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1.
Drainage water from agricultural fields with applied manure can degrade the bacterial quality of surface and groundwater. The impact of conventional tillage (CT) and zero tillage (ZT) practices on Escherichia coli (E.coli) discharge through artificially drained soils is not well understood. Consequently, two field trials were conducted during 2002–2004. The first trial involved fall applications of beef manure while the second involved spring applications of dairy manure. Both surface and subsurface drainage water were monitored in the first trial while only subsurface drainage water was monitored in the second. Under fall applied beef manure (trial 1), no differences (p?>?0.05) were observed in E.coli concentrations (cfu/100 ml) in combined drainage water under both tillage systems. However, during 2003–2004, subsurface drainage water under ZT had higher E.coli concentrations and loads than drainage water under CT. When the combined (surface + subsurface) annual E.coli loads were considered, CT loads were greater than ZT during 2002–2003 with an opposite situation during 2003–2004. Overall, annual E.coli loads were similar under ZT (4.7?×?1010 cfu/ha) and CT (4.8?×?1010 cfu/ha). Spring dairy manure application (trial 2) produced significant (p?>?0.03) tillage effect on E.coli loads in subsurface drainage water only during the second year. During the study period, ZT plots (1.55?×?1010 cfu/ha) discharged 5× more E.coli than CT (0.23?×?1010 cfu/ha). A longer duration of ZT practices resulted in higher subsurface flow volumes and subsequently greater loads of E.coli discharge in both trials.  相似文献   

2.
Two bacteriophages — phage 80 of Staphylococcus aureus and a P2-like phage (?MWD 1) of Escherichia coli (H2S + ) — were evaluated as sewage tracers. Background plaque concentrations on the S. aureus host were < 1100 mL?1 in seven (raw and treated) effluents tested but, on E. coli (H2S +), they ranged from < 1100 mL?1 in oxidation pond effluents to 1.1 × 103 100 mL?1 in primary treated meatworks effluent. Thus, phage 80 appears to be a suitable tracer for both raw and treated sewage but ?MWD 1 may only be suitable for use in secondary treated effluent. In frozen samples, concentrations of both tracer phages were reduced by 90% within 2 days, but decreased more slowly over the following 68 days to around 5% of the original (unfrozen) titre. In a field test, the two phages were used simultaneously to trace the movement of oxidation pond effluents down a river system. Timing of assay of frozen samples and the advantages and limitations of bacteriophages as sewage tracers are discussed.  相似文献   

3.
Abstract. This article examines some of the factors that influence the relative risk of Escherichia coli pollution of surface waters from grazing animals compared to cattle slurry application. Drainage water from pipe‐drained plots grazed with sheep (16 sheep + lambs per hectare) from 29 May to 17 July 2002 had average E. coli counts of 11 c.f.u. mL?1 or 0.4% of estimated E. coli inputs over the grazing period. Drainage water from plots on the same site treated with cattle slurry (36 m3ha?1 on 29 May 2002) had lower average E. coli counts of 5 c.f.u. mL?1 or 0.03% of estimated faecal input. Sheep (16 lambs per hectare) grazing under cooler, moister conditions from 24 September to 3 December 2001 gave drainage water with much higher average E. coli counts of 282 c.f.u. mL?1 or 8.2% of estimated input, which is more than twice the average E. coli counts previously reported under such conditions (Vinten et al. 2002 Soil Use and Management 18, 1–9). Laboratory studies of runoff from soil slabs after slurry application showed that the mobility of E. coli in surface soil decreased with time, suggesting that increased attachment to soil or migration to ‘immobile’ water also provides at least part of the physical explanation for the relatively higher risk of pollution from grazing animals compared with slurry. Sampling for E. coli in field drainflow and in streamwater during a storm event in the predominantly dairy Cessnock Water catchment, Ayrshire, Scotland supported the hypothesis that E. coli transport is linked to grazing animals. For a 7‐mm rainfall event, roughly 14% of the estimated daily input from grazing livestock was transported to the river, even though little slurry spreading had occurred in the catchment in the previous month. Spot sampling of field drains in grazed fields and silage fields in the same catchment also showed that grazing animals were the principal source of E. coli and faecal streptococci.  相似文献   

