Prediction of Pollen-Mediated Gene Flow Between Fields of Red Clover (<Emphasis Type="Italic">Trifolium pratense</Emphasis>)

Pollen-mediated gene flow between red clover fields by bumblebees is predicted by estimating or simulating the parameters in a gene flow model for insect-pollinated crops. Generally, the predicted level of gene flow was found to depend on the visiting bee species and the spatial arrangement of the red clover fields. When the fields are close to each other, the gene flow depends mainly on the typical foraging distance of the visiting bee species, but when the fields are far apart, the gene flow between red clover fields is more sensitive to the distances between red clover fields than to the actual bumblebee species that pollinates the fields. Using the suggested methodology, the gene flow may be predicted in different agricultural scenarios. For example, if the gene flow between red clover fields is mediated by Bombus terrestris and the red clover fields that were assumed to be quadrates with sides of 100 m are separated by 200 m, then the median gene flow is predicted to be 0.17%.     

Leaching behavior of nitrogen in a long-term experiment on rice under different N management systems

The leaching behavior of nitrogen was studied in single rice paddy production ecosystems in Tsukuba, Japan after 75 years of consistent fertilization regimes (no fertilizer, ammonium sulfate, a combination of composted rice straw with soybean cake, and fresh clover). During the 75-year period, management was unchanged with respect to rice planting density, irrigation, and net N fertilization for each field to which an N-source was added. Percolation water was collected, from May 2001 to April 2002, using porous suction cups installed in the fields at depths of 15, 40, and 60 cm. All water samples were taken to the laboratory for the measurement of both NH₄ ^?+??CN and NO₃ ^????CN concentrations using a continuous-flow nitrogen analyzer. The result indicated that there were significant differences in N leaching losses between treatments during the rice growing season. Total N leaching was significantly lower with the application of composted rice straw plus soybean cake (0.58 kg N ha^???1) than with ammonium sulfate (2.41 kg N ha^???1), which resulted in N leaching at a similar level to that with the fresh clover treatment (no significant difference). The majority of this N leaching was not due to NO₃ ^????CN loss, but to that of NH₄ ^?+??CN. The mean N leaching for all fertilizer treatments during the entire rice growing season was 1.58 kg N ha^???1. Composted rice straw plus soybean cake produced leaching losses which were 65?C75% lower than those with the application of fresh clover and ammonium sulfate. N accumulation resulting from nitrification in the fallow season could be a key source of nitrate?CN leaching when fields become re-flooded before rice transplanting in the following year; particular attention should be paid to this phenomenon.     

Development of a Pollination Service Measurement (PSM) method using potted plant phytometry

The value of pollination to human society is not limited to agricultural production, but also in the sustainability of ecosystems and the services that they provide. Seed set can be used as a comparative measure of pollination effectiveness, with minimum variability expected when other resources are not limiting. Six species of self-incompatible fall asters (Symphyotrichum) were used to evaluate pollination service at 12 sites across a spectrum of expected levels of pollination. Seed set per inflorescence was generally lower at sites with lower pollinator numbers and diversity, although as expected pollinator assemblage characteristics were highly variable within and between sites. However, rankings of sites showed consistency of response across phytometer species and between years; the summed ranks across multiple species appears to have as the greatest value in Pollination Service Measurement (PSM). Abundance, richness, and Shannon diversity of pollinator assemblages were highly autocorrelated and showed variable relationships with seed set depending on plant species and temporal scale of pollinator assemblage assessment. Use of seed set to directly measure pollination service at a site was consistent and cost effective when compared to less certain and more labour-intensive methods of pollinator collection and identification, and shows promise for implementation in pollination monitoring and bioassessment practices.     

