TY - JOUR

T1 - Aggregate stability of south Chilean volcanic ash soils

T2 - A combined XPS, contact angle, and surface charge analysis

AU - Bachmann, J.

AU - Goebel, M. O.

AU - Krueger, J.

AU - Fleige, H.

AU - Woche, S. K.

AU - Dörner, J.

AU - Horn, R.

N1 - Funding Information: Financial support provided by the German Research Foundation – DFG (BA 1359/12-1 and HO 911/45-1) for this project is greatly appreciated. We would like to thank Patrick Neumann (Kiel) for soil sampling and determining basic soil properties, Stephan Sass (Hannover) for soil sampling, Hendrik Brüggemeyer (Hannover) for measuring aggregate stability as well as Hanna Böhme and Cora Bell (Hannover) for conducting textural analysis

PY - 2020/3/1

Y1 - 2020/3/1

N2 - Soils developed from volcanic ash deposits vary extremely in physical and chemical soil properties and are known to degrade easily through erosion or soil compaction, which limits intensive utilization. Our objective was to test if aggregate stability, AS, as a key factor for erodibility, can be assessed from surface parameters, namely particle wettability in terms of the solid–water contact angle, CA, and the specific surface charge, SSC. To relate wettability to the chemical composition of particle interfaces, the amount of polar and nonpolar carbon (C) species within the particle interface layer was assessed by X-ray photoelectron spectroscopy, XPS. Samples were taken from four locations in southern Chile (40° south) along a 120 km transect from the central volcano range to the coastal mountain region. Sites were different in stage of soil development and land use. Aggregates (8–12 mm) were sampled on forest, meadow or arable plots from upper top- and subsoil. To increase the natural range of SSC and CA, soil pH was modified by treatment with HCl and NH3 gas, respectively. Results showed a general trend of increasing AS with increasing soil development, i.e. decreasing bulk density and increasing clay and soil organic carbon, SOC, content. A clear relation was also found between CA and AS with a wide range of AS (about 9 to >90%) at CA < 35° and always high AS for CA > 35°. XPS analysis showed that CA was closely related to the amount of nonpolar C species. Interestingly, the relation between CA and AS was still consistent after pH variation (initial pH ≅ 6, modified to pH 2 to 9) which led to net changes in SSC from around 0 C g−1 (pH 6) to values between +10 and −8 C g−1, respectively. CA for negative SSC were still in the range from 0° to >90°, similar to untreated soil, whereas positive SSC reduced the maximum CA to <40°. Increasing or decreasing SSC caused higher AS, while the least stable aggregates were found at point of zero charge, PZC. XPS analysis showed that a relative increase in interfacial C content increased AS (r2 = 0.77) and CA (r2 = 0.98) significantly. Generally, CA was revealed to be a significant parameter that allows rapid assessment of the present status and possible modifications of AS for a wide range of environmental conditions.

AB - Soils developed from volcanic ash deposits vary extremely in physical and chemical soil properties and are known to degrade easily through erosion or soil compaction, which limits intensive utilization. Our objective was to test if aggregate stability, AS, as a key factor for erodibility, can be assessed from surface parameters, namely particle wettability in terms of the solid–water contact angle, CA, and the specific surface charge, SSC. To relate wettability to the chemical composition of particle interfaces, the amount of polar and nonpolar carbon (C) species within the particle interface layer was assessed by X-ray photoelectron spectroscopy, XPS. Samples were taken from four locations in southern Chile (40° south) along a 120 km transect from the central volcano range to the coastal mountain region. Sites were different in stage of soil development and land use. Aggregates (8–12 mm) were sampled on forest, meadow or arable plots from upper top- and subsoil. To increase the natural range of SSC and CA, soil pH was modified by treatment with HCl and NH3 gas, respectively. Results showed a general trend of increasing AS with increasing soil development, i.e. decreasing bulk density and increasing clay and soil organic carbon, SOC, content. A clear relation was also found between CA and AS with a wide range of AS (about 9 to >90%) at CA < 35° and always high AS for CA > 35°. XPS analysis showed that CA was closely related to the amount of nonpolar C species. Interestingly, the relation between CA and AS was still consistent after pH variation (initial pH ≅ 6, modified to pH 2 to 9) which led to net changes in SSC from around 0 C g−1 (pH 6) to values between +10 and −8 C g−1, respectively. CA for negative SSC were still in the range from 0° to >90°, similar to untreated soil, whereas positive SSC reduced the maximum CA to <40°. Increasing or decreasing SSC caused higher AS, while the least stable aggregates were found at point of zero charge, PZC. XPS analysis showed that a relative increase in interfacial C content increased AS (r2 = 0.77) and CA (r2 = 0.98) significantly. Generally, CA was revealed to be a significant parameter that allows rapid assessment of the present status and possible modifications of AS for a wide range of environmental conditions.

KW - Andosols

KW - Contact angle

KW - Specific surface charge

KW - Wet-sieving aggregate stability

KW - X-ray photoelectron spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=85075988733&partnerID=8YFLogxK

U2 - 10.1016/j.geoderma.2019.114022

DO - 10.1016/j.geoderma.2019.114022

M3 - Article

AN - SCOPUS:85075988733

VL - 361

JO - GEODERMA

JF - GEODERMA

SN - 0016-7061

M1 - 114022

ER -