4.
The research goal was to determine if onsite wastewater system (OWS) density had an influence on the concentrations and watershed exports of Escherichia coli and enterococci in urbanizing watersheds. Eight watersheds with OWS densities ranging from <?0.1 to 1.88 systems ha?1 plus a watershed served by sewer (Sewer) and a mostly forested, natural watershed (Natural) in the Piedmont of North Carolina served as the study locations. Stream samples were collected approximately monthly during baseflow conditions between January 2015 and December 2016 (n?=?21). Median concentrations of E. coli (2014 most probable number (MPN) 100 mL?1) and enterococci (168 MPN 100 mL?1) were elevated in streams draining watersheds with a high density of OWS (>?0.77 system ha?1) relative to watersheds with a low (<?0.77 system ha?1) density (E. coli: 204 MPN 100 mL?1 and enterococci: 88 MPN 100 mL?1) and control watersheds (Natural: E. coli: 355 MPN 100 mL?1 and enterococci: 62 MPN 100 mL?1; Sewer: 177 MPN 100 mL?1 and 130 MPN 100 mL?1). Samples collected from watersheds with a high density of OWS had E. coli and enterococci concentrations that exceeded recommended thresholds 88 and 57% of times sampled, respectively. Results show that stream E. coli and enterococci concentrations and exports are influenced by the density of OWS in urbanizing watersheds. Cost share programs to help finance OWS repairs and maintenance are suggested to help improve water quality in watersheds with OWS.  相似文献   

5.
The survival, persistence, and dispersal of bacteria in soil raises serious water quality questions for rural areas of the world especially where podzol-type soils dominate. To determine survival characteristics of an environmentally derived multiple-antibiotic resistant E. coli, it was added to laboratory containers containing sandy-loam podzol soils taken from two different locations (‘Webb’, pH 6.8–8.3 and ‘Rich’, pH 5.5–7.2). This was done in order to study the stability of the tracer bacterium under conditions designed to mimic those that might be encountered during subsequent field mini-plot studies. Sets of microcosms consisting of three replicates of each soil received 1012 or 1013 colony forming units per g of soil and were incubated at four temperatures (5, 10, 20, and 37 °C) and two moisture levels (15% i.e. average field capacity and saturation) for 160 days. The microcosm data gave estimated maximum survical times for the ‘Webb’ soil of 23.3 months at 5 °C under saturating moisture conditions and 20.7 months for the ‘Rich’ soil under the same conditions using exponential regression analysis of the data.  相似文献   

6.
Land applications of manure from confined animal systems and direct deposit by grazing animals are both major sources of bacteria in streams. An understanding of the overland transport mechanisms from land applied waste is needed to improve design of best management practices (BMPs) and modeling of nonpoint source (NPS) pollution. Plots were established on pasturelands receiving phosphorus-based livestock waste applications to measure the concentrations of Escherichia coli (E. coli), fecal coliform (FC), and Enterococcus present in overland flow at the edge of the field. The flow-weighted bacteria concentrations were highest in runoff samples from the plots treated with cowpies (1.37×105 colony forming units (cfu)/100 ml of E. coli) followed by liquid dairy manure (1.84×104 cfu/100 ml of E. coli) and turkey litter (1.29×104 cfu/100 ml of E. coli). The temporal distribution of fecal bacterial concentrations appeared to be dependent upon both the animal waste treatment and the indicator species, with peak concentrations occurring either at the beginning of the runoff event or during peak flow rates. BMPs could be selected to reduce peak flows or first flush effects depending upon the litter or manure applied to the land. The commercial Biolog System was used to identify the dominant species of Enterococcus present in the cowpie source manure (Enterococcus mundtii 55%) and in the runoff collected from the transport plots treated with cowpies (Enterococcus faecalis 37%). The identification of predominant species of Enterococcus that are associated with specific sources of fecal pollution could greatly assist with identifying the origins of NPS pollution.  相似文献   

