Influence of DOC on MS-2 Bacteriophage Transport in a Sandy Soil

The purpose of this study was to investigate the influence of dissolved organic carbon (DOC) on MS-2 bacteriophage transport in a sandy soil. Miscible-displacement experiments were conducted to examine the retention and transport of MS-2, at two influent concentrations, in the absence and presence of DOC. Effluent recoveries of MS-2 were similar for both sets of experiments. The results of the experiments were analyzed with a mathematical model that incorporated inactivation and rate-limited attachment/detachment. The optimized attachment rate coefficients were similar for all experiments. These results indicate that DOC had no significant influence on the transport of MS-2 in this soil. A mass-balance analysis based on the mathematical-modeling results revealed that attachment was significant during the early stages of the experiments, and that the majority of attached MS-2 became inactivated by the time the experiments were completed.     

Spatial and Temporal Changes of Jet Fuel Contamination in an Unconfined Sandy Aquifer

Leakage of jet fuel from an oil skimmer has resulted in soil and groundwater contamination at the fire fighting training site of the Oslo international airport. The site is located on an unconfined sandy aquifer formed by the Gardermoen ice contact delta. A strong relationship between hydrogeological settings and spatial distribution of the hydrocarbons has been observed. Leaching hydrocarbons constitute a source of dissolved BTEX and naphthalene. Concentration of the dissolved hydrocarbons, electron acceptors and metabolic by-products has revealed concomitant changes in space and in time, in response to groundwater fluctuations. Correlation between high concentrations of hydrocarbons, elevated alkalinity and depleted electron acceptors supports the hypothesis that intrinsic bioremediation has been taking place at the site. Naphthalene, however, has been found persistent under anoxic conditions. Calculations of biodegradation potential indicates that Fe(III) reduction, methanogenesis, nitrate and sulphate reduction are the main factors controlling biodegradation.     

砂质农业土壤养分积累和迁移特点的研究

研究表明，砂质土壤开垦农用后，土壤有机质和保肥性（CEC）明显下降。除大棚蔬菜地外，施用的氮和钾肥不易在土壤中积累，很容易在短时间内沿剖面迁移至地下水，或随地表径流迁移至周围水体。但磷可以活性较高的可提取态形式积累在砂质土壤剖面中，并可逐渐随水进入地下水或迁至地表水，对环境造成危害。长期施用化肥的砂质农地地下水中磷、氮浓度可达到较高的水平。田间观测和模拟淋洗试验表明，砂土中养分极易随水迁移，高浓度的养分流失常发生在施肥后的降雨过程中。因此在砂质土壤上应避免高量施肥，肥料宜少量多次施用，不宜在雨前施用肥料。     

病毒在土壤和地下水中迁移研究综述

病毒能够通过多种途径进入土壤和地下水,并在其中迁移。经病毒污染的地下水被人畜直接饮用后可以造成感染,进而引发多种疾病。为了有效的预防和控制病毒污染,必须对病毒迁移机理进行深入的研究。本文在总结已有研究结果的基础上,综述了土壤和地下水中病毒迁移的过程和机理,以及影响病毒迁移的主要因素,并指出还有待深入的问题和今后的研究方向。     

Transport and Attenuation of Microbial Tracers and Effluent Microorganisms in Saturated Pumice Sand Aquifer Material

Land disposal of treated human and animal effluent through pumice sand soils is a common practice around Rotorua, in the central North Island of New Zealand. There is increasing concern about the possibility of contamination of shallow pumice sand aquifers associated with this practice. In this study, we investigated the transport and attenuation of F-RNA bacteriophages and Escherichia coli in saturated pumice sand aquifer media using a field tracing experiment, and laboratory batch and column studies. The influence of dissolved organic carbon on microbial transport was also investigated by conditioning the 18 cm-long column with ultrafiltered sewage. The CXTFIT curve-fitting program was used to model the experimental data and to determine transport and attenuation parameters. Batch studies showed more than 90% adsorption of both microbial indicators onto pumice sand. High mass removal of microbial indicators was shown in the field (>99% for phage MS2 and E. coli at 2 m down gradient of the injection well; not detected at 6 m) and in the ‘clean sand’ column (65% for phage MS2 and 90% or E. coli). These results suggest that uncontaminated pumice is an effective sorbent capable of retaining microbial contaminants due to high surface area and porosity. However, in the column, with additional dissolved organic carbon, phages showed a progressive reduction in mass removal and retardation between experiments (93%, 75%, and 63% removal; retardation factor: 3.5, 2.5 and 1.2). This suggests that the organic matter competed with phages for the sorption sites, thus promoting phage transport. As a result, viral transport rates may be significantly greater in contaminated compared with uncontaminated pumice sand aquifers.     

