Mechanistic insights into Cd(II) and As(V) sorption on Miscanthus biochar at different pH values and pyrolysis temperatures.

Biochar has received great attention as a biosorbent, but explanations of the underlying sorption mechanisms are still unclear. Here, batch sorption of cadmium (Cd(II)) and arsenate (As(V)) to Miscanthus biochar at different pH values and pyrolysis temperatures and the sorption mechanisms were comprehensively investigated. The maximum sorption capacities for both Cd(II) and As(V) were observed under alkaline conditions. Physisorption was identified as a common sorption mechanism for both Cd(II) and As(V) irrespective of pH; however, inner-sphere complexation with acidic functional groups (AFGs) and crystallized precipitation as otavite predominate at higher pH values for Cd(II), while hydrophobic attraction of arsenite and metallic As and electrostatic bridging with multivalent ions at deprotonated AFGs are presumed to be dominant sorption mechanisms for As(V). Inner-sphere complexes of Cd(II) (98.6%) and electrostatic bridging complexes of As(V) (89.5%) were the dominant sorption forms for B400, while inner-sphere complexes (45.9%) and precipitates (50.5%) of Cd(II) and physisorption and hydrophobic interactions of As (63.7%) were abundant. The results challenge the widely held notion that the sorption of anions decreases as pH increases, while that of cations increases with increasing pH. This unexpected phenomenon can be explained by reduction of As(V) and by the difference in the charge densities between As(V) and basic functional groups of the biochar. Such biochar-induced reduction would cause an unexpected risk of exposing human health and ecosystems to reduceable pollutants. These findings contribute to a better explanation for the environmental fate and behavior of inorganic pollutants in biochar applications.

Source apportionment and human health risk assessment of trace metals and metalloids in surface soils of the Mugan Plain, the Republic of Azerbaijan.

The Mugan Plain is the most productive area in the Republic of Azerbaijan, but a previous study confirmed trace metal and metalloid (TM&M) contamination with Cr, Ni and Pb, and the potential ecological risk of As was estimated. However, no industrial activity was previously reported in this area; thus, a source apportionment model using positive matrix factorization (PMF) was employed to identify pollution sources, and a human health risk assessment was conducted to evaluate noncarcinogenic and carcinogenic risks. Surface soil samples were collected from 349 sites, and six major elements (Si, Ca, Cl, P, S and Sr) and 8 TM&Ms (As, Cd, Cr, Co, Cu, Ni, Pb and Zn) were analyzed by X-ray fluorescence and employed for further apportionment and risk assessment. As a result, the PMF model showed 7 factors, assigned to natural activity (12.9%), dry riverbed (13.6%), surface accumulation (3.1%), desalinization activity (3.2%), residential activity (12.3%), fossil fuel combustion (35.5%) and agricultural activity (19.3%). The PMF model characterized certain areas with desalinization activity in the previous Soviet period and with surface accumulation of salt, and these findings were confirmed by additional field surveys and historical Landsat satellite images. The risk assessment results showed that there was no risk for the adults, while for children, there was a noncarcinogenic risk, but no carcinogenic risk. Dermal contact was estimated to be the primary pathway, and Ni and As were identified as the most problematic TM&Ms for noncarcinogenic and carcinogenic risks, respectively. According to the results, fossil fuel combustion associated with heating and vehicle transportation was estimated to be the main source of pollution, contributing 42.6% of the noncarcinogenic and 48.0% of the carcinogenic risks. These results can provide scientific guidance to understand and prevent the risk of TM&Ms on the Mugan Plain.

Spatial distribution of salinity and heavy metals in surface soils on the Mugan Plain, the Republic of Azerbaijan.

