Koji Amano

HPLC Determination of Linear Alkylbenzenesulfonate (LAS) in Aquatic Environment. Seasonal Changes in LAS Concentration in Polluted Lake Water and Sediment

Abstract An analytical method for linear alkylbenzenesulfonate (LAS) using HPLC was studied. It was found that the peaks of different LAS isomers with alkyl chain lengths between 11 and 14 could be separated by gradient elution with aqueous NaClO4 solution and acetonitrile. The pretreatment of the LAS in the environmental samples was studied and an easy-to-use method involving solvent extraction with 4-methyl-2-pentanone was developed. By using these techniques the concentrations of the different LAS analogues in environmental samples could be measured respectively. The method was used to determine LAS in the aquatic environment; and the seasonal changes of these chemicals were clearly observed.

Diffusive exchange of linear alkylbenzenesulfonates (LAS) between overlying water and bottom sediment

Linear alkylbenzenesulfonate (LAS) was detected in a 0–30 cm deep sediment column collected in Lake Teganuma (one of the most polluted lakes in Japan). The range of the LAS concentration in sediments was between 0.1 and 500 µg g−1 (C11–C14 homologs per dry solid) and its vertical profile showed a seasonal variation. A mathematical model, which includes a diffusion term and a biodegradation term, was used to simulate the temporal variation of LAS in the sediment column and to calculate the diffusive flux rate of LAS across the sediment/water interface. An averaged diffusion coefficient of 2.4 × 10−5 cm2 s−1 for the sediment interstitial water was obtained from sediment core samples located in Lake Teganuma. The biodegradation rate constant (0.002 d−1) of LAS in the sediment obtained from the model analysis was considerably less than that reported for LAS in anaerobic waters. These results confirm that a model describing diffusive transport and biodegradation of LAS in the sediments can simulate the temporal variation of LAS in near surface sediments. The diffusive flux rate from overlying water to bottom sediment was calculated to be between −0.20 and 0.52 (C11–C14 LAS) mg m−2 h−1 and the annual net flux rate was 0.7 g m−2 y−1.

Modeling for estimating representative water conditions in a river basin

Abstract The actual mechanism on the generation of pollution loading is so complicated that it should be simplified in modeling for its quantifications. Therefore, there is no perfect modeling for those. On the proposal of our new concept for modeling, we tried to describe the real phenomenon or mechanism from source to river more precisely. We have estimated generated pollution loading at a dry period per branch or drain in the middle basin of the Tama River. The data or materials for this investigation are based on the administrative informations which were summed up in 1981. In order to ascertain the calculated pollution loadings, these data were compared with the real water conditions which have been provided by the large-scale and simultaneous river survey in August 1981. We proposed the methodology for adjustment of observed values by ones from plural sections and described the real water conditions in the river. According to the ratio of estimated value and actual condition, we ascertained that our procedure or methodology of calculations for quantification of the generated pollution loadings is reasonable.