Dynamics of Atmospheric Aerosol Number Size Distributions in the Eastern Mediterranean During the ��SUB-AERO�� Project

Measurements of number size distributions of submicron aerosols have been performed at the Eastern part of Mediterranean as part of an extensive measurement campaign to study photo-oxidants and aerosols (SUB-AERO Project). The measurements were made at the Finokalia station on the island of Crete (Greece) and onboard the research vessel ??Aegaeon??. Two campaigns were performed during July 2000 and January 2001 using two scanning mobility particle sizers. The particle distributions measured in the range between 7.8 < d _p < 327 nm during the summer measurements and between 7.5 < d _p < 316 nm during the winter measurements, where d _p is the mobility particle diameter. The concentration of ultrafine particles (7.5 < d _p < 30 nm) was higher during the winter period and varied mainly between 5 × 10¹ and 2 × 10³?cm^?3 with concentration peak values for this mode exceeding 1 × 10⁴?cm^?3. During the summer campaign, an average number concentration of 1 × 10²?cm^?3 at Finokalia and about 5 × 10¹?cm^?3 aboard the ??Aegaeon?? vessel was measured. An average concentration of 1 × 10³?cm^?3 was measured for the particles in the size range between 30 and 100 nm, whereas in the size range 100?C300 nm, the measured concentration ranged between 1 × 10² and 5 × 10³?cm^?3. Diurnal patterns in number concentrations were observed in connection with the transport of air masses and local sources. During the winter period, three nucleation events were observed in connection with the appearance of a particle mode at 20 nm.     

Rhizosphere effects of maize hybrids and N forms on Cd bioavailability in a limed soil

Replacing new corn genotypes in agricultural practices requires adequate information on the reaction of the selected hybrids to Cd uptake in Cd-polluted soil and an understanding of interactions with N fertilizers. A 2 × 2 × 3 factorial pot experiment with limed soil (pH 8), two maize (Zea mays) hybrids (Pioneer cultivar yellow and Pioneer cultivar white), two N fertilization forms (NH₄ ⁺ and NO₃ ^?) and three Cd exposures (0, 2 and 5 mg kg^?1 soil) was conducted under greenhouse conditions. Shoot dry mass increased significantly with NH₄ ⁺ nutrition compared with NO₃ ^? nutrition in both maize hybrids, with greater negative influence of Cd application combined with NH₄ ⁺ nutrition. The yellow cultivar had significantly greater shoot dry mass and lower Cd uptake than the white cultivar. Both hybrids exhibited similar N uptake in shoots and roots, with the exception of yellow cultivar with NH₄ ⁺ nutrition without Cd application. NO₃ ^? nutrition always decreased Cd uptake in both cultivars compared with NH₄ ⁺ nutrition. The N balance (mean across cultivars and Cd supply) after harvest showed most N uptake with NH₄ ⁺ nutrition (63.4%) and N_min remains in the soil with NO₃ ^? nutrition (48.7%). Soil pH decreased more with NH₄ ⁺ (?0.95 pH units) than NO₃ ^? nutrition (?0.21).     

Soil Ammonium Diffusion Constraints Contribute to Large Differences in Nitrogen Supply to Rice in the Southern United States

This study was to determine if diffusion of soil ammonium may explain why many sandy soils have greater nitrogen (N)–supplying capacity to rice than clay soils. A laboratory procedure using transient-state methods measured the linear movement of soil ammonium (NH₄) in tubes packed with five field soils under aerobic conditions. Ammonium diffusion was measured by sectioning tubes after 48 h of equilibration and then measuring NH₄ by steam distillation. Effective diffusion coefficients, D_e, and NH₄ diffusion distance, d, per day ranged from D_e = 4.6 × 10^?5 cm² d^?1 and 1.5 cm d^?1 for Katy sandy loam to D_e = 2.9 × 10^?7 cm² d^?1 and 0.11 cm d^?1 for League clay. Ammonium diffusion distance d was strongly related to soil clay content and hence was predicted by d = Y × {[100/(% clay)] ? 1}, where Y is set to 0.1. Predicted d and measured d were highly related (R² = 0.99).     

