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1.
The increasing emission of primary and gaseous precursors of secondarily formed atmospheric particulate matter due to continuing industrial development and urbanization are leading to an increased public awareness of environmental issues and human health risks in China. As part of a pilot study, 12-h integrated fine fraction particulate matter (PM2.5) filter samples were collected to chemically characterize and investigate the sources of ambient particulate matter in Guiyang City, Guizhou Province, southwestern China. Results showed that the 12-h integrated PM2.5 concentrations exhibited a daytime average of 51 ± 22 µg m?3 (mean ± standard deviation) with a range of 17–128 µg m?3 and a nighttime average of 55 ± 32 µg m?3 with a range of 4–186 µg m?3. The 24-h integrated PM2.5 concentrations varied from 15 to 157 µg m?3, with a mean value of 53 ± 25 µg m?3, which exceeded the 24-h PM2.5 standard of 35 µg m?3 set by USEPA, but was below the standard of 75 µg m?3, set by China Ministry of Environmental Protection. Energy-dispersive X-ray fluorescence spectrometry (XRF) was applied to determine PM2.5 chemical element concentrations. The order of concentrations of heavy metals in PM2.5 were iron (Fe) > zinc (Zn) > manganese (Mn) > lead (Pb) > arsenic (As) > chromium (Cr). The total concentration of 18 chemical elements was 13 ± 2 µg m?3, accounting for 25% in PM2.5, which is comparable to other major cities in China, but much higher than cities outside of China.  相似文献   

2.
This study was carried out to assess the distribution of uranium in groundwater by using LED fluorimeter LF-2a and chemical and radiological risks associated with its consumption in Sirsa district, Haryana, India. Uranium concentration ranged between 0.93 and 290μg l-1 with an average value of 49 μg l-1. About 44% of the groundwater samples had uranium concentration above the maximum contamination level of 30 μg l-1 prescribed by the World Health Organization and United States Environmental Protection Agency and 22% of the samples exceeded the permissible limit of 60 μgl-1 prescribed by the Atomic Energy Regulatory Board, India. The average cancer morbidity and mortality risks are determined to be 1.10 × 10-4 and 7.17 × 10-5 respectively, indicating the negligible carcinogenic risk. Hazard quotient for 44% samples is greater than unity which indicates health risk due to chemical toxicity of uranium in groundwater. The associated age-dependent annual effective dose is estimated by taking the prescribed water intake values of different age groups.  相似文献   

3.
The radioactivity due to 238U and 234U in three aquifer systems occurring within the Paraná sedimentary basin, South America, has been investigated. Uranium is much less dissolved from fractured igneous rocks than from the porous sedimentary rocks as indicated by the U-mobility coefficients between 7.6 × 10?6 and 1.2 × 10?3 g cm?3. These values are also compatible with the U preference ratios relative to Na, K, Ca, Mg and SiO2, which showed that U is never preferentially mobilized in the liquid phase during the flow occurring in cracks, fissures, fractures and faults of the igneous basaltic rocks. Experimental dissolution of diabase grains on a time-scale laboratory has demonstrated that the U dissolution appeared to be a two-stage process characterized by linear and second-order kinetics. The U dissolution rate was 8 × 10?16 mol m?2 s?1 that is within the range of 4 × 10?16–3 × 10?14 mol m?2 s?1 estimated for other rock types. The 234U/238U activity ratio of dissolved U in solutions was higher than unity, a typical result expected during the water–rock interactions when preferential 234U-leach from the rock surfaces takes place. Some U-isotopes data allowed estimating 320 ka for the groundwater residence time in a sector of a transect in São Paulo State. A modeling has been also realized considering all U-isotopes data obtained in Bauru (35 samples), Serra Geral (16 samples) and Guarani (29 samples) aquifers. The results indicated that the Bauru aquifer waters may result from the admixture of waters from Guarani (1.5 %) and Serra Geral (98.5 %) aquifers.  相似文献   