Prediction of the effluent from a domestic wastewater treatment plant of CASP using gray model and neural network

When a domestic wastewater treatment plant (DWWTP) is put into operation, variations of the wastewater quantity and quality must be predicted using mathematical models to assist in operating the wastewater treatment plant such that the treated effluent will be controlled and meet discharge standards. In this study, three types of gray model (GM) including GM (1, N), GM (1, 1), and rolling GM (1, 1) were used to predict the effluent biochemical oxygen demand (BOD), chemical oxygen demand (COD), and suspended solids (SS) from the DWWTP of conventional activated sludge process. The predicted results were compared with those obtained using backpropagation neural network (BPNN). The simulation results indicated that the minimum mean absolute percentage errors of 43.79%, 16.21%, and 30.11% for BOD, COD, and SS could be achieved. The fitness was higher when using BPNN for prediction of BOD (34.77%), but it required a large quantity of data for constructing model. Contrarily, GM only required a small amount of data (at least four data) and the prediction results were analogous to those of BPNN, even lower than that of BPNN when predicting COD (16.21%) and SS (30.11%). According to the prediction, results suggested that GM could predict the domestic effluent variation when its effluent data were insufficient.     

Physico-chemical assessment of paper mill effluent and its heavy metal remediation using aquatic macrophytes—a case study at JK Paper mill, Rayagada, India

The present investigation aims to assess the phytoremediation potential of six aquatic macrophytes, viz. Eichhornia crassipes, Hydrilla verticillata, Jussiaea repens, Lemna minor, Pistia stratiotes and Trapa natans grown in paper mill effluent of JK Paper mill of Rayagada, Orissa, for remediation of heavy metals. The experiment was designed in pot culture experiments. Assessment of physico-chemical parameters of paper mill effluent showed significant decrease in pH, conductivity, total dissolved solids, total suspended solids, chlorine, sulphur, biological and chemical oxygen demand after growth of macrophytes for 20 days. Phytoremediation ability of these aquatic macrophytic species for copper (Cu) and mercury (Hg) was indicated by assessing the decrease in the levels of heavy metals from effluent water. Maximum reduction (66.5 %) in Hg content of untreated paper mill effluent was observed using L. minor followed by T. natans (64.8 %). L. minor showed highest reduction (71.4 %) of Cu content from effluent water followed by E. crassipes (63.6 %). Phytoextraction potential of L. minor was remarkable for Hg and Cu, and bioaccumulation was evident from bioconcentration factor values, i.e. 0.59 and 0.70, respectively. The present phytoremediation approach was considered more effective than conventional chemical treatment method for removing toxic contaminants from paper mill effluent.     

Plants as bioindicators for archaeological prospection: a case of study from Domitian’s Stadium in the Palatine (Rome, Italy)

In this study, we analyzed the relationship between buried archaeological remains (masonries, pavements, and ancient ruins) and spontaneous vegetation growing above them. We carried out several vegetation surveys in the Domitian’s Stadium at the archaeological site of the Palatine (Rome). Vegetation data were collected using the Braun-Blanquet approach and elaborated using statistical analyses (cluster analysis) to assess the similarity among surveys. Structural, chorological, and ecological features of the plant communities were analyzed. Results showed that the vegetation responds significantly to the presence of sub-emerging ancient remains. The plant bioindication of this phenomenon occurs through the following floristic-vegetation variations: phenological alterations in single individuals (reduction in height, displacement of flowering/fruiting period), increase of annual species and decrease of perennial ones, decrease of total plant coverage, reduction of maturity level of the vegetation which remains blocked at a pioneer evolutive stage. The presence of sub-surfacing ruins manifests itself through the dominant occurrence of xerophilous and not-nitrophilous species (e.g., Hypochaeris achyrophorus L., Aira elegantissima Schur, Trifolium scabrum L. ssp. scabrum, Trifolium stellatum L., Plantago lagopus L., Medicago minima (L.) L., and Catapodium rigidum (L.) C.E. Hubb. ex Dony ssp. rigidum) and in a rarefaction of more mesophilous and nitrophilous species (e.g., Plantago lanceolata L., Trifolium pratense L. ssp. pratense, Trifolium repens L. ssp. repens, and Poa trivialis L.). Therefore, the vegetation can be used as bioindicator for the detection of buried ruins, contributing in the archaeological prospection for a general, fast, and inexpensive interpretation of the underground.     