Effects of Soil Amendments on Growth and Metal Uptake by Ocimum gratissimum Grown in Cd/Zn-Contaminated Soil

Hydroponic and pot experiments were conducted to assess the uptake of heavy metals (Cd and Zn) by a common crop plant, African basil, Ocimum gratissimum. In addition, the effects of soil amendments, hydroxyapatite (HA) and cow manure on plant growth and metal accumulations were compared. In the hydroponic study, plants were exposed to various concentrations of Cd (2.5 and 5 mg L^?1) and Zn (10 and 20 mg L^?1) for 15 days. O. gratissimum was shown to be a Cd accumulator more than a Zn accumulator. Cadmium concentration in its shoots exceeded 100 mg kg^?1. In the pot experiments, soils from a heavily Cd-contaminated site (Cd 67.9 mg kg^?1 and Zn 2,886.8 mg kg^?1) were treated with cow manure and HA at the rates of 10% and 20% (w/w), and 0.75 and 1.5% (w/w), respectively. Plants were grown in the greenhouse for 3 months. The addition of cow manure resulted in the highest biomass production and the lowest accumulations of Cd in plant parts, while HA was more efficient than cow manure in reducing Zn uptake. Leaves of African basil showed a decreased Cd concentration from 1.5 to 0.3 mg kg^?1 (cow manure) and decreased Zn concentration from 69.3 to 34 mg kg^?1 (HA). This clearly demonstrates the efficiency of HA and cow manure in reducing metal content in leaves of plants grown on high metal-contaminated soil to acceptable or close to acceptable values (0.2 mg kg^?1 for Cd, 99.4 mg kg^?1 for Zn).     

Cadmium soil sorption at low concentrations: VIII. correlation with soil parameters

Cadmium distribution coefficients, K _d were determined at low Cd concentrations (solute: 0.2 to 3.0 μg Cd dm^?3, soil: 0.044 to 1.1 mg Cd kg^?1) for 63 Danish agricultural soils. The K _d values ranged from 15 to 2450 L kg^?1. About 40% of the soils had K _d values below 200 L kg^?1. The observed K _d values correlated very well with soil pH (r ² = 0.72). Introducing soil organic matter content as a second parameter improved the correlation some (r ² = 0.79). No further improvements were obtained by introducing traditional soil parameters as clay, silt, fine sand, coarse sand and CEC or ‘reactive’ parameters as oxyhydroxides of Mn, Fe and Al. The identified regression equation for predicting K _d values indicates that K _d approximately doubles for each 0.5 unit increase in pH or 2% increase (weight basis) in organic matter content.     

Effects of aluminium ions on uptake of calcium,magnesium and nitrogen in Betula pendula seedlings growing at high and low nutrient supply rates

The effects of aluminium on plant nutrition in small birch plants (Betula pendula Roth) were investigated. By using relative addition rate (r _A, g g^?1 d^?1) of nutrients as the growth-controlling variable, it was possible to grow the plants at very low external nutrient concentrations and to simulate plant requirements at two different fertility levels. Before aluminium addition the plants were at steady-state relative growth rate, (R _G, g g^?1 d^?1). The two addition rates were free access of nutrients with R _G ≈ 0.215 d^?1, or nutrient-limited, R _Aand R _G=0.10 d^?1. Internal concentrations of calcium and magnesium decreased with increasing Al³⁺ conncentration in the nutrient solution while nitrogen concentrations in the plants remained unchanged or increased. It was demonstrated in both nutrition treatments that calcium and magnesium decrease per se does not reduce plant growth and that uptake has to be considered in relation to plant requirement at different growth rates. The interpretation of the effects of aluminium on Ca and Mg uptake and plant biomass development suggested that processes other than disturbances in Ca and Mg uptake are the cause of the decrease in growth.     

