Extraction of compounds associated with water repellency in sandy soils of different origin

After an initial evaluation of several solvents, the efficiency of Soxhlet extractions with isopropanol/ammonia (s.g. 0.88) (70 : 30 v : v; 24 h) in extracting compounds associated with water repellency in sandy soils was examined using a range of repellent and wettable control soils (n = 15 and 4) from Australia, Greece, Portugal, The Netherlands, and the UK. Extraction efficiency and the role of the extracts in causing soil water repellency was examined by determining extract mass, sample organic carbon content and water repellency (after drying at 20°C and 105°C) pre- and post-extraction, and amounts of aliphatic C–H removed using DRIFT, and by assessing the ability of extracts to cause repellency in acid-washed sand (AWS). Key findings are: (i) none of organic carbon content, amount of aliphatic C–H, or amount of material extracted give any significant correlation with repellency for this diverse range of soils; (ii) sample drying at 105°C is not necessarily useful before extraction, but may provide additional information on extraction effectiveness when used after extraction; (iii) the extraction removed repellency completely from 13 of the 15 repellent samples; (iv) extracts from all repellent and wettable control soils were capable of inducing repellency in AWS. The findings suggest that compounds responsible for repellency represent only a fraction of the extract composition and that their presence does not necessarily always cause repellency.

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The Impacts of Vineyard Afforestation on Soil Properties, Water Repellency and Near-Saturated Infiltration in the Little Carpathians Mountains

Water ◽

10.3390/w12092550 ◽

2020 ◽

Vol 12 (9) ◽

pp. 2550

Author(s):

Andrej Hrabovský ◽

Pavel Dlapa ◽

Artemi Cerdà ◽

Jozef Kollár

Keyword(s):

Land Use ◽

Organic Carbon ◽

Soil Properties ◽

Carbon Content ◽

Water Repellency ◽

Infiltration Rate ◽

Organic Carbon Content ◽

Soil Water Repellency ◽

Infiltration Process ◽

Vineyard Soils

Vineyards are a 7000-year-old land-use tradition and both management and abandonment have result in altered soil properties. These have a great effect on water resources and soil services, and this inspired our investigation into the effects of land-use and land-use change on soils in the Modra wine-growing region in South-western Slovakia. Ten topsoil samples were taken at each of the seven research sites (n = 70) on granite parent material in cultivated and afforested vineyards and original forest soils. Laboratory analyses included determination of soil texture, organic carbon content, soil pH, and water repellency. This was supplemented by infiltration measurements under near-saturated conditions at the vineyard and afforested study sites. Studied soils have a low clay content and a high proportion of sand. The vineyard soils have significantly higher pH than the forest and afforested soils because the naturally acidic soils have been limed. The forest and afforested soils have similar properties, with higher organic carbon content. This makes them strongly to extremely water repellent and contrasts sharply with the wettability of cultivated vineyard soils. One afforested site, however, was less acidic and therefore was considered transitional between forest and vineyard soils. Our infiltration measurements established the influence of soil water repellency on the infiltration process, and our results highlighted that the infiltration rate in the vineyard soils was significantly higher than in afforested soils. The infiltration rate also gradually increased over time in afforested soils due to decreasing water repellency. Physically impossible negative sorptivity values in afforested soils were noted because of changes in water repellency during the infiltration process. Finally, we conclude that soil afforestation results in increased soil water repellency and a subsequent reduction in the infiltration rate at the matrix scale.

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Drivers of soil water repellency after wildfires: case study in the south-central Appalachian Mountains, US

10.5194/egusphere-egu21-3738 ◽

2021 ◽

Author(s):

Jingjing Chen ◽

Brian Strahm ◽

Ryan Stewart

Keyword(s):