The Republic of Azerbaijan suffers from low agricultural productivity caused by soil salinization and erosion, and limited and insufficient soil data are available for economic and political reasons. In this study, soil salinity and heavy metal levels were assessed. Environmental risk assessment was conducted to evaluate the potential risk posed by soils to human health. Soil guideline values were proposed to monitor soil pollution in the Republic of Azerbaijan. Water extraction and spatial variability analysis were conducted to understand soil salinization and heavy metal pollution. Among the 20 studied elements, the elements Ca, Cl, and S and the heavy metals Cr, Ni, and Pb were classified as problematic on the basis of the geoaccumulation index, and As was also identified as posing a possible risk on the basis of the potential ecological risk index. Based on the developed soil guideline values for agricultural soil, the As, Cr, and Ni in the soil samples exceeded their respective guidelines by 31.3, 41.8, and 61.6%, respectively. Water extraction results confirmed that 99% of the leached ions were cationic salts, and the most problematic ion was Na, followed by Ca, Cl, and S. The extractability values of Cr and Ni were significantly lower than those of other heavy metals, which implies that their actual leaching potential may be overestimated. The linear regression and spatial variability analysis confirmed that leachable salts have accumulated in lowland areas due to the capillary rise of water and evaporation, but the distribution of heavy metals confirmed that As, Cr, and Ni were abundant in agricultural soils. Our results clearly showed that heavy metal soil contamination and high salinity levels are major problems that should be considered when assessing food safety and health hazards in the Mugan Plain of Azerbaijan. Therefore, future studies should be performed for additional environmental risk assessment, detailed hazard identification, and health risk assessment.

Characterizing Preferential Adsorption of Phosphate on Binary Sorbents of Goethite and Maghaemite using in situ ATR-FTIR and 2D Correlation Spectroscopy.

Recent developments in analytics using infrared spectroscopy have enabled us to identify the adsorption mechanism at interfaces, but such methods are applicable only for simple systems. In this study, the preferential adsorption of phosphate on binary goethite and maghaemite was investigated. As a result, monodentate and bidentate complexes were the major complexes on goethite and maghaemite, respectively. A shrinking effect in goethite and a swelling effect in maghaemite were identified, and environmental perturbations caused a significant decrease in the integrated absorbance of phosphate complexes on maghaemite, while no effect was observed on goethite, which implies that different adsorption mechanisms were involved. Based on the results, a bridging complex was proposed, and the swelling effect is explained by the negatively charged maghaemite surface resulting from the bidentate complex. The isolation of phosphate by the shrinking effect explains the low phosphate bioavailability in the soil environment, while the colloidal properties of the bidentate complex on maghaemite are the reason for colloidal mobilization. To the best of our knowledge, this study not only addresses the shrinking and swelling properties of iron (hydr)oxide nanoparticles but also demonstrates preferential adsorption on binary sorbents using in situ ATR-FTIR for the first time.

Interpreting competitive adsorption of arsenate and phosphate on nanosized iron (hydr)oxides: effects of pH and surface loading.

Arsenate and phosphate have similar properties due to their electrochemical structures, but their environmental impacts are unique. The abundance and competition of arsenate and phosphate determine their bioavailability and leachability; thus, it is essential to understand their fate in the soil environment. In this study, the effects of pH and surface loading on the competitive adsorption of arsenate and phosphate on four iron (hydr)oxides were evaluated by employing the Langmuir isotherm, competitive sorption ratio (CSR), and competition effect (CE). The stability and transformation of the iron (hydr)oxides were also assessed. Various adsorption patterns were observed in the single and mixed treatments by controlling the addition of oxyanions, pH, surface loading, and type of iron (hydr)oxides. Arsenate was preferentially adsorbed at a low pH, whereas phosphate showed the opposite trend. The CEAs(V),P(V) was close to zero at low surface density (no competition) and sequentially changed to negative or positive values with increasing surface density, indirectly indicating the sequential development of promotive and competitive effects. Transformation in goethite was identified at a high pH with the presence of oxyanions, except that no transformation was observed upon the addition of oxyanions and with pH change. However, the stability of the iron (hydr)oxides decreased at a low pH and with the presence of phosphate, arsenate, or both. The hematite showed a significant promotive effect regardless of the pH. Our study revealed that the pH, surface loading, and type of iron (hydr)oxides are intercorrelated and simultaneously affect the adsorption characteristics of oxyanions and the stability of iron (hydr)oxides.

Identification of Bernalite Transformation and Tridentate Arsenate Complex at Nano-goethite under Effects of Drying, pH and Surface Loading.