Kinetics of cadmium uptake by green algae

The kinetics of cadmium uptake by Selenastrum capricornutum Printz was studied at 21 °C and 0 °C and at four different concentrations of free cadmium (10^?9, 10^?8, 10^?7 and 10^?3 M). The free cadmium concentrations in the medium were kept constant through buffering by a chelating agent (NTA). Initial uptake occurred within 10 min at both temperatures, indicating a fast process. At 21 °C, the cadmium uptake increased during the experimental sampling times from 0.12 to 50 h, whereas at 0 °C, the cadmium uptake remained constant after the first sampling time. Apparently, two different processes were involved in cadmium uptake, a first fast, probably passive process and a second slower, possibly physiological process. The cadmium uptake processes are described with a generalized metalligand complex formation model. The experimental dissociation constants for the fast (K _R,F ) and the slow process (K _R,S ) were reproducible for different experiments and they were both in the order of 5 10^?6 mol L^?1. For the slow process, the uptake- and release rate constants (k₁ and k₂) were quantified; for two experiments, the mean value for k_i was 111±28 L mol^?1 h^?1 and the mean value for k ₂ was (5.1±1.8) 10^?4 h^?1. These values were calculated using the fitted value of the cadmium uptake in the fast process.     

Single and Combined Effects of Cadmium and Zinc on Carrots: Uptake and Bioaccumulation

ABSTRACT

The present study was conducted to evaluate the effects of different concentrations of cadmium (Cd) and zinc (Zn), singly and in combination, on uptake and bioaccumulation of Cd and Zn in Daucus carota L. (carrot) grown under natural field conditions. Carrot plants were treated with two Cd concentrations (10 and 100 μg mL^?1), two Zn concentrations (100 and 300 μg mL^?1), and two combined concentrations of Cd and Zn (10 + 100 and 100 + 300 μg mL^?1) 15 d after seed germination. Treatments were repeated at 10 d intervals up to 90 d of plant age. A control was also kept without a Cd or Zn treatment. Uptake, total accumulation rate (TAR), bioconcentration factor (BCF), primary transport index (PTI), secondary transport index (STI), and accumulation of Cd and Zn in root, stem, and leaf were quantified. The results show that uptake, TAR, and accumulation of Cd and Zn are concentration-dependent phenomena. Highest accumulation of Cd and Zn was found in the root, followed by the stem and then leaves. The results also showed that bioaccumulation of Cd in root, stem, and leaf was greater at the low metal-application rates of Cd and Zn in combination than at the higher rate. This study further showed that interactions of Zn and Cd are dependent on the concentrations of those metals in the soil.     

硫杆菌以及好养异养型硫氧化菌对元素硫的氧化

The prediction of the oxidation rate of elemental sulfur (S⁰) is a critical step in sulfur (S) fertilizer strategy to supply plant-available sulfur. An incubation experiment was conducted to determine the rate and amount of S⁰ oxidation in relation to the contribution of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria. After 84 days, 16.3% and 22.4% of the total S⁰ applied to the soil were oxidized at 20 and 30 ℃, respectively. The oxidation of S⁰ proved to be a two-step process with a rapid oxidation during the first 28 days and a slow oxidation from then on. The highest oxidation rate of 12.8 μg S cm^-2 d^-1 was measured during the first two weeks at 30 ℃. At 20 ℃ the highest oxidation rate of 10.2 μg S cm^-2 d^-1 was obtained from two to four weeks after start of the experiment. On an average the soil pH declined by 3.6 and 4.0 units after two weeks of experiment. At the same time the electric conductivity increased nine times. With the oxidation of S⁰ the population of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased. The corresponding values for Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased from 2.9 × 10⁵ and 1.4 × 10⁵ g^-1 soil at the start of the experiment to 4 × 10⁸ and 5.6 × 10⁸ g^-1 soil 14 days after S⁰ application, respectively. No Thiobacillus spp. was present eight weeks after S⁰ application. The results suggested that oxidation of residual S⁰ completely relied on aerobic heterotrophic S-oxidizing bacteria.     

