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1.
《Applied soil ecology》1999,11(1):79-90
Escherichia coli K12 strain (J5-3/RP4) persisted in sandy loam for more than 70 days when incubated at 10°C or 4°C. It decreased to below the level of detection within 20 days when incubated at 25°C. No loss of multi-resistance plasmid RP4 from the E. coli cells was detected during incubation in soil. There was a positive relation between the bacterial inoculum size and the following increase of the protozoan numbers in the soil. When soil microcosms were amended with an eukaryotic inhibitor, the period of survival was increased. These observations indicate a direct involvement of protozoa in the decline of E. coli in soil. Transfer of plasmid RP4 from E. coli donor bacteria to indigenous bacteria in soil was detected already 24 h after addition of the E. coli K12 donor strain. The efficiency of transfer during the first 48 h was approximately 10−6 transconjugants per donor. Inhibition of protozoan predation increased the number of transconjugants appearing in the soil, but the transfer efficiency per donor was not affected by the decreased predation. No transfer could be detected when the donor strain was washed and resuspended in saline before addition to the soil, but transconjugants were detected in this experiment when nutrients (LB) were supplemented after two days of incubation. Plasmid RP4 was maintained in the transconjugant soil bacteria throughout the experiment. The data presented here indicate that the indigenous bacteria in soil may serve as a sink for plasmidborne traits.  相似文献   

2.
Crushed limestone was tested as a sealing liner for organic wastewater storage facilities. This material was compacted in laboratory columns and exposed in quadruplet to three levels of wastewater total solids (TS of 0.6, 1.3 and 2.6%). A fourth set of quadruple columns was used to monitor the total nitrogen (TN) loading rate using 1.3% TS wastewater. The crushed limestone cores measured 310 mm in depth by 98 mm in diameter and were exposed to a typical wastewater depth of 290 mm. Wastewater TS and ambient temperatures had a marked effect on seepage and TN loading rates. If the wastewater contains at least 1.3% TS, the seepage and N loading rate can be limited to 2 × 10-8 m s-1 and 200 mgN m-2 d-1, respectively. Ambient temperatures below 5 °C caused the TN loading rate to increase 7 fold, while those above 5 °C favoured nitrifying and denitrifying activity, thereby reducing seepage TN.  相似文献   

3.
Field study on colloid transport using fluorescent microspheres   总被引：1，自引：1，他引：0  
Understanding colloid movement through the vadose zone is important, because colloids may facilitate transport of some less mobile contaminants. Experimental evidence of colloid transport in the vadose zone, especially at the field scale, is rare. We developed and tested a method to detect and quantify local concentrations of fluorescent microspheres (MS) with a diameter of 1 μm in unsaturated soil based on fluorescent microscopy. The detection limit was 400 × 106 MS kg?1 field‐moist soil for an automated counting method, and 20 × 103 MS kg?1 for manual counting. To test the method in the field, we applied a 40‐mm pulse with an input concentration of 14.6 × 109 MS litre?1 on two plots during 6 hours, together with bromide (Br?) and the food dye Brilliant Blue (BB). The concentrations of MS were determined on horizontal cross‐sections by a randomly distributed sampling scheme, either directly after application or 90 days after application and a rainfall of 100 mm. Mass recoveries for the MS of 85 and 65% were acceptable in view of the field conditions. Even after infiltration of particle‐free water, the largest MS concentrations were measured at the soil’s surface, which pointed at physical retention mechanisms. An additional selective sampling of hydrologically active preferential flow pathways, guided by the dye infiltration patterns, revealed that the MS were transported to similar depths as BB, that is 0.80 m directly after irrigation and 1.7 m after 90 days. This implies that also a small fraction of the particulate tracers was rapidly transported to larger depths, regardless of their physico‐chemical properties.  相似文献   

4.
The adsorption of four dyestuffs onto bagasse pith has been studied. A method has been presented for the prediction of concentration decay vs time. The model is based on external mass transfer and pore diffusion and enables the external transport coefficients and the effective diffusivities to be determined. Constant mass transport. coefficients were obtained for each dye-pith system to correlate the effects of varying the initial dye concentration and pith mass. The external mass transfer coefficients are 1.4 × 10?2, 1.24 × 10?2, 1.5 × 10?3, and 2.5 × 10?3 cm s?1 and the effective diffusivities are 6.5 × 10?6, 2.6 × 10?6, 4.5 × 10?7, and 5.7 × 10?7 cm2 s?1 for Basic Blue 69, Basic Red 22, Acid Blue 25, and Acid Red 114, respectively.  相似文献   

