Assessment of Radionuclides, Trace Metals and Radionuclide Transfer from Soil to Food of Jhangar Valley (Pakistan) Using Gamma-Ray Spectrometry

The gamma spectrometric analysis of soil and essential foodstuffs, e.g., wheat, millet, potato, lentils and cauliflower, which form the main component of the daily diet of the local public, was carried out using high purity germanium (HpGe) detector coupled with a computer based high-resolution multi-channel analyzer. The activity concentration in soil samples for ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 30.0 Bq kg^?1 to 81.2 Bq kg^?1, 31.4 Bq kg^?1 to 78.25 Bq kg^?1 and 308.8 Bq kg^?1 to 2177.6 Bq kg^?1, with mean values of 56.2, 58.5 and 851.9 Bq kg^?1, respectively. The average activity measured for ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples was found higher than the world average. The major radionuclide found in the food items studied was ⁴⁰K, while ²²⁶Ra, ²³²Th and ¹³⁷Cs were detected in very nominal amounts. The results clearly indicate that these radionuclides have no health hazard to human beings, as they are well below the annual limit of intake (ALI) for these radionuclides. The transfer factors of these radionuclides from soil to food were also studied. The mean transfer factors of ⁴⁰K, ²²⁶Ra, ²³²Th and ¹³⁷Cs from soil to food were estimated to be about 0.17, 0.07, 0.16 and 0.23, respectively. An artificial radionuclide, ¹³⁷Cs, was also present in detectable amount in all samples. The internal and external hazard indices were measured and had mean values of 0.70 and 0.55, respectively. Absorbed dose rates and effective dose have been determined in the present study. Concentration of trace metals, such as Cr, Pb, Ni and Zn, was also determined in the soil samples. The concentrations of radionuclides and trace metals found in these samples during the present study were nominal and do not pose any potential health hazard to the general public.     

Transfer of Cd, Pb, Ra and U from Phosphogypsum Amended Soils to Tomato Plants

About 170 million tons of phosphogypsum (PG) are annually generated worldwide as a by-product of phosphoric acid factories. Agricultural uses of PG could become the main sink for this waste, which usually contains significant radionuclide (from the ²³⁸U-series) and toxic metals concentrations. To study PG effects on pollutant uptake by crops, a completely randomised greenhouse experiment was carried out growing Lycopersicum esculentum Mill L. on a reclaimed marsh soil amended with three PG rates (treatments), corresponding to zero (control without PG application), one, three and ten times the typical PG rates used in SW Spain (20 Mg ha^?1). The concentrations of Cd, Pb, U (by inductively coupled plasma mass spectroscopy) and ²²⁶Ra and ²¹⁰Po (by γ-spectrometry and α-counting, respectively) were determined in soil, vegetal tissue and draining water. Cadmium concentrations in fruit increased with PG rates, reaching 44?±?7 μg kg^?1 formula weight with ten PG rates (being 50 μg kg^?1 the maximum allowed concentration by EC 1881/2006 regulation). Cd transfer factors in non-edible parts were as high as 4.8?±?0.5 (dry weight (d.w.)), two orders of magnitude higher than values found for lead, lead, uranium and radium concentrations in fruit remained below the corresponding detection limits—0.5 and 0.25 mg kg^?1 and 0.6 mBq kg^?1, respectively (in a d.w. basis). ²³⁸U (up to 7 μg kg^?1 d.w.) and ²¹⁰Po (up to 0.74 Bq kg^?1 d.w.) could be measured in some fruit samples by α-spectrometry. Overall, the concentrations of these metals and radionuclides in the draining water accounted for less than 1% of the amount applied with PG.     

