Behaviour of Cs and Pb inventory at three candidate reference sites for erosion study in the upstream Citarum watershed area, West Java, Indonesia.

The fallout radionuclide (FRN) analysis needs a reference site (RS) inventory to determine erosion and sedimentation in the study area. The investigated area is in the upstream Citarum watershed, West Java, Indonesia. Twenty-seven corings and 22 scrap samples have been prepared well and measured using HPGe gamma spectroscopy. The data below the minimum detectable activity (MDA) was found for Cs in RS6 cor 4 and 7 (<0.16 ± 0.08 Bq kg). MDA quantification implies that the inventory below MDA eroded greater than its maximum value (76.02 tons ha a). The comparison Cs inventory in this study is lower than the three estimation models; however, the inventory of Mt. Papandayan is closer to the model. This study found the depth percentage of 20-30 cm using the proportion of 0-20 cm/0-30 cm ratio and predicted the portion of the existence of Cs and Pb in the 20-30 cm in the bulk sample. The highest (142.04 kg m), the relaxation length , and proportion of 20% of Cs in 20-30 cm depth imply that Cs inventory activity is possibly deeper than 30 cm. This study recommends that Mt. Papandayan could be the alternative RS for the upstream Citarum watershed.