Alterations in aggregate characteristics of thermally heated water-repellent soil aggregates under laboratory conditions

TY - JOUR

T1 - Alterations in aggregate characteristics of thermally heated water-repellent soil aggregates under laboratory conditions

AU - Perera, H. T.M.

AU - Leelamanie, D. A.L.

AU - Maeda, Morihiro

AU - Mori, Yasushi

N1 - Publisher Copyright: © 2023 H. T. M. Perera et al., published by Sciendo.

PY - 2023/6/1

Y1 - 2023/6/1

N2 - The heat generated during wildfires modifies soil characteristics, including soil water repellency (SWR) and the water stability of aggregates, which are known to be interrelated. SWR lowers the rate of water entry into aggregates, minimizing aggregate disruption and subsequent erosion. This study aimed to examine these aggregate characteristics (SWR, water stability of aggregates) of thermally heated water-repellent soil aggregates under laboratory conditions. Water-repellent aggregates were collected from Eucalyptus grandis forest soil separately from four soil depths (0-5, 5-10, 10-15, and 15-20 cm) with varying initial repellency levels. Using an automated programmable muffle furnace, aggregates were separately exposed to three heating temperatures, TH (150, 200, 250 °C), three rates of heating (speed of rising temperature to reach relevant TH), RH (200, 400, 800 °C h-1), and three durations of exposure to relevant TH, ED (30, 60, 120 min). The molarity of an ethanol droplet test was used to measure the contact angle (contact angle>90°). The water drop penetration time (WDPT) was also measured. The SWR of aggregates declined with the increasing TH and ED. All aggregates were wettable once exposed to 250 °C. At the lowest TH and ED (150 °C, 30 min), the contact angle was <90° only in the least repellent aggregates collected from 10-15 and 15-20 cm depths. Although RH indicated the least influence on the measured parameters, the slowest RH (200 °C h-1) caused a comparatively greater decline in SWR. Water stability of aggregates increased with heating irrespective of decreasing SWR. Further investigations on heat-induced changes in organic compounds at molecular levels would be necessary to understand the theories for the behavior of aggregates.

AB - The heat generated during wildfires modifies soil characteristics, including soil water repellency (SWR) and the water stability of aggregates, which are known to be interrelated. SWR lowers the rate of water entry into aggregates, minimizing aggregate disruption and subsequent erosion. This study aimed to examine these aggregate characteristics (SWR, water stability of aggregates) of thermally heated water-repellent soil aggregates under laboratory conditions. Water-repellent aggregates were collected from Eucalyptus grandis forest soil separately from four soil depths (0-5, 5-10, 10-15, and 15-20 cm) with varying initial repellency levels. Using an automated programmable muffle furnace, aggregates were separately exposed to three heating temperatures, TH (150, 200, 250 °C), three rates of heating (speed of rising temperature to reach relevant TH), RH (200, 400, 800 °C h-1), and three durations of exposure to relevant TH, ED (30, 60, 120 min). The molarity of an ethanol droplet test was used to measure the contact angle (contact angle>90°). The water drop penetration time (WDPT) was also measured. The SWR of aggregates declined with the increasing TH and ED. All aggregates were wettable once exposed to 250 °C. At the lowest TH and ED (150 °C, 30 min), the contact angle was <90° only in the least repellent aggregates collected from 10-15 and 15-20 cm depths. Although RH indicated the least influence on the measured parameters, the slowest RH (200 °C h-1) caused a comparatively greater decline in SWR. Water stability of aggregates increased with heating irrespective of decreasing SWR. Further investigations on heat-induced changes in organic compounds at molecular levels would be necessary to understand the theories for the behavior of aggregates.

KW - Eucalyptus grandis

KW - Laboratory heating

KW - Water repellency

KW - Water stability of aggregates

UR - http://www.scopus.com/inward/record.url?scp=85159860837&partnerID=8YFLogxK

U2 - 10.2478/johh-2023-0009

DO - 10.2478/johh-2023-0009

M3 - Journal article

AN - SCOPUS:85159860837

SN - 0042-790X

VL - 71

SP - 177

EP - 187

JO - Journal of Hydrology and Hydromechanics

JF - Journal of Hydrology and Hydromechanics

IS - 2

ER -