Distribution and composition of polycyclic aromatic hydrocarbons within experimental microcosms treated with liquid creosote

Abstract

Abstract-Temporal changes in the distribution and relative composition of 15 priority polycyclic aromatic hydrocarbons (PAHs) in water, sediment, and absorbed to polyvinylchloride (PVC) strips were assessed following direct application of liquid creosote to aquatic microcosms. Fourteen microcosms were treated with nominal creosote concentrations ranging from 0.06 to 109 mg/L and two microcosms served as controls. Quantitative analysis of PAHs was performed using high-performance liquid chromatography equipped with a fluorescence detector. Post-treatment concentration of PAHs in water decreased exponentially with time. At 2 d posttreatment, total PAHs (⌺ PAH) ranged from 7.3 g/L (lowest treatment) to 5,803.2 g/L (highest treatment); by 84 d, ⌺ PAH in the same microcosms was reduced to between 0.8 g/L and 13.9 g/L, respectively. The relative composition of PAHs in the water also changed with time; at 2 d posttreatment, ⌺ PAH in the lowest treatment (7.3 g/L) reflected contribution from nine PAHs, whereas only two PAHs contributed to this concentration (0.8 g/L) at 84 d. Low and high molecular weight (mol. wt.) PAHs were lost first from the water column, followed by PAHs of intermediate mol wt. In sediments, a dose-dependent increase in ⌺ PAH was observed above 0.59 mg/L creosote up to 28 d, followed by a decline thereafter in all but the highest treatment. Total PAHs in sediment ranged from 0.91 g/g (lowest treatment) to 63.9 g/g (highest treatment) at 28 d. A dose-dependent relationship was also observed in PVC strips, with ⌺ PAH on PVC ranging from 0.05 to 88 g/cm 2 at 31 d and 0.04 to 18.4 g/ cm 2 at 58 d posttreatment. A mass balance evaluation showed that 88.3% of PAHs was lost from the system after 1 month, indicating that liquid creosote is attenuated relatively quickly in aquatic environments.

Distribution and Composition of Polycyclic Aromatic Hydrocarbons Within Experimental Microcosms Treated With Creosote-Impregnated Douglas Fir Pilings

“…Construction and dimension details for the microcosms are provided in Bestari et al [17]. Below we provide only a brief synopsis of the microcosm design.…”

“…Detailed methods for water and PVC sample collection and preservation are discussed in Bestari et al [17].…”

“…These compounds, arranged in order of increasing molecular weight, in- Detailed water, sediment, and PVC sample preparation and extraction methods are discussed in Bestari et al [17], and only a brief outline is presented below. All solvents were highperformance liquid chromatography (HPLC) grade.…”

“…Marine-grade, Douglas fir pilings (15-20 cm diameter; 1.2 m length) were treated with the same creosote as that used in a parallel assessment of liquid creosote [17] to facilitate comparisons between the two studies. We used marine-grade pilings as these are treated with 100% creosote rather than a mixture of creosote and heavy bunker oil.…”

“…Prior to analysis, each wood core disk was chopped with a knife into small pieces. The wood pieces were added to a Soxhlet extraction apparatus and extracted in the same manner as that described for sediments in Bestari et al [17].…”