Tetracycline-Resistant Escherichia coli in a Small Stream Receiving Fish Hatchery Effluent

We examined the impact of the effluent discharged from a freshwater (trout and related species) fish hatchery on the presence of antibiotic-resistant microorganisms in a small stream. There had been no documented use of antibiotics in the hatchery for at least 6 months prior to our study, although a variety of biocides were employed routinely for cleaning. Heterotrophic bacteria and Escherichia coli were isolated from both water column and sediment samples at sites above and below the discharge of the hatchery effluent as well as from the hatchery effluent itself. Randomly chosen isolates (≥96 isolates per site) were tested for their resistance to ampicillin, cephalexin, erythromycin, and tetracycline. Resistance to at least one antibiotic was found in greater than 30% of both the heterotrophic isolates and the E. coli isolates from each of the sites. There were no significant differences among the sites in the proportion of the heterotrophic isolates resistant to any specific antibiotic. The proportion of E. coli isolates resistant to tetracycline in the hatchery effluent and in both the downstream water and sediment samples was significantly higher than in either the upstream water or sediment. These results support the possibility of the hatchery as a source of tetracycline-resistant microorganisms even in the absence of recent use of this antibiotic.     

Phosphorus Removal by Sediment in Streams Contaminated with Acid Mine Drainage

Acid mine drainage (AMD) affects thousands of stream miles in the Appalachian region of the USA and results in elevated concentrations of iron and aluminum in the stream water and sediments and wide ranging pH values. It was hypothesized that these conditions would lead to increased P buffering capacity of the sediments which in turn would cause a decrease in dissolved reactive phosphorus (DRP) in the water column. In the lab fresh Fe, Al, and Mn oxide precipitates all adsorbed DRP strongly but over different pH ranges. Sulfate and calcium ions inhibited adsorption of DRP with Fe oxides but the effect was less apparent with Al oxides. In the field DRP concentration was reduced 54–90% just downstream of an AMD input compared to upstream of the input. In addition the sediment buffering capacity increased and equilibrium phosphate concentration decreased dramatically downstream of the AMD inputs. The strength of the effect and the widespread occurrence of AMD suggest that AMD could be altering the P dynamics of streams and rivers throughout the Appalachian region.     

科技部“十三五”农业面源和重金属污染农田综合防治与修复技术研发重点专项 “农田氮磷淋溶损失污染与防控机制研究”项目正式启动

集约化农田通过投入大量化肥和灌溉提高作物产量,过量的化肥养分通过淋溶损失到地下水,对地下水环境产生巨大影响。这种高强度的人为干预,形成了集约化农业特有的根层-深层包气带-地下水系统。我国农业主产区集约化程度和污染负荷居全球之首,对环境影响为全球典型。我国地下水污染日益严重,80%监测点地下水为Ⅳ和Ⅴ类,与农田淋溶相关的“三氮”(氨氮、亚硝态氮、硝态氮)是最主要的污染源。黑土、潮土和褐土区是我国粮仓,氮磷肥、灌溉过量投入,也是农田氮磷淋溶和地下水污染的易发区和高发区。因此,开展氮磷在根层-深层包气带-地下水淋溶机理和阻控机制的理论研究,是保障国家粮食安全和生态环境可持续的迫切需求。由农田点污染控制向区域农田氮磷淋失风险控制分区及其相关氮磷消减政策法案的结合治理是国际上农田氮磷淋失污染控制的发展趋势。欧洲联盟(EU-27)制定硝酸盐指令(nitrate directive)和水指令(water framework directive),规范肥料与灌溉水的施用量和方式,提高氮磷的利用效率,减少氮磷淋失,并通过划分硝酸盐脆弱敏感区,进行重点防控。由此可见,研究从农田到区域的氮磷淋溶规律和区域阻控途径意义重大。针对这一社会需求,近日,科技部联合农业部启动了第一批“农业面源和重金属污染农田综合防治与修复技术研发”重点专项,“农田氮磷淋溶损失污染与防控机制研究项目”属于专项2016年首批启动的基础研究项目之一。     

