River water quality assessment: comparison between old and new indices in a real scenario from Italy

ABSTRACT

According to the European Water Framework Directive, Italy introduced two aggregate indices for evaluating the ecological status of rivers, called respectively LIM (Pollution Level of the Macro-descriptors) from 2000 to 2008, and LIM_eco from 2010 onwards. The LIM index considered the % of Dissolved Oxygen (DO%), ammonium nitrogen (NH₄-N), nitrate nitrogen (NO₃-N), total phosphorus (P), Biochemical Oxygen Demand (BOD₅), Chemical Oxygen Demand (COD), and Escherichia (E.) coli, while LIM_eco considered only DO%, NH₄-N, NO₃-N, and total P. The aim of this study was to evaluate differences between LIM and LIM_eco for defining quality status of freshwaters. For this purpose, data obtained during an annual monitoring campaign of four main rivers of southern Italy were used to calculate both indices. LIM_eco seems to return the quality status of a river better than LIM when the state of the water body is more compromised, while there is a substantial consistency when the river quality is at a medium/high level. Indeed, LIM intended to give a ‘traditional’ classification of freshwaters, integrating environmental and ecological descriptors, while LIM_eco focuses on the trophic status of freshwaters, considering only nutrients and oxygen, essential for the aquatic biological communities and it does not consider organic load and microbiological contamination.

Keywords:

• Freshwater quality
• European Water Framework Directive
• ecological assessment
• freshwater ecological indices