RESUMOA exploração dos solos de várzeas do Rio Grande do Sul, Brasil, tem sido historicamente restrita ao binômio arroz irrigado-pecuária extensiva. Dentre os diversos fatores que contribuem para este quadro, as más condições de drenagem são dos mais restritivos, haja vista que, especificamente em relação ao arroz irrigado, tal situação acarreta atraso no plantio com conseqüente queda da produtividade. Como objetivo inicial, o modelo SWAP foi validado com dados de um solo típico das várzeas do Rio Grande do Sul, para posteriormente se empregá-lo na simulação de diversos cenários sob diferentes condições de drenagem e os resultados dessas simulações foram confrontados com critérios que avaliam a possibilidade de preparo do solo, com base em sua umidade. Este confronto mostrou haver relação muito estreita entre a drenagem subsuperficial e superficial; quando esta é satisfatória, os perfis de umidade podem ser compatíveis com o preparo do solo, mesmo com drenos subsuperficiais bastante espaçados; caso contrário, o crescimento no número de dias aptos para a mecanização exige a presença de drenos subsuperficiais muito próximos. Palavras-chave: simulação, manejo do solo, arroz irrigadoDrainage conditions related with mechanization in flood plain soil (RS-Brazil) ABSTRACTThe exploration of flood plains soils in the State of Rio Grande do Sul (Brazil) has been historically restricted to the binomial 'irrigated rice crop -livestock'. Among several factors that contribute to that situation, the bad drainage conditions are one of the most important. In relation to irrigated rice, this situation promotes late planting and, consequently, productivity reduction. After validation with measured data in a typical flood plain soil of Rio Grande do Sul, the SWAP model was used to simulate scenarios under different drainage conditions. The results were compared with criteria that evaluate soil tillage possibility based on moisture values. This comparison showed a close relationship between subsurface and surface drainage. When surface drainage is satisfactory, soil moisture contents can be compatible with soil tillage, even if subsurface drains are too widely spaced. Otherwise, the increase in number of workable days for mechanization requires very closely-spaced subsurface drains.
On July 16, 2000, a rupture of a pipeline occurred in the Scraper area of the PETROBRAS refinery located in Araucaria, in the state of Parana, south of Brazil. This resulted in the spill of approximately 4,000m3 (1,060,000 gallons) of a crude oil (Cusiana − 41°API). The spilled oil spread over part of the refinery area, affecting the wetlands that are crossed by the Arroio Saldanha creek before discharging into the Barigui River, which is a tributary of Iguassu River. This entire area crossed by the creek is referred to as Point Zero (PO). This paper presents the chemical data of 2 monitoring programs: the Barigui, Iguassu and Arroio Saldanha Rivers, and the groundwater of Point Zero. The programs were carried out in 2 phases: for 3 months immediately after the spill and 1 year later. They included the analyses of BTEX, TPH, PAH, n-alkanes, UCM and biomarkers for the water and sediment samples. The rivers program encompassed 13 stations along Barigui and Iguassu Rivers and 1 station at Arroio Saldanha Creek. The results in water and sediments demonstrated the efficiency of the recovering of the spilled oil from the water. That suggested that the impact of the spill on the Barigui and Iguassu Rivers was of a short duration after the spill. On the other hand, the hydrocarbon concentration data for Arroio Saldanha Creek during the 3 months after the spill revealed high levels of hydrocarbon contamination, which corroborated the visual inspection. The groundwater monitoring program in the terrestrial area of Point Zero was initiated shortly after the spill. The groundwater program included about 80 monitoring wells (piezometers) installed, along the Arroio Saldanha Creek and in the wetlands crossed by the creek. It could be observed that BTEX and TPH groundwater concentrations decreased significantly after one year.
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