Concentrations of elements and metals in sediments of the southeastern Gulf of Mexico

. This paper deals with the extent of contamination in sediments of the southeast Gulf of Mexico. The concentration of elements (SiO2, Al2O3, Fe2O3, Na2O, MgO, CaO, and K2O) and heavy metals (Cu, Cd, Zn, Co, Pb, Ag, Cr, Ni, V, and Ba) were determined. The elemental composition of sediments is influenced by the Grijalva–Usumacinta–Terminos System at the east and the Tabasco lagoon system (El Carmen–La Machona) at the west coast of the study area. Concentrations of Ni, V, and Ba were anomalously high at some sites. Oil production activities in the vicinity of the sites may be responsible for the high values. Correlations of metal concentrations to elemental composition were performed. No significant relationships between metals and elements were found for most metals (p>0.05), suggesting that metals are not significantly associated with naturally occurring aluminosilicates, iron hydroxide, and calcium carbonate minerals of sediments. Other sources such as organic matter may be contributing to the total concentration of metals. The comparison of metal content in sediments of the southeast Gulf of Mexico with metals of the other areas of the Gulf of Mexico suggests that it is relatively contaminated with Cd, Pb, and Ni. The probable causes of contamination are briefly discussed.     

Hydrogeophysical approach for contamination assessment in NamSon landfill,Hanoi, Vietnam

Self potential (SP) and electrical resistivity tomography (ERT) methods are used together with the results of groundwater samples hydrogeochemical analysis to assess the impact of the water leak from the landfill garbage site at NamSon located in Northern Hanoi on causing pollution to the surrounding environment and affecting geological structure. Selected survey area covers an area of 180 × 300 m lying in the low land of the NamSon site with a slope ranging about 8 m in direction NW–SE. There are three geophysical measurements lines denoted as T1, T2 and T3. Processing 180 SP data points has allowed to draw maps of equipotential epoch in the two periods in 2015 and 2016. The maps show four zones of SP positive anomalies with maximum amplitudes of about +20 mV where the groundwater flow direction is downward and five zones of SP negative anomalies with minimum values in a range from ?180 to ?260 mV where the groundwater flow direction is upward. Resistivity values of the subsurface layers of soils and rocks have been aquired from 2D inverse model for measuring ERT in March 2015 and March 2016. The results of the ERT allowed to define the low resistivity in the range 15–20 Ωm related to leachate plume from NamSon landfill site. Results of the physico-chemical analysis of groundwater samples from the existing six boreholes show increases in concentration of the measured pollutant parameters indicating contamination of the groundwater as a result of solid waste leachate accumulation. This result is affirmative evidence for the survey results by geophysical technique. The rapid decrease in quality of groundwater over the last year is probably due to the influence of the leachate from the NamSon landfill site.     

Geoelectrical surveys of the Nanjido waste landfill in Seoul,Korea

Electrical surveys have routinely been taken to map and monitor groundwater contamination. In 1994-1996, various electrical surveys were applied to investigate contaminant distributions in the ground at the Nanjido landfill. The geophysical survey data were compared with other available information, particularly boring data. Interpretations of electrical survey data show low resistivity zones below 10 ohm-m which appear to be zones fully saturated with leachate. Annual variations of resistivity anomalies clearly indicate that resistivities and thicknesses of layers contaminated by leachate become lower and thicker in and around the Nanjido landfill during one year. In particular, mean thickness of saturated layers with leachate increased by about 3-6 m/year and the resistivity of bedrock decreased. It seems obvious that ground contamination by leachate is in progress. In the area northeast of the landfill, no evidence of bedrock contamination is indicated. Soundings made at one year intervals in this area do not show any evidence of further ground contamination by leachate. From these results, it appears that contamination of the weathered zone and bedrock is in progress mainly southwest of the Nanjido landfill.     

Geophysical imaging of municipal solid waste contaminant pathways

Surface electrical and electromagnetic surveys were conducted on top of a solid waste facility in Unguwan Dosa, Kaduna State, Northwest Nigeria. The aim of the geophysical survey was to detect vertical and subvertical fractures that may provide pathways for groundwater and contaminant transport. Results from the 2D electrical resistivity imaging showed vertical and subvertical contacts overlain by 6–10 m thick overburden. Quantitative interpretation of the VLF-EM data correlates well with the results of the 2D resistivity imaging delineating the vertical and subvertical contacts as good and weak conductors (fractures zones) with resistivity values of 40–220 and 300–420 Ω m, respectively. Azimuthal Schlumberger VES measurements yield apparent anisotropy values ranging from 1.01 to 1.47 for electrode spacings of 1–45 m with the highest value recorded at spacing of 2 m. However, azimuthal variations at large spacings (30–45 m) showed no fracture anisotropy due possibly to the array’s low sensitivity to anisotropy at these spacings. The result of the study showed that pollutants in the leachate can reach and contaminate the groundwater. Therefore, urgency for leachate treatment at this site is recommended to prevent contamination of groundwater.     