5.
Horizontal gene transfer is useful for enhancing bioremediation through gene bioaugmentation. However, factors affecting transfer of degradative plasmids have not been systematically addressed. To this end, plasmid transfer experiments were performed using a TOL-like plasmid carrying the gene encoding for catechol 2,3-dioxygenase (C23O) between two soil bacteria under different conditions. Transfer frequency increased with air temperature in the range of 10–35 °C and reached 6 × 10−4 transconjugants per donor cell at 35 °C. The transfer frequency detected at soil depth 5–10 cm was significantly higher (p < 0.05) compared with other depths. Addition of 5–75% LB in the microbial inoculum promoted plasmid transfer frequencies. Addition of phenol to the experimental system resulted in significantly higher transfer frequency (p < 0.05) compared with no addition. Transfer frequency heat-moisture in loam was significantly higher (p < 0.05) than in other soils. The highest transfer frequency was found in the experiment containing tomato seedlings, with up to about 1.3 × 10−3 transconjugants per donor cell. Corn and wheat seedlings also led to significantly higher transfer frequencies (p < 0.05) compared with no plants. Furthermore, C23O activities of transconjugants formed under different conditions were measured, as a surrogate measure of the activity of transconjugant. Transfer temperature, soil and plant types had a minor influence on activities of transconjugants. Topsoil (0–5 cm) transconjugants expressed C23O more efficiently under normal incubation condition, but less efficiently when soils incubated with excessive LB medium concentrations, and in the absence of phenol in soil. These results suggested that transfer temperature, soil depth, dilutions of LB broth, phenol content, and soil and plant types had important effects on transfer of the TOL-like plasmid in soil, and some factors also affected activities of transconjugants.  相似文献   

6.
该文采用水平扩散池观测了水溶性盐阳离子在工程黄土中的扩散过程。结果表明：水溶性盐阳离子在土壤中的扩散性因离子种类而异,Ｃａ＾２＋的扩散系数最高,Ｍｇ＾２＋,Ｎａ＾＋,Ｋ＾＋依次降低,其由两个模型测定的平均值分别为２．６９２８×１０＾－６,２．３１２７×１０＾－６,１．６７３０×１０＾－６,０．４５０４×１０＾０－６ｃｍ＾２／ｓ。在距源溶液较近时,土壤胶体交换性Ｋ＾＋,Ｎａ＾＋,Ｍｇ６２＋均明显升高  相似文献   

7.
Two methods for the determination of DNA have been adapted for use on the bacterial fraction of an organic soil, obtained by fractionated centrifugation. The. soil contained about 1.1 × 1010 bacteria g?1 dry weight when counted by fluorescence microscopy. One method was based on the reaction with 3,5-diaminobenzoic acid 2HCl, and the other on the specific reaction of the antibiotic mithramycin with double-stranded DNA. For the first method, about 8 × 108 cells were required and for the second, about 4 × 109. The analytical results with the two methods agreed well. As an average of several determinations, an amount of 8.4 fg (10?15g) DNA per bacterial cell was found when the cells were counted by fluorescence microscopy. This is in the upper size range of bacterial genomes. showing that virtually all microscopically counted bacteria in this soil contain DNA. The total amount of DNA was about 90μg g?1 soil dry weight.  相似文献   

8.
Long-term changes in carbon and nitrogen storage in the top 100 em layers of soils from different physiographic units in Bangladesh were evaluated using 460 soil samples from 43 profiles collected in 1967 and 1994/95. The study area consisted of ten physiographic units, viz.: Old Himalayan Piedmont Plain (OHP), Tista Floodplain (TF), Barind Tract (BT), Ganges Floodplain (GF), Madhupur Tract (MT), Brahmaputra Floodplain (BF), Meghna River and Estuarine Floodplain (MF), Surma-Kushiyara Floodplain (SKF), Northern and Eastern Piedmont Plain (NEP), and Chittagong Coastal Plain (CCP).

