Microbial Mineralization of Organic Compounds in an Acidic Agricultural Soil: Effects of Preadsorption to Various Soil Constituents

Abstract

This study investigated the interactions between organic chemicals and components of the soil matrix and their effects on subsequent microbial mineralization kinetics. Five 14 C-labeled chemicals (anionic, cationic, and nonionic surfactants) were aseptically sorbed to montmorillonite, kaolinite, illite, sand, humic acids, and fulvic acids. Small amounts of these sorbed chemicals were dosed to an acidic, sludge-amended agricultural soil (Rossmoyne) to a final added chemical concentration of 50 ng g Ϫ1 . Controls received the same final added concentration of the chemicals in water. The ratio of sorbed chemical to soil was kept low to minimize changes to the soil mineralogy, chemistry, and microbiology. Microbial mineralization of the chemicals to 14 CO 2 was measured over a period of 60 to 70 d, and the data were fitted to first-order and 3/2-order mineralization models. Association with the soil constituents inhibited the mineralization of the chemicals in the following rank (from least to greatest effect): controls ഠ sand Ͻ kaolinite Ͻ illite Ͻ montmorillonite ഠ humic acids Ͻ fulvic acids. These experiments demonstrated that interactions with some soil constituents (kaolinite, illite, and sand) had little effect on the microbial metabolism of these chemicals, while montmorillonite, humic acids, and especially fulvic acids significantly decreased the bioavailability of the chemicals to the microbial community. The first group of soil constituents had little influence on the mineralization kinetic parameters, whereas the latter significantly reduced at least one of the parameter estimates. The parent soil, possibly via interactions with its mineral surfaces, also had effects on the degradation of the chemicals, since soil microbial biomass and physiological activity were not correlated with any of the mineralization kinetic parameter estimates. These experiments demonstrate that the environmental form of a chemical has a significant influence on its eventual microbial metabolism and is an important parameter to consider when investigating the fate of chemicals in soil environments.

Effects and Risk Assessment of Linear Alkylbenzene Sulfonates in Agricultural Soil. 4. The Influence of Salt Speciation, Soil Type, and Sewage Sludge on Toxicity Using the Collembolan Folsomia Fimetaria and the Earthworm Aporrectodea Caliginosa as Test Organisms

“…A priori, we hypothesized that toxicity would vary with the texture and the organic matter of the soils, resulting in higher toxicity with a lower CEC value. Sorption to organic carbon is assumed to be the main mechanism controlling bioavailability [15,31]. Because the organic carbon content is similar and quite low in typical Danish agricultural soils, one would not expect much difference in the three soils tested, which was confirmed by the results.…”

“…Also, soil characteristics such as organic matter content, clay content, cation-exchange capacity (CEC), and pH are likely to influence the adsorption and, thus, the toxicity of LAS [14,15]. In the wastewater treatment plant, LAS will presumably be adsorbed to sludge particles, with the adsorption forces being positively correlated with residence time of the LAS-sludge mixture under anaerobic conditions.…”

“…In the wastewater treatment plant, LAS will presumably be adsorbed to sludge particles, with the adsorption forces being positively correlated with residence time of the LAS-sludge mixture under anaerobic conditions. On the one hand, application of sewage sludge to soils could result in a lower bioavailability than when Na-LAS is mixed directly into soil [15]. On the other hand, soil animals may feed selectively on sludge particles [16,17] and, therefore, be at risk via the dietary uptake of LAS.…”

Spiking hydrophobic organic compounds into soil and sediment: A review and critique of adopted procedures

“…Carrier solutions have been added directly to a stirred slurry [43][44][45] or the overlying water of sediment and allowed to sorb with or without mixing [46]. Carrier solutions have also been added directly to wet sediment and allowed to evaporate, leaving a fine crystalline deposit that is subsequently mixed into the sediment [47,48].…”

Effects of sorption on the biodegradation of 2‐methylpyridine in aqueous suspensions of reference clay minerals

“…While it is commonly accepted that sorption to mineral and organic particulate materials reduces the biodegradation of OCs, presumably by lowering the aqueous-phase concentration of contaminants [1][2][3][4][5], this generalization is not universally true. Several studies have suggested that sorbed substrates may also be degraded [6][7][8][9].…”