The structural configuration of arsenate on iron (hydr)oxide determines its leachability and bioavailability in the soil environment. It is important to understand how the stability of iron hydroxide and the structural configuration of arsenate complexes vary in response to changes in environmental conditions. Therefore, we investigated the effects of drying, pH and surface loadings on the stability of goethite and the structural configuration of arsenate through batch experiments and TEM and XAS measurements with DFT calculation. As a result, we observed no significant transformation of goethite under most conditions, but TEM confirmed the partial formation of bernalite in the presence of arsenate at a pH of 10, and the bernalite showed 2.18 times higher arsenate sorption than the goethite. The linear combination fitting of the EXAFS spectra with DFT calculations revealed that tridentate and bidentate complexes were dominant under low surface loading and pH conditions in the sedimented samples, while monodentate complexes were abundant under high surface loading and pH conditions. Based on our results, we conclude that the formation of arsenic-rich colloids could account for mobilization in the soil environment, and the density of available sorption sites combined with the concentration of solute could cause the change in structural configuration.

Nitrogen removal through N cycling from sediments in a constructed coastal marsh as assessed by 15N-isotope dilution.

Constructed coastal marsh regulates land-born nitrogen (N) loadings through salinity-dependent microbial N transformation processes. A hypothesis that salinity predominantly controls N removal in marsh was tested through incubation in a closed system with added-15NH4+ using sediments collected from five sub-marshes in Shihwa marsh, Korea. Time-course patterns of concentrations and 15N-atom% of soil-N pools were analyzed. Sediments having higher salinity and lower soil organic-C and acid-extractable organic-N exhibited slower rates of N mineralization and immobilization, nitrification, and denitrification. Rates of denitrification were not predicted well by sediment salinity but by its organic-C, indicating heterotrophic denitrification. Denitrification dominated N-loss from this marsh, and nitrogen removal capacity of this marsh was estimated at 337 kg N day-1 (9.9% of the daily N-loadings) considering the current rooting depth of common reeds (1.0 m). We showed that sediment N removal decreases with increasing salinity and can increase with increasing organic-C for heterotrophic denitrification.

Vertical distribution of bacterial community is associated with the degree of soil organic matter decomposition in the active layer of moist acidic tundra.

The increasing temperature in Arctic tundra deepens the active layer, which is the upper layer of permafrost soil that experiences repeated thawing and freezing. The increasing of soil temperature and the deepening of active layer seem to affect soil microbial communities. Therefore, information on soil microbial communities at various soil depths is essential to understand their potential responses to climate change in the active layer soil. We investigated the community structure of soil bacteria in the active layer from moist acidic tundra in Council, Alaska. We also interpreted their relationship with some relevant soil physicochemical characteristics along soil depth with a fine scale (5 cm depth interval). The bacterial community structure was found to change along soil depth. The relative abundances of Acidobacteria, Gammaproteobacteria, Planctomycetes, and candidate phylum WPS-2 rapidly decreased with soil depth, while those of Bacteroidetes, Chloroflexi, Gemmatimonadetes, and candidate AD3 rapidly increased. A structural shift was also found in the soil bacterial communities around 20 cm depth, where two organic (upper Oi and lower Oa) horizons are subdivided. The quality and the decomposition degree of organic matter might have influenced the bacterial community structure. Besides the organic matter quality, the vertical distribution of bacterial communities was also found to be related to soil pH and total phosphorus content. This study showed the vertical change of bacterial community in the active layer with a fine scale resolution and the possible influence of the quality of soil organic matter on shaping bacterial community structure.

Fluxes of nutrients and trace metals across the sediment-water interface controlled by sediment-capping agents: bentonite and sand.

