Use of Time Domain Reflectometry (TDR) to determine moisture and temperature regimes in Antarctic soils
Wall, A. M. (2004). Use of Time Domain Reflectometry (TDR)to determine moisture and temperature regimes in Antarctic soils (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/12858
Permanent Research Commons link: https://hdl.handle.net/10289/12858
Antarctic soil moisture and temperature data are important as the soil climate influence. Antarctic ecosystems, and the data may provide information on climate change, and the effects of human activities on the Antarctic environment. The objectives of this study were to: (1) determine the limitations of Hydra (TDR) soil moisture probes (Stevens Water Monitoring Systems Inc., Oregon, U.S.A.) for use in Antarctic conditions and in hydrocarbon-contaminated soils; (2) describe the soil moisture and temperature regimes of soils located at Scott Base, Marble Point and in the Wright Valley using existing TDR data; and (3) investigate the temperature and moisture regimes at hydrocarbon-contaminated sites at Scott Base and Marble Point. Determination of the limitations of Hydra (TDR) probes in Antarctic conditions was undertaken in the laboratory where experiments were undertaken to measure the effects of soil temperature, texture, salinity and hydrocarbons on TDR probe accuracy. Field investigations measured soil moisture content with the Hydra (TDR) probes and compared the results to gravimetrically determined soil moisture contents. Soil moisture and temperature data collected by soil climate stations at Scott Base, Marble Point and in the Wright Valley between 1999/2000 and 2001/02 summers, and in hydrocarbon-contaminated soils at Scott Base and Marble Point for the 1999/2000 and 2000/01 summers, were investigated. The laboratory experimentation showed that soil temperature, texture, and salinity all influenced the soil moisture results recorded by the Hydra (TDR) probes. Hydrocarbons did not influence the soil moisture content recorded by the Hydra (TDR) probes. The cumulative and offsetting effects of soil texture, temperature and salinity were considered to be within the ±3% limit of accuracy of the Hydra (TDR) probe stated by the manufacturers. Diurnal freeze-thaw cycles occurred throughout the summer at the 2-5 cm depth, and averaged 50 freeze-thaw cycles per summer at Scott Base, 79 in the Wright Valley, and 52 at Marble Point. At the 2 cm depth, the soil temperature was cumulatively >0°C for an average of 830 hours each summer at Scott Base, 1 680 hours in the Wright Valley, and I 110 hours at Marble Point. Up to five soil-moistening events were identified each summer at Scott Base and Marble Point, while soil-moistening was detected once by one sensor over three summers in the Wright Valley. During the soil-moistening events, volumetric liquid soil moisture contents increased up to 23% at Scott Base, 32% at Marble Point, and 6% in the Wright Valley. At the 2 cm depth, the liquid soil moisture was cumulatively >5% for an average of 860 hours each summer at Scott Base, 1 hour in the Wright Valley, and 310 hours at Marble Point. The drying period following soil-moistening for surface soils (2-5 cm depth) was about 6 days, which was extended to about 12 days when freeze-thaw cycles were occurring. Soil moisture regimes of the hydrocarbon-contaminated soils were similar to those of the uncontaminated soils. Lack of replication, TDR ϴᵥ accuracy, and spatial variability were limitations to the accurate comparison of hydrocarbon-contaminated soil data with that from neighbouring uncontaminated sites.
The University of Waikato
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