Soil/Air Partitioning of Semivolatile Organic Compounds. 2. Influence of Temperature and Relative Humidity

Abstract

The influence of temperature and relative humidity (RH) on the equilibrium partitioning of polychlorinated biphenyls (PCBs), pentachlorobenzene, and hexachlorobenzene between a sandy loam soil and air was investigated. The measurements were conducted at 6 temperatures from 5 to 60 °C at each of 5 different relative humidities from 29 to 93% in a solid-phase fugacity meter. The soil/air equilibrium partition coefficient (K SA) was very sensitive to temperature and humidity. For instance, K SA for PCB 52 was 46,000 times higher at T = 5 °C, RH = 29% than at T = 60 °C, RH = 93%. For a given RH, a linear relationship between ln K SA and 1/T was observed. The heats of phase change were similar for the di- through octachlorinated PCB congeners but varied with RH, increasing from 103 kJ/mol at RH = 29% to 116 kJ/mol at RH = 66% and then decreasing to 98 kJ/mol at RH = 93%. At a given temperature, an inverse linear relationship between ln K SA and RH was observed. The slopes of these lines were similar for all compounds studied at all temperatures. The increase in K SA with diminishing RH was much greater than could be explained by adsorption to soil minerals. This suggests that sorption in organic material also increases with diminishing RH. A simple predictive equation was developed to calculate K SA as a function of soil properties, physical chemical properties, soil temperature and soil relative humidity. The correlation coefficient for the 1131 data points predicted and the measured K SA was 0.97, with a root-mean-square residual of 0.24 log units. This equation provides an initial basis for exploring the influence of the high sensitivity of K SA to temperature and relative humidity on the environmental fate of SOCs.

Polychlorinated biphenyls (PCBs) in air and soil from a high-altitude pasture in the Italian Alps: evidence of CB-209 contamination

“…The temperature-dependent interpretation of the seasonal trend of the PCB concentrations in soil agrees with that of Hippelein and McLachlan (2000) and Ballabio et al (2013) and can be verified by comparing the PCB concentrations in soil and their temperature-specific K sa values. Including the effect of temperature in the equation suggested by Hippelein and McLachlan (1998), we can obtain specific K sa values for each congener on each sampling date.…”

The influence of land use on the concentration and vertical distribution of PBDEs in soils of an e-waste recycling region of South China

“…Second, PBDEs can be transported to nearby surface waters through mechanical and soil-solution runoff with surface soils. And finally, vaporization rates are greater in moist paddy soils due to the co-evaporation of more volatile PBDEs with water (Hippelein and McLachlan, 2000). Since the volatility of BDE-209 is very low, the low levels of BDE-209 in the topsoil of paddy fields can mostly be attributed to the adsorption to particles associated with leaching or runoff.…”

Critical evaluation of a new passive exchange-meter for assessing multimedia fate of persistent organic pollutants at the air-soil interface

“…Other active sampling approaches have been tested to assess the biogeochemical control on POP re-emission from soils, mainly aimed at measuring airsurface fugacity gradients (Cabrerizo et al, 2009(Cabrerizo et al, , 2011aHippelein and McLachlan, 2000). These approaches lacked capacity of resolving mass transfer and fluxes.…”