The use of X-ray fluorescence to detect lead contamination of carpeted surfaces

The recognition of the hazards to young children of low-level lead intoxication and the widespread distribution of lead in the urban environment have resulted in massive federal, state, and local lead awareness and abatement programs. Two of the most significant exposure routes of lead to young children are the soils and dusts found within the child's home. Most state and federal lead abatement programs deal with lead-based paint contamination but often do not address the issue of soft-surface contamination, such as that of carpets, furniture, and draperies. Carpets can be a reservoir of contaminated soils and dusts; currently, there exists no standard method to test carpeted surfaces for lead contamination. This paper describes a study that uses X-ray fluorescence (XRF) to test carpeted surfaces for lead contamination. XRF technology is the standard technology used in lead-based paint testing and is known to be an accurate technique to test for lead in soils. This study uses a controlled laboratory atmosphere to evaluate this technology; the objectives are to determine: (1) a lower limit of detection for the instrument; and (2) whether soil loading levels can be differentiated by XRF using trace elements also present in the soil. Results indicate that XRF can easily differentiate soil loading levels (g soil/m² carpet). The lower limit of detection of soil lead concentration on the carpet is a function of both soil lead concentration and soil loading; therefore, lead loading (mg Pb/m²) is a better indicator of detection limit than soil lead concentration. Lead loading detection levels from 108–258 mg Pb/m² were obtained, as compared to a level of 10 000 mg/m² (1 mg/cm²) for lead on painted surfaces as required by theLead-Based Paint Poisoning Prevention Act. XRF technology has the potential to be a fast, inexpensive screening technique for the evaluation of lead contamination on carpeted surfaces.     

Survey and evaluation of contaminants in earthworms and in soils derived from dredged material at confined disposal facilities in the Great Lakes Region

Soils derived from dredged material were collected, together with earthworms from nine confined disposal facilities located in the Great Lakes Region. These samples were analyzed for 18 elements, 11 organochlorine pesticides, PCBs, and 24 polycyclic aromatic hydrocarbons. The concentrations detected in earthworms were evaluated in terms of their potential hazard to wildlife, which for the sake of the evaluation were assumed to prey entirely either on earthworms or on other soil invertebrates having similar concentrations. The soil concentrations (dry wt.) of the contaminants of greatest concern were <1.9 to 32 ppm Cd, <0.053 to 0.94 ppm Hg, 4.6 to 550 ppm Pb, and <0.1 to 1.0 ppm PCBs. The concentrations in earthworms (dry wt., ingested soil included) were as high as 91 ppm Cd, 1.6 ppm Hg, 200 ppm Pb, and 1.8 ppm PCBs. Based on laboratory toxicity studies of relatively sensitive species, and on concentration factors calculated from the earthworm and soil data, we estimated that lethal or serious sublethal effects on wildlife might be expected at concentrations of 10 ppm Cd, 3 ppm Hg, 670 ppm Pb, and 1.7 ppm PCBs in alkaline surface soils derived from dredged material. Concentrations of polycyclic aromatic hydrocarbons in earthworms were well below those in soil.     

Simulation of the migration and transformation of petroleum pollutants in the soils of the Loess plateau: a case study in the Maling oil field of northwestern China

We developed a coupled water–oil simulation model to simulate the migration and transformation of petroleum-derived contaminants in the soil of the Xifeng oil field. To do so, we used the HYDRUS-2D model, which simulates the diffusion, adsorption or desorption, and microbial degradation of petroleum-derived hydrocarbons in the soil–water system. The saturated soil hydraulic conductivity of petroleum-derived pollutants was 0.05 cm?day^?1, which is about 1 to 2 % of the soil moisture permeability coefficient. Our numerical simulation results show that spilled crude oil was mainly concentrated in the surface horizons of the soil. The organic pollutant concentration tended to be highest nearest to the pollution source. The pollutant migration was generally concentrated within the top 20 to 30 cm of the soil, with the maximum concentration in the top 5 cm of the soil. With passing time, the pollutant accumulation increased and the adsorption and degradation functions reached a dynamic balance with the input rate at depths greater than 30 cm below the soil surface. The oil-derived pollutants totaled 50 to 100 mg?kg^?1 under the dynamic balance condition, which occurred after 20 to 30 years. The petroleum-derived pollutant concentration in the loess soil was inversely correlated with the horizontal distance from the oil well, and the concentration decreased greatly at a distance greater than 40 m from the well.     

