This work aims to identify the sources of nitrogencontamination in nitrate vulnerable zones (NVZs) of Spain by means of the nitrogen isotope method. Three categories of nitrogen sources (synthetic fertilisers, animal wastes, and sludges and effluents from waste-water treatment plants) from three NVZs were analysed for their nitrogen isotopic composition (δ¹⁵N) in order to assess the applicability of the method to the identification of these N sources. The mean δ¹⁵N values were: +1.48‰ for synthetic fertilisers, +15.98‰ for animal wastes and +11.52‰ for sludges and effluents. The synthetic fertiliser sources were significantly different from the organic sources and so, the method can be used for their identification. The highest variability was found within the animal waste category. The range of values found for the different kinds of animal wastes (+5.86 to +36.74) was very wide and overlappedthe range found for sludges and effluents from waste-water treatmentplants (+4.57 to +20.18). Accordingly, these two nitrogen sources areisotopically indistinguishable.

The paper presents the results of investigation of benthic algae of the river Rasina. During April, 2001, it was determined 110 algal taxa from the divisions Cyanophyta, Bacillariophyta and Chlorophyta, which indicate the high biodiversity of algae in this river. With 97 algal taxa, Bacillariophyta is dominant. The community of benthic algae is typical for this kind of aquatic ecosystem during the spring period. Great number of algal bioindicators of highly polluted water indicates the presence of high concentration of organic compounds in this aquatic ecosystem.

Investigations of phytoplankton in the Montenegrin coastal sea through summer (June, July, August) 2003 are described in this paper. They represent continuation from the previous years, and especially from 2001 and 2002. Maximum microphytoplankton quantity is found in the area of the bay (Kotor Bay) during June 3.9 x 10**6 cell/cubic dm, with the dominance of Nitzschia delicatissima (99%). This species was found with high percentage (more than 50%) during July and August, too. Leptocylindrus minimus and Skeletonema costatum, which were dominant in the previous period, through this year were slightly presented. In the area outside the Bay of Boka Kotorska, microphytoplankton was presented with quantities cell between 10**3 and 10**5 cell/cubic dm. Mean values of microphytoplankton in the area of the Boka Kotorska Bay were in 2003 year 4.6 times higher than outside the Bay. The same ratio was found for nanophytoplankton, too.

In this paper are represented the results of the pollution character of soils and water during the 2002. Taking into consideration the changes of analyzed parameters in during the analyzed period, there have been noticed strong periodical pollutions by organic substances, nutrients and industrial polluters with the growing tendency regarding frequency which make worse the quality of soil-water the drainage basin of the river Tara, unique in Europe is proposed. That is the reason why the monitoring of the mentioned potential, with support of the space informatics technology as the prerequisite of its management.

During 2003 the referent monitoring of chemical quality of surface waters and sediments in Vojvodina (Serbia, Serbia and Montenegro) was conducted as a supplement to the regular monitoring program in Vojvodina. The aim of the study was to establish the chemical quality of surface waters and sediments. It is concluded that the water quality satisfies the criteria of the 1st/2nd class according to our legislation, with the exception of a few monitoring stations which showed a slight contamination with mineral oils and polycyclic aromatic hydrocarbons (PAHs)/ With regard to contamination of sediments with PAHs, organochlorine pesticides and polychlorinated biphenyls (PCBs) the Begej-Klek monitoring station may be considered as potentially problematic as the reference values according to Dutch legislation were exceeded for three classes of pollutants.

This paper presents general characteristics of water source Mareza, which has been used for water supply of the town of Podgorica, as well as potential risks that can affect water quality of this source. Measures for the source protection in order to maintain existing high quality of the source water are presented.