7.
Experimental plots set up by G. W. Dimbleby to test the effect of birch on the soil of a podzolized heather moor were sampled for earthworms after 8, 10 and 27 yr. Of 213 worms collected, one was Dendrobaena octaedra (Savigny, 1826) and the remainder were Bimastos eiseni (Levinsen, 1884). No worms were found on the heather control plots and a single specimen only was taken on plots screefed and sown with Molinia. The population density on plots treated with birch litter, taking 1 yr with another, averaged approximately 1.7 worms m?2 with a biomass < 1 g m?2.On the Callunetum surrounding the experimental plots worms were sampled by a trapping method. Only B. eiseni was found. On the Callunetum and on the experimental plots worm numbers were correlated with the calcium content of the 0–3 cm soil horizon. Parts of the experimental site and surrounding Callunetum are subject to intermittent waterlogging. The development of the earthworm population in these areas appears to be restricted by occasional reducing conditions in the upper organic horizon.  相似文献   

8.
From the results of in vitro studies carried out on wastewater from a stabilization pond it can be concluded that pH values close to 9, as a single factor, do not play any essential role in the die-off of fecal coliform bacteria. The percentage of elmination that occurs in pond water inoculated with 1.1×1010 cells of E. coli mL?1 where the pH is maintained at 8.2 (original pH) is 99.997%, a much greater reduction than that observed (94.1%) in distilled water inoculated with the same concentration of E. coli and where pH is increased up to 9.  相似文献   

9.
Chromium occurs naturally at trace levels in most soils and water, but disposal of industrial waste and sewage sludge containing chromium compounds has created a number of contaminated sites, which could pose a major environmental threat. This study was conducted to enumerate and isolate chromium-resistant microorganisms from sediments of evaporation ponds of a metal processing plant and determine their tolerance to other metals, metalloids and antibiotics. Enumeration of the microbiota of Cr-contaminated sediments and a clean background sample was conducted by means of the dilution-plate count method using media spiked with Cr(VI) at concentrations ranging from 10 to 1000 mg L?1. Twenty Cr(VI) tolerant bacterial isolates were selected and their resistance to other metals and metalloids, and to antibiotics was assessed using a plate diffusion technique. The number of colony-forming units (cfu) of the contaminated sediments declined with increasing concentrations from 10 to 100 mg L?1 Cr(VI), and more severely from 100 to 1000 mg L?1 Cr(VI). The background sample behaved similarly to 100 mg L?1 Cr(VI), but the cfu declined more rapidly thereafter, and no cfu were observed at 1000 mg L?1 Cr(VI). Metals and metalloids that inhibited growth (from the most to least inhibitory) were: Hg > Cd > Ag > Mo = As(III) at 50 μg mL?1. All 20 isolates were resistant to Co, Cu, Fe, Ni, Se(IV), Se(VI), Zn, Sn, As(V), Te and Sb at 50 μg mL?1 and Pb at 100 μg mL?1. Eighty-five percent of the isolates had multiple antibiotic resistance. In general, the more metal-tolerant bacteria were among the more resistant to antibiotics. It appears that the Cr-contaminated sediments may have enriched for bacterial strains with increased Cr(VI) tolerance.  相似文献   

10.
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   

11.
Abstract

Azotobacter chroococcum strains E12, HT57 were genetically tagged with lac Z, gfp to study the colonization behaviour on wheat (Triticum aestivum) and cotton (Gossypium sp.) in soil under controlled conditions. 103 – 104 cfu g?1 soil of HT57 lac Z were found to colonize roots of both cotton and wheat crops whereas 1.7 × 104 – 7.2 × 104 cfu g?1 soil of E12 gfp was colonizing wheat roots and 1.6 × 104 – 9.3 × 104 cfu g?1 soil of E12 gfp colonized cotton roots respectively. Tagged strains colonized mostly on root tips compared to basal roots in both the crops.  相似文献   