During the period 1967–1995, mean values of soil carbon and nitrogen declined by 16.2 t C ha-1 and 1.38 t N ha-1 in Bangladesh. The total carbon and nitrogen budgets showed a fall of 42.8 × 106 t C and 3.36 × 106 t N within the 27 y period in Bangladesh. All the physiographic units showed a decline in carbon and nitrogen contents except for BT which showed an increase of 3.76 t C ha-1 and 0.77 t N ha-1 for these elements. MT showed the highest decline in carbon (30.5 t C ha-1) and nitrogen (3.25 t N ha-1). The lowest decline in carbon was observed in SKF (7.18 t C ha-1) while the same applied to nitrogen in GF (0.50 t N ha-1). The other physiographic units showed a moderate decline in the contents of these elements.

Based on the land area occupied by the sampled soil series of each physiographic unit, GF showed the highest decline of 13.7×106 t C and a moderate decline of 0.52 × 106 t N. Decrease in the carbon level for BF was moderate (9.31 × 106 t C) but the decline in the nitrogen level was the highest (0.95 × 106 t N). Decrease in the amount of carbon and nitrogen stored for the other physiographic units was: OHP (0.67 × 106 t C, 0.03 × 106 t N), TF (2.54 × 106 t C, 0.25 × 106 t N), MT (4.28 × 106 t C, 0.45 × 106 t N), MF (6.06 × 106 t C, 0.61 × 106 t N), SKF (2.87×106 t C, 0.24×106 t N), NEP (2.68×106 t C, 0.22×106 t N), and CCP (0.81 × 106 t C, 0.11 × 106 t N). Increase in carbon and nitrogen contents was only observed in BT (0.08 × 106 t C, 0.02 × 106 t N).  相似文献   

9.
Tetrahymena pyriformis cultures were maintained when transferred serially in solutions containing 105 to 107Klebsiella pneumoniae cells.ml?1, bacterial numbers that were observed to persist in the presence of protozoa. The number of cells of one strain of K. pneumoniae surviving predation in solution was essentially the same in the absence of an alternative prey as in the presence of a second K. pneumoniae strain. Toxins deleterious to protozoa did not appear as the animal consumed the bacteria. T. pyriformis reduced the abundance of Escherichia coli from about 108 to 106.ml?1. but the latter number persisted for 15 days; however, in solutions containing chloramphenicol, the abundance of E. coli fell to 590 cells. ml?1 in 15 days. In solutions containing the antibiotic, T. pyriformis reduced the Rhizobium sp. population from more than 106 to less than 103 cells in 10 days and K. pneumoniae from more than 108.ml?1 to zero in 18 days. An appreciable decline in abundance of these bacteria did not occur in the antibiotic-amended liquid free of protozoa. T. pyriformis did not greatly reduce Rhizobium sp. numbers when both were added to irradiated soil, but the predator caused the bacterial population to decline from 4 × 108 to fewer than 105.g?1 in 16 days in chloramphenicol-treated soil. Colpoda sp. inoculated with Rhizobium sp. into soil sterilized by autoclaving only reduced the prey abundance from 109 to 108.g?1, but the protozoan caused the bacterial population to fall to about 100.g?1 in 15 days in the presence of the antibiotic. The population of Rhizobium sp. added to nonsterile soil dropped from in excess of 108 to 6 × 106.g?1 in 29 days. but it declined to 550. g?1 in the same period when chloramphenicol was also introduced. It is concluded that the ability of these bacteria to maintain themselves in solution and in soil is governed by their capacity to reproduce and replace the cells consumed by predation.  相似文献   

10.
采用薄层营养液膜技术(NFT)培育多年生黑麦草(Lolium perenne L),以草带为植物滤器净化5种不同配置的富氮废水,废水10 d更换一次.试验结果表明在短期内(2d),TAN、NO-2-N和NO-3-N的去除量均在本身高水平而其他成分低水平的试验组达到最高,4组非离子氨UIA的净化率均高于99%.所有废水的pH值在2 d后均被控制在6.5～8.0.以上述3种氮90%的净化率为目标,废水G3(初始浓度为TAN:40 mg·L-1,NO-2-N:40 mg·L,NO-3-N:10 mg·L-1)和CK(仅在26.77 L自来水中加入18.36 g四水硝酸钙)需2d,废水G4(TAN:40 mg·L-1,NO-2-N:4 mg·L-1,NO-3-N:10 mg·L-1)需4 d,废水G1(TAN:140 mg·L-1,NO-2-N:40 mg·L-1,NO-3-N:80 mg·L-1)、废水G2(TAN:140mg·L-1,NO-2-N:40 mg·L-1,NO-3-N:10 mg·L-1)仅TAN和NO-2-N在6 d内完成.试验结束时G3草净增长最高(169.3 mm),并获得最大干草产量0.205 kg·m-2,G4获得最大鲜草产量1.48 kg·m-2.  相似文献   