Bioremediation of Lindane Contaminated Soil by Pleurotus ostreatus in Non Sterile Conditions Using Multilevel Factorial Design

A commercial strain of the fungus Pleurotus ostreatus was used to mediate the degradation of lindane, by landfarming technology during a 4 weeks statistical experiment. The Multilevel Factorial Design was used with two design factors, namely, straw content X ₁ (%) and lindane content X ₂ (ppm). The optimization parameters (responses) investigated were: biodegradation rate Y ₁ (μg d^?1), biomass growth rate Y ₂ (mg d^?1), biodegradation/biomass Y ₃ (μg mg^?1), total organic carbon Y ₄ (%), total organic nitrogen Y ₅ (%) and total organic carbon/total organic nitrogen Y ₆. The optima of the adequate models obtained for the period of 2 and 4-weeks were found. An overall kinetic study, conducted in this work with the aid of experimental design, determined the optimum (maximum) specific lindane degradation rate to be 0.16 g kg^?1 month^?1.     

Effects of a chromated-copper-arsenate wood preservative on the growth of a pentachlorophenol degrading bacterium

A chromated-copper-arsenate (CCA) wood preservative was tested for toxic effects on the growth of a bacterial culture (Flavobactenum sp. ATCC 53874) capable of biodegrading pentachlorophenol, another wood preservation chemical. Both a commercially available CCA preparation and a laboratory-prepared CCA solution were tested. Each had an inhibitory effect on the growth of Flavobacterium at diluted CCA levels as low as 1.0×10^?4 to 1.0×10^?5% wt vol^?1. The commercial formulation was generally more toxic. EC₅₀ values calculated after 96 hr of incubation were 1.2 ×10^?4% wt vol^?1 for the commercial material (containing 0.15/0.097/0.14 μg mL^?1 of Cr/Cu/As, respectively) and 3.8×10^?4% for the laboratory solution (containing 0.51/0.31/0.49 μg mL^?1 of Cr/Cu/As, respectively). CCA toxicity increased during the first 7 to 8 days and then slowly decreased for the balance of the 21 day incubation period. Biodegradation of pentachlorophenol residues in contaminated soil will be negatively affected by the presence of CCA as a co-contaminant.     

Sorption of antimony species by humic acid

The retention of antimony (a potential toxin) in polluted soils or waterway sediments can involve interaction with several component phases. One of these, humic acid, has been found to adsorb antimony (III) from solutions of Sb(OH)₃ or potassium antimonyl tartrate (C₈H₄K₂Sb₂O₁₂) in accordance with Langmuir type isotherms. Using Sb(OH)₃ solutions (initial Sb levels < 10 μM) the bonding constant value (at pH 4) was 6 × 10⁵, with a calculated saturation capacity of 23 μmol g^?1. In the antimonyl tartrate systems (initial Sb levels 0.5 to 75 μM) the bonding constant value for the sorbed species was 1.6 × 10⁵ and the saturation capacity 53 μmol g^?1. Addition of small amounts of HCl or NaOH (to vary the pH between 3.1 and 5.4) had little effect on the amount sorbed from KSbT solutions but with Sb(OH)₃ solutions uptake was reduced (by about 15%). In the presence of NaCl (0.5 or 0.05M) Sb uptake increased (by about 15%). Antimony (V) (introduced as KSb (OH)₆) was not sorbed from solutions < 10 μM in this salt. Using more concentrated solutions, uptake gradually increased, reaching a plateau value of around 8 μmol g^?1 with solutions initially 50 or 75 μM.     

Influences of Cadmium and Zinc Interaction and Humic Acid on Metal Accumulation in Ceratophyllum Demersum

Interactions between Zn and Cd on the accumulation of these metals in coontail, Ceratophyllum demersum were studied at different metal concentrations. Plants were grown in nutrient solution containing Cd (0.05–0.25 mg l^?1) and Zn (0.5–5 mgl^?1). High concentrations of Zn caused a significant decrease in Cd accumulation. In general, adding Cd solution decreased Zn accumulation in C. demersum except at the lowest concentration of Zn in which the Zn accumulation was similar to that without Cd. C. demersum could accumulate high concentrations of both Cd and Zn. The influence of humic acid (HA) on Cd and Zn accumulation was also studied. HA had a significant effect on Zn accumulation in plants. 2 mg l^?1 of HA reduced Zn accumulation at 1 mg l^?1 level (from 2,167 to 803 mg kg^?1). Cd uptake by plant tissue, toxicity symptoms and accumulation at 0.25 and 0.5 mg l^?1, were reduced (from 515 to 154 mg kg^?1 and from 816 to 305 mg kg^?1, respectively) by addition of 2 mg l^?1 of HA. Cd uptake reached a maximum on day 9 of treatment, while that of Zn was observed on day 15. Long-term accumulation study revealed that HA reduced toxicity and accumulation of heavy metals.     