Competitive Retention of Lead and Cadmium on an Agricultural Soil

Lead and cadmium contamination of an agricultural soil has been studied using batch and column experiments. Thermodynamics of theretention phenomena may be represented by a Langmuir isotherm foran aqueous metal concentration up to 100 mg L^-1. First order kinetics with respect to the solid phase yield good predictabilityfor both batch and column experiments. Kinetics and thermodynamics of lead retention predominate over those ofcadmium. As a consequence, lead is preferentially retainedand can even displace sorbed cadmium. In the event of anspill involving both metals, cadmium would move further inthe soil and its aqueous concentration downstream could beeven higher than that of the influent solution, increasingpotential risks. A two-region model has been used to fit all the experimental results. Satisfactory predictions for column experiments are obtained with parameters which are consistent with those obtained for the batch experiments, for which sorption is described by a Langmuir isotherm including competitive retention.     

Assessment of phenol infiltration resilience in soil media by HYDRUS-1D transport model for a waste discharge site

The movement of contaminants through soil imparts a variety of geo-environmental problem inclusive of lithospheric pollution. Near-surface aquifers are often vulnerable to contamination from surface source if overlying soil possesses poor resilience or contaminant attenuation capacity. The prediction of contaminant transport through soil is urged to protect groundwater from sources of pollutants. Using field simulation through column experiments and mathematical modeling like HYDRUS-1D, assessment of soil resilience and movement of contaminants through the subsurface to reach aquifers can be predicted. An outfall site of effluents of a coke oven plant comprising of alarming concentration of phenol (4–12.2 mg/L) have been considered for studying groundwater condition and quality, in situ soil characterization, and effluent characterization. Hydrogeological feature suggests the presence of near-surface aquifers at the effluent discharge site. Analysis of groundwater of nearby locality reveals the phenol concentration (0.11–0.75 mg/L) exceeded the prescribed limit of WHO specification (0.002 mg/L). The in situ soil, used in column experiment, possess higher saturated hydraulic conductivity (K _S ?=?5.25?×?10^?4 cm/s). The soil containing 47 % silt, 11 % clay, and 1.54 % organic carbon content was found to be a poor absorber of phenol (24 mg/kg). The linear phenol adsorption isotherm model showed the best fit (R ²?=?0.977, RMSE?=?1.057) to the test results. Column experiments revealed that the phenol removal percent and the length of the mass transfer zone increased with increasing bed heights. The overall phenol adsorption efficiency was found to be 42–49 %. Breakthrough curves (BTCs) predicted by HYDRUS-1D model appears to be close fitting with the BTCs derived from the column experiments. The phenol BTC predicted by the HYDRUS-1D model for 1.2 m depth subsurface soil, i.e., up to the depth of groundwater in the study area, showed that the exhaustion point was reached within 12 days of elapsed time. This clearly demonstrated poor attenuation capacity of the soil to retard migration of phenol to the groundwater from the surface outfall site. Suitable liner, based on these data, may be designed to inhibit subsurface transport of phenol and thereby to protect precious groundwater from contamination.     

Further studies using X-ray fluorescence to sample lead contaminated carpeted surfaces

The sampling of carpeted surfaces to test for lead contamination primarily focuses upon vacuum techniques. Vacuum sampling techniques, however, require time-consuming, expensive laboratory analysis of the dusts obtained and are unable to determine total lead load on the carpet. X-ray fluorescence (XRF) analysis is an on-site, inexpensive, non-destructive, quick technique for predicting metals levels in a variety of media, such as water, soil, filter paper and painted surfaces. A 1992 study of the feasibility of XRF to analyze for lead and soil loadings on carpeted surfaces indicated that XRF can detect lead at a low enough level to warrant further study. This paper expands this earlier study and developes lead and soil loading calibration curves for three different carpet types based upon XRF lead L-beta peak areas and XRF iron and barium K-alpha peak and background areas. Results indicate that variation in the data can be reduced through modifications of the XRF analysis technique, thus reducing the statistically determined detection level, and that carpet type does affect the calibration. Detection levels of approximately 70 mg/m² for lead and 5 g/m² for soil were obtained. Overall, good agreement was found between results of this study and the earlier one. XRF shows excellent potential for quantitative analysis of lead on carpeted surfaces.     

