Analysis of matrix effects critical to microbial transport in organic waste‐affected soils across laboratory and field scales

Abstract

Organic waste applications to soil (manure, various wastewaters, and biosolids) are among the most significant sources of bacterial contamination in surface and groundwater. Transport of bacteria through the vadose zone depends on flow path geometry and stability and is mitigated by interaction between soil, soil solution, air‐water interfaces, and characteristics of microbial surfaces. After initial entry, the transport through soil depends on continued entrainment of bacteria and resuspension of those retained in the porous structure. We evaluated the retention of bacteria‐sized artificial microspheres, varying in diameter and surface charge and applied in different suspending solutions, by a range of sieved soils contained in minicolumns, the transport of hydrophobic bacteria‐sized microspheres through undisturbed soil columns as affected by waste type under simulated rainfall, and the field‐scale transport of Enterococcus spp. to an unconfined sandy aquifer after the application of liquid manure. Microsphere retention reflected microsphere properties. The soil type and suspending solution affected retention of hydrophilic but not hydrophobic particles. Retention was not necessarily facilitated by manure‐microsphere‐soil interactions but by manure‐soil interactions. Undisturbed column studies confirmed the governing role of waste type on vadose‐zone microsphere transport. Filtration theory applied as an integrated analysis of transport across length scales showed that effective collision efficiency depended on the distance of travel. It followed a power law behavior with the power coefficient varying from ∼0.4 over short distances to >0.9 over 1 m (i.e., very little filtration for a finite fraction of biocolloids), consistent with reduced influence of soil solution and biocolloid properties at longer travel distances.

Assessing biosynthetic potential of agricultural groundwater through metagenomic sequencing: A diverse anammox community dominates nitrate-rich groundwater

“…Each water sample was tested for the presence of USDA pathogenic bacteria by inoculating liquid enrichment media and plating on selective nutrient media [20–22]. The specific pathogens tested for were Salmonella , Enterococcus , Escherichia coli , and E .…”

Soil and Waste Matrix Affects Spatial Heterogeneity of Bacteria Filtration during Unsaturated Flow

“…Previous observations have shown that filtration efficiency decreases with distance [15,17]. Nevertheless, for the sandy soils, which were less heterogeneous, this phenomenon was less obvious and for the application of LMB the fit was mostly linear, indicating continual decrease in cumulative filtration for collectors that allowed increased flow and suggesting a more constant filtration and thus advection of bacteria at consistent rates independent of the total flow.…”

“…If this were the case then transport would be mainly a function of particle size relative to the pores [17]. Effective size of bacteria tends to vary with their physiological status [31].…”

“…Retention, as described by collision efficiency, was shown to vary consistently across distances and experimental conditions [17]. We need to understand the role of waste type on transport pathway stability and retention and re-entrainment of bacteria to be able to understand and manage long-term risks associated with transport of pathogenic bacteria through soil.…”

Effects of dissolved organic matter on the co-transport of mineral colloids and sorptive contaminants

“…The transport of contaminants through the vadose zone has important implications to groundwater quality and has received considerable attention (e.g., Chen et al, 2005;Dresel et al, 2011;Lazouskaya et al, 2011Lazouskaya et al, , 2013Masciopinto and Caputo, 2011;Oostrom et al, 2010;Unc et al, 2012). Dissolved contaminants are transported through vadose zone to groundwater by advection and dispersion, and the transport process can be retarded due to contaminant adsorption to the porous medium (Gidley et al, 2012;Rod et al, 2010;Roy and Dzombak, 1997;Simunek et al, 2006).…”