11.
Sadiq  Rehan  Husain  Tahir  Kar  Sudip 《Water, air, and soil pollution》2002,138(1-4):123-140
Chlorine is the most commonly used disinfectant for watertreatment but when in contact with organic precursors it producestoxic compounds known as trihalomethanes (THMs). Chloroform isthe most commonly occurring THM and constitutes approximately90% of the THM concentration. A study was conducted inNewfoundland for estimating the chloroform content in thedrinking water supplies in Clarenville and St. John's. Thesampling program was conducted in two stages, July and October-November. Higher concentrations of chloroform were observed in Clarenville but in St. John's the concentrations werewithin Health Canada guidelines. The chloroform is a probablehuman carcinogen and is categorised as `B2' by U.S. EnvironmentalProtection Agency (U.S. EPA). The human health risk associatedwith consumption of drinking water was estimated by performingprobabilistic analysis. In the first phase bootstrap simulations(B = 250) were performed to calculate the variability in thedata. The normal distribution was found the best-fitted distribution to chloroform concentration data. For eachbootstrapped run 1000 Monte Carlo Simulations (MCS) wereperformed in the second phase. The cancer risk was estimatedusing dose-response relationship of chloroform. Appropriateprobability density functions (PDFs) were defined subjectivelyfor intake rate, body weight, exposure duration, exposurefrequency and averaging time. The excess lifetime human cancerrisk varied from 0.5 × 10-4 to 4.0 × 10-4, and zero to 1.0 × 10-4 for Clarenvilleand St. John's, respectively. The average cancer risks in Clarenville and St. John's communities were 1.2 × 10-4 and 2.5 × 10-5. The estimated probabilitiesof exceedences above 100 ppb (μg L-1), were 100 and 2.5% for Clarenville and St. John's, respectively which emphasised the need for water treatment. Granular Activated Carbon (GAC) was proposed as one of the potential treatment technology for risk reduction in St. John's community. The treatment efficiency of a proposed technology was assumed uniformly distributed and revised risks were calculated. Theaverage risk in St. John's can be reduced to 8.0 ×10-6 after treatment.  相似文献   

12.
粪大肠菌群(FecalColiform,FC)是判定污泥土地安全利用的重要指标之一。通过实地调查取样,收集了长江三角洲地区的南京、苏州、上海、杭州等15个城市的污水处理厂的48份污泥样品,测定了其粪大肠菌群数,旨在了解污泥中FC的数量与潜在污染风险;并在污泥自然风干过程的第7、14、21、28天分别取样测定了FC的数量和水分含量,以观察风干过程中FC和水分的动态变化及其与风干时间的关系。研究结果表明,污泥中FC的最大可能数(MPN)的范围在0～3.41×106(MPNg-1,DW),平均为3.79×105(MPNg-1,DW),检出率达89.6%。不同类型污泥中FC的数量差别较大,“河流”污水处理厂污泥和污泥制品的FC数量最低,以生活污水为主的污泥和混流污水污泥中FC数量较高。污泥风干过程中FC数量和水分含量均随风干时间的延长而减少,但FC数量有回升现象。总之,污泥样品的FC数量差异较大,部分污泥样品的数量超过了污泥农用的病原物标准,为了保护生态环境和人类健康,防止二次污染,污泥土地利用时需考虑FC数量,采取相应控制措施。  相似文献   

13.
恶臭假单胞菌P861(Gus)在油菜根部定殖的生态研究   总被引：3，自引：0，他引：3  
本研究采用Gus 基因标记技术和常规方法跟踪考察了恶臭假单胞菌P861(Gus) 在缩影系统油菜根圈的定殖情况,以及缩影系统内土壤类型、土壤含水量对根部定殖的影响。土壤含水量分别为60% FC和75% FC时,P861(Gus) 在砂姜黑土中的定殖水平高于50% FC的,不但能散布至种子下8cm 以内的根段部位,且定殖水平分别为7.5×102和2.8×103cfu·g-1。在灰潮土缩影中,P861(Gus) 在油菜根圈的定殖动态表现为在油菜播种后3 ～6 天,定殖密度可达最高水平(5.5×106cfu·g-1) ,然后急速下降,最后保持在一个相对稳定的较低水平(7.6×102cfu·g-1) 。P861(Gus) 在不同根段部位的定殖密度并无从上到下逐渐递减的规律。  相似文献   