Cadmium Accumulation and Translocation in Four Emergent Wetland Species

Emergent wetland plant species may exhibit different capacity for phytoremediation when used in constructed wetlands. To evaluate cadmium (Cd) remediation capacity of four emergent wetland species [Baumea juncea (R.Br.) Palla, Baumea articulata (R.Br.) S.T. Blake, Schoenoplectus validus (M.Vahl) A. & D.Löve, and Juncus subsecundus N.A. Wakef.], a glasshouse experiment was conducted in hydroponics to investigate the effects of Cd (0, 5, 10, and 20 mg L^?1) on plant growth and Cd uptake and translocation as well as uptake of other nutrients after 14 days. The relative growth rates of the three species changed little in various Cd treatments, but was severely inhibited for B. juncea at 20 mg Cd per liter treatment. Hence, the Cd tolerance index (root length in Cd treatment vs. control) was significantly lower in B. juncea compared to other species. Among the species, the highest concentration of Cd was in the roots of J. subsecundus, followed by S. validus, B. articulata, and B. juncea, while the lowest concentration of Cd was in the S. validus shoots. Of all the species, J. subsecundus had the highest bioconcentration factor (BCF) in shoots, whereas S. validus and B. juncea had the lowest BCF in rhizomes and roots, respectively. The translocation factor was significantly lower in S. validus compared to the other species. J. subsecundus had a higher Cd accumulation rate than the other species regardless of the Cd supply. The lowest allocation of Cd in shoots was recorded for S. validus and in roots for B. juncea. The concentrations of other elements (P, S, Ca, Fe, Cu, and Zn) in shoots decreased with Cd additions, but the interactions between Cd and other elements in roots varied with the different species. These results indicate that the four wetland species have good tolerance to Cd stress (except B. juncea at high Cd exposure), varying in Cd accumulation and translocation in tissues. These properties need to be taken into account when selecting species for wetlands constructed for phytoremediation.     

Heavy‐Metal Inhibition of Nitrification in Selected Iowa Soils Treated with Stay‐N 2000

Abstract

Heavy‐metal inhibition of nitrification in soils treated with reformulated nitrapyrin was investigated. Clarion and Okoboji soils were treated with ammonium sulfate [(NH₄)₂SO₄] and a nitrification inhibitor. Copper(II) (Cu), Zinc(II) (Zn), Cadmium(II) (Cd), or Lead(II) (Pb) were added to each soil. A first‐order equation was used to calculate the maximum nitrification rate (K _max), duration of lag period (t′), period of maximum nitrification (Δt), and the termination period of nitrification (t _s). In the Clarion soil, the K _max decreased from 12 mg kg^?1 d^?1 without the nitrification inhibitor to 4, 0.25, 0.86, and 0.27 mg kg^?1 d^?1, respectively, when the inhibitor and Cu, Zn, Pb, or Cd were applied. In the Okoboji soil, K _max decreased from 22 mg kg^?1 d^?1 with no inhibitor to 6, 3, 4, and 2 mg kg^?1 d^?1, respectively, when an inhibitor and Cu, Zn, Pb, or Cd were added. The t′ varied from 8 to 25 d in the Clarion soil and from 5 to 25 d in the Okoboji soil, due to addition of Cu, Zn, Pb, or Cd and the inhibitor.     

