Prolonged survival of an environmental Escherchia coli in laboratory soil microcosms

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.     

Three-dimensional variability of soil nitrate-nitrogen in an agricultural field

The aim of this study is to evaluate two different approaches [the layered two-dimensional (2-D) method and a full 3-D approach] to describe the 3-D spatial variability of soil NO₃^--N in the top 1 m of an agricultural field of about 1 ha. NO₃^--N concentrations were determined in layers of 5 cm to a depth of 1 m at 26 locations. These samples were complemented with less intensive sampling at only three depths (0-5, 30-35 and 60-65 cm) at 26 other locations and with topsoil (0-5 cm) samples at another 75 locations. Variogram analysis showed a strong anisotropy when the horizontal dimension was compared to the vertical. A nested model of four structures was used to represent a 3-D variogram. This allowed us to predict the average NO₃^--N concentration for blocks of 5ǹ m (horizontally) by 0.05 m (vertically). A cross-validation showed a clear improvement in using the full 3-D interpolation instead of the layered 2-D approach. The full 3-D interpolation seems to be especially useful in situations where knowledge of the 3-D distribution of soil properties is essential to evaluate soil management practices in respect to environmental considerations, like N fertilisation and the subsequent leaching of N to the ground water, or N₂O emissions.     

Occurrence and survival of coliform bacteria, Escherichia coli and Salmonella in various manure and compost

pp. 865–874
Occurrence and survival of fecal-contamination indicator bacteria (coliform bacteria, Escherichia coli and Salmonella ) in various manure and compost samples collected from 23 composting facilities mostly in Kyushu were investigated by using selective media. Coliform bacteria were detected on desoxycholate agar from 11 (38%) of 29 product samples (15 cow dung manure, 4 poultry manure, 2 biosolid compost and 8 food waste compost) at a range of 10² to 10⁶ cfu g¹ dry matter. From positive samples, 21 isolates of possible coliform bacteria were purified. Among them, species of coliform bacteria ( E. coli , E. vulneria , Pantoea sp. and Buttiauxella agrestis ) were identified whereas isolates of Serratia marcescens , not coliform bacteria, were also obtained, suggesting that careful observation was necessary to avoid false positive counting due to the presence of a red colony of S. marcescens that resembled coliform bacteria. Isolates of E. coli were tested for slide aggregation with a set of antiserum against pathogenic E. coli serotypes and negative reaction was obtained for all the isolates tested. Direct detection of E. coli on Chromocult coliform agar and Salmonella on MLCB agar resulted in none and 2 (17%) of 12 samples tested, respectively. The fate of fecal-contamination indicator bacteria as above was followed during compost production on 7 cases at 6 compost facilities and 4 patterns were observed: fecal-contamination indicator bacteria 1) decreased and finally disappeared, 2) decreased once but re-growth was occurred on products, 3) decreased to some extent but remained in products, 4) was not detected throughout production. These results suggest that some fecal-contamination indicator bacteria may survive compost production and appropriate temperature control would be significant for hygiene control of manure and compost.     

Response of Escherichia coli O157:H7 survival to pH of cultivated soils

Purpose

The Escherichia coli (E. coli) O157:H7 survival dynamics in original and pH-modified agricultural soils were investigated to determinate how E. coli O157:H7 survival responded to the pH values of different soils, identify the relationships between E. coli O157:H7 survival time (t _d ) and soil properties, and assess the potential pathogen contamination after soil pH changed.

Materials and methods

The six soil samples were collected from different provinces of China, and 18 pH-modified soil samples were obtained from original soils by treating the original soils with direct electric current. The E. coli O157:H7 cells were inoculated into 24 soils and incubated at soil moisture of ?33 kPa and 25 °C. The soils were sampled for determining the numbers of E. coli O157:H7 at given time intervals over the incubation. The effects of soil pH change and other properties on the t _d values were analyzed.

Results and discussion

The t _d values in the test soils were between 7.1—24.7 days. Results indicate that soil pH, texture, and free Fe₂O₃ (Fe_d) were the most important factors impacting the t _d values in the test soils. Further, the response of E. coli O157:H7 survival to pH change varied with different soils. In the acidic soils (shorter t _d values), the t _d values decreased as the pH decreased and Fe_d increased, while in the neutral or alkaline soils (pH?≥?6.45, longer t _d values), the t _d values did not change significantly with pH.

Conclusions

The changes of amorphous and free sesquioxides induced by pH change might strengthen the response of E. coli O157:H7 survival to soil pH. Closer attention should be paid to E. coli O157:H7 long survival in soils and its potential environmental contamination risk.     