Commercial bumblebee hives to assess an anthropogenic environment for pollinator support: a case study in the region of Ghent (Belgium)

Anthropogenic changes of the environment influence the distribution and abundance of pollinators such as bumblebees and have been proposed as one of the main causes in their worldwide decline. In order to evaluate the impact of expanding anthropogenic landscapes on supporting pollinator potential, reliable tools are needed. Bombus terrestris is one of the most abundant bumblebee species in Europe, and these bumblebees are known as generalist pollinators of not only wild flowers in nature but also of crops in agriculture. For more than two decades, these bumblebees have been commercially mass reared for biological pollination in greenhouses. In this project, we placed commercial hives of the bumblebee B. terrestris containing one queen and 40 workers, in three different locations in the region of Ghent (Belgium), and the performance of these hives was followed during a 4-week period in spring 2012. In parallel, we determined the floral richness and diversity index in the chosen study sites. The sites consisted of a rich urban environment with patchy green areas opposed to an urban environment with poor landscape metrics; a third rural study site showed average positive landscape metrics. The results demonstrated that the hive biomass and numbers of workers increased significantly in the rich compared to the poor environment, providing a mechanism to discriminate between study sites. In addition, the bumblebee-collected pollen showed that the flowering plants Salix spp. and Rosaceae/Prunus spp. are dominant food sources in all anthropogenic environments during early spring. Finally, the results are discussed in relation to the optimization of the experimental setup and to the use of commercial bumblebee hives in assessing local pollinator support within any given environment.     

Quantifying the introgressive hybridisation propensity between transgenic oilseed rape and its wild/weedy relatives

In order to estimate the introgressive hybridisation propensity (IHP) between genetically modified (GM) oilseed rape (Brassica napus) and certain of its cross-compatible wild/weedy relatives at the landscape level, a conceptual approach was developed. A gene flow index was established enclosing the successive steps to successfully achieve introgressive hybridisation: wild/weedy relatives and oilseed rape should co-occur, have overlapping flowering periods, be compatible, produce viable and fertile progeny, and the transgenes should persist in natural/weedy populations. Each step was described and scored, resulting in an IHP value for each cross-compatible oilseed rape wild/weedy relative. The gene flow index revealed that Brassica rapa has the highest introgressive hybridisation propensity (IHP value = 11.5), followed by Hirschfeldia incana and Raphanus raphanistrum (IHP = 6.7), Brassica juncea (IHP = 5.1), Diplotaxis tenuifolia and Sinapis arvensis (IHP = 4.5) in Flanders. Based on the IHP values, monitoring priorities can be defined within the pool of cross-compatible wild/weedy oilseed rape relatives. Moreover, the developed approach enables to select areas where case-specific monitoring of GM oilseed rape could be done in order to detect potential adverse effects on cross-compatible wild/weedy relatives resulting from vertical gene flow. The implementation of the proposed oilseed rape-wild relative gene flow index revealed that the survey design of existing botanical survey networks does not suit general surveillance needs of GM crops in Belgium. The encountered hurdles to implement the gene flow index and proposals to acquire the missing data are discussed.     

Potential for gene flow from genetically modified <Emphasis Type="Italic">Brassica napus</Emphasis> on the territory of Russia

Gene flow from genetically modified crops has been studied for more than 20 years, but public concern still remains. A lot of data on this matter is obtained on the territory of EU and the USA, but in the majority of countries, such experiments were never carried out. Here, we present the first study of interspecific and intraspecific hybridization of transgenic Brassica napus on the territory of Russia. The experiment was conducted using two different models of coexistence. Cross-pollination with related species was more frequent in mixed than that in separated populations. We observed maximum 4.1% of transgenic seeds in the progeny of Brassica rapa and 0.6% in the progeny of Brassica juncea. The highest intraspecific hybridization rate of 0.67% was observed in separated populations. DNA fragments, typical to both parents, were present in the genome of the hybrids. The risk of gene flow in Russia is relatively low, but it will be problematic to do environmental monitoring on such a big territory. However, instead of banning the cultivation of genetically modified crops, some new varieties with visually detectable selective traits could be designed and approved for cultivation.     

