Comparação entre métodos de determinação de nitrato: coluna redutora de cádmio e teste nitraver® 5

Abstract

The widespread increase of nitrate (NO3-) levels in groundwater is a direct consequence of anthropogenic interventions in the nitrogen cycle. For determination of N-NO3- in waters and effluents, the Laboratório Físico-Químico da Superintendência Estadual do Meio Ambiente (SEMACE) makes use of the alternative Hach® 8171 methodology (Method A), through the NitraVer® 5 Test. This work aims to compare Method A with the Cadmium Reducing Column Method (B) found in Standard Methods for the Examination of Water and Wastewater. The N-NO3- + NO2- quantification, the average volume of residue generated, the average time of analysis, the costs with the reducing agent, common to both analyzes, and the Cd content eliminated were correlated. Groundwater samples from two wells located in the Metropolitan Region of Fortaleza were used: P1 (Caucaia) and P2 (Messejana). The results were associated with CONAMA Resolution 396/08, noting that the wells are contaminated by NO3-. The elemental Cd content in the residues was analyzed according to Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) technique and correlated with CONAMA Resolution 430/11, showing that both methods generate Cd in much higher levels than the Permitted Maximum Value (MPV).