Effects of relative humidity on the water repellency of fire-affected soils
Effects of relative humidity on the water repellency of fire-affected soils
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DOI：
10.1016/j.catena.2015.11.012
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发表时间：
2016-03-01
期刊：
影响因子：
6.2
通讯作者：
Arcenegui, V.
中科院分区：
文献类型：
--
作者：
Jimenez-Pinilla, P.;Doerr, S. H.;Arcenegui, V.
土壤拒水性（SWR）是未燃烧的土壤，特别是受火灾影响的土壤中的一个常见特征，并且可以增加几种环境风险。它可能受到许多因素的影响，如植被覆盖、含水量，以及在受火灾影响的地区，燃烧时的升温程度。此外，使用未燃烧土壤的实验表明，大气相对湿度会影响其防水性。本实验室研究的目的是研究环境相对湿度（RH）如何影响燃烧土壤的SWR，并探讨其对火灾影响地区的影响。土壤样品取自易着火但长期未燃烧的松和阿利坎特（西班牙东南部）戈尔加的灌木丛。为了模拟不同的火灾严重程度，将样品在不同温度（50、100、150、200、250、300和350 ° C）下加热20分钟。然后将样品在20 ℃恒温的密封气候室中在不同RH（30、50、70和95%）下平衡。在密封气候室内进行水滴渗透时间（WDPT）测试、乙醇液滴摩尔浓度（MED）测试和前进接触角（CA）测量，以评估每个样品和处理的SWR。总的来说，增加热处理增强了SWR，这反过来在暴露于高RH后进一步增强。WDPT试验表明，松树下的土壤在最低加热温度下是斥水的，在较高的加热温度和接近饱和（95%RH）时变得强烈斥水。灌木林地土壤大多是湿的，在发病时，并保持在每一个RH水平的研究，除了轻微的SWR在95%RH。MED和CA测量后发现类似的趋势。结果表明，高相对湿度有助于提高驻波比也在烧过的土壤，高温已经导致了显着提高驻波比。这些研究结果表明，在现场或实验室条件下确定的火灾影响地区周围的SWR水平可能会低估在高相对湿度水平，往往在大风暴事件之前存在的表观SWR水平。这反过来又对预测火灾后径流和侵蚀事件产生影响。(C)2015 Elsevier B.V.版权所有。
Soil water repellency (SWR) is a common feature in unburned and particularly in fire-affected soils, and can enhance several environmental risks. It can be affected by many factors such as vegetation cover, moisture content and, in fire-affected areas, the degree of heating during burning. In addition, experiments using unburned soils have shown that atmospheric relative humidity can affect their water repellency. The purpose of this laboratory study was to examine how ambient relative humidity (RH) affects SWR of burned soils, and to explore its implications for fire-affected regions. Soil samples were taken from under fire-prone, but long unburned Pinus halepensis and a shrub site in Gorga, Alicante (SE Spain). In order to simulate different fire severities, samples were heated for 20 min at different temperatures (50, 100, 150, 200, 250, 300 and 350 degrees C). Samples were then equilibrated at different RHs (30, 50, 70 and 95%) in a sealed climate chamber at a constant temperature of 20 degrees C. The water drop penetration time (WDPT) test, molarity of ethanol droplet (MED) test, and advancing contact angle (CA) measurements were performed inside the sealed climate chamber to assess SWR for each sample and treatment Overall, increasing heat treatments enhanced SWR, which in turn was enhanced further following exposure to high RHs. The WDPT test showed that soils under pine were water repellent at the lowest heating temperature and became strongly water repellent at the higher heating temperatures and near saturation (95% RH). Shrubland soils were mostly wettable at the onset and remained so at every RH level studied except being slightly SWR at 95% RH. A similar trend was found after MED and CA measurements. The results demonstrate that high RH contributes to enhanced SWR also in burned soils, where high temperatures had already led to a substantial enhancement of SWR. These findings suggest that SWR levels determined for fire affected areas ambient under field or laboratory conditions may underestimate the apparent SWR levels present at the high RH levels that often precede major storm events. This in turn has implications for predicting post-fire runoff and erosion events. (C) 2015 Elsevier B.V. All rights reserved.