and intermittent flow, respectively. A higher contribution of biodegradation to the overall removal of hydrocarbon will lower hydrocarbon concentrations in the off-gases to be treated. Together with the decreased amount of air used, this can reduce the overall remediation costs. The overall process can be better understood by determining the degree of contaminants removal by evaporation and biodegradation in the experimental set up.     

Outgassing Losses of Toluene and m-Xylene Evaluated by 14C-Based Mass Balances for Laboratory Bioventing Simulations

Mixtures of toluene, ethylbenzene, and the xylenes spiked with ¹⁴C-labeled toluene or m-xylene were added to bench-scale bioventing simulation columns filled with hydrocarbon-contaminated subsurface soils. After 2 to 4 weeks of incubation during which air was pumped through the column at rates of at least 2?ml·min^?1·kg^?1 between 54 and 84% of the radiolabel was recovered in traps as outgassed parent compound from four columns sterilized with gamma-irradiation. In contrast, seven nonsterilized but otherwise identically treated (except for inorganic nitrogen addition) columns lost less than 0.4% (and one column lost 0.7%) of the radiolabel through outgassing of the parent compound. Nonsterilized columns lost 40 to 61% of the radiolabel as ¹⁴CO₂, whereas gamma-irradiated columns usually lost only trace amounts of ¹⁴C in this form. Biologically active columns also retained much larger fractions than sterilized columns of the radiolabel in the subsoil in forms, possibly microbial biomass, from which it could be recovered by wet oxidation. Addition of 10 or 40?mg/kg of mineral nitrogen had no consistent effect on bioventing performance.     

Evaluation of Soil Vapor Extraction and Bioventing for a Petroleum-Contaminated Shallow Aquifer in Korea

The feasibility of soil vapor extraction and bioventing technologies was examined for a petroleum hydrocarbon-contaminated site. The test site was highly contaminated with toluene, ethylbenzene, and xylene, due to leakage from petroleum storage tanks. Three respiration tests demonstrated that the test site conditions were appropriate for application of air-based remediation technologies. The oxygen consumption rates ranged from 4.32 to 7.68 %-O₂/day and biodegradation rates ranged from 2.72 to 4.84?mg/kg-day in respiration tests. In a 120-day soil vapor extraction pilot test, high initial mass removals (with tailing effects) were observed. As expected for the soil vapor extraction, the volatilization rate was much higher than the biodegradation rate. In a bioventing trial, the biodegradation effect was predominant, but a tailing effect was not observed. From this study, the suggested sequence of remediation is to construct an integrated system of soil vapor extraction and bioventing and initially operate the soil vapor extraction system until the volatilization rate becomes smaller than the biodegradation rate. After that, the system needs to be changed over to a bioventing mode. Field demonstration supports the feasibility of the proposed integrated system.     

The Oxidative and Morphological Effects of High Concentration Chronic Toluene Exposure on Rat Sciatic Nerves

This study was designed to investigate the effects of chronic toluene inhalation in high concentration on lipid peroxidation, antioxidant enzyme activities and ultrastructural changes in the sciatic nerves of rats. Male Wistar albino rats (150–250 g) were divided in two experimental groups: the control and the toluene treated group (n=10 for each). Toluene treatment was performed by inhalation of 3000 ppm toluene, in a 8 h/day and 6 day/week order for 16 weeks. Blood and tissue samples were obtained for biochemical and histopathological investigation. The blood and sciatic nerves were assayed for toluene by gas chromatography. Toluene significantly increased blood and tissue malondialdehyde (MDA), and decreased tissue superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), but not tissue catalase (CAT) levels when compared with controls. Electron micrographs of sciatic nerve in the toluene group shows myelin destructions with onion-bulb and bubble form protrusion on the myelin sheath and axolemma border of myelinated axons. The area of injury on the myelin sheath were measured by Image-Pro Plus. Mean of the injury area were estimated 34% each myelin. These findings indicate that chronic toluene inhalation might be involved with free radical processes.     