4.
A geophysical and geochemical study was carried out in the Maneadero aquifer, Baja California, Mexico, with the aim of identifying potential recharge locations for reclaimed water (RW). This coastal aquifer shows a significant decline in water quality, both as a result of salinization and the pollution by nitrates. Total dissolved solids (TDS) in an extreme case increased from 4 g l?1 in 2000 to 27 g l?1 in 2011. Nitrate as N–NO3, reaches 46 mg l?1. Based on their geochemistry and location, four water-quality zones are identified: (a) fresh water with TDS ≈ 1 g l?1 in the upper creeks, (b) mixture between seawater and freshwater in the coast-proximal sections, (c) water significantly enriched in nitrate below and adjacent to the town of Maneadero, and (d) brackish water with no signs of current interaction with freshwater. The 3D geophysics identifies the influence of modern recharge areas and also buried flow-paths down to at least 30 m depth. The locations best suitable for aquifer recharge are those with equal or higher TDS concentrations (>2.5 g l?1) than RW, which are located at the brackish water zone and/or at the coastal limits of the mixing zones.  相似文献   

5.
There has been a growing awareness of As in the environment due to both anthropogenic and geogenic loading. This study quantifies the presence of As in river water, river sediment and groundwater within the Harlech Dome region of the UK, an area underlain by Cambro–Ordovician aged mineralization. Published data regarding As levels in UK groundwater are relatively rare compared to elsewhere. Arsenic levels in groundwater (0.1–18 µg l?1) and river sediment (1.5–142 mg kg?1) exceed environmental quality guidelines and indicate the release of As into the secondary environment from predominantly geogenic sources. Modelling of dissolved As speciation using ORP–pH diagrams predicts the presence of As in both arsenate (As5+) and arsenous acid (As3+) species, which possess differing solubilities and mobilities. Calculation of enrichment factors (EFs) for As in river sediments, using Al as a reference element, indicates highest EFs, and therefore As release, occurs in streams draining the Coed-y-Brenin region in the south-east of the Harlech Dome. This area is underlain by an as yet unexploited porphyry copper deposit. Data indicate that the presence of potentially harmful elements within the environment may occur with or without the presence of major anthropogenic activity.  相似文献   

6.
A novel strain of the genus Micrococcus isolated from wastewater was studied for resistance to seven heavy metals and forty antibiotics. Its capacity to accumulate metal ions was also realized at different pH. The strain exhibited high minimal inhibitory concentration values for metal ions tested and resist to 15 antibiotics. The living cells of the bacterial strain show a largest uptake capacity at pH 6–8.5 for copper, nickel, and zinc with values ranging from 51.45 to 83.90 %, 52.59 to 78.81 %, and 59.55 to 78.90 %, respectively. It was also able to absorbed 59.81–80.08 % of chromium and 58.09–79.41 % of cobalt at pH 7.3–8.5. The maximum lead uptake was obtained at pH 5.5–8.5 with an amount of 55.28–91.06 %. The significant absorption of cadmium was shown at pH 6.5 with 38 %. In 25 µg mL-1 zinc, chromium, and nickel solutions, dead cells of the isolate were able to biosorbed 20.46, 22.5, and 23.98 µg mL?1, respectively, after 30 min of contact. In other solutions with higher concentrations 50 and 100 µg mL?1, the amount of each metal immobilized was, respectively, as follows: 38.02 and 90.21 µg mL?1 for zinc, 39.78 and 89.23 µg mL?1 for chromium, and 47.19 and 86.83 µg mL?1 for nickel. Due to its high-metal accumulation capacity in aerobic conditions, these Gram-positive bacteria may be potentially applicable in situ bioremediation of heavy metals contaminating aqueous systems.  相似文献   

7.
The hydrogeochemical and isotopic evolution of groundwaters in the Mio–Pliocene sands of the Complexe Terminal (CT) aquifer in central Algeria are described. The CT aquifer is located in the large sedimentary basin of the Great Oriental Erg. Down-gradient groundwater evolution is considered along the main representative aquifer cross section (south–north), from the southern recharge area (Tinrhert Plateau and Great Oriental Erg) over about 700 km. Groundwater mineralisation increases along the flow line, from 1.5 to 8 g l?1, primarily as a result of dissolution of evaporite minerals, as shown by Br/Cl and strontium isotope ratios. Trends in both major and trace elements demonstrate a progressive evolution along the flow path. Redox reactions are important and the persistence of oxidising conditions favours the increase in some trace elements (e.g. Cr) and also NO3 ?, which reaches concentrations of 16.8 mg l?1 NO3-N. The range in 14C, 0–8.4 pmc in the deeper groundwaters, corresponds with late Pleistocene recharge, although there then follows a hiatus in the data with no results in the range 10–20 pmc, interpreted as a gap in recharge coincident with hyper-arid but cool conditions across the Sahara; groundwater in the range 24.7–38.9 pmc signifies a distinct period of Holocene recharge. All δ18O compositions are enriched relative to deuterium and are considered to be derived by evaporative enrichment from a parent rainfall around ?11‰ δ18O, signifying cooler conditions in the late Pleistocene and possibly heavy monsoon rains during the Holocene.  相似文献   