Occurrence of naphthalenesulfonates and their condensates with formaldehyde in a landfill leachate and their transport behavior in groundwater of the Upper Rhine Valley, Germany

. Naphthalenesulfonates and their condensation products with formaldehyde are manufactured in the chemical industry for broad application as tanning agents, dispersing agents, and as superplasticizers for concrete. With the disposal of waste they have found their way into the aquatic environment. Five monomeric naphthalenesulfonates and a group of dimeric sulfonated naphthalene-formaldehyde condensates (SNFC) were identified in the leachate and in groundwater observation wells downstream in the plume of the Karlsruhe-West landfill, situated in the Upper Rhine Valley in southwest Germany. For the main monomer of technical SNFC products, 2-naphthalenesulfonate (2-NS), the concentration in the leachate was 170 µg l^–1, which decreased to 9.5 µg l^–1 at a distance of about 300 m from the boundary of the landfill. In the Merdingen tracer test field, the transport of these compounds was studied under more controlled conditions in two tracer experiments with (1) two model compounds, and (2) a technical SNFC product and uranine as a reference tracer. In these experiments, the monomeric naphthalenesulfonates and the SNFC with n=2 behave as conservative tracers. Thus, the findings of the landfill study were supported by these results. Higher molecular SNFC were strongly retarded, which is attributed to adsorption to soil particles. The results of the second tracer experiment suggest a degradation of 2-NS and 2,6-naphthalenedisulfonate (2,6-NDS) after adaptation of the microorganisms in the groundwater aquifer as a consequence of the first tracer experiment.     

Investigation on potential groundwater impacts and influence of local hydrogeology on natural attenuation of leachate at a municipal landfill

The influence of local hydrogeology on natural attenuation of contaminants from landfill leachates in shallow aquifer underlying the active Olusosun landfill base in Lagos was investigated. In addition, the level of groundwater contamination in the vicinity of the landfill and of leachate migration pattern in groundwater down gradient of the landfill base was equally assessed. Landfill leachate and groundwater samples were collected and analyzed and characterized. Physico-chemical analyses of sampled water followed standard analytical methods. Analytical results showed a measurable impact of leachate outflows on groundwater quality. Elevated levels of anions: nitrate, chloride and sulphate in the groundwater body and heavy metals: Cr₃. Cd and Cu, were detected at measurable levels in groundwater down gradient of the landfill location without any particular attenuation pattern. The migration pattern and dispersion of leachates down gradient, 750 m away from the landfill location are irregular and difficult to predict as depicted by levels of contaminants present in groundwater. The study highlighted the importance of soil stratigraphy beneath the landfill base as an important factor in the natural attenuation of leachate constituents in the groundwater body.     

Combined analyses of chemometrics and kriging for identifying groundwater contamination sources and origins at the Masan coastal area in Korea

Hydrogeochemical analyses including the basic statistics of chemical components, Piper??s trilinear diagram, and Mazor??s compositional bivariate diagram revealed that the main source and origin of groundwater contamination was seawater intrusion in the study area. However, the other sources and origins of groundwater contamination could be found by the combined analyses of chemometrics and kriging. Cluster analysis was helpful for the classification on the basis of the contamination characteristics of groundwater quality; however, it was not sufficient for the apportionment of groundwater contamination sources. Factor analysis (FA) determined three factors with 81.07% in total variance: Factor 1 for seawater contamination, Factor 2 for nitrate contamination, and Factor 3 for iron contamination. Factor analysis determined the sources of groundwater contamination; however, it could not discover the origins of contaminants except Factor 1. In backward stepwise mode, discriminant analysis decreased the number of parameters from 18 to 6 in discriminating the contaminant type with 96.2% correctness. TDS, Ca, NO₃, Mn, Fe, and Br were the most significant parameters for the discrimination of contaminants. Kriging analysis was very useful for the understanding of correlation and similarity between contaminants and factors of FA, and for the investigation of contaminant origins. It also showed that the similarity between factor scores and contaminant concentrations was proportional to the magnitudes of factor loadings for contaminants. This study represented that the combined analyses of chemometrics and kriging were very indispensable to the identification of groundwater contamination sources and origins, as well as for the spatial classification and assessment of groundwater quality.     

