Dinâmica de nitrogênio e fósforo em reservatório na região semiárida utilizando balanço de massa

Abstract

R E S U M OMuitos reservatórios são alvo de impactos resultantes de diversas atividades antrópicas, principalmente os localizados nos domínios das bacias metropolitanas. O açude Gavião, responsável pelo abastecimento de água potável da Região Metropolitana de Fortaleza, apresenta a presença excessiva de fitoplâncton, consequência direta do enriquecimento da água por nutrientes, dificultando substancialmente o tratamento da água no reservatório e elevando os custos de tratamento. Torna-se imprescindível, portanto, estudos, planos de gerenciamento, ações corretivas e/ou preventivas a fim de que, futuramente, a qualidade das águas não seja prejudicada a ponto de culminar na necessidade da modificação da tecnologia de tratamento utilizada na estação. A determinação da carga de nutrientes e os balanços de massa podem avaliar o processo de eutrofização no sistema verificando-se se há exportação ou retenção de nutrientes no corpo d'água. Amostras mensais de janeiro a maio de 2011 foram coletadas em cinco pontos do açude com o objetivo de estudar o balanço de massa dos macronutrientes. No período de estudo o açude acumulou cerca de 28,06 t de fósforo e 121,42 t de nitrogênio podendo ser classificado eutrófico.Dynamics of nitrogen and phosphorus in reservoir in the semi-arid region using mass balance A B S T R A C TMany reservoirs are subjected to impacts resulting from various anthropogenic activities, especially those located in metropolitan areas of the basins. The reservoir Gavião is responsible for drinking water supply in the Metropolitan Region of Fortaleza and contains excessive presence of algae, a direct result of the enrichment of water by nutrients, which substantially hampers the treatment of water collected in the reservoir and increase the treatment costs. Therefore, it is essential to carry out studies of corrective and/or preventative management plans so that future water quality is not impaired to the point that it culminates with the replacement or modification of the technology used in the treatment plant. The determination of nutrient loading and mass balances can evaluate the eutrophication process in the system, checking for export or retention of nutrients in the water body. Samples were collected monthly from January to May 2011, at five points in the reservoir in order to study the mass balance of macronutrients. During the study period the reservoir accumulated approximately 28.06 t of phosphorus and 121.42 t of nitrogen, and can be classified as eutrophic.Dinâmica de nitrogênio e fósforo em reservatório na região semiárida utilizando balanço de massa

Loss of Water and Nutrients in Different Soil Tillage Systems Subjected to Natural Rainfall in the State of Mato Grosso, Brazil

“…High concentrations of nutrients-especially nitrogen (N)-in the water can cause damage to the environment and to human and animal health. Phosphorus (P) and N are essential elements for triggering the eutrophication of water resources; however, P is considered to be the limiting element because N can be supplied via the fixation of atmospheric N by some aquatic plants (Vidal & Capelo Neto, 2014). In addition to eutrophication, N may also cause human health problems Engenharia Agrícola, Jaboticabal, v.38, n.6, p.864-873, nov./dec.…”

Chemical Changes of Soil and Water in Hillside Areas Under Intensive Horticulture

“…Water from R6 is not shown in the graph since it has a larger scale, presenting higher values for NO3 − , ranging from 4.72 to 4.97 mg L −1 and with no direct relation with the precipitation of the same period. Considering that nitrate is very soluble in water and poorly adsorbed by soil (Vidal & Neto, 2014), these results indicate that nitrate have been leached in the soil, slowly and continuously contaminating the water table over several years of infiltration since water volume in R6 is high, but variations did not respond immediately to the precipitation of the same year. The low water volumes of reservoirs and increases followed by rainy periods reveal that a small part of the nitrate from hillside soils may be being carried to dams by topsoil erosion.…”

“…An increase in precipitation reduced P concentration both in water reservoirs and in R6, but the inverse was observed for NO3 − concentration. Considering that P is slightly mobile in the soil (Paula et al, 2016) and that organic matter mineralization does not cause water eutrophication in these environments even in areas with high contents of this component (Freire et al, 2013;Vidal & Neto, 2014), the high concentration of P in reservoir waters is related to soil hillside erosion.…”

The Discharge of Effluents and the Contamination by Toxic Metals and Organic Matter in Bastiana Lake, Ceará, Brazil

“…One of the main problems related to eutrophication is the proliferation of cyanobacteria, which can produce toxins that affect the health of animals and humans (Vidal and Capelo Neto, 2014) Therefore, public investment and the expansion of the sewage treatment system is required for all sewage generated in the region may have a suitable destination and treatment given the entire population. Environmental education is needed to encourage the public about the importance and benefits of conservation of aquatic systems.…”