The effect of bentonite and sand, as natural capping agents, on the fluxes of nutrients and trace metals across the sediment-water interface was studied through sediment incubation, and the ecotoxicological impact was assessed by using Daphnia magna. Bentonite and sand were layered on the sediment at 15, 75, and 225 mg cm(-2), and the concentration of cations, nutrients, and trace metals was measured. Sediment incubation showed that bentonite reduced the N flux but increased the P flux as a result of dissolution of non-crystalline P from bentonite, while sand slightly decreased the N fluxes but not the P flux. The concentration of Na increased in the overlying water with increasing application rates of bentonite, while that of Ca decreased. However, regardless of the rate of sand application, concentrations of all cation species remained unchanged. The concentration of As and Cr increased with bentonite application rate but decreased with sand. Both capping materials suppressed fluxes of Cd, Cu, Ni, and Zn compared to control, and the extent of suppression was different depending on the trace metal species and capping agents used. During sediment incubation, the survival rate of D. magna significantly decreased in bentonite suspension but began to decrease at the end in sand suspension. Sediment capping of mildly polluted sediments by using bentonite and sand lowered the level of nutrients and trace metals. However, unexpected or undesirable side effects, such as influxes of P and As from bentonite to the overlying water and a possibility of toxic impacts to aquatic ecosystems, were observed, suggesting that capping agents with an adequate assessment of their side effects and toxicity should be predetermined for site-specific sediment management strategies.

Short-Term Effects of Low-Level Heavy Metal Contamination on Soil Health Analyzed by Nematode Community Structure.

The short-term effects of low-level contamination by heavy metals (As, Cd, Cu, and Pb) on the soil health were examined by analyzing soil nematode community in soils planted with tomatoes. For this, the soils were irrigated with five metal concentrations ([1, 1/4, 1/4(2), 1/4(3), and 0] × maximum concentrations [MC] detected in irrigation waters near abandoned mine sites) for 18 weeks. Heavy metal concentrations were significantly increased in soils irrigated with MC of heavy metals, among which As and Cu exceeded the maximum heavy metal residue contents of soil approved in Korea. In no heavy metal treatment controls, nematode abundances for all trophic groups (except omnivorous-predatory nematodes [OP]) and colonizer-persister (cp) values (except cp-4-5) were significantly increased, and all maturity indices (except maturity index [MI] of plant-parasitic nematodes) and structure index (SI) were significantly decreased, suggesting the soil environments might have been disturbed during 18 weeks of tomato growth. There were no concentration-dependent significant decreases in richness, abundance, or MI for most heavy metals; however, their significant decreases occurred in abundance and richness of OP and cp-4, MI2-5 (excluding cp-1) and SI, indicating disturbed soil ecosystems, at the higher concentrations (MC and MC/4) of Pb that had the most significant negative correlation coefficients for heavy metal concentrations and nematode community among the heavy metals. Therefore, the short-term effects of low-level heavy metal contamination on soil health can be analyzed by nematode community structures before the appearance of plant damages caused by the abiotic agents, heavy metals.

Tracing carbon monoxide uptake by Clostridium ljungdahlii during ethanol fermentation using (13)C-enrichment technique.

Conversion of synthesis gas (CO and H2) to ethanol can be an alternative, promising technology to produce biofuels from renewable biomass. To distinguish microbial utilization of carbon source between fructose and synthesis gas CO and to evaluate biological production of ethanol from CO, we adopted the (13)C-enrichment of the CO substrate and hypothesized that the residual increase in δ(13)C of the cell biomass would reflect the increased contribution of (13)C-enriched CO. Addition of synthesis gas to live culture medium for ethanol fermentation by Clostridum ljungdahlii increased the microbial growth and ethanol production. Despite the high (13)C-enrichment in CO (99 atom % (13)C), however, microbial δ(13)C increased relatively small compared to the microbial growth. The uptake efficiency of CO estimated using the isotope mass balance equation was also very low: 0.0014 % for the low CO and 0.0016 % for the high CO treatment. Furthermore, the fast production of ethanol in the early stage indicated that the presence of sugar in fermentation medium would limit the utilization of CO as a carbon source by C. ljungdahlii.

Analysis of isoflavone, phenolic, soyasapogenol, and tocopherol compounds in soybean [ Glycine max (L.) Merrill] germplasms of different seed weights and origins.

