Search for: All records

Perchlorate (ClO4–) is a pervasive, harmful, and inert anion on both Earth and Mars. Current technologies for ClO4– reduction entail either harsh conditions or multicomponent enzymatic processes. Herein, we report a heterogeneous (L)Mo–Pd/C catalyst directly prepared from Na2MoO4, a bidentate nitrogen ligand (L), and Pd/C to reduce aqueous ClO4– into Cl– with 1 atm of H2 at room temperature. A suite of instrument characterizations and probing reactions suggest that the MoVI precursor and L at the optimal 1:1 ratio are transformed in situ into oligomeric MoIV active sites at the carbon–water interface. For each Mo site, the initial turnover frequency (TOF0) for oxygen atom transfer from ClOx– substrates reached 165 h–1. The turnover number (TON) reached 3840 after a single batch reduction of 100 mM ClO4–. This study provides a water-compatible, efficient, and robust catalyst to degrade and utilize ClO4– for water purification and space exploration. 

Aeolian dust deposition is an important phosphorus (P) input to terrestrial ecosystems, but its influence on P dynamics during long-term ecosystem development remains poorly understood. In this study, we characterized P speciation using P K-edge XANES spectroscopy in surface soils (0–15 cm, A horizon) and contemporary aeolian dust collected at each site of a 3000-ky volcanic soil chronosequence in a cool, semi-arid environment. Phosphorus speciation in dust was dominated by calcium-bound P (Ca-P; 54–74%), with 11–23% iron and aluminum-bound P [(Fe + Al)-P] and 7–25% organic P (Po). In soils, Po contributed 1–23% of total P, being greater in older soils; however, the proportions of Ca-P (16–39%) and (Fe + Al)-P (48–82%) fluctuated with increasing weathering over the soil chronosequence. These soil fluctuations resulted from the accumulation and preservation of alkaline aeolian dust during pedogenesis in the semi-arid climate, which significantly increased soil Ca-P while decreasing the total amounts and relative abundances of soil (Fe + Al)-P. We suggest that the effects of an aeolian dust input on soil P transformations are functions of the relative magnitude and chemical composition of the dust input and the soil weathering intensity. For a given source of dust, when the net dust flux is greater than the weathering rate, dust accumulates and thus alters the pattern of P transformations during pedogenesis; otherwise, the dust influence on soil P transformations is negligible. By accurately identifying the chemical nature of P pools, our work highlights the advantage of P K-edge XANES spectroscopy over chemical extractions in examining soil P dynamics, and demonstrates how dust inputs can modify the Walker and Syers model of pedogenic P transformations in semi-arid environments. Overall, this work provides a foundation for understanding how dust influences P cycling during soil and ecosystem development, and indicates that dust inputs and composition, and the soil weathering rate, all must be considered for developing integrated climate-biogeochemical models with predictive power in terrestrial ecosystems. 

Aeolian dust deposition is an important phosphorus (P) input to terrestrial ecosystems, but its influence on P dynamics during long-term ecosystem development remains poorly understood. In this study, we characterized P speciation using P K-edge XANES spectroscopy in surface soils (0–15 cm, A horizon) and contemporary aeolian dust collected at each site of a 3000-ky volcanic soil chronosequence in a cool, semi-arid environment. Phosphorus speciation in dust was dominated by calcium-bound P (Ca-P; 54–74%), with 11–23% iron and aluminum-bound P [(Fe + Al)-P] and 7–25% organic P (Po). In soils, Po contributed 1–23% of total P, being greater in older soils; however, the proportions of Ca-P (16–39%) and (Fe + Al)-P (48–82%) fluctuated with increasing weathering over the soil chronosequence. These soil fluctuations resulted from the accumulation and preservation of alkaline aeolian dust during pedogenesis in the semi-arid climate, which significantly increased soil Ca-P while decreasing the total amounts and relative abundances of soil (Fe + Al)-P. We suggest that the effects of an aeolian dust input on soil P transformations are functions of the relative magnitude and chemical composition of the dust input and the soil weathering intensity. For a given source of dust, when the net dust flux is greater than the weathering rate, dust accumulates and thus alters the pattern of P transformations during pedogenesis; otherwise, the dust influence on soil P transformations is negligible. By accurately identifying the chemical nature of P pools, our work highlights the advantage of P K-edge XANES spectroscopy over chemical extractions in examining soil P dynamics, and demonstrates how dust inputs can modify the Walker and Syers model of pedogenic P transformations in semi-arid environments. Overall, this work provides a foundation for understanding how dust influences P cycling during soil and ecosystem development, and indicates that dust inputs and composition, and the soil weathering rate, all must be considered for developing integrated climate-biogeochemical models with predictive power in terrestrial ecosystems.