Measurement of Radionuclides and Gamma-Ray Dose Rate in Soil and Transfer of Radionuclides from Soil to Vegetation, Vegetable of Some Northern Area of Pakistan Using ��-Ray Spectrometry

The analysis of gamma emitters natural radionuclides, i.e., ²²⁶Ra, ²³²Th, and ⁴⁰K, has been carried out in soil, vegetation, vegetable, and water samples collected from some Northern area of Pakistan, using gamma-ray spectrometry. The ??-ray spectrometry was carried out using high-purity Germanium detector coupled with a computer-based high-resolution multi-channel analyzer. The activity concentrations in soil ranges from 24.7 to 78.5 Bq?kg^?1, 21.7 to 75.3 Bq?kg^?1, and 298.5 to 570.8 Bq?kg^?1 for ²²⁶Ra, ²³²Th, and ⁴⁰K with the mean value of 42.1, 43.3, 9.5, and 418.3 Bq?kg^?1, respectively. In the present analysis, ⁴⁰K was the major radionuclide present in soil, vegetation, fruit, and vegetable samples. The concentration of ⁴⁰K in vegetation sample varied from 646.6 to 869.6 Bq?kg^?1 on dry weight basis. However, the concentration of ⁴⁰K in fruit and vegetable samples varied from 34.0 to 123.3 Bq?kg^?1 on fresh weight basis. In vegetation samples, along with ⁴⁰K, ²²⁶Ra, and ²³²Th were also present in small amount. The transfer factors of these radionuclides from soil to vegetation, fruit, and vegetable were also studied. The transfer factors were found in the order: ⁴⁰K?>?²³²Th????²²⁶Ra. The analysis of water samples showed activity concentrations values for all radionuclides below detection limit. The internal and external hazard indices were measured and found less than the safe limit of unity. The mean value of outdoor and indoor absorbed dose rate in air was found 64.61 and 77.54 nGy?h^?1, respectively. The activity concentrations of radionuclides found in all samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the general public.     

Determination of Natural and Artificial Radionuclide Levels in Soils of Western and Southern Coastal Area of Turkey

Soil samples were collected from western and southern region of Turkey in 1995 from 17 sampling stations of different depths. Natural and artificial radionuclide activity levels of soil samples of the western and southern sea in Turkey were previously reported about nine years after the Chernobyl accident. The aim of the study was to collect data for following up of the earlier study and to present result for distributions of radionuclides in soil samples of the western and southern regions of Turkey. ²²⁶Ra is in the range 19–276 Bq kg^?1, 7–173 Bq kg^?1 for ²³⁸U, 8–244 Bq kg^?1 for ²³²Th, 86–1162 Bq kg^?1 (dry wt.) for ⁴⁰K and ¹³⁷Cs activity result varies between 1.8–82 Bq kg^?1 (dry wt.).     

Levels of 131I and Six Natural Radionuclides in Sludge from the Sewage Treatment Plant of Valladolid, Spain

The levels of ¹³¹I and six natural radionuclides (²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²²⁸Ra, ²²⁴Ra, and ⁴⁰K) were determined in sewage sludge samples obtained from an urban wastewater treatment plant that services a medium-sized town in Spain. Secondary treatment of wastewater consisting of anaerobic, anoxic, and oxic stages is collectively called A2O processing. Radio analytical determinations were performed by gamma spectrometry using a high-purity germanium detector. This technique has proven useful in identifying local radioactive pollution. This type of pollution was consistently detected throughout the year, with several increases associated with authorized discharges from hospitals. Finally, we examined the radiation dose that workers are exposed to due to the presence of ¹³¹I in the sludge. We found inhalation risk to be negligible, with external radiation as the main source of exposure to ¹³¹I.     

