Historical analysis of domestic wastewater pollution and its measures in Lake Teganuma basin using surfactant concentrations recorded in sediment core samples

In order to learn whether it is possible to clarify the history of water pollution and its countermeasure from the fluctuation of chemicals accumulated in the sediment core of the lake, concentrations of linear alkylbenzenesulfonates (LAS) in sediment core samples collected from Lake Teganuma, which was severely polluted by domestic wastewater, were determined. The results were compared with concentrations of LAS in the lake water, waters of two large inflowing rivers, and in sewage from the Lake Teganuma basin. Sediment cores collected in 2003 and 2004 recorded the history of domestic wastewater pollution in the basin during the previous 25–35 years. LAS concentrations in the sediment core drastically decreased after the 1990s, and similar reductions of LAS were observed in the river and lake waters. Large amounts of LAS have still been used in the basin during 1980s to 2017, the drastic decrease of LAS concentrations in both the sediment and the river and lake waters is attributable the expansion of sewer system coverage in the basin since 1981. The effect of lake dredging was also estimated by the changes in surfactant concentrations. Thus, historical changes in not only pollution levels but also social factors can be assessed by determining sediment concentrations of chemicals in daily use such as LAS.