Chloroform production from the chlorination of aquatic humic material: The effect of molecular weight, environment and season

Abstract

Humic material from various aqueous environments and from laboratory microbial cultures was segregated into humic and fulvic acid fractions and then each fraction was separated into eight molecular weight ranges by ultrafiltration. The fractionated material was then chlorinated in aqueous solution and the amount of chloroform produced was measured. Chloroform concentration per unit weight humic material passed through a maximum at molecular weight about 20,000–30,000 for the fulvic acids, whereas the CHCl 3 concentration decreased with increasing molecular weight above 20,000–30,000 for the humic acids. Only minor fluctuations in chloroform concentrations were apparent for samples from various aqueous environments (lake, river, stream, swamp, microbial) and for samples from a single environment obtained during different seasons of the year. Based on the total amount of material isolated from the original samples and the chloroform production per unit weight, the major chloroform precursors in aquatic humic material were the low molecular weight (< 30,000) fulvic acid fractions. Unfortunately, because of their low molecular weight and high surface activity, these fractions will probably prove to be the most difficult to remove by standard water treatment processes.