干旱区人工绿洲间作农田蒸散研究

在黑河流域中游的张掖绿洲区建立了大田环境下的春小麦和夏玉米间作农田能水平衡研究观测点,以气象观测资料为基础,采用波文比能量平衡法(BREB)和参考作物蒸散量—作物系数法(ET₀-K_c)对作物的蒸散进行了计算。结果表明：在一个完整的生长期内,利用波文比能量平衡法得到的间作作物蒸散量为688 mm,日均3.4 mm/d,用参考作物蒸散量—作物系数法得到的作物蒸散量为666 mm,日均3.3 mm/d,两种计算方法得到的蒸散量总值差别小。同期,水文平衡法计算结果为733 mm。利用波文比能量平衡法所得结果的分析表明,试验地在不同生长阶段,ET变化剧烈,生长初期、中期、末期分别为1.19、4.41和2.58 mm/d,其蒸散量分别占全年蒸散总量的7.79%、78.73%和13.48%。ET月变化显示,3月维持在一个较低水平;4月和5月剧烈增加;6月达到最大;此后的7月和8月降低,但仍维持在一个高水平;9月,随着作物进入生长末期,蒸散急剧减小。对ET日内变化分析可知,作物蒸散开始于早晨7∶00～8∶00,在14∶00左右达到最大,19∶00～20∶00趋于0 mm/d。不同生长阶段蒸散强度差异明显。     

Patchy environments and species survival: Chipmunks in an agricultural mosaic

Chipmunks were studied in woods separated by farmland and connected by fencerows. Local extinctions of chipmunks from individual woods were readily recolonised by animals from other patches. Fencerows formed critical connections among woods. A minimum area for considering population survival includes several woods and interconnecting fencerows. Such landscape mosaics should be the elementary units in much conservation planning and management.     

花岗岩地区坡耕地径流泥沙观测试验研究

本文总结分析了三年来对花岗岩地区坡耕地径流泥沙的观测试验资料, 得出以下结论: 1.荒坡地的泥沙流失量大于作物地; 2.作物地覆盖度低于30%以下则比荒坡地的泥沙流失量要大; 3.大于25°的坡耕地, 头两年产量虽然较好, 但第3年以后产量大幅度下降, 并造成大量的泥沙流失, 故种多年生植物为佳。 同时通过试验研究表明: 在花岗岩地区, 泥沙流失量多数来源于坡耕地。 因此搞好坡耕地的综合治理, 是防治水土流失提高单位面积产量的关键措施。     

Effect of treated farm dairy effluent on E. coli,phosphorus and nitrogen leaching and greenhouse gas emissions: a field lysimeter study

Purpose

Land application of farm dairy effluent (FDE) to pasture soils is the preferred practice in New Zealand. Recently, a new FDE treatment technology has been developed to recycle the water for washing the yard Cameron and Di (J Soils Sediments 2018). Here we report a lysimeter study to compare the leaching losses of Escherichia coli, phosphorus (P), and nitrogen (N) and emissions of greenhouse gases from the treated FDE compared with the untreated original FDE.

Materials and methods

Lysimeters were collected from a Balmoral silt loam soil (Typic Dystrudept, USDA) and installed in a field trench facility. Treatments included (1) treated effluent (TE), (2) a mixture of TE and recycled water (M), (3) untreated original FDE (FDE), and (4) water as control. The effluents were applied at a surface application rate of 24 mm on each lysimeter in May and again in September 2017. Measurements included leaching losses of E. coli, total phosphorus (TP), dissolved reactive phosphorus (DRP), total mineral nitrogen (TN), ammonium-N (NH₄⁺-N), and nitrate-N (NO₃^?-N); emissions of nitrous oxide (N₂O), carbon dioxide (CO₂), and methane (CH₄); herbage yield; and N uptake.

Results and discussion

The results showed that E. coli, TP, and DRP leaching losses from the TE were 1.31?×?10¹⁰ cfu/ha, 0.26 kg P/ha, and 0.009 kg DRP/ha and from M treatments were 6.96?×?10⁸ cfu/ha, 0.18 kg P/ha, and 0.004 kg DRP/ha, respectively, which were significantly (P?<?0.05) lower than those from the FDE which were 4.21?×?10¹⁰ cfu/ha, 1.75 kg P/ha, and 0.034 kg DRP/ha, respectively. There were no significant differences in NO₃^?-N leaching losses amongst the different forms of effluents. There were no significant differences in total N₂O, CO₂ emissions, and CH₄ uptakes from the different effluents (P?<?0.05). Herbage dry matter yields and N uptakes were also similar in the different effluent-treated lysimeters.

