Determination of resin acids by gas chromatography and high-performance liquid chromatography in paper mill effluent, river waters and sediments from the upper Derwent Estuary, Tasmania

Abstract

Resin acids in effluent from a paper mill situated on the upper Derwent Estuary near Hobart, Tasmania (Australia) were determined by HPLC analysis of their 7-methoxycoumarin-4-yl and 7-acetoxycoumarin-4-yl methyl esters. Total concentrations ranged from 1.0 to 4.8 mg 1 −1 with a mean of 2.7 mg 1 −1 during 1991–1992. Capillary GC-flame ionization detection and GC-MS analyses of organic constituents in river waters collected in April 1992 confirmed the presence of resin acids derived from the paper mill effluent, but the concentrations were highly variable and strongly influenced by freshwater flow and tidal movements. At a site just 500 m downstream of the effluent discharge, concentrations ranged from <0.01 to 0.78 mg 1 −1 over a 6-h period. Resin acids were also found in sediments close to the discharge (up to 87 mg kg −1 dry mass), but amounts in sediments downriver were generally considerably less (most samples <7 mg kg −1). The major resin acids in the effluent were dehydroabietic, palustric, abietic and pimaric acids. Smaller amounts of isopimaric, neoabietic, levopimaric and sandaracopimaric acids were also found. The proportions of individual resin acids in some of the water and sediment samples showed considerable differences from those in the effluent. The abundance of resin acids with conjugated double bonds such as palustric, levopimaric and neoabietic acids were particularly variable suggesting that they are more easily degraded. Resin acids of the pimarane type, such as pimaric acid, were considerably more stable. Variations in the water column distributions reflect both degradation of the more labile resin acids and redistribution of the resin acids between aqueous, colloid and sediment phases. Dehydroabietic acid was the most resistant to degradation and in some water samples it represented up to 66% of the resin acids compared with only 34% in the effluent. This result confirms earlier observations, and suggests that dehydroabietic acid could be used as a tracer for organic matter derived from the paper mill.