Resumo

RASCHE ALVAREZ, Jimmy Walter et al. Water erosion and loss of sediment, water and chemical elements during rainfall events in two rural watersheds. Investig. Agrar. [online]. 2014, vol.16, n.2, pp.113-123. ISSN 2305-0683.

Agricultural activities generate impacts on the environment and require constant study and monitoring to improve understanding of the forms and degree of contamination. The present study aimed to quantify the losses of water, sediment and chemical elements during two rainfall events in two rural watersheds (RW) from an agricultural settlement in Júlio de Castilhos, State of Rio Grande do Sul, Brazil. The studied RWs have an area of 144.5 ha (RW140) and 79.5 ha (RW80), with different land use distribution. The monitored rainfall events occurred in 18 (45.9 mm) and 19 (39.7 mm) September 2012. Water loss by runoff in the RW140 was 5.5%, and in RW80 was 15.2%. In the RW140 the highest concentration of suspended sediment was 1.4 g L^-1 compared to 0.9 g L^-1 in RW80. The levels of soluble phosphorus in the water samples + sediment in the RW80 ranged between 0.01 and 0.02 mg L^-1 and en the RW140 reached 0.06 mg L^-1. Total phosphorus in samples of water samples + sediment in the RW140 was higher than the RW80, reaching maximum values of 2.10 and 0.47 mg L^-1 in the RW140 in the first and second event, respectively. Both RWs in this study showed low phosphorus losses, moderate losses of bases (Ca, Mg, K e Na) and elements that are constituents of the soil structure as Fe, Al, Mn, and insignificant losses of metallic trace elements.

Palavras-chave : Water quality; soil degradation; eutrophication; water contamination.

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