Organic Carbon ◽

Carbon Content ◽

Soil Water ◽

Functional Groups ◽

Appalachian Mountains ◽

Water Repellency ◽

Organic Carbon Content ◽

Soil Water Repellency ◽

South Central ◽

Mount Pleasant

Increasing frequency of wildfire in humid hardwood forests make it necessary to understand the occurrence and origin of soil water repellency in these systems, as wildfire-induced soil water repellency has been observed to severely impact many biophysical processes in other forest types. In this project, we studied two sites in the Appalachian Mountains, United States, (at Mount Pleasant Wildlife Refuge, Virginia, and Chimney Rock State Park, North Carolina) where wildfires occurred in late 2016. In each site, burned and unburned soils were evaluated for actual (in the field) and potential (in the laboratory) water repellency using the water drop penetration time method. In addition, samples were analyzed for organic carbon content (measured using C/N analyzer), hydrophobic functional groups (using Fourier transform infrared, FTIR), and their rank correlations (rs) based on multiple samples collected one year after the fires. We found that soil water repellency was substantial greater in burned soils in the first months after the fire, and persisted for the entire year in the more severely burned soils. We also determined that potential water repellency was much greater than actual water repellency, and that organic carbon content and hydrophobic functional groups were significantly correlated to potential water repellency (p < 0.0001). Correlations were stronger at Mount Pleasant (0.77 < rs <0.91) than at Chimney Rock (0.06 < rs < 0.70). For actual water repellency only had significant correlations with soil organic content at Mount Pleasant (p < 0.0001), and with hydrophobic functional groups (p < 0.0001) at both sites except the unburned soils at Chimney Rock. However, these correlations were weaker than with potential water repellency, likely due to the influence of soil water content. Altogether, this study provides new insight into the influence of soil organic matter and its composition on post-wildfire soil water repellency.

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Organic carbon content controls the severity of water repellency and the critical moisture level across New Zealand pasture soils

Geoderma ◽

10.1016/j.geoderma.2018.12.007 ◽

2019 ◽

Vol 338 ◽

pp. 281-290 ◽

Cited By ~ 9

Author(s):

Cecilie Hermansen ◽

Per Moldrup ◽

Karin Müller ◽

Peter Weber Jensen ◽

Carlo van den Dijssel ◽

...

Keyword(s):

New Zealand ◽

Organic Carbon ◽

Carbon Content ◽

Water Repellency ◽

Moisture Level ◽

Organic Carbon Content ◽

Critical Moisture

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Differences in sorption behaviour of carbaryl and phosalone in soils from Australia, Pakistan, and the United Kingdom

Soil Research ◽

10.1071/sr00021 ◽

2001 ◽

Vol 39 (4) ◽

pp. 893 ◽

Cited By ~ 18

Author(s):

R. Ahmad ◽

R. S. Kookana ◽

A. M. Alston ◽

R. H. Bromilow

Keyword(s):

United Kingdom ◽

Organic Carbon ◽

Carbon Content ◽

Organic Carbon Content ◽

Local Conditions ◽

Sorption Behaviour ◽

Organic C ◽

The United Kingdom ◽

D Values ◽

The Uk

Sorption of 2 nonionic pesticides, carbaryl (1-naphthyl methylcarbamate) and phosalone (S-6-chloro-2,3-dihydro-2-oxobenzoxazol-3-ylmethyl O,O-diethyl phosphorodithioate), was investigated for 48 soils from Australia, Pakistan, and the United Kingdom. A wide variation in sorption affinities of the soils to carbaryl and phosalone was observed. The sorption coefficient (K d) values for carbaryl ranged from 0.19 to 23.0 L/kg in Australian soils, from 0.99 to 59.7 L/kg in Pakistani soils, and from 1.09 to 23.0 L/kg in the UK soils. The K d values for phosalone ranged from 4.8 to 443 L/kg in Australian soils, from 15.5 to 1182 L/kg in Pakistani soils, and from 18.1 to 205 L/kg in the UK soils. To eliminate the effect of variation in organic carbon content among the soils, the K d values were normalised to the fraction of soil organic carbon (K oc ). However, K oc values for both pesticides varied by about an order of magnitude across the soils, decreasing in the following order: Pakistani > Australian > UK soils. Correlation between K d and organic carbon content of the soils was poor (r 2 = 0.44 and 0.46). The particulate organic C (53 µm–2 mm) was only slightly better correlated with K d than the total organic C in the <2 mm fraction of the soils. Thus soil organic C content alone is not a good predictor of sorption even for nonionic pesticides such as carbaryl and phosalone. Caution is needed during extrapolation of overseas data to predict sorption under local conditions.

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