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.     

Tissue free water tritium and organically bound tritium in the rice plant acutely exposed to atmospheric HTO vapor under semi-outdoor conditions.

Potted rice plants were exposed to atmospheric HTO in a box outdoors for 1 h at 9 different times from booting to yellow-ripe stages. It is indicated that the leaf TFWT concentration may reach equilibrium within 1 h in clear weather. The plant TFWT concentration decreased at a rapid rate for the first several hours and at a much slower rate thereafter. The decrease till harvest was by factors of 600-95,000 depending on the plant parts and exposure times. The time course of the ear OBT concentration was characterized by the exposure time. After exposure at the booting to heading stages, the leaf OBT concentration decreased rapidly for the first several hours and then very slowly. The plant OBT concentration was initially about 2 orders of magnitude lower, but at harvest an order of magnitude higher, than the TFWT concentration. The OBT concentration in hulled seeds at harvest varied with exposure times by a factor of 70, being highest in the exposure performed at the earlier stage of rapid grain growth. Also in this exposure, the plant total OBT was greatest due to the seed OBT.     

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.     

Uptake of deuterium by dead leaves exposed to deuterated water vapor in a greenhouse at daytime and nighttime

Dead leaves were exposed to deuterated water vapor (D(2)O) as a substitute of tritiated water (HTO) in a greenhouse at daytime and nighttime to examine uptake and release of tritium by dead leaves because they cover a wide area of the forest floor and are therefore a major target material to be exposed when HTO is atmospherically derived to the forest. The dead cedar needles showed faster uptake and faster release rates during and after the exposure than the fresh ones, and the equilibrium concentration of the dead cedar needles was about two times higher than the fresh ones, indicating a quick response and a high buffering potential of dead leaves. The relation between uptake of D(2)O and number of stoma was examined for dead deciduous leaves; the species with larger number of stoma accumulated more D(2)O at the daytime and nighttime exposures. However, drying of the dead leaves suppressed D(2)O uptake greatly at daytime, suggesting stomata's opening and closing controls the D(2)O uptake of dead leaves.     

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...     

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.     

Elevated levels of PFOS and PFHxS in firefighters exposed to aqueous film forming foam (AFFF)

Exposure to aqueous film forming foam (AFFF) was evaluated in 149 firefighters working at AFFF training facilities in Australia by analysis of PFOS and related compounds in serum. A questionnaire was designed to capture information about basic demographic factors, lifestyle factors and potential occupational exposure (such as work history and self-reported skin contact with foam). The results showed that a number of factors were associated with PFAA serum concentrations. Blood donation was found to be linked to low PFAA levels, and the concentrations of PFOS and PFHxS were found to be positively associated with years of jobs with AFFF contact. The highest levels of PFOS and PFHxS were one order of magnitude higher compared to the general population in Australia and Canada. Study participants who had worked ten years or less had levels of PFOS that were similar to or only slightly above those of the general population. This coincides with the phase out of 3M AFFF from all training facilities in 2003, and suggests that the exposures to PFOS and PFHxS in AFFF have declined in recent years. Self-reporting of skin contact and frequency of contact were used as an index of exposure. Using this index, there was no relationship between PFOS levels and skin exposure. This index of exposure is limited as it relies on self-report and it only considers skin exposure to AFFF, and does not capture other routes of potential exposure. Possible associations between serum PFAA concentrations and five biochemical outcomes were assessed. The outcomes were serum cholesterol, triglycerides, high-density lipoproteins, low density lipoproteins, and uric acid. No statistical associations between any of these endpoints and serum PFAA concentrations were observed.     

Measured and modelled tritium concentrations in freshwater Barnes mussels (Elliptio complanata) exposed to an abrupt increase in ambient tritium levels

To improve understanding of environmental tritium behaviour, the International Atomic Energy Agency (IAEA) included a Tritium and C-14 Working Group (WG) in its EMRAS (Environmental Modelling for Radiation Safety) program. One scenario considered by the WG involved the prediction of time-dependent tritium concentrations in freshwater mussels that were subjected to an abrupt increase in ambient tritium levels. The experimental data used in the scenario were obtained from a study in which freshwater Barnes mussels (Elliptio complanata) were transplanted from an area with background tritium concentrations to a small Canadian Shield lake that contains elevated tritium. The mussels were then sampled over 88 days, and concentrations of free-water tritium (HTO) and organically-bound tritium (OBT) were measured in the soft tissues to follow the build-up of tritium in the mussels over time.The HTO concentration in the mussels reached steady state with the concentration in lake water within one or two hours. Most models predicted a longer time (up to a few days) to equilibrium. All models under-predicted the OBT concentration in the mussels one hour after transplantation, but over-predicted the rate of OBT formation over the next 24 h. Subsequent dynamics were not well modelled, although all participants predicted OBT concentrations that were within a factor of three of the observation at the end of the study period. The concentration at the final time point was over-predicted by all but one of the models. The relatively low observed concentration at this time was likely due to the loss of OBT by mussels during reproduction.     