Bioremediation of Soil Contaminated with Explosives at the Naval Weapons Station Yorktown

The explosives TNT, HMX, and RDX are integral components of many munitions. The wastes from the manufacture and the use of these and other explosives has resulted in substantial contamination of water and soil. White rot fungi have been proposed for use in the bioremediation of contaminated soil and water. Strains of Phanerochaete chrysosporium and Pleurotus ostreatus adapted to grow on high concentrations of TNT were studied with regard to their ability to degrade TNT in liquid cultures. Both strains were able to cause extensive degradation of TNT. Field bioremediation studies using P. ostreatus were performed on site at the Yorktown Naval Weapons Station Yorktown (Yorktown, VA). In two plots, 6 cubic yards of soil contaminated with TNT, HMX, and RDX were blended with 3 cubic yards of a substrate mixture containing nutrients that promote the growth of fungi. In soil amended with growth substrate and P. ostreatus, concentrations of TNT, HMX and RDX were reduced from 194.0±50, 61±20 mg/kg and 118.0±30 to 3±4, 18±7 and 5±3?mg/kg, respectively, during a 62-day incubation period. Interestingly, in soil that was amended with this substrate mixture, but not with P. ostreatus, the concentrations of TNT, HMX, and RDX were also reduced substantially from 283±100, 67±20, and 144±50?mg/kg to 10±10, 34±20, and 12±10?mg/kg, respectively, during the same period. Thus, it appears that addition of amendments that enhance the growth and activity of indigenous microorganisms was sufficient to promote extensive degradation of these compounds in soil.     

Correlations between PID and FID Field Analytical Instruments in the Analysis of Soil Contaminated with Diesel Fuel

Research was conducted to determine if there is a correlation between the data gathered by field analytical instruments in analyzing soil contaminated with diesel fuel. One instrument was equipped with a flame ionization detector (FID) and the other a photoionization detector (PID). The results showed that the concentration readings of the PID and FID displayed a linear relationship for soil recently contaminated with diesel fuel. However, for soil containing weathered diesel fuel in the field, a logarithmic relationship between the PID and FID readings was displayed. It was also determined by laboratory experimentation that the PID and FID readings both exhibited log-linear decreases over time for uncovered diesel fuel-contaminated soil. It was concluded that the PID and FID can both individually be used to evaluate soil contaminated by diesel fuel and might be interchangeable depending on the needs of the researcher.     

Effect of Toluene and Nutritional Status on Serotonin,Lipid Peroxidation Levels and NA<Superscript>+</Superscript>/K<Superscript>+</Superscript>-ATPase in Adult Rat Brain

The aim was to evaluate the effect of toluene and nutritional status on levels of serotonin (5-HT), 5-hydroxytryptophan (5-HTP), Na⁺/K⁺-ATPase, total ATPase and lipid peroxidation (TBARS) in rat brain. Study was conducted with malnourished (MN), well-nourished (WN) and normal Wistar rats. Three groups were formed for each nutritional status: control group I received 0.9% NaCl; toluene (1 g/kg) was administered to group II, and 1.5 g/kg to group III. Levels of 5-HT decreased (P < 0.05) in WN toluene groups, and 5-HTP decreased (P < 0.05) in the WN 1 g toluene and MN 1.5 g toluene groups. TBARS decreased (P < 0.05) in WN toluene groups. A trend to increase in Na⁺/K⁺-ATPase was found in WN and MN toluene groups, while total ATPase increased (P < 0.05) in the WN 1.5 g toluene group. The results suggest that high concentrations of toluene in single doses induce significant changes in the serotonergic system and alter membrane fluidity more perceptibly in the brain of adult animals with regular diet than in malnourished animals.     

