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1.
Biological Degradation of 2,4-Dinitrotoluene in a Continuous Bioreactor and Kinetic Studies Experimental results on the aerobic biological degradation with complete mineralization of 2,4-dinitrotoluene (2,4-DNT) are presented. A culture of Pseudomonas sp. DNT from Spain and Nishino was used. The degradation was examined with batch cultures for the determination of kinetic and stoichiometric coefficients. Further experiments were carried out with a continuous culture in a fixed-bed reactor with recirculation in order to obtain high degradation rates. The reactor was packed with ceramic Raschig rings (55 mL) and had a liquid reaction volume of 160 mL. The minimal salt media from Spanggord et al. with and without (NH4)2S)4 as nitrogen source was used as substrate. 2,4-DNT was the sole source of carbon and energy. From batch experiments a yield coefficient YB/S = (0.30 ± 0.05) g g?1 was calculated from a mass balance of the elements. This result was confirmed by calculations using literature data. Fitting the experimental data to the Monod equation, μmax = 0.1 h?1 and KS = 0.01…0.03 mmol L?1 were obtained. It was demonstrated by batch experiments that 2,4-DNT is not only used as the source of carbon and energy but also as the nitrogen source. In the fixed-bed reactor, a degradation of 92…97% was reached with a maximal 2,4-DNT load of 95 mg L?1 h?1. The rate of continuous degradation could be described by a pseudo-first-order reaction (k = 9.73 h?1). The complete mineralization of 2,4-DNT was verified by the measurement of DOC and the formed nitrite and nitrate. The formed nitrite was nitrified simultaneously. It was demonstrated by these experiments that large scale biological treatment of industrial effluent containing 2,4-DNT may be successful.  相似文献   

2.
To remove nitro aromatic compounds (NACs) from 2,4,6‐trinitrotoluene (TNT) red water, large‐pore‐size (pore size = 200 nm) polystyrene (PSt) microspheres were activated with chloroacetyl chloride followed by reaction with 1,2‐ethanediamine (EDA). Fourier transform IR analyses showed that the amino group was introduced onto PSt microspheres. Determination of the total amino group and primary amino densities suggested that the imino group was the functional group of EDA–PSt. Scanning electron microscope images and mercury porosimetry measurements indicated that the pore structure was well maintained during the reaction. After adsorption with EDA–PSt, 98.5% chemical oxygen demand and 99% acute toxicity of TNT red water was removed. As shown by HPLC and GC–MS, all the neutral and acid NACs in TNT red water were removed by EDA–PSt, while the basic NACs were not. The results showed that hydrogen bonding and electrostatic attraction were involved in adsorption. The adsorbed neutral and acid NACs were eluted using methanol and 0.1 mol L?1 NaOH, respectively.  相似文献   

3.
The toxicity of transformation products of 2,6-dinitrotoluene (2,6-DNT) and 2,4,6-trinitrophenol (picric acid) were assessed in spiked sandy and fine-grained marine sediments and in seawater. Toxicity of pore water from sediments spiked with 2,6-DNT decreased for the macro-alga, Ulva fasciata, zoospores as biotransformation proceeded, but increased for the copepod, Schizopera knabeni, nauplii. The primary biotransformation product of 2,6-DNT, 2-amino-6-nitrotoluene, was also more toxic than the parent compound to copepod nauplii, but not to alga zoospores, in spiked seawater tests. Two biotransformation products of picric acid, picramic acid and 2,4-DNP, were more toxic than their parent compound. Porewater toxicity from picric acid-spiked sediments decreased significantly at the end of six-months incubation. Fine-grained sediment spiked with either ordnance compound had lower toxicity than its sandy counterpart after six months, suggesting faster microbial transformation in the former and production of less toxic products. Photo-transformation of 2,6-DNT in seawater resulted in a reduction in toxicity.  相似文献   

4.
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5.
A number of samples of polyvinyl chloride (PVC) well casings used for ground water monitoring that varied in schedule, diameter or manufacturer were placed in contact with low concentrations of aqueous solutions of TNT, RDX, HMX and 2,4-DNT for 80 days. Analysis indicated that there was more loss of TNT and HMX with the PVC casing than with the glass controls, but that the amount lost was, for the most part, equivalent among different types. A second experiment was performed to determine if these losses were due to sorption or if biodegradation was involved. Several different ground water conditions were simulated by varying salinity, initial pH and dissolved oxygen content. The only case where there was an in-creased loss of any substance due to the presence of PVC casing was with the TNT solution under non-sterile conditions. The extent of loss was small, however, considering the length of the equilibration period. This increased loss is thought to be associated with increased microbial degradation rather than sorption. Several samples of PVC casing were also leached with ground water for 80 days. No detectable interferences were found by reversed-phase high performance liquid chromatography (HPLC) analysis. Therefore, it is concluded that PVC well casings are suitable for monitoring ground water for the presence of these munitions.  相似文献   

