Behaviour of chloroform from pulp bleaching in an ice-covered finnish lake

Abstract

Samples of ice and water from different depths were collected from various parts of Lake Näsijärvi, Finland. Chloroform was analysed by liquid-liquid extraction, capillary gas chromatography followed by electron capture detection and confirmation by gas chromatography/mass spectrometry. Maps of the regional variation of chloroform and sodium-lignin sulfonates (NaLS) show that under winter conditions with an inverse stratification the effluents of a pulp mill containing chloroform and NaLS fill the depressions of the lake bottom and flow as a thin, high-density waste water current downslope northeastward against the southward directed upper current of the epilimnion. Plots of chloroform against Ca indicate that there is only a weak net removal of chloroform from combined solution and suspension. Thus mass transfer to the atmosphere is confined in Lake Näsijärvi to seasons with vertical mixing of the water masses. © 1986.