Fate of HTO following its acute soil deposition at different growth stages of Chinese cabbage

Lysimeter experiments were carried out in a greenhouse to study the fate of HTO following its soil deposition at different growth stages of Chinese cabbage. An HTO solution was applied to the surface of an acidic sandy soil at a time before, and four different times after, sowing. The transfer of HTO to the plants was quantified with the areal transfer factor (TFa, m2 kg(-1)-fresh) defined as the ratio of the plant concentration at harvest to the areal activity deposition. In the four post-sowing applications, the TFa values were in the ranges of 1.6 x 10(-5)-4.9 x 10(-3) for TFWT and 4.5 x 10(-6) -4.3 x 10(-5) for OBT, increasing with a decrease in the time interval between application and harvest. In the pre-sowing application, which was followed by a soil mixing, the TFa values for TFWT and OBT were 1.3 x 10(-4) and 8.6 x 10(-6), respectively. One week after harvest, soil samplings were made for the applications at 26 (A(26)) and 63d (A(63)) after sowing. Peaks of the depth profiles of the soil HTO appeared in the 10-15 cm layer for A(26) and the 5-10 cm layer for A(63). The top 30 cm of soil contained 0.5% and 20% of the applied activity for A(26) and A(63), respectively. Negligible fractions seemed to be in the deeper zone. It was estimated that almost all or most of the applied HTO had escaped to the air before plants' harvest.     

Tritium levels in Chinese cabbage and radish plants acutely exposed to HTO vapor at different growth stages

To simulate an acute exposure of Chinese cabbage and radish plants to airborne HTO, the potted plants were exposed to HTO vapor under semi-outdoor conditions for 1h at different times from the early to late growth stages. The plants were grown outdoors and the plant tritium was measured at the end of an exposure (h(0)) and at harvest. The leaf tissue free water tritium (TFWT) concentrations at h(0) were considerably lower than estimated equilibrium concentrations. In the leaves of Chinese cabbage, the exposure at the earlier growth stage generally ended with a higher TFWT concentration. Such a tendency was not apparent either in the leaves or roots of radish. On the other hand, the earlier stage exposure gave rise to lower TFWT concentrations at the harvest of both crops. For the OBT (organically bound tritium), however, the same occurred only in the Chinese cabbage leaves. During the period between the exposure and harvest, the TFWT concentrations reduced by factors of up to 1.1 x 10(6) for the Chinese cabbage leaves and 1.3 x 10(4) for the radish roots. Based on the activity ratios of OBT to TFWT at harvest, it is estimated that OBT mostly contributes much more to the ingestion dose than TFWT does.     

Synergy of Sentinel-2A and Near-proximal sensor data for deriving biochemical parameters of paddy at different growth stages

Environment, Development and Sustainability - The biochemical parameters (i.e. chlorophyll and nitrogen content) of crops are essential to evaluate the health status and to monitor crop growth. The...     

Transfer of 137Cs to rice plants from various paddy soils contaminated under flooded conditions at different growth stages

Soil blocks from 18 paddy fields around three Korean nuclear power plant sites were put into lysimeters. Greenhouse experiments were carried out to investigate the (137)Cs transfer from these paddy soils to rice plants for its deposition at different growth stages. A solution of (137)Cs was applied to the flooded lysimeters at 2-3 different stages. The applied (137)Cs was mixed with the topsoil only at the pre-transplanting application. The transfer was quantified with a transfer factor based on the unit-area deposition (TF(a), m(2)kg(-1)-dry). The TF(a) in the pre-transplanting application showed a remarkable variation with the soils. However, the differences in the mean values among the study sites were not statistically significant. The straw TF(a) was 2-3 times higher than the corresponding seed value. The early-tillering stage and booting stage applications resulted in a higher transfer than the pre-transplanting application by factors of, on an average, 2 and 16 for the straws, and 3 and 25 for the hulled seeds, respectively. The (137)Cs transfer was found to correlate negatively with the soil pH and positively with the organic matter content. Based on the present results, the representative (137)Cs TF(a) values for the rice are proposed for use in the whole of Korea for the deposition at three different growth stages.     

