Bioelectricity generation from three ornamental plants: Chlorophytum comosum,Chasmanthe floribunda and Papyrus diffusus

In the present study, bioelectricity generation using a living plant in soil was achieved by converting solar energy into electricity on the principles of plant photosynthesis. The plants Chlorophytum comosum, Chasmanthe floribunda and Papyrus diffuses were used in microbial fuel cells (MFCs) and produced, respectively, a maximum current of 25, 31 and 19 mA/m², without the use of any nutrient or membrane. In this study, the importance of light was demonstrated by the high current values generated during daytime, and the microorganisms at the anode-rhizosphere interface were examined.     

Factors affecting metribuzin retention in Algerian soils and assessment of the risks of contamination

Metribuzin is a widely used herbicide around the world but it could lead to soil and water contamination. Metribuzin retention on a silty–clay agricultural soil of Algeria was studied in laboratory batch experiments to assess the contamination risk of the groundwater. Factors conditioning the fate of metribuzin were investigated: soil nature, metribuzin formulation, NPK fertilizer, and soil pH. Freundlich sorption isotherms gave the coefficients K _F between 1.2 and 4.9 and 1/n _a between 0.52 and 0.93. The adsorption is directly dependent on organic and clay soil contents. Formulated metribuzin (Metriphar) reduces the adsorption (K _F?=?1.25) compared to pure metribuzin (K _F?=?2.81). The addition of an NPK fertilizer decreases the soil pH (6.67 for the soil without fertilizer and 5.86 for 2 % of fertilizer) and increases metribuzin adsorption (K _F is 4.83 for 2 % of fertilizer). The pH effect on the adsorption is corroborated in experiments changing the soil pH between 5 (K _F is 4.17) and 8 (K _F is 1.57) under controlled conditions. Desorption isotherms show a hysteresis and only 30 to 40 % of the initially adsorbed metribuzin is released. The estimated GUS index is ≥2.8 for a DT50?≥?30 days. K _F values and the hysteresis show that metribuzin is little but strongly retained on the soil. Formulated metribuzin and addition of fertilizer affect the retention. However, the GUS index indicates a high mobility and a significant risk of leaching. The most appropriate risk management measure would be an important increase in organic matter content of the soil by addition of organic amendments.