Erratum to “Effects of intensive urbanization on the intrusion of shallow groundwater into deep groundwater: Examples from Bangkok and Jakarta”

Asian megacities have severe pollution problems in both coastal and urban areas. In addition, the groundwater potential has decreased and land subsidence has occurred because of intensive groundwater pumping in urban areas. To prevent the adverse effects of urbanization on groundwater quality, it is necessary to confirm the changes in groundwater flow and contaminant transport caused by urbanization. We examined the effects of urbanization on contaminant transport in groundwater. The research areas were located around Bangkok, Thailand, and akarta, Indonesia, cities with populations of approximately 8 and 12 million, respectively. Each metropolitan city is located on a river delta and is adjacent to a bay. We measured the water level and collected water samples at boreholes at multiple depths (100 to 200 m) in 2004 and 2006 in Bangkok and Jakarta, respectively. The current hydraulic potential is below sea level in both cities because of prior excess abstraction of groundwater. As a result, the direction of groundwater flow is now downward in the coastal area. The Cl⁻ concentration and δ¹⁸O distributions in groundwater suggest that the decline in hydraulic potential has caused the intrusion of seawater and shallow groundwater into deep groundwater. Concentrations of Mn and NO3⁻-N in groundwater suggest the intrusion of these contaminants from shallow to deep aquifers with downward groundwater flow and implies an accumulation of contaminants in deep aquifers. Therefore, it is important to recognize the possibility of future contaminant transport with the discharge of deep groundwater into the sea after the recovery of groundwater potential in the coastal areas.     

Sources of nitrate and ammonium contamination in groundwater under developing Asian megacities

The status of nitrate (NO(3)(-)), nitrite (NO(2)(-)) and ammonium (NH(4)(+)) contamination in the water systems, and the mechanisms controlling their sources, pathways, and distributions were investigated for the Southeast Asian cities of Metro Manila, Bangkok, and Jakarta. GIS-based monitoring and dual isotope approach (nitrate delta(15)N and delta(18)O) suggested that human waste via severe sewer leakage was the major source of nutrient contaminants in Metro Manila and Jakarta urban areas. Furthermore, the characteristics of the nutrient contamination differed depending on the agricultural land use pattern in the suburban areas: high nitrate contamination was observed in Jakarta (dry fields), and relatively lower nutrients consisting mainly of ammonium were detected in Bangkok (paddy fields). The exponential increase in NO(3)(-)-delta(15)N along with the NO(3)(-) reduction and clear delta(18)O/delta(15)N slopes of NO(3)(-) ( approximately 0.5) indicated the occurrence of denitrification. An anoxic subsurface system associated with the natural geological setting (e.g., the old tidal plain at Bangkok) and artificial pavement coverage served to buffer NO(3)(-) contamination via active denitrification and reduced nitrification. Our results showed that NO(3)(-) and NH(4)(+) contamination of the aquifers in Metro Manila, Bangkok, and Jakarta was not excessive, suggesting low risk of drinking groundwater to human health, at present. However, the increased nitrogen load and increased per capita gross domestic product (GDP) in these developing cities may increase this contamination in the very near future. Continuous monitoring and management of the groundwater system is needed to minimize groundwater pollution in these areas, and this information should be shared among adjacent countries with similar geographic and cultural settings.     

Trends in urbanization and patterns of land use in the Asian mega cities Jakarta,Bangkok, and Metro Manila

Asian mega cities have experienced rapid population growth and continue to grow. Urbanization in those areas is proceeding differently from the patterns of city growth experienced in Western countries. Understanding the characteristics of Asian urbanization will be indispensable for the establishment of a local landscape planning system. In this study, we used the Clark linear exponential model and the Newling quadratic exponential model to compare the spatial distribution of population densities in three Southeast Asian mega cities: Jakarta, Bangkok, and Metro Manila. We analyzed land-use patterns in each of the three cities by examining the mixture of urban and agricultural land use. The Clark and Newling models showed that the three cities were at different stages of urbanization. Jakarta had entered the suburbanization stage, Metro Manila was still at an early stage of urbanization, and Bangkok was at an intermediate stage between Jakarta and Metro Manila. Analysis of spatial patterns revealed areas of mixed land use within and around the city region in the three cities and that these areas of mixed land use would shift outward as urbanization proceeds. These findings indicate that planning concepts need to respect the vernacular landscape of each Asian mega cities as well as its stage of urbanization.     

