Introduction

Global warming promotes the occurrence of cyanobacterial blooms in surface waters throughout the world [1]. Some climatic effects of global change include the variation in rainfall patterns [2], floods, droughts, dust storms [3], tropical storms, and intensity of hurricanes [4] which synergistically (along with nutrients) impact cyanobacterial and algal communities and bloom dynamics. Cyanobacteria often favor warm water and high light environments [5, 6]. Active growth occurs largely at temperatures above 20°C. Cyanobacteria also have been shown to be

R.A. Khaydarov (*), R.R. Khaydarov, and O. Gapurova Institute of Nuclear Physics, Tashkent, Uzbekistan e-mail: [email protected]

dominant in the warmer months in subtropical estuaries [7]. Many cyanobacteria are UV-tolerant since evolving various mechanisms to counteract UV radiation [8- 10].

The cyanobacterial blooms in fresh water are formed by cyanobacteria, such as

Microcystis aeruginosa, Anabaena circinalis, Anabaena flos-aquae, Aphanizomenon flos-aquae, Cylindrospermopsis raciborskii [11]. They are dangerous for the following listed below:

1. Dense cyanobacterial blooms can block sunlight and use up oxygen in water, killing other plants and animals.

2. Dense cyanobacterial blooms can disable water pumps. For example, in 2009 several Russian cities located near Tsimlyanskaya Reservoir on the Don River and Ijevskaya Reservoirs on Ij River lost drinking water because of clogged water pumps at water treatment stations.

3. Some cyanobacteria produce toxins that are among the most powerful natural poisons known [12-18]. For example, they produce neurotoxins (Anatoxin-a, Anatoxin-a(s), Saxitoxin, Neosaxitoxin) which affect the nervous system, hepatotoxins (Microcystins, Nodularins, Cylindrospermopsin) which affect the liver, tumor promoters (Microcystins) which can promote tumor growth, and Lipopolysaccharides which can affect the gastrointestinal system. Many of these toxins have no known antidotes. Cyanobacterial blooms can make people and animals sick. Children are at higher risk than adults for illness because they weigh less thereby receiving a larger comparative dose of the toxin.

These potential dangers underscore the importance of removing cyanobacteria from water. But this process should be conducted carefully because cyanobacteria account for 20-30% of the Earth's photosynthetic productivity and convert solar energy into biomass-stored chemical energy at the rate of ~450 TW. Cyanobacteria utilize the energy of sunlight to drive photosynthesis, a process where the energy of light is used to split water molecules into oxygen, protons, and electrons. While most of the high-energy electrons derived from water are utilized by the cyanobac-terial cells for their own needs, a fraction of these electrons are donated to the external environment through electrogenic activity. Cyanobacterial electrogenic activity is an important microbiological conduit of solar energy into the biosphere. Moreover, in some countries cyanobacteria is sold as food, notably Aphanizomenon flos-aquae and Arthrospira platensis [19].

Usually chemical and biological methods are used to control cyanobacteria in fresh water. These chemical methods adjust the balance between concentrations of phosphorus and nitrate in water, using peroxides, algicides and antibiotics like erythromycin to kill cyanobacteria. Unfortunately, these methods are expensive and cannot be used to control cyanobacteria in large water reservoirs. The biological methods are based on introducing a strain of chlorella into reservoirs, but they are not very efficient. This paper describes a new technology to control cyanobacteria in open water reservoirs using nanocarbon-metal compositions (NCMC).

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