Reducing leachable petroleum hydrocarbon concentration in weathered fuel oil contaminated soil by chemical oxidation with hydrogen peroxide

Number 6 fuel oil is one of the most used energy sources for electricity generation. However, leaks can contaminate soil and also groundwater due to leaching. At old sites, the oil may have low toxicity but still contaminate groundwater with foul-tasting compounds even at low concentrations. The purpose of this study was to evaluate the feasibility of applying H₂O₂ to reduce the leaching potential of a fuel oil contaminated soil. A silt-loam soil was collected from a contaminated thermal-electric plant with a hydrocarbon concentration of 3.2% in soil producing 4.3 mg/l in leachate. Hydrogen peroxide was applied (0.1, 0.2, 0.3, 0.6, 1.2% dry weight basis), and petroleum hydrocarbons were measured in soil and leachate pre- and post-treatment (72 h). At first, the soil and leachate concentrations diminished linearly (24.4 and 27.3% in soil and leachate, respectively). This was followed by a phase in which the concentration in leachate diminished greatly (75.8%) although the concentration in soil was reduced only moderately (15.1%). Overall, hydrocarbons in leachates were reduced 82.4% even though concentrations in soil were only reduced 35.8%. Correlation analysis showed that at only 1.0% w/w H₂O₂ a concentration of petroleum hydrocarbons in leachate safe for human consumption (≤ 1 mg/l) could be obtained even with a final hydrocarbon concentration in soil > 2%. Thus, this study presents an alternative strategy for remediation of fuel oil contaminated soils in urban environments that protects water sources by focusing on contamination in leachates, without spending extra financial resources to reduce the hydrocarbon concentration in low-toxicity soil.     

Integrated use of hydrochemistry and resistivity methods in groundwater contamination caused by a recently closed solid waste site

 In order to investigate the groundwater contamination by solid waste disposal using both hydrochemical and geophysical methods, the Halkalı (I˙stanbul) solid waste disposal site which was closed in 1994 was investigated. The disposal site lies on a ridge between two valleys filled with alluvium. A total of six boreholes were drilled on two lines across the Menekşe valley adjacent to the Halkalı site. Groundwater samples collected from these boreholes were analyzed for various contaminant parameters. The results indicate that TDS and chloride concentrations decrease horizontally away from the waste site whereas they increase with depth. Electrical soundings carried out at 12 locations yielded high resistivity values at the upstream part of Menekşe valley while lower values were obtained from the locations near the leachate seepage points. Received: 11 November 1997 · Accepted: 23 February 1998     

Localization of water bearing fractured zones in a hard rock area using integrated geophysical techniques in Andhra Pradesh,India

Knowledge of the existence of fracture zones, their extent, intensity and direction is very useful for assessing groundwater in hardrock regions and in this context geophysical methods are widely accepted as a powerful means of study. In the modern era of exploration, application of the Resistivity Imaging technique gives a new opportunity for groundwater study in hardrock regions. Exploration surveys were conducted at one of the important sites in Maheshwaram watershed, Andhra Pradesh, India with a multielectrode resistivity imaging system. To reduce the ambiguity of geophysical interpretation some complementary geophysical studies like ground Magnetic and VLF were also carried out.A number of 2D resistivity images were prepared in a grid pattern, which clearly show the weathered and fractured zones in different parts of the study area. With the help of all 2D profiles a quasi-3D image has been created, which indicates the orientation and extension of the fracture zone in a horizontal as well as vertical direction in the study area. Strong agreement exists among the anomalies identified using the ground magnetic, VLF and resistivity imaging methods. The litholog data available in the study area also helps to interpret geophysical results to find a potential groundwater bearing zone in that area.     