This study investigated the functional compounds, including isoflavones, phenolics, soyasapogenols, and tocopherols, that were detected in 204 soybean [ Glycine max (L.) Merrill] germplasms. The soybean samples were divided into three groups according to origin: America, China, and Korea. The soybean samples were also classified into three groups on the basis of 100-seed weight: small (<13 g), medium (13-24 g), and large (>24 g). Among the soybean germplasms, CSRV121 (Bosukkong) had the highest level of isoflavone content (4778.1 µg g(-1)), whereas CS01316 had the lowest isoflavone content (682.4 µg g(-1)). Of the soybeans from the three different countries of origin, those from Korea showed the highest average concentration of total isoflavones (2252.6 µg g(-1)). The small seeds had the highest average total isoflavone concentration (2520.0 µg g(-1)) of the three different seed sizes. Among the 204 soybean germplasms, CS01405 had the highest content of total phenolics (5219.6 µg g(-1)), and CSRV017 (Hwangkeumkong) had the lowest phenolic content (654.6 µg g(-1)). The mean concentrations of total phenolic compounds were 2729.1 µg g(-1) in American soybean seeds, 1680.4 µg g(-1) in Chinese soybean seeds, and 1977.6 µg g(-1) in Korean soybean seeds. Of the soybean seeds from the three different countries of origin, American soybean seeds had the highest average concentration of total phenolic compounds, and Korean varieties showed the second highest value. Small soybean seeds had the highest average content of total phenolic compounds (2241.7 µg g(-1)), whereas medium-sized (1926.8 µg g(-1)) and large (1949.9 µg g(-1)) soybeans had lower concentrations of phenolic compounds. In whole soybean germplasms, the level of total soyasapogenols was higher in CS01173 (1802.3 µg g(-1)) and CS01346 (1736.8 µg g(-1)) than in the other types of soybeans. The mean concentrations of total soyasapogenol were 1234.0 µg g(-1) in American, 1294.5 µg g(-1) in Chinese, and 1241.5 µg g(-1) in Korean soybean varieties. Chinese soybean varieties showed the highest mean concentration of total soyasapogenol, and Korean soybean seeds showed the second highest level. The medium-seed group had the highest soyasapogenol content (1269.3 µg g(-1)) of the seeds that were grouped by size. A larger amount of soyasapogenol B than soyasapogenol A was detected. In whole soybeans, CS01202 showed the highest level of total tocopherols (330.5 µg g(-1)), whereas CSRV056 (Pungsannamulkong) had the lowest content (153.3 µg g(-1)). Chinese soybeans had the highest average concentration of total tocopherols (255.1 µg g(-1)). By comparison, the medium-sized Chinese soybean group had the highest (256.1 µg g(-1)) average total tocopherol content.

Effects of phosphate addition on biofilm bacterial communities and water quality in annular reactors equipped with stainless steel and ductile cast iron pipes.

The impact of orthophosphate addition on biofilm formation and water quality was studied in corrosion-resistant stainless steel (STS) pipe and corrosion-susceptible ductile cast iron (DCI) pipe using cultivation and culture-independent approaches. Sample coupons of DCI pipe and STS pipe were installed in annular reactors, which were operated for 9 months under hydraulic conditions similar to a domestic plumbing system. Addition of 5 mg/L of phosphate to the plumbing systems, under low residual chlorine conditions, promoted a more significant growth of biofilm and led to a greater rate reduction of disinfection by-products in DCI pipe than in STS pipe. While the level of THMs (trihalomethanes) increased under conditions of low biofilm concentration, the levels of HAAs (halo acetic acids) and CH (chloral hydrate) decreased in all cases in proportion to the amount of biofilm. It was also observed that chloroform, the main species of THM, was not readily decomposed biologically and decomposition was not proportional to the biofilm concentration; however, it was easily biodegraded after the addition of phosphate. Analysis of the 16S rDNA sequences of 102 biofilm isolates revealed that Proteobacteria (50%) was the most frequently detected phylum, followed by Firmicutes (10%) and Actinobacteria (2%), with 37% of the bacteria unclassified. Bradyrhizobium was the dominant genus on corroded DCI pipe, while Sphingomonas was predominant on non-corroded STS pipe. Methylobacterium and Afipia were detected only in the reactor without added phosphate. PCR-DGGE analysis showed that the diversity of species in biofilm tended to increase when phosphate was added regardless of the pipe material, indicating that phosphate addition upset the biological stability in the plumbing systems.

Effects of soil dilution and amendments (mussel shell, cow bone, and biochar) on Pb availability and phytotoxicity in military shooting range soil.