Erratum to “Sources of nitrate and ammonium contamination in groundwater under developing Asian megacities”

The status of nitrate (NO₃⁻), nitrite (NO₂⁻) and ammonium (NH₄⁺) contamination in the water systems, and the mechanisms controlling their sources, pathways, and distributions were investigated for the Southeast Asian cities of Metro Manila, Bangkok, and Jakarta. GIS-based monitoring and dual isotope approach (nitrate δ¹⁵N and δ¹⁸O) suggested that human waste via severe sewer leakage was the major source of nutrient contaminants in Metro Manila and Jakarta urban areas. Furthermore, the characteristics of the nutrient contamination differed depending on the agricultural land use pattern in the suburban areas: high nitrate contamination was observed in Jakarta (dry fields), and relatively lower nutrients consisting mainly of ammonium were detected in Bangkok (paddy fields).The exponential increase in NO₃⁻-δ¹⁵N along with the NO₃⁻ reduction and clear δ¹⁸O/δ¹⁵N slopes of NO₃⁻ (∼ 0.5) indicated the occurrence of denitrification. An anoxic subsurface system associated with the natural geological setting (e.g., the old tidal plain at Bangkok) and artificial pavement coverage served to buffer NO₃⁻ contamination via active denitrification and reduced nitrification.Our results showed that NO₃⁻ and NH₄⁺ contamination of the aquifers in Metro Manila, Bangkok, and Jakarta was not excessive, suggesting low risk of drinking groundwater to human health, at present. However, the increased nitrogen load and increased per capita gross domestic product (GDP) in these developing cities may increase this contamination in the very near future. Continuous monitoring and management of the groundwater system is needed to minimize groundwater pollution in these areas, and this information should be shared among adjacent countries with similar geographic and cultural settings.     

北京通州区地下水污染评价及监测网布设

为准确刻画通州区地下水污染的分布特征,基于2008年6月采集的151个浅、中、深层地下水样进行了分层污染评价。采用数理统计学方法,计算了各层不同级别的污染面积。初步探讨了污染机理和原因。结果表明研究区内浅层地下水均已经遭受污染且污染程度较为严重,中层地下水绝大部分显示为轻度污染,而深层地下水只在西部小范围地区遭受轻度污染。提出了“重点突出、区域控制、分层监测、有机无机并重”监测网布设原则,整合并新施工监测井,形成了立体分层的地下水监测网络：其中污染源专项监孔共计71眼,区域浅层监测孔共计48眼,区域中层共计36眼,区域中深层共计26眼,区域深层共计22眼。最后对监测网的运行情况进行了简要介绍。     

Dimensionierung wasserwirtschaftlicher Vorranggebiete in Kies-Grundwasserleitern unter Berücksichtigung von Schadstofftransport

Delineating of areas surrounding designated drinking water protection zones provides an administrative tool for preventing groundwater contamination. This delineation can be difficult for gravel aquifers due to their extended catchment areas and high groundwater flow velocities. A practical approach is proposed based on a combined consideration of aquifer characteristics such as surficial cover, recharge rate, surface area, groundwater flow velocity and those for common contaminants (transport, sorption and degradation behaviours). The possibility of applying this method to delimit the broader III and III B protection zones is also suggested.     

Natural denitrification in the Kakamigahara groundwater basin,Gifu prefecture,central Japan

Although nitrate is recognized as the most common groundwater contaminant due to growing anthropogenic sources, such as agriculture in particular, its adverse effects on human and animal health are debatable. The current issue, however, is to control and reduce nitrate contamination with regards to the long residence time of groundwater within aquifers. Denitrification has recently been recognized for its ability to reduce high nitrate concentrations in groundwater. The Kakamigahara groundwater basin, Gifu prefecture, Japan, witnessed rising levels of nitrate (>12 mg/l NO(3)-N) originating from agricultural sources. Chemical analyses for the determination of major constituents of groundwater and delta(15)N of residual nitrate were performed on representative groundwater samples in order to fulfill two main objectives. One is to investigate the current situation of nitrate groundwater pollution. The second objective is to determine whether the denitrification is a potential natural mechanism, which eliminates nitrate pollution in the Kakamigahara aquifer. Agricultural nitrate contamination of groundwater was obvious from characteristically high concentrations of Ca(2+), Mg(2+), NO(3)(-) and SO(4)(2-). High nitrate concentrations were found on the eastern side of the basin in association with vegetable cultivation fields, and decreased gradually towards the west of the basin along the direction of groundwater flow. The decrease of nitrate concentration was conveniently coupled with increase of HCO(3)(-) (the heterotrophic denitrification product), pH and delta(15)N of residual nitrate (due to isotopic fractionation) from east to west. Therefore, denitrification in situ is continuously removing nitrate from the Kakamigahara groundwater system.     

