Organic matter mineralization rate

As shown in Fig. 3, CHEMGL considers 10 major well-mixed compartments air boundary layer, free troposphere, stratosphere, surface water, surface soil, vadose soil, sediment, ground water zone, plant foliage and plant route. In each compartment, several phases are included, for example, air, water and solids (organic matter, mineral matter). A volume fraction is used to express the ratio of the phase volume to the bulk compartment volume. Furthermore, each compartment is assumed to be a completely mixed box, which means all environmental properties and the chemical concentrations are uniform in a compartment. In addition, the environmental properties are assumed to not change with time. Other assumptions made in the model include continuous emissions to the compartments, equilibrium between different phases within each compartment and first-order irreversible loss rate within each compartment [38]. 

Nitrate reduction rates have been shown to be highly correlated to soil organic matter and soluble or available organic carbon (determined as extractable organic carbon) in soils. Several studies have shown a strong relationship between nitrate reduction and available carbon in soils (Buford and Bremner, 1975 Reddy et al., 1982). Nitrate reduction in wetland soils can be coupled to organic matter mineralization (see Chapter 5), as facultative bacteria use... 

Although a vast amount of literature exists on the reduction of Fe(III) and Mn(IV) in soils and sediments, little information is available on the overall kinetics of reduction. However, the kinetics of reduction of other electron acceptors such as oxygen, nitrate, and sulfate have been widely studied and reported (see Chapters 6,7, and 11). The kinetics of Fe(III) and Mn(IV) reduction are influenced by interaction of bacterial cells with solid phases of these compounds (Roden and Wetzel, 2002). Microbial reduction of Fe(lll) oxides was reported to follow first-order kinetics in wetland soils and rates of reduction were directly linked to organic matter mineralization (Roden and Wetzel, 2002). The first-order rate constants were in the range of 0.175-0.346 day, suggesting a turnover rate of... 

Soil—water nutrient exchange rates Substrate-induced respiration Arginine mineralization Microbial diversity Cellular fatty adds rRNA sequence analysis Organic matter accretion rates Cs-137 and Pb-210 profiles Phosphate sorption index Equilibrium phosphorous concentration (EPCo)... 

When rainfall intensity exceeds infiltration rate and surface-storage capacity has been reached, overland flow begins. The transfer of dissolved pesticides from the soil matrix to overland flow consists of several mechanisms desorption from soil organic matter, mineral surfaces and plant residues dissolution of insecticide crystals or granules and diffusive and turbulent transport of dissolved insecticide from soil water into overland flow (2, 62). The relative importance of each process depends on the physico-chemical properties of the chemical, formulation, initial placement, soil properties, recent hydraulic history and vegetation (62). 

Soil minerals play a stabilizing role in organic matter. The Al and Fe that complex and stabilize organic matter against microbial decomposition are released from soil minerals during soil formation. The supply rates apparently control the content of soil organic matter to a great extent. This is demonstrated by the relationship between pyrophosphate-extractable C and pyrophosphate-extractable Al plus Fe (Wada 1995). 

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