Seasonal variation in composition and properties of aquatic humic substances

Abstract During a period of 1 year, natural humic water was sampled once every season. Several chemical parameters were measured including 3 different aluminium species. Chemical composition of the samples were studied before and after tube dialysis. High-performance size exclusion chromatography (HPSEC) was performed on the samples in order to study molecular weight distributions. The ability of natural humus substances to complex/adsorb organic micropollutants (OMP) as a function of contact time was studied. This was done by adding known amounts of OMP to the samples and measuring the recovery of OMP by cyclohexane extraction. The natural content of polycyclic aromatic hydrocarbons (PAH) was also determined. No major variations in the chemical composition of the humic water from the four seasons were found. Furthermore no significant variation in molecular weight distribution was found. The complexation/adsorption ability of humic substances towards OMP was found to differ with the seasons. Spring and summer humus showed a significant greater complexation/adsorption ability than the other two qualities. The background level of PAH in the humus water was also found to vary, with the largest PAH content during fall.