Reconstruction of the thermal environment evolution in urban areas from underground temperature distribution

It is possible to estimate the ground surface temperature (GST) history of the past several hundred years from temperature profiles measured in boreholes because the temporal variation in GST propagates into the subsurface by thermal diffusion. This “geothermal method” of reconstructing GST histories can be applied to studies of thermal environment evolution in urban areas, including the development of “heat islands.” Temperatures in boreholes were logged at 102 sites in Bangkok, Jakarta, Taipei, Seoul and their surrounding areas in 2004 to 2007. The effects of recent surface warming can be recognized in the shapes of most of the obtained temperature profiles. The preliminary results of reconstruction of GST histories through inversion analysis show that GST increased significantly in the last century. Existing temperature profile data for the areas in and around Tokyo and Osaka can also be used to reconstruct GST histories. Because most of these cities are located on alluvial plains in relatively humid areas, it is necessary to use a model with groundwater flow and a layered subsurface structure for reconstruction analysis. Long-term records of subsurface temperatures at multiple depths may demonstrate how the GST variation propagates downward through formations. Time series data provide information on the mechanism of heat transfer (conduction or advection) and the thermal diffusivity. Long-term temperature monitoring has been carried out in a borehole located on the coast of Lake Biwa, Japan. Temperatures at 30 and 40 m below the ground surface were measured for 4 years and 2 years, respectively, with a resolution of 1 mK. The obtained records indicate steady increases at both depths with different rates, which is probably the result of some recent thermal event(s) near the surface. Borehole temperatures have also been monitored at selected sites in Bangkok, Jakarta, and Taiwan.     

Groundwater quality in Scotland: major ion chemistry of the key groundwater bodies

Groundwater in Scotland is, for the most part, weakly to moderately mineralised and dominated by the Ca and HCO3 ions. The aquifer systems are almost entirely unconfined and most groundwater remains in contact with oxygen; some reducing groundwaters occur in deeper isolated cracks and joints within the many fractured bedrock aquifers such as Devonian sandstones. Groundwater depleted in oxygen is also common in the Coal Measures in the Midland Valley as a direct result of past coal and oil shale mining, when iron and other metals are taken into solution as the abandoned mine workings are allowed to flood. Low pH groundwaters are rare but do occur where calcite is absent in some basement rocks. Marine intrusion of coastal aquifers occurs locally in East Lothian and parts of Morayshire. Deeper circulating groundwaters are responsible for some of the more exotic spa waters, notably at Bridge of Earn near Perth. Nitrate contamination of groundwater is increasing in some areas, and is most prevalent in the south of Scotland. The Devonian aquifer in Fife and parts of the Permian sandstone aquifers of south-west Scotland are the worst affected.     

Anthropogenic effects on the subsurface thermal and groundwater environments in Osaka, Japan and Bangkok, Thailand

Anthropogenic effects in both Osaka and Bangkok were evaluated to compare the relationships between subsurface environment and the development stage of both cities. Subsurface thermal anomalies due to heat island effects were found in both cities. The Surface Warming Index (SWI), the departure depth from the steady geothermal gradient, was used as an indicator of the heat island effect. SWI increases (deeper) with the magnitude of heat island effect and the elapsed time starting from the surface warming. Distributions of subsurface thermal anomalies due to the heat island effect agreed well with the distribution of changes in air temperature due to the same process, which is described by the distribution of population density in both Osaka and Bangkok. Different time lags between groundwater depression and subsidence in the two cities was found. This is attributed to differences in hydrogeologic characters, such as porosity and hydraulic conductivity. We find that differences in subsurface degradations in Osaka and Bangkok, including subsurface thermal anomalies, groundwater depression, and land subsidence, depends on the difference of the development stage of urbanization and hydrogeological characters.     