12.
One way to disperse waste from large commercial feedlots is to spread large amounts of the waste on limited areas nearby. The effects of this practice on the soil microbial populations was assessed. Feedlot waste (FLW) was applied for 5 yr at rates of 0, 22, 67, 134, and 269 t ha?1 yr?1. Additional treatments were 538 t ha?1 yr?1 for 1 and 3 years and applications of N and NPK fertilizer. Soil cores from plots were sampled for microbial analysis before, during, and after the fifth growing season. April, July. and December soil samples were analyzed to 180-, 20-, and 480-cm depths, respectively. The following utritional and physiological groups of microorganisms were counted: soil fungi on Rose Bengal agar; bacteria on a basal mineral salts medium, on nutrient agar (both aerobically and in BBL GasPak jars), and on EMB agar (Escherichia coli-type colonies and total counts); and nitrifying and denitrifying organisms. Little effect due to FLW application rates was found, and organisms producing coliform-type colonies on EMB agar did not persist in the soil. The results indicated that applying large amounts of feedlot waste will not deleteriously affect soil microorganisms.  相似文献   

13.
Outwintering beef cattle on woodchip corrals offers stock management, economic and welfare benefits when compared with overwintering in open fields or indoors. A trial was set up on a loamy sand over sand soil to evaluate the pollution risks from corrals and the effect of design features (size and depth of woodchips, stocking density, and feeding on or off the corral). Plastic‐lined drainage trenches at 9–10 m spacing under the woodchips allowed sampling of the leachate. Sampling of the soil to 3.6 m below the corral allowed evaluation of pollutant mitigation during vadose zone transport. Mean corral leachate pollutant concentrations were 443–1056 mg NH4‐N L?1, 372–1078 mg dissolved organic carbon (DOC) L?1, 3–13 mg NO3‐N L?1, 8 × 104–1.0 × 106Escherichia coli 100 mL?1 and 2.8 × 102–1.4 × 103 faecal enterococci 100 mL?1. Little influence of design features could be observed. DOC, NH4 and (in most cases) E. coli and faecal enterococci concentrations decreased 102–103 fold when compared with corral leachate during transport to 3.6 m but there were some cores where faecal enterococci concentrations remained high throughout the profile. Travel times of pollutants (39–113 days) were estimated assuming vertical percolation, piston displacement at field moisture content and no adsorption. This allowed decay/die‐off kinetics in the soil to be estimated (0.009–0.044 day?1 for DOC, 0.014–0.045 day?1 for E. coli and 0–0.022 day?1 for faecal enterococci). The mean [NO3‐N] in pore water from the soil cores (n = 3 per corral) ranged from 114 ± 52 to 404 ± 54 mg NO3‐N L?1, when compared with 59 ± 15 mg NO3‐N L?1 from a field overwintering area and 47 ± 40 mg NO3‐N L?1 under a permanent feeding area. However, modelling suggested that denitrification losses in the soil profile increased with stocking density so nitrate leaching losses per animal may be smaller under corrals than for other overwintering methods. Nitrous oxide, carbon dioxide and methane fluxes (measured on one occasion from one corral) were 5–110 g N ha?1 day?1, 3–23 kg C ha?1 day?1, and 5–340 g C ha?1 day?1 respectively. Ammonia content of air extracted from above the woodchips was 0.7–3.5 mg NH4‐N m?3.  相似文献   

