The main purpose of this study was to investigate whether meteorological parameters (temperature, relative humidity, direct radiation) play an important role in modifying the NO₂ concentration in an urban environment. The diurnal and seasonal variation recorded at a NO₂ traffic station was analyzed, based on data collected in situ in a Romanian city, Braila (45.26° N, 27.95° E), during 2009–2014. The NO₂ atmospheric content close to the ground had, in general, a summer minimum and a late autumn/winter maximum for most years. Two diurnal peaks were observed, regardless of the season, which were more evident during cold months. Traffic is an important contributor to the NO₂ atmospheric pollution during daytime hours. The variability of in situ measurements of NO₂ concentration compared relatively well with space-based observations of the NO₂ vertical column by the Ozone Monitoring Instrument (OMI) satellite for most of the period under scrutiny. Data for daytime and nighttime (when the traffic is reduced) were analyzed separately, in the attempt to isolate meteorological effects. Meteorological parameters are not fully independent and we used partial correlation analysis to check whether the relationships with one parameter may be induced by another. The correlation between NO₂ and temperature was not coherent. Relative humidity and solar radiation seemed to play a role in shaping the NO₂ concentration, regardless of the time of day, and these relationships were only partially interconnected.

Bathymetric measurements play an important role in assessing the sedimentation rate, deposition of pollutants, erosion rate, or monitoring of morphological changes in a river, lake, or accumulation basin. In order to create a coherent and continuous digital elevation model (DEM) of a river bed, various data interpolation methods are used, especially when single-beam bathymetric measurements do not cover the entire area and when there are areas which are not measured. Interpolation methods are based on numerical models applied to natural landscapes (e.g., meandering river) by taking into account various morphometric and morphologies and a wide range of scales. Obviously, each interpolation method, used in standard or customised form, yields different results. This study aims at testing four interpolation methods in order to determine the most appropriate method which will give an accurate description of the riverbed, based on single-beam bathymetric measurements. The four interpolation methods selected in the present research are: inverse distance weighting (IDW), radial basis function (RBF) with completely regularized spline (CRS) which uses deterministic interpolation, simple kriging (KRG) which is a geo-statistical method, and Topo to Raster (TopoR), a particular method specifically designed for creating continuous surfaces from various elevation points, contour, or polygon data, suitable for creating surfaces for hydrologic analysis. Digital elevation models (DEM’s) were statistically analyzed and precision and errors were evaluated. The single-beam bathymetric measurements were made on the Siret River, between 0 and 35 km. To check and validate the methods, the experiment was repeated for five randomly selected cross-sections in a 1500 m section of the river. The results were then compared with the data extracted from each elevation model generated with each of the four interpolation methods. Our results show that: 1) TopoR is the most accurate technique, and 2) the two deterministic methods give large errors in bank areas, for the entire river channel and for the particular cross-sections.

This study investigates the level of wastewater pollution by analyzing its chemical characteristics at five wastewater collectors. Samples are collected before they discharge into the Danube during a monitoring campaign of two weeks. Organic and inorganic compounds, heavy metals, and biogenic compounds have been analyzed using potentiometric and spectrophotometric methods. Experimental results show that the quality of wastewater varies from site to site and it greatly depends on the origin of the wastewater. Correlation analysis was used in order to identify possible relationships between concentrations of various analyzed parameters, which could be used in selecting the appropriate method for wastewater treatment to be implemented at wastewater plants.

Due to its complex role within the radiation budget of the Earth, cloud cover plays an important role in climate variability at local, regional or continental scale. Consequently, there is a need for better understanding the causes and feedbacks of changes in cloud cover. We aim at investigating the response of cloud cover to changes in atmospheric circulation for 1981–2014. This is done based on the application of automated weather type classification from COST733 synoptic classifications software, which helps in identifying a variety of atmospheric circulation types for selected domains. Two major spatial changes in cloud cover over Europe are identified, in connection with atmospheric circulation, associated with the latitudinal shift towards the north of the westerly circulation. The first one is related to a decrease of the cloud cover over the inner continent and especially in the East of Europe in connection with an increase of circulation types associated with high pressures centers development over the central and northern part of the continent. The second one, which is weaker in intensity, indicates an increase of cloud cover in the south‐western part of Europe as a result of a decrease in circulation types induced by the development of the Azores High and its northeastward ridges. The changes in cloud cover distribution and also in radiation fluxes, imposed by these shifts in atmospheric circulation over the continent, are higher in the Eastern and Central Europe.