Dynamics of solutes and dissolved oxygen in shallow urban groundwater below a stormwater infiltration basin

Artificial recharge of urban aquifers with stormwater has been used extensively in urban areas to dispose of stormwater and compensate for reduced groundwater recharge. However, stormwater-derived sediments accumulating in infiltration beds may act as a source of dissolved contaminants for groundwater. Concentrations of hydrocarbons, heavy metals, nutrients and dissolved oxygen (DO) were monitored at multiple depths in shallow groundwater below a stormwater infiltration basin retaining large amounts of contaminated organic sediments. Multilevel wells and multiparameter loggers were used to examine changes in groundwater chemistry occurring over small spatial and temporal scales. Rainfall events produced a plume of low-salinity stormwater in the first 2 m below the groundwater table, thereby generating steep vertical physico-chemical gradients that resorbed during dry weather. Heavy metals and hydrocarbons were below reference concentrations in groundwater and aquifer sediments, indicating that they remained adsorbed onto the bed sediments. However, mineralization of organic sediments was the most probable cause of elevated concentrations of phosphate and DOC in groundwater. DO supply in groundwater was severely limited by bed respiration which increased with temperature. Cold winter stormwater slightly re-oxygenated groundwater, whereas warm summer stormwater lowered DO concentrations in groundwater. Among several results provided by this study, it is recommended for management purposes that infiltration practices should minimize the contact between inflow stormwater and organic sediments retained in infiltration basins.     

开采条件下海河流域平原区浅层地下水数值模拟研究

本文利用地下水数值模拟系统(GMS),建立了能反映海河流域平原区地下水含水层结构及其水流特性的大区域水文地质概念模型和地下水流模型,重点研究了在无开采井条件下地下水开采强度时空分布的特征,模拟了平原区1965~2005年41年间的地下水流场及漏斗的演变过程,综合分析了海河流域平原区浅层含水层长期开采条件下地下水系统的演变过程以及地下水开采带来的影响。同时,对所建立的地下水数值模型就流场、漏斗变化以及水文地质参数等多方面进行了识别和验证。采用经过率定和验证的模型,预测分析了水资源配置制定的地下水限采方案,为南水北调实施后对海河流域地下水的修复作用以及其它可能的影响提供了可靠的分析手段和措施。     

Influence of traditional agricultural practices on mobilization of arsenic from sediments to groundwater in Bengal delta

In the wake of the idea that surface derived dissolved organic carbon (DOC) plays an important role in the mobilization of arsenic (As) from sediments to groundwater and may provide a vital tool in understanding the mechanism of As contamination (mobilization/fixation) in Bengal delta; a study has been carried out. Agricultural fields that mainly cultivate rice (paddy fields) leave significantly large quantities of organic matter/organic carbon on the surface of Bengal delta which during monsoon starts decomposing and produces DOC. The DOC thus produced percolates down with rain water and mobilizes As from the sediments. Investigations on sediment samples collected from a paddy field clearly indicate that As coming on to the surface along with the irrigation water accumulates itself in the top few meters of sediment profile. The column experiments carried out on a 9 m deep sediment profile demonstrates that DOC has a strong potential to mobilize As from the paddy fields and the water recharging the aquifer through such agricultural fields contain As well above the WHO limit thus contaminating the shallow groundwater. Experiment also demonstrates that decay of organic matter induces reducing condition in the sediments. Progressively increasing reducing conditions not only prevent the adsorption of As on mineral surfaces but also cause mobilization of previously sorbed arsenic. There seems to be a cyclic pattern where As from deeper levels comes to the surface with irrigational water, accumulates itself in the sediments, and ultimately moves down to the shallow groundwater. The extensive and continual exploitation of intermediate/deep groundwater accelerates this cyclic process and helps in the movement of shallow contaminated groundwater to the deeper levels.     