14.
The side effects of fluazifop-butyl on soil fungal populations and oxygen uptake were studied by incubating soil samples with a range of fluazifop-butyl concentrations (0, 0.6, 3 and 6 μg g?1) over 8 weeks. Cellulose decomposition in soil was also studied in laboratory experiments with the herbicide which was either incorporated in soil or sprayed onto calico squares which were buried in soil. The mycelial dry weight of six fungal species under the effect of the herbicide was also examined. Fluazifop-butyl had no significant effect on total fungal propagule populations at 0.6 μg g?1. At 3 and 6 μg g?1, it caused temporary reduction in fungal populations observed after 1 and 2-wk of incubation. The herbicide had no significant effect on OZ uptake. The decay of calico buried in herbicide-treated soil was generally stimulated, while the decomposition of herbicide-treated calico, buried in untreated soil, was temporary delayed. The mycelial dry weight yields of Aspergillus favus (at 2 and 12 μg mL?1 of fluazifop-butyl) and Cunninghamella echinulata (at 12 μg mL?1) were significantly increased. At 24 μg mL?1 the mycelial dry weight of A. flavus and Alternaria alternata was significantly reduced.  相似文献   

15.
Little is known about the transport of microorganisms through freeze-fractured clay soils. Normally consolidated clay (NCC) and compacted clay (CC) columns (representing a natural clay barrier and a compacted barrier, respectively) were exposed to six consecutive freeze–thaw cycles and permeated for 21 days with an Escherichia coli cell suspension (approximately 1?×?107 colony forming units (CFU)/mL) containing a 2.1-mM bromide tracer. An unfractured sand column was also examined for comparison with the clay columns. While no E. coli was detected in the effluent of both untreated NCC and CC control clay columns, a relatively low density of E. coli (between 228 and 270 CFU/mL compared to 1?×?107 CFU/mL in the influent) was first detected in the effluent of the freeze-fractured NCC and CC columns at 0.29 and 0.31 pore volumes (or at 5.4 and 4.1 h), respectively. It took 11 min for a full breakthrough of E. coli through the sand column, but only about 0.1% of the influent E. coli density was detected in the effluents of the freeze-fractured NCC and CC columns at day 21. These observations show that despite the high bacterial retention capacity of the freeze-fractured clay columns, the fractures were large enough for the E. coli to flow through. Based on batch sorption tests and the permeation data, it is estimated that 18%, 7%, and 84% of the freeze-fractured NCC, CC, and sand columns would be exposed to the influent, respectively, under a full E. coli breakthrough condition. Our data show that the high bacterial retention capacity of clay barriers can be compromised by freeze–thaw conditions.  相似文献   

16.
The concentration of mercury has been determined in assimilation organs of forest trees from 10 main industrial regions of Slovakia, four mountain forests and one military area and compared with concentration of mercury from 1356 permanent monitoring plots of Slovakia. The mercury concentration ranges for 2 yr old needles of Picea abies Karst. were (in mg kg?1): 1.249–4.402 (Rudnany iron ore mines), 0.013–0.749 (nine other industrial regions), 0.021–0.737 (four mountain forests) and 0.053–0.538 (military area). The mercury content in the soil (0–5 cm) from a mercury smelting plant ranged from 9.9 to 130 mg kg?1, and the moss Pleurozium schreberi contained 3.8–9.1 mg kg?1. The values obtained were compared with the available literature data.  相似文献   

17.
Three isolates of Escherichia coli were labeled by their resistance to sodium azide and, separately, to novobiocin, nalidixic acid, and tetracycline. The strains exhibited a high degree of persistence in the soil environment and were recoverable on strain specific media at levels within the 95% confidence interval of the numbers covered on nonselective media. The E. coli strains were subsequently used to evaluate the events which would occur when a septic tank drainfield became submerged in a perched water table and effluentborne bacteria escaped into the groundwater. Field experiments were conducted by introducing the strains into horizontal lines installed into the A, B, and C horizons of a soil profile and transport was evaluated by collecting groundwater samples from 5 rows of piezometers (sampling six separate depth zones/row) located downslope from the injection lines. The major portion of subsurface transport of the bacterial populations occurred in specific zones in the soil profile and at an apparent maximum velocity of 17.0 cm min?1. The maximum bacterial density in the groundwater, observed at each sampling distance downslope, was used to produce a mathematical relationship which described the overall decrease in numbers of organisms with increased distance through the soil. The potential health hazards which could occur by the subsurface transport of fecal organisms in relation to these experiments are discussed.  相似文献   