Determination of lead, cadmium and copper in roadside soil and plants in Elazig, Turkey

The concentrations of lead, cadmium and copper in roadside soil and plants in Elazig, Turkey were investigated. Soil samples were collected at distances of 0, 25 and 50 m from the roadside. The concentrations of lead, cadmium and copper were measured by Flame Atomic Absorption Spectrophotometry (FAAS). A slotted tube atom trap (STAT) was used to increase the sensitivity of lead and cadmium in FAAS. Lead concentrations in soil samples varied from 1.3 to 45 mg kg⁻¹ while mean lead levels in plants ranged from120 ng g⁻¹ for grape in point-4 to 866 ng g⁻¹ for apple leaves in point-2. Lead analyses showed that there was a considerable contamination in both soil and plants affected from traffic intensity. Overall level of Cd in soil samples lies between 78 and 527 ng/g while cadmium concentration in different vegetations varied in the range of 0.8–98.0 ng g⁻¹. Concentrations of copper in soil and plant samples were found in the range of 11.1–27.9 mg kg⁻¹ for soil and 0.8–5.6 mg kg⁻¹ for plants. Standard reference material (SRM) was used to find the accuracy of the results of soil analyses.     

Spatial variability of fallout-137Cs in the soil of a cultivated field

To obtain information on the spatial variability of fallout ¹³⁷Cs in the soil of a small area, the activity concentration of this radionuclide was determined in 100 soil samples, taken along the two diagonals of a cultivated field (150×100 m). The results show that the spatial distribution of ¹³⁷Cs in this field is at random. The frequency distribution of the values is skewed to the right, but not log-normal. The median activity concentration observed was 7.45 Bq kg^-1 dry soil, the values ranging from 4.8–15 Bq kg^-1. The spatial variability, as characterized by the relative decile deviation was 26%. If one tolerates for the establishment of baselines of global fallout ¹³⁷Cs in the soil an error in the mean activity concentration of 10% (20%) at the 95% confidence level, the minimum number of soil samples to be taken can be estimated as 14 (4). The total deposition of ¹³⁷Cs on the soil surface by fallout was determined as 3.3±0.4 kBq m^-2.     

Kriging for estimating spatial pattern of contaminants: Potential and problems

This paper discusses and illustrates the use of kriging techniques for estimating the spatial pattern of contaminants in environmental media, particularly soil. The assumptions underlying kriging are reviewed as are some advantages and disadvantages of the method. Lognormal kriging (kriging applied to logarithmic-transformed data) is illustrated using a set of radionuclide soil concentrations at a nuclear testing area on the Nevada Test Site. This example shows how lognormal kriging can be used to estimate average concentrations at points or for blocks of land, concentration contours over space, confidence bands about these contours, and radionuclide inventory in soil. The validity of kriging estimates depends on the accurate estimation and modeling of the spatial correlation structure of the phenomenon. Accuracy is especially important when lognormal kriging is used and estimates of means and their standard deviations are required in the original, untransformed scale. This paper illustrates the bias that can result when a changing correlation structure over space is ignored.Operated for the U.S. Department of Energy by Battelle Memorial InstituteWork supported by Nevada Applied Ecology Group, U.S. Department of Energy, Nevada Operations Office under Contract DE-AC06-76RLO 1830.     

The use of silica gel modified with allyl 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate for selective separation and preconcentration of lead in environmental samples

The aim of the present work is the assessment of a new sorbent, prepared using silica gel coated with a pyrimidine derivative (allyl 6-methyl-4-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate), for extraction and preconcentration trace amount of lead from different samples prior to determination by flame atomic absorption spectrometry. Common coexisting ions did not interfere with the separation and determination of lead at pH?6, so that lead ion completely adsorbed on the column. The limit of detection based on three times the standard deviation of the blank was found to be 0.53 ng?mL^?1 in original solution. Obtained sorption capacity for 1 g sorbent was 5.0 mg Pb. The linearity was maintained in the concentration range of 0.1–30.0 ng?mL^?1 for the concentrated solution. Eight replicate determinations of 2.0 μg?mL^?1 of lead in the final solution gave relative standard deviation of ±2.6 %. The proposed method was successfully applied to the determination trace amounts of lead in the environmental samples such as carrot, rice, zardchoobe, and real water samples.     