14.
The present study demonstrates the usefulness of natural microbial growth-promoting compounds for improving the stability and life of vermicompost-based (both granular and its aqueous extract) bioformulations. Granular vermicompost maintained the number of cells of Rhizobium meliloti Rmd 201 up to 5.9 × 108 after 180 days at 28°C compared with 2.1 × 108 in charcoal (powdered), while aqueous extract of the vermicompost supported the 5.6 × 107 rhizobia numbers even after 270 days. The addition of 25 μL/mL cow urine and 0.01 mM calliterpinone, a natural plant growth promoter, increased the rhizobia number significantly in granular vermicompost and its aqueous extract, respectively.  相似文献   

15.
The efficiencies of free and immobilized bacterial cultures of petroleum hydrocarbon degraders were evaluated and compared in this study.Hydrocarbon-degrading microbial communities with high tolerance to and high degrading ability of crude oil were obtained from the soil contaminated with crude oil in the Yellow River Delta.Then,the microbial cells were immobilized in sodium alginate(SA)beads and sodium alginate-diatomite(SAD)beads.The biodegradation of crude oil in soil by immobilized cells was compared with that by free cells at three inoculation concentrations,1×104 colony forming units(cfu)kg-1(low concentration,L),5×104 cfu kg-1(medium concentration,M),and 1×105 cfu kg-1(high concentration,H).At 20 d after inoculation,the maximum degradation rate in the immobilized systems reached 29.8%(SAD-M),significantly higher(P<0.05)than that of the free cells(21.1%),and the SAD beads showed greater degradation than the SA beads.Moreover,both microbial populations and total microbial activity reached significantly higher level(P<0.05)in the immobilized systems than free cell systems at a same initial inoculation amount.The scanning effectronic microscope(SEM)images also confirmed the advantages of the immobilized microstructure of SAD beads.The enhanced degradation and bacterial growth in the SAD beads indicated the high potential of SAD beads as an effective option for bioremediation of crude oil-contaminated soils in the Yellow River Delta.  相似文献   

16.
The photo-Fenton oxidation treatment combined with a coagulation/flocculation process was investigated for removal of chemical oxygen demand (COD) from a refractory petroleum refinery wastewater. Scrap iron shavings were used as the catalyst source. A response surface methodology (RSM) with a cubic IV optimal design was employed for optimizing the treatment process. Kinetic studies showed that the proposed process could be described by a two-stage, second-order reaction model. Experiments showed that precipitation of iron ions can be utilized as a post-oxidation coagulation stage to improve the overall treatment efficiency. More than 96.9% of the COD removal was achieved under optimal conditions, with a post-oxidation coagulation stage accounting for about 30% of the removal, thus confirming the collaborative role of oxidation and coagulation in the overall treatment. A low-velocity gradient of 8.0 s?1 for a short mixing time of 10 min resulted in optimum post-oxidation coagulation. Comparison of photo-Fenton oxidation to a standard Fenton reaction in the same wastewater showed more rapid COD removal for photo-Fenton, with an initial second-order rate constant of 4.0 × 10?4 L mg?1 min?1 compared to the Fenton reaction’s overall second-order rate constant of 7.0 × 10?5 L mg?1 min?1.  相似文献   

