Constructed wetlands as extensive treatment of diffuse pollution

Agriculture has been identified as a significant source of pollution of superficial and underground waters. The effects of the agricultural pollution are numerous and include: sediments contamination and deposition, pesticides residues, eutrophycation of superficial waters and degradation of down-stream rivers. These effects are caused by diffused pollution sources (NPS, Non-Point Sources ), that are considered as one of the major causes of the problems of the water bodies.

Applications in agriculture of fertilizers and pesticides have been dramatically increased starting from the mid 1960's, and the agro-chemical contamination of superficial and underground water has come to be a serious environmental problem. Nitrogenous compounds and pesticides represent the principal problem, due to the effects on human health and ecosystems, and to their wide utilization. It has to be noted that generally quite the 50% of nitrogenous fertilizers applied to the fields is lost in the drainage water, mostly in the form o nitrates NO3. Therefore, all these pollutants reach in great quantities the hydrographical network.

It is unlikely that these problems can be solved just by a management of the situation based on chemical treatments. Moreover, the diffuse character of the problem makes environmentally and economically unsuitable a conventional technological approach.

On the contrary, an approach based on extensive treatments realized by natural depuration techniques has proved itself to be efficient and able to promote the restoration of the agricultural ecosystem.

rom this perspective, the small dimensions of artificial wetlands (as order of magnitude, the requested surface is about the 5% of the surface of the served agricultural field) together with the high treatment power suggest that constructed wetlands can be scattered in the agricultural land, assuring the treatment of the diffuse pollution. In this way, they can also contribute to create a higher complexity of the agricultural ecosystem, in terms of landscape, biodiversity and habitats for the wild life. Considered that constructed wetlands can receive also eventual organic loads (for example connected to rain events), they can represent a powerful instrument with which the agriculture can even create benefits for the community: agriculture could actively participates in the improvement of the quality of water, in particular, and of the environment in general.