TY - JOUR

T1 - Transport, retention, and release of Escherichia coli and Rhodococcus erythropolis through dry natural soils as affected by water repellency

AU - Sepehrnia, Nasrollah

AU - Bachmann, Jörg

AU - Hajabbasi, Mohammad Ali

AU - Rezanezhad, Fereidoun

AU - Lichner, Lubomir

AU - Hallett, Paul D.

AU - Coyne, Mark

N1 - Funding Information: This contribution was supported by the Isfahan University of Technology , Iran and the Leibniz University Hannover , Germany. We acknowledge partial financial support of Iran National Science Foundation (INSF, no. 95848929 ) and Alexander von Humboldt Foundation .

PY - 2019/12/1

Y1 - 2019/12/1

N2 - Microbial transport in soil affects pathogen retention, colonization, and innoculant delivery in bioremediating agricultural soils. Various bacteria strains residing in the fluid phases of soils are potential contaminants affecting human health. We measured the transport of hydrophilic Escherichia coli (E. coli) and hydrophobic Rhodococcus erythropolis (R. erythropolis) bacteria through initially air-dried wettable or water-repellent soil columns to understand the effect of water repellency and the hydrophobicity of the organism on its retention, release, and transport properties. Bacteria suspensions infiltrated the top of the columns under saturated (0 cm) and unsaturated (−5 cm) flows in the air-dried (pulse 1) and rewetting (pulse 2) conditions. Cells were recovered from the leachates and the soil extracts by the viable counts. Wettable soil efficiently retained both hydrophobic and hydrophilic bacteria (>80%) in initial air-dried conditions (pulse 1). Even after rewetting, and the formation and expansion of water films and corresponding reduction of the air-water interfacial area (pulse 2), few bacteria were released (maximum 31.5% and 10.1% for saturated and unsaturated flows, respectively), whereas more cells were released from the water-repellent counterpart (more that 72%). The smaller size of hydrophobic R. erythropolis made cell transport possible within the thinner water films of both soils compared to hydrophilic E. coli through pulses 1 and 2. The shape of each strain's retention profiles was uniform and exponential as influenced by soil, strain, and water flow conditions. The results suggest that hydrophobic bacteria will disperse readily when leached into initially dry soil, while hydrophilic bacteria are more susceptible to leaching, posing a risk of pathogen contamination. Clearly the wettability of soil and organisms affects fate and transport.

AB - Microbial transport in soil affects pathogen retention, colonization, and innoculant delivery in bioremediating agricultural soils. Various bacteria strains residing in the fluid phases of soils are potential contaminants affecting human health. We measured the transport of hydrophilic Escherichia coli (E. coli) and hydrophobic Rhodococcus erythropolis (R. erythropolis) bacteria through initially air-dried wettable or water-repellent soil columns to understand the effect of water repellency and the hydrophobicity of the organism on its retention, release, and transport properties. Bacteria suspensions infiltrated the top of the columns under saturated (0 cm) and unsaturated (−5 cm) flows in the air-dried (pulse 1) and rewetting (pulse 2) conditions. Cells were recovered from the leachates and the soil extracts by the viable counts. Wettable soil efficiently retained both hydrophobic and hydrophilic bacteria (>80%) in initial air-dried conditions (pulse 1). Even after rewetting, and the formation and expansion of water films and corresponding reduction of the air-water interfacial area (pulse 2), few bacteria were released (maximum 31.5% and 10.1% for saturated and unsaturated flows, respectively), whereas more cells were released from the water-repellent counterpart (more that 72%). The smaller size of hydrophobic R. erythropolis made cell transport possible within the thinner water films of both soils compared to hydrophilic E. coli through pulses 1 and 2. The shape of each strain's retention profiles was uniform and exponential as influenced by soil, strain, and water flow conditions. The results suggest that hydrophobic bacteria will disperse readily when leached into initially dry soil, while hydrophilic bacteria are more susceptible to leaching, posing a risk of pathogen contamination. Clearly the wettability of soil and organisms affects fate and transport.

KW - Bacteria transport

KW - Infiltration

KW - Microbial retention

KW - Soil contamination

KW - Water repellency

UR - http://www.scopus.com/inward/record.url?scp=85070101296&partnerID=8YFLogxK

U2 - 10.1016/j.scitotenv.2019.133666

DO - 10.1016/j.scitotenv.2019.133666

M3 - Article

C2 - 31394325

AN - SCOPUS:85070101296

VL - 694

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 133666

ER -