模拟降雨下纳米碳对风沙土硝态氮迁移特征的影响

通过在神木六道沟流域开展模拟降雨试验,分别在试验小区上、中、下位置条施不同施加量的纳米碳(0.0%,0.1%,0.5%,0.7%和1.0%)研究其对硝态氮随径流、泥沙迁移及在土壤中再分布过程的影响。设计1.0m×1.0m降雨小区,前期在土壤表层以下5—10cm埋入不同施加量纳米碳,另设不施加纳米碳的小区为参照。采用针孔式人工模拟降雨器进行模拟降雨,降雨强度为90mm/h,降雨历时为40min。降雨前后分别采集土壤剖面土样,降雨过程中定时收集径流及泥沙,用以研究纳米碳对于硝态氮迁移过程的影响。结果表明,在土壤中施加纳米碳,可有效减少坡面产流产沙量,且累计径流量、累计产沙量与土壤中纳米碳施加量呈现负相关关系;纳米碳的施加同样可降低径流、泥沙中硝态氮含量,随着纳米碳施加量的增加,径流和泥沙中硝态氮流失量减少,纳米碳施加量为1.0%时,可减少径流中硝态氮流失65.3%,泥沙中硝态氮流失85.7%;土壤剖面硝态氮变化对比表明,施加纳米碳处理中表层硝态氮含量明显低于对照处理,且在10—15cm出现硝态氮含量峰值,均大于对照处理。通过等效径流迁移深度分析硝态氮流失情况,无纳米碳施加处理的EDR最大,随着纳米碳施加量的增加,各处理的EDR依次减小。综上,在黄绵土中施加纳米碳,可有效减少土壤硝态氮的流失量,在黄土区土壤中施加纳米碳并提高施入纳米碳的比例,对于该地区硝态氮流失的治理具有积极作用。     

中水灌溉条件下含砾砂土污染物运移的初步研究

以宁夏回族自治区大武口市森林公园的含砾砂土为研究对象，通过室内试验，对中水灌溉条件下砂砾质土壤在不同灌水量、多次连续灌水、降雨淋洗等不同来水条件下水分、污染物运移的规律进行了初步的研究，为微污染水用于绿化灌溉对砂砾质土壤中污染物运移及累积的研究提供科学依据。     

土壤胶体对砂质土柱中草萘胺迁移的影响

采用室内砂柱模拟试验方法研究了红壤和黑土两种土壤胶体对草萘胺在砂质土柱中迁移的影响。结果表明,整个淋滤过程中红壤和黑土胶体的回收率比较高,分别达到66．76％和74．75％;胶体促进了草萘胺在砂质土柱中的迁移,与对照相比（无胶体）,加入红壤和黑土胶体后草萘胺的回收率分别提高了9．82％和10．63％。但是吸附在胶体上迁移的草萘胺数量比较少,只占到迁移总量的1．15％（红壤）和1．68％（黑土）,物理非平衡机制可能在迁移过程中起支配作用。     

Rinsing of Saline Water from Road Salt in a Sandy Soil by Infiltrating Rainfall: Experiments,Simulations, and Implications

Saline melt water from road salt applications that has percolated into a fine sandy soil in winter is rinsed out of the soil by infiltrating rainwater in the following warmer seasons. This sequence of saturated and unsaturated flow processes associated with saline water transport in a fine sandy soil was studied by simulation and exploratory laboratory experiments. Experiments in soil columns of 300-μm sand revealed that two rinses of pure water, each of one pore volume, were sufficient to reduce the salt concentration by 99% of its original value in the soil column. Simulated time variations of salt concentration in the effluent from the column agreed with experimental results. Based on simulated and experimental results, a sandy soil must become saturated to experience pore water flow in order to efficiently rinse saline snowmelt water. Depending on the saturated hydraulic conductivity and the soil depth, days, weeks, or months of freshwater infiltration in summer are needed to rinse saline melt water from an unsaturated sandy soil after road salt applications in winter. This explains findings of significant salt concentrations in surface and shallow groundwater during summer months, long after road salt application and infiltration has ceased.     