Optimizing different adaptive strategies by using crop growth modeling under IPCC climate change scenarios for sustainable wheat production

Environment, Development and Sustainability - Crop production is highly sensitive to climate. It is affected by long-term trends in average rainfall and temperature, inter-annual climate...     

Assessment of plant uptake of radioactive nickel from soils

As a result of isotopic dilution, the availability to plants of radioisotopes introduced into the soil solution should be directly related to the size of the isotopically exchangeable pool (E(t))-value). This work was undertaken to test this hypothesis for the radionuclide 63Ni. The demonstration was based on pot experiments conducted with seven soils representing a large range of Ni content (from 9.9 mg kg(-1) to 862.6 mg kg(-1)) which were mixed with a 63NiCl2 solution (100 kBq kg(-1)). Three plant species varying in Ni uptake, Triticum aestivum (wheat), Trifolium pratense (clover), and the Ni-hyperaccumulator Alyssum murale, were grown for 90 d, and their total Ni and 63Ni content determined at harvest. In parallel, the isotopically exchangeable kinetics method (IEK) was run on each soil sample to measure the E(t)-value. Results showed that plant uptake of radioactive nickel was negatively correlated with the E(t)-value with wheat and clover as a result of the dilution of 63Ni added in the isotopically exchangeable pool of soil Ni (alpha=5%); correlation was positive with the A. murale (alpha=10%). Hence, this provides a new approach for the assessment of soil-to-plant transfer of 63Ni at larger scale avoiding the carrying out of time consuming experiments.     

Characteristics of stone moroko population dynamics at different stages of naturalization in lake- and steam-type Dnieper reservoirs

The probable source of stone moroko, Pseudorasbora parva (Temminck & Schlegel, 1846), populations in lake- and stream-type Dnieper reservoirs was revealed. The dynamics and specific growth rates of these populations over 20 years were analyzed. The dynamic phase portrait method was used to determine the timing of stages in the process of invader naturalization and the periods when its populations were in equilibrium. The potential growth rates of P. parva populations in the Kremenchug and Dneprodzerzhinsk reservoirs were estimated.     

Soil availability,plant uptake and soil to plant transfer of 99Tc--a review

The fission yield of 99Tc from 239Pu and 235U is similar to that of 137Cs or 90Sr and it is therefore an important component of nuclear weapons fall-out, nuclear waste and releases from nuclear facilities. There is particular current interest in 99Tc transfer from soil to plants for: (a) environmental impact assessments for terrestrial nuclear waste repositories, and (b) assessments of the potential for phytoextraction of radionuclides from contaminated effluent and soil. Vascular plants have a high 99Tc uptake capacity, a strong tendency to transport it to shoot material and accumulate it in vegetative rather than reproductive structures. The mechanisms that control 99Tc entry to plants have not been identified and there has been little discussion of the potential for phytoextraction of 99Tc contaminated effluents or soil. Here we review soil availability, plant uptake mechanisms and soil to plant transfer of 99Tc in the light of recent advances in soil science, plant molecular biology and phytoextraction technologies. We conclude that 99Tc might not be highly available in the long term from up to 50% of soils worldwide, and that no single mechanism that might be easily targeted by recombinant DNA technologies controls 99Tc uptake by plants. Overall, we suggest that Tc might be less available in terrestrial ecosystems than is often assumed but that nevertheless the potential of phytoextraction as a decontamination strategy is probably greater for 99Tc than for any other nuclide of radioecological interest.     

Soil transport and plant uptake of radio-iodine from near-surface groundwater

This paper describes a 12-month experiment designed to study the extent of upward migration of (125)I (as a surrogate for (129)I) from near-surface groundwater, through a 50-cm column of soil and into perennial ryegrass. The water table was established at a depth of 45 cm below the soil surface. By 3 months, (125)I had migrated about half way up the soil column. After this, it tended to accumulate just above this mid-point, with only very small amounts being transported to the upper 20 cm of soil. This behaviour seemed to be explained well by soil moisture and redox conditions. The experiment indicated that (125)I was mobile only within the saturated/low redox zone at the base of the soil column and accumulated in the zone of transition between anoxic and oxic soil conditions. Uptake of (125)I by the ryegrass was found to be low.     

