Valentinas Šaulys

Determination of Organic Matter by UV Absorption in the Ground Water

Abstract Organic matter in drinking water is determined by applying indirect determination methods used for quantitative measurements such as total organic carbon (TOC), chemical oxygen demand (COD), and biochemical oxygen demand (BOD). These analyses require expensive devices, harmful chemical reagents, and are time consuming. Standard water quality tests are inconvenient during start-up or reconstruction of drinking water treatment plants as samples need to be transported to a laboratory and no on-line measurements on plant performing efficiency are available. For practical purposes, less sophisticated and faster methods to determine organic matter are required. One of the methods could be ultraviolet absorption of water at 254 nm wavelength (UV254). It is a technically simple and fast method for determining natural organic matter, requiring neither expensive measurement equipment nor chemical reagents. The present article aims at investigating the possibilities of practical applications of UV254 method...

Patterns of River Runoff Change Considering the Size of the Basin

Abstract Climatic change and fluctuations of river runoff are among the most urgent topics nowadays. It is important to analyse and establish tendencies for forecasting. The article deals with the reasons of runoff variation trends, i.e. river basins with different physical-geographical and meteorological conditions are analysed. In the research, statistical Mann-Kendall test and correlation coefficients were applied to assess the influence of precipitation amount variation on the variation of river discharges. The achieved results showed that the correlation links between a major river outflow (Neris) and precipitation were established only during autumn and winter seasons, however, the links were very weak (correlation coefficient of 0.4). The correlation between major river runoff and precipitation is also weak but can be observed during summer season as well. The highest correlation coefficients were established in rivers of average size. This proves that the smaller the river, the stronger is the rea...