Contrasting effect of zirconium-, iron-, and zirconium/iron-modified attapulgites capping and amendment on phosphorus mobilization in sediment.

In this research, the sorption characteristics and mechanism of phosphate on zirconium-modified attapulgite (Zr-ATP), iron-modified attapulgite (Fe-ATP), and zirconium/iron co-modified attapulgite (Zr/Fe-ATP) prepared by a simple impregnation method were studied, and the impacts of Zr-ATP, Fe-ATP, and Zr/Fe-ATP amendment and capping on the migration of phosphorus (P) from sediments to overlying waters were investigated. The results showed that Zr-ATP and Zr/Fe-ATP possessed stronger adsorption ability for phosphate in aqueous solution than Fe-ATP. The ligand replacement of the hydroxyl group with the phosphate anion to form the inner-sphere phosphate complex played a crucial role in the adsorption process of phosphate on Zr-ATP, Fe-ATP, and Zr/Fe-ATP. Most of the phosphate ions bound by Zr-ATP and Zr/Fe-ATP were in the form of caustic soda solution-extractable inorganic P (NaOH-IP) and residual P (Res-P), and it is hard for these P species to be re-released into water under the circumstances of reducing environment and normal pH (5-9). The ratio of mobile P to total P of Fe-ATP loaded with phosphate was much higher than those of Zr-ATP and Zr/Fe-ATP loaded with phosphate, indicating that Fe-ATP-bound phosphate has a higher re-releasing risk than Zr-ATP-bound and Zr/Fe-ATP-bound phosphate. Zr-ATP, Fe-ATP, and Zr/Fe-ATP amendment all can reduce the releasing risk of P from sediments to overlying waters. The amendment of sediment with Zr-ATP and Zr/Fe-ATP can both induce the conversion of redox-sensitive P (BD-P) to NaOH-IP and Res-P in the sediment, making the phosphorus in the sediment more stable. However, the amendment of sediment with Fe-ATP can only induce the conversion of HCl-P to NaOH-IP in the sediment and had a negligible effect on the inorganic P activity in the sediment. Zr-ATP, Fe-ATP, and Zr/Fe-ATP capping all can reduce the risk of P release from sediment into the overlying water, and Zr-ATP and Zr/Fe-ATP capping had a better reduction efficiency of internal P liberation to the overlying water than Fe-ATP capping. Zr-ATP, Fe-ATP, and Zr/Fe-ATP capping all can give rise to the reduction of pore water SRP and diffusive gradient in thin-film (DGT)-labile P in the upper sediment. This is beneficial to the control of P releasing from sediment into the overlying water by the Zr-ATP, Fe-ATP, and Zr/Fe-ATP capping. The findings of this work suggest that Zr-ATP and Zr/Fe-ATP are promising active capping or amendment materials for internal P loading management in surface water bodies.

Anti-fungal activity of moso bamboo (Phyllostachys pubescens) leaf extract and its development into a botanical fungicide to control pepper phytophthora blight.

Moso bamboo (Phyllostachys pubescens, Gramineae) is a well-known medicinal and edible plant found in China with various bioactivities, but few systematic studies address the utilization of its anti-fungal activity. The extract of moso bamboo leaf showed good anti-fungal activity to Phytophthora capsici, Fusarium graminearum, Valsa mali Miyabe et Yamada, Botryosphaeria dothidea, Venturia nashicola, and Botrytis cinerea Pers, with inhibitory rate of 100.00%, 75.12%, 60.66%, 57.24%, 44.62%, and 30.16%, respectively. Anti-fungal activity was different by the difference of samples picking time and location. The extract showed good synergistic effects with carbendazim at the ratios of 9:1 and 15:1 (extract : carbendazim), and the co-toxicity coefficients were 124.4 and 139.95. Compound 2 was isolated and identified as the main active component, with the EC50 value of 11.02 mg L-1. Then, the extract was formulated as a 10% emulsion in water, which was stable and had no acute toxic effects. Moreover, a field trial about this formulation was assayed to control pepper phytophthora blight, with the control effect of 85.60%. These data provided a better understanding of the anti-fungal activity and relevant active component of moso bamboo leaf extract. Taken together, our findings illustrated that bamboo leaf extract could be developed and utilized as a botanical fungicide or fungicide adjuvant.