Fate of Escherichia coli and Escherichia coli O157 in soils and drainage water following cattle slurry application at 3 sites in southern Scotland

Abstract. Slurry from farm animals may contaminate water supplies, rivers and bathing waters with faecal coliforms, such as Escherichia coli . Where animals harbour the O157 strain the hazard to human health is particularly high, but both the hazard level, and the low incidence and sporadic nature of the excretion of E. coli O157 make it difficult to study this strain under field conditions. The survival of total E. coli and of E. coli O157 were compared in the laboratory for two soils under controlled temperature and moisture. E. coli O157 die-off rate was the same as or quicker than for total E. coli . This result meant that field experiments studying the fate of total E. coli should give a satisfactory evaluation of the risk of water contamination by the O157 strain. In four field experiments at three sites, slurry containing total E. coli numbers of 2.2 × 10⁴ to 5.7 × 10⁵ colony forming units per mL (c.f.u. mL^–1) was applied to drained field plots. Field die-off was faster than expected from laboratory experiments, especially in one experiment where two weeks dry weather followed application. In all but this experiment, the first drain flow events after slurry application led to very high E. coli concentrations in the drains (10³ to 10⁴ c.f.u. mL^–1). E. coli O157 was present in the slurry used for two of the experiments (33 c.f.u. per 100 mL in each case). However the proportion of E.coli O157 was very low (about 1 in 10⁵) and it was not detected in the drainage water. After the first week E. coli drainage water numbers decreased rapidly but they were 1–10 c.f.u. mL^–1 for much of the sampling period after slurry application (1–3 months).     

不同施肥处理下旱地红壤中阿特拉津的环境归趋及其调控研究

本研究采集长期施用化肥或有机肥(猪粪)的旱地红壤,设置单一或复合添加木质素和牡蛎壳粉的不同组合处理,进行微宇宙试验。采用同位素示踪、定量PCR、高通量测序等方法,研究施肥及土壤改良措施对红壤中阿特拉津矿化特征及降解微生物的调控作用。结果表明,在14周培养期间,旱地红壤对阿特拉津的矿化率低于0.33%。牡蛎壳粉有效提高红壤p H、改变土壤细菌群落,将施化肥、有机肥土壤中矿化率大幅提高至43.3%和9.51%,同时导致atz C和trz N等阿特拉津降解功能基因的富集。木质素则显著促进阿特拉津残留态形成,使阿特拉津与土壤有机质的结合达对照组的6.1倍,但对污染物的矿化没有明显作用。本研究结果有助于阐明旱地红壤中阿特拉津的环境归趋,并为发展适用于红壤的污染物控制技术提供科学依据。     

The Transport of Escherichia coli Through Freeze-Fractured Clay Soil

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.     

Soil particles inhibit colony formation of Escherichia coli on the surface of agar media

When enumerating Escherichia coli in serial dilution of soil using selective media, soils was found to exert an inhibitory effect on colony formation on the surface of the agar plates. The inhibitory effect did not appear to be due to either soil bacteria or soluble chemicals but to the soil particles themselves. No inhibition was observed when the cells were enumerated by the most probable number (MPN) method. Some alternative plating methods, such as pour-plating or overlaying, were effective in removing the inhibitory effect. Removal of soil particles by simple sedimentation was also effective in enhancing the enumeration efficiency. These observations would be practically important for enumerating bacteria in the soil environment.     

啶氧菌酯环境归趋与生态风险研究进展

啶氧菌酯是一种对生态系统存在安全风险的甲氧基丙烯酸酯类杀菌剂,从环境归趋,生态毒理的角度出发,综述了啶氧菌酯在土壤、水中、农作物中的归趋,阐述了啶氧菌酯对蚯蚓、蜜蜂和水生非靶标生物急/慢性毒性,和对组织、酶活、蛋白、基因等方面的影响进行了归纳,并讨论了啶氧菌酯未来的生态毒理学研究方向。以期为进一步研究啶氧菌酯对非靶标生物毒性效应和作用机理,并制定相关策略以减少其生态风险提供依据。     

Fate of chlorate present in cattle wastes and its impact on Salmonella Typhimurium and Escherichia coli O157:H7