Interrelationship between geochemical elements of sediment and groundwater at Samrak Park Delta of Nakdong River Basin in Korea: multivariate statistical analyses and artificial neural network approaches

This research was conducted at Samrak Park Delta of Nakdong River Basin in Busan Metropolitan City, Korea. The main objective of this study was to evaluate the interrelationship of geochemical elements in sediments and groundwater through multivariate statistical analyses and a multilayer perceptron artificial neural network model. The mean concentrations of chemical elements were Si (46%), Fe (16.9%), Al (15.7%), K (7.5%) and Ca (4.5%) in sediments, and Na (8650 mg/L), Mg (999 mg/L), Ca (432 mg/L), K (293 mg/L) and Cl (17,640 mg/L) in groundwater, respectively. The principal component analysis produced 3 kinds of factors with the variances of 63.37, 27.02 and 9.62%, respectively. It is suggested that the chemical components of sediments and groundwater were mainly originated from source rocks and seawater intrusion, with the minor impacts of irrigation and industry. Cluster analysis also showed that chemical elements were mainly controlled by the natural geogenic sources and seawater intrusion. Multilayer perceptron of artificial neural network (ANN) presented the good interrelationship between sediment and groundwater. The determination coefficients (R ²) between ANN predicted values and observed values in groundwater showed the high values of 0.61–0.97 except Mg, Mn and Sr. It is revealed that the chemical components of sediment and groundwater were derived from local geological origin and from the minor impact of anthropogenic sources. Multivariate analyses and ANN contributed to the identification of the mutual relationship between the geochemical elements of sediment and those of groundwater.     

Role of some salient geophysical, geochemical, and hydrogeological parameters in the exploration of fresh groundwater in a brackish terrain

. Geophysical, geochemical, and hydrogeological parameters, for example longitudinal unit conductance (S), transverse unit resistance (T), total dissolved solids (TDS) and thickness of the weathered zone (Wz), have been compared for 25 sites of Navalgund taluk in Dharwar District of Karnataka State, India. Interrelation among these parameters has been analyzed quantitatively by the standard statistical technique leading to a suitable mathematical model. The contrasting geophysical, geochemical, and hydrogeological characteristics of the fresh water pockets in the regionally brackish aquifers are compared and illustrated. The study explains the significant bearing of these parameters on exploration, development, and exploitation of fresh groundwater sources in the areas affected by the occurrence of a brackish water aquifer. The importance of such a comparison in raising the confidence to identify a fresh groundwater aquifer in the brackish terrain by quantitative interpretation of resistivity data has been demonstrated.     

Applying spatial regression to evaluate risk factors for microbiological contamination of urban groundwater sources in Juba,South Sudan

This study developed methodology for statistically assessing groundwater contamination mechanisms. It focused on microbial water pollution in low-income regions. Risk factors for faecal contamination of groundwater-fed drinking-water sources were evaluated in a case study in Juba, South Sudan. The study was based on counts of thermotolerant coliforms in water samples from 129 sources, collected by the humanitarian aid organisation Médecins Sans Frontières in 2010. The factors included hydrogeological settings, land use and socio-economic characteristics. The results showed that the residuals of a conventional probit regression model had a significant positive spatial autocorrelation (Moran’s I?=?3.05, I-stat?=?9.28); therefore, a spatial model was developed that had better goodness-of-fit to the observations. The most significant factor in this model (p-value 0.005) was the distance from a water source to the nearest Tukul area, an area with informal settlements that lack sanitation services. It is thus recommended that future remediation and monitoring efforts in the city be concentrated in such low-income regions. The spatial model differed from the conventional approach: in contrast with the latter case, lowland topography was not significant at the 5% level, as the p-value was 0.074 in the spatial model and 0.040 in the traditional model. This study showed that statistical risk-factor assessments of groundwater contamination need to consider spatial interactions when the water sources are located close to each other. Future studies might further investigate the cut-off distance that reflects spatial autocorrelation. Particularly, these results advise research on urban groundwater quality.     

GIS-based colour composites and overlays to delineate heavy metal contamination zones in the shallow alluvial aquifers, Ankaleshwar industrial estate, south Gujarat, India

In an attempt to delineate heavy metal contamination precincts and to evaluate the extent and degree of toxic levels, besides their possible sources, 38 water samples from Ankaleshwar Industrial Estate, south Gujarat, India were analyzed. By clutching geochemical analyses and GIS-based colour composites areas depicting anomalously high concentration of heavy metals (Mo, Zn, Pb, Ni, Co, Cd, etc.) in the groundwater were revealed. The multicomponent overlays in grey-scale facilitated in identifying situates of heavy metal ‘hot spots’, and lateral protuberances of the contamination plume around defile stretch of the main stream Amla Khadi flowing through the area. The multiple pollution plumes emerging from other parts of the area further coincide with effluent laden streams and small channels indicating industrial establishments as major sources of groundwater contamination. Influent nature of the streams, accelerated infiltration process, high mass influx and shallow groundwater table are the factors conducive for easy access of heavy metals to the phreatic aquifers affecting over 20 km² area. On the basis of P/U ratios (concentration of metals in polluted water to unpolluted water), geogenic and anthropogenic sources have been identified. Very high levels of technogenic elements present in the ground water raise concerns about possible migration into food crops, as the area is an important horticultural locale and is highly cultivated.     