In Situ Heavy Metal Accumulation in Lettuce Growing Near a Former Mining Waste Disposal Area: Implications for Agricultural Management

Mining wastes may pose risk nearby urban and agricultural areas. We investigated a lettuce crop land close to a former capped mine tailing in order to determinate the metal uptake by crops. Soil plot sampling design within the crop area and two transects along the tailing were performed. In addition, lettuces (root and leaves) were analyzed after transplant and harvest. The results showed a pH of around 7–8 for all the soil samples. Total metal concentrations were as follows: 190–510 mg kg^?1 Pb, 13–21 mg kg^?1 Cu, and 210–910 mg kg^?1 Zn. Diethylene triamine pentaacetic acid-extractable Pb was around 18% of the total Pb in some samples. Transects along the base and on the plateau of the tailing showed high metal concentrations of Pb (up to 5,800 mg kg^?1) and Zn (up to 4,500 mg kg^?1), indicating that capping layer had been eroded. Lettuce leaves showed Pb concentrations within standard for human health (<0.3 mg kg^?1 in fresh weight). For essential micronutrients such as Cu and Zn, leaves had optimal content (10–28 mg kg^?1 Cu, 60–85 mg kg^?1 Zn). A continued monitoring in metal uptake is needed in crop lands close to mining wastes in order to prevent risks in food safety. Capped tailings must be monitored and rehabilitation works performed from time to time.     

Edaphic and physiographic factors affecting the distribution of natural gamma-emitting radionuclides in the soils of the Arnás catchment in the Central Spanish Pyrenees

Gamma‐emitting radionuclides are a natural source of radiation that can be a concern for human health, therefore it is important to know the radionuclide backgrounds in soils and to assess their mobility and transfer in ecosystems. Concentrations of natural radionuclides were determined in soils from a small catchment in the middle mountain environment of the Central Spanish Pyrenees. Radioisotope activities were well within the natural ranges for soil, averaging 27, 26, 32 and 500 Bq kg^?1 for ²³⁸U, ²²⁶Ra, ²⁰⁸Tl and ⁴⁰K, respectively. Their distributions in the soil profile were analysed along three transects of contrasting physiography and soil type. Uranium was depleted in upper layers of the soil and slightly enriched in deeper sections, while ²²⁶Ra, ⁴⁰K and ²⁰⁸Tl were more uniformly distributed. Radionuclide activities in the Calcaric Regosols on the shrub slope were less than those in the deeper and better developed Haplic Kastanozems under forest and in Calcaric Fluvisols in the valley bottom. These spatial patterns seem to be affected by the soil type; other landscape features, such as slope orientation and vegetation cover, appeared to have an indirect effect. The results indicate that the depth distribution of the radionuclides is affected by some soil properties, including pH, carbonates, organic matter and particle size, and soil processes, such as leaching and adsorption.     

Transfer of 137Cs and 40K from Agricultural Soils to Food Products in Terrestrial Environment of Tarapur, India

The ¹³⁷Cs and ⁴⁰K activities and transfer factors from soil to vegetables, grass, and milk from villages located around Tarapur Atomic Power Station (TAPS) were determined using high-resolution gamma spectrometry. A total of 32 soil, 21 vegetable, 23 dry paddy grass, and 23 milk samples were collected from 23 different agricultural farms from various villages around TAPS to determine transfer factors for natural environment. The mean concentration values for ¹³⁷Cs and ⁴⁰K in soil, grass, and milk were 2.39?±?0.86 Bq kg^?1, 0.31?±?0.23 Bq kg^?1, and 12.4?±?5.7 mBq L^?1 and 179?±?31 Bq kg^?1, 412?±?138 Bq kg^?1, and 37.6?±?9.3 Bq L^?1, respectively, for soil?Cgrass?Cmilk pathway. In the soil?Cvegetation pathway, the mean concentrations values for ¹³⁷Cs and ⁴⁰K were 2.15?±?1.04 Bq kg^?1, 16.5?±?7.5 mBq kg^?1, and 185?±?24, 89?±?50 Bq kg^?1, respectively. The evaluated mean transfer factors from soil?Cgrass, grass?Cmilk, and soil?Cvegetation for ¹³⁷Cs were 0.14, 0.0044, and 0.0073 and that of ⁴⁰K were 2.42, 0.0053, and 0.49, respectively. Only 15 out of total 44 milk and vegetable samples were detected positive for ¹³⁷Cs, indicating a very low level of bioavailability.     

