The work is devoted to the consideration of the peculiarities of the impact of manganese (II) on representatives of freshwater biota. Manganese plays an important role in the aquatic environment, since it determines the course of the most important metabolic processes in hydrobiont organisms of varying degrees of organization. The analysis of processes involving manganese has shown that the main chemical factors affecting the accumulation of manganese in the aquatic environment are anaerobic biochemical processes caused by active silting of the riverbed due to the washout of organic substances from agricultural fields. The use of various physiological endpoints in daphnids is considered as an inexpensive and simple alternative, the criterion of which corresponds to the rule “replacement, reduction, refinement”. It has been shown that manganese (II) ions in the concentration range of 0.1-1000 LOCvr do not have an acute toxic effect on D. magna crustaceans, chronic toxicity is manifested in samples with concentrations of more than 10 LOCvr. The acute toxicity of solutions of manganese (II) salts in relation to S. Quadricauda was revealed by the change in the fluorescence level of microalgae at a concentration of Mn2+ from 0.05 mg/l.

Introduction. The relevance of the work for preventive medicine is due to the need to assess the impact of climate aridity on the hygienic safety of drinking water. The aim of the work is to determine the influence of the degree of aridity of the arid regions of Russia on the hygienic safety of drinking water prepared from surface water sources. Materials and methods. The objects of the study are the water of small rivers located in the arid regions of the Saratov Region and the Republic of Bashkortostan. The content of pollutants in water was determined by atomic absorption spectrometry, spectrophotometry, and potentiometry. Satellite images for the implementation of remote sensing of the Earth are obtained in the geoinformation catalogue earthexplorer.usgs.gov. Image processing and mapping of the studied territories was carried out using the QGIS program, version 3.12.3. Results. Using the method of remote sensing of the Earth, it was revealed for the first time that the low-arid regions of the Republic of Bashkortostan correspond to positive NDMI values. In contrast, the areas of the Saratov region are characterized by negative NDMI values. For the first time, a statistically significant correlation has been established between the hygienic hazard caused by polluting chemicals in water, typical for arid territories and the change in the aridity index NDMI. Biogenic nitrogen, iron, and manganese make the most significant contribution to the formation of the non-carcinogenic danger of small river waters in the conditions of climate warming. Conclusion. We have shown for the first time using the remote sensing method of the Earth that low-arid regions of the Republic of Bashkortostan correspond to low positive values of the aridity index NDMI than for the areas of the Saratov region characterized by negative NDMI values. For the first time, a correlation was established between an increase in the degree of aridity of arid areas of Russia and an increase in non-carcinogenic health risk due to the use of drinking water prepared from surface water sources.

Introduction. Chemical factors affect the emergence of carcinogenic and non-carcinogenic health risks when drinking water consumed in the arid regions of Russia and the world. Material and methods. The objects of the study are samples of water springs located in the city of Saratov. Methods of atomic-absorption spectrometry, spectrophotometry, and potentiometry were used to determine contaminants’ content in water of springs. The health and hygiene safety of spring water was assessed by calculating carcinogenic and non-carcinogenic risk, hazard level, and total hazard level. Results. The unacceptable level of non-carcinogenic risk (HI>1) was established to refer to the development of pathologies of the cardiovascular system and liver and the gastrointestinal tract, kidneys, skin, endocrine system. Nitrates are the greatest contributor to the formation of non-carcinogenic hazards of spring water from the sources studied. Discussion. The processes of rotting plant matter, agricultural activities, and exchange between water and underlying aquifer caused the exceeding of the admissible health risk of water springs located at higher elevations was mainly due to. The highest frequency and magnitude of excess non-carcinogenic sanitary and chemical indices are most often characteristic of springs at the highest elevations or located in the zone of active agricultural activity. The Ni2+ ion, with the highest amount of the total carcinogenic risk caused the carcinogenic effect mainly. It corresponds to springs located on the slopes near the freeways. Conclusion. Nitrates, nickel, cadmium, and iron, made the most significant contribution to the risk of non-carcinogenic exposure in drinking water from the studied springs have. The presence of nickel had a more pronounced carcinogenic effect. Toxic non-carcinogenic water action is directed mainly at the cardiovascular system and liver. The use of water from the springs studied decreases with the increase in the height of the source above sea level caused the probability of non-carcinogenic and carcinogenic effects. The exchange processes with the underlying aquifer of carbonate rocks, as well as the life of iron-healing bacteria during floods and rains, can explain the effect of the arid climate on the distribution of carcinogenic and non-carcinogenic risks in the spring water of Saratov.

The work is devoted to establishing the influence of aridity on the risk of negative soil changes caused by residual pesticides presence in spring and autumn. Using the Earth’s remote sensing method, it is shown that the NDMI index is decreasing and aridity is increasing in the following direction: Lipetsk Oblast- Kursk Oblast - Voronezh Oblast-Belgorod Oblast-Ulyanovsk Oblast -Samara Oblast -Saratov Oblast - Penza Oblast -Orenburg Oblast --Stavropol Krai-Karachay-Cherkessia. Correspondence was established between the increase in region’s aridity and the increase in the risk increment value for the period from spring to autumn due to the presence of residual pesticide content in the soil. This circumstance can be associated with pesticides accumulation in the soil cover, an increase in their consumption and a decrease in destruction in conditions of arid climate. DDT and hexachlorocyclohexane cause the highest risk increment due to soil accumulation, trifluraline is more subjected to conversion in the soil, has less effect on risk change of soil agroecological condition.