Bioremediation of HMX-Contaminated Soil Using Soil Slurry Reactors

Soil in some parts of the Iowa Army Ammunition Plant in Burlington, Iowa, was contaminated with cyclotetramethyleneter-anitramine, commonly known as high melting explosive (HMX). A laboratory treat-ability study was conducted to find out the ability of the native soil bacteria present in the contaminated site to degrade HMX. The results indicated that the HMX can be removed effectively from soil by native soil bacteria through a co-metabolic process. Molasses, identified as an effective co-substrate, is inexpensive, and this factor makes the treatment system cost-effective. The successful operation of aerobic-anoxic soil slurry reactors in batch mode with HMX-contaminated soil showed that the technology can be scaled up for field demonstration. The HMX concentration in the contaminated soil was decreased by 97% in 4 months of reactor operation. The advantage of the slurry reactor is its simplicity of operation. The method needs only mixing and the addition of molasses as co-substrate.     

Compost Soil Piles for Treatment of Oil-Contaminated Soil

A number of diverse technological options are being considered for the remediation of soil contaminated with weathered crude oil in Kuwait. The bioremediation technique involving the use of composting soil piles was selected from among the most appropriate methods and evaluated on a pilot scale. The field test was conducted from November 1992 to September 1993 at the Burgan oil field. Soil piles were constructed from the contaminated soil after amendment with necessary soil additives. The piles were subjected to regular irrigation and turning, and a monitoring program was carried out, including monthly soil sample collection from each pile for the measurement of petroleum hydrocarbon PAHs, soil microbial counts, mineral and metal concentrations. The results obtained showed that the composting soil pile treatment resulted in the reduction of up to 59% total extractable matter of oil contamination within 8 months. This article describes the technology used and summarizes the results obtained.     

Dependence of Soil Respiration on Soil Temperature and Soil Moisture in Successional Forests in Southern China

The spatial and temporal variations in soil respiration and its relationship with biophysical factors In forests near the Tropic of Cancer remain highly uncertain. To contribute towards an Improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured In three successional subtropical forests at the Dlnghuahan Nature Reserve （DNR） In southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and Its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared In successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season （April-September） and with low rates In the cool dry season （October-March）. Soil respiration measured at these forests showed a clear Increasing trend with the progressive succession. Annual mean （± SD） soil respiration rate In the DNR forests was （9.0 ± 4.6） Mg CO2-C/hm^2 per year, ranging from （6.1 ± 3.2） Mg CO2-C/hm^2 per year in early successional forests to （10.7 ± 4.9） Mg CO2-C/hm^2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation In DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture Increased with progressive succession processes. This increase is caused, in part, by abundant respirators In advanced-successional forest, where more soil moisture is needed to maintain their activities.     

Alkaliphilic Soil Actinomycetes

The actinomycete complex of alkaline soils was found to be dominated by alkaliphilic streptomycetes, which showed maximal radial rates of colony growth at pH 8. At pH values of 7 and 10, the growth of these streptomycetes was poor. Alkaliphilic streptomycetes can be morphologically differentiated from other actinomycetes based on their high radial rates of colony growth and increased spore formation in alkaline media as compared to neutral media.     

Acidophilic Soil Actinomycetes

A clear-cut dependence of the distribution of acidophilic actinomycetes on the pH value of soil was established. Acidophilic actinomycetes were found to be present in soils whose pH does not exceed 6.8 (acid forest soils, lowland peaty soil, and ordinary chernozem) and not in slightly alkaline soils (chestnut sodic and alluvial meadow soils). In acid lowland peaty soil, the species diversity of acidophilic streptomycetes was lesser than the species diversity of streptomycetes revealed in the same soil by using neutral medium.     