农药企业搬迁土地挥发性有机物风险评价

对常州某农药生产场地土壤中挥发性有机物(VOCs)污染状况以及健康风险和生态风险进行了调查评价。结果表明,该场地土壤中挥发性有机物污染以苯系物和卤代烃为主。苯系物质量浓度为0~56.6 mg/kg,卤代烃质量浓度为0~1.14 mg/kg。健康风险评价结果均在可接受范围内,而生态风险评价显示生产车间内的土壤VOCs生态风险较大,存在着对生物的危害。     

挥发性有机物污染土壤样品采样方法比较

以苯系物污染土壤样品的采集为例,比较了4种不同采样方法导致样品检测结果的差异。其中,方法 1将样品装填至广口瓶内并压实密封,方法2采用非扰动采样器采集10 g样品后转移至加有10 mL甲醇保护剂的Vial瓶中密封,方法 3用非扰动采样器采集10 g样品后直接将其密封于采样器内,方法 4用Encore采样器采样后将其密封于采样器内。结果表明,方法 2采集样品的检出率最高,其余3种方法的差异不明显,方法 2采集样品的检出结果 71%以上都大于其余3种方法。而且,对于挥发性较强的苯与甲苯,以方法 2采集的样品91%以上都大于其余3种方法,最大及平均检出浓度高出2~3个数量级。5种不同土质样品检测结果表明,对于有机质含量较低的细砂,方法2的最高及平均检出浓度均高于其余3种方法 1~3个数量级,差异随土壤有机质含量的升高而降低。可见,对于苯系物及挥发性强于苯系物的其他挥发性有机物污染土壤样品的采集,方法 2效果最优,可指定为VOCs污染场地土壤样品的采样方法。     

CDOM fluorescence as a proxy of DOC concentration in natural waters: a comparison of four contrasting tropical systems

Chromophoric dissolved organic matter (CDOM) fluorescence or absorption is often proposed as a rapid alternative to chemical methods for the estimation of bulk dissolved organic carbon (DOC) concentration in natural waters. However, the robustness of this method across a wide range of systems remains to be shown. We measured CDOM fluorescence and DOC concentration in four tropical freshwater and coastal environments (estuary and coastal, tropical shallow lakes, water from the freshwater lens of two small islands, and soil leachates). We found that although this method can provide an estimation of DOC concentration in sites with low variability in DOC and CDOM sources in systems where the variability of DOC and CDOM sources are high, this method should not be used as it will lead to errors in the estimation of the bulk DOC concentration.     

Estimation Of Selenium Concentration In Shallow Groundwater In Alluvial Fan Area In Tsukui, Central Japan

Total selenium (Se) and water-soluble Se in soil, and Se in a shallow groundwater were hydrogeochemically researched in an alluvial fan area in Tsukui, Central Japan. The water-soluble Se was estimated at average level of 2.6 ± 1.2μg Se kg⁻¹ dry soil (± SD, n = 25), showing less than 1% of the total Se (349–508μg Se kg⁻¹ dry soil) in soil. The monthly Se concentration in groundwater was average 2.2μg,L⁻¹, ranging 1.6–2.4μg,L⁻¹ during 2001–2003. The Se in groundwater significantly decreased with increasing groundwater level after rainfall. This result indicated that Se-bearing water percolated with relatively low Se concentration through the soil layer. According to our prediction model of linear regression curve on the observation data, Se concentration in the groundwater was estimated to be increasing with the very low rate of 4.35 × 10⁻³μg Se L⁻¹,yr⁻¹. The hydrogeochemical research and the result of the prediction model showed that any explosive increase of Se will hardly occur in this groundwater without an anthropogenic Se contamination.     

Urban stormwater harvesting and reuse: a probe into the chemical, toxicology and microbiological contaminants in water quality