Monitoring and assessment of soil and forage molybdenum near an atmospheric source

Forage and soil molybdenum (Mo) were measured in the vicinity of a Mo processing plant in southwestern Pennsylvania, USA. Molybdenum concentrations in red clover plants (Trifolium pratense L.), measured at 23 sites, ranged from 1.1 to 56.6 mg kg^–1. Fourteen of the 23 sites sampled had red clover plants with Mo concentrations over the threshold value of 6 mg kg^–1. Red clover Cu:Mo concentration ratios were below the recommended ratio of 4 in 19 of the sites. The low Cu:Mo values, along with high plant Mo concentrations, indicates that there is a potential risk of molybdenosis in ruminant animals in this area. Acid digested (sorbed) soil Mo concentrations, measured at 30 sites, ranged from 7.0 (background level) to 131 mg kg^–1. Using the Baker Soil Test (BST) extract, molybdenum soil concentrations ranged from 0.01 to 3.99 mg kg^–1. Regression equations were developed to predict plant uptake of soil Mo based on the red clover plant, soil extracts and soil pH data. The R-squared values for predicting plant uptake were 81.9% for the BST extract and 81.6% for the acid digestion extract plus soil pH. Based on the above results, a protocol has been implemented for assessing the risk of high soil Mo near this Mo processing plant.     

Molecular quantification of virulence gene-containing Aeromonas in water samples collected from different drinking water treatment processes

Pathogenic species of Aeromonas produce a range of virulence factors, including aerolysin, cytotonic enterotoxins, and serine protease, to cause acute gastroenteritis and wound infections in humans and animals. Recognizing that not all Aeromonas strains are pathogenic, in this study, we proposed to evaluate Aeromonas removal effectiveness based on the presence of virulence gene-containing Aeromonas as a proper means to assess microbial risk of Aeromonas. We developed and applied real-time PCR assays to quantify serine protease (ser) gene- and heat-labile cytotonic enterotoxin (alt) gene-containing Aeromonas in water samples. Among 18 Aeromonas isolates from the source water, only three isolates possessed all three genes (aer, ser, and alt). A higher percent of isolates has either ser gene (89%) or alt gene (72%) compared to the percent of isolates containing aer gene (44%). Results of this study suggested that several different conventional and unconventional drinking water treatment processes could effectively remove Aeromonas from source water. As the comprehensive knowledge of the distribution of virulence factors in different Aeromonas species is currently not available, using real-time PCR to quantify various virulence factor genes in water samples and/or isolates can be a practical means for better assessment of microbial risks in water.     

Assessment of six Indian cultivars of mung bean against ozone by using foliar injury index and changes in carbon assimilation, gas exchange, chlorophyll fluorescence and photosynthetic pigments

Six Indian cultivars of Vigna radiata L. (HUM-1, HUM-2, HUM-6, HUM-23, HUM-24 and HUM-26) were exposed with ambient and elevated (ambient + 10 ppb ozone (O₃) for 6 h?day^?1) level of O₃ in open top chambers. Ozone sensitivity was assessed by recording the magnitude of foliar visible injury and changes in various physiological parameters. All the six cultivars showed visible foliar symptoms due to O₃, ranging 7.4 to 55.7 % injured leaf area. O₃ significantly depressed total chlorophyll, photosynthetic rate (Ps), quantum yield (F _v/F _m) and total biomass although the extent of variation was cultivar specific. Cultivar HUM-1 showed maximum reduction in Ps and stomatal conductance. The fluorescence parameters also indicated maximum damage to PSII reaction centres of HUM-1. Injury percentage, chlorophyll loss, Ps, F _v/F _m and total biomass reduced least in HUM-23 depicting highest O₃ resistance (R%).     

