Environmental monitoring model for a drainage basin obtained through spectral analysis of time series.

The quality of results of an environmental monitoring plan is limited to the weakest component, which could be the analytical approach or sampling method. Considering both the possibilities and the fragility that sampling methods offer, this environmental monitoring study focused on the uncertainties caused by the time component. Four time series of nutrient concentration at two sampling points (PB1 and PB2) in the Ribeirão Garcia basin in Blumenau, Brazil, which were significantly correlated to the spatial component, were considered with a 2-hour resolution to develop efficient sampling models. These models were based on the time at which there was the highest tendency toward adverse environmental effects. Fourier spectral analysis was used to evaluated the time series and resulted in two sampling models: (1) the SMCP (sampling model for critical period) that operated with 100% efficiency for registering the highest concentration of nutrients and was valid for 83% of the studied parameters; and (2) the SMGCP (sampling model for global critical period) that operated with 83 and 50% efficiency for PB1 and PB2, respectively.

Determinação do coeficiente de reaeração em rios através do uso do traçador gasoso GLP / Determination of stream reaeration coefficients by use of GLP gas tracer

A oxigenação da água constitui-se em importante fator no desenvolvimento do fenômeno de autodepuração de rios. A reposição do oxigênio dissolvido pode ser representada pelo coeficiente de reaeração (K2). Neste trabalho foi testado o uso do GLP como fonte do traçador gás propano em ensaios de reaeração. Foram executados 15 ensaios em trechos de rios com características hidrodinâmicas distintas. Os experimentos mostraram que a utilização do GLP como fonte do traçador gasoso é viável, tanto do ponto de vista analítico, quanto do ponto de vista econômico. Do ponto de vista analítico, os resultados foram equiparáveis e até superiores à técnica tradicional de traçador gasoso. Do ponto de vista econômico, houve redução do custo para a realização de cada ensaio.

The water oxygenation constitutes an important factor in the development of self-purification phenomenon in rivers. The replenishment of dissolved oxygen in water can be represented by the reaeration coefficient (K2). This work was used propane contained in the GLP as tracer in reaeration tests. The tests showed that the use of LPG is feasible, both from analytical point of view, as of the economic. From an analytical standpoint, the results were comparable and even superior to the traditional technique of tracer gas. From an economic standpoint, the cost to perform each test has been reduced.