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The effect of calcium and pH on nickel accumulation in and rhizotoxicity to pea (Pisum sativum L.) root-empirical relationships and modeling
2010
Wu, Yonghong | Hendershot, William H.
The accumulation and rhizotoxicity of Ni to pea were investigated. Calcium, H, and Ni competed for root-binding sites with high pH and low Ca favoring more Ni accumulation. At low pH, Ca accumulation is the key factor determining root growth, while at medium to high pH, root elongation is more sensitive to Ni concentration. The tissue concentration of Ni and Ca ([Ni]t or [Ca]t, μmol g-1 dry root) can be predicted from total dissolved Ni ([Ni]T, μM), pH, and total dissolved Ca ([Ca]T, mM) by two approaches. Approach 1 is the empirical equations [Ni]t = (0.361 pH-0.695[Ca]T)*[Ni]T and [Ca]t = 8.29 pH + 10.8 [Ca]T. The second approach involves a two-step model. The surface-bound Ni and Ca are estimated from a surface adsorption model with binding constants derived from independent ion adsorption experiments. Then transfer functions are used to predict internal root Ni and Ca accumulation.
Show more [+] Less [-]Factors influencing concentrations of dissolved gaseous mercury (DGM) and total mercury (TM) in an artificial reservoir
2010
Ahn, Myung-Chan | Kim, Bomchul | Holsen, Thomas M. | Yi, Seung-Muk | Han, Young-Ji
The effects of various factors including turbidity, pH, DOC, temperature, and solar radiation on the concentrations of total mercury (TM) and dissolved gaseous mercury (DGM) were investigated in an artificial reservoir in Korea. Episodic total mercury accumulation events occurred during the rainy season as turbidity increased, indicating that the TM concentration was not controlled by direct atmospheric deposition. The DGM concentration in surface water ranged from 3.6 to 160 pg/L, having a maximum in summer and minimum in winter. While in most previous studies DGM was controlled primarily by a photo-reduction process, DGM concentrations tracked the amount of solar radiation only in winter when the water temperature was fairly low in this study. During the other seasons microbial transformation seemed to play an important role in reducing Hg(II) to Hg(0). DGM increased as dissolved organic carbon (DOC) concentration increased (p-value < 0.01) while it increased with a decrease of pH (p-value < 0.01). Long-term in-situ monitoring of TM and DGM concentrations with various factors was executed in a large artificial reservoir in this study.
Show more [+] Less [-]Chemical fluxes in time through forest ecosystems in the UK - Soil response to pollution recovery
2010
Vanguelova, E.I. | Benham, S. | Pitman, R. | Moffat, A.J. | Broadmeadow, M. | Nisbet, T. | Durrant, D. | Barsoum, N. | Wilkinson, M. | Bochereau, F. | Hutchings, T. | Broadmeadow, S. | Crow, P. | Taylor, P. | Houston, T Durrant
Long term trend analysis of bulk precipitation, throughfall and soil solution elemental fluxes from 12 years monitoring at 10 ICP Level II forest sites in the UK reveal coherent national chemical trends indicating recovery from sulphur deposition and acidification. Soil solution pH increased and sulphate and aluminium decreased at most sites. Trends in nitrogen were variable and dependant on its form. Dissolved organic nitrogen increased in bulk precipitation, throughfall and soil solution at most sites. Nitrate in soil solution declined at sites receiving high nitrogen deposition. Increase in soil dissolved organic carbon was detected - a response to pollution recovery, changes in soil temperature and/or increased microbial activity. An increase of sodium and chloride was evident - a possible result of more frequent storm events at exposed sites. The intensive and integrated nature of monitoring enables the relationships between climate/pollutant exposure and chemical/biological response in forestry to be explored.
Show more [+] Less [-]Effects of biochar and greenwaste compost amendments on mobility, bioavailability and toxicity of inorganic and organic contaminants in a multi-element polluted soil
2010
Applying amendments to multi-element contaminated soils can have contradictory effects on the mobility, bioavailability and toxicity of specific elements, depending on the amendment. Trace elements and PAHs were monitored in a contaminated soil amended with biochar and greenwaste compost over 60 days field exposure, after which phytotoxicity was assessed by a simple bio-indicator test. Copper and As concentrations in soil pore water increased more than 30 fold after adding both amendments, associated with significant increases in dissolved organic carbon and pH, whereas Zn and Cd significantly decreased. Biochar was most effective, resulting in a 10 fold decrease of Cd in pore water and a resultant reduction in phytotoxicity. Concentrations of PAHs were also reduced by biochar, with greater than 50% decreases of the heavier, more toxicologically relevant PAHs. The results highlight the potential of biochar for contaminated land remediation.