Bioavailability and bioaccessibility determine the level of metal toxicity in the soils. Inorganic soil amendments may decrease metal bioavailability and enhance soil quality. This study used mussel shell, cow bone, and biochar to reduce lead (Pb) toxicity in the highly contaminated military shooting range soil in Korea. Water-soluble and 1-M ammonium nitrate extractions, and a modified physiologically based extraction test (PBET) were performed to determine Pb bioavailability and bioaccessibility in the soil, respectively. Active C in the soil was also measured to evaluate the effects of the amendments on biological soil quality. The Pb contaminated soil was diluted in serial with uncontaminated soil for the bioassays. Seed germination and root elongation tests using lettuce (Lactuca sativa) showed increases in germination percentage and root length in soil treated with the amendments. Biochar was most effective and increased seed germination by 360% and root length by 189% compared to the unamended soil. Up to 20% soil dilution resulted in more than 50% seed germination. Bioavailability and bioaccessibility of Pb in the soils were decreased by 92.5% and 48.5% with mussel shell, by 84.8% and 34.5% with cow bone, and by 75.8% and 12.5% with biochar, respectively, compared to the unamended soil. We found that the Pb availability in the military shooting range soil can be reduced effectively by the tested amendments or soil dilution alternately, thereby decreasing the risk of ecotoxicity. Furthermore, the increasing active C from the amendments revitalized the soil contaminated with Pb.

Major essential oils composition and immunotoxicity activity from leaves of Foeniculum vulgare against Aedes aegypti L.

The leaves of Foeniculum vulgare (Umbelliferae) were extracted and the major essential oil composition and immunotoxicity effects were studied. The analyses conducted by gas chromatography and mass spectroscopy (GC-MS) revealed the essential oils of F. vulgare leaves. The F. vulgare essential oil yield was 0.97%, and GC/MS analysis revealed that its major constituents were methyl clavicol (46.3%), α-phellandrene (18.2%), fenchone (10.6%), (E)-anethole (11.3%), myrcene (3.4%), and α-pinene (2.1%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 41.23 ppm and an LC(90) value of 65.24 ppm. Also, methyl clavicol (≥98.0%), α-phellandrene (≥95.0%), fenchone (≥98.0%), (E)-anethole (≥99.0%), myrcene (≥99.0%), and α-pinene (≥99.0%) were tested against the F(21) laboratory strain of A. aegypti. Fenchone (≥98.0%) and (E)-anethole (≥99.0%) have medium activity with an LC(50) value of 73.11 ppm and 102.41 ppm. The above data indicate that major compounds interaction may play a more important role in the toxicity of essential oil.

Phenolic compound concentration and antioxidant activities of edible and medicinal mushrooms from Korea.

A study was conducted to determine the content of phenolic compounds and the antioxidative activity of five edible and five medicinal mushrooms commonly cultivated in Korea. Phenolic compounds were analyzed using high performance liquid chromatography, and antioxidant activity was evaluated by 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity and superoxide dismutase activity. A total of 28 phenolic compounds were detected in the mushrooms studied. The average total concentration of phenolic compounds was 326 microg/g, the average being of 174 microg/g in edible mushrooms and 477 microg/g in medicinal mushrooms. The average total flavonoids concentration was 49 microg/g, with averages of 22 and 76 microg/g in edible and medicinal mushrooms, respectively. The DPPH radical scavenging activities ranged between 15 (Pleurotus eryngii) and 70% (Ganoderma lucidum) when reaction time was for 1 min. When reaction time was 30 min, the values ranged between 5 (Pleurotus eryngii) and 78% (Agaricus bisporus). The SOD activity averaged 28% among the 10 mushroom species, averages for edible and medicinal mushrooms being comparable. DPPH activities was significantly correlated (p < 0.01) with total content of phenolic compounds in edible mushrooms, while in medicinal mushrooms there was a significant correlation (p < 0.01) between SOD activity and total concentration of phenolic compounds. Numerous significant positive correlations were observed between phenolic compounds detected and antioxidative potential.

Changes in nitrogen isotopic compositions during composting of cattle feedlot manure: effects of bedding material type.