Soil migration and plant uptake of technetium from a fluctuating water table

Soil columns (50x15 cm) were used to determine the potential for 95mTc (as a surrogate for 99Tc which is an important component of some radioactive waste) to migrate from a contaminated, fluctuating water table, through sandy loam soil and into perennial ryegrass. Upward migration was significantly retarded with, generally, only the bottom few centimetres of soil becoming contaminated over the 6 months of the experiment. This is thought to have been due to the presence of anoxic conditions within the water table leading to the reduction of pertechnetate to Tc(IV) species which are relatively insoluble. However, some evidence of very slow upward migration over time was found. Only a small and inconsistent transfer of activity into the perennial ryegrass was observed. Whilst these observations would suggest that 99Tc is less important than radionuclides such as 129I and 36Cl in terms of the risk associated with radioactive waste disposal, the potential for a slow upward migration, and/or a pulse-release following the re-oxidation of reduced soil in which 99Tc has accumulated should not be overlooked.     

Removal of NOM in the different stages of the water treatment process

Natural organic matter (NOM) is abundant in natural waters in Finland and in many ways affects the unit operations in water purification. In this study, the organic matter content in water in different stages of a full-scale treatment process over 1 year was measured. The full-scale treatment sequence, studied at the Rusko water treatment plant in Tampere, Finland, consisted of coagulation, flocculation, clarification by sedimentation or flotation, activated carbon (AC) filtration, and disinfection. High-performance size exclusion chromatography (HPSEC) was used for separation to determine changes in the humic substances content during the purification process. In addition, total organic carbon (TOC), KMnO4-number, and UV-absorbance at wavelength 254 nm (UV254) were measured. High molecular weight (HMW) matter was clearly easier to remove in coagulation and clarification than low molecular weight (LMW) matter. Furthermore, depending on the regeneration of the activated carbon filters, activated carbon filtration was effective to a degree but did not remove most of the lowest molecular weight compounds. Significant correlation was established among HPSEC, KMnO4, UV254 absorbance, and TOC. HPSEC proved to be a fast and relatively easy method to estimate NOM content in water and, in fact, gave more information than traditional methods on the type of NOM in a water sample. It also helped the process performance follow-up.     

Effects of forms and rates of potassium fertilizers on cadmium uptake by two cultivars of spring wheat (Triticum aestivum, L.)

A greenhouse pot experiment was conducted to study the influence of potassium fertilizers in different forms and rates on cadmium (Cd) uptake by two cultivars of spring wheat (Triticum aestivum, L.): Brookton and Krichauff. Potassium fertilizers were added to soil at four levels: 0, 55, 110 and 166 mg K kg(-1) soil as KNO(3) (N), KCl (C) or K(2)SO(4) (S). CdCl(2) was added to all the treatments at a uniform rate equivalent to 15 mg Cd kg(-1) soil. Plant shoot and root dry weights (DW) of both cultivars were reduced significantly by the addition of K-fertilizer in C and S treatments but there were only marginal changes in the N treatments. The Cd concentrations in shoots and whole plants increased significantly (P<.001) with increasing K addition, from 37.5 to 81.4 mg kg(-1) and from 42.9 to 86.8 mg kg(-1) for Brookton and Krichauff, respectively. However, no obvious effect was observed in the N treatments, except for the highest K level (K3) where there was a sharp increase in Cd concentration compared to the lower additions. Forms of K-fertilizers significantly influenced the Cd concentrations in plant shoots and roots (P<.001), but there was no significant difference between C and S treatments. This experiment showed that anions Cl(-) and SO(4)(2-) increase Cd uptake by plants, which can be interpreted as Cl(-) and SO(4)(2-) complexing readily with Cd(2+) and thereby increasing the bioavailability of Cd(2+) in soils. The effect of potassium itself on plant uptake of Cd was also observed. We suggest that when applying potassium fertilizer to Cd-contaminated soils, the forms and rates should be considered.     