Impact of long-term wastewater application on microbiological properties of vadose zone

Impact of wastewater irrigation on some biological properties was studied in an area where treated sewage water is being supplied to the farmers since 1979 in the western part of National Capital Territory of New Delhi under Keshopur Effluent Irrigation Scheme. Three fields were selected which had been receiving irrigation through wastewater for last 20, 10 and 5 years. Two additional fields were selected in which the source of irrigation water was tubewell. The soil bacterial and fungal population density was studied in soil layers of 0?C15, 15?C30, 30?C60 and 60?C120 cm depths. Groundwater samples were collected from the piezometers installed in the field irrigated with sewage water for last 20, 10 and 5 years. Results indicate that there was significant increase in bacterial and fungal count in sewage-irrigated soils as compared to their respective control. The population density of bacteria and fungi in waste water-irrigated soils increased with the duration of sewage water application and decreased with increasing depth. The bacterial and fungal count was also directly proportional to organic carbon, sand and silt content and negatively correlated to the clay content, electrical conductivity, pH and bulk density of the soil. Groundwater under sewage-irrigated fields had higher values of most probable number (MPN) index as compared to that of tubewell water-irrigated fields. All the shallow and deep groundwaters were found to be contaminated with faecal coliforms. The vadose zone had filtered the faecal coliform to the tune of 98?C99%, as the MPN index was reduced from ??18,000 per 100 ml of applied waste water to 310 per 100 ml of groundwater under 20 years sewage-irrigated field. The corresponding values of MPN were 250 and 130 per 100 ml of shallow groundwater under 10 and 05 years sewage-irrigated fields, respectively. Rapid detection of faecal contamination suggested that the Citrobacter freundii and Salmonella were dominant in shallow groundwater, while Escherichia coli was dominant in deep groundwater collected from sewage-irrigated field.     

Associations between self-reported odour annoyance and volatile organic compounds in ‘Chemical Valley’, Sarnia, Ontario

Annoyance produced by air pollution has been suggested as a useful proxy for determining ambient air pollution exposure. However, most of the studies, to date, have focused on nitrogen dioxide and sulphur dioxide, with no work done on volatile organic compounds (VOC). This study is aimed at examining the associations between odour annoyance and VOC in ‘Chemical Valley’, Sarnia, Ontario, Canada. Annoyance scores were extracted from a community health survey (N?=?774), and exposures to VOC were estimated from respondents’ six-digit alphanumeric postal codes using land use regression models. Univariate analyses were used to explore the relationships between odour annoyance and modelled pollutants, whilst multivariate ordinal logistic regression was utilized to examine the determinants of odour annoyance. The results indicate that odour annoyance is significantly associated with modelled benzene, toluene, ethylbenzene, o-xylene and (m?+?p)?xylene (BTEX) pollutants. The findings also show that the determinants of odour annoyance in the context of VOC include gender, number of relatives in the community, perception of air pollution, community satisfaction, medical checkups, ability to cope with daily life demands and general symptoms. When compared, the analysis indicates that Sarnia residents respond to considerably lower BTEX concentrations than the allowable ‘safe’ levels in the province of Ontario. In general, the results exhibit a dose–response gradient with annoyance score increasing with rising modelled pollutant concentrations. The observed relationships suggest that odour annoyance might be a function of true exposure and may serve as a proxy for air quality and ambient air pollution monitoring. However, questionnaire-based odour annoyance scores need to be longitudinally validated across different geographical scales and pollutants if they are to be adopted at the national level.     