Partitioning and transport of lead-210 in the Ottawa river watershed

The partitioning of ²¹⁰Pb between dissolved and the suspended sediment phases of the Ottawa River waters has been studied. The results indicate high affinity of the radionuclide for particulates (K_d, 1.9 × 10⁵ mL g^?1). Companion studies on the precursor ²²⁶Ra give an average (K_d value of 7.8 × 10³ mL g^?1). Nearly 77% of the total ²¹⁰Pb (i.e., dissolved plus particulate) and 99% of the total ²²⁶Ra are transported through the system in the dissolved form. The suggestion is made that the low availability of particulates in the system promotes the export of ²¹⁰Pb in the dissolved form. The conventional approach gives a mean residence time of about 2000 yr for the atmospherically-derived ²¹⁰Pb in the watershed. However, if the flux of this ²¹⁰Pb falling directly on the river's surface is taken into account, a mean residence time of about 6200 yr is inferred for this radionuclide in the area soils. This aspect of the study is largely applicable to metals with geochemical behavior similar to that of ²¹⁰Pb for the radionuclide itself has a mean life of only 32.2 yr.     

Radioactive Contamination of Alluvial Soils in the Taiga Landscapes of Yakutia with <Superscript>137</Superscript>Cs, <Superscript>226</Superscript>Ra,and <Superscript>238</Superscript>U

The concentrations and distribution of ¹³⁷Cs in alluvial soils (Fluvisols) of the upper and middle reaches of the Markha River in the northwest of Yakutia and ²²⁶Ra and ²³⁸U in alluvial soils within the El’kon uranium ore deposit in the south of Yakutia have been studied. It is shown that the migration of radiocesium in the permafrost-affected soils of Yakutia owing to alluviation processes extends to more than 600 km from the source of the radioactive contamination. The migration of ¹³⁷Cs with water flows is accompanied by its deposition in the buried horizons of alluvial soils during extremely high floods caused by ice jams. In the technogenic landscapes of southern Yakutia, active water migration of ²³⁸U and ²²⁶Ra from radioactive dump rocks. The leaching of ²³⁸U with surface waters from the rocks is more intense than the leaching of ²²⁶Ra. The vertical distribution patterns of ²³⁸U and ²²⁶Ra in the profiles of alluvial soils are complex. Uranium tends to accumulate in the surface humus horizon and in the buried soil horizons, whereas radium does not display any definite regularities of its distribution in the soil profiles. At present, the migration of ²³⁸U and ²²⁶Ra with river water and their accumulation in the alluvial soils extend to about 30 km from the source.     

Determination of Uranium and Thorium in Soil and Plant Parts around Abandoned Lead–Zinc–Copper Mining Area

This study reports distribution of uranium (U) and thorium (Th) in soil samples and the roots and shoots of some plants grown around an abandoned lead (Pb)–zinc (Zn)–copper (Cu) mining area. The plants Euphorbia macroclada, Verbascum cheiranthifolium Boiss, and Astragalus gummifer were examined. The determinations of U and Th were carried out by inductively coupled plasma‐mass spectrometry (ICP‐MS). Uranium and Th levels of the studied soil samples were found to be in the range of 1.1–70.3 mg kg^?1 and 2.1–62.1 mg kg^?1, respectively. Some results obtained from this study were higher than the mean U and Th concentrations of soils reported around the world. Uranium and thorium concentrations in studied plant roots were in the range of 0.04–16 and 0.08–14.57 mg kg^?1, whereas in plant shoots they were 0.02–2.76 and 0.07–12.3 mg kg^?1, respectively. It was concluded that the shoots of Astragalus and roots of Euphorbia and Verbascum can be used as both a biomonitor for environmental pollution and biogeochemical indicator because of their higher U and Th concentrations.     