Environmental and lifestyle factors affect benzene uptake biomonitoring of residents near a petrochemical plant

Background

We monitored urinary benzene excretion to examine factors affecting benzene uptake in a sample of the general population living near a petrochemical plant.

Methods

Our study population included 143 subjects: 33 petrochemical plant workers (W) with low level occupational benzene exposure; 30 residents in a small town 2 km from the plant (2kmR); 26 residents in a second small town located 2 to 4 km from the plant (4kmR); and 54 urban residents 25 km from the plant (25kmR). Exposure to benzene was evaluated by personal air sampling during one work-shift for the W group, and from 8.00 to 20:00 for general population subgroups, and by urinary benzene (BEN-U).

Results

Median airborne benzene exposure was 25, 9, 7 and 6 μg/m³ benzene among the W, 2kmR, 4kmR, and 25kmR subgroups, respectively; the highest level was found among the workers, while there was no significant difference among the other groups. Median BEN-U was 2 to 14-fold higher in smokers compared to non-smokers; among non-smokers BEN-U was the highest in W (median 236 ng/L), and lower in the 2kmR (48 ng/L) and 4kmR (63 ng/L) subgroups than in the 25kmR (120 ng/L) subgroup. A multiple linear regression analysis, explaining up to 73% of BEN-U variability, confirmed that active smoking and airborne benzene most strongly affected BEN-U. Among the non-smoking, non-occupationally exposed study subjects, a positive association was found between BEN-U and the distance of residence from the plant. This association was explained by increased exposure to urban traffic emissions in the study group residing at a greater distance from the plant. Environmental tobacco smoke had a marginally positive role.

Conclusion

Among factors affecting benzene uptake in non-occupationally exposed individuals, urban residence contributes to benzene exposure more than residing in close proximity to a petrochemical plant.     

Natural radioactivity, dose assessment and uranium uptake by agricultural crops at Khan Al-Zabeeb, Jordan

Khan Al-Zabeeb, an irrigated cultivated area lies above a superficial uranium deposits, is regularly used to produce vegetables and fruits consumed by the public. Both soil and plant samples collected from the study area were investigated for their natural radioactivity to determine the uranium uptake by crops and hence to estimate the effective dose equivalent to human consumption. Concentrations of (238)U, (235)U, (232)Th, (226)Ra, (222)Rn, (137)Cs and (40)K in nine soil profiles were measured by gamma-ray spectrometry whereas watermelon and zucchini crops were analyzed for their uranium content by means of alpha spectrometry after radiochemical separation. Correlations between measured radionuclides were made and their activity ratios were determined to evaluate their geochemical behavior in the soil profiles. Calculated soil-plant transfer factors indicate that the green parts (leaves, stems and roots) of the studied crops tend to accumulate uranium about two orders of magnitude higher than the fruits. The maximum dose from ingestion of 1 kg of watermelon pulp was estimated to be 3.1 and 4.7 nSv y(-1) for (238)U and (234)U, respectively. Estimations of the annual effective dose equivalent due to external exposure showed extremely low values. Radium equivalent activity and external hazard index were seen to exceed the permissible limits of 370 Bq kg(-1) and 1, respectively.     

A comparison of the soil migration and plant uptake of radioactive chlorine and iodine from contaminated groundwater

A 6-month soil column experiment was conducted to compare the upward migration and plant uptake of radiochlorine and radioiodine from shallow, near-surface contaminated water tables. Both fixed and fluctuating water tables were studied. After 6 months, (36)Cl activity concentrations were relatively uniform throughout the soil profile apart from an accumulation at the soil surface, which was especially marked under a fluctuating water table scenario. In contrast, (125)I (a surrogate for (129)I) tended to accumulate at the boundary between the anoxic conditions at the base of the column and the oxic conditions above, due to its redox-dependent sorption behaviour. The uptake of (36)Cl by perennial ryegrass was much greater than that of (125)I due to its greater migration into the rooting zone and its ready availability in soil solution. In the context of radioactive waste disposal, where these radionuclides may potentially be released into groundwater, (36)Cl would be expected to present a greater potential for contamination of the biosphere than (129)I.     