8.
Water samples from the river network and from some shallow and brackish springs located in a tectonic window of the northern Apennines of Italy were studied in the frame of a comprehensive hydrogeological investigation in order to better understand the origin and the mixing processes between the two water types noticed also in previous studies (Ca–HCO3 and Na–Cl). A sampling campaign covering the drought period during year 2010 was planned to gather electric conductivity, temperature and redox potential data along the river network and on groundwater occurrences located inside the tectonic structure. Additionally, eight water samples were collected for hydrochemical (major anions and cations: Na+, K+, Ca2+, Mg2+, HCO3 ?, Cl?, SO4 2? and trace ion Btot) and isotopic (δ18O, δ2H, 3H) analyses and compared with other eighteen samples from shallow and brackish springs collected near the study site during the period 2005–2012. Moreover, river discharge and water balance estimations were carried out. Results confirmed the presence of old Na–Cl water with salinity progressively increasing up to 5.5 g l?1 at the northern termination of the tectonic window. These values are in agreement with the ions contents of the most mineralized spring (Macognano spring: salinity of 7.6 g l?1), which has been considered as having the deepest and longest flow-path. Stable isotopes and trace ions contents are consistent with rainfall and snowmelt water mixed with brines associated with a hydrocarbon reservoir hosted at depth. Considering as end-member the more mineralized Na–Cl water, a cumulate inflow in the range of 12.9 ± 5.9 l s?1 has been estimated. This aliquot is released into the river network with different mixing proportions by the groundwater occurrences discharging from the autochthonous flysch unit.  相似文献   

9.
Enzymatic and alkali pretreatments were employed to improve nickel biosorption capacity of Rhizomucor pusillus biomass. Pretreatment with 0.002–80 g l?1 NaOH and 0.0001–0.1 Anson Unit (AU) g?1 protease enhanced the biosorption capacity of fungal biomass. Increasing the concentration of NaOH from 0.002 to 5 g l?1 improved nickel removal from 93.2 to 100.0 % while untreated biomass showed 64.6 % Ni(II) removal. Pretreatment with higher concentrations of NaOH, 5–80 g l?1 resulted in nearly complete removal of nickel ions. Pretreatment of the biomass with 0.0001 AU g?1 protease improved the nickel removal to over 91 %, while increasing the enzyme loading to 0.1 AU g?1 improved the removal to 93 %. Untreated biomass removed 78.4, 63.0, and 96.3 % of chromium, copper, and lead ions, respectively, from a mixture solution of the ions. Respective metal removals were increased to 100, 98.9, and 100 % after pretreatment with 0.2 g l?1 NaOH solution and to 87.8, 86.7, and 100 % after the enzymatic pretreatment with 0.1 AU g?1 protease. Scanning electron microscopy analysis indicated that alkali and enzymatic pretreatments enhanced the porosity of the biomass. Furthermore, compositional analysis showed that both of the pretreatments removed a major part of fungal proteins (2.1–95.8 % removal). Glucosamine, N-acetyl glucosamine, and phosphates were the major ingredients of the pretreated biomass.  相似文献   

10.
Carbendazim and Chlorpyrifos are some of the most widespread environmental contaminants of major concern to human and animal reproductive health. Acute toxicity test results for pesticides were evaluated by the Probit analysis method and 96 h LC50 values for C. chanos exposed to chlorpyrifos was 3.73 and 11.5 μg l?1 for carbendazim. Chlorpyrifos and carbendazim significantly decreased total protein, catalase, glutathione S-transferase and acetyl choline esterase and induced lipid peroxidation. Maximum effects of protein, catalase, lipid peroxidation, acetyl choline esterase and glutathione s-transferase were obtained in response to 23.68 μg l?1 of chlorpyrifos and 43.68 μg l?1 of carbendazim. Micronuclei assay results have shown increased abnormality with increasing doses of chlorpyrifos and carbendazim. Maximum increasing in micronuclei was observed in chlorpyrifos exposed C. chanos. This study showed that chlorpyrifos and carbendazim induced alterations in the activity of antioxidant enzymes and could induce clastogenicity.  相似文献   

