下水処理場下流のムール貝にラジウムが含まれているとの研究報告(Mussels downstream of wastewater treatment plant contain radium, study reports)

2024-06-01

2024-05-31 ペンシルベニア州立大学(PennState)

ペンシルベニア州立大学の研究者たちは、淡水ムール貝が環境の清浄度を示すバイオモニターであることを発見しました。ムール貝は有機物を摂取し水をろ過するため、その組織や殻に放射性物質を含む環境物質が蓄積されます。研究者たちは、20年以上にわたり油・ガス産業の廃水を処理した西ペンシルベニアの施設の下流に生息するムール貝を分析し、フラッキング廃水由来のラジウムを検出しました。廃水処理後の水は高い塩分濃度を持ち、放射性物質を含むため、ムール貝はそれを吸収していました。この結果、ムール貝の組織や殻に高濃度のラジウムが検出されました。研究は、放射性物質の環境中での影響と将来の規制に役立つ可能性があるとしています。

＜関連情報＞

石油・ガス生産水の放射能が淡水ムール貝に蓄積 Radioactivity from oil and gas produced water accumulated in freshwater mussels

Katharina Pankratz, Nathaniel R. Warner
Science of The Total Environment Available online: 2 April 2024
DOI:https://doi.org/10.1016/j.scitotenv.2024.172151

Highlights

Discharge of oil and gas produced water (OGPW) led to increased radium in mussels.
Shell & tissue metal/Ca, ⁸⁷Sr/⁸⁶Sr, and ²²⁸Ra/²²⁶Ra indicate areas impacted by OGPW.
Elemental & isotopic signatures persist in mussels years after discharges ceased.

Abstract

Legacy disposal of oil and gas produced water (OGPW) to surface water has led to radium contamination in streambed sediment creating a long-term radium source. Increased radium activities pose a potential health hazard to benthic organisms, such as freshwater mussels, as radium is capable of bioaccumulation. This project quantifies the impact of OGPW disposal on adult freshwater mussels, Eurynia dilatata, which were examined along the Allegheny River adjacent to a centralized waste treatment facility (CWT) that historically treated and then discharged OGPW. Radium isotopes (²²⁶Ra and ²²⁸Ra) were measured in streambed sediment, mussel soft tissue, and mussel hard shell collected upstream, at the outfall, 0.5 km downstream, and 5 km downstream of the CWT. Total radium activity was significantly higher (p < 0.05) in mussel tissue (mean = 3.44 ± 0.95 pCi/g), sediment (mean = 1.45 ± 0.19 pCi/g), and hard shell (mean = 0.34 ± 0.11 pCi/g) samples 0.5 km downstream than background samples collected upstream (mean = 1.27 ± 0.24; 0.91 ± 0.09; 0.10 ± 0.02 pCi/g respectively). Mussel shells displayed increased ²²⁶Ra activities up to 5 km downstream of the original discharge. Downstream soft tissue and hard shell ⁸⁷Sr/⁸⁶Sr ratios, as well as hard shell metal/calcium (e.g., Na/Ca; K/Ca; Mg/Ca) and ²²⁸Ra/²²⁶Ra ratios demonstrated trends towards values characteristic of Marcellus OGPW. Combined, this study demonstrates multiple lines of evidence for radium retention and bioaccumulation in freshwater mussels resulting from exposure to Marcellus OGPW.