Investigating Desorption of Native Pyrene from Sediment on Minute- to Month-Timescales by Time-Gated Fluorescence Spectroscopy

Abstract

We investigated desorption of native pyrene from field-aged sediments using time-gated, laser-induced fluorescence (LIF) spectroscopy. LIF is superior to conventional analytical methods for the measurement of quickly changing dissolved pyrene because it allows observations at minute-scale resolution, has a low detection limit (approximately 1 ng/L), and minimizes sample loss and disturbance since it requires no system subsampling and chemical analysis. The efficacy of LIF was demonstrated in studies of pyrene desorption from Boston Harbor sediment segregated into different size-fractions (38-75, 75-106, and 180-250 microm diameter) and used in varying solid-to-water ratios (20, 70, and 280 mg(solid)/L). The effects of particle size and solid loading on desorption were consistent with diffusion physics. For suspension conditions between 20 and 280 mg(solids)/L, we observed desorption continuing toward an apparent plateau level over the course of weeks to months. This implies that the characteristic desorption time of pyrene from fine sediments and, by inference, other sediment-bound hydrophobic organic compounds (HOCs) of similar hydrophobicity, exceeds the typical characteristic times for pore water flushing and resuspension events. Consequently, the assumption of local sorption equilibrium in modeling efforts would be inappropriate.

Influence of Low Oxygen Tensions and Sorption to Sediment Black Carbon on Biodegradation of Pyrene

“…The log K d values estimated for NQB and NQB-BC sediments were 3.38 Ϯ 0.04 and 4.09 Ϯ 0.04, respectively. The former was close to, but lower than, the value previously reported with this sediment, 3.72 Ϯ 0.17 (1), presumably because the sorptive equilibrium for this system was not fully reached even at 200 h (20).…”

“…Sediment samples (20 to 80 mg) were introduced into 60-ml BOD glass bottles (Wheaton), together with 50 ml of distilled water containing 8.4 ng/ml dissolved 14 C-pyrene (5,000 dpm/ml). The resulting range of concentrations of suspended solids (400 to 1,600 mg solids/liter) can be considered realistic for natural estuary, harbor, or tributary water columns, which typically contain 20 to 500 mg of solids/liter (20), and for waters receiving inputs of solids (130 to 2,300 mg solids/liter) during resuspensions of PAH-polluted sediments (37). The radiolabeled compound had been added to the aqueous solution dissolved in acetone (0.1 ml acetone per liter of water).…”

Inferring Black Carbon Concentrations in Particulate Organic Matter by Observing Pyrene Fluorescence Losses

“…The choice of pyrene as the chemical probe for our analysis was based on observations by Rudnick and Chen , previous work in our research group ,, , and experience in our lab. First, pyrene has a substantial affinity for BC , .…”

“…Next, Rudnick and Chen found this PAH only occurred at ng/L levels in Boston Harbor seawater, implying we could control total pyrene levels in our samples with μg/L spikes. Finally, truly dissolved pyrene concentrations can be assessed via static fluorescence measures down to subμg/L levels , , and the uniquely long fluorescence lifetime of this PAH allows dissolved pyrene to be detected among many other natural and pollutant fluorophores using time-gated approaches, if necessary , .…”

A Fluorescence-Based Method for Rapid and Direct Determination of Polybrominated Diphenyl Ethers in Water

“…The new method is based on characteristic fluorescence properties of PBDEs under room temperature. Although fluorescence-based methods have been widely used in analyzing hydrophobic organic compounds in aqueous phase [ 20 – 23 ], sediments [ 24 , 25 ], and engineered nanoporous materials [ 26 ], its application to analyze PBDEs has not been reported to our knowledge. The major objectives of this study are therefore to (1) characterize fluorescent properties of six major PBDEs congeners that are commonly found in environment and (2) demonstrate the efficacy of the fluorescence spectroscopy method for measuring the concentrations of PBDEs in aqueous samples.…”