Temporal changes in delta(15)N of cattle feedlot manure during its composting with either rice hull (RHM) or sawdust (SDM) as bedding materials were investigated. Regardless of the bedding material used, the delta(15)N of total N in the manure increased sharply from +7.6 per thousand to +9.9 per thousand and from +11.4 per thousand to +14.3 per thousand, respectively, in RHM or SDM, within 10 days from the commencement of composting. Such increases could be attributed primarily to N loss via NH(3) volatilization and denitrification based on the very high delta(15)N values (greater than +20 per thousand) of NH(4)(+) and NO(3)(-) in the co-composted manure. The delta(15)N of total N in RHM was substantially lower (by more than 3 per thousand) than that in SDM, suggesting that the delta(15)N of the composted manure was affected not only by N loss but also by the type of bedding material used. Specifically, the higher N concentration in the rice hull than in the saw dust could lead to a greater (15)N isotope dilution.

Comparison of isoflavone concentrations in soybean (Glycine max (L.) Merrill) sprouts grown under two different light conditions.

We determined and compared the composition and content of isoflavones in the cotyledon, hypocotyl, and root of 17 soybean sprout varieties grown under dark and light conditions. The total average isoflavone concentrations in 17 soybean sprout varieties were 2167 microg g(-1) (green sprout) and 2538 microg g(-1) (yellow sprout) in cotyledons, 1169 microg g(-1) (green sprout) and 1132 microg g(-1) (yellow sprout) in hypocotyls, and 2399 microg g(-1) (green sprout) and 2852 microg g(-1) (yellow sprout) in roots. There were no significant differences in total isoflavone concentrations between the green and yellow sprouts. However, significant differences in total isoflavone amounts were observed among the three organs, with roots exhibiting the highest total isoflavone concentrations followed by cotyledons and hypocotyls. Total daidzin concentrations of green (775 microg g(-1)) and yellow (897 microg g(-1)) sprouts increased to more than 4 times that in seeds (187 microg g(-1)). Yellow sprouts contained the highest (1122 microg g(-1)) total genistin concentrations, and green (155 microg g(-1)) and yellow (155 microg g(-1)) sprouts had more total glycitin concentrations than seeds. In cotyledons of green and yellow sprouts, genistin, daidzen, and glycitin constituted more than 67%, more than 28%, and less than 4% of the total isoflavone contents, respectively. In hypocotyls, total daidzin represented more than 45% of the total isoflavones, and total glycitin was higher than in cotyledons and roots. Malonylglycoside concentrations were highest in cotyledons, whereas glycoside concentrations were highest in hypocotyls and roots. The high accumulation of isoflavones in roots is consistent with isoflavones serving as signal molecules in the induction of microbial genes involved in soybean (Glycine max) nodulation.

Soil metabolism of a new herbicide, [14C]Pyribenzoxim, under flooded conditions.

To elucidate the fate of a new pyrimidinyloxybenzoic herbicide, pyribenzoxim, a soil metabolism study was carried out with [14C]pyribenzoxim applied to a sandy loam soil under flooded conditions. The material balance of applied radioactivity ranged from 96.4 to 104.4% and from 96.1 to 101.9% for nonsterile and sterile soils, respectively. The half-life of [14C]pyribenzoxim was calculated to be approximately 1.3 and 9.4 days for nonsterile and sterile soils, respectively. The metabolites identified during the study were 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid (M1) and 2-hydroxy-6-(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid (M2), resulting from the cleavage of the ester bond and subsequent hydrolysis. The nonextractable radioactivity levels increased to 37.8% for nonsterile conditions at 50 days after treatment and to 38.2% for sterile conditions at 60 days after treatment. Fractionation of the nonextractable soil residues indicated that bound radioactivity was associated mainly with humin fraction. No significant volatile products or [14C]carbon dioxide was observed during the study. On the basis of these results, pyribenzoxim is considered to undergo rapid degradation in soil by microbial and chemical reactions, mainly hydrolysis, which limits its transfer to and accumulation in lower soil layers and groundwater. Therefore, the possibility of environmental contamination from the use of pyribenzoxim is expected to be very low.