Phosphorus Concentrations and Flow in Maize Wet‐Milling Streams

Marketing of coproducts such as corn gluten meal (CGM) and corn gluten feed (CGF) is important to the maize wet‐milling industry. High phosphorus concentrations could lead to limited markets for CGF due to its potential to increase phosphorus in animal wastes. The objective was to measure the concentration and flow of phosphorus in the wet‐milling process and identify streams that could be altered. Samples were taken from 21 process streams of three facilities and the phosphorus content of each was determined. Flow of phosphorus was simulated using a computer model for a 2,700 tonne/day (105,000 bu/day) wet‐milling plant. Phosphorus concentrations of streams varied from <10 mg/kg to >14,000 mg/kg. Phosphorus content of many streams differed significantly among facilities. Flow of phosphorus (kg/day) varied dramatically among streams. However light steepwater, light gluten, and process water streams (5,960, 3,080, and 970 kg/day, respectively) accounted for much of the phosphorus flow. Modification of these streams could reduce phosphorus content of coproducts. The high phosphorus content of either CGF or CGM could be reduced markedly if phosphorus was reduced in the appropriate streams.     

模拟稻田生态系统对农村污水中磷的消纳

通过模拟试验研究了垄作、平作以及在不同施肥水平下,稻田生态系统对农村污水中磷的消纳效果.结果表明:TDP(总水溶性磷)浓度为2.0 mg/L的污水加入1 d后,稻田田面水中DRP(溶解态活性磷)和TDP浓度分别降低了22%～36%和6%～27%;3 d后,DRP和TDP浓度分别降低了73%～89%和53%～66%.各处理田面水中DOP(溶解态有机磷)浓度在污水加入后均迅速上升,3 d后达到峰值0.21～0.30 mg/L;7 d后DOP浓度平均降至0.11 mg/L.田面水中磷素的形态特征,在水稻生长发育前期.田面水中TDP主要以DRP形式存在,在水稻生长发育中期DRP和DOP的含量基本相同;在水稻生长发育后期DRP的百分含量又有升高的趋势.各处理田面水中CODcr,BOD5在污水加入后均迅速上升,3 d后达到峰值(CODcr为64.2～90.0 mg/L,BOD5为2.09～2.76 mg/L),7 d后CODcr,BOD5降至较低水平(CODcr平均为35.0 mg/L,BOD5平均为0.76 mg/L)并保持较长时间,但是在水稻生长发育后期CODcr有上升的趋势.相关分析表明田面水中DOP与BOD5之间存在良好的线性关系,达到极显著水平.     

Characterization of Phosphorus in Sewage Sludge from Different Sources by 31Phosphorus Nuclear Magnetic Resonance Spectroscopy

To investigate the distribution and dynamics of phosphorus (P) in soils for environmental protection and agronomical usage, ³¹P nuclear magnetic resonance spectroscopy (³¹P NMR) was used to characterize the contents and chemical properties of P in sewage sludge from 13 wastewater treatment plants in Shanghai. The samples were extracted with 0.25 M sodium hydroxide (NaOH) / 0.05 M sodium ethylenediamietetraacetic acid (Na₂EDTA) in ratio of 1:20 (w/v). Total P recovery in the extract ranged from 91 to 116% when compared to traditional chemical methods. The dominant forms of P in all samples were inorganic orthophosphates and orthophosphates monoesters. Orthophosphate diesters and pyrophosphates were present in only two and four samples, respectively. This study provides detailed information on the distribution, contents, and chemical properties of P in sewage sludge that may be of value in the utilization of sewage sludge for agronomic purposes.     

