5:15 PM - 6:45 PM
[AOS12-P02] Distribution and behavior of dissolved silver in the Bay of Bengal and eastern Indian Ocean
Keywords:marine chemistry, silver, Bay of Bengal
[Background]
Anthropogenic activities release various metals, including silver, into the environment. Notably, silver is known to be highly toxic to aquatic organisms (Tsiola et al., 2017). In this study, we elucidated the distribution of dissolved silver in the Bay of Bengal and the eastern Indian Ocean, and examined the sources and behavior of silver in these regions. The Bay of Bengal, bordered by India, Bangladesh, and Myanmar, is an area of concern due to high population growth and rapid industrialization, which possibly increases the supply of silver into seawater.
[Methods]
The sampling stations are shown in the figure. At each station, from BA-5 to MY-7, seawater was collected from a depth of 10 m to about 10 m above the seafloor. Subsequently, the seawater samples were immediately filtered through a 0.2 µm pore size filter to remove particulate matter.
The quantification of dissolved silver was carried out using isotope dilution followed by inductively coupled plasma mass spectrometry, after extraction of dissolved silver from its seawater matrix using NOBIAS PA-1 chelating resin (Hitachi High-Tech).
[Results and Discussion]
Dissolved silver concentrations exceeded 100 pM below 1500 m at MY-7 and 80 pM below 2000 m at MY-11. The seawater of the Bay of Bengal showed relatively high levels of dissolved silver compared to those outside the Bay, which ranged between 60 pM and 80 pM (Kramer et al., 2011). Possible sources of silver in this region include shelf sediments around MY-11 and seamounts near to MY-7.
A strong positive correlation (R = 0.91 - 0.94) was found between the concentration of dissolved silver and dissolved oxygen in seawater below 50 m depth. In waters with low dissolved oxygen concentrations, the reduction of Ag(I) to Ag(0) may occur (Wimmer et al., 2020), potentially leading to the conversion of dissolved silver into particulate silver.
It is likely that the shelf sediments at bottom of BA-5 is a source of dissolved silver. In the upper 50 m of MY-7, the concentrations of dissolved silver were about 40 - 60 pM. At other stations, the concentrations ranged between 20 pM and 40 pM. These values contrasted those reported by previous studies quantifying dissolved silver in surface seawater in other regions, where dissolved silver concentrations were generally less than 10 pM (Kramer et al., 2011). Therefore, the coastal areas of the Bay of Bengal exhibited relatively high dissolved silver concentration.
The salinity of the surface seawater was found to be lower at shallower depths and decreased with river water inflow. This suggests that the elevated concentrations of dissolved silver in low-salinity waters suggests are likely attributable to the rivers discharging into the Bay of Bengal.
[Conclusions and Future plans]
We elucidated for the first time the behavior of dissolved silver in the coastal areas of the Bay of Bengal and the eastern Indian Ocean. Our data indicate that anthropogenic activities, coastal inputs, and environmental factors such as dissolved oxygen influenced the distribution of dissolved silver in the study region. We recommend future studies to focus on quantifying particulate silver in aerosols, marine sediments, seawater, and in surrounding river water to gain a better understanding of the sources and behavior of silver in seawater.
[References]
Tsiola, A., Pitta, P., Callol, A., Kalantzi, M., Mylona, K., Santi. I., Toncelli, C., Pergantis, S., Tsapakis, M., 2017. The impact of silver nanoparticles on marine plankton dynamics: Dependence on coating, size and concentration. Science of The Total Environment, 601-602, 1838-1848
Kramer, D., Cullen, J.T., Christian, J.R., Johnson, W.K., Pedersen, T.F., 2011, Silver in the subarctic northeast Pacific Ocean: Explaining the basin scale distribution of silver, Marine Chemistry, 123, 133-142
Wimmer, A., Urstoeger, A., Funck, N.C., Adler, F.P., Lenz, L., Doeblinger, M., Schuster, M., 2020. What happens to silver-based nanoparticles if they meet seawater?, Water Research, 171, 115399.
