No abstract

Geochemical and biological processes that operate in the soil matrix and on the soil surface are important to the degradation of biosolids in soil. Due to the large surface area of soils it is assumed that the microbial ecology is associated with mineral soil surface area. The total mineral surface areas were determined for soils from eight different fields selected from a long term study of annual biosolids application to 41 fields in central Illinois varying in size from 3.6 to 66 ha. The surface areas for the soils varied from 1 to 9 m 2 /g of soil. The biological degradation rates for the eight soils were determined using a biological degradation rate model (DRM) and varied from 0.02 to 0.20/year´1. Regression analysis revealed that the degradation rate was positively associated with mineral soil surface area (1 m 2 /g produces 0.018 year´1 increase in the degradation rate). The annual soil sequestration rate was calculated to increase from 1% to 6% when the soil total surface area increased from 1 to 9 m 2 /g of soil. Therefore, land application of biosolids is an effective way to enhance carbon sequestration in soils and reduce greenhouse gas emissions.

In this work, the effect of oxidation pretreatment on the enzymatic hydrolysis of cellulose in tobacco stems was evaluated. A comparison was made between the effect of H2O2 pretreatment and conventional alkali pretreatment on the weight loss of cellulose, lignins and hemicelluloses of tobacco stems. The effects of H2O2 concentration, pretreatment time and temperature on the enzymatic hydrolysis of tobacco stems were investigated. This pretreatment could give a higher recovery of cellulose and better removal of lignin and hemicellulose than alkali‐only pretreatment. Compared with the untreated stems, the yield of reducing sugar pretreated by H2O2 pretreatment (pH 11.5, 0.6% H2O2) for 9 h at 60C increased 347.2%. The results of scanning electron microscope and X‐ray diffraction analysis also showed that the structural and crystalline properties of the tobacco stems were changed by pretreatment, and they were in favor of the following enzymatic hydrolysis. The optimal pretreatment conditions were 60C of temperature, 0.6% of H2O2 concentration and 9 h of time, which were calculated by orthogonal experiments. PRACTICAL APPLICATIONS Pretreatment on lignocellulosic materials to disrupt the recalcitrant structure is helpful for their bioconversion into low‐molecular weight substances. The tobacco stems were pretreated by H2O2 oxidation before subjecting to enzymatic hydrolysis by cellulase in this work. This pretreatment was confirmed effectively to improve the recovery of celllulose, and helpful to remove lignin and hemicellulose. Moreover, the yield of reducing sugar produced by cellulase hydrolysis was apparently improved. These results were helpful for the extensive development of tobacco stems.

This paper presents ultrafine-particle (UFP) emission factors (EFs) as a function of vehicle mode of operation (free flow and congestion) using (1) concurrent 5 min measurements of UFPs and carbon monoxide (CO) concentration, wind speed and direction, traffic volume and speed near a roadway that is restricted to light-duty vehicles (LDVs) and (2) inverse dispersion model calculations. Short-term measurements are required to characterize the highly variable and rapidly changing UFP concentration generated by vehicles. Under congestion conditions, the UFP vehicle EFs increased from 0.5 × 10(13) to 2 × 10(13) (particles km(-1) vehicle(-1)) when vehicle flow increased from 5500 to 7500 vehicles/h. For free-flow conditions, the EF is constant at 1.5 × 10(13) (particles km(-1) vehicle(-1)). The analysis is based on the assumption that air-quality models adequately describe the dilution process due to both traffic and atmospheric turbulence. The approach used to verify this assumption was to use an emission factor model to determine EFs for CO and then estimate dilution factors using measured CO concentrations. This procedure eliminates the need to rely only on air quality models to generate dilution factors. The EFs are suitable for fleet emissions under real-world traffic conditions.

The paper provides emission factors (EFs) that are a function of traffic volume and mode of operation (free flow and congestion) for LDVs under real-world conditions. The good agreement between monitoring and modeling results indicates that high-resolution, simultaneous measurements of air quality and meteorological and traffic conditions can be used to determine real-world, fleet-wide vehicle EFs as a function of vehicle mode of operation under actual driving conditions.