65 Years Long-term Experiments at Thyrow. Results for Sustainable Crop Production at Sandy Soils

In 1937, K. Opitz founded an agricultural experimental station at Thyrow (Brandenburg County, Germany) where field experiments with a duration of 25 to 65 years still are being managed representing classical long-term field experiments. The location is characterized by low soil fertility, low silty sand soil and unstable water supply and represents arable land of low quality in the lowland of Northern Germany. The long-term collection of results of three different experiments lead to the following approaches for sustainable plant production on marginal sand soils: ” In cereal cropping a well-balanced crop rotation is more important than high amounts of soil organic matter. ” Sustainable reproduction of soil organic matter needs at least 10t/ha and year farm yard manure or straw manure in every second year. ” Irrigation is effective only if additional mineral N fertilizer is applied.     

Groundwater Contamination by Landfill Leachates in a Karstic Aquifer

The contamination of a karstic aquifer by the leachate from the urban solid waste landfill of La Mina (Marbella, south of Spain) has been monitored. A characterization of the karstic media and the different storages of water in the carbonate rock have been deduced by the study of the hydrodynamic and hydrochemical variations in water points of the study network. The chemical compositions of four springs, three pumping wells and five piezometers in the surroundings of the landfill, yield two patterns of hydrochemical behaviour at the contaminated points: (1) the contamination at the piezometers, measured by the concentration of Cl^? and by electrical conductivity, increased over time, but was associated with the precipitation of calcite, evidenced by a reduction in the concentration of HCO₃ ^? and Ca²⁺; (2) at points near the landfill, contamination also increased, but the CO₂ from the landfill provoked an additional dissolution of carbonate minerals, a process reflected in the high concentrations of hydrogen carbonate, calcium and magnesium. The contaminated points were irregularly distributed, the most distant piezometer presenting the greatest impact, whereas no traces of contamination were detected at one piezometer close to the landfill. The irregular distribution of these processes is explained by the heterogeneity of the karstic media, with different types of storage (conduits, fractures/fissures and matrix) and a difference in density between the leachate and the groundwater.     

Monitoring and Modeling Nitrate Persistence in a Shallow Aquifer

A modeling study on fertilizer by-products fate and transport was performed in an unconfined shallow aquifer equipped with a grid of 13 piezometers. The field site was located in a former agricultural field overlying a river paleochannel near Ferrara (Northern Italy), cultivated with cereals rotation until 2004 and then converted to park. Piezometers were installed in June 2007 and were monitored until June 2009 via pressure transducer data loggers to evaluate the temporal and spatial variation of groundwater heads, while an onsite meteorological station provided data for recharge rate calculations via unsaturated zone modeling. The groundwater composition in June 2007 exhibited elevated nitrate (NO ₃ ^? ) and chloride (Cl^?) concentrations due to fertilizer leaching from the top soil. The spatial distribution of NO ₃ ^? and Cl^? was heterogeneous and the concentration decreased during the monitoring period, with NO ₃ ^? attenuation (below 10?mg/l) after 650?days. A transient groundwater flow and contaminant transport model was calibrated versus observed heads and NO ₃ ^? and Cl^? concentrations. Cl^? was used as environmental tracer to quantify groundwater flow velocity and it was simulated as a conservative species. NO ₃ ^? was treated as a reactive species and denitrification was simulated with a first order degradation rate constant. Model calibration gave a low denitrification rate (2.5e^?3 mg-NO ₃ ^? /l/d) likely because of prevailing oxic conditions and low concentration of dissolved organic carbon. Scenario modeling was implemented with steady state and variable flow time discretization to identify the mechanism of NO ₃ ^? attenuation. It was shown that transient piezometric conditions did not exert a strong control on NO ₃ ^? clean up time, while transient recharge rate did, because it is the main source of unpolluted water in the domain.     