Conclusions

Results from this research indicate that land application of the treated effluents (TE) or a mixture of TE plus clarified water (M) would result in significant environmental benefits by reducing E. coli and P leaching without increasing greenhouse gas emissions.

     

暗管控制排水棉田氮素流失规律试验

为了研究不同排水出口埋深条件下田间氮素流失规律,2008年在湖北荆州丫角排灌试验站棉田进行暗管控制排水对照试验。结果发现,控制排水条件下,地表氮素累积流失量较暗管多。暗管排水量随控制排水出口埋深减小而减少,较自由暗管排水减少61.3%～86.9%。暗管排水氮素累积流失量主要受排水量影响。NH4+_N累积流失量随排水出口埋深减小而减少;当出口埋深为30 cm时由于浓度增加,NO-3-N、TN累积流失量在两次降雨后较50 cm处理和80 cm处理增加。暗管排水出口埋深控制在30～50 cm之间有利于减少排水量和氮素累积流失量。     

Nitrate leaching in field lysimeters at an agricultural site in Zimbabwe

Abstract. Nitrate leaching in lysimeters containing a tropical sandy agricultural soil was studied over two summers with maize ( Zea mays L.) and one winter season with wheat ( Triticum aestivum L.). The treatments included two moisture regimes and two nitrogen sources, cattle manure and inorganic fertilizer-N (either ammonium nitrate or ammonium sulphate) applied at 100 kg N/ha in the summers. Neither manure nor fertilizer-N was applied in the intervening winter. Leachate volume from the manured lysimeters was mostly larger than from fertilized ones because of poor growth and less evapotranspiration. The largest seasonal nitrate loads (17–39 kg N/ha) were obtained in the wet summer immediately after installation of the lysimeters. Nitrate loads in winter (3.7–18.6 kg N/ha) were larger than those obtained in fertilized (0.6 and 9.3 kg N/ha) and manured (0.3 and 3.0 kg N/ha) lysimeters for the two moisture regimes in the second summer. The drier conditions in the second summer decreased N-mineralization and leaching of manure.     

保鲜运输车温度场分布特性试验研究

为解决果蔬保鲜运输车厢体内温差过大的问题,搭建了基于压差原理的保鲜运输温度场试验平台。通过改变回风道风速、回风道长度、开孔隔板开孔率、堆栈方式、气流导轨等影响气流形式的因素,研究了这些因素对保鲜运输车厢温度场分布的影响。结果表明：回风道风速越大,回风道越长,保鲜厢内的温度场均匀性越好;堆栈方式为中间两侧留空时,厢体内温度场均匀性优于仅中间留空、两侧留空和满载等3种堆栈方式;开孔隔板开孔率对保鲜室中横截面温度场均匀性的影响较大;有气流导轨时的温度场均匀性优于无气流导轨时。当回风道长度为1.5 m,回风道风速为8 m/s,开孔率为16.11%,堆栈方式为中间两侧留空,有气流导轨时,保鲜运输车厢内的温度场均匀性较优,此时保鲜室内中纵截面温度分布的标准差为1.15℃,中横截面温度分布的标准差为2.04℃。研究结果为果蔬保鲜运输车的厢体结构优化提供参考。     

Nitrilotriacetic acid removal in septic tanks: A field study

The removal of nitrilotriacetic acid (NTA) dosed to two full-scale septic tanks each connected to a single dwelling was monitored weekly over a period of 75 weeks. Nitrilotriacetic acid in the septic tank effluent was detected in samples diluted at least 25 times by a differential pulse polarographic technique. After an initial period of stabilization, concentrations of NTA in the effluent at both sites were always > 10 mg L^?1. Mean five-weekly estimated removals of NTA during the last 50 weeks of the study ranged from 33 to 52%. Removal of NTA was probably by solids adsorption only as no acclimatization period or overall increase in removal during the investigation was apparent.     

Detecting zones of abrupt change in soil data, with an application to an agricultural field

We propose a new method for estimating and testing the zones where a variable has discontinuities or sharp changes in the mean. Such zones are called Zones of Abrupt Change (ZACs). Our method is based on the statistical properties of the estimated gradient of the variable. The local gradient is first interpolated by kriging. Then we test whether the estimated local gradient exceeds some critical threshold computed under the null hypothesis of a constant mean. The locations where the local test is rejected define the potential ZACs, which are then tested globally. Using this method, we analysed soil data from an agricultural field. The analysis of the main soil components of the ploughed layer (clay, silt and sand particles and calcium carbonate content) reveals the structural variations in the field, linked to boundaries between soil types. Its application to non‐permanent variables (soil water and mineral nitrogen content of the soil profile to 120 cm taken at several dates) shows that water content has the same ZACs for all dates, whereas mineral nitrogen has none.     

