Vertical Distribution of Nonylphenol Ethoxylates and Their Derivatives in Sediments of a Freshwater Reservoir

Abstract

The distribution of nonylphenol ethoxylates (NPEOn) and their derivatives of nonylphenol (NP) and nonylphenoxy ethoxy acetic acids (NPEnC) in the sediments of a relatively closed freshwater reservoir was investigated using sediment layers sliced from undisturbed sediment cores collected with a gravity core sampler at three sampling sites (St. 1, St. 2 and St. 3) along the water flow direction. The relationships between the bound content of these compounds and the sediment organic matter as well as the likely transformation pathways were evaluated. The total content of NPEOn (n=1-15) fell in 84.6-336.5, 59.9-135.5 and 77.0-623.4 μg/kg-dry for all sliced layers at St.1, St.2 and St.3, respectively, with the content of individual NPEOn species showing a general decreasing trend with the attached molar number of the ethoxy (EO) chain. Compared to each detected NPEOn species, the bound content of NP was much higher, falling in 73.2-248.4, 79.9-358.2 and 25.5-1,988.4 μg/kg-dry at St. 1, St. 2 and St. 3, respectively. A general increasing trend of the NP content along the water flow direction of the reservoir was revealed. NPEnC (n=1-10) varied in 1.93-4.12, 2.85-9.84 and 1.05-19.1 μg/kg-dry for sediment at the respective site of St. 1, St. 2 and St. 3, with the averaged values at these sites (2.91, 4.71 and 6.72 μg/kg-dry) showing an increasing trend from the upstream to the downstream.For NPEnC, a parametric trend of increases in the content of NPE 1 C, NPE 2 C and NPE 3 C with the bound sediment organic matter (9.06-11.8%) seemed to be existent. Furthermore, the computed magnitudes of NPEO 1-2 / NPEO 1-15 , NP/NPEO 1-15 and NPEC 1-10 /NPEO 1-15 suggested that non-oxidative hydrolytic transformation was probably prevailing within the sedimented mud phase of the reservoir, with the oxidative hydrolytic transformation pathway being less involved.

Sorption Characteristics of Cesium Onto Reservoir Sediment

“…The use of sediment from the pre-reservoir, rather than the main reservoir, was mainly due to the considerations that this pre-reservoir is a natural reservoir and it has been frequently used as the study site for investigation of the occurrence and behavior of a variety of pollutants (including nitrogen, phosphorus, nonionic surfactants and natural estrogens) with the projects from the Ministry of Land, Infrastructure, Transport and Tourism of Japan 13,14) ; and the large number of data obtained so far can facilitate future comparisons of the behavior of different pollutants including cesium targeted in this study.…”