湿地植物对农村生活污水中氮磷的净化作用

[目的] 探讨水生植物修复技术对农村生活污水的治理效果,为乡村生态综合治理提供思路借鉴和参考资料。[方法] 通过模拟室内控制试验的方法,选取不同生态型的6种湿地植物为研究对象,分析植株生物量、去除率、植物积累量、底泥吸附量等多项指标变化,研究不同水生植物及其组合对污水中氮磷的净化效果差异以及水生植物系统的脱氮除磷特征。[结果] 无论单一种植组或混合种植组,水生植物系统对污水中TN,NH₄⁺-N,TP均有较好的净化效果,平均去除率分别达到96.6%,93.2%和95.9%,显著高于对照组。单一种植的再力花长势最好,鸢尾地上和地下部分生物量的比值最大,混合种植的美人蕉以及单一种植的梭鱼草相对生长速率最低。挺水植物对氮素的吸收作用更好,苦草对磷的吸收效果更好。植物吸收氮、磷占系统总去除量的比例在6.9%~18.3%和4.1%~13.6%之间,底泥吸附氮、磷占总去除量的比例在14.0%~31.5%和26.3%~68.4%之间。微生物及其他植物的间接作用是植物系统脱氮除磷的主要影响因素。[结论] 再力花、鸢尾及苦草的镶嵌组合是在淮北平原区湿地植物种植的理想选择。对水生植物的组合方式、数量、时间等进行优化配置,能够有效用于农村生活污水的净化。     

Projections of Chloride Concentrations in Urban Lakes Receiving Road De-icing Salt

The chloride concentrations of urban lakes where road de-icing salt (NaCl) is used have increased to levels that can change natural lake-mixing behavior and influence aquatic life. A zero-dimensional model was formulated to project the long-term accumulation of chloride in urban lakes receiving runoff from roads on which road salt is applied. Four model parameters and an initial concentration were obtained by calibrating the model with 5 years (2004–2008) of monthly salinity data from seven lakes in the Minneapolis/St. Paul Twin Cities Metropolitan Area of Minnesota, USA. Three of the seven lakes appear headed towards year-round volume averaged chloride concentrations above the 230-mg/L chronic standard for impairment to aquatic habitat. The two lakes with the lowest projected equilibrium concentrations of chloride have already reached equilibrium. One lake is projected to take an additional 40 years to reach equilibrium under current climate conditions and current road salt application rates. If road salt application rates are reduced in future winters, it is projected that the lakes will respond with noticeably lower chloride concentrations within 5 to 10 years. If road salt applications are discontinued altogether, chloride concentrations are projected to drop to natural levels within 10 to 30 years in all seven lakes. A reduction of application rates by 50% would result in annual volumetric average chloride concentrations below the chronic standard.     

砂质红壤污泥农用后P垂直迁移规律研究

为了解污泥施肥于红壤中,P在剖面中的淋溶和迁移状况,通过田间试验分别对污泥不同类型、施用量和施肥方式在典型红壤坡地P垂直迁移状况进行研究。结果表明:（1）不同处理的污泥施用均可引起Kcl-P和Olsen-P在红砂壤上的垂直迁移,含量随剖面深度而降低,养分积累主要集中在0—50 cm土层;（2）污泥类型、施肥量、施用方式都对P素迁移具有影响,随着施肥量的增加,剖面各层Kcl-P和Olsen-P含量增加,撒施处理比穴施更易造成Kcl-P和Olsen-P剖面深层迁移,干污泥养分含量随剖面深度变化更剧烈,更易造成Kcl-P深层迁移;（3）污泥撒施0—30 cm土层Olsen-P累计量占0—80 cm总累计量60%以上,基本可以反映剖面Olsen-P含量水平和迁移潜力。     