Comparison of field techniques for sampling soil solution in an upland peatland

Abstract. Results from recent studies of peatland biogeochemistry suggest that appropriate soil water sampling techniques are required in order to advance our understanding of peatland soil systems. In a comparative field experiment, concentrations of inorganic solutes and dissolved organic carbon (DOC) were measured in soil water extracted at a depth of 10 cm beneath the surface of deep peat by three techniques: zero-tension (z-t) lysimeters, PTFE suction samplers, and polysulfone suction samplers. The majority of solute concentrations were broadly similar, but mean concentrations of silicon, DOC, iron and aluminium in water extracted by z-t lysimeters and PTFE samplers were in ratios of 1:5; 1:2; 1:5 and 1:3 respectively. Mean conductivity and concentrations of chloride and hydrogen ion were significantly larger in the z-t lysimeter samples, which had sodium, potassium and magnesium to chloride ratios that were very similar to local rainfall. The z-t lysimeters appeared to sample macropores preferentially, while the suction samplers collected micropore water.     

水田行间除草装置设计与试验

为减少化学除草剂的使用,解决现有水田除草机械除草效果差等问题,该研究设计了一种水田行间除草装置,包括压草浮板和除草辊等结构,工作时压草浮板先将压倒杂草,紧接着除草辊将压倒的杂草压入泥中。压草浮板先将杂草压倒,除草辊将杂草压入泥中的几率可提高9.98%。除草辊两端设有倒角,在避免或减少对水稻根系损伤的同时可扩大行间除草区域,最大可增加常规除草宽度的3%。对压草浮板和除草辊进行了参数设计,通过仿真试验分析了行间除草装置与土壤之间的相互作用规律,确定最佳作业条件为入土深度35 mm,前进速度0.8 m/s。以未除草、化学除草、人工除草和不同参数的除草辊为试验因素,以水稻植株高度、产量、产量构成因素和水稻根系参数为试验指标,进行田间试验,试验结果表明,行间除草装置平均除草率最高为87.51%,可以翻动土壤,增加土壤透气性。与常规宽度的除草辊相比,增加除草宽度,扩大行间除草区域最大可提高除草率7.3个百分点。不同的除草处理对水稻植株高度和产量等有显著影响（P<0.05）,机械除草可以促进水稻的生长发育,其产量可以达到甚至超过化学除草和人工除草水平。不同参数的除草辊对植株高度、产量和根系等有显著影响（P<0.05）,增加除草辊宽度同时两端设倒角,可以减少对水稻根系的损伤,有利于水稻的生长发育,提高水稻产量。研究结果可为水田除草机械装备的研究提供参考。     

磁场非热杀菌技术初探

该文旨在采用自行设计的磁场杀菌装置，研究磁场非热杀菌技术。以啤酒酵母、大肠杆菌为对象菌，探求磁通密度、磁场极性转换时间等因素对对象菌的致死率影响规律，研究啤酒酵母磁场非热杀菌动力学。试验结果表明：磁通密度对啤酒酵母、大肠杆菌杀菌率有一定影响，对啤酒酵母、大肠杆菌致死效果最好的磁通密度分别为1.5T，1T。初菌浓度、磁通密度对大肠杆菌致死率有显著影响，当磁通密度为1T的磁场作用8 h，磁场对大肠杆菌致死率为78%。对象菌受磁致死的动力学方程的表达与化学一级反应方程相仿。     

高压电场干燥胡萝卜的试验研究

针对热敏性物料干燥提出一种高压电场干燥的新型干燥技术，以胡萝卜为对象进行高压电场干燥和热风干燥对比试验，及对其干燥后的胡萝卜素进行检测和复水试验。结果表明：高压电场能够加速胡萝卜的干燥，干燥时间缩短43.3%，且能够很好的保留胡萝卜素，高压电场干燥样品的胡萝卜素含量比热风干燥样品高10.86％。高压电场干燥的胡萝卜在复水性上比热风干燥的平均高11.7％。并分析了高压电场干燥机理，认为是电场中载能离子注入、非均匀电场和离子风外部吹动三部分合一的过程，即“电场能传质”。     

Methane emission from an Indonesian rainfed paddy field

In relation to global warming, a great deal of attention has been paid to methane (CH4 ) emission from paddy fields. The amount of CH₄ emitted from paddy fields is now estimated to account for about 12% of the total CH₄ emission according to Prather et al. (1995). Harvested area of rough rice in Asia covered 1,320,000 km² in 1990 and 38% of the area was estimated to be maintained under rainfed conditions (IRRI 1991).