Scientific bases for the development of water quality objectives in Spain. Ecotoxicological criteria

Abstract

Water Directive Framework (2000/60/CE) deals with the pollution caused by dangerous substances being discharged into the aquatic environment. In accordance with this directive, prevention and control of pollution may be enforced by means of limiting discharges or having water quality objectives (WQOs). The directive is a framework directive, which has to be followed by implementation directives in order to be effective. This study describes the methodology, based on the application of a deterministic model, for the development of WQOs. Following this procedure, national water quality criteria for 7 metals, 15 organic compounds, ammonia, nitrites and fluoride were developed. Finally, WQOs dependant of water hardness were established, between 1 and 10 micro g L-1 for Cu and Pb and between 10 and 100 micro g L-1 for Ni and Zn. Other WQOs of metals like Sn, Cr and Se ranged from 1 to 10 micro g L-1 taking into account the metal oxidation level. WQO for ammonia was established between 0.25 and 10 mg N L-1 depending on the pH. WQO dependant of chloride concentration was established for nitrites, finding a linear relation for waters with chloride concentrations higher than 10 mg L-1. For organic compounds, WQOs for several pesticides (atrazine, simazine, molinate, terbuthylazine and metolachor,