Vegetation Affects the Relative Abundances of Dominant Soil Bacterial Taxa and Soil Respiration Rates in an Upland Grassland Soil

Plant-derived organic matter inputs are thought to be a key driver of soil bacterial community composition and associated soil processes. We sought to investigate the role of acid grassland vegetation on soil bacterial community structure by assessing bacterial diversity in combination with other soil variables in temporally and spatially distinct samples taken from a field-based plant removal experiment. Removal of aboveground vegetation resulted in reproducible differences in soil properties, soil respiration and bacterial diversity. Vegetated soils had significantly increased carbon and nitrogen concentrations and exhibited higher rates of respiration. Molecular analyses revealed that the soils were broadly dominated by Alphaproteobacterial and Acidobacterial lineages, with increased abundances of Alphaproteobacteria in vegetated soils and more Acidobacteria in bare soils. This field-based study contributes to a growing body of evidence documenting the effect of soil nutrient status on the relative abundances of dominant soil bacterial taxa, with Proteobacterial taxa dominating over Acidobacteria in soils exhibiting higher rates of C turnover. Furthermore, we highlight the role of aboveground vegetation in mediating this effect by demonstrating that plant removal can alter the relative abundances of dominant soil taxa with concomitant changes in soil CO₂-C efflux.     

Biotic and Abiotic Soil Properties Influence Survival of Listeria monocytogenes in Soil

Listeria monocytogenes is a food-borne pathogen responsible for the potentially fatal disease listeriosis and terrestrial ecosystems have been hypothesized to be its natural reservoir. Therefore, identifying the key edaphic factors that influence its survival in soil is critical. We measured the survival of L. monocytogenes in a set of 100 soil samples belonging to the French Soil Quality Monitoring Network. This soil collection is meant to be representative of the pedology and land use of the whole French territory. The population of L. monocytogenes in inoculated microcosms was enumerated by plate count after 7, 14 and 84 days of incubation. Analysis of survival profiles showed that L. monocytogenes was able to survive up to 84 days in 71% of the soils tested, in the other soils (29%) only a short-term survival (up to 7 to 14 days) was observed. Using variance partitioning techniques, we showed that about 65% of the short-term survival ratio of L. monocytogenes in soils was explained by the soil chemical properties, amongst which the basic cation saturation ratio seems to be the main driver. On the other hand, while explaining a lower amount of survival ratio variance (11%), soil texture and especially clay content was the main driver of long-term survival of L. monocytogenes in soils. In order to assess the effect of the endogenous soils microbiota on L. monocytogenes survival, sterilized versus non-sterilized soils microcosms were compared in a subset of 9 soils. We found that the endogenous soil microbiota could limit L. monocytogenes survival especially when soil pH was greater than 7, whereas in acidic soils, survival ratios in sterilized and unsterilized microcosms were not statistically different. These results point out the critical role played by both the endogenous microbiota and the soil physic-chemical properties in determining the survival of L. monocytogenes in soils.     

Soil CO2 Dynamics in a Tree Island Soil of the Pantanal: The Role of Soil Water Potential

The Pantanal is a biodiversity hotspot comprised of a mosaic of landforms that differ in vegetative assemblages and flooding dynamics. Tree islands provide refuge for terrestrial fauna during the flooding period and are particularly important to the regional ecosystem structure. Little soil CO₂ research has been conducted in this region. We evaluated soil CO₂ dynamics in relation to primary controlling environmental parameters (soil temperature and soil water). Soil respiration was computed using the gradient method using in situ infrared gas analyzers to directly measure CO₂ concentration within the soil profile. Due to the cost of the sensors and associated equipment, this study was unreplicated. Rather, we focus on the temporal relationships between soil CO₂ efflux and related environmental parameters. Soil CO₂ efflux during the study averaged 3.53 µmol CO₂ m⁻² s⁻¹, and was equivalent to an annual soil respiration of 1220 g C m⁻² y⁻¹. This efflux value, integrated over a year, is comparable to soil C stocks for 0–20 cm. Soil water potential was the measured parameter most strongly associated with soil CO₂ concentrations, with high CO₂ values observed only once soil water potential at the 10 cm depth approached zero. This relationship was exhibited across a spectrum of timescales and was found to be significant at a daily timescale across all seasons using conditional nonparametric spectral Granger causality analysis. Hydrology plays a significant role in controlling CO₂ efflux from the tree island soil, with soil CO₂ dynamics differing by wetting mechanism. During the wet-up period, direct precipitation infiltrates soil from above and results in pulses of CO₂ efflux from soil. The annual flood arrives later, and saturates soil from below. While CO₂ concentrations in soil grew very high under both wetting mechanisms, the change in soil CO₂ efflux was only significant when soils were wet from above.     