17.
Soil-inhabiting fungal pathogen Fusarium oxysporum often causes severe yield losses in many crops. We investigated the effect of a plant growth-promoting fungus, Penicillium sp. EU0013 on Fusarium wilt disease. In dual culture experiments, EU0013 inhibited the growth of Fusarium wilt pathogens by producing an inhibition zone. In experiments using sterile potting medium under controlled conditions, EU0013 significantly reduced the severity of Fusarium wilt on tomato (Solanum lycopersicum L.) and cabbage (Brassica oleracea L. var. capitata). In non-sterile soil, benomyl-resistant mutants of EU0013 were selected by exposing the conidial solution of EU0013 to ultraviolet light. The selected mutant EU0013_90S isolate did not show any distinct differences from EU0013 in colony characteristics, growth rate or antifungal activity against Fusarium wilt pathogens in dual culture. The effect of EU0013_90S on tomato wilt was studied under greenhouse conditions using non-sterile soil. Two-weeks old tomato seedlings were dipped in four different concentrations of EU0013_90S conidial suspension (1?×?103, 1?×?104, 1?×?105, and 1?×?106 conidia mL–1). Seedlings were then planted in soil inoculated with either F. oxysporum f. sp. lycopersici race 1 CU1 or race 2 JCM 12575 (1?×?106 bud-cells g–1). We found the greatest disease suppression occurred when seedlings were dipped in the highest concentration of EU0013_90S conidia. This same inoculum concentration of EU0013_90S also resulted in the highest disease reduction in soil infested with JCM 12575. Higher root colonization with EU0013_90S showed a significant reduction in Fusarium wilt disease, suggesting that colonization by Penicillium sp. EU0013_90S is important for efficient biocontrol of these diseases.  相似文献   

18.
ABSTRACT

To ensure the safety of compost products, the Canadian Council of Ministers of the Environment's compost guidelines specify upper limits for certain pathogenic and indicator microbes, which are presumably achieved by exposing every particle of compost to temperatures ≥55°C for at least three consecutive days. A rugged temperature probe that behaves like a random compost particle was used to investigate whether every compost particle meets the time temperature criterion and to measure sanitation efficacy. An inoculum consisting of Salmonella enterica var. Meleagridis, Escherichia coli K12, and phi-S1 bacteriophage (all at levels of ～1 × 106 CFU/PFU mL?1) was added into 17 probes. The probes were randomly introduced into a covered, aerated static pile along with 17 probes that only monitored the temperature. After 56 days of composting, with one pile turn the probes were recovered. Organism levels were determined via culture-based methods. Before turning, 80% of the randomly introduced probes satisfied the time-temperature criterion. After turning, this number increased to 87%, demonstrating that turning is somewhat useful for sanitation. The cool zones largely remained mesophilic with the pile turning having minimal impact, which could potentially be an indication that the pile was not turned thoroughly. One of the 17 probes with cryovials reached only 40.2°C, and survival of S. meleagridis (2.5 × 106 CFU ml?1) was observed. The remaining probes with cryovials exceeded 55°C and were pathogen free. It appears that the specified time-temperature conditions are likely adequate. However, more observations are needed before a firm conclusion can be made.  相似文献   

19.
Hydraulic Resistance and Capacitance in the Soil-Plant System   总被引：1，自引：0，他引：1  
In this paper, the hydraulic resistances and capacitances were evaluated. based on the development of non-(?) model of water flow in the soil-plant system and the simulating experiment work.The results show that the mean hydraulic resistance in the soil-plant system is 6.79×109 MPa·S·m-3; the mean hydraulic capacitance in the system is 5.2×107m3·MPa-1. In the components of hydraulic capacitance in the system, the capacitance in soil (81.8×10-6m3·MPa ) is the biggest and its variability with suii water potential is extremely strong, the capacitance in plant (5.3×10-7m3·MPa-1) is much smaller than that in soil, and the capacitance in shoots (15.5×10-7m3·2MPa-1) is bigger than that in roots (8.4×10-7m3·2MPa-1). An interesting result is that the capacitance in plant is almost equivalent to that in the soil-plant system.  相似文献   

20.
ABSTRACT

Variations in the levels of the highly toxic oleandrin molecules were studied during composting of Nerium oleander L. waste mixed with clippings of the grass Pennisetum clandistenum L. The thermophilic phase is characterized by a rise in temperature, which reached 70°C. After 150 days of co-composting, the C/N ratio was 11, the pH was 8, the NO3?/NH4+ ratio was greater than 1 and overall decomposition reached 70%. During the successive stages of co-composting, oleandrin concentrations were monitored by HPLC. The relative abundance of oleadrin was 26.84% at T0 with 10% abatement during the first month and 90% after two months (stabilization phase), reaching 100%, i.e., total removal after 90 days of co-composting (maturation phase). The biodegradation of the toxic substance was largely attributed to the activity of actinomycetes and fungi. The germination index of lettuce and watercress seeds exceeded 50% after 90 days and reached 95% after 150 days, confirming that the final compost was mature, stable, and free from phytotoxicity in spite of the highly poisonous starting material.  相似文献   

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