11.
An attempt has been made in Chinnar sub basin of Dharmapuri district, South India to isolate the geochemistry of uranium occurrences in groundwater. The geology of the area is mainly of charnockite and granite gneiss. Groundwater samples were collected for two different seasons post and pre monsoon in two different litho units (granite gneiss and charnockite) and analysed for major, minor and uranium concentrations. Higher uranium (18.45 μg L?1) has been recorded during pre monsoon season in granite gneiss with increasing pH. The saturation index calculation for the groundwater isolated minerals like uaraninite, coffinite, haiweeite and soddyite to be precipitating and uranium oxides like UO2.25, UO2.25beta, UO2.33beta as oversaturated. The Eh-pH diagram attempted represents solubility of uraninite within the pH range of 6.0 to 8.0. The study isolate uranium in groundwater of the study area is controlled by the presence of (U4O9) uranium oxide.  相似文献   

12.
Chemical data on groundwater composition in rhyolitic hard rock aquifers with limited global occurrence are rarely found. In this research geochemistry of Mahabad Rhyolite Aquifer, NW Iran, was studied considering major ions, silica and trace elements measured in wet and dry seasons. Based on the results, the mean silica content was 18 mg l?1, less than the average of the rhyolitic waters. However, the relatively higher electrical conductivity (EC) of 418 µS cm?1 was measured. Based on a PHREEQCI model, the weathering of the silicate minerals and dissolution of carbonated intercalations turns groundwater dominantly into Ca–HCO3 type, enhancing EC, pH and silica concentration along the flow path. Trace elements of Sr, Ba and Pb were measured at highest concentrations, the later with an average value of 83 ppb exceeds the drinking guidelines. Cluster analysis confirms biotite weathering and barite dissolution as the main sources of the trace elements in the groundwater. The results signify geochemical features of rhyolitic groundwater which can be a useful tracer of mixing in flow systems containing variety of aquifers including rhyolites.  相似文献   

13.
The concentrations of uranium, iron and the major constituents were determined in groundwater samples from aquifer containing uranyl phosphate minerals (meta-autunite, meta-torbernite and torbernite) in the Köprüba?? area. Groundwater samples from wells located at shallow depths (0.5–6 m) show usually near neutral pH values (6.2–7.1) and oxidizing conditions (Eh = 119–275 mV). Electrical conductivity (EC) values of samples are between 87 and 329 μS/cm?1. They are mostly characterized by mixed cationic Ca dominating bicarbonate types. The main hydrogeochemical process is weathering of the silicates in the shallow groundwater system. All groundwater in the study area are considered undersaturated with respect to torbernite and autunite. PHREEQC predicted UO2(HPO4) 2 2? as the unique species. The excellent positive correlation coefficient (r = 0.99) between U and PO4 indicates the dissolved uranium in groundwater would be associated with the dissolution of uranyl phosphate minerals. The groundwater show U content in the range 1.71–70.45 μg/l but they are mostly lower than US EPA (2003) maximum contaminant level of 30 μg/l. This low U concentrations in oxic groundwater samples is attributed to the low solubility of U(VI) phosphate minerals under near neutral pH and low bicarbonate conditions. Iron closely associated with studied sediments, were also detected in groundwater. The maximum concentration of Fe in groundwater samples was 2837 μg/l, while the drinking water guidelines of Turkish (TSE 1997) and US EPA (2003) were suggested 200 and 300 μg/l, respectively. Furthermore, iron and uranium showed a significant correlation to each other with a correlation coefficient (r) of 0.94. This high correlation is probably related to the iron-rich sediments which contain also significant amounts of uranium mineralization. In addition to pH and bicarbonate controlling dissolution of uranyl phosphates, association of uranyl phosphates with iron (hydr) oxides seems to play important role in the amount of dissolved U in shallow groundwater.  相似文献   

