Target

• to study the distribution of mercury and the mechanisms by which it is transpored.
• to develop a model capable of predicting the spread of pollution and simulating the effect of different interventions.
• to identify a set of economically feasible technical options and management strategies for damage limitation and for remediation of the polluted area.

Organization financing project: INTAS

Execution terms : February 1997   - January 1999 г.

Executors

• Kazakh State Academy of Architecture and Construction (KazGACA)
• Institute of New Chemical Technologies and Materials, Kazakh State National University of Al-Farabi
• Institute of Hydrogeology and Hydrophysics MS-HE
• Kaskelen Geophysical Observatory
• Institute of Microbiology and Virusology MS-HE
• Dept of Civil and Environmental Engineering, Southampton University, UK (Project Coordinator)
• Dipartimento di Ingegneria Civile, Universita degli Studi di Firenze, Italy, now at Dipartimento di Ingegneria Civile, Universita degli Studi di Trieste, Italy
• Institute of Mineralogy, Geochemistry and Crystallochemitry of Rare Elements (IMGRE), Moscow, Russian Federation

Earmarked resources: 208 000  ECU

Investigation results

• The riverbed between Samarkand and Intumak reservoirs contains significantly less pollution than first reported: about 550 000 cbm of silt and about 10 tonnes of Hg. Most of the silt and over 90% of the Hg is in the 25 km of the river immediately below Samarkand reservoir: approximately 80% of the contaminated material occurs in 10% of the river cross-sections. A further 160 000 cubic metre of silt and 4 tonnes of Hg is located in backwaters of the river, and 290 000 cbm of silt and 2 tonnes of Hg in oxbow lakes on the floodplain.

• The floodplain topsoil contains approximately 53 tonnes of Hg. Approximately 3% of the floodplain is in the hazardous category (more than 10 mg/kg of Hg in topsoil), equal to 5.8 sq. km or 880 000 cbm of material. About 70% of this is in the first 25 km.

• About 1 720 000 cbm of silt containing approximately 65 tonnes of Hg is deposited in layers up to 3 m thick on the floodplain. The majority of the contaminated material (approximately 80% of the silt and 90% of the mercury) is in the upper 25 km of the river.

• Local hotspots containing high concentrations of Hg occur in Swamp Zhaur (approx 1 sq. km, 50-100 tonnes), the old ash lagoon of KarGES-1 (approx 1 sq. km, 50-100 tonnes), the wastewater treatment works and the banks of the Main Drain from AO Karbide.

• Sediment transport modelling shows that in an average flood the reservoir will remove 20% of sediment, but if the spillway height is increased to its design height 70% will be removed.

• There does not appear to be a simple single parameter (eg. pH) which can be used to control the rate of Hg methylation in the river. The high pH of the water and sediments keeps the amount of Hg in the water column low. Most of the Hg in the water column is bound to the sediment and can be settled to remove Hg. Hg in the water column is only high in the flood season.

Contact
Sonia Heaven, Mikhail Ilyushenko, Tel: 20 18 44; Fax: 20 12 81; E-mail: enviro@ieem.almaty.kz