Relationship between Mineral Soil Surface Area and the Biological Degradation of Biosolids Added to Soil

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.

Relationship Between Mineral Soil Surface Area and Carbon Sequestration Rate for Biosolids Added to Soil

“…After annual biosolid application for 15-22 years to each field, the modeled SOC concentrations and amount of C sequestered were estimated by applying DRM. Figure 4 provides example plots for two of the selected fields [15]. The SOC measured and estimated with the DRM matched very good base on the coefficient of determinations between them (average coefficient of determination is 0.94), indicating that the curve fitting technique was able to provide biomass yield and degradation rate.…”

“…Group I consisted of 20 fields of "coarse" mine spoil soils, primarily Lenzburg (fine-loamy, mixed, active, calcareous, mesic Haplic Udarents) and Lenzwheel soil series [14]. Group II is primarily Rapatee (fine-silty, mixed, superactive, nonacid, mesic Mollic Udarents) soil series and contains nine fields of "fine" mine spoil soils, [14,15]. Group III contains 12 fields of various non-mined soils that were degraded by intensive cultivation or overgrazing [14,15] (Figure 2).…”

“…The DRM can be applied to estimate (1) the biosolid degradation as a function of time, (2) the SOC portion due to biosolids remaining, and (3) the residual microbial biomass (C sequestered). To apply the DRM, the appropriate biomass yields and degradation rate that are estimated from curve fitting are needed [15]. It should be noticed that the microbial biomass yield is considered as constant (35-40%) determined by curve fitting results.…”

“…It was assumed that the soil particles are spherical with a smooth surface and the number of soil particles was estimated by Eq. (8) [15]:…”

“…The SOC measured and estimated with the DRM matched very good base on the coefficient of determinations between them (average coefficient of determination is 0.94), indicating that the curve fitting technique was able to provide biomass yield and degradation rate. Therefore, DRM model is allowed to provide acceptable estimates of the measured SOC values and sequestration amounts [15].…”