Methodological scheme for designing the monitoring of genetically modified crops at the regional scale

According to EC regulations the deliberate release of genetically modified (GM) crops into the agro-environment needs to be accompanied by environmental monitoring to detect potential adverse effects, e.g.unacceptable levels of gene flow from GM to non-GM crops, or adverse effects on single species or species groups thus reducing biodiversity. There is, however, considerable scientific and public debate on how GM crops should be monitored with sufficient accuracy, discussing questions of potential adverse effects, agro-environmental variables or indicators to be monitored and respective detection methods; Another basic component, the appropriate number and location of monitoring sites, is hardly considered. Currently, no consistent GM crop monitoring approach combines these components systematically. This study focuses on and integrates spatial agro-environmental aspects at a landscape level in order to design monitoring networks. Based on examples of environmental variables associated with the cropping of Bt-Maize (Zea maize L.), herbicide-tolerant (HT) winter oilseed rape (Brassica napus L.), HT sugar beet (Beta vulgaris L.), and starch-modified potato (Solanum tuberosum L.), we develop a transferable framework and assessment scheme that comprises anticipated adverse environmental effects, variables to be measured and monitoring methods.These we integrate with a rule-based GIS (geographic information system) analysis, applying widely available spatial area and point information from existing environmental networks. This is used todevelop scenarios with optimised regional GM crop monitoring networks.     

Study on concentration of ambient NH 3 and interactions with some other ambient trace gases

We present diurnal variation of ambient ammonia (NH₃) in relation with other trace gases (O₃, CO, NO, NO₂, and SO₂) and meteorological parameters at an urban site of Delhi during winter period. For the first time, ambient ammonia (NH₃) was monitored very precisely and continuously using ammonia analyzer, which operates on chemiluminescence method. NH₃ estimation efficiency of the chemiluminescence method (>90%) is much higher than the conventional chemical trapping method (reproducibility 4.5%). Ambient NH₃ concentration reaches its maxima (46.17 ppb) at night and minimum during midday. Result reveals that the ambient ammonia (NH₃) concentration is positively correlated with ambient NO (r ²?=?0.79) and NO₂ (r ²?=?0.91) mixing ratio and negatively correlated with ambient temperature (r ²?=???0.32). Wind direction and wind speed indicates that the nearby (~500 m NW) agricultural fields may be major source of ambient NH₃ at the observational site.     

Numerical Modeling of Flow Fields and Dispersion of Passive Pollutants in the Vicinity of the Temelín Nuclear Power Plant

This study deals with numerical simulation of flow fields and dispersion of model passive admixtures in the planetary boundary layer in a 10 × 10 km square area, centered on the Czech Republic’s Temelín Nuclear Power Plant. Numerical calculations of three-dimensional flow fields with eight basic wind directions given for the inlet boundary of the computational domain are performed using the FLUENT CFD code with the standard k – ε turbulence model. The resultant modeling of the flow fields provides information as to probable local directions and velocities of flow vectors on a horizontal scale of 100 m, which are consistent with the data given for the boundaries of the calculation area in the framework of a scale of 10 km. The modeled flow fields generate the input data for related Lagrangian simulation of the ground concentration and deposition fields of passive particles assumedly emitted at the site of the Temelín plant. Simulated plumes describe eight cases of potential ground-level distribution of model passive admixtures in the area.     

Antibiotic-resistant E. coli in surface water and groundwater in dairy operations in Northern California

Generic Escherichia coli was isolated from surface water and groundwater samples from two dairies in Northern California and tested for susceptibility to antibiotics. Surface samples were collected from flush water, lagoon water, and manure solids, and groundwater samples were collected from monitoring wells. Although E. coli was ubiquitous in surface samples with concentrations ranging from several hundred thousand to over a million colony-forming units per 100 mL of surface water or per gram of surface solids, groundwater under the influence of these high surface microbial loadings had substantially fewer bacteria (3- to 7-log₁₀ reduction). Among 80 isolates of E. coli tested, 34 (42.5 %) were resistant to one or more antibiotics and 22 (27.5 %) were multi-antibiotic resistant (resistant to ≥3 antibiotics), with resistance to tetracycline, cefoxitin, amoxicillin/clavulanic acid, and ampicillin being the most common. E. coli isolates from the calf hutch area exhibited the highest levels of multi-antibiotic resistance, much higher than isolates in surface soil solids from heifer and cow pens, flush alleys, manure storage lagoons, and irrigated fields. Among E. coli isolates from four groundwater samples, only one sample exhibited resistance to ceftriaxone, chloramphenicol, and tetracycline, indicating the potential of groundwater contamination with antibiotic-resistant bacteria from dairy operations.     