Assessment of the leachate movement in a sealed landfill using geophysical methods

This paper describes a case study concerning the use of integrated geophysical methods applied to environmental assessment. The study is focused on an old municipal solid waste sealed landfill site, located in Gaeiras, Central Portugal. The problem is related with leachate overproduction in this domestic and industrial waste landfill that became an environmental problem with urgent assessment, so that a solution could be planned. Due to the lack of accurate information regarding the shape, history and development of the landfill, the use of a set of classical geophysical methods was the option, since they are non-invasive and non-destructive. The available area was small, almost restricted to the landfill area. To conduct this assessment, electromagnetic RF-EM and Geonics EM34, spontaneous potential (SP), vertical electrical soundings (VES) and magnetic prospecting surveys were planned to understand the various problems that could be related with the leachate overproduction. The joint use of these classical geophysical methods was targeted to investigate bedrock depth and structure (RF-EM, EM34 and VES), waste and leachate characteristics (EM34 and magnetics) and groundwater flow (SP) in the landfill. Geophysical results were correlated with hydrogeological information, integrated and interpreted, using geographic information system tools. The results obtained were important to understand the geological mechanisms that are responsible for leachate overproduction and to suggest remedial measures.     

Aquifer vulnerability assessment using the DRASTIC model at Russeifa landfill,northeast Jordan

Groundwater is inherently susceptible to contamination from anthropogenic activities and remediation is very difficult and expensive. Prevention of contamination is hence critical in effective groundwater management. In this paper an attempt has been made to assess aquifer vulnerability at the Russeifa solid waste landfill. This disposal site is placed at the most important aquifer in Jordan, which is known as Amman-Wadi Sir (B2/A7). The daily-generated leachate within the landfill is about 160 m³/day and there is no system for collecting and treating this leachate. Therefore, the leachate infiltrates to groundwater and degrades the quality of the groundwater. The area is strongly vulnerable to pollution due to the presence of intensive agricultural activity, the solid waste disposal site and industries. Increasing groundwater demand makes the protection of the aquifer from pollution crucial. Physical and hydrogeological characteristics make the aquifer susceptible to pollution. The vulnerability of groundwater to contamination in the study area was quantified using the DRASTIC model. The DRASTIC model uses the following seven parameters: depth to water, recharge, aquifer media, soil media, topography, impact on vadose zone and hydraulic conductivity. The water level data were measured in the observation wells within the disposal site. The recharge is derived based on precipitation, land use and soil characteristics. The aquifer media was obtained from a geological map of the area. The topography is obtained from the Natural Resources Authority of Jordan, 1:50,000 scale topographic map. The impact on the vadose zone is defined by the soil permeability and depth to water. The hydraulic conductivity was obtained from the field pumping tests. The calculated DRASTIC index number indicates a moderate pollution potential for the study area.     

Impact of pit-toilet leachate on groundwater chemistry and role of vadose zone in removal of nitrate and E. coli pollutants in Kolar District, Karnataka, India

Assessment of chemistry of groundwater infiltrated by pit-toilet leachate and contaminant removal by vadose zone form the focus of this study. The study area is Mulbagal Town in Karnataka State, India. Groundwater level measurements and estimation of unsaturated permeability indicated that the leachate recharged the groundwater inside the town at the rate of 1 m/day. The average nitrate concentration of groundwater inside the town (148 mg/L) was three times larger than the permissible limit (45 mg/L), while the average nitrate concentration of groundwater outside the town (30 mg/L) was below the permissible limit. The groundwater inside the town exhibited E. coli contamination, while groundwater outside the town was free of pathogen contamination. Infiltration of alkalis (Na⁺, K⁺) and strong acids (Cl^?, SO₄ ^2?) caused the mixed Ca–Mg–Cl type (60 %) and Na–Cl type (28 %) facies to predominate groundwater inside the town, while, Ca–HCO₃ (35 %), mixed Ca–Mg–Cl type (35 %) and mixed Ca–Na–HCO₃ type (28 %) facies predominated groundwater outside/periphery of town. Reductions in E. coli and nitrate concentrations with vadose zone thickness indicated its participation in contaminant removal. A 4-m thickness of unsaturated sand + soft, disintegrated weathered rock deposit facilitates the removal of 1 log of E. coli pathogen. The anoxic conditions prevailing in the deeper layers of the vadose zone (>19 m thickness) favor denitrification resulting in lower nitrate concentrations (28–96 mg/L) in deeper water tables (located at depths of ?29 to ?39 m).     

