The influence of the Evros River on the recent sedimentation of the inner shelf of the NE Aegean Sea

Natural radioactivity of riverbank sediments of the Maritza and Tundja Rivers in Turkey

This article represents the first results of the natural radionuclides in the Maritza and Tundja river sediments, in the vicinity of Edirne city, Turkey. The aim of the article is to describe the natural radioactivity concentrations as a baseline for further studies and to obtain the distribution patterns of radioactivity in trans-boundary river sediments of the Maritza and Tundja, which are shared by Turkey, Bulgaria and Greece. Sediment samples were collected during the period of August 2007-April 2010. The riverbank sediment samples were analyzed firstly for their pH, organic matter content and soil texture. The gross alpha/beta and (238)U, (232)Th and (40)K activity concentrations were then investigated in the collected sediment samples. The mean and standard error of mean values of gross alpha and gross beta activity concentrations were found as 91 ± 11, 410 ± 69 Bq/kg and 86 ± 11, 583 ± 109 Bq/kg for the Maritza and Tundja river sediments, respectively. Moreover, the mean and standard error of mean values of (238)U, (232)Th and (40)K activity concentrations were determined as 219 ± 68, 128 ± 55, 298 ± 13 and as 186 ± 98, 121 ± 68, 222 ± 30 Bq/kg for the Maritza and Tundja River, respectively. Absorbed dose rates (D) and annual effective dose equivalent s have been calculated for each sampling point. The average value of adsorbed dose rate and effective dose equivalent were found as 191 and 169 nGy/h; 2 and 2 mSv/y for the Maritza and the Tundja river sediments, respectively.

Spatial and temporal distribution of pesticide residues in surface waters in northeastern Greece

A monitoring study of 147 compounds in surface river waters from northeastern Greece near Greek/Bulgarian/Turkish borders was carried out during 1999-2007. Based on agricultural use eight sampling points along the rivers Ardas, Evros and Erythropotamos were set up, covering the distance from the Greek/Bulgarian borders down to the river's discharge (river's delta) in the Greek territory. In total, 88 sampling events were carried out from 1999 to 2007. Pesticides were extracted by solid-phase extraction (SPE) and analyzed by gas chromatography-mass spectrometry (GC-EI-MS) using a multiresidue in-house analytical method including pesticides belonging to different chemical classes. Aquatic risk concerning the detected pesticides was assessed on the basis of the risk quotient (RQ = PEC/PNEC). From the 28 compounds (pesticides, metabolites and caffeine) that were detected in surface waters of northeastern Greece the soil applied pesticides were the most frequently detected. High pesticide concentrations were detected within 2 months of their application. Extreme pesticide concentrations were detected in the beginning of the irrigation season or just after high rainfall events. Generally, low levels of pesticide residues were found in the first sampling point (Greek/Bulgarian borders) of all rivers, however o',p' DDT, o',p' DDE and gamma-HCH were mainly detected in this sampling point regarded as cross-boundary contamination. The most commonly encountered compounds in the river waters were atrazine, DEA, alachlor, trifluralin, prometryne, molinate, carbofuran, carbaryl and diazinon. Increased loading (primary as well as secondary peaks) seemed to be a consequence of application (timing, rate, frequency) and intense rainfall during the application period. Aquatic risk assessment revealed that from the 28 compounds that were constantly detected 12 showed non-acceptable risk when median concentrations were used as PEC and 18 when extreme concentrations were used as PEC values.