| dc.description.abstract | Nonylphenol polyethoxylates (NPEOs) is one of the major classes of nonionic surfactants used in Taiwan and over 48 · 106 kg were produced and consumed each year. However, large quantities of these surfactants in wastewaters are discharged into the rivers directly because of Taiwan’s deficient municipal and industrial wastewater treatments. NPEOs can be biodegraded into: (a) shortening of the polyethoxy chain, resulting in the formation of nonylphenol (NP) and shorter ethoxy chain NPEO residues (such as NP1EO and NP2EO); and (b) carboxylation of the terminal ethoxy or nonyl unit, resulting in the formation of nonylphenol polyethoxy carboxylates (NPECs), or carboxy-nonylphenol polyethoxy carboxylates (CNPECs). We called these compounds as persistent nonylphenolic pollutants. The survey of occurrence and concentration of persistent nonylphenolic compounds in the rivers in Taiwan was undertaken to establish environmental concentrations and to support surface water protection programs.
The method involves extraction of the samples by graphitized carbon black (GCB) solid-phase cartridge, which can be used to extract NP and the degradation products (NPnEC and CNPnEC) simultaneously. These persistent nonylphenolic pollutants were then identified and quantified by large-volume injection GC-MS analysis. This technique provides high precision and sensitivity for persistent nonylphenolic pollutants, to quantitation at < 0.1 ?g/L in 200 ml of water samples. Recovery of nonylphenol (NP) and nonylphenoxyacetic acid (NP1EC) in spiked water samples were 84% (RSD=6.0%, n=5) and 95% (RSD=3.9%, n=5), respectively. Concentrations of nonylphenol (NP) in 19 main rivers of Taiwan were in the range n.d. to 5.1 ?g/L, which are below the threshold concentration (10 ?g/L) for vitellogenin induction in fish. However, 99% of these water samples from rivers exceed the predicted-no-effect concentration (PNEC) 0.33 ?g/L as proposed recently by European Union. The average recovery of the 4-t-OP surrogate for NP analysis was 86% (RSD =10.1%, n=136). The total concentrations of shortened NPEO (i.e., NP1EO and NP2EO) and carboxylates metabolites (i.e., NP1EC, NP2EC, CNP1EC and CNP2EC) in rivers were ranged from n.d. to 115.0 ?g/L. The average recovery of the 4-t-OP1EC surrogate for carboxylated nonylphenolic pollutant analysis was 89% (RSD =11.8%, n=136). The results indicated that the method performed satisfactorily despite the variable compositions of environmental samples.
The significant higher concentrations of carboxylated nonylphenolic pollutants were detected in the river waters as compared to that of NP, NP1EO and NP2EO metabolites. These carboxylated nonylphenolic compounds can be regarded as potential precursors for the formation of nonylphenol under various biotransformation conditions. | en_US |