Chlorate salts are being developed as a feed additive to reduce the numbers of pathogens in feedlot cattle. A series of studies was conducted to determine whether chlorate, at concentrations expected to be excreted in urine of dosed cattle, would also reduce the populations of pathogens in cattle wastes (a mixture of urine and feces) and to determine the fate of chlorate in cattle wastes. Chlorate salts present in a urine-manure-soil mixture at 0, 17, 33, and 67 ppm had no significant effect on the rates of Escherichia coli O157:H7 or Salmonella Typhimurium inactivation from batch cultures. Chlorate was rapidly degraded when incubated at 20 and 30 degrees C with half-lives of 0.1 to 4 days. Chlorate degradation in batch cultures was slowest at 5 degrees C with half-lives of 2.9 to 30 days. The half-life of 100 ppm chlorate in an artificial lagoon system charged with slurry from a feedlot lagoon was 88 h. From an environmental standpoint, chlorate use in feedlot cattle would likely have minimal impacts because any chlorate that escaped degradation on the feedlot floor would be degraded in lagoon systems. Collectively, these results suggest that chlorate administered to cattle and excreted in wastes would have no significant secondary effects on pathogens present in mixed wastes on pen floors. Lack of chlorate efficacy was likely due to low chlorate concentrations in mixed wastes relative to chlorate levels shown to be active in live animals, and the rapid degradation of chlorate to chloride at temperatures of 20 degrees C and above.     

Effects of Grasses on the Fate of VOCs in Contaminated Soil and Air

Plant toxicity and chemical removal tests were conducted to investigate the remediation ability of grasses with respect to volatile organic contaminants (VOCs) in contaminated soil and air. Eastern gamagrass (Tripsacum dactyloides) and annual ryegrass (Lolium rigidum) were exposed to artificially contaminated soil or air containing a mixture of 1,1,1-trichloroethane (TCA), trichloroethylene (TCE), and tetrachloroethylene (PCE) under controlled laboratory conditions. The results showed that the grasses are more severely affected in hydroponics than potted soil contaminated with a mixture of these contaminants. It was observed from the results that more contaminants were detected in the shoot and root of plants grown in a closed system with contaminated air than in an open system with contaminated soil. It is suggested from the results that grasses can be used for purification of VOCs from contaminated air especially in a closed system, but the purification effects are likely to be low. The results also suggested that the concentration level of VOCs in shoot, root, and soil could be used as contamination indicator at contaminated sites.     

Occurrence and Environmental Fate of Veterinary Antibiotics in the Terrestrial Environment

A wide variety of veterinary antibiotics (VAs) has been detected in environmental water samples, and this is of potential environmental concern due to their adverse effects. In particular, the potential for development of antibiotic-resistant bacteria has raised social concerns leading to intensive investigation regarding the influence of antibiotics on human and ecosystem health. One of the main sources of antibiotic effluence to the environment is livestock manures that often contain elevated levels of VAs that survive normal digestive procedures following medication in animal husbandry because unlike human waste, waste generated on farms does not undergo tertiary wastewater treatment, and consequently, the concentration of antibiotics entering the environment is expected to be larger from farming practices. Animal feed is often supplemented with VAs to promote growth and parasite resistance in the medicated animals, and this practice typically resulted in higher use of VAs and consequential excretion from livestock through urine and feces. The excretion rate varied depending on the type of VA used with around 75, 90, and 50?C100% being excreted for chlortetracycline, sulfamethazine, and tyolsin, respectively. The excreted VAs that initially present in livestock manures were degraded more than 90% when proper composting practice was used, and hence, this can be employed as a management strategy to decrease VA environmental loads. The reduction of VA concentrations during composting was mainly attributed to abiotic processes rather than biotic degradation. The VAs released to soils by the application of manure and manure-based composts can be degraded or inactivated to various degrees through abiotic process such as adsorption to soil components. Depending on the antibiotic species and soil properties, residues can be transferred to groundwater and surface water through leaching and runoff and can potentially be taken up by plants.     