The Effect of Temperature and Aeration Rate on Bioremediation of Diesel-contaminated Soil in Solid-phase Bench-scale Bioreactors

Bioremediation of hydrocarbon (HC) contaminated soils is most effective in aerobic conditions. Despite the fact that mass transfer of oxygen is an important process parameter, the effect of this parameter on solid-phase bioremediation has received limited attention. In this study, the combined effect of temperature and aeration on the bioremediation of low organic content coarse-grained soils, freshly contaminated with diesel, was investigated in solid-phase bench-scale bioreactors. Total HC and carbon range soil concentrations, volatilization, and microbial activity were monitored throughout the six-month experiments at two temperatures (7 and 22°C) and at two aeration rates (13 and 45 mL·s^?1). Total HC removal reached between 48 and 83%. Generally, removal increased proportionally with temperature and aeration rates, and decreased proportionally with HC compounds molecular weight. Both biodegradation and volatilization played important roles in removal in all treatments. The high aeration rate enhanced microbial activity in soil. Enhancement was believed to be due to increased mass transfer of oxygen from the soil gas to the soil solution, where microbial activity occurs. However, high aeration also enhanced volatilization, especially at 22°C where 51% of HCs were lost to volatilization. High aeration rate enhanced biodegradation of compounds > nC15 without promoting their excessive volatilization.     

The Effect of Phyllode Temperature on Gas Exchange and Chlorophyll Fluorescence of Acacia mangium

The optimum temperature for photosynthetic CO₂ assimilation of A. mangium phyllodes was 30–32 °C. Photosystem 2 (PS 2) exhibited high tolerance to high temperature. Gas exchange and the function of PS2 of A. mangium were adapted to the temperature regime of the tropical environment and this might be the contributing factor to their fast growth under tropical conditions.     

Effect of Moisture and Temperature on the Survival of Sclerotia of Sclerotium rolfsii in Soil

The sclerotia of Sclerotium rolfsii Sacc. survived in natural soil for 225 days under controlled moisture at 50% water holding capacity (WHC) after which there was a progressive reduction in the population of viable sclerotia. At 390 days only 48% were recovered. Sclerotia survived well at moisture contents upto 75% WHC but at 100% the population declined rapidly and none were recovered after 60 days. The contents of the sclerotia were found to lyse without germination leaving hollow rinds. Such lysis was found to be favoured between 25 and 40°C. At and below 20°C no such lysis was recovered and more than 80% sclerotia were recovered even after 60 days.     

温度对八斑鞘腹蛛实验种群生长的影响

八斑鞘腹蛛(Coleosoma octomaculatum)是农田害虫的主要天敌之一。它分布范围广、数量大,可捕食棉蚜(Aphis gossypii)、豆蚜(A.craccivora)、柳蚜(A.saliceti)、菜缢管蚜(Lipaphis erysimi)、麦长管蚜(Macrosi-     

Effect of Soil Moisture on the Gas Exchange of Changium smyrnioides and Anthriscus sylvestris

The effect of soil moisture on gas exchange and growth of an endangered species, Changium smyrnioides, was compared with a non-endangered species, Anthriscus sylvestris. The two species belong to the same family Umbellaceae. With the decrease of soil moisture, the net photosynthetic rate (P_N) and transpiration rate (E) decreased, while water use efficiency (WUE) increased, P_N and WUE of C. smyrnioides were lower than those of A. sylvestris, whereas E was higher than that of A. sylvestris. The biomass, leaf mass ratio (LMR) and leaf area ratio (LAR) of C. smyrnioides were lower than those of A. sylvestris. Under drought, biomass. LMR and LAR of C. smyrnioides decreased more steeply than those of A. sylvestris, whereas specific root length (SRL) of C. smyrnioides was higher, compared to that of A. sylvestris. The present study indicated that C. smyrnioides accumulated less biomass, and directed more biomass to roots than A. sylvestris.     

