Influence of Temperature, Relative Humidity, and Soil Properties on the Soil–Air Partitioning of Semivolatile Pesticides: Laboratory Measurements and Predictive Models

Abstract

Soil-air partition coefficient (Ksoil-air) values are often employed to investigate the fate of organic contaminants in soils; however, these values have not been measured for many compounds of interest, including semivolatile current-use pesticides. Moreover, predictive equations for estimating Ksoil-air values for pesticides (other than the organochlorine pesticides) have not been robustly developed, due to a lack of measured data. In this work, a solid-phase fugacity meter was used to measure the Ksoil-air values of 22 semivolatile current- and historic-use pesticides and their degradation products. Ksoil-air values were determined for two soils (semiarid and volcanic) under a range of environmentally relevant temperature (10-30 °C) and relative humidity (30-100%) conditions, such that 943 Ksoil-air measurements were made. Measured values were used to derive a predictive equation for pesticide Ksoil-air values based on temperature, relative humidity, soil organic carbon content, and pesticide-specific octanol-air partition coefficients. Pesticide volatilization losses from soil, calculated with the newly derived Ksoil-air predictive equation and a previously described pesticide volatilization model, were compared to previous results and showed that the choice of Ksoil-air predictive equation mainly affected the more-volatile pesticides and that the way in which relative humidity was accounted for was the most critical difference.

Assessing soil-air partitioning of PAHs and PCBs with a new fugacity passive sampler

“…Even small changes in temperature and RH can correspond to large changes in partitioning behavior between air, the passive sampling material (Huckins et al, 1990), and soil (Davie-Martin et al, 2015). Field measurements of temperature are incorporated into partition coefficients between air and the sampling material ( K sample-air ) using a modified van ‘t Hoff equation (SI).…”

“…Davie-Martin et al (2015) developed an equation that predicts K soil-air of individual compounds using 22 pesticide compounds in varying conditions: $$log{K}_{\mathit{soil}-\mathit{air}}=-26.2+0.714{\mathrm{italiclogK}}_{oa}+8291\frac{1}{T}-0.0218RH+0.121{\mathrm{italiclogf}}_{oc}$$ where log K oa is the logarithm of the octanol-air partition coefficient, T (K) is the mean environment temperature during deployment, RH (%) is relative humidity, and log f oc (%) is the logarithm of soil organic carbon content.…”

“…Organic carbon content correlates with a soil’s capacity to sorb semi-volatile contaminants (Dalla Valle et al, 2005; Davie-Martin et al, 2015; Schwarzenbach et al, 2003). It might therefore be expected that soils rich in organic matter would favor partitioning to soil through deposition.…”

Research on Occurrence and Development of Pasture Drought Events in Alpine Grassland using the Drought Threshold

“…Previous studies (Wang et al,2013;Daviemartin et al,2015;Paudel et al,2015)on soil relative humidity mostly use the observational data of meteorological stations, the data is 3 times a month, 8,…”

Air-soil diffusive exchange of PAHs in an urban park of Shanghai based on polyethylene passive sampling: Vertical distribution, vegetation influence and diffusive flux

“…However, large uncertainties exit in estimating air-soil partitioning coefficients and because of soil heterogeneity, e.g. during soil sampling vertical concentration gradients are disturbed leading to misinterpretation on soil fugacity (Ali et al, 2015;Davie-Martin et al, 2015;Donald and Anderson, 2017). Alternative in situ technologies have been developed to directly monitor the soil air, namely the gas phase in soil pores.…”