Sugarecane molasse and vinasse added as microbial growth substrates increase calcium carbonate content, surface stability and resistance against wind erosion of desert soils.

Wind erosion is one of the main factors of soil degradation and air pollution in arid and semi-arid regions. In this study we evaluated microbial-induced carbonate precipitation (MICP) as an alternative soil conservation method against wind erosion using sugar cane molasse and vinasse as growth substrates in comparison to tryptic soy broth (TSB). The three substrates were applied in laboratory tests with and without addition of MICP cementing solution (1 M urea plus calcium chloride) to two sandy soils differing in calcium carbonate content. The performance of MICP solution inoculated with a cultured urease-producing strain of Sporosarcina pasteurii was compared to that of an autoclaved MICP solution. For control we also performed a blank treatment without substrate, MICP solution and inoculation. In addition to lab tests in which we determined the effects of treatments on soil pH, electrical conductivity (EC), calcium carbonate (CaCO3) content and surface penetration resistance, we performed wind tunnel experiments to determine soil loss by deflation under different wind velocities. Applying vinasse and molasse strongly increased soil CaCO3 content and penetration resistance, with and without addition of inoculated or non-inoculated MICP solution. Vinasse generally had stronger effects than molasse, while TSB was less effective, especially on penetration resistance. The addition of MICP solution in most treatments did not enhance but rather decrease the substrate effects. In the treatments with vinasse and molasse, increase in penetration resistance translated into substantially decreased soil loss in the wind tunnel tests, down to around one third of the loss in the blank treatment. In contrast, soil loss substantially increased in the treatments with TSB, probably due to the high input of sodium with this substrate. Our results show that molasse and, even more, vinasse can have a strong soil stabilization effect against wind erosion, which is primarily related to the formation of CaCO3 content and does not depend on additional amendments. Thus, these substrates have a great potential to be used on their own as environmentally friendly and cost-effective amendments to control wind erosion of bare sandy soils in arid environments.

Fate and transport modeling of phthalate esters from biosolid amended soil under corn cultivation.

Phthalate esters (PAEs) are prevalent in the environment due to the broad range of industrial, agriculture and domestic applications. The ubiquitous use of PAEs has resulted in their potential to reach groundwater sources through application of agri-chemicals and municipal biosolids. A study was conducted to monitor the fate and transport of seven commonly detected PAEs in the environment including: dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl butyl phthalate (BBP), bis(di-ethyl hexyl) phthalate (DEHP), di-n-octyl phthalate (DnOP), dipentyl phthalate (DPP), and di-n-butyl phthalate (DnBP). Biosolids sourced from the Halifax Regional Municipality were applied at three rates on field-based lysimeter cells which were cropped to corn (Zea mays) for one growing season. In the present study, breakthrough curves (BTCs) were established for phthalates leaching from a corn-cultivated agricultural soil profile. The HYDRUS-1D model and a two-site sorption model were applied to predict transport parameters of PAEs using an inverse solution approach. Results of our research revealed that higher PAE adsorption was observed based on increasing carbon chain number. In addition, higher values of F (i.e. the fraction of type-1 sorption sites assumed to be in equilibrium with the solution phase) and lower values of D (i.e. dispersion coefficient) were observed for PAEs with large carbon chains which was validated both through the empirical dataset and the model simulations.