Stormwater is one of the last major untapped urban water resources that can be exploited as an alternative water source in Australia. The information in the current Australian Guidelines for Water Recycling relating to stormwater harvesting and reuse only emphasises on a limited number of stormwater quality parameters. In order to supply stormwater as a source for higher value end-uses, a more comprehensive assessment on the potential public health risks has to be undertaken. Owing to the stochastic variations in rainfall, catchment hydrology and also the types of non-point pollution sources that can provide contaminants relating to different anthropogenic activities and catchment land uses, the characterisation of public health risks in stormwater is complex, tedious and not always possible through the conventional detection and analytical methods. In this study, a holistic approach was undertaken to assess the potential public health risks in urban stormwater samples from a medium-density residential catchment. A combined chemical–toxicological assessment was used to characterise the potential health risks arising from chemical contaminants, while a combination of standard culture methods and quantitative polymerase chain reaction (qPCR) methods was used for detection and quantification of faecal indicator bacteria (FIB) and pathogens in urban stormwater. Results showed that the concentration of chemical contaminants and associated toxicity were relatively low when benchmarked against other alternative water sources such as recycled wastewater. However, the concentrations of heavy metals particularly cadmium and lead have exceeded the Australian guideline values, indicating potential public health risks. Also, high numbers of FIB were detected in urban stormwater samples obtained from wet weather events. In addition, qPCR detection of human-related pathogens suggested there are frequent sewage ingressions into the urban stormwater runoff during wet weather events. Further water quality monitoring study will be conducted at different contrasting urban catchments in order to undertake a more comprehensive public health risk assessment for urban stormwater.     

Assessing environmental soil quality in rural areas

A base line study into the environmental quality of soils in the rural areas of the province of Zeeland, the Netherlands, was performed. The polder-landscape in this area was developed in a complex history of floodings and land-reclamation. Samples from 67 sites, at a density of roughly one per 25 km², were analyzed for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in addition to a physicochemical characterization by pH(KCl), dry solids, organic matter, and clay content. At about 2/3 of the sites samples were taken at more than one depth. Fluoride and pesticides were determined in partly overlapping selections of 30 samples. Four land use classes were distinguished (arable land, grass land, orchards, uncultivated), and samples were labelled by region within the province. Data evaluation was aided by a recursive statistical approach, whereby statistical tests confirm and strengthen geochemical reasoning. Single- and multivariate statistics were used both as exploratory tools and as a measure of significance and relevance of conditions and processes. In general the environmental quality of the soils is satisfactory. Exceedence of the legal standards for natural background values at more than one site occurs for Cd, Cu, Hg and the pesticides DDT/DDE, dieldrin and HCH, at most by a factor of three. High levels of Hg appear related to arable land use; enhanced levels of Cu are found in orchards. High Cd levels primarily seem to follow a regional or geological pattern; yet, a relation with arable land use and clayey soils cannot be excluded. Pesticides are not detected in grass land, incidence is highest in orchards as well as in uncultivated areas. DDT levels appear to be generally inherited from the past. Variation in soil type as described by the macro physico-chemical characteristics is essential in explaining the variation in concentration level of the potential contaminants. Variations with depth also appear largely related to concurrent variation in soil properties. For As redox conditions and hydrological regime seem of importance, in addition to the geologic history. The influence of atmospheric input is inferred for Pb. The available data do not fully resolve the causes for the regional pattern that remains when the influences of soil type, geology, and land use have been taken into account. In addition to current concentration levels, the base line study offers general insight as to what degree variations in potential contaminants are of natural or anthropogenic origin. A succession of similar studies at suitable time intervals, each with a new selection of sampling sites, may constitute an evolving, flexible monitoring system. When putting up a monitoring system, authorities should weigh the advantages and disadvantages of a network composed of fixed sites against this alternative.     

Distribution of phthalate esters in topsoil: a case study in the Yellow River Delta, China

The Yellow River Delta (YRD) is a typical agricultural and petrochemical industrial area of China. To assess the current status of phthalate esters (PAEs) of soil residues, soil samples (0～20 cm) (n?=?82) were collected in Bincheng District, at the geographic center of the YRD. PAEs were detected in all topsoil samples analyzed, which indicated that PAEs are ubiquitous environmental contaminants. Concentrations of 11 PAEs are in the range of 0.794～19.504 μg g^?1, with an average value of 2.975 μg g^?1. It was presented that PAEs pollution in this area was weak and monotonously increasing along the rural–urban gradient. Higher concentrations were observed from roadsides (and/or gutters), densely anthropogenic activities areas (such as the urbanization and industrialization), and agriculture influence district, which mainly originated from construction waste, municipal sewage, agricultural waste and pesticide, discarded plastic effusion and atmospheric depositions. Concentrations of PAEs were weakly positivity correlated with soil organic carbon content and pH, which suggested both of them can affect the distribution of PAEs. The concentration of di (2-ethylhexyl) phthalate and di-n-butyl phthalate dominated in the 11 PAEs, with the average values of 0.735 and 1.915 μg g^?1, respectively, and accounted for 92.1 % of the whole PAEs’ concentrations. No significant differences of PAE congeneric profiles were observed between our work and others previously reported, which is consistent with the use of similar commercial PAEs around the world.     