6.
Toxicological and chemical studies were performed with a silty and a sandy marine sediment spiked with 2,6-dinitrotoluene (2,6-DNT), 2,4,6-trinitrophenylmethylnitramine (tetryl), or 2,4,6-trinitrophenol (picric acid). Whole sediment toxicity was analyzed by the 10-day survival test with the amphipod Ampelisca abdita, and porewater toxicity tests assessed macro-algae (Ulva fasciata) zoospore germination and germling growth, sea urchin (Arbacia punctulata) embryological development, and polychaete (Dinophilus gyrociliatus) survival and reproduction. Whole sediments spiked with 2,6-DNT were not toxic to amphipods. The fine-grained sediment spiked with tetryl was also not acutely toxic. The tetryl and picric acid LC50 values in the sandy sediment were 3.24 and 144 mg/kg dry weight, respectively. The fine-grained sediment spiked with picric acid generated a U-shaped concentration-response curve in the amphipod test, with increased survival both in the lowest and highest concentration. Grain-size distribution and organic carbon content strongly influenced the behavior of ordnance compounds in spiked sediments. Very low concentrations were measured in some of the treatments and irreversible binding and biodegradation are suggested as the processes responsible for the low measurements. Porewater toxicity varied with its sedimentary origin and with ordnance compound. The sea urchin embryological development test tended to be the least sensitive. Tetryl was the most toxic chemical in all porewater tests, and picric acid the least toxic. Samples spiked with 2,6-DNT contained a degradation product identified as 2-methyl-3-nitroaniline (also known as 2-amino-6-nitrotoluene), and unidentified peaks, possibly degradation products, were also seen in some of the picric acid- and tetryl-spiked samples. Degradation products may have played a role in observed toxicity.  相似文献   

7.
This work seeks to understand how the balance of abiotic and biotic kinetic processes in sediments control the residual concentration of TNT in marine systems after release from ocean-dumped source. Kinetics of TNT disappearance were followed using marine sediments at different temperatures and under both biotic and presumably abiotic conditions (through sodium azide addition). Sediments exhibiting the highest rate of TNT disappearance under biotic conditions also exhibited the highest sorption affinity for TNT under abiotic conditions. Significant temperature dependence in the abiotic processes was observed in the diffusion coefficient of TNT and not sediment sorption affinity. At higher temperature, kinetics of biotic processes outpaced abiotic processes, but at low temperature, kinetics of abiotic processes were much more significant. We concluded that the differential influence of temperature on the kinetics of abiotic and biotic processes could provide distinguishing predictions for the potential residual concentration of TNT contamination in marine-sediment systems.  相似文献   

8.
Phosphorus limitation of bacterial growth in high Arctic lakes and ponds   总被引：4，自引：0，他引：4  
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9.
In situ bioremediation is being considered to optimize an existing pump‐and‐treat remedy for treatment of explosives‐contaminated groundwater at the Umatilla Chemical Depot. Push‐pull tests were conducted using a phased approach to measure in situ hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) and 2,4,6‐trinitrotoluene (TNT) degradation rates associated with various carbon substrates. Phase I included short‐duration transport tests conducted in each well to determine dilution rates and retardation factors for RDX and TNT. Phase II included aquifer “feedings” conducted by injecting 150 gallons of treated site groundwater amended with ethanol, corn syrup, lactose or emulsified oil (concentrations 10, 25 and 27 mM, respectively; 12% by volume for emulsified oil). Wells received up to 6 substrate “feedings” over the course of 3 months followed by monitoring dissolved oxygen, nitrate, Fe(II), and sulfate to gauge in situ redox conditions as indicators of anaerobic microbial activity. Phase III included push‐pull tests conducted by injecting 150 gallons of site groundwater amended with approximately 1000 µg/L RDX, 350 µg/L TNT, carbon substrate and a conservative tracer, followed by sampling over 8 d. Corn syrup resulted in the best RDX removal (82% on average) and the largest RDX degradation rate coefficient (1.4 ± 1.1 d?1). Emulsified oil resulted in the best TNT removal (99%) and largest TNT degradation rate coefficient (5.7 × 10?2 d?1). These results will be used to simulate full‐scale in situ bioremediation scenarios at Umatilla and will support a go/no‐go decision to initiate full‐scale bioremediation remedy optimization.  相似文献   