Show more [+] Less [-]Critical Limits for Hg(II) in soils, derived from chronic toxicity data
2010
Tipping, E. | Lofts, S. | Hooper, H. | Frey, B. | Spurgeon, D. | Svendsen, C.
Published chronic toxicity data for Hg(II) added to soils were assembled and evaluated to produce a data set comprising 52 chronic end-points, five each for plants and invertebrates and 42 for microbes. With end-points expressed in terms of added soil Hg(II) contents, Critical Limits were derived from the 5th percentiles of species sensitivity distributions, values of 0.13 μg (g soil)-1 and 3.3 μg (g soil organic matter)-1 being obtained. The latter value exceeds the currently recommended Critical Limit, used to determine Hg(II) Critical Loads in Europe, of 0.5 μg (g soil organic matter)−1. We also applied the WHAM/Model VI chemical speciation model to estimate concentrations of Hg2+ in soil solution, and derived an approximate Critical Limit Function (CLF) that includes pH; log [Hg2+]crit = −2.15 pH −17.10. Because they take soil properties into account, the soil organic matter-based limit and the CLF provide the best assessment of toxic threat for different soils. For differing representative soils, each predicts a range of up to 100-fold in the dry weight-based content of mercury that corresponds to the Critical Limit.
Show more [+] Less [-]Identification of a phytotoxic photo-transformation product of diclofenac using effect-directed analysis
2010
Schulze, Tobias | Weiss, Sara | Schymanski, Emma | Ohe, Peter Carsten von der | Schmitt-Jansen, Mechthild | Altenburger, R. | Streck, Georg | Brack, Werner
The pharmaceutical diclofenac (DCF) is released in considerably high amounts to the aquatic environment. Photo-transformation of DCF was reported as the main degradation pathway in surface waters and was found to produce metabolites with enhanced toxicity to the green algae Scenedesmus vacuolatus. We identified and subsequently confirmed 2-[2-(chlorophenyl)amino]benzaldehyde (CPAB) as a transformation product with enhanced toxicity using effect-directed analysis. The EC50 of CPAB (4.8 mg/L) was a factor of 10 lower than that for DCF (48.1 mg/L), due to the higher hydrophobicity of CPAB (log Kow = 3.62) compared with DCF (log Dow = 2.04) at pH 7.0.
Show more [+] Less [-]Ammonium Nitrogen Deposition as a Dominant Source of Nitrogen in a Forested Watershed Experiencing Acid Rain in Central Japan
2010
Ham, Young-Sik | Kobori, Hiromi | Kang, Joo-Hyon | Kim, Joon Ha
To clarify nitrogen (N) sources, the overall N budget in a forested watershed in Kanagawa Prefecture, Central Japan was estimated by measuring dissolved inorganic N (DIN; NH₄ ⁺ + NO₃ ⁻ + NO₂ ⁻) from Nov 2004 through Oct 2005. The estimated N budget (-1.43 kg N ha⁻¹ year⁻¹) showed that the N output rate (stream water N) was higher than the N input rate (bulk deposition N) in the watershed. The annual NO₂ ⁻ and NO₃ ⁻ input rates were 0.02 and 1.99 kg N ha⁻¹ year⁻¹, respectively. NH₄ ⁺ was the predominant source in this forested watershed, accounting for 71% (4.99 kg N ha⁻¹ year⁻¹) of DIN input rate. In addition, this study estimated rainfall pH, air temperature, and wind direction, which were considered as controlling factors related to the atmospheric deposition rate of NH₄ ⁺. This study showed that the rainfall NH₄ ⁺ was inversely proportional to the initial pH of the rainfall, which was calculated by adding the amount of H⁺ consumed by the dissociation process of NH₃₍aq₎ to the measured rainfall pH. This result implies that acid rain can elevate the solubility of NH₃₍g₎ and the dissociation capacity of NH₄ ⁺ throughout the process of precipitation. Also, this study provides strong evidence that the high NH₄ ⁺ deposition rate is mainly derived from NH₃₍g₎ emitted from livestock wastes under the NH₃ transport condition of warm summer and favorable wind direction.