Influence of Short-Chain Aliphatic Acids on the Phenanthrene Desorption and Mobilization from Contaminated Soil

This study was performed to investigate the influence of short-chain aliphatic acids (SCAAs) on the desorption of phenanthrene from artificially contaminated soils with this polycyclic aromatic hydrocarbon. Five SCAAs examined, including acetic acid, oxalic acid, malic acid, tartaric acid and citric acid, were related to the increase of phenanthrene desorption from two kinds of soil. Citric acid and oxalic acid enhanced phenanthrene desorption to a more significant extent than other organic acids. The effects of pH, SCAA concentration, and ionic strength were further evaluated. The phenanthrene desorption was enhanced as the pH increased. An increase in desorbed phenanthrene from pH 3 to pH 8 was observed, but that was followed by a slight decrease above pH 8 for most SCAAs. The phenanthrene desorption performance showed increments with increasing organic acid concentrations. However, the increase of phenanthrene desorption became less remarkable when SCAA concentrations were above 100 mmol/L. Moreover the results suggested that high ionic strength hindered the desorption of phenanthrene in the presence of SCAAs.     

Effect of Dietary Linoleate/alpha-Linolenate Balance on the Brain Lipid Composition,Reproductive Outcome and Behavior of Rats during Their Prenatal and Postnatal Development

The effect of the dietary linoleate (LA)/alpha-linolenate (LNA) balance during development on the brain lipid composition, reproductive outcome and behavior of rats was studied. Female rats were fed on experimental diets during pregnancy and the resulting pups for 16 weeks. The dietary LA/LNA ratios were 1.07 (LA1), 2.64 (LA2), 4.45 (LA3), 7.68 (LA4) and 10.35 (LA5). The relative content of docosahexaenoate (DHA) in the brain of pups tended to increase with decreasing LA/LNA ratio at 0 and 3 weeks, while the level of DHA was maintained constant at 16 weeks regardless of the dietary LA/LNA ratio. The learning ability was measured at 12 weeks of age, and there was no difference among the groups. In an open field test, the exploratory index was significantly lower in the LA1 group than in the LA2 group. The LA1 group had a smaller litter size and lower survival rate than the other groups. We conclude that if the diet contained appropriate amounts and balance of LA and LNA, it was possible for rats to synthesize an appropriate amount of DHA and have normal behavioral activity without DHA supplementation.     

Influence of Temperature and Oil Content on the Soil/Air Partition Coefficient for Hexachlorobenzene in Oil-Contaminated Rice Paddy Field Soil

The soil/air partition coefficients (K _SA ) for hexachlorobenzene (HCB) in oil-contaminated (crude oil and diesel) rice paddy field soils were measured in a solid fugacity meter at different oil concentrations over the temperature range of 5 to 30°C at 100% relative humidity. The results showed that values of K _SA increased with a decrease of temperature. As for oil content, there is a critical separate phase concentration (CSPC) above which K _SA increased with increasing of oil content. When oil content is above CSPC, oil plays a role as a separate phase that enhances the sorption capacity of the soil. At a given temperature (20°C) values of CSPC depended on the natural organic matter (NOM) contents of the soil, while for a given oil concentration they depended on the temperature. The normalized oil/air partition coefficients ) for HCB deduced from K _SA for oils and experimentally determined with crude oil/quartz sand system were similar and 0.7–7 times higher than the normalized organic/air partition coefficient ), which implied that oil was a super sorbent. The enthalpies (ΔH_SA) for crude oil and diesel were 64.9 and 55.7 kJ mol^?1, respectively.     

The Influence of Liquid to Soil Ratios on Arsenic and Lead Bioaccessibility in Reference and Field Soil

In vitro bioaccessibility testing is gaining popularity as a tool to estimate the oral bioavailability of contaminants in soil for human health risk assessment (HHRA). Bioaccessibility tests are used to measure the bioaccessible fraction of a contaminant in soil, which can then be used to estimate the bioavailable fraction. Inherent uncertainties are associated with bioaccessibility tests. Various test parameters need to be carefully considered in their development, including the liquid to soil (L/S) ratio employed. We used L/S ratios (v:wt) ranging from 25 ml:1 g to 1,000 ml:1 g in a modified relative bioaccessibility extraction procedure to investigate the effects on bioaccessibility of lead and arsenic in field and reference soils. General trends of increased percent bioaccessibility of lead and arsenic with increasing L/S ratio were observed in the reference soil. A similar positive relationship was observed for lead in the field soil; soluble arsenic concentrations were below the detection limit and data were insufficient to observe a trend. Percent bioaccessibility was significantly affected at each extreme of the L/S ratios tested (p < .05). Biological relevance, technical feasibility, and mathematical relationships with in vivo results should be considered when selecting an appropriate L/S ratio for bioaccessibility testing.     