Predominant Catalase-negative Soil Bacteria. I. Streptococcal Population Indigenous to Soil

Streptococci related to Streptococcus sanguis were shown to represent a major segment of the bacterial flora of certain soils. Upon initial isolation, these streptococci were quite pleomorphic and displayed morphological characteristics common to several other genera of bacteria, but after prolonged cultivation on laboratory media the isolates demonstrated a typical streptococcal morphology. It was proposed that a requirement for correction of the control mechanisms affecting growth rate and cell wall synthesis in part might explain the difficulty encountered in isolation of these organisms from soil and their initial pleomorphism and cultural instability. The possible role of these soil organisms as etiological agents of disease and the occurrence of other groups of streptococci in soil were discussed.     

Influence of Soil Organic Matter on Copper Extraction from Contaminated Soil

Column experiments of copper extraction from four contaminated soils characterized by a content of Soil Organic Matter (SOM) ranging from 1% to 25% are presented and discussed. The extraction was performed by flushing the soil with an aqueous solution of a sodium salt of ethylene diamminotetraacetic acid (EDTA). Preliminary tests were performed on a soil containing 25% of organic matter, to investigate the influence of pH, concentration and volumes of EDTA on its chelant action and on the dissolution of SOM. Having selected the optimal conditions for the extraction process, a further series of tests was conducted on the four soils to evaluate the influence of organic content on copper extraction yields. EDTA solutions at 0.01 M, 0.05 M, 0.1 and 0.2 M were injected at 0.33 ml/s; copper and organic matter extraction yield were determined. At a pH of 5, 15 pore volume (PV) of a solution containing 0.05M EDTA, extracted about 99% of copper contained by the soil with the higher organic matter content. Under the same conditions, and for soil with > 6% SOM, extraction yields over 80% were achieved, while at lower organic content, copper extraction was dramatically reduced. This was attributed to the formation of highly stable copper-humate complexes and to their increasingly dissolution that occurred in the soils with higher organic matter level.

Experimental tests performed at different contamination levels (1200 mg/kg, 2400 mg/kg) showed that EDTA extraction effectiveness also depended upon initial soil Cu concentration.     

提高赤红壤旱地生态系统土壤肥力问题的研究

提高赤红壤旱地生态系统土壤肥力问题的研究高志强（福建农业大学土地与环境学系,福州３５０００２）ＳｏｉｌＦｅｒｔｉｌｉｔｙＩｍｐｒｏｖｅｍｅｎｔｏｆＵｐｌａｎｄＬａｔｅｒｉｔｉｃＲｅｄＳｏｉｌＥｃｏｓｙｓｔｅｍ．￥ＧａｏＺｈｉｑｉａｎｇ（Ｄｅｐａｒｔｍ...     

Remediation of Metal-Contaminated Soil by an Integrated Soil Washing-Electrolysis Process

Chelating agents such as EDTA and DTPA are often used to remove metals from soil. However, their toxicity, bio-recalcitrance, and problems with recovery of heavy metal and chelating agents severely limit their applications. A biodegradable chelating agent, LED3A, and two surfactants, SDS and Triton X 100, were evaluated as potential alternatives for remediation of metal-contaminated soil.

LED3A alone only removed 40% of cadmium the addition of surfactant significantly enhanced its cadmium removal capacity up to 80% for a wide range of pH (5 to 11). The enhancement increased with both surfactant concentrations and LED3A concentrations. Because LED3A had a much higher removal capacity for copper, the synergistic effect of surfactant-LED3A mixture was less obvious. Sequential extraction analysis indicated that the LED3A not only removed copper from carbonate and Fe-Mn oxide fraction, but also from organic fractions. A three-dimension electrolysis reactor could effectively recover both metals and LED3A-SDS within thirty minutes. The combined soil washing by LED3A-surfactants and electrolysis provides a potential approach for remediation of copper- and cadmium-contaminated soils.     