The significance of colloids in the transport of pesticides through Chalk

Agrochemical contamination in groundwater poses a significant long term threat to water quality and is of concern for legislators, water utilities and consumers alike. In the dual porosity, dual permeability aquifers such as the Chalk aquifer, movement of pesticides and their metabolites through the unsaturated zone to groundwater is generally considered to be through one of two pathways; a rapid by-pass flow and a slower 'piston-flow' route via the rock matrix. However, the dissolved form or 'colloidal species' in which pesticides move within the water body is poorly understood. Following heavy rainfall, very high peaks in pesticide concentration have been observed in shallow Chalk aquifers. These concentrations might be well explained by colloidal transport of pesticides. We have sampled a Chalk groundwater beneath a deep (30 m) unsaturated zone known to be contaminated with the pesticide diuron. Using a tangential flow filtration technique we have produced colloidal fractions from 0.45 microm to 1 kDa. In addition, we have applied agricultural grade diuron to a typical Chalk soil and created a soil water suspension which was also subsequently fractionated using the same filtration system. The deep groundwater sample showed no evidence of association between colloidal material and pesticide concentration. In comparison, despite some evidence of particle trapping or sorption to the filters, the soil water clearly showed an association between the <0.45 microm and <0.1 microm colloidal fractions which displayed significantly higher pesticide concentrations than the unfiltered sample. Degradation products were also observed and found to behave in a similar manner to the parent compound. Although relatively large colloids can be generated in the Chalk soil zone, it appears transport to depth in a colloidal-bound form does not occur. Comparison with other field and monitoring studies suggests that rapid by-pass flow is unlikely to occur beneath 4-5 m. Therefore, shallow groundwaters are most at risk from rapid transport of high concentrations of pesticide-colloidal complexes. The presence of a deep unsaturated zone will mean that most of the colloidal-complexes will be filtered by the narrow Chalk pores and the majority of pesticide transport will occur in a 'dissolved' form through the more gradual 'piston-flow' route.     

子牙河—海河流域浅层地下水矿化度分布及成因

对天津地区子牙河—海河干流流域浅层地下水矿化度及水化学类型分布进行了调查,发现地下水矿化度由低到高、从微咸水到咸水再到盐卤水渐变特征明显,对其形成原因进行了分析,认为地下水补给不足以及深层地下水开采形成降落漏斗和渤海湾风暴潮等引起的海水入侵是导致该分布特征的主要原因。     

Sources and controls for the mobility of arsenic in oxidizing groundwaters from loess-type sediments in arid/semi-arid dry climates - evidence from the Chaco-Pampean plain (Argentina)

In oxidizing aquifers, arsenic (As) mobilization from sediments into groundwater is controlled by pH-dependent As desorption from and dissolution of mineral phases. If climate is dry, then the process of evaporative concentration contributes further to the total concentration of dissolved As. In this paper the principal As mobility controls under these conditions have been demonstrated for Salí River alluvial basin in NW Argentina (Tucumán Province; 7000 km²), which is representative for other basins or areas of the predominantly semi-arid Chaco-Pampean plain (1,000,000 km²) which is one of the world’s largest regions affected by high As concentrations in groundwater. Detailed hydrogeochemical studies have been performed in the Salí River basin where 85 groundwater samples from shallow aquifers (42 samples), deep samples (26 samples) and artesian aquifers (17 samples) have been collected. Arsenic concentrations range from 11.4 to 1660 μg L⁻¹ leaving 100% of the investigated waters above the provisional WHO guideline value of 10 μg L⁻¹. A strong positive correlation among As, F, and V in shallow groundwaters was found. The correlations among those trace elements and U, B and Mo have less significance. High pH (up to 9.2) and high bicarbonate (HCO₃) concentrations favour leaching from pyroclastic materials, including volcanic glass which is present to 20-25% in the loess-type aquifer sediments and yield higher trace element concentrations in groundwater from shallow aquifers compared to deep and artesian aquifers. The significant increase in minor and trace element concentrations and salinity in shallow aquifers is related to strong evaporation under semi-arid climatic conditions. Sorption of As and associated minor and trace elements (F, U, B, Mo and V) onto the surface of Fe-, Al- and Mn-oxides and oxi-hydroxides, restricts the mobilization of these elements into groundwater. Nevertheless, this does not hold in the case of the shallow unconfined groundwaters with high pH and high concentrations of potential competitors for adsorption sites (HCO₃, V, P, etc.). Under these geochemical conditions, desorption of the above mentioned anions and oxyanions occurs as a key process for As mobilization, resulting in an increase of minor and trace element concentrations. These geochemical processes that control the concentrations of dissolved As and other trace elements and which determine the groundwater quality especially in the shallow aquifers, are comparable to other areas with high As concentrations in groundwater of oxidizing aquifers and semi-arid or arid climate, which are found in many parts of the world, such as the western sectors of the USA, Mexico, northern Chile, Turkey, Mongolia, central and northern China, and central and northwestern Argentina.     

