Pesticides: Behavior in Agricultural Soil and Plants.

This review considers potential approaches to solve an important problem concerning the impact of applied pesticides of various classes on living organisms, mainly agricultural crops used as food. We used the method of multi-residual determination of several pesticides in agricultural food products with its practical application for estimating pesticides in real products and in model experiments. The distribution of the pesticide between the components of the soil-plant system was studied with a pesticide of the sulfonylureas class, i.e., rimsulfuron. Autoradiography showed that rimsulfuron inhibits the development of plants considered as weeds. Cereals are less susceptible to the effects of pesticides such as acetamiprid, flumetsulam and florasulam, while the development of legume shoots was inhibited with subsequent plant death.

The effect of humic substances on metal migration at the border of sediment and water flow.

The speciation of radionuclides in bottom sediments of the Yenisei River, sampled in the near-field region of the nuclear fuel cycle enterprise, was studied. It has been established that most of 152Eu and 241Am radionuclides isolated by sequential chemical fractionation are in a bound state with the organic matter of bottom sediments (up to 35% of the total amount). In this case, the content of 152Eu and 241Am in depth of the bottom sediment layers is directly dependent on the change in the organic matter content. Bottom sediments containing a high content of organic substances (humic acids - HA and fulvic acids - FA) were studied. By the HA: FA ratio, the studied bottom sediments are related to a fulvate-humate type. When fractionating the organic matter of bottom sediments, it was revealed that the distribution occurred as follows (% of the total content): in the form of fulvates 152Eu - 53, 241Am-16, 60Co - 10, 137Cs-3; 241Am-28% associated with humin; in the form of organomineral compounds ~ 2-5%; in the form of organometallic complexes ~ 2-3%. Model experiments with addition of HA to the aqueous medium of the bottom sediments-water system. HA was previously isolated from bottom sediments and identified by IR Fourier spectroscopy. The introduction of HA significantly influenced the release of radionuclides and some metals from bottom sediments into the liquid medium. So, the content of 152Eu and 241Am radionuclides are intensively released into the water: from 0 to 198 ± 8 Bq·L-1 and 167 ± 7 Bq·L-1, respectively. The content of 4 K, 60Co, 137Cs was not considerable. The content of some analysed metals in the aqueous medium also increased significantly: 9 times for U6+ and 32 times for Cu2+.

Investigation of the tritium content in surface water, bottom sediments (zoobenthos), macrophytes, and fish in the mid-stream region of the Yenisei River (Siberia, Russia).

The potential sources of tritium input to the Yenisei River ecosystem are derived from local operations of nuclear facilities of the Mining and Chemical Combine operated by the state-owned Rosatom corporation and from sources derived from global weapons testing fallout and nuclear power. The background tritium concentrations in zoobenthos, bottom sediments, relevant commercial fish species, and widespread endogenous aquatic plants have been obtained for the first time in this region. Our results demonstrate that the major input term of tritium to this region of the Yenisei is derived from nearby mining operations of Rosatom, with tritium concentrations in aquatic plants marginally exceeding the observed background values obtained from upstream control sample collection sites.

The relationship of mineral and geochemical composition to artificial radionuclide partitioning in Yenisei river sediments downstream from Krasnoyarsk.

Discharges from the Mining-and-Chemical Combine (MCC) of Rosatom, downstream from Krasnoyarsk, resulted in radioactive contamination of sediments of the River Yenisei. The concentration of artificial gamma-emitting radionuclides ((137)Cs, (60)Co, (152)Eu, and (241)Am) was determined with the objective to analyze the migration processes leading to the transport of these radionuclides. The content of artificial radionuclides in the surface layers of the study area varied in wide ranges: (137)Cs-318-1,800 Bq/kg, (60)Co-87-720 Bq/kg, (152)Eu-12-287 Bq/kg and (241)Am-6-76 Bq/kg. There was a sequence of migration of radionuclides investigated in the surface layer of sediments that were collected in the near zone of influence of the MCC: (241)Am ≈ (152)Eu > (60)Co > (137)Cs. Radionuclide species have been found to be directly related to sediment structure and composition.

Effect of low-level alpha-radiation on bioluminescent assay systems of various complexity.

This study addresses the effects of low-level alpha-radiation on bioluminescent assay systems of different levels of organization: in vivo and in vitro. Three bioluminescent assay systems are used: intact bacteria, lyophilized bacteria, and bioluminescent system of coupled enzyme reactions. Solutions of 241Am(NO3)3 are used as a source of alpha-radiation. It has been shown that activation processes predominate in all the three bioluminescent assay systems subjected to short-term exposure (20-55 h) and inhibition processes in the systems subjected to longer-term exposure to radiation. It has been found that these effects are caused by the radiation component of 241Am3+ impact. The intensity of the 241Am3+ effect on the bioluminescent assay systems has been shown to depend on the 241Am3+ concentration, level of organization and integrity of the bioluminescent assay system. The bioluminescent assay systems in vivo have been found to be highly sensitive to 241Am3+ (up to 10(-17) M).