Assessment of river water quality during snowmelt and base flow periods in two catchment areas with different land use

River water quality was evaluated with respect to eutrophication and land use during spring snowmelt and summer base flow periods in Abashiri (mixed cropland-livestock farming) and Okoppe (grassland-based dairy cattle farming), eastern Hokkaido, Japan. Water from rivers and tributaries was sampled during snowmelt and summer base flow periods in 2005, and river flow was measured. Total N (TN), NO₃–N, and Si concentrations were determined using standard methods. Total catchment and upland areas for each sampling site were determined with ArcGIS hydrology modeling software and 1:25,000-scale digital topographic maps. Specific discharge was significantly higher during snowmelt than during base flow. In both areas, TN concentrations increased, whereas Si concentrations decreased, with increased specific discharge, and were significantly higher during snowmelt. The Si:TN mole ratio decreased to below or close to the threshold value for eutrophication (2.7) in one-third of sites during snowmelt. River NO₃–N concentrations during base flow were significantly and positively correlated with the proportion of upland fields in the catchment in both the Abashiri (r = 0.88, P < 0.001) and Okoppe (r = 0.43, P < 0.01) areas. However, the regression slope, defined as the impact factor (IF) of water quality, was much higher in Abashiri (0.025) than in Okoppe (0.0094). The correlations were also significantly positive during snowmelt in both areas, but IF was four to eight times higher during snowmelt than during base flow. Higher discharge of N from upland fields and grasslands during snowmelt and the resulting eutrophication in estuaries suggest that nutrient discharge during snowmelt should be taken into account when assessing and monitoring the annual loss of nutrients from agricultural fields.     

Wilk’s Method Based Model for Regulations Related to Radiological Impact of Opencast Uranium Mining on Water Reservoirs

Opencast mining of uranium may lead to natural erosion of ore material due to overland flow of water accumulated from rainfall. The overland flow may ultimately reach the nearby surface water body. This process may lead to the release of ²³⁸U and its daughter products into the surface water body. A model is developed to assess the radiological impact of the erosion in terms of dose through drinking water pathway due to ²³⁸U and its progeny in the surface water body. The in-growth of progeny is taken into account using Bateman equations. The study brings out the importance of incorporating decay chain transport in the radiological impact assessment studies. It is also observed that ²¹⁰Po, ²¹⁰Pb, ²²⁶Ra, and ²³⁰Th together contribute to about 95.5 % of the total dose. The model is then extended to incorporate the uncertainty associated with the dose due to consumption of the reservoir water by employing Wilk’s Method. Such a model can be very useful in establishing regulations related to dose through drinking water pathway around an opencast mine. Wilk’s method is computationally less expensive as compared to the exact methods like Monte Carlo method. Wilk’s method is used to calculate a value greater than α percentile value for the dose to the public due to ²³⁸U and its progeny in the reservoir through drinking water pathway with confidence level β (α/β value). When applied to a hypothetical case using some literature data on surface water bodies, it is found that with increase in the value of α or β, the α/β value in general, shows an increasing trend as expected. Depending upon the nature of the problem under study, one can calculate an α/β value i.e. 95/95 value, 99/95 value etc., and that value can be helpful in establishing the regulatory limiting value. Also, the α/β value can be used to check whether dose due to a particular radioactive release is within the specified limits.