Chelate-enhanced phytoextraction and phytostabilization of lead-contaminated soils by carrot (Daucus carota)

The objective of this study was to study the influence of different ethylenediamine tetraacetate (EDTA), nitrilotriacetic acid (NTA) and oxalic acid (HOx) concentrations on tolerance and lead (Pb) accumulation capacity of carrot (Daucus carota). The results indicated that by increasing Pb, NTA and HOx concentrations in the soil, the shoot, taproot and capillary root dry matters increase effectively. In contrary, EDTA caused to reduce capillary roots biomass. EDTA was more effective than NTA and HOx in solubilizing soil Pb. The highest Pb content in shoots (342.2 ± 13.9 mg kg^?1) and taproots (301 ± 15.5 mg kg^?1) occurred in 10 mM EDTA, while it occurred for capillary roots (1620 ± 24.6 mg kg^?1) in 5 mM HOx, when the soil Pb concentration was 800 mg kg^?1. The obtained high phytoextraction and phytostabilization potentials were 1208 (±25.6) and 11.75 (±0.32) g Pb ha^?1 yr^?1 in 10 mmol EDTA kg^?1 soil and no chelate treatments, respectively. It may be concluded that chelate application increases Pb uptake by carrots. Consequently, this plant can be introduced as a hyperaccumulator to phytoextract and phytostabilize Pb from contaminated soils.     

Transfer of radiocesium from hydroponic medium to potherb mustard and tomato plants

Abstract

Potherb mustard (Brassica rapa var. nipposinica) and tomato plants (scion, ‘CF Momotaro haruka’; rootstock, ‘Dokutar K’; Solanum lycopersicum) were cultured in hydroponic medium containing cesium-137 (¹³⁷Cs) at three different concentrations (0.03, 0.13 and 1.03 Bq L^?1), and uptake of ¹³⁷C into the plants was determined. When the ¹³⁷Cs radioactivity concentration in the medium was 1.03 Bq L^?1, the ¹³⁷Cs radioactivity concentrations in the edible portions of the plants were 4.80 Bq kg^?1 fresh weight for the potherb mustard plants and 3.60 Bq kg^?1 fresh weight for the tomato plants. In both species, the ¹³⁷Cs radioactivity concentration in the edible portions decreased with decreasing ¹³⁷Cs radioactivity concentration in the culture medium. When the ¹³⁷Cs radioactivity concentration in the medium was 0.03 Bq L^?1, a concentration observed in many streams and in tap water in Fukushima Prefecture after the accident at the Fukushima Daiichi Nuclear Power Plant, the ¹³⁷Cs radioactivity concentrations in the edible portions of the plants were 0.50 and 0.15 Bq kg^?1 fresh weight for potherb mustard and tomato plants, respectively. These values are less than the Japanese allowable limit for radiocesium in food. For both species, the transfer factors for ¹³⁷Cs uptake from the culture media to the edible portions and the average transfer rates over the cultivation period were calculated.     

Radioactivity and chemical characteristics of Alberta phosphogypsum

Gypsum based by-products of phosphate fertilizer production, termed phosphogypsum (PG), are stockpiled at numerous locations worldwide. Although dominated by gypsum, PG contains accessory minerals, trace elements, and radionuclides. This study was conducted to characterize the composition and pore water chemistry of PG samples from a plant site in southern Alberta, Canada. Pore water chemistry was studied by equilibrating PG with deionized water for 80 days; the aqueous phase was then analyzed for dissolved constituents. The PG samples had pH levels of 4.0 or lower and contained gypsum and minor amounts of quartz, phosphate rock and sodium feldspar. The PG was elevated in total content of Ag, Au, Ca, Cd, P, S, Se, Sr, U and some of the light rare earth elements and Y relative to shale. Average ²²⁶Ra activity, determined by the radon emanation method, was 890 Bq kg^?1. Activity of ²¹²Pb, in equilibrium with ²²⁸Th, was 5.8 Bq kg^?1. Pore water concentrations of As, Cd, Cr, Cu, Fe, Mn, Na, NO₃ ^?-N, Se, SO₄ ^2?-S, and Zn exceeded drinking water standards in some PG samples. Although closer to flue gas desulfurization sludge in mineralogy, the pore water chemistry of PG is more like that of some fly ashes.     

