ABSTRACT

Concentrations of acid volatile sulfides (AVS) as metal sulfides in three different size fractions (<30 nm, 30–200 nm, >200 nm) at Lake Teganuma were measured using a nano-filtration followed by a purge-trap gas chromatography with a flame photoionization detector (GC-FPD). Fresh water samples were collected at four sites in the lake and sequentially filtered with 30 nm and 200 nm pore size filters on site immediately after the sampling. The concentrations of unfiltered AVS (AVS_total) ranged from 0.6 to 1.4 nmol/kg, among which the highest concentration was found in a lotus colony site. Except for the lotus colony site, the relative AVS abundances in the three size-fractions were quite similar. It was found that >80% of AVS_total existed in the <30 nm size fraction, while only 10~20% in 30–200 nm and >200 nm size fractions. In the lotus colony site, on the other hand, <30 nm fraction contributed only ~5% but the 30–200 nm size fraction exhibited most dominant contribution (~80%), although the AVS_total concentration in the lotus colony site was similar to those in other sites. Present observation shows that metal sulfides exist in fresh water environment and mainly reside in <30 nm size fraction, but even larger metal sulfide nanoparticles with the size of 30–200 nm can be formed, which seem to be formed from <30 nm size fraction through a relatively rapid process.