Soil Moisture Controls the Denitrification Loss of Urea Nitrogen from Silty Clay Soil

Relative control of soil moisture [30, 60, and 80 percent water-holding capacity (WHC)] on nitrous oxide (N₂O) emissions from Fargo-Ryan soil, treated with urea at 0, 150, and 250 kg N ha^?1 with and without nitrapyrin [2-chloro-(6-trichloromethyl) pyridine] (NP), was measured under laboratory condition for 140 days. Soil N₂O emissions significantly increased with increasing nitrogen (N) rates and WHC levels. Urea applied at 250 kg N ha^?1 produced the greatest cumulative N₂O emissions and averaged 560, 3919, and 15894 µg kg^?1 at 30, 60, and 80 percent WHC, respectively. At WHC ≤ 60 percent, addition of NP to urea significantly reduced N₂O losses by 2.6- to 4.8-fold. Additions of NP to urea reduced N₂O emission at rates similar to the control (0 N) until 48 days for 30 percent WHC and 35 days for 60 and 80 percent WHC. These results can help devise urea-N fertilizer management strategies in reducing N₂O emissions from silty-clay soils.     

Modelling the Fate of Chromated Copper Arsenate in a sandy Soil

A pulse of chromated copper arsenate (CCA, a timber preservative) was applied in irrigation water to an undisturbed field soil in a laboratory column. Concentrations of various elements in the leachate from the column were measured during the experiment. Also, the remnants within the soil were measured at the end of the experiment. The geochemical modelling package, PHREEQC-2, was used to simulate the experimental data. Processes included in the CCA transport modelling were advection, dispersion, non-specific adsorption (cation exchange) and specific adsorption by clay minerals and organic matter, as well as other possible chemical reactions such as precipitation/dissolution. The modelling effort highlighted the possible complexities in CCA transport and reaction experiments. For example, the uneven dosing of CCA as well as incomplete knowledge of the soil properties resulted in simulations that gave only partial, although reasonable, agreement with the experimental data. Both the experimental data and simulations show that As and Cu are strongly adsorbed and therefore, will mostly remain at the top of the soil profile, with a small proportion appearing in leachate. On the other hand, Cr is more mobile and thus it is present in the soil column leachate. Further simulations show that both the quantity of CCA added to the soil and the pH of the irrigation water will influence CCA transport. Simulations suggest that application of larger doses of CCA to the soil will result in higher leachate concentrations, especially for Cu and As. Irrigation water with a lower pH will dramatically increase leaching of Cu. These results indicate that acidic rainfall or significant accidental spillage of CCA will increase the risk of groundwater pollution.     

Modelling the Fate of Chromated Copper Arsenate in a sandy Soil

Afforestation of former agricultural land changes soil characteristics such as pH and organic matter content, which may affect heavy metal solubility in the soil. In this study the effects of different tree species on heavy metal solubility were investigated at four 34 years old adjacent stands of beech (Fagus sylvatica L.), grand fir (Abies grandis Lindl.), Norway spruce (Picea abies (L.) Karst.) and oak (Quercus robur L.) planted on former agricultural land at four different sites in Denmark. The sites differ in soil characteristics and represent two texture classes (loamy sand and sandy loam). Soil pH and soil organic matter content was measured in the 16 stands and soil solution was isolated by centrifugation from three depths at four different occasions. Dissolved organic carbon (DOC), pH in the soil solution and the soil solution concentrations (availability) of Cd, Cu, Ni, Pb and Zn were determined. Analysis of variance showed that the tree species affects soil pH and organic matter content in the topsoil, but not in the lower horizons. Norway spruce and grand fir acidify more than beech and oak, and the highest amount of accumulated soil organic matter is in the topsoil under Norway spruce. The effects of tree species on soil solution pH and DOC resemble the effect on soil pH and organic matter content. Grand fir enhances the solubility of Cd and Zn in the topsoil with the lower solubility found under beech and oak and Norway spruce enhances the solubility of Cu, Ni and Pb in the top horizons. The lowest solubility of Ni and Pb is found under beech and oak, whereas the lowest Cu concentrations in the soil solution are found under grand fir. After 34 years of afforestation no effects of tree species on the concentrations of heavy metals in the soil solution from the C-horizons were found. The tree species effect on the concentration of Cd, Cu and Ni in the soil solution depends on the soil characteristics with the higher concentrations found in sandy loam soils, whereas no effect of site on the solution concentration was found for Pb and Zn. It was not possible to find a clear correlation between the soil solution concentrations of heavy metals, pH and DOC concentration.     