Lantana camara——an Ecological Bioindicator Plant for Decontamination of Pb-Impaired Soil Under Organic Waste-Supplemented Scenarios

Heavy metal extraction and processing from ores releases elements into the environment. Soil, being an "unfortunate" sink, has its bionomics impaired and affected by metal pollution. Metals sneak into the food chain and pose risk to humans and other edaphicdependent organisms. For decontamination, the use of an ecosystem-friendly approach involving plants is known as phytoremediation.In this study, different lead(Pb) concentrations(80, 40, 20, and 10 mg kg~(-1)) were used to contaminate a well-characterized soil,(un)supplemented with organic waste empty fruit bunch(EFB) or spent mushroom compost(SMC), with non-edible plant—Lantana camara. Lead removal by L. camara ranged from 45.51% to 88.03% for supplemented soil, and from 23.7% to 57.8% for unsupplemented soil(P 0.05). The EFB-supplemented and L. camara-remediated soil showed the highest counts of heavy metal-resistant bacteria(HMRB)(79.67 × 10~6–56.0 × 10~6 colony forming units(CFU) g~(-1) soil), followed by SMC-supplemented and L. camara-remediated soil(63.33 × 10~6–39.0 × 10~6 CFU g~(-1) soil). Aerial metal uptake ranged from 32.08 ± 0.8 to 5.03 ± 0.08 mg kg~(-1) dry weight, and the bioaccumulation factor ranged from 0.401 to 0.643(P 0.05). Half-lives(t_(1/2)) of Pb were 7.24–2.26 d in supplemented soil,18.39–11.83 d in unsupplemented soil, and 123.75–38.72 d in the soil without plants and organic waste. Freundlich isotherms showed that the intensity of metal absorption(n) ranged from 2.44 to 2.51 for supplemented soil, with regression coefficients of determination(R~2) between 0.901 2 and 0.984 0. The computed free-energy change(?G) for Pb absorption ranged from -5.01 to 0.49 kJ mol~(-1) K~(-1) for EFB-supplemented soil and -3.93 to 0.49 k J mol~(-1) K~(-1) for SMC-supplemented soil.     

ADSORPTION OF CADMIUM AND ITS EXCHANGE CHARACTERISTICS IN SOME ISRAELI SOILS

Cd adsorption isotherms were measured on five Israeli soils ranging in specific surface area from 65 to 315m²/g. Retention capacity of Cd ranged from 4.7 × 10³ to 10 × 10³μg/g soil (8.4 to 17.9 mequiv/100 g soil) and was correlated with the specific surface area. Almost all the adsorbed Cd was exchangeable with 0.5 M CaCl₂ and the remaining fraction was extractable in 0.5 M HCl. Plots of K_d, the distribution coefficient of Cd between the solid and solution phases, vs. Γ, the surface density of adsorbed Cd, showed that all soils behave similarly, K_d sharply diminishing with Γ. It was suggested, based on comparison with literature data on Cd adsorption on montmorillonite, that below γ s 0. 5 × 10¹⁷ ions/m², specific adsorption mechanisms prevail whereas above it the adsorption is mainly due to electrostatic interactions and ion exchange.     

Phytoextraction of Cadmium and Phytostabilisation with Mugwort (Artemisia vulgaris)

Artemisia vulgaris (mugwort) is a tall (1.0?C2.0 m) high biomass perennial herb which accumulates considerable amounts of metals on contaminated sites. An outdoor pot experiment was conducted on a sandy, slightly alkaline soil of moderate fertility to study the uptake of cadmium and the distribution of Cd in plant tissues of A. vulgaris. Cadmium was applied as CdCl₂ (a total of 1 l solution of 0, 10, 50 and 100 mg Cd l^?1) to 12-l pots with a height of 25 cm. HNO₃- and water-extractable concentrations of Cd were correlated with the applied Cd at 2-cm soil depth, but were not correlated at 20-cm soil depth, suggesting that Cd was either not mobile in the soil or completely taken up by mugwort roots. The Cd concentrations in different organs of A. vulgaris and litter increased with increasing soil contamination. Leaf/soil concentration ratios (BCFs) up to 65.93?±?32.26 were observed. Translocation of Cd to the aboveground organs was very high. The leaf/root Cd concentration ratio (translocation factor) ranged from 2.07?±?0.56 to 2.37 ± 1.31; however, there was no correlation of translocation factors to Cd enrichment, indicating similar translocation upon different soil contamination levels. In summary, A. vulgaris is tolerant to the metal concentrations accumulated, has a high metal accumulating biomass and accumulates Cd up to about 70% in the aboveground parts. Both a high phytoextraction potential and a high value for phytostabilisation would recommend mugwort for phytoremediation.     