不同覆盖模式下砂壤土水盐运移特征研究

地表蒸发引起土壤水分的散失是造成盐分表聚的重要原因之一,土壤表层进行覆盖可改变地表结构,从而影响土壤水分蒸发和盐分迁移过程。为了揭示不同覆盖模式的蓄水控盐效果,通过室内模拟试验,研究了不同覆盖模式下土壤水分入渗过程和水盐迁移特征。试验设置无覆盖(CK)、覆砂(S)、覆砂+覆膜(SM)、覆秸秆+覆膜(JM)和覆秸秆+覆砂(JS)5种模式。结果表明:土壤表层进行的不同覆盖处理会降低土壤湿润锋推进速率和水分入渗速率,具有一定的阻渗作用;湿润锋推进距离与时间符合幂函数F=a·t~b,累积入渗量与时间符合Kostiakov入渗公式,湿润锋推进距离与累积入渗量符合线性关系I=K·Z_f+c。土壤表层进行的不同覆盖处理可有效抑制土壤水分蒸发,土壤保水效果为SMJSSJMCK;随土层深度的增加,土壤含水率减小的趋势逐渐减缓。土壤表层进行的不同覆盖处理也可减弱土壤盐分表聚,缩小盐分在土壤中迁移的范围;覆盖处理的土壤盐分主要在0—20cm范围内迁移,CK在0—35cm范围内。综合考虑不同覆盖模式对土壤水分入渗、抑制水分蒸发和减弱盐分表聚效果,认为砂石覆盖模式是较适合西北旱区的覆盖模式。     

Bacterial Diversity and Aerobic Biodegradation Potential in a BTEX-Contaminated Aquifer

In order to gain insight into the community structure and the biodegradative potential of bacteria residing in a BTEX-contaminated field site, with benzene as main pollutant, an investigation strategy with a variety of cultivation-independent and -dependent approaches was undertaken. Based on 16S ribosomal DNA sequence analysis, sampling stations in the center of the pollution plume were found to be dominated by a bacterial consortium affiliated with various members of the class of Proteobacteria and Firmicutes, including different sporulating and non-sporulating sulfate-reducing bacteria and members of the genus Geobacter. Non-polluted samples retrieved from outside the plume revealed several phylotypes which were also observed in the centre of the plume. Bacterial sequences retrieved from the fringe of the plume were dominated by several genera of beta Proteobacteria subclass which were not associated with other phylotypes obtained in this study. All sampling stations were tested positive for catechol 2,3-dioxygenase genes, indicating the presence of microorganisms with the genetic potential degrading aromatic compounds via the meta-cleavage pathway. The groundwater system at the down-gradient edge of the plume was characterized, in contrast to all other sampling stations in the center and outside the plume, by high numbers of cultivable bacteria and cultivable aerobic benzene and toluene degraders. These findings are also in accordance with the investigations based on fluorescent in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes, suggesting the presence of an actively benzene degrading bacterial community of beta Proteobacteria at the fringe of the pollution plume.     

沙区城镇化过程的生态环境影响

借助“3S”技术、景观分析软件及统计分析手段,对宁夏回族自治区盐池县北部风沙区1989-2007年的城镇化进程和景观格局变化进行了研究.结果表明,盐池县城镇化水平在1985-1990年迅速增长,变化速率在54％～73.4％;1990年后,城镇化水平减缓,由之前平均每年增长3.88％到平均每年减小0.53％.城镇化过程中景观格局变化表现出多样性、均匀度、分离度、破碎度减小,集聚度增大的趋势.典型风沙区盐池县城镇化水平在过去的20 a多中呈阶段性发展,景观格局的变化也表现出明显的阶段性.城镇化对生态环境建设有促进作用,两者相辅相成.在经济发展和正确的政策引导下,生态环境得到改善,特色的城镇化稳步发展.     