氮磷钾配比与用量对湘杂油763产量和经济效益的影响

为了筛选出冬油菜新品种"湘杂油763"在湖南油菜主产区推广的适宜氮磷钾配比及用量,于2008—2010年连续进行了2次该品种的氮磷钾配比及用量的大田小区试验,研究了不同氮磷钾配比及用量对其生物产量、籽粒产量、油分产量和经济效益的影响。结果表明:氮磷钾配比(N:P2O5:K2O)为1:0.50:0.50(处理B)和氮磷钾配比(N:P2O5:K2O)为1:0.43:0.57(处理G)的处理籽粒产量较高,分别达到2231和2065kg.hm-2,处理B显著高于除G外的其他处理;氮磷钾3种养分中,以氮肥对提高油菜籽粒产量的作用最大,其次为磷肥,作用最小者为钾肥;油分产量及植株生物产量变化规律与籽粒产量基本一致;按照处理B配比,籽粒产值为9816.97元.hm-2、施肥仅1641.23元.hm-2、施肥效益为6741.34元.hm-2,产投比达4.11;研究区域内N:P2O5:K2O=1:0.50:0.50,用量分别180(N)、90(P2O5)和90kg.hm-2(K2O)为较适宜施肥比例及用量。     

硅对受土壤中镉污染的白菜生长和抗胁迫能力的影响

在土培盆栽条件下,硅可提高白菜的地上部鲜重和茎鲜重,但根鲜重下降,叶鲜重略有下降。硅可抑制白菜吸收镉,在0.3、0.6、1.2mg·kg~(-1)镉水平下,施硅可显著降低白菜地上部的镉含量,并在一定程度上提高叶中过氧化物酶(POD)活性,但降低超氧化物歧化酶(SOD)活性。0.5、1.0 g·kg~(-1)硅可提高白菜的叶绿素含量和过氧化氢酶(CAT)活性,降低叶细胞膜透性,从而提高其对镉胁迫的耐受力。较高的硅浓度对植物有一定的毒性,叶绿素含量和CAT活性都下降,细胞膜透性也增加。     

黄腐酸拌种对春小麦产量和水分利用效率的影响

在大田研究了黄腐酸拌种对春小麦产量形成和水分利用效率的影响。实验设４个处理：对照（ＣＫ）,播种前种子不处理;ＦＡ处理：播种前用ＦＡ拌种;ＷＭ处理：浇３０ｍｍ底墒水,覆膜;处理ＷＭＦＡ：浇３０ｍｍ底墒水,覆膜,播种前用ＦＡ拌种。２个覆膜处理均在播种后６２ｄ揭膜。同ＣＫ相比,ＦＡ拌种后,根系生长良好,吸收利用了更多的土壤水分,增加了穗重、单穗籽粒重和收获指数,产量和水分利用效率均显著提高。ＷＭ和ＷＭＦ     

Employment of Rhizobacteria for the Inoculation of Barley Plants Cultivated in Soil Contaminated with Lead and Cadmium

In laboratory experiments, the rhizobacteria Azospirillum lipoferum 137, Arthrobacter mysorens7, Agrobacterium radiobacter 10, and Flavobacterium sp. L30 were found to have a relatively high resistance to the toxic heavy metals lead and cadmium (except that strain L30 was found to be sensitive to Cd). When introduced by means of seed bacterization, the heavy metal–resistant strains actively colonized the rhizosphere of barley plants cultivated in uncontaminated and contaminated soils. In both pot and field experiments, seed bacterization improved the growth of barley plants and the uptake of nutrient elements from soil contaminated with Pb and Cd. The bacterization also prevented the accumulation of Pb and Cd in barley plants, thereby mitigating the toxic effect of these heavy metals on the plants.