Nano-Bioremediation of Arsenic and Its Effect on the Biological Activity and Growth of Maize Plants Grown in Highly Arsenic-Contaminated Soil.

Arsenic (As)-contaminated soil reduces soil quality and leads to soil degradation, and traditional remediation strategies are expensive or typically produce hazardous by-products that have negative impacts on ecosystems. Therefore, this investigation attempts to assess the impact of As-tolerant bacterial isolates via a bacterial Rhizobim nepotum strain (B1), a bacterial Glutamicibacter halophytocola strain (B2), and MgO-NPs (N) and their combinations on the arsenic content, biological activity, and growth characteristics of maize plants cultivated in highly As-contaminated soil (300 mg As Kg-1). The results indicated that the spectroscopic characterization of MgO-NPs contained functional groups (e.g., Mg-O, OH, and Si-O-Si) and possessed a large surface area. Under As stress, its addition boosted the growth of plants, biomass, and chlorophyll levels while decreasing As uptake. Co-inoculation of R. nepotum and G. halophytocola had the highest significant values for chlorophyll content, soil organic matter (SOM), microbial biomass (MBC), dehydrogenase activity (DHA), and total number of bacteria compared to other treatments, which played an essential role in increasing maize growth. The addition of R. nepotum and G. halophytocola alone or in combination with MgO-NPs significantly decreased As uptake and increased the biological activity and growth characteristics of maize plants cultivated in highly arsenic-contaminated soil. Considering the results of this investigation, the combination of G. halophytocola with MgO-NPs can be used as a nanobioremediation strategy for remediating severely arsenic-contaminated soil and also improving the biological activity and growth parameters of maize plants.

Turning, compacting and the addition of water as factors affecting gaseous emissions in farm manure composting.

Composting allows simple management of animal manure but excessive aeration can increase emissions of polluting gases such as ammonia or nitrous oxide. The aim of the present work was to determine the effect of three techniques--turning, compacting and the addition of water--on gaseous emissions. One ton of cattle manure and 3 tons of turkey manure were composted in two and four cells for 46 and 51 days respectively. The manure was either turned, wetted, or compacted. Emissions of carbon dioxide, water vapor, ammonia and nitrous oxide were monitored. The results show that turning did not alter the free air space. Compacting can be used specifically to reduce the water loss. A reduction of free air space by 20-60%, either by compacting or adding water (or both), reduced the ammonia and nitrous oxide emissions by 30-70%.