Behaviour of ¹³⁷Cs and ²¹⁰Pb inventory at three candidate reference sites for erosion study in the upstream Citarum watershed area, West Java, Indonesia

ABSTRACT

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 ¹³⁷Cs in RS6 cor 4 and 7 (<0.16 ± 0.08 Bq kg^–1). MDA quantification implies that the inventory below MDA eroded greater than its maximum value (76.02 tons ha^–1 a^–1). The comparison ¹³⁷Cs 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 ¹³⁷Cs and ²¹⁰Pb_ex in the 20–30 cm in the bulk sample. The highest H₀ (142.04 kg m^–2), the relaxation length λ, and proportion of 20% of ¹³⁷Cs in 20–30 cm depth imply that ¹³⁷Cs inventory activity is possibly deeper than 30 cm. This study recommends that Mt. Papandayan could be the alternative RS for the upstream Citarum watershed.

KEYWORDS:

• cesium-137
• Citarum watershed
• FRN
• gamma spectroscopy
• lead-210
• MDA level
• natural radioactivity
• reference site
• West Java

Acknowledgement

The authors would like to thank the Northeast Forestry University, China, Especially to my great Supervisor, Professor Duan Wen Biao, thank you for the research funding support, direction and guidance in compiling this paper. I also thank to the Research Center for Radiation Process Technology, National Research and Innovation Agency, Indonesia, which has supported our accommodation to collect sample data, conduct the experiment, and measure samples. Our colleagues from the Research Center for Radiation Process Technology, National Research and Innovation Agency, Indonesia, M. Fajar Sanjaya, Arief Adhari, Megy Stefanus, and Rahmad Ramdani are acknowledged for helping to collect samples, prepare the samples and operate the MCA gamma spectroscopy to measure the FRN activity.

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Funding

The author(s) reported there is no funding associated with the work featured in this article.