The influence of benzo(a)pyrene on the growth of wheat and corn

Corn seeds responded to soaking in aqueous solutions of benzo(a)pyrene with increased root growth. Growth stimulation decreased from 14% to 0 with increasing concentrations (0.0005–0.02 ppm), and with increasing soaking times (6 and 12 hr). Shoot growth and dry weights of shoots were not affected. Wheat did not respond as distinctly as corn to similar treatments. A decrease in the growth of shoots and roots with increasing BaP concentrations was not statistically significant.     

Responses of reproduction and important value of dominant plant species in different plant functional type in Kobresia meadow to temperature increase

Responses of reproduction and IV (important value) of dominant plant species in different PFT to warming were studied at a Kobresia meadow in the Tibetan Autonomous State of Qinghai Province, China (37°29′–37°45′ N, 101°12′–101°33′ E, 3900 m asl) using the temperature gradient method formalized by the ITEX. Responses of Elymus nutans and Poa pratensis (Gramineous PFT) to increasing temperature were similar. The numbers of tillers, buds and IV increased in the chambers treated with higher temperature compared to the control without treatments (CK). Responses of Kobresia humilis and Carex alrofusca (Cyperaceae PFT) to increasing temperature were different, that is, the numbers of tillers and IV reached the maximum in different temperature among species, the numbers of buds decreased with the temperature increasing. The number of buds and IV of Lagotis brachystachya (Forbs PFT) decreased with the warming, but the number of stolons was initially large, and then decreased with increasing temperature. The number of buds of Ranunculus brotherusii (Forbs PFT) increased with the temperature increasing in the first year, but decreased in the second year; and IV decreased with the temperature warming. Under conditions of continued warming in the future, PFT structure will be significantly changed, Cyperaceae PFT dominant plant species original position will be replaced by Gramineae PFT dominant plant species. Cyperaceae plants will become the dominant species, and some species belonging to Forbs PFT will be eliminated from the community.     

Availability and plant uptake of heavy metals from contaminated dredged material placed in flooded and upland disposal environments

The availability and plant uptake of heavy metals was evaluated from contaminated dredged material placed in flooded and upland disposal environments using a solid-phase plant bioassay. The objective of the study was to verify previous dredged material research results and to develop a plant bioassay procedure that could indicate phytotoxicity and bioaccumulation of heavy metals in contaminated dredged material. The plant bioassay indicated more uptake and bioaccumulations of cadmium and, to a lesser extent, zinc when contaminated dredged material was placed in an upland environment where the sediment was allowed to air-dry. Placing the contaminated dredged material in a flooded (reduced) environment lowered the availability and plant uptake of cadmium and, to a lesser extent, zinc. Factors that influenced the availability and plant uptake of heavy metals from contaminated sediments included sediment oxidation-reduction potential, organic matter content, total sulfur content, and pH. The plant bioassay showed phytotoxicity and bioaccumulation of arsenic under a flooded environment. Placing the arsenic-contaminated sediment in an upland environment reduced both the phytotoxicity and bioaccumulation of arsenic in the freshwater marsh plant Cyperus esculentus.     

Environmental processes affecting plant root uptake of radioactive trace elements and variability of transfer factor data: a review

Soil-to-plant transfer factors are commonly used to estimate the food chain transfer of radionuclides. Their definition assumes that the concentration of a radionuclide in a plant relates linearly solely to its average concentration in the rooting zone of the soil. However, the large range of transfer factors reported in the literature shows that the concentration of a radionuclide in a soil is not the only factor influencing its uptake by a plant. With emphasis on radiocesium and -strontium, this paper reviews the effects of competition with major ions present in the soil-plant system, the effects of rhizosphere processes and soil micro-organisms on bioavailability, the factors influencing transport to and uptake by roots and the processes affecting long-term uptake rates. Attention is given to summarizing the results of recent novel electrophysiological and genetic techniques which provide a physiologically based understanding of the processes involved in the uptake and translocation of radiocesium and -strontium by plants.