We all depend on clean water – for drinking water and for recreational uses such as visits to streams, lakes and the sea. Unfortunately, the water is not always clean. Every day water is exposed to a wide range of substances due to human activity in general and industrial and agricultural production in particular. Consequently, to conserve clean water and maintain a healthy and captivating nature we need to become better at limiting and controlling our use of water and limit any emissions of substances including, among others, organic matter, nitrogen, phosphorus and pesticides. Today, one of the major global threats to nature and the environment is nutrient pollution which causes high nutrient loadings to the aquatic environment and excessive algae growth in surface waters.
Urban sewage treatment plants and the agricultural sector are the primary sources of organic matter, nutrients, pesticides, etc. in our aquatic environment. From approx. 65,000 km of watercourses, water flows from land areas into the sea. It stems from surplus rain, which seeps down through the soil into the groundwater. This primarily occurs in winter when evaporation is limited. While travelling downwards through the soil, the water is contaminated by various substances including nitrate, phosphate, pesticides, soil particles and other xenobiotic compounds. The amount of matter which is transported with rain water down through the soil primarily depends on how the area in question is currently used and how it has been used in the past, and on the soil’s textural composition. On their way through the soil, nutrients and xenobiotic compounds can shift from one phase to another owing to biogeochemical processes. For example, bacteria can reduce nitrate to free gaseous nitrogen through denitrification. Water from the soil can also run directly into a stream or lake as superficial run-off owing to heavy precipitation, or through underground drainage pipes which farmers have laid down in more than 50 per cent of the fields to ensure that they can drain and hence cultivate their land efficiently.
We have also participated in the development of the national nitrogen model under the project ”Oplandsmodel til belastning og virkemidler” initiated by the Danish Nature Agency, the Danish AgriFish Agency and the Danish Environmental Protection Agency. The model describes the total nitrogen transport and turnover from field to coast by coupling the sub-models developed specifically for, respectively, the root zone, groundwater and surface water at AU and GEUS. The project was completed in autumn 2015.
Specifically we are involved in the ongoing monitoring of agro-ecosystems, farmers handling of nutrients and the transport and fate of nutrients in five small catchments. Furthermore, we are responsible for the annual quality assurance and annual reporting of results from the hydrometric and water quality monitoring at several hundred stream gauging stations and the calculation of the emission and sources of nutrients to the Danish coastal waters. Climate plays an important role in the emission of nutrients and therefore we also conduct research into the impact of climate change on the water and nutrient cycle and other biogeochemical cycles. Finally, we conduct research into the effects of new mitigation strategies on how to reduce greenhouse gas emissions and the loss of carbon and nutrients to the aquatic environment. In years to come, mitigation measures such as bufferzones, wetlands, catch crops, and controlled drainage will be used as the Water Framework Directive is being implemented. Last but not least we educate new biologists within the field.