Evaluation of Pb Phytoremediation Potential in Buddleja asiatica and B. paniculata

The phytoremediation potential for Pb of Buddleja asiatica (a wild species) and a closely related cultivated species, B. paniculata, was investigated by means of field survey, hydroponic and pot experiments, and field trial experiments. Field surveys showed that B. asiatica had an extraordinary accumulation capacity and tolerance for Pb. Plants grown in soil with 2,369.8–206,152 mg kg^?1 total Pb accumulated 1,835.5–4,335.8 mg kg^?1 Pb in their shoots. Under hydroponic conditions (10, 20 mg l^?1 Pb), both B. asiatica and B. paniculata showed unusually high concentrations of Pb in their roots (12,133–21,667 mg kg^?1) and increased biomass production. A pot experiment in a greenhouse without any soil amendments was conducted on three different soils with various Pb contents (10,652, 31,304, 89,083 mg kg^?1) for 3 months. The results showed that both species of Buddleja had an increase in the biomass similar to the control plants. There was a slight decrease in survival rates of plants grown in soil with 89,083 mg kg^?1 Pb content. A field trial experiment was conducted for 6 months at three sites around the Pb mine area in which plants were provided with Osmocote fertilizer. Both Buddleja species showed 100% survival, increased biomass production and phytoextraction capacity (TF 1.1–2.3) when grown in soil with Pb content of 94,584–101,405 mg kg^?1. Plants accumulated 2,273–3,675 mg kg^?1 Pb in their shoots. The results suggest these Buddleja plants are suitable for use in the phytoremediation of Pb-contaminated soil.     

Effect of Ectomycorrhiza on Cu and Pb Accumulation in Leaves and Roots of Silver Birch (Betula pendula Roth.) Seedlings Grown in Metal-Contaminated Soil

A pot experiment was conducted to study the effects of high concentrations of available Cu and Pb in soil originated from the vicinity of a copper foundry in Poland (Cu, 2,585–3,725 mg kg^?1 d.wt.; Pb, 1,459–1,812 mg kg^?1 d.wt.) on the growth and chemical constituents of Betula pendula seedlings. Control plants grew in unpolluted forest soil. Dry matter accumulation in the plants during the growing season and root/leaf mineral content were determined. Colonization of birch roots by ectomycorrhizal (ECM) fungi also was evaluated, as was soil dehydrogenase activity for influence of the metals on soil microorganisms. The heavy metals negatively affected seedling growth, ECM colonization, and soil dehydrogenase activity. A reverse relationship was found between ECM abundance and heavy metal concentrations in birch leaves, indicating the potential of mycorrhizas to protect the aboveground part of young silver birch seedlings from elevated environmental levels of Cu and Pb.     

Removal of Lead from Contaminated Soils by Typha Angustifolia

A greenhouse study was demonstrated for removal of lead (Pb) from contaminated soil by the narrow — leaved cattail, Typha angustifolia. The plants were grown in sandy loam soil containing various concentrations of Pb(NO₃)₂ (53.3, 106.7, 160, 213.3, and 266.7 mg Pb kg^-1 soil). Most lead was accumulated in roots and then transported to leaves. In soil contaminated with 266.7 mg kg^-1 of lead, the plants accumulated 7492.6 mg Pb kg^-1 dry weight in the roots and 167 mg Pb kg^-1 dry weight in the leaves. Yet, no growth retardation from lead was detected. T. angustifolia has high potential as a plant to clean up lead contaminated soil due to its vigorous growth, high biomass productivity, and because it is a perennial in nature. Further work is required to study on the iron plaque formation and its role in metal immobilization.     