Distribution of Zinc Fractions in Some Major Soils of India and the Impact on Nutrition of Rice

Abstract

Speciation study of microelements in soils is useful to assess their retention and release by the soil to the plant. Laboratory and greenhouse investigations were conducted for five soils of different agro‐ecological zones (viz., Bhuna, Delhi, Cooch‐Behar, Gurgaon, and Pabra) with diverse physicochemical properties to study the distribution of zinc (Zn) among the soil fractions with respect to the availability of Zn species for uptake by rice plant. A sequential extraction procedure was used that fractionated total soil Zn into water‐soluble (WS), exchangeable (EX), specifically adsorbed (SA), acid‐soluble (AS), manganese (Mn)‐oxide‐occluded (Mn‐OX), organic‐matter‐occluded (OM), amorphous iron (Fe)‐oxide‐bound (AFe‐OX), crystalline Fe‐oxide‐bound (CFe‐OX), and residual (RES) forms. There was a wide variation in the magnitude of these fractions among the soils. The studies revealed that more than 90% of the total Zn content occurred in the relatively inactive clay lattice and other mineral‐bound form (RES) and that only a small fraction occurred in the forms of WS, EX, OM, AFe‐OX, and CFe‐OX. Rice (Oryza sativa L.) cultivars differ widely in their sensitivity to Zn deficiency. Results suggested that Zn in water‐soluble, organic complexes, exchange positions, and amorphous sesquioxides were the fractions (pools) that played a key role in the uptake of Zn by the rice varieties (viz., Pusa‐933‐87‐1‐11‐88‐1‐2‐1, Pusa‐44, Pusa‐834, Jaya, and Pusa‐677). Isotopic ally exchangeable Zn (labile Zn) was recorded higher in Typic Ustrochrept of Pabra soil, and uptake of Zn by rice cultivars was also higher in this soil. The kinetic parameters such as maximum influx at high concentrations (I_max) and nutrient concentration in solution where influx is one half of I_max (K_m) behaved differentially with respect to varieties. The highest I_max value recorded was 9.2×10^?7 µmol cm^?2 s^?1 at the 5 mg kg^?1 Zn rate for Pusa‐933‐87‐1‐11‐88‐1‐2‐1, and the same was lowest for Pusa‐44, being 4.6×10^?7 µmol cm^?2 s^?1 at the 5 mg kg^?1 Zn rate. The K_m value was highest for Pusa‐44 (2.1×10^?4µmol cm^?2 s^?1) and lowest for Pusa‐933‐87‐1‐11‐88‐1‐2‐1 (1.20×10^?4µmol cm^?2 s^?1). The availability of Zn to rice cultivars in Typic Ustrochrepts of Bhuna and Delhi soils, which are characterized by higher activation energy and entropy factor, was accompanied by breakage of bonds or by significant structural changes.     

Estimation and Mapping of Nitrogen Uptake by Forest in South Korea

Regional air pollution in northeast Asia is an emerging environmental problem requiring long-term impact assessment of acidic deposition. In this study, the gridded distribution of nitrogen uptake led by both growing forests and harvested biomass for eight tree species: Japanese Larch, Red pine, Korean pine, Oak tree, Chestnut, Other Conifers, Other broad leaved trees, and Mixed forest was identified to estimate critical loads for nitrogen over South Korea. The gridded spatial distribution of averaged nitrogen uptake was mapped by 0.125° Latitude × 0.125° Longitude resolution. The results showed that net uptake of nitrogen led by both growth and harvested biomass was totaled at 438 mol_c ha^?1 year^?1 among which harvested biomass contribution was estimated to be 25 mol_c ha^?1 year^?1, yielding a very small fraction of total nitrogen uptake presumably due to the younger stages of forest in South Korea.