Assessment of indoor airborne contamination in a wastewater treatment plant

The main objective of this work was to quantify and characterize the major indoor air contaminants present in different stages of a municipal WWTP, including microorganisms (bacteria and fungi), carbon dioxide, carbon monoxide, hydrogen sulfide ammonia, formaldehyde, and volatile organic compounds (VOCs). In general, the total bacteria concentration was found to vary from 60 to >52,560 colony-forming units (CFU)/m³, and the total fungi concentration ranged from 369 to 14,068 CFU/m³. Generally, Gram-positive bacteria were observed in higher number than Gram-negative bacteria. CO₂ concentration ranged from 251 to 9,710 ppm, and CO concentration was either not detected or presented a level of 1 ppm. H₂S concentration ranged from 0.1 to 6.0 ppm. NH₃ concentration was <2 ppm in most samples. Formaldehyde was <0.01 ppm at all sampling sites. The total VOC concentration ranged from 36 to 1,724 μg/m³. Among the VOCs, toluene presented the highest concentration. Results point to indoor/outdoor ratios higher than one. In general, the highest levels of airborne contaminants were detected at the primary treatment (SEDIPAC 3D), secondary sedimentation, and sludge dehydration. At most sampling sites, the concentrations of airborne contaminants were below the occupational exposure limits (OELs) for all the campaigns. However, a few contaminants were above OELs in some sampling sites.     

Determination of radioactive elements and heavy metals in sediments and soil from domestic water sources in northern peninsular Malaysia

Soil serves as a major reservoir for contaminants as it posseses an ability to bind various chemicals together. To safeguard the members of the public from an unwanted exposure, studies were conducted on the sediments and soil from water bodies that form the major sources of domestic water supply in northern peninsular Malaysia for their trace element concentration levels. Neutron Activation Analysis, using Nigeria Research Reactor-1 (NIRR-1) located at the Centre for Energy Research and Training, Zaria, Nigeria was employed as the analytical tool. The elements identified in major quantities include Na, K, and Fe while As, Br, Cr, U, Th, Eu, Cs, Co, La, Sm, Yb, Sc, Zn, Rb, Ba, Lu, Hf, Ta, and Sb were also identified in trace quantities. Gamma spectroscopy was also employed to analyze some soil samples from the same area. The results indicated safe levels in terms of the radium equivalent activity, external hazard index as well as the mean external exposure dose rates from the soil. The overall screening of the domestic water sources with relatively high heavy metals concentration values in sediments and high activity concentration values in soil is strongly recommended as their accumulation overtime as a consequence of leaching into the water may be of health concern to the members of the public.     

Corrections for measurements of tritium in subterranean vapor using silica gel

Hazardous contaminants buried within vadose zones can accumulate in soil gas. The concentrations and spatial extent of these contaminants are measured to evaluate potential transport to groundwater for public risk evaluation. Tritium is an important contaminant found and monitored for in vadose zones across numerous sites within the US nuclear weapons complex, including Los Alamos National Laboratory. The extraction, collection, and laboratory analysis of tritium from subterranean soil gas presents numerous technical challenges that have not been fully studied. Particularly, the lack of moisture in the soil gas in the vadose zone makes it difficult to obtain enough sample (e.g., >5 g) to provide for the required measurement sensitivity, and often, only small amounts of moisture can be collected. Further, although silica gel has high affinity for water vapor and is prebaked prior to sampling, there is still sufficient residual moisture in the prebaked gel to dilute the relatively small amount of sampled moisture; thereby, significantly lowering the ??true?? tritium concentration in the soil gas. This paper provides an evaluation of the magnitude of the bias from dilution, provides methods to correct past measurements by applying a correction factor (CF), and evaluates the uncertainty of the CF values. For this, 10,000 Monte Carlo calculations were performed, and distribution parameters of CF values were determined and evaluated. The mean and standard deviation of the distribution of CF values were 1.53 ± 0.36, and the minimum, median, and maximum values were 1.14, 1.43, and 5.27, respectively.