Testfeld Süd: Einrichtung der Testfeldinfrastruktur und Erkundung hydraulisch-hydrogeochemischer Parameter des Grundwasserleiters

A former gasification plant with a variety of organic contaminants within the aquifer serves as a field test site. Both contaminants in phase (contamination source) and dissolved (contaminant plume) can be detected. After extending the test site infrastructure various methods for the investigation of groundwater flow and transport have been applied and compared. The geometry of the aquifer is variable and a pronounced heterogeneity of the hydraulic conductivity can be observed. The influence of the sedimentary setting on the structure of the aquifer is shown. A relation between discrete grain size distributions and the petrographical composition of the aquifer material is established. Using this relation, the sorption properties of the aquifer can be derived. Following the first measurements, the observed differential spreading of pollutants within the contaminant plume is influenced by microbial degradation. Further field tests to investigate the biodegradation rates are proposed.     

Hydro-environmental changes and their influence on the subsurface environment in the context of urban development

The relationship between urban development and hydro-environmental change, particularly with regard to the subsurface environment is examined for three coastal cities affected by Asian monsoons (Tokyo and Osaka in Japan, and Bangkok in Thailand). Major differences in subsurface changes among these cities are closely related to city size, urban structure, and the timing, stage and extent of urbanization as well as the natural environment. The work shows that the urban development has not affected the Bangkok subsurface hydro-environment in the same way it has in Tokyo and Osaka. Three reasons for the difference account for this, (1) Bangkok's abundant annual rainfall, (2) Bangkok has the smallest ratio of impervious pavement surface area, meaning that surface water can more easily infiltrate underground., (3) the degree and extent of urbanization. Bangkok's subsurface hydro-environment has not been heavily affected because underground development has not yet reached deep subterranean areas.By researching yet more cities, at different stages of urbanization to that of Tokyo, Osaka and Bangkok, we plan to quantitatively examine urbanization and its influence on subsurface hydro-environments. This research will help limit damage to developing cities that are not yet experiencing subsurface failures but which are expected to confront these problems in the future.     

Identification of the origin of salinization in groundwater using minor ions (Lower Andarax,Southeast Spain)

The study of salinization of groundwater in the Detrital Aquifer of the Lower Andarax is highly complex due to the semiarid climate, the presence of evaporites, proximity to the sea and localized geothermal manifestations in the area. The salinization has been characterized by jointly studying the content of various minor ions (B, Br and Li) and a series of ionic relationships (B/Li, SO4/Cl, Na/Cl, Cl/B). The combined analysis of B and Li enabled the areas with a marked marine influence to be distinguished from those with an evaporite or geothermal influence. Lithium is directly related to water temperature whilst B content increases in more saline areas, since it is associated with the presence of evaporitic and/or marine influences. Bromine analysis enabled the identification of the principal processes that determine the salinity of the water along the coastal zone: the presence of Quaternary marine sediments and present-day marine intrusion. The brackish groundwaters that are related to old raised beaches showed a low Cl/Br ratio. Areas affected by marine intrusion had Cl/Br ratios similar to seawater and higher than in other areas along the coastal zone. At some points on the delta, a mixture of brackish water and recharge water was detected--the recharge water has a sulfate facies, which causes a drop in the Cl/Br ratio and changes the general character of the water in the coastal zone. The coastal zone contains silty-clay intercalations that favor processes of ion exchange, anthropogenic pollution also occurs and together these processes hamper the interpretation of all the processes.     

Clogging of a limestone fracture by stimulating groundwater microbes

Biological clogging is promoted in aquifers either to contain or to remediate groundwater. In this study, an apparatus able to detect small changes in hydraulic conductivity (K) was developed to measure the clogging of a single fracture in limestone, following microbial stimulation. The fracture had a 2.5 mm2 section and was 50 cm long. Prior to the inoculation of the limestone, the sequencing of representative clones from 16S rRNA genes isolated from groundwater, showed significant affiliation with Cytophaga spp., Arcobacter spp. and Rhizobium spp. These bacteria are known to secrete extracellular polymeric substances and form biofilms. When nutrients were added to the inoculated limestone, a decrease in K occurred after 8 days, reaching 0.8% of its initial value after 22 days (Kfi = 340 cm min-1). This study showed that a stimulation of indigenous microbes from groundwater effectively clogged a macrofracture in limestone, suggesting the potential application of biobarriers in fractured rock aquifers.