Arsenic and heavy metal accumulation by Athyrium yokoscense from contaminated soils

Abstract

Athyrium yokoscense, a type of fern that grows vigorously in mining areas in Japan, is well known as a Cd hyperaccumulator as well as a Cu, Pb and Zn tolerant plant. However, no information is available on As accumulation of A. yokoscense, although it often grows on soils containing high levels of both heavy metals and As. In this study, young ferns collected from a mine area were grown in media containing As-spiked soils or mine soil in a greenhouse for 21 weeks. Athyrium yokosense was highly tolerant to arsenate and survived in soils containing up to 500 mg As (V) kg^?1. The addition of 100 mg As (V) kg^?1 resulted in the highest fern biomass (1.95 g plant^?1) among As-spiked soils. Although the As concentration of the fern was lower than other As hyperaccumulators, such as Pteris vittata, A. yokoscense could hyperaccumulate As in mature and old fronds. Arsenic was accumulated most efficiently in old fronds (922 mg kg^?1) in the media containing 5 mg As (III) kg^?1. Moreover, higher As accumulation was found in the roots of the ferns, with a range from 506 to 2,192 mg kg^?1. In addition, in the mine soil with elevated concentrations of As and heavy metals, A. yokoscense not only hyperaccumulated As (242 mg As kg^?1 in old fronds), but also accumulated Cd, Pb, Cu and Zn at concentrations much higher than those reported for other terrestrial plants. Athyrium yokoscense accumulated Cd mostly in fronds in high concentrations, up to 1095 mg kg^?1, while it accumulated Cu, Zn and Pb mainly in the roots and the concentrations were 375, 2040 and 1165 mg kg^?1, respectively.     

Natural radionuclides in rocks and soils of the high-mountain regions of the Great Caucasus

The results of the radioecological survey in the high-mountain regions of the Great Caucasus at the heights from 2200 to 3800 m a.s.l. are considered. This survey encompassed the territories of Dagestan, Azerbaijan, Georgia, Chechnya, Northern Ossetia-Alania, Kabardino-Balkaria, Karachay-Cherkessia, and the Stavropol and Krasnodar regions. The natural ?? background radiation in the studied regions is subjected to considerable fluctuations and varies from 6 to 40 ??R/h. The major regularities of the migration of natural radionuclides ²³⁸U, ²³²Th, ²²⁶Ra, and ⁴⁰K in soils in dependence on the particular environmental conditions (the initial concentration of the radionuclides in the parent material; the intensity of pedogenesis; the intensity of the vertical and horizontal migration; and the geographic, climatic, and landscape-geochemical factors) are discussed.     

Chelate-Assisted Phytoextraction of Cadmium and Lead using Mustard and Fenugreek

A screen-house experiment was conducted to study cadmium (Cd) and lead (Pb) phytoextraction using mustard and fenugreek as test crops. Cadmium was applied at a rate of 20 mg kg^?1 soil for both crops, and Pb was applied at 160 and 80 mg kg^?1 soil for mustard and fenugreek, respectively. The disodium salt of ethylenediamine tetraacetic acid (EDTA) was applied at 0, 0.5, 1.0, and 1.5 g kg^?1 soil. Dry-matter yield (DMY) of both crops decreased with increasing rates of EDTA application. Application of 1.5 g EDTA kg^?1 soil caused 23% and 70% declines in DMY of mustard and fenugreek shoots, respectively, in the soils receiving 20 mg Cd kg^?1 soil. Similarly, in soil with 160 mg Pb kg^?1 soil, application of 1.5 g EDTA kg^?1 resulted in 25.4% decrease in DMY of mustard shoot, whereas this decrease was 55.4% in fenugreek grown on a soil that had received 80 mg Pb kg^?1 soil. The EDTA application increased the plant Cd and Pb concentrations as well as shoot/root ratios of these metals in both the crops. Application of 1.5 g kg^?1 EDTA resulted in a 1.50-fold increase in Cd accumulation and a 3-fold increase in Pb accumulation by mustard compared to the control treatment. EDTA application caused mobilization of Cd and Pb from carbonate, manganese oxide, and amorphous iron oxide fractions, which was evident from decrease in these fractions in the presence of EDTA as compared to the control treatment (no EDTA).