18.
Ninety percent of the pines (P. Sylvestris) in the forests of Berlin (West) are classified as damaged. Needle and leaf analyses do not indicate nutrient deficiencies. In site of high S-inputs (55 kg ha?1 yr?1 with throughfall) total acid inputs are moderate (2.4 kmol ha?1 yr?1) due to their neutralization by carbonatic dusts. Heavy metal depositions have led to accumulations in the forest floor (e.g. Pb 150 mg kg?1, Cd 0.5 mg kg?1). The dominating soil type, a cambic arenosol (Ustipsamment) is strongly acidified (pH 3.2 – 4.0) and poor in available nutrients. On an experimental plot, the application of dolomitic lime (6.1 tons ha?1) and fertilizer (145 kg ha?1 K2SO4) led to a significant increase m pH and base saturation in the top 10 cm of the mineral soil after 2 yr. The data on element fluxes give evidence for increased mineralization rates, enhanced heavy metal accumulation in the forest floor and increased soil solution concentrations of potentially hazardous substances (Al, Cd, NO3). The lime application is discussed in terms of site specific effects on ecosystem stability and groundwater quality.  相似文献   

19.
A chromated-copper-arsenate (CCA) wood preservative was tested for toxic effects on the growth of a bacterial culture (Flavobactenum sp. ATCC 53874) capable of biodegrading pentachlorophenol, another wood preservation chemical. Both a commercially available CCA preparation and a laboratory-prepared CCA solution were tested. Each had an inhibitory effect on the growth of Flavobacterium at diluted CCA levels as low as 1.0×10?4 to 1.0×10?5% wt vol?1. The commercial formulation was generally more toxic. EC50 values calculated after 96 hr of incubation were 1.2 ×10?4% wt vol?1 for the commercial material (containing 0.15/0.097/0.14 μg mL?1 of Cr/Cu/As, respectively) and 3.8×10?4% for the laboratory solution (containing 0.51/0.31/0.49 μg mL?1 of Cr/Cu/As, respectively). CCA toxicity increased during the first 7 to 8 days and then slowly decreased for the balance of the 21 day incubation period. Biodegradation of pentachlorophenol residues in contaminated soil will be negatively affected by the presence of CCA as a co-contaminant.  相似文献   

20.
Phytoremediation is a remediation technique that involves the use of plants to extract, sequester, and/or detoxify pollutants through physical, chemical, and biological processes. The use of phytoremediation is expanding due to its cost-effectiveness compared with conventional methods. This study was conducted to investigate the effects of autumn and spring application of plant growth-promoting rhizobacteria (PGPR, 108 cfu mL?1 Bacillus megaterium var. phosphaticum sprayed at 250 mL plot?1) and phosphorus (P) fertilizer (0, 11, 22, 33, 44 kg P ha?1) on dry matter yield and heavy metal uptake by plants in soils contaminated with heavy metals. Field experiments were conducted using a randomized complete block design with four replications between 2004 and 2007. The results of the study indicated that P fertilization, but not PGPR application, significantly affected dry matter yield. Application of PGPR increased heavy metal availability in soils and the heavy metal uptake of meadow plants. The heavy metal content of the meadow plants resulting from PGPR application was 4–6 times higher for the spring application than the autumn application. Approximately 16, 30, 10, 10, and 3 growing seasons without PGPR are necessary to remove all lead (Pb), nickel (Ni), boron (B), manganese (Mn), and zinc (Zn), respectively, from polluted soil. The time required for Pb, Ni, B, Mn, and Zn removal could be further decreased to approximately 4, 6, 3, 3, and 1 growing seasons, respectively, with 33 kg phosphorus pentoxide (P2O5) ha?1 and 108 cfu mL?1 PGPR applications at rates of 250 mL plot?1 in the spring season.  相似文献   

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