Anthropogenic activities release various metals, including silver, into the environment. Notably, silver is known to be highly toxic to aquatic organisms (Tsiola et al., 2017). In this study, we elucidated the distribution of dissolved silver in the Bay of Bengal and the eastern Indian Ocean, and examined the sources and behavior of silver in these regions. The Bay of Bengal, bordered by India, Bangladesh, and Myanmar, is an area of concern due to high population growth and rapid industrialization, which possibly increases the supply of silver into seawater.
[Methods]
The sampling stations are shown in the figure. At each station, from BA-5 to MY-7, seawater was collected from a depth of 10 m to about 10 m above the seafloor. Subsequently, the seawater samples were immediately filtered through a 0.2 µm pore size filter to remove particulate matter.
The quantification of dissolved silver was carried out using isotope dilution followed by inductively coupled plasma mass spectrometry, after extraction of dissolved silver from its seawater matrix using NOBIAS PA-1 chelating resin (Hitachi High-Tech).
[Results and Discussion]
Dissolved silver concentrations exceeded 100 pM below 1500 m at MY-7 and 80 pM below 2000 m at MY-11. The seawater of the Bay of Bengal showed relatively high levels of dissolved silver compared to those outside the Bay, which ranged between 60 pM and 80 pM (Kramer et al., 2011). Possible sources of silver in this region include shelf sediments around MY-11 and seamounts near to MY-7.
A strong positive correlation (R = 0.91 - 0.94) was found between the concentration of dissolved silver and dissolved oxygen in seawater below 50 m depth. In waters with low dissolved oxygen concentrations, the reduction of Ag(I) to Ag(0) may occur (Wimmer et al., 2020), potentially leading to the conversion of dissolved silver into particulate silver.
It is likely that the shelf sediments at bottom of BA-5 is a source of dissolved silver. In the upper 50 m of MY-7, the concentrations of dissolved silver were about 40 - 60 pM. At other stations, the concentrations ranged between 20 pM and 40 pM. These values contrasted those reported by previous studies quantifying dissolved silver in surface seawater in other regions, where dissolved silver concentrations were generally less than 10 pM (Kramer et al., 2011). Therefore, the coastal areas of the Bay of Bengal exhibited relatively high dissolved silver concentration.
The salinity of the surface seawater was found to be lower at shallower depths and decreased with river water inflow. This suggests that the elevated concentrations of dissolved silver in low-salinity waters suggests are likely attributable to the rivers discharging into the Bay of Bengal.
[Conclusions and Future plans]
We elucidated for the first time the behavior of dissolved silver in the coastal areas of the Bay of Bengal and the eastern Indian Ocean. Our data indicate that anthropogenic activities, coastal inputs, and environmental factors such as dissolved oxygen influenced the distribution of dissolved silver in the study region. We recommend future studies to focus on quantifying particulate silver in aerosols, marine sediments, seawater, and in surrounding river water to gain a better understanding of the sources and behavior of silver in seawater.
[References]
Tsiola, A., Pitta, P., Callol, A., Kalantzi, M., Mylona, K., Santi. I., Toncelli, C., Pergantis, S., Tsapakis, M., 2017. The impact of silver nanoparticles on marine plankton dynamics: Dependence on coating, size and concentration. Science of The Total Environment, 601-602, 1838-1848
Kramer, D., Cullen, J.T., Christian, J.R., Johnson, W.K., Pedersen, T.F., 2011, Silver in the subarctic northeast Pacific Ocean: Explaining the basin scale distribution of silver, Marine Chemistry, 123, 133-142
Wimmer, A., Urstoeger, A., Funck, N.C., Adler, F.P., Lenz, L., Doeblinger, M., Schuster, M., 2020. What happens to silver-based nanoparticles if they meet seawater?, Water Research, 171, 115399.