Environmental fate of nonylphenol ethoxylates: Differential adsorption of homologs to components of river sediment

Abstract

Nonylphenol ethoxylate (NPEOx) homologs present in commercial mixtures were rapidly adsorbed to and desorbed from native river sediment. Adsorption isotherms, established using high‐performance liquid chromatography analysis to monitor individual homologs NPEO3 to NPEO13 simultaneously, were linear for each component adsorbing to native sediment, organic‐free sediment, and kaolinite, usually with small positive intercepts on the isotherms indicating an additional low‐capacity, high‐affinity binding site. The adsorption partition coefficients (Kd) for the native sediment decreased progressively from 1,460 L/kg for NPEO3 to 450 L/kg for NPEO10, then increased again slightly for higher homologs. In contrast, Kd values for organic‐free sediment (range 230–590 L/kg) or kaolinite (190–490 L/kg) increased steadily from NPEO3 to NPEO13. Adsorptions to silica and alumina were very weak, but to sewage sludge all components adsorbed strongly (Kd values 12,000–33,000, with a maximum at NPEO7). The adsorption to sewage sludge was related to the low‐capacity, high‐affinity sites observed for native sediment. Dependence of Kd values on ethoxylate chain length was analyzed, in terms of both possible adsorption mechanisms, and the environmental fate and impact of NPEOxs as endocrine disruptors.

Pollution of NPEOs in four municipal sewage treatment plants in the north of China

“…Moreover, it was found that the small analogs of NPnEO and NP were adsorbed to a greater extent due to the high content of organic matter in the sludge. These results are similar to that of John et al [3]. The level of NP, NP1EO, and NP2EO in the sludge has been reported to be 8.4-4 000, 3.9-680, and 1.5-280 mg/kg, while the levels of total NPEOs were 9-370 mg/ kg with K d being 1.2x10 4 -3.3x10 4 L/kg [3], which is similar to our results.…”

“…Consequently, these small metabolites have been extensively detected in the environment. Moreover, these small metabolites were reported to be more toxic, easier to be bioaccumulated, and easier to be concentrated in the sediment [1][2][3][4][5][6][7][8]. More recent studies have revealed that some of these small metabolites, mainly NP and NP1EO, bear endocrine disrupting activity.…”

Partition of Nonylphenol and Related Compounds Among Different Aquatic Compartments in Tiber River (Central Italy)

“…Several studies (John et al, 2000;Isobe et al, 2001;Ferguson et al, 2001) reported that short ethoxy-chain NPEOs were moderately hydrophobic contaminants that were primarily associated with organic-rich particle fraction in aqueous systems. However, the increase of NPEOs ethoxylation led to an increased association of metabolites with mineral surface, which could largely contribute to polyethoxylate surfactants sorption on solids (Brownawell et al, 1997).…”

Distribution, exposure pathways, sources and toxicity of nonylphenol and nonylphenol ethoxylates in the environment

“…The levels of NP, OP, OPPEs and NPEs in sediments are presented in Table 3. Adsorption processes controlling the partition of nonylphenol ethoxylates to sediments demonstrated that the organic content of the sediments was one of the most important determinants of the adsorption process, especially for short-chain nonylphenol ethoxylates (John et al, 2000). Higher concentrations of nonylphenol and its ethoxylates were detected in samples from developed countries as compared to samples from developing countries.…”