10.
Studies of carbon sources in plankton communities are important because carbon content has become the main currency used in functional studies of aquatic ecosystems. We evaluated the contribution to the total organic carbon pool from different plankton communities (phytoplankton, bacterioplankton, and zooplankton – C-biota) and its drivers in eight tropical hydroelectric reservoirs with different trophic and hydrological status and different physical features. Our systems were separated into three groups based on trophic status and water residence time: (i) mesotrophic with low residence time (ML); (ii) mesotrophic with high residence time (MH); and (iii) eutrophic with low residence time (EL). Our hypothesis that reservoirs with low water residence times and low nutrient concentrations would show the lowest C-biota was supported. Phytoplankton carbon (C-phy) showed the highest concentrations in the EL, followed by MH and ML systems. The EL group also showed significantly higher zooplankton carbon (C-zoo). No significant difference was observed for bacteria carbon (C-bac) among the three system groups. In addition to trophic status and water residence time, regression analyses revealed that water temperature, light, pH, and dissolved organic carbon concentrations were the main drivers of plankton communities in these large tropical hydroelectric reservoirs.  相似文献   

11.
The ability of the two synthetic marine biotic indices, AMBI and M-AMBI, to account for changes in the ecological quality of coastal soft bottoms of Reunion Island according to disturbances was assessed from macrobenthic samples collected in five sectors between 1994 and 2004. Samples were collected under non-perturbed conditions and at two sites subjected to heavy organic enrichment. Both indices are based on a classification of macrofauna into ecological groups (EG), and their transfer to tropical waters required some adaptations. These indices proved efficient in detecting a degradation of habitat quality. Their use resulted in the classification of all sites sampled between 1996 and 1998 as "good" or "high". M-AMBI nevertheless tended to result in the attribution of a slightly worse ecological quality status than AMBI. Together with an update of the EG species list for the Indian Ocean area, our results support the extension of both indices for the assessment of tropical soft bottoms.  相似文献   

12.
Biochemical reaction rates, metabolic rates, and other rates of biological activity increase exponentially with temperature. It has thus been hypothesized that toxicity to chemical contaminants may increase from polar to temperate to tropical species; however, until recently, polar data to test this hypothesis were not available. This study examined differences in the acute sensitivities of marine invertebrates to four metals (Cu, Cd, Zn, Pb) for polar, temperate and tropical species; data deficiencies for polar regions prohibited comparisons using chronic end-points or other chemicals. Differences between the three geographic regions were not predictable based on temperature (other factors such as differences in dissolved organic carbon concentrations also affect toxicity). There appears to be no universal, predictable pattern of increased toxicity from polar to tropical regions. Toxicity data from one geographic region will not be universally protective of other regions.  相似文献   

13.
Polyhydroxyalkanoates (PHAs), environmental friendly polyesters, can be produced by a wide range of microorganisms in nutrient‐limiting conditions. In the present study a new bacterial strain, able to produce high quantities of poly‐3‐hydroxybutyrate (PHB), is isolated from contaminated soil. The isolate is characterized and identified as Bacillus cereus Y23, based on morphological, physiological characteristics, and 16S ribosomal RNA gene sequences. PHB production is evaluated using different carbon and nitrogen sources and nutritional and culture conditions are optimized. The highest PHB production of 5.12 g L?1 was obtained in growth medium containing fructose and ammonium sulfate at a C/N ratio of 30, 0.3% yeast extract, 4.5 g L?1 phosphate solution, pH 7, inoculum size of 0.3%, and agitation rate of 150 rpm after 48 h of incubation at 32 °C. The PHB production decrement can be attributed to the intracellular utilization of the polymer during the stationary phase of the cellular growth and to the sporulation process. The presence of the main functional groups of PHB polymer is verified by Fourier‐transform infrared analysis. At optimum conditions, B. cereus Y23 turned out to be a good candidate for industrial production of PHB since it accumulates up to 67.9% of its dry weight.  相似文献   