Short-Term Response of Soil Bacteria to Carbon Enrichment in Different Soil Microsites

The response of bacteria in bulk soil and earthworm casts to carbon enrichment was studied by an RNA stable-isotope probing/terminal restriction fragment length polymorphism strategy with ¹³C-labeled glucose and acetate. Both the soil microsite status and the carbon enrichment selected rapidly for different active bacterial communities, which resulted in different degradation kinetics. Our study clearly illustrates the biases that are generated by adding C substrates to detect metabolically active bacteria in soil.     

重度盐碱地营造杨树人工林土壤改良效果

为探讨重度盐碱地营造杨树人工林对土壤的改良效果,本实验以黑龙江省肇东市重度盐碱地作为研究对象,采用小穴改良"一字沟"觅食丘式原位修复、小穴改良"十字沟"觅食台式原位修复和小穴改良"井字沟"觅食坛式原位修复的方法对重度盐碱地进行改良。研究结果表明:实施不同改良措施后土壤特性发生了显著变化,土壤pH值、电导率含量显著下降;土壤碳酸根含量显著下降,交换性钙、镁含量显著提高;土壤胡敏酸和壳聚糖含量明显提高,土壤肥力增加。因此,本研究所采用的三种不同的改良措施具有良好的改良效果。     

Abundant Microorganism in Soil

The presence in soil of large numbers of a catalase-negative, microaerophilic, coccoid microorganism was demonstrated. Use of media of high nutrient value, without incorporation of inhibitors, and growth in the absence of antagonistic microorganisms were utilized to isolate this organism from soil dilutions greater than those providing growth by other means. The organism described does not grow on soil extract agars and is missed by conventional counting techniques for soil organisms. On the basis of morphological and growth characteristics, this organism appears to have at least some taxonomic relationships to the families Actinomycetaceae and Mycobacteriaceae. It is proposed that this organism makes up much of the coccoid microflora of soil as observed by light and ultraviolet fluorescence microscopy.     

Soil mycoflora of Peru

A qualitative survey of the yeasts and filamentous fungi in 29 Peruvian soils was undertaken. Using the dilution plate method, 4884 isolates were obtained. Four per cent were sterile and 7 % were unidentified. The remaining isolates belonged to 53 genera, 159 species, and 4 varieties of which 14 were phycomycetes, 22 were ascomycetes, and 128 were deuteromycetes.Absidia repens, Helicodendron westerdijkae, Chaetomium brasiliense, Coniochaeta tetraspora, Podospora castorinospora, andP. nannopodalis were among the unusual species isolated. Distribution of certain fungal taxa was related to soil pH, altitude, and/or vegetation. Some changes in the population due to storage of the samples are described.

---

Zusammenfassung Eine qualitative Übersicht von Hefen und Fadenpilzen in 29 peruanischen Bodenproben wurde unternommen. Mit der Verdünnungsplattenmethode sind 4884 Isolierungen erhalten worden. Vier Prozent waren steril und sieben blieben unidentifiziert. Die isolierten Stämme gehörten 53 Gattungen, 159 Arten und 4 Varietäten an, unter welchen 14 Phycomyceten, 22 Ascomyceten und 128 Deuteromyceten vorkamen.Absidia repens, Helicodendron westerdijkae, Chaetomium brasiliense, Coniochaeta tetraspora, Podospora castorinospora, undP. nannopodalis als ungewöhnliche Arten sind isoliert worden. Die Verbreitung gewisser Pilze war von pH des Bodens, der Höhe und von der Vegetation abhängig. Gewisse Abwechslungen in der Pilzbevölkerung nach Aufbewahrung der Bodenproben sind beschrieben.