Differentiated Estimation of the 137Cs Content on the Biogenic and Lithogenic Suspended Matter in the Black Sea

IF 0.7 4区地球科学 Q4 GEOCHEMISTRY & GEOPHYSICS

Geochemistry International Pub Date : 2023-07-06 DOI:10.1134/S0016702923040122

I. G. Sidorov, O. N. Miroshnichenko, V. Yu. Proskurnin, A. A. Paraskiv

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Abstract—Sedimentation transport of ¹³⁷Cs can lead to the significant accumulation of this radionuclide at depths that could not be reached through the vertical water exchange alone; therefore, a comparative assessment of its contents for different types of suspended matter (SM) and regions of the Black Sea is of particular interest. For this purpose, we have collected samples of SM and seawater at deep-water and coastal stations for the subsequent determination of the ¹³⁷Cs activity in the surface water layer. To calculate the fraction of lithogenic matter, the potassium content in the SM was additionally determined. The range of ¹³⁷Cs content on SM at different stations differed by more than an order of magnitude: from 7 to 111 Bq/kg for specific activity, and from 0.03 to 0.69% for its content on SM, in % of the total content in the surface water layer. Stations located farther away from the coast were characterized by the lowest percentage of ¹³⁷Cs in SM, while its content at the coastal stations was more variable. The comparison of the lithogenic and biogenic contribution to SM and data on ¹³⁷Cs for different stations suggests that the content of this radionuclide on SM is primarily determined by the dynamic variations of the lithogenic matter. Based on the ¹³⁷Cs migration on SM, the Black Sea is divided into at least two types of regions. One regions are water areas far removed from sources of lithogenic matter where SM is formed mainly due to the hydrobiont activity. The ¹³⁷Cs content in SM due to the predominance of biogenic matter and an insignificant concentration of lithogenic matter in this case accounts for hundredths of a percent of its total content in the surface water layer. Other regions are coastal and shelf water basins, which, on the one hand, are subjected to the significant coastal and river lithogenic runoff, and on the other, they are characterized by the elevated trophicity and biological productivity. In these water areas, ¹³⁷Cs content on SM owing to the variability of biotic and abiotic factors is more variable and can fluctuate from values typical for the open sea to an order of magnitude higher.

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黑海生物成岩悬浮物中137Cs含量的差异性估计

摘要- 137Cs的沉降输运可导致该放射性核素在仅通过垂直水交换无法达到的深度显著积累;因此，对黑海不同类型悬浮物(SM)和区域的含量进行比较评估是特别有意义的。为此，我们在深水站和沿海站采集了SM和海水样品，随后测定了表层水层的137Cs活度。另外测定了SM中钾的含量，以计算成岩物质的含量。不同站点SM上137Cs含量的变化幅度相差一个数量级以上:比活度为7 ~ 111 Bq/kg，比活度为0.03 ~ 0.69%，占表层水层总含量的%。离海岸较远的气象站的SM中137Cs的含量最低，而沿海气象站的137Cs含量变化较大。通过对不同台站137Cs资料的对比分析，认为SM中137Cs的含量主要由成岩物质的动态变化决定。根据137Cs在SM上的迁移，黑海至少分为两种类型的区域。一个区域是远离成岩物质来源的水域，主要是由于水生物活动而形成的SM。SM中137Cs的含量占表层水层总含量的百分之几，主要是由于生物物质占主导地位，而岩质物质浓度不高。其他地区则是沿海和陆架水域，一方面受到海岸和河流产岩径流的影响，另一方面又具有较高的营养和生物生产力。在这些水域，由于生物和非生物因素的可变性，SM上的137Cs含量变化更大，可以从公海的典型值波动到更高的数量级。

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来源期刊

Geochemistry International 地学-地球化学与地球物理

CiteScore

1.60

自引率

12.50%

发文量

审稿时长

1 months

期刊介绍： Geochemistry International is a peer reviewed journal that publishes articles on cosmochemistry; geochemistry of magmatic, metamorphic, hydrothermal, and sedimentary processes; isotope geochemistry; organic geochemistry; applied geochemistry; and chemistry of the environment. Geochemistry International provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.