土壤有机和无机组分对多环芳烃环境行为影响的研究进展

土壤中多环芳烃(PAHs)的环境行为取决于它们与土壤不同组分之间的相互作用。本文综述了土壤有机质、黏土矿物以及有机矿质复合体对PAHs土壤环境行为影响的研究进展,期望从土壤基本组成和性质上对PAHs的土壤环境行为有一个本质的了解。     

Preferential Attachment of Escherichia coli to Different Particle Size Fractions of an Agricultural Grassland Soil

This study reports on the attachment preference of a faecally derived bacterium, Escherichia coli, to soil particles of defined size fractions. In a batch sorption experiment using a clay loam soil it was found that 35% of introduced E. coli cells were associated with soil particulates >2 μm diameter. Of this 35%, most of the E. coli (14%) were found to be associated with the size fraction 15–4 μm. This was attributed to the larger number of particles within this size range and its consequently greater surface area available for attachment. When results were normalised with respect to estimates of the surface area available for bacterial cell attachment to each size fraction, it was found that E. coli preferentially attached to those soil particles within the size range 30–16 μm. For soil particles >2 μm, E. coli showed at least 3.9 times more preference to associate with the 30–16 μm than any other fraction. We report that E. coli can associate with different soil particle size fractions in varying proportions and that this is likely to impact on the hydrological transfer of cells through soil and have clear implications for our wider understanding of the attachment dynamics of faecally derived bacteria in soils of different compositions.     

施用涂层尿素对水田土壤氮去向及其利用率的影响

采用水稻盆栽试验方法,研究施用涂层尿素对水田土壤氮的挥发、土壤残留、水稻吸收三个去向及其氮素利用率的影响。研究结果表明:施用涂层尿素可显著抑制NH3和NOX挥发损失,NH3和NOX挥发量之和的减少幅度为22.1%~24.8%;使土壤中全氮含量增加,增加幅度为1.9%~2.1%。等氮用量条件下,施用涂层尿素可极显著提高氮素利用率,其提高幅度随施用量增大而减小;使水稻经济产量显著增加,中用量和高用量水平处理经济产量增加幅度分别为21.8%和21.5%。说明施用涂层尿素不仅能提高水田土壤氮素利用率,而且可减轻生态环境污染。     

硒的土壤环境化学研究进展

本文概述了土壤环境中硒的赋存形态和生物有效性 ,阐述了影响环境中硒的形态、有效性和转化的因素 .并对今后硒的土壤环境化学研究应关注的问题提出了建议     

Fate of Fertilizer Nitrogen Applied to Crops Grown on Fluvo-Aquic Soil in Huang-Huai-Hai Plain

The fate of urea-and ammonium bicarbonate(ABC)-nitrogen (N) applied by prevailing traditional techniques to winter wheat (Triticum aestivum L.)or maize (Zea mays L.)grown in the fields of Fluvo-aquic soil was investigated using ^15N tracer-micro-plot technique.Results show that:(1) at maturity of wheat,N recovery in plants and N losses of urea and ABC applied at seeding in autumn were 31-39%,and 34-46%,respextively,while the corresponding figures for side-banding at 10 cm depth in early spring were 51-57%,and 5-12%;surface-broadcast of urea followed by irrigation at early spring was as efficient as the side-banding in improving N recovery in plants and reducing N loss,however,such techuique was found less satisfactory with ABC.(2)At the maturity of maize,N recovery in the plants and N loss of urea and ABC sidebanded at seedling stage or prior to tasseling ranged from 23% to 57%,and 9% to 26%,respectively.(3) Either in Wheat or in maize experiment,the majority of residual fertilizer N in soil profile (0-60cm) was in the form of biologically immobilized organic N,however,the contribution of ammonium fixation by clay minerals increased markedly nwith depth in soil profile.(4) Though the proportion of residual fertilizer N was generally highest in the top 20 cm soil layer,considerable reaidual N (nostly 6-11% of the N applied)was found in 60-100 cm soil layers.