Methodological and Environmental Impacts on Bioaccessibility Estimates Provided by Single-Point Tenax Extractions

Single-point Tenax extractions (SPTEs) of hydrophobic organic contaminants provide estimates of bioaccessibility through consistent measures of the chemical concentration initially in the rapidly desorbing fraction in sediment (C _rapT0), such that a constant ratio is expected between SPTE and C _rapT0 (C _T /C _rapT0, where T is the duration of the SPTE). As environmental factors (i.e., aging time and organic carbon content) and contaminant hydrophobicity can affect the C _rapT0, the utility of the SPTEs as exposure estimates hinges on the consistency of the C _T /C _rapT0 ratio. Individually these factors have little impact on the ability of SPTEs to represent bioaccumulation, but the effect of these factors in combination, as well as SPTE methodological variation on the C _T /C _rapT0 ratio is poorly understood. The current study evaluated how environmental and methodological variation-expressed as varying Tenax to organic carbon mass (Tenax:OC) ratios-impacts the C _24h/C _rapT0 ratio of pyrethroids in laboratory-spiked sediments. A multiple regression analysis was used to examine the impact of organic carbon, pyrethroid hydrophobicity, Tenax mass, and aging time on the C _24h/C _rapT0 ratio. Only aging time of the pyrethroids in sediment significantly affected the C _24h/C _rapT0 ratio with a slight decline of -0.0027/d in the C _24h/C _rapT0 ratio, and this decline was considered negligible as a consistent C _24h/C _rapT0 ratio of 1.46 ± 0.03 was observed across all experimental treatments. This result further demonstrates the consistency of SPTEs to estimate bioaccessibility of hydrophobic contaminants in sediment and subsequent exposure.