Analysis of the distribution of inorganic constituents in a landfill leachate-contaminated aquifer: Astrolabe Park,Sydney, Australia

An investigation was conducted at Astrolabe Park landfill, a decommissioned municipal landfill in Sydney, Australia, to assess the physical and chemical processes affecting the distribution of inorganic constituents in the leachate plume. The plume is migrating from the landfill towards a groundwater-fed pond into which leachate-impacted groundwater discharges. Borehole geophysical logging and depth-discrete groundwater sampling were used to delineate the distribution of the leachate plume along two groundwater flow paths between the landfill and the shore of the pond. Borehole geophysical logs indicate a strong correlation between bulk and fluid electrical conductivity (EC) values, and help to identify small-scale heterogeneities that comprise a major constraint on contaminant transport within the aquifer. Variations in the distribution of several indicator parameters (EC, HCO₃^–, pH, Eh, NH₄⁺/NO₃^–, S^2–/SO₄^2–) are used to assess the dominant processes affecting contaminant distribution along the flow path, including mixing of fresh and contaminated groundwater, oxidation/reduction reactions and ion exchange.     

Environmental impact of an urban landfill on a coastal aquifer (El Jadida, Morocco)

The El Jadida landfill is one among many uncontrolled dumping sites in Morocco with no bottom liner. About 150 tons/day of solid wastes from mixed urban and industrial origins are placed directly on the ground. At the site of this landfill, the groundwaters circulate deeply (10–15 m) in the Cenomanian rock (calcareous–marl), which is characterised by an important permeability from cracks. The soil is sand–clay characterized by a weak coefficient of retention.The phreatic water ascends to the bottom of three quarries, which are located within the landfill. These circumstances, along with the lack of a leachate collection system, worsen the risks for a potential deterioration of the aquifer.To evaluate groundwater pollution due to this urban landfill, piezometric level and geochemical analyses have been monitored since 1999 on 60 wells. The landfill leachate has been collected from the three quarries that are located within the landfill. The average results of geochemical analyses show an important polluant charge vehiculed by landfill leachate (chloride = 5680 mg l⁻¹, chemical oxygen demand = 1000 mg l⁻¹, iron = 23 000 μg l⁻¹). They show also an important qualitative degradation of the groundwater, especially in the parts situated in the down gradient area and in direct proximity to the landfill. In these polluted zones, we have observed the following values: higher than 4.5 mS cm⁻¹ in electric conductivity, 1620 and 1000 mg l⁻¹ respectively in chlorides and sulfate (), 15–25 μg l⁻¹ in cadmium, and 60–100 μg l⁻¹ in chromium. These concentrations widely exceed the standard values for potable water.Several determining factors in the evolution of groundwater contamination have been highlighted, such as (1) depth of the water table, (2) permeability of soil and unsaturated zone, (3) effective infiltration, (4) humidity and (5) absence of a system for leachate drainage. So, to reduce the pollution risks of the groundwater, it is necessary to set a system of collection, drainage and treatment of landfill leachates and to emplace an impermeable surface at the site of landfill, in order to limit the infiltration of leachate.     

The use of soil mercury and radon gas surveys to assist the detection of concealed faults in Fuzhou City, China

Soil gas approaches have been proven useful for detecting buried faults in field survey. How about their applicability in urban area? A trial soil gas survey has been conducted in an attempt to evaluate this in Fuzhou City, Southeastern China. The detection was performed by measuring the adsorbed mercury, free mercury and radon gases in soil in the sites such as crop soil, refilled soil and those with shallow groundwater levels. The resulting distributions show that anomalous concentrations of soil gases over faults are generally two to four times as much as those in the surrounding areas. The locations of peak values of absorbed and free mercury could possibly be applied to assist to determine the trend of faults. The background values of free mercury seems to be more stable and the anomalous zones narrower than those of radon gas, therefore, the free mercury method seems to be good for detection at this area, especially in those sites with shallow groundwater levels. The false gas anomalies may occur in such a site as refilled with external soil, refilled pond and abandoned construction bases.