农村污水加入对模拟稻田生态系统中氮、磷的影响

在温室内,以中性紫色水稻土为基质,水稻(Oryza sativa)为植被构建了模拟稻田生态系统用以处理农村污水,研究了外源污水(TN 15.0mg/L,其中NH4+-N 13.5mg/L,NO3--N 1.5mg/L;TP 2.0mg/L)加入4种系统后,土壤和田面水中各种形态氮、磷、pH等的动态变化。结果表明,外源污水加入后3d土壤中NH4+-N、NO3--N、pH均达到峰值,其中NH4+-N 29.4～46.5mg/kg,NO3--N 12.3～21.4mg/kg,pH 7.9～9.1,完全施肥处理显著高于减量施肥处理,垄作与平作之间差异不显著。7d后NH4+-N、NO3--N、pH显著降低,处理之间差异不显著。外源污水加入后3d,土壤中NH4+-N增加了5.76～9.70g/m2,显著高于田面水中NH4+-N的损失量1.15～1.34g/m2,田面水和土壤中NO3--N分别上升了0.64～0.91g/m2和2.02～4.12g/m2。表明田面水中NH4+-N的减少可能对土壤中NH4+-N的升高有一定的贡献,而田面水中NO3--N的增加量可能来自土壤。土壤中碱解氮和Olsen-P浓度均在污水加入后1d达到峰值,完全施肥处理显著高于减量施肥处理,垄作与平作之间差异不显著。土壤中TN和TP在试验期间有下降的趋势,但是差异不显著。相同施肥条件下,垄作较平作能够获得更高的生物产量,意味着能够带走更多的氮、磷。     

Phosphorus Retention Mechanisms in the Sediment of an Eutrophic Mining Lake

A small, highly eutrophic mining lake (Golpa IV) in eastern Germany with a continuous input of nutrients and metals was used to study the mechanisms of phosphorus (P) fixation in the sediment. The sediment (0-15 cm) is characterised by high contents of iron (96 mg g-1 DW), aluminium (37.3 mg g-1 DW) and sulphur (54.3 mg g-1 DW) and an extreme accumulation of some trace metals. Despite oxygen free conditions in the hypolimnion and intensive sulphate reduction in the sediment, high P retention rates could be calculated from dated sediment cores (1986-1995: 11 g P m-2 a-1). The lake has shown a rapid response to reduction of P loading. In some sediment layers unusually high total sediment P concentrations with more than 24 mg P g-1 DW were observed. More than 80% of total sediment P was bound in the BD-SRP and NaOH-SRP fractions (extraction scheme according to Psenner et al., 1984) which indicates that a substantial portion of deposited P is immobilised in an Fe or Al bound form. This corresponds well with the presence of oxidised Fe species at all sediment depths. Furthermore thermodynamic calculations indicate that vivianite precipitation is favourable in deeper anoxic sediment layers. The inventory or input of Fe or Al seems to be more important for the permanent P immobilisation in the sediment of the investigated mining lake than redox forced mobilisation processes (e.g. iron or sulphate reduction).     

几种水生观赏植物对城市污水的生理响应

主要研究了石菖蒲、泽泻、菖蒲、黄花鸢尾、千屈菜这5种常见水生观赏植物对城市污水的生理生化变化,分别在第5 d,10 d和15 d对植物叶片膜脂过氧化(MDA、电导率)、体内保护系统酶(CAT、POD)、非酶类(游离Pro)及根系活力等抗性生理指标进行测定,探讨植物抗污水逆境的能力。研究结果表明,不同植物适应污水环境能力不同。其中,黄花鸢尾在污水处理下的抗逆性最强,与对照相比其电导率和丙二醛含量变化不大,而一些植物在实验初期受到污水胁迫,电导率和丙二醛含量较对照有上升的现象;同时,实验初期黄花鸢尾中游离Pro含量、POD和CAT活性及根系活力的增强,菖蒲根系活力的增加,千屈菜POD、CAT酶活性的升高,泽泻根系活力、POD、CAT酶活性的升高,都是水生植物对污水环境的生理适应。黄花鸢尾抗逆性强,是一种值得推荐的净化污水的湿地植物。     

