China
Africa
Explore chapters and articles related to this topic
Contaminant Vapors as a Component of Soil Gas in the Unsaturated Zone
Published in Warren J. Lyman, Patrick J. Reidy, Benjamin Levy, Chi-Yuan Fan, Mobility and Degradation of Organic Contaminants in Subsurface Environments, 2020
Warren J. Lyman, Patrick J. Reidy, Benjamin Levy, Chi-Yuan Fan
Volatilization from liquid contaminant in loci nos. 5, 6, and 7 into the soil air represents the primary mechanism for partitioning into this locus. Concentrations in the soil gas are affected by advection and dispersion, gravity transport, and chemical retardation and sorption. Volatilized contaminant mass in the soil gas may partition to dry soil (locus no. 2) or wet soil (locus no. 4). Contaminant mass may also dissolve into the pore water of the unsaturated zone (loci nos. 3 and 12) or into the water of the saturated zone (locus no. 8). Contaminated soil gas is considered to be relatively mobile and venting to the atmosphere is the chief loss mechanism.
Site Investigations
Published in Benjamin Alter, Environmental Consulting Fundamentals, 2019
Depending on access issues and site geology, a drill rig can install as many as 30 soil gas probes in a day, enabling the rapid collection of subsurface data. Soil gas samples can be analyzed by a fixed-base laboratory, or in the field in a mobile laboratory so that the real-time data can be used to select the next sampling locations. By varying the depth of the soil gas probes, active soil gas surveys can also provide vertical profiling of the concentration of contaminants in the vadose zone.
Field Investigation Techniques for Potentially Contaminated Sites
Published in Kofi Asante-Duah, Management of Contaminated Site Problems, 2019
On the whole, soil gas surveys are well-established methods for assessing the subsurface distribution of volatile organic contamination. They are particularly useful in the vicinity of storage tanks that are suspected to be leaking or in areas where some form of release or spill of fuels or organic solvents is suspected. Classically, soil gas surveys are used to delineate the apparent extent of soil contamination and to identify locations for the collection of samples for more rigorous analysis conducted in an analytical laboratory. They can indeed be a powerful screening technique, if used in a professionally credible and responsible manner. This is because soil gas surveys can delineate source areas and track some contaminant plumes, allowing an investigator to more accurately place subsequent soil boring and monitoring well point locations.
New-designed in-situ measurement system for radon concentration in soil air and its application in vertical profile observation
Published in Journal of Nuclear Science and Technology, 2022
Hao Wang, Lei Zhang, Yunxiang Wang, Changhao Sun, Qiuju Guo
Calibration of 10 radon probes was conducted in a temperature-and-humidity-controlled box with an effective volume of 150 L (KOWINTEST, KW-TH, China) [37]. The relative humidity could be adjusted from 10% to 95% with an uncertainty of 2%, and the temperature control range is from −10 °C to 40 °C with an uncertainty of 0.3 °C. The soil gas pumped from 1 m depth in the soil at a flow rate of 2.5 lpm was used as radon source. The radon concentration in the temperature-and-humidity-controlled box was measured by an AlphaGUARD PQ2000 monitor (Saphymo, France) [38], which can be traced back to the National Radon Standard of Metrological Institute of China.
Study of radon/thoron exhalation rate, soil-gas radon concentration, and assessment of indoor radon/thoron concentration in Siwalik Himalayas of Jammu & Kashmir
Published in Human and Ecological Risk Assessment: An International Journal, 2018
Manpreet Kaur, Ajay Kumar, Rohit Mehra, Rosaline Mishra
The soil-gas radon concentration at different depth intervals (15, 30, 60, and 100 cm) was measured by semiconductor based detector, i.e., RAD7 (Durridge Company, 2012, made in USA), which was composed of a pump with 1-m long steel soil probe and a desiccant (Kaur et al.2017) as shown in Figure 4. The soil-gas samples of each site were collected with the help of the stainless steel probe. Firstly, a pilot iron rod was driven into the soil at depth interval of 15 cm with gentle strokes of hammer.; At 15 cm depth, it was removed and an assembly of stainless steel probe having iron rod within it, was inserted within this hole by gentle hammering up to that specific depth of 1 m. After successfully inserting the iron rod, it was removed and the probe was then connected to RAD7 detector through desiccant tube containing CaSO4. The measurements were performed where the soil is uniform and generally free of rocks. The measuring instrument was then attached to the probe for sucking the soil-gas from the deep soil. The sniff-protocol and grab mode was used for the soil sampling. The radon concentration was calculated according to the counts of 218Po which was collected by an electrode. The measurement cycle was about 30 min. The soil was sucked through the tube pipe into the measuring instrument for 5-min pumping phase. The instrument waits another 5 min and then counts for four 5-min cycles. At the end of the half-hour period, the RAD7 printed out a summary of the measurement, including an average radon concentration in the soil-gas from the four 5-min cycle measurements. The minimum detection limit of the system is 4 Bq m−3. The same procedure was followed for the measurement of soil radon gas concentration at depth intervals of 30 cm, 60 cm, and 100 cm.
Recent progress in radon-based monitoring as seismic and volcanic precursor: A critical review
Published in Critical Reviews in Environmental Science and Technology, 2020
Nury Morales-Simfors, Ramon A. Wyss, Jochen Bundschuh
Radon migration in soil proceeds both by diffusion and by transport with moving soil gas (Tanner, 1971). Its transport through natural soils exhibits a multi-layer behavior, where each layer has its own diffusion coefficient (Hafez & Awad, 2016). Radon concentration in the soil-gas increases with depth (Antonopoulos-Domis, Xanthos, Clouvas, & Alifrangis, 2009; Tanner, 1971) and the diffusion and advection of radon out of soils are controlled by several physical factors that affect the formation and movement of radon through the underground, such as (i) soil structure (the uranium content of soil, soil pore structure, grain size, soil porosity, presence of radon carrier gases, permeability of the host rock, groundwater movement, temperature), (ii) meteorological variables (soil humidity, atmospheric pressure, wind speed, soil thermal gradient), and (iii) geophysical (e.g. faulting and seismicity) and geological characteristics of the area under survey. Radon acts as an indicator for changes in the gas streams, Friedmann (2012) found that the most sensitive depth to detect such changes is between 0.5 to 1 m. Antonopoulos-Domis et al. (2009) found that radon concentration increased up to soil depths of about 80 cm, seems to remain constant at depths of 80-130 cm, and then increased again. The increase in soil-gas radon concentration before an earthquake may be due to the strain build up in the area (Dutta et al., 2012). High radon releases are characterized by structural discontinuities and/or weakness, such as faults and fracture systems, which increase porosity and permeability of the soils and rocks (e.g. Burton, Neri, & Condarelli, 2004; Dutta et al., 2012; Kuo & Tsunomori, 2014; Neri et al., 2016; Nikolopoulos et al., 2012; Richon et al., 2010; Tuccimei et al., 2015; Walia et al., 2005, Walia et al., 2010).