14.
The Choptank River, Chesapeake Bay’s largest eastern-shore tributary, is experiencing increasing nutrient loading and eutrophication. Productivity in the Choptank is predominantly nitrogen-limited, and most nitrogen inputs occur via discharge of high-nitrate groundwater into the river system’s surface waters. However, spatial patterns in the magnitude and quality of groundwater discharge are not well understood. In this study, we surveyed the activity of 222Rn, a natural groundwater tracer, in the Choptank’s main tidal channel, the large tidal tributary Tuckahoe Creek, smaller tidal and non-tidal tributaries around the basin, and groundwater discharging into those tributaries, measuring nitrate and salinity concurrently. 222Rn activities were <100 Bq m?3 in the main tidal channel and 100–700 Bq m?3 in the upper Choptank River and Tuckahoe Creek, while the median Rn activities of fresh tributaries and discharging groundwater were 1,000 and 7,000 Bq m?3, respectively. Nitrate-N concentrations were <0.01 mg L?1 throughout most of the tidal channel, 1.5–3 mg L?1 in the upper reaches, up to 13 mg L?1 in tributary samples, and up to 19.6 mg L?1 in groundwater. Nitrate concentrations in tributary surface water were correlated with Rn activity in three of five sub-watersheds, indicating a groundwater nitrate source. 222Rn and salinity mass balances indicated that Rn-enriched groundwater discharges directly into the Choptank’s tidal waters and suggested that it consists of a mixture of fresh groundwater and brackish re-circulated estuarine water. Further sampling is necessary to constrain the Rn activity and nitrate concentration of discharging groundwater and quantify direct discharge and associated nitrogen inputs.  相似文献   

15.
In this study we investigate the radiological hazard of naturally occurring radioactive material in Tunisian and Algerian phosphorite deposits. Eight samples of phosphorite were collected from the phosphorite mines. The Tunisian and Algerian phosphorites occur in the Late Paleocene and Lower Eocene (Ypresian-Lutetian) in age (Béji Sassi 1984 and Zaïer 1999). Activity concentrations in all the samples were measured by alpha spectrometry and gamma spectrometry. Alpha spectrometry analyses show that the specific activity values of 238U, 234U and 235U in the samples of Tunisian phosphorite were 327?±?7 (321–327), 326?±?6 (325–331) and 14.50?±?0.72 (13.90–15.57) Bq kg?1, respectively. Specific activity measured by gamma spectrometry in the samples of the Tunisian and Algerian phosphorite shows a small difference. Specific activity levels of 40K, 226Ra, 232Th, 235U and 238U in the phosphorite samples from Tunisia were, respectively, 71.10?±?3.80, 391.54?±?9.39, 60.38?±?3.74, 12.72?±?0.54 and 527.42?±?49.57 Bq kg?1 and Algeria were 15.72?±?1.73, 989.65?±?12.52, 12.08?±?1.20, 47.50?±?1.52 and 1,148.78?±?7.30 Bq kg?1, respectively. The measured value of specific activity of 232Th and 40K in the Tunisian phosphorite samples is relatively higher than that found in the samples of Algerian phosphorite. The measured activity of uranium (238U) in the Tunisian phosphorite (527?±?49) Bq kg?1 is lower than in Algerian phosphorite. The measured activity of 238U in the Tunisian phosphorite samples was (527–1,315?±?65) 238U Bq kg?1 which is higher than its maximum background value of 110 Bq kg?1 in soils of the various countries of the world (Tufail et al. Radiat Meas 41:443–451, 2006). Different geological origins of phosphorites deposits are the main reason for the large spread in worldwide specific activities. The obtained results of uranium concentrations in phosphorites of different types (Algerian and Tunisian) demonstrate that the uranium concentrations are mainly governed by the phosphatic material. The present study reveals that phosphorite deposits contain natural radioactivity higher than background level.  相似文献   

16.
A diazinon-degrading bacterium was isolated from paddy soils under flooded conditions. Biochemical characterization and 16S rRNA sequencing showed the isolate was an oxidase-positive Stenotrophomonas maltophilia. The isolate could grow on a mineral salt medium (MSM) supplemented with diazinon as the main carbon source (50 µg ml?1) and dissipate the pesticide in a simple first-order manner with DT50 and DT90 of 4.54 and 15.09 days, respectively. The addition of glucose favored the bacterial growth and reduced the pesticide’s DT50 and DT90 to 3.39 and 11.27 days, respectively. The dissipation of diazinon in MSM was accompanied by a slight reduction of the pH which was more significant in the glucose-treated media. FTIR analysis proved the separation of the heterocyclic leaving group by hydrolyzing the ester bond and aerobic cleavage of the aromatic ring as the main pathways of diazinon degradation in the MSM. The dissipation of diazinon (150 µg g?1) in the inoculated sterilized flooded paddy soils was biphasic, and based on this, only 31.55 µg g?1 of the initial concentration declined with a faster rate while the rest of the residue dissipated slowly as the adsorbed phase. In the non-inoculated non-sterilized soils, diazinon dissipated more slowly with an initial lag phase.  相似文献   