Accumulation of (137)Cs in Brazilian soils and its transfer to plants under different climatic conditions

The spatial distribution and behaviour of the global fallout (137)Cs in the tropical, subtropical and equatorial soil-plant systems were investigated at several upland sites in Brazil selected according to their climate characteristics, and to the agricultural importance. To determine the (137)Cs deposition density, undisturbed soil profiles were taken from 23 environments situated between the latitudes of 02 degrees N and 30 degrees S. Sampling sites located along to the equator exhibited (137)Cs deposition densities with an average value of 219Bqm(-2). Extremely low deposition densities of 1.3Bqm(-2) were found in the Amazon region. In contrast, the southern part of Brazil, located between latitudes of 20 degrees S and 34 degrees S, exhibited considerably higher deposition densities ranging from 140Bqm(-2) to 1620Bqm(-2). To examine the (137)Cs soil-to-plant transfer in the Brazilian agricultural products, 29 mainly tropical plant species, and corresponding soil samples were collected at 43 sampling locations in nine federal states of Brazil. Values of the (137)Cs concentration factor plant/soil exhibited a large range from 0.020 (beans) to 6.2 (cassava). Samples of some plant species originated from different collecting areas showed different concentration factors. The (137)Cs content of some plants collected was not measurable due to a very low (137)Cs concentration level found in the upper layers of the incremental soils. Globally, the soil-to-plant transfer of (137)Cs can be described by a logarithmic normal distribution with a geometric mean of 0.3 and a geometric standard deviation of 3.9.     

Mercury and docosahexaenoic acid levels in maternal and cord blood in relation to segmental maternal hair mercury concentrations at parturition

Fish is a major source of harmful methylmercury (MeHg) and beneficial docosahexaenoic acid (DHA) in the developing brain. In this study, we investigated the correlations among maternal and umbilical cord (cord) MeHg and DHA levels at parturition, and mercury (Hg) concentration in 1-cm incremental segments hair samples which grew during gestation representing monthly MeHg exposure levels throughout the period. Whole blood Hg and plasma DHA levels were measured in blood sample pairs collected from 54 mothers at early gestation and parturition, and in cord blood. Maternal hair samples were collected at parturition, and Hg concentrations were measured in 1-cm incremental segments. Hg level in mothers at parturition was slightly lower than that at early gestation and the level in cord blood were approximately 1.9 times higher than that in mothers at parturition. On the other hand, DHA level in mothers at parturition was approximately 2.3 and 1.6 times higher than those in mothers at early gestation and in cord plasma, respectively. These results indicate that kinetics of these chemicals in mothers during gestation and placental transfer are completely different. However, Hg and DHA levels had significant positive correlation in fetal circulation. The cord blood Hg showed the strongest correlation with maternal hair Hg in the first 1-cm segment from the scalp at parturition (r = 0.87), indicating that fetal MeHg level reflects maternal MeHg burden at late gestation. In contrast, maternal and cord plasma DHA concentrations at parturition showed the highest correlation coefficients with Hg in the fifth (r = 0.43) and fourth (r = 0.38) 1-cm hair segments, suggesting that maternal and fetal DHA levels reflects maternal fish intake during mid-gestation.     

Selenium bioavailability and uptake as affected by four different plants in a loamy clay soil with particular attention to mycorrhizae inoculated ryegrass

The aim of this study was to investigate the influence of plant species, especially of their rhizosphere soil, and of inoculation with an arbuscular mycorrhizal (AM) fungus on the bioavailability of selenium and its transfer in soil-plant systems. A pot experiment was performed with a loamy clay soil and four plant species: maize, lettuce, radish and ryegrass, the last one being inoculated or not with an arbuscular mycorrhizal fungus (Glomus mosseae). Plant biomass and Se concentration in shoots and roots were estimated at harvest. Se bioavailability in rhizosphere and unplanted soil was evaluated using sequential extractions. Plant biomass and selenium uptake varied with plant species. The quantity of rhizosphere soil also differed between plants and was not proportional to plant biomass. The highest plant biomass, Se concentration in plants, and soil to plant transfer factor were obtained with radish. The lowest Se transfer factors were obtained with ryegrass. For the latter, mycorrhizal inoculation did not significantly affect plant growth, but reduced selenium transfer from soil to plant by 30%. In unplanted soil after 65 days aging, more than 90% of added Se was water-extractable. On the contrary, Se concentration in water extracts of rhizosphere soil represented less than 1% and 20% of added Se for ryegrass and maize, respectively. No correlation was found between the water-extractable fraction and Se concentration in plants. The speciation of selenium in the water extracts indicated that selenate was reduced, may be under organic forms, in the rhizosphere soil.