Contrasting effects of different types of organic material on surface area and microaggregation of goethite

Short-term effects of plant litter addition on mineral surface characteristics of young sandy soils

“…However, this decrease in enthalpy was only significant for PS. A negative correlation between C BET and SOM (R = −0.40) was found as was described to be characteristic for soils (Kaiser and Guggenberger, 2003;Mödl et al, 2007). An increasing sorption of SOM caused a decrease of the C constant in the BET equation by replacing mineral surface area with the surface area of SOM.…”

Quaternary ammonium compounds in soil: implications for antibiotic resistance development

“…Many clay minerals in soil are covered by patchy surfaces with SOM and oxides (Mayer 1999;Mödl et al 2007;Kaiser and Guggenberger 2007); frequently they are involved in the formation of microaggregates (Totsche et al 2017), and cations may block intercalation if not replaced by high QAAC contents. In addition, long-term applications of manure or sewage sludge, or irrigation with wastewater form conditions different to those studied in the lab or with pure compounds.…”

Extent and nature of organic coverage of soil mineral surfaces assessed by a gas sorption approach

“…This correlation implies that mineral surfaces are occluded in direct proportion to the accretion of OM (which has low SSA) that surrounds high-SSA mineral particles. The surface area of minerals is generally held within micropores or mesopores that are formed by aggregation of primary grains such as sub-micrometer phyllosilicates or metal oxides (Mayer et al, 2004 and references therein), so that occlusion of aggregates can shield high-SSA internal pores with a low-SSA external sheath (Mayer and Xing, 2001;Kaiser and Guggenberger, 2003;Mikutta et al, 2004;Kaiser and Guggenberger, 2007;Mödl et al, 2007). The roughly linear relationship found here suggests that the probability of the organic occlusion of mineral surfaces may be directly proportional to the volume fraction of OM and is consistent with strong association between the OM and mineral grains as indicated by density separations (Wagai et al, 2008).…”

“…Note that this level of OM loading is higher than the level required to saturate sorption sites on mineral surfaces in most laboratory experiments. When maximum sorption of naturally-occurring dissolved OM is reached at common soil pH values, OM loadings are no more than 2.3-3.4 mg-OC m − 2 for goethite and typically much lower for other minerals including phyllosilicate clays (Tipping, 1981;Benke et al, 1999;Chorover and Amistadi, 2001;Kaiser and Guggenberger, 2003;Mödl et al, 2007). While laboratory sorption doesn't often achieve full organic coverage (Kaiser and Guggenberger, 2003;Lang and Kaupenjohann, 2003;Mödl et al, 2007), OM association with goethite around maximum sorptive capacity (1.9 mg-OC m − 2 in this case) led to bulky OM accumulations presumably via hydrophobic interactions embedding some of the goethite particles (Kaiser and Guggenberger, 2007).…”

“…The C-constant can be used to quantitatively determine the fractions of exposed surfaces that are organic or inorganic, by using a mixing equation between organic and inorganic endmembers (Mayer, 1999). This approach fails, however, as a quantitative measure of surface composition in some soils because of the presence of micropores (b2 nm diameter) that are often associated with iron and aluminum hydrous oxides (e.g., Mödl et al, 2007). Soil minerals with high microporosity have higher C-constant values compared to the soil minerals without them (Mayer and Xing, 2001) and the micropores are preferentially covered with OM compared to other parts of mineral surfaces in sorption experiments (Kaiser and Guggenberger, 2003;Mikutta et al, 2004;Filimonova et al, 2006).…”