Medium-scale Plant Experiment of Sewage Sludge-based Phosphorus Fertilizers from Large-scale Thermal Processing

ABSTRACT

Phosphorus (P) recycling from sewage sludge for agricultural needs has to meet requirements for agricultural implementation, such as short and long-term P-plant-availability under field conditions. Field experiments often bring no evaluable results, because agricultural soils got a high potential of P-supply even if they are classified as low in P-supply according to the CAL extraction method. The present study presents a possible way to investigate the P-plant-availability of P-recycling-fertilizers under field-like conditions. The plant experiments are firstly performed in small Mitscherlich pots in growth chambers and subsequently in containers with a high soil volume of 170 kg under greenhouse conditions, in which plants can grow until ripening. The tested P-recycling-fertilizers were produced from sewage sludge in a large-scale thermal process. It was a two-step treatment process performed with a pyrolysis of sewage sludge at 550°C (SSC-550) and a subsequent thermochemical post-treatment at 950°C with Na₂SO₄ (SSA-Na) and HCl + Na₂SO₄ (SSA-HCl/Na) as additives. The results show, that the P-recycling-products from pyrolysis got an adequate long-term but a 65% lower short-term P-plant-availability compared to triple-superphosphate. SSA-Na and SSA-HCl/Na show both a high short and long-term P-plant-availability comparable to triple-superphosphate. This can be explained by their highly plant-available P-compound CaNaPO₄.     

6种水生植物及其组合对模拟污水中磷的净化效果

[目的]针对河流湖泊水体污染严重现状,选择6种水生植物进行水质净化试验,为污染水体的水生植物治理提供选择依据。[方法]选择6种具观赏效果的水生植物菖蒲、美人蕉、大薸、凤眼莲、金鱼藻、穗花狐尾藻,采用静态水培的方法,研究6种水生植物及其组合对不同浓度模拟污水中总磷净化效果。[结果]单一水生植物试验中,凤眼莲在高(2 mg/L)、中浓度(0.5 mg/L)磷水体中总磷去除效果最好,去除率分别为95.9%,93.4%。金鱼藻在低浓度磷(0.1 mg/L)水体中总磷去除效果最好,去除率为91.1%。组合水生植物试验中,高浓度磷水体中金鱼藻+菖蒲+凤眼莲的水生植物组合对水体中总磷去除效果最好,去除率为96%。中浓度磷水体中穗花狐尾藻+菖蒲+凤眼莲水生植物组合总磷去除效果最好,去除率为98.8%。低浓度磷水体中穗花狐尾藻+菖蒲+大薸水生植物组合总磷去除效果最好,去除率为94.3%。[结论]选择的6种水生植物对总磷均有一定的去除效果,对水生植物的种植数量、面积、时间以及组合方式进行优化配置,可用于污染水体水质净化。     

Effects of Urban Sewage on Dissolved Oxygen,Dissolved Inorganic and Organic Carbon,and Electrical Conductivity of Small Streams along a Gradient of Urbanization in the Piracicaba River Basin

In Brazil most of the urban sewage is dumped without treatment into rivers. Because of this, it is extremely important to evaluate the consequences of organic matter rich sewage on the structure and functioning of river ecosystems. In this study we investigated the effects of urban sewage on the dissolved oxygen (O₂), dissolved inorganic (DIC) and organic carbon (DOC), and electrical conductivity (EC) in 10 small streams of the Piracicaba River basin, southeast region of Brazil. In the Piracicaba River basin, which is one of the most developed regions of the country, only 16% of the total sewage load generated is treated. These streams were classified into two groups, one with heavy influence of urban sewage and another with less influence. Both concentrations and seasonal variability were distinct between the two groups. The streams that received sewage effluent had a combination of low O₂ with high DIC, DOC, and EC. In the polluted streams, concentrations of dissolved carbon forms and EC were higher and O₂ concentration lower during the low water period. In the less polluted streams seasonal variations in concentrations were small. We also investigated the efficiency of a sewage treatment plant installed two years ago in the catchment of one of these streams. It was observed an increase in the O₂ concentration after the beginning of the treatment, and a decrease of DIC and DOC concentrations especially during the low water period. However, no significant change was observed in the EC, suggesting that the concentrations of major ions is still unaltered, and that a secondary treatment is necessary in order to reduce ion load into the stream.     

