næringsavløp

Næringsavløp, or nutrient runoff, refers to the flow of excess nutrients, primarily nitrogen and phosphorus, from agricultural lands and other sources into waterways. This process occurs when fertilizers, animal waste, and other nutrient-rich materials are applied to the land and subsequently washed into rivers, lakes, and coastal waters by rain or irrigation. The nutrients are not fully absorbed by crops or vegetation and are instead transported across the surface or leached through the soil.

The primary consequence ofnæringsavløp is eutrophication, a process where excessive nutrient enrichment leads to an overgrowth of algae and aquatic plants. This algal bloom can deplete dissolved oxygen in the water when the algae decompose, creating hypoxic or anoxic conditions that are harmful or fatal to fish and other aquatic organisms. These "dead zones" can significantly impact aquatic ecosystems and fisheries.

Sources of næringsavløp are diverse and include large-scale agriculture, urban stormwater runoff, septic system leakage, and industrial discharges. Agricultural practices, such as the overuse of synthetic fertilizers and manure, are often significant contributors. Urban areas contribute nutrients from lawn fertilizers, pet waste, and wastewater treatment plant effluent.

Mitigation strategies aim to reduce the amount of nutrients entering waterways. These can include improved agricultural practices like cover cropping, reduced fertilizer application, buffer strips along waterways, and better manure management. In urban areas, measures such as green infrastructure, public education campaigns about responsible lawn care, and improved stormwater management are employed.