No abstract

No abstract

No abstract

Phosphorus (P) is limiting nutrient in soil system. The P availability in soil strongly depend on Iron (Fe) speciation. Colloidal iron phosphate (FePO 4coll ) is an important phosphorus (P) fraction in soil solution that carry P from soil to water bodies. This study tested the hypothesis that phytate exudation by Pteris vittata (P. vittata) can dissolve FePO 4coll that leads to release of P and Fe. The phytate exudation in P. vittata increased from 434−2136 mg kg −1 as the FePO 4coll concentration increased from 0−300 mM. The total P in P. vittata tissue increased from 2.88 to 8.28 g kg −1 , the trichloroacetic acid P fractions (TCA fractions) were: inorganic P (0.86-5.10 mg g −1 ), soluble organic P (0.25-0.87 mg g −1 ), and insoluble organic P (0.16-2.03 mg g −1 ) which leads to higher biomass as FePO 4coll increased from 0−300 mM.The linear regression analysis showed that FePO 4 solubilizing activity has a positive correlation with TP, TCA P fractions in P. vittata, TP in growth media, and root exudates. This study shows that phytate exudation dissolved the FePO 4coll due to the chelation effect of phytic acid on Fe, and due to the high Fe-P solubilizing activity in root exudates of P. vittata.

Background Trace amounts of nitrogen and phosphorus can easily trigger eutrophication damage in surface water, while cost-effective adsorption treatment is in prospect for clearing these pollutants simultaneously and efficiently. In this study, engineered adsorbents decorated with ZnFe-LDH by alkaline coprecipitation (3-6 mm, with modified ceramsite as CZF and modified volcanic rock as VZF) were prepared for NH 4 + and H 2 PO 4 - co-adsorption from aqueous solutions.Results Coexisting ions showed great effects on phosphate adsorption, especially Ca 2+ and CO 3 2- , and humic acid exhibited only a limited shielding impact on co-adsorption properties. Though comprehensive tests presented that the maximum captured amount of ammonium and phosphate occurred at pH 7, the isotherm and kinetic results suggest that two adsorbents preferentially adsorbed each pollutant. Specifically, the maximum uptake quantity of NH 4 + (15.55 mg-N g -1 ) and H 2 PO 4 - (11.21 mg-P g -1 ) were achieved by VZF and CZF, respectively, and controlled by physisorption and chemisorption distinctively, revealing that contaminants were cleared in disparate ways. Performances of seven consecutive adsorption/desorption cycles using 5% NaOH regenerant suggested that CZF retained 71.9% of PO 4 - removal efficiency, and VZF retained 47.9% of the NH 4 + adsorption rate, implying the strong reusability of ZnFe-LDH-modified adsorbents. A dynamic study has assessed that with 1 kg of combined modified adsorbents, approximately 527 L of polluted runoff flow could be continuously treated to below the National limits within one adsorption cycle.Conclusion Comparing with other parallel adsorbents, ZnFe-LDH-modified adsorbent is promising in eliminating eutrophication due to their superior capacity, stability, renewability, and non-toxicity.