Connecting bacterial colonization to physical and biochemical changes in a sand box infiltration experiment

Influence of Increasing Concentrations of Organic Pollutants on Biofilm Formation and Flow Parameters in a Sand-aquifer and Its Capillary Fringe.

“…At both probe positions the mean temperatures in phases III and IV, when most substrate was available and metabolized by P. fluorescens in the sand of the SSC were significantly higher than in phase I, II and V, when less soluble organic material was supplied in the medium for respiration. An increased temperature in a sand box experiment of 0.5 -1 °C during respiration of pollutants was also observed by [45]. In the SSC experiment the temperature changes resulted from bacterial heat production during respiration and presumably decreasing heat losses by a decreasing evaporation during accumulation of EPS.…”

“…Single aspects of biofilm formation have been reviewed previously by [43], covering among others the changes of the "morphological structure of the extracellular polymeric substances (EPS) matrix under varying hydration states, its role in maintenance of aquatic microhabitats and facilitating nutrient diffusion under desiccated conditions, and potential modification of macroscopic hydrologic properties of host porous media". Biofilm formation by a mixed population of soil bacteria and flow characteristics during vertical infiltration of slightly polluted water in the low mg/L-range, into a water-saturated soil of 1.2 m depth in a lysimeter was investigated by [45]. Microbial processes in the heterogeneous soil of the lysimeter apparently reduced the infiltration rate.…”

“…Whereas mainly aerobic bacteria, fungi and protozoa colonize soil surface layers, the proportion of mainly anaerobic bacteria (most of them are "fermenters") and of Actinomycetes increases with depth in the underground in the vicinity and below the groundwater table. These population changes are accompanied by a significantly decreasing diversity of microorganisms [17] and by a decrease of physiological functions [45]. Groundwater bacteria tend to form a biofilm on mineral surfaces of soil particles and may cause preferential flow paths or clogging in heterogeneous soil compartments [45].…”

“…These population changes are accompanied by a significantly decreasing diversity of microorganisms [17] and by a decrease of physiological functions [45]. Groundwater bacteria tend to form a biofilm on mineral surfaces of soil particles and may cause preferential flow paths or clogging in heterogeneous soil compartments [45]. In contrast aerobic motile bacteria can even move into the top zone of the capillary fringe (CF, spanning from the groundwater table to still visible moisture above it in a quartz sand aquifer) above the water-saturated zone of quartz sand and form a dense biofilm in the still highly saturated interface region of the CF [31].…”

A random walk solution for modeling solute transport with network reactions and multi-rate mass transfer in heterogeneous systems: Impact of biofilms

“…Because bacteria generally have diameters that range between 0.1 and 1 microns, the small effective porosity of clays typically restricts the ability of bacteria to move and reproduce effectively. Also, the natural occurrence of preferential flow channels in porous media (typically represented as a mobile region in the multirate model) favors the movement of groundwater and dissolved elements through certain pathways, which typically harbor larger bacterial densities and microbial activities compare to the adjacent porous media (Pivetz and Steenhuis, 1995;Mallawatantri et al, 1996;Rubol et al, 2014). In fact, Vinther et al (1999) and Bundt et al (2001) found that both substrate availability and nutrient supply are largest in preferential flow paths, enhancing bacterial biomass and associated microbial processes.…”