17.
Uranium contents and234U/238U ratios have been determined on 29 water samples from the Taiyuan area, Shanxi Province. The results show that the same artesian aquifer has similar uranium contents and234U/238U activity ratios, and the deeper aquifers have higher A. R. values but lower uranium contents. The A. R. values increase slightly towards groundwater flow in the artesian aquifers dominated by oxidizing ground waters. The Lancun Spring and the famous Jinci Spring belong to two different karst groundwater systems, i.e., the east and west karst groundwater systems. The recharge area of the Lancun Spring should cover the wide limestone outcrops of middle Ordovician in the northeast. The Ordovician fissure-karst ground water to the Jinci Spring is extensively mixed with fissure water in Carboniferous-Jurassic formations and seepage water from the Fenhe River.  相似文献   

18.
The following conclusions can be drawn from the work reported in this paper:
  1. Sixteen samples were determined for uranium by spectrophotometric method. The uranium content in the sea floor sediments of the Bohai Gulf ranges from 1.6 to 6.3 ppm, with an average of 4.3 ppm.
  2. Statistical data show close relationship between U concentration and grain size. Relatively larger amount of uranium was found accumulated in mud than in sand. The bulk of uranium is assumed to be derived from terrestrial detrital minerals.
  3. A positive correlation between U and Fe is recognized. Similar relation also can be seen between U and Al. The plot of U concentration vs. Fe is linear, and can be expressed by the linear regression equation:Y=?0.37+1.35X. The plot of U against Al gives an equation ofY=?2.48+1.01X.
  4. The average U/Corg. ratio for these sediments is 7×10?4, and the average ratios of U/P, U/Mn, and U/CaCO3 are 100×10?4, 50×10?4 and 2×10?4, respectively.
  5. Compared with the abundances of other shelf sediments, the average concentration of U in the area under consideration is close to that of sediments on the selves of Japan and the Gulf of Mexico, and the Black Sea. Uranium concentration in the Bohai Gulf sediments is comparable to that of the continental crust, but differs from that of deep-sea clay.
  相似文献   

19.
Perchlorate and iodide concentrations were determined in brown (Undaria pinnatifida and Laminaria japonica) and red (Porphyra sp.) edible seaweeds, which are commonly consumed by Korean people, with the use of ion chromatography, coupled with a tandem mass spectrometer. Seaweeds (i.e., good sources of iodine) are among the most important plant life in the ocean and commonly consumed as food and nutritional supplement in South Korea. All seaweed samples were purchased from different regions in South Korea. The detected concentrations of perchlorate were as follows: 19.7–620.7 μg kg?1 dry weight (n = 11, mean concentration = 149.2 μg kg?1 dry weight) for L. japonica and 7.3–21.7 μg kg?1 dry weight (mean concentration = 10.6 μg kg?1 dry weight) for U. pinnatifida. Of the 11 samples of Porphyra sp., only 1 sample showed 6.7 μg kg?1 dry weight perchlorate. The concentrations of iodide in all seaweed samples varied from 0.44 to 6,800 mg kg?1 dry weight. L. japonica samples (n = 11) had significantly higher iodide concentrations, with a mean of 5,261 mg kg?1 dry weight. The bioconcentration factor values for perchlorate and iodide in the three different seaweeds varied widely and showed similar variation trends. The trend for perchlorate and iodide was Porphyra sp. < U. pinnatifida < L. japonica. The results have provided growing evidence that perchlorate frequently occurs in food products.  相似文献   

20.
This study presents the temporal and spatial variability of 234U/238U activity ratios in the Shu River and provides interpretation to explain the downstream changes of uranium and the 234U/238U activity ratios in the study area. The positive linear correlation (R 2 = 0.98, p < 0.001) between uranium concentration and specific electrical conductance is consistent with rock weathering and leaching as the major contributor of dissolved uranium in the studied area of the river. The 234U/238U activity ratio ranged between ~1.6 in the upper reaches of the river to ~1.15 furthest downstream. Activity ratios at specific sampling points do not show significant seasonal variability.  相似文献   

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