Increase in colour and amount of organic matter in surface waters

Sammendrag

Some regions of the world are blessed with ample amounts of fresh surface water, but its dissolved Natural Organic Matter (NOM) often poses a serious concern for waterworks. Increases in NOM have largely been responsible for the unprecedented increases inwater colour over the last 10-15 years that have been reported in the Nordic countries, the foothills of central Europe, Northern UK and North-eastern US. This increase has poised the water industry to spend hundreds of millions of Euro to deal with the problem. Furthermore, NOM is the single most important biogeochemical factor in the aquatic ecosystems of the northern hemisphere. A multidisciplinary Workshop was held in the Rondane National Park, in the heart of Norway, on the 22 & 23 May, 2003. The objective of the assembly was to bring together leading scientist from various fields of research but all involved in the study of causes and consequences of the changes in quality and quantity of NOM. The Workshop arrived at the following views and recommendations: Changes in the amount and properties of NOM are expected to be the most important ways by which climate change will influence aquatic biota. Moreover, many other social pressures that are altering NOM amount and quality are changing at an even greater pace than climate change (e.g. acid rain and land-use). Since changes are going to occur, the challenge is how to manage those changes such that society can achieve its environmental goals. Due to pending investments, the most pressing challenge is to secure clean drinking water,. What future investments in drinking water treatment are required and what NOM removal technology should be applied are important questions that need to be answered in order to maintain sustainable management of aquatic ecosystem services. To answer these questions we need to understand the processes controlling NOM cycling. NOM cycling is a fundamental feature of ecosystems and a scientific area of great complexity, but also an area of active research. We already know enough to say that the amount, quality and intensity of precipitation is the main driving force of the observed changes in NOM and that the anthropogenic factors, such as climate change (e.g. changes in seasonality of temperature, precipitation), reduced acid rain and land-use changes (e.g. more forests, decreasing drainage), superimpose on the natural variation. The management of water resources under a regime of changing NOM requires knowledge and understanding about the links between the environmental changes and their impacts, and society�s responses to them (i.e. DSPIR (Driving Force; Pressure; State; Impact; Response) framework)). It is therefore of urgent importance to separate the precipitation-runoff effects from the effects of other potential factors as some of these factors are changing dramatically. NOM is a complex substance, and its significance has been widely recognized by the scientific community only relatively recently. Our knowledge of the causes and consequences of a change in the NOM cycling is therefore deficient. Unless the importance of NOM for society is acknowledged and its research is included in national/international agenda, the science will not make the contribution it could and should.