Abstract No : 343

Water quality management, water and sediment pollution, land based sources, hazardous wastes, algalblooms, bio- indicators of pollution and monitoring, pollution control

The Assessment Of Heavy Metals Biogeochemical Activity

Irina Radovanova (1), Natalya Popova (2) and Alexey Kurapov (1,3)(1) Caspian Marine Scientific Research Center, 414045 Astrakhan, Russia
Telephone: +7 8512 30 34 70 Email: irinaradov@mail.ru(2) Caspian Oil Company, Ltd., 414014 Astrakhan, Russia
Telephone: +7 8512 39 56 16 Email: popovaNV@caspoil.com(3) Telephone: +7 8512 30 34 70 Email: kaspmniz@mail.ru

The paper presents the results of assessment of biogeochemical activity of some heavy
metals in the shallow area of the North Caspian. The activity was estimated by means of
the method developed in KaspMNIZ. The method is based on comparison of the dynamicsof a pollutant substance (PS) with the dynamics of a conservative component dependentexclusively on the processes of water mixing. PS activity is revealed in deviation fromconservative behavior as it passes from water to other components of the marine
environment, including living organisms (biofiltration, biosorption processes, etc.). PS
activity was estimated by means of two non-dimensional indices: the index of activity
direction IFs and the index of activity level IFm. The first one characterizes the directionof PS transfer (depletion – enrichment) and the second one helps compare different
substances in their activity level. The research showed that in 2001-2009 the average
activity level of heavy metals in marine water varied insignificantly (IFm values areindicated in brackets): Cu, Pb (0.80) – Zn, Ni (0.78) – Cd (0.77). The activity of Cd and Cu
mainly revealed in water enrichment with these metals, while the activity of Pb, Ni andZn – in depletion. The analysis of seasonal variability revealed that there was a rise inactivity of Pb and Zn in spring and summer, and the rise in activity of Cu in autumn. The
activity of Cd и Ni didn’t depend on the season. Activity direction among the most of thestudied metals changed to the contrary with the change of the season. The changes ofaverage metal concentration in water almost did not have an impact on their activity.
Positive correlation was identified only for Ni in the warm period of the year. Metalactivity was also studied in different water types (differing in salinity level) of the North
Caspian Sea. It was revealed that in spring and summer the activity of Cd, Cu, and Ni in
the water with the salinity of 7-9‰ was higher than in fresh water (S<2‰); in autumn
the activity of these metals fell as water salinity increased to more than 9 ‰. Pb activity
rose significantly in fresh water, especially throughout spring period. The level of Zn
activity almost didn’t change. The analysis of activity direction showed that while the 2‰
salinity threshold was reached the activity sign of the most of the studied metals changed
to the contrary. One of characteristic features is that Cd, Cu and Zn mainly deposit from
fresh water, Pb – under salinity of more than 2‰, and Ni – under the salinity of morethan 7‰. The results of assessment of pollutants biogeochemical activity are accounted

for in the description of environmental situation in the North Caspian, as the process ofwater self-purification with living organisms can lead to either positive (PSbiodegradation) or negative (PS bioaccumulation) consequences. Keywords:
biogeochemical activity, heavy metals, North Caspian