Evaluation of Urban Groundwater Contamination from Sewage Network in Kuwait City

To investigate the possible contamination of groundwater by wastewater leaked from the underground sewage network, water samples from 29 monitoring wells, drilled at strategic locations across Kuwait City and the adjacent residential areas, were analyzed for their inorganic and organic constituents including isotopic composition (oxygen-18 and deuterium) that can be used as tracers for source identification. As a non-conventional method, statistical processing in the form of hierarchical cluster and discriminant function analyses of the inorganic and organic data was used to group the wells according to the degree of possible contamination of groundwater. It was concluded from this analysis that more than half of the wells (17) showed little evidence of such contamination. Sample from only one of the wells suggested high degree of contamination (concentrations of total coliform bacteria (TCB) and fecal coliform bacteria (FCB) >2,000 MPN/100 ml and boron (B) concentration >11 mg/l) whereas another well appeared significantly contaminated (TCB?>?2,000 MPN/100 ml; FCB?>?900 MPN/100 ml; B?>?4 mg/l). Three of the wells were possibly contaminated (1,000?<?TCB?<?2,000 MPN/100 ml; 15?<?FCB?<?500 MPN/100 ml; 3?<?B?<?11.5 mg/l), and the rest of the seven wells were classified as possibly not contaminated (TCB?>?2,400 MPN/100 ml; FCB?<?40 MPN/100 ml; B?<?5 mg/l). The overall conclusion was that the leakage from sewage network was affecting groundwater in localized areas only. Isotope data, available for water samples from eight of the monitoring wells, tended to support the aforesaid conclusions. However, because of the use of bailing as the sampling method and lack of actual leakage surveillance, further studies need to be carried out to strengthen the reliability of these findings.     

南京城市土壤磷的形态和吸附-解吸特征

研究了南京城市土壤有机磷、各形态无机磷的含量和比例以及磷的吸附 -解吸特性。结果表明 :随着土壤全磷含量的增加 ,Al-P、Fe -P、O -P、Ca -P含量、Al-P占全磷的比例增加 ,但有机磷占全磷的比例、Fe -P占全磷的比例减少 ;与非城区土壤相比较 ,城市土壤磷的吸附量低 ,磷的解吸量和解吸率高 ;城市土壤中Al -P的含量及其在全磷中的比例较高 ,而磷的吸附量低、解吸率高是导致城市地下水磷浓度偏高的重要原因之一。     

丛枝菌根真菌促进植物摄取土壤磷的作用机制

磷在土壤中易被固定沉淀,在植物磷利用率低的情况下,过度施肥会造成磷肥浪费,可能通过地表径流、地下水溶解等方式,造成水体富营养化产生面源污染,对人类生产生活造成较大影响。丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)和植物结合所形成的共生菌根可以显著增强植株对磷的吸收利用。通过AMF可以提高宿主植株对磷的吸收转运的特性,从AMF促进植株对磷元素的摄取机制、AMF促进植物磷摄取分子机理、AMF作用下根系分泌物对植株磷利用的影响与根际微生物对AMF磷元素利用的影响4个方面的研究进展进行分析总结。AMF可以通过改变宿主植株的根系形态和菌丝网络的形成,扩大植株对养分吸收范围;释放有机酸、磷酸酶和质子等根系分泌物改变土壤结构和理化性质,与根际微生物共同作用降解土壤中难溶性磷酸盐;诱导相关磷转运蛋白基因的特异性表达,提高植株对磷的转运能力而促进其吸收。