Show more [+] Less [-]Quantification of Heavy Metals from A.M.D. Discharged into a Public Water Supply Dam in the Iberian Pyrite Belt (SW Spain) Using Centered Moving Average
2010
Grande, Jose Antonio | Jimenez, Antonio | Romero, Sixto | de la Torre, María Luisa | Gómez-Olivera, Tamara
In this work, the determination of moving averages is proposed as a method for quantifying metal, arsenic, and sulfate discharges into a water course undergoing acid mine drainage processes which flows into a public water supply dam in the Iberian Pyrite Belt. The analysis of the results obtained by applying moving averages shows that the highest metal and sulfate concentrations occur in October, coinciding with the first rainfall and the sponging of mine dumps, with November and December being the months when the highest contributions to the Andevalo Dam take place. The discharge of acid mine waters with its corresponding metal load into the Andevalo Dam means, for a single hydrological year, more than 6,000 t of sulfates, almost 600 t of iron, and 1 t of As, of special relevance for the hydrochemical quality of the stored waters. When they arrive at the dam, these metals precipitate, since the water pH is near 7, and remain latent in the bottom sediment as long as the chemical makeup of the dam water does not change.
Show more [+] Less [-]Preparation, Characterization, and Environmental Application of Crosslinked Chitosan-Coated Bentonite for Tartrazine Adsorption from Aqueous Solutions
2010
Wan Ngah, Wan Saime | Ariff, Noorul Farhana Md | Hanafiah, Megat Ahmad Kamal Megat
The preparation, characterization, and environmental application of crosslinked chitosan-coated bentonite (CCB) beads for tartrazine adsorption have been investigated. CCB beads were characterized by using Fourier transform infrared spectrophotometer (FTIR), scanning electron microscope (SEM), and Brunauer-Emmett-Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore size distribution analyses were also determined. The values of pH of the aqueous slurry and pH of zero point charge (pHZPC) were almost equal. The adsorption at equilibrium of tartrazine was found to be a function of pH of the solution, stirring rate, contact time, and tartrazine concentration. The optimum conditions for tartrazine adsorption were pH 2.5, stirring rate of 400 rpm and contact time of 80 min. Pseudo-first-order and pseudo-second-order models were used to analyze the kinetics of adsorption with the latter found to agree well with the kinetics data, suggesting that the rate determining step may be chemisorption. The two most common isotherm models, Langmuir and Freundlich, were used to describe the adsorption equilibrium data. On the basis of Langmuir isotherm model, the maximum adsorption capacities were determined to be 250.0, 277.8, and 294.1 mg g⁻¹ at 300, 310, and 320 K, respectively. Desorption studies were carried out at different concentrations of EDTA, H₂SO₄, and NaOH. All desorbing solutions showed poor recovery of tartrazine.
Show more [+] Less [-]Effectiveness of Potassium Ferrate (K₂FeO₄) for Simultaneous Removal of Heavy Metals and Natural Organic Matters from River Water
2010
This study has investigated how to simultaneously remove both heavy metals (Cu, Mn, and Zn) and natural organic matters (NOM; humic acid and fulvic acid) from river water using potassium ferrate (K₂FeO₄), a multipurpose chemical acting as oxidant, disinfectant, and coagulant. In water sample including each 0.1 mM heavy metal, its removal efficiency ranged 28-99% for Cu, 22-73% for Mn, and 18-100% for Zn at the ferrate(VI) doses of 0.03-0.7 mM (as Fe). The removal efficiency of each heavy metal increased with increasing pH, whereas an overall temperature did not make any special effect on the reaction between the heavy metal and ferrate(VI). A high efficiency was achieved on the simultaneous treatment of heavy metals (0.1 mM) and NOM (10 mg/l) at the ferrate(VI) doses of 0.03-0.7 mM (as Fe): 87-100% (Cu), 31-81% (Mn), 11-100% (Zn), and 33-86% (NOM). In the single heavy metal solution, the optimum ferrate dose for treating 0.1 mM Cu or Mn was 0.1 mM (as Fe), while that for treating 0.1 mM Zn was 0.3 mM (as Fe). In the mixture of three heavy metals and NOM, on the other hand, 0.5 mM (as Fe) ferrate(VI) was determined as an optimum dose for removing both 0.1 mM heavy metals (Cu, Mn, and Zn) and 10 mg/l NOM. Prior to the addition of ferrate(VI) into the solution of heavy metals and NOM (HA or FA), complexes were formed by the reaction between divalent cations of heavy metals and negatively charged functional groups of NOM, enhancing the removal of both heavy metals and NOM by ferrate(VI).
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