BEHAVIOR OF ALKYLPHENOL POLYETHOXYLATE SURFACTANTS IN THE AQUATIC ENVIRONMENT .3. OCCURRENCE AND ELIMINATION OF THEIR PERSISTENT METABOLITES DURING INFILTRATION OF RIVER WATER TO GROUNDWATER

The behaviour of various persistent metabolites derived from nonylphen ol polyethoxylate (NPnEO) surfactants was studied during infiltration of river water to groundwater at two field sites situated in the north ern part of Switzerland (Glatt River and Sitter River). Nonylphenol (N P), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2E O), nonylphenoxy acetic acid (NP1EC) and nonylphenoxy(ethoxy) acetic a cid (NP2EC) were observed in the two investigated rivers at relatively high concentrations with average values of the individual types of no nylphenolic compounds ranging from 1.8 to 25 mu g/l. The average conce ntrations of NP, NP1EO and NP2EO in groundwater were significantly low er (range <0.1-1 mu g/l) suggesting an efficient elimination of these compounds during infiltration. In contrast, the elimination of nonylph enoxy carboxylic acids was less efficient. Most of the observed elimin ation occurred in the first 2.5 m of the aquifer, while further decrea se in concentration was rather slow. In one sampling period, residual concentrations of nonylphenolic compounds up to 7.2 mu g/l were detect ed in a pumping station used for drinking water supply which is situat ed 130 m from the Glatt River bed. Concentrations of NP, NP1EO and NP2 EO in both river water and groundwater showed a pronounced seasonal va riability with higher values observed during winter. The data suggest that low temperatures, which prevail in winter, significantly reduce t he elimination efficiency of NP and to a lesser extent of NP1EO, while the behaviour of NP2EO was not affected. Such a behaviour indicates b iogical transformation as the responsible elimination process. A compa rison of average elimination efficiences of nonylphenolic compounds wi th those of pentachlorphenol (PCP) and nitrilotriacetate (NTA) gives t he following sequence: NTA greater than or equal to NP2EO > NP1EO > NP > PCP > NP1EC = NP2EC.