Simulation of Groundwater Flow in a Sedimentary Aquifer System Subjected to Overexploitation

Groundwater flow models are applied to a large variety of hydrogeological conditions in different aquifer types, in order to simulate the groundwater flow of the investigated system. This paper aims to present the application of a groundwater flow model for the simulation of a sedimentary aquifer, located in Northern Greece. The simulation involves the period between April 2003 and April 2004, and the model is divided into two distinct stress periods, each containing two different time steps. The simulation of the aquifer is found to be satisfactory, conclusion which is based on both graphical as well as arithmetical verifications. The groundwater flow simulation was achieved by the application of the MODFLOW code.     

浑善达克沙地以北地区沙漠化动态初探

在收集大量前人研究成果和野外调查的基础上,运用RS和GIS技术,以2000年和2005年具有相同时相(秋季)的landsat TM4,3,2波段(分别赋予红、绿、蓝3种颜色)、分辨率为30 m×30 m的标准假彩色合成卫星影像的两期TM影像为信息源,利用Erdas8.7遥感图像处理软件、Arcinfo9.0和Arcview3.3等GIS软件,对浑善达克沙地以北地区的沙漠化土地进行了动态监测研究和分析。结果表明:土地沙漠化总体呈上升扩展的趋势,5 a多来沙漠化土地面积增加了1 366.057 km2,具体表现为轻度、中度、重度沙漠化土地面积分别增加;239.806,1 025.393,850.396 km2,严重沙漠化面积减少了749.539 km2;从全区各旗、县的角度来看,其中苏尼特右旗、苏尼特左旗、西乌珠穆沁旗、锡林浩特的沙漠化发展比较快,增加的面积分别为:1 038.377,185.487,69.431,51.554 km2,克什克腾旗、阿巴嘎旗的发展速度比较慢,增加的面积分别为:5.492,15.715 km2,林西的沙漠化面积基本没有变化。     

Effects of Different Factors on Water Flow and Solute Transport Investigated by Time Domain Reflectometry in Sandy Clay Loam Field Soil

Factors affecting preferential flow and transport in the vadose zone need to be investigated by experiments and simulations to protect groundwater against surface applied chemicals. The objectives of this study were to investigate the effects of several factors (soil structure, initial soil water content (SWC), and application rate) and their interactions on the extent of preferential flow and transport in a sandy clay loam field soil using the time domain reflectometry (TDR) for measuring SWC and electrical conductivity (EC) in 12 treatments, modeling (by HYDRUS-1D and VS2DTI) the measured SWC and EC, and conducting statistical tests for comparing the means of the measured and modeled SWC and EC and solute transport parameters (pore water velocity and dispersion coefficient) obtained by inversely fitting in the CXTFIT program. The study results showed that the applied solution moved faster in the undisturbed, wet initial SWC, and higher application rate experimental conditions than in the disturbed, dry initial SWC, and lower application rate, respectively, based on the analysis of the changes in TDR measured SWC and EC with depth at 1, 2, 5, and 15?h of the experiments. However, the effects of interactive factors or treatments on water flow and solute transport were not clear enough. The modeling results showed that HYDRUS-1D was better than VS2DTI in the estimation of EC and especially SWC, but overall the models had relatively low performances in the simulations. Statistical test results also showed that the treatments had different flow and transport characteristics because they were divided into different groups in terms of the means of SWC and EC and solute transport parameters. These results suggest that similar experiments with more distinct interactions and modeling studies with different approaches need to be considered for better understanding the complex flow and transport processes in the vadose zone.     

毛乌素沙地巴图塔沙柳沙障对植被恢复作用的研究

以毛乌素沙地巴图塔沙柳基地为研究区域,采用野外调查和统计分析相结合的方法,对沙障设置前后的植被动态变化、物种多样性进行研究,进而分析沙柳沙障对植被恢复的影响。研究结果表明:随着沙障设置年限的增加,群落的物种数增加;群落类型由沙障设置前的沙米+沙竹群落发展成沙柳人工植被群落,在演替过程中无物种消失,物种多样性与沙障设置年限基本呈正相关关系。证明流动沙丘上植被恢复过程中沙柳沙障起着重要促进作用。     

毛乌素榆林沙区沙产业发展战略研究

分析了毛乌素榆林沙区发展沙产业的资源优势、技术优势和区位优势,并根据该区沙产业发展现状及存在的问题,提出加速该区沙产业发展的对策。