Nitrate reduction by commercially available nitrate reductases: bio-catalytic potentials and enzymatic activities in the presence of metals ions.

Commercially available nitrate reductases from corn, Aspergillus niger, and Escherichia coli have the potential to mitigate excess nitrate in soils and water sources. In this study, in vitro experiments were conducted to evaluate nitrate reduction by commercially available nitrate reductases from three major sources (plant, fungi and bacteria), their biocatalytic potentials and activities in the presence of varied concentrations of Cd(2+), Cu(2+), Ni(2+), Co(2+), Cr(6+), Fe(2+), Zn(2+), and Pb(2+). The results showed that the activity, V (max), and potential to reduce nitrate was in the order: corn > A.

Mercury speciation and effects on soil microbial activities.

To study Hg toxicity on soil microbes and their activities, it is necessary to understand its various forms in soils. The objectives of this study were to investigate Hg speciation in four soil types spiked with Hg (300 mg kg(-1) soil) and its effects on soil microbial respiration and enzymes (amidohydrolases and phosphatase) activities. An assessment of the chemical forms, amounts, reactions, and mobility of Hg in soils and sediments is of significant importance to improve and maintain soil and environmental health and sustainability.

X-ray absorption near edge structure study of lead sorption on phosphate-treated kaolinite.

Presorbed phosphate significantly increases Pb sorption on the phyllosilicate kaolinite in the pH range from 4to 8. The sorbed Pb-to-P molar ratios over this pH range stray little from the molar ratio found in the mineral pyromorphite, suggesting sorbed phosphate reacts with soluble Pb to form a surface precipitate similar to pyromorphite. X-ray absorption near edge structure (XANES) studies at the Pb L3-edge support this interpretation.

Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions.

Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.