Nous proposons un modèle à générations imbriquées dans lequel les émissions polluantes des firmes sont régulées par un système de permis de pollution. Le quota global d'émission est imposé à l'économie et s'accompagne de contraintes politiques quant à son utilisation. Dans ce contexte, la question se pose de savoir si la régulation de la pollution par les permis et la réalisation de l'optimum de premier rang sont compatibles. Nous montrons que quand la politique est contrainte, il est possible d'établir l'optimalité de l'équilibre grâce à une politique de redistribution de la rente environnementale et à une politique de discrimination par les prix des intervenants (firmes et ménages) sur le marché des permis.

This paper presents the results of investigation on photosynthetic pigments, chlorophyll a in the river Danube (Serbia) during 2002-2005. Field investigations were carried out with seasonal dynamics on the river strech between 1112 and 851 km. Exceptionally in September, during low water period, investigations were carried out on the river strech between km 1260 - 851, including the main tributaries: Tisza, Sava, Velika Morava and Pek. The concentrations of chlorophyll a and phaeophytin a were determined using the standard ISO 10260/92 methodology, variant B. Pigment extraction was done in hot ethanol immediately after sampling, on board of a research ship. The results revealed seasonal concentration dynamics of the mentioned indicators of primary productivity and physiological status of the algae community where fall of chlorophyll a from the upstream towards downstream profiles was evidenced.

Recent surveys of river Tisza (Serbia) have shown that class Oligochaeta is commonly present as dominant member of benthic macroinvertebrate community. Knowing the fact that this class is very good indicator of organic upload in aquatic ecosystem, in this paper it is used for saprobiological water quality assessment of middle and lower stream of river Tisza in summer of 2002, 2004 and 2005. Results presented as saprobiological indices, showed that water quality of river Tisza (Serbia) was alfa-mesosaprobioc (the third class) during research period.

The paper considers legal framework for the surface waters quality control as per our Regulation and Directive 75/440/EEC in terms of required quality of surface waters intended to be used for the drinking water production. Research has been done in eight accumulations designed for water supply in Serbia, and water quality index has been determined using WQI method during the period 2000-2004. The water quality in these accumulations was within the treshold values in relation to the required quality.

Microbiological and saprobiological characteristics of river Moraca and Skadar lake for period of 2004/2005 are done at localities: Pernica, Moraca estuary and Vranjina (Skadar Lake). The objective of the research is to establish quality of water of these aquatic ecosystems based on microbiological and saprobiological analyses, as well as, to show need for protection of these water ecosystems from permanent contaminations, mainly by sewage should be pointed out. Saprobiological index is determined based on Gulyas Pal, and Pantle Buck is used to determine saprobiological level.

The puddles Slatina and Pecena Slatina are the old meanders of the river Tamis. These ecosystems are periodicity fill with moderate salt and high alkaline water. The paper gives a review of qualitative and quantitative analysis of the algal compositions. Cyanoprokaryota and Euglenophyta are more common. All investigated parameters like compositions of lagal communities, their abundace, biomass and chlorphyll-a showed a high level of nature eutriphication in these ecosystems.

One of the key issues related to the water quality in the Iron Gate reservoir is the pollution of the sediment. Sediment deposits retained in the Iron Gate reservoir originate from a wide river basin with more then 80 million inhabitants and highly developed municipal and industrial infrastructure. Besides mineral river sediment, various organic and inorganic matters entered and deposited within the Iron Gate reservoir. Sediment research objective was to assess the content of contaminants and nutrients which potentially could enter the water column.

During spring of 2005, referent monitoring of the chemical quality of surface waters and sediments in some protected areas in Vojvodina (Serbia) was conducted as a supplement to the Regular monitoring program. The aim of the study was to establish the chemical quality of surface waters and sediments regarding nutrient content. It is shown that the water quality satisfies the criteria of the 1st/2nd class according to our legislation, with the exception of the Ludos location, which showed a contamination with nitrogen matter in water and sediments. With regard to the contamination of water with phosphorus, almost all locations may be considered as potentially problematic.

The objective of this paper is establishing eco-chemical characterization of the Skadar lake (i.e. Lake Scutari) system by investigation of heavy metal content and distribution in the lake sediments. Factors that influence heavy metal concentrations in sediments are allochthonous (natural and human effects) and autochthonous (natural processes of settling and sorption) as well as transformation of settled substances in sediments. Sediments samples were taken from 15 sites and analysed for copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb).

During the study we recorded narrow margins between zooplankton distribution and the ecological characteristics of water in Bokakotorska Bay (Adriatic sea, Montenegro). Various species show different vulnerability to environment quality. Some are defined as indicators, with low tolerance for the ecological variation of environment, and their distribution is limited to the particular type of water masses within the sea. The limiting factors are different for various species, and their indicator status is determined by their distribution. The indicator type, based on monitoring of particular species, may define a biotope, with the help of statistical analyses that identify the main time and spacial behavior patterns of a species, and my allow future ecosystem changes to be anticipated. In this paper we paid particular attention to the indicator species Oithona nana (Giesbrecht).