The paper presents an analysis of water pollution carried out on the basis of the combined physico-chemical Serbian Water Quality Index (WQI) in the Timok River basin. The analysis covers various parameters (oxygen saturation, Five-Day Biochemical Oxygen Demand or BOD 5 , ammonium ion concentration, pH value, Water Total Nitrogen or WTN, Total Suspended Solids or TSS, orthophosphate concentration, electrical conductivity, temperature and the fecal coliform bacteria parameter) the values of which were calculated for four hydrological stations within the basin. The data obtained at each measurement station were averaged using the annual arithmetic average mean. The annual WQI values were calculated for a twenty-five year period (1990-2014) and they were in the range between 12 and 92, which means that the quality of water varied, ranging from "very bad" to "excellent". The obtained results were interpreted and the watercourse quality was assessed using the comparison of water quality indicators according to the Serbian Classification of Surface Waters and the WQI method. The worst water quality was recorded in the Borska Reka River. Certain SWQI values are the result of water quality changes caused by wastewater from human settlements, industrial facilities, agricultural sources and illegal waste disposal sites in the basin.

Internal migration is an essential part of regional population change. Driven by various determinants, internal migration has been unequal across time and space. Migration responses to the changes in societal circumstances make it relevant to investigate the spatial and temporal dimension of internal migration in Serbia before and in the aftermath of the COVID-19 pandemic outbreak. The research aims to identify to what extent and in what way the pandemic has changed the magnitude and geographical patterns of internal migration in Serbia. The study is based on additionally processed official statistics on internal migration for the period 2018-2020, from March to December for each year, at the municipal, district (oblast, plural-oblasti), and regional levels. These are aggregate administrative data on usual residence registration by month. The derived data on the net migration rate is cartographically presented using the classification method natural Breaks (Jenks). Spatial dependence was assessed applying the spatial autocorrelation method, based on the Local Moran statistic. The results revealed that the pandemic affected not only the volume of internal migration but also its spatial patterns. The findings present new insights on the role of internal migration in reallocation of population across Serbia before and during the COVID-19 pandemic while underlying the importance of further research to deepen the understanding of internal migration trends upon the COVID-19 outbreak.

Socioeconomic data of the villages belonging to the municipality Vladičin Han were analyzed in the paper. This municipality is part of Pčinjski district and is located in southeastern Serbia. The villages have typical rural character and are located in mountain area, except Priboj, which is dislocated in the 19th century. The lowest is Priboj (350-460 m) and the highest one is Kukavica (1,170-1,230 m). The subject of this paper is also the settlements of Lebet, Rdovo and Kostomlatica. The data obtained are the result of processing database retrieved from the Statistical Office of the Republic of Serbia, related to the period 1971-2011. At the beginning of this period, the village with the largest population was Priboj (359 inhabitants). According to the last census (in year 2011), there lived 296 inhabitants with average age of 44. The settlement with the smallest population, according to the latest census, is Kostomlatica village. There live 10 inhabitants with an average age of 76.3 years. Other demographic indicators point to the extinction of the villages in this region. Depopulation is the problem to which state does not pay enough attention, especially in mountainous and border areas.

The Spanish flu appeared at the end of the First World War and spread around the world in three waves: spring-summer in 1918, which was mild; autumn fatal wave, in the same year; and winter wave in 1919, which also had great consequences. From the United States of America, as the cradle of its origin, the Spanish flu spread to all the inhabited continents, and it did not bypass Serbia either. Research on the Spanish flu, as the deadliest and most widespread pandemic in the human history, was mostly based on statistical researches. The development of the geographic information systems and spatial analyses has enabled the implementation of the information of location in existing researches, allowing the identification of the spatial patterns of infectious diseases. The subject of this paper is the spatial patterns of the share of deaths from the Spanish flu in the total population in Valjevo Srez (in Western Serbia), at the settlement level, and their determination by the geographical characteristics of the studied area-the average altitude and the distance of the settlement from the center of the Srez. This paper adopted hot spot analysis, based on Gi* statistic, and the results indicated pronounced spatial disparities (spatial grouping of values), for all the studied parameters. The conclusions derived from the studying of historical spatial patterns of infectious diseases and mortality can be applied as a platform for defining measures in the case of an epidemic outbreak with similar characteristics.

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