SHORT, MEDIUM AND LONG TERM STOCHASTIC ANALYSIS OF THE SUCEAVA RIVER POLLUTION EVOLUTION IN THE HOMONYMOUS CITY

The future evolution of climate and of its features, especially the exacerbation of extreme events, will have an important role in the dynamic evolution of river flow regime, in increasing the frequency of flood and low water periods. River flow regime influences the concentration of pollutants in water and can generate critical environmental situations. In this study, a statistical analysis of existing environmental data for Suceava city was conducted. It is a representative city for the postcommunist economic evolution in the central-eastern Europe; it continues having a strong impact on environment quality, in general, and on water, in particular. The recent evolution of Suceava River pollution in Suceava city is a complex phenomenon determined by hydrological characteristics, the climate, the economic evolution (before and after the global financial crisis), the effect of European measures to reduce pollution, the legislative measures and, last but not least, the building of a new treatment plants. Hydrological, meteorological and hydrochemical data were used for analyzing the future evolution of some parameters. The present pollution characteristics and the trend curves allowed estimating the probable evolution of the pollutants concentrations in future (with focus on the most likely times to reach maximum concentrations). Flow and rainfall characteristics are the most important control factors used in our forecasts. The probabilistic estimation of scenarios is based on various correlation coefficients between natural conditions and pollutants. We have different scenarios depending on mean the depending on the future time chosen and depending on the variants of future socioeconomic development. Chemical characteristics analyzed for Suceava River are pH, suspended solids, dissolved oxygen, BOD5, permanganate index, COD-Cr, ammonium, nitrite, nitrate, total nitrogen, orthophosphate, total phosphorus, fixed residue, sulfates, chlorides, total iron, detergents, phenols and in forecasting future evolution of the concentrations of previously mentioned parameters, their concentrations in the discharged wastewater from the treatment plant were also monitored. We also conducted a thermal field study of high temporal resolution on Suceava River correlated with the existing monthly time series and showing a clear thermal pollution of the river downstream from the city. The effects of forecasted oscillations of pollutants concentrations were analyzed both in terms of the water chemical quality classes and in terms of aquatic ecosystem quality. Biological effects of pollution are measured using phytobenthos and zoobenthos. The majority of scenarios predict a better water quality of Suceava River for all analysed parameters.