DISSOLVED ORGANIC-CARBON FRACTIONS IN FINNISH AND MAINE (USA) LAKES

Dissolved organic carbon (DOC) was examined in 17 Finnish lakes, 6 Fin nish streams, and 30 Maine (USA) lakes by fractionating DOC into hydro phobic acids and neutrals, and hydrophilic acids, bases, and neutrals. A procedure using XAD-8, anion-exchange, and cation-exchange resins w as used. In every sample, organic acids dominated, averaging 82% of DO C. No major differences in DOC fractions between Maine lakes and Finni sh lakes were found. However, differences in DOC fractions were found between lakes with low and high DOC. The proportion of hydrophobic aci ds increased with increasing POC, whereas the proportion of hydrophili c acids decreased with increasing DOC. Low DOC lakes had a greater pro portion of their DOC as hydrophilic neutrals compared with high DOC la kes On the basis of the fractionation results, linear equations were d eveloped for the relationships between the total DOC and the proportio ns of hydrophobic and hydrophilic acids of the total DOC. (C) 1998 Els evier Science Ltd.