14.
Feeding interactions among functional feeding groups (FFGs) of macroinvertebrates are robust indicators of aquatic ecosystem interactions. They provide information regarding organic matter processing, habitat condition and trophic dynamics. In tropical rivers with pronounced wet and dry seasons, macroinvertebrate based ecological monitoring tools are explicitly focused on metrics and indices, while ignoring interactions of FFGs. Therefore, the objective of this study was to investigate the functional feeding type metrics, diversity indices and feeding interactions among FFGs of macroinvertebrates along the water pollution gradient in Gilgel Gibe watershed, Ethiopia. Water quality parameters and macroinvertebrate community attributes were assessed for samples collected from upstream sites (15 sites), urban-impacted stretches (12 sites) and wetland-affected river zones (7 sites) of the watershed during the rainy (July) and dry (February) seasons. To understand the effect of pollution on the feeding interactions, stable carbon and nitrogen isotopes were analyzed. Macroinvertebrate-based diversity indices and functional feeding type metric showed deterioration of ecological integrity at the urban-impacted sites and substantial recovery in the wetland-affected downstream sites. Omnivorous feeding behavior of macroinvertebrates was noted for the upstream sites, whereas clear trophic guilds of FFGs were suggested for the wetland-affected river zones by the stable isotope results. The results of pollution gradient analysis and feeding interactions among FFGs revealed that the urban-impacted sites showed weaker interactions when compared to upstream and wetland influenced sites. This affirms the potential importance of feeding interactions among FFGs of macroinvertebrates in water quality monitoring.  相似文献   

15.
Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators or tracers in seagrass ecosystem studies. We focus on both the use of natural isotope abundance as food web integrators or environmental tracers and on the use of stable isotopes as experimental tools. As ecosystem integrators, stable isotopes have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable isotopes have proven their utility in sewage impact measuring and mapping. However, to make such environmental studies more comprehensible, future works on understanding of basic reasons for variations of N and C stable isotopes in seagrasses should be encouraged. At least, as experimental tracers, stable isotopes allow the study of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem.  相似文献   

16.
梯级筑坝对河流水环境演化的影响是国内外关注的热点.小型山区河流高密度梯级开发对水体生源要素的空间格局以及水环境演化的累积影响特征尚不清楚.以重庆市五布河为研究对象,对流域内8个“河流—水库—下泄水”交替系统中表层水体理化因子及碳(C)、氮(N)、磷(P)形态组成进行季节性监测,探讨了梯级筑坝对小型河流生源要素空间格局及水体富营养化风险影响的累积特征及驱动机制.结果表明：梯级水电开发对五布河流域水生生境和生源要素空间分配的影响具有潜在的累积效应,各库区水体碳氮磷浓度均呈逐级增加的空间规律;水库段的有机碳及不同形态的氮、磷浓度均高于入库河流,因此水体养分浓度呈现出河段尺度(即单个河流—水库—下泄水系统)和流域尺度(即上游至下游)耦合的空间变异模式.上游水库中溶解性氮、磷的再释放及下泄输移能够补给下游库区,加之下游水库泥沙对氮、磷的吸附—沉积作用的减弱,导致水体氮、磷总量及溶解性氮、磷的占比沿程增加,呈现梯级筑坝对水环境演化的累积影响.梯级筑坝影响下河流碳氮磷总量的相关性减弱,而溶解性养分间的相关性增强,形成了特殊的养分协同演化;水库群之间水力滞留时间的差异与水体碳氮磷浓度具有较好的线性关系...  相似文献   

17.
The temporal variations of the superficial (0–1 cm) sedimentary organic matter were studied at a depth of 26 m on the continental shelf of the Gulf of Lions (northwestern Mediterranean). The samples were analyzed for total organic carbon, coarse organic carbon (>40 μm), hydrolyzable organic carbon, nitrogen, total amino acids, total and individual sugars (HPLC), lignin-derived compounds (HPLC) and kerogens (acid-soluble, humic substances and humin). Seasonal variations of the organic compounds are related to the sedimentological, hydrodynamical and physico-chemical environmental conditions.The mean annual values of the different organic compounds analyzed show the low quantities and their evolved character at the sediment-water interface: 0.5% total org C (TOC) (d.w.), 0.049% N (d.w.), CN: 11.2, coarse org C (COQ: 62% of TOC, hydrolyzable org C: 45% TOC. The labile compounds represent a low percentage of the total organic matter (TOM), amino-acids: 12% of TOM and sugars: 5% of TOM. The relative proportions of soluble (humic) and insoluble kerogens (humin), respectively 6% and 94% of TOC are typical of a highly evolved organic matter. The large contribution of plant remains confirmed by the high proportion of COC, corresponds to a low proportion of humic substances and a high degree of condensation (HC = 1.3). The infrared spectroscopy determination of the functional groups of the humic substances permits us to confirm both autochtonous (marine) and allochtonous (terrestrial) sources of organic matter in the Têt prodeltaïc accumulation area. Numerous functional groups identified reveal the fresh quality of the organic inputs at the sediment-water interface. Aliphaticity is well marked and nitrogenous compounds (1 and 2 amines) correspond to autochtonous production (in spring: phyto- and zoo-planktonic blooms in the euphotic zone; in summer: primary production under the thermocline and phytobenthic blooms). Sugars are well represented, but from two origins: phytoplanktonic, and issue from terrestrial high plants (ligno-cellulosic complexes). The aromatic functional groups are well identified (aromatic ether, phenol) as are the markers of a large contribution of terrestrial organic matter.The active hydrodynamical (resuspension) and biological, (consumption, bioturbation) events participate in the frequent reworking of the superficial deposits (muddy-silts) and, consequently, the active degradation (oxidization) of the organic matter. The more labile organic matter is rapidly consumed by the intense biological benthic activity. The organic C content is low (0.5% d.w.) except during the autumnal input (2.5% d.w.). This input (8 cm thick) disappears one month later, because of the resuspension induced by littoral currents. This same phenomenon induces during all the year the reworking of the first centimeter of the deposit. In terms of budget of the carbon cycle in the coastal area, this active hydrodynamical environment shows the supremacy of the carbon degradation over its burial.  相似文献   

18.
The stability of soil organic carbon （SOC）,as it relates to resistance to decomposition,is important for greenhouse gas emission and climate change.However,the SOC stabilization and its related influencing factors subjected to water erosion remain uncertain.The objective of the current study was to determine the SOC stability under long-term water erosion and to investigate the link between SOC stability and edaphic factors.Soil samples from eroded,depositional,and control sites in a closed wate...  相似文献   

19.
Total organic carbon (TOC), total nitrogen (TN) and their δ(13)C and δ(15)N values were determined for 42 surface sediments from coastal Bohai Bay in order to determine the concentration and identify the source of organic matter. The sampling sites covered both the marine region of coastal Bohai Bay and the major rivers it connects with. More abundant TOC and TN in sediments from rivers than from the marine region reflect the situation that most of the terrestrial organic matter is deposited before it meets the sea. The spatial variation in δ(13)C and δ(15)N signatures implies that the input of organic matter from anthropogenic activities has a more significant influence on its distribution than that from natural processes. Taking the area as a whole, surface sediments in the marine region of coastal Bohai Bay are dominated by marine derived organic carbon, which on average accounts for 62±11% of TOC.  相似文献   

20.
This study combined bacterial incubation and hydrogeochemical methods to investigate denitrification in the surface water, top soil (0–20 cm), and shallow groundwater of the Ochi wetland in Japan. Surface water was rich in nitrate (40 mg/l) and denitrifying bacteria (700 per ml). Three functional zones in the wetland were identified in the top soil and shallow groundwater. In the upstream portion of the wetland (Zone I), the counts of denitrifying bacteria in top soil increased from 5200 to 14 970 per ml and nitrate decreased from 25·4 to 1·8 mg/l. Organic carbon concentrations decreased as sulfate increased from 4·0 to 9·6 mg/l in this zone. In the middle‐stream of the wetland (Zone II), all concentrations of major anions, iron, organic carbon, and total nitrogen content in top soil were relatively constant, but the counts of denitrifying bacteria increased up to 70 200 per ml. In the downstream portion of the wetland (Zone III), complete removal of nitrate resulted in sharp reduction of counts of denitrifying bacteria. Correspondingly, dissolved oxygen (DO), organic carbon, and total nitrogen increased in this zone. Counts of denitrifying bacteria were lower in shallow groundwater than in top soil; nitrate concentrations in shallow groundwater were also very low in this zone. DO and the oxidation/reduction potential data suggest that groundwater flows to the surface along an extended flow path, thus providing nitrate for the denitrifying community. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

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