S?o Paulo State is the main sugar cane producer and these agricultural activities are carried out in predominantly sandy soils, which require large amounts of phosphate fertilizers and amendments. This work evaluated ...S?o Paulo State is the main sugar cane producer and these agricultural activities are carried out in predominantly sandy soils, which require large amounts of phosphate fertilizers and amendments. This work evaluated the fertilizer-effect on the Al, Ba, Fe, Mn and Ni released in a watershed with influence of sugar cane crops in the S?o Paulo State, Brazil, namely the Monjolo Grande Stream basin. Five surface water sampling campaigns were carried out at the mouth of Monjolo Grande Stream in February, April, June, September and November 2010, characterizing the following parameters: discharge, pH, temperature, electric conductivity, dissolved oxygen and total and dissolved concentrations of Al, Ba, Fe, Mn and Ni. Approximately 99% of Al and Fe are transported annually in association with suspended sediments carried to the Monjolo Grande Stream by sheet erosion. The results also demonstrated that the increasing Al, Ba, Fe and Mn concentrations dissolved in the waters of the Monjolo Grande Stream basin in the wet season are associated to phosphate fertilizers and amendments that are used extensively in agrichemical activities. However, with the current application rates, there has been no increase in the dissolved concentrations of these metals at levels that could pose risks to human health.展开更多
Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake vari...Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the distur- bance intensity to sediments, which caused the increase of suspended solids （SS） concentration, total phosphorus （TP） concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well： when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4,86 mg/（md） at 0.4 m/s. The concentration of total dissolved phosphorous （TDP） and soluble reactive phosphate （SRP） both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.展开更多
文摘S?o Paulo State is the main sugar cane producer and these agricultural activities are carried out in predominantly sandy soils, which require large amounts of phosphate fertilizers and amendments. This work evaluated the fertilizer-effect on the Al, Ba, Fe, Mn and Ni released in a watershed with influence of sugar cane crops in the S?o Paulo State, Brazil, namely the Monjolo Grande Stream basin. Five surface water sampling campaigns were carried out at the mouth of Monjolo Grande Stream in February, April, June, September and November 2010, characterizing the following parameters: discharge, pH, temperature, electric conductivity, dissolved oxygen and total and dissolved concentrations of Al, Ba, Fe, Mn and Ni. Approximately 99% of Al and Fe are transported annually in association with suspended sediments carried to the Monjolo Grande Stream by sheet erosion. The results also demonstrated that the increasing Al, Ba, Fe and Mn concentrations dissolved in the waters of the Monjolo Grande Stream basin in the wet season are associated to phosphate fertilizers and amendments that are used extensively in agrichemical activities. However, with the current application rates, there has been no increase in the dissolved concentrations of these metals at levels that could pose risks to human health.
基金National Key Project for Basic Research,No.2012CB417004
文摘Since the construction of the Three Gorges Dam, the Poyang Lake hydrological characteristics obviously changed. During the impoundment period of the Three Gorges Reservoir, the hydrodynamic factors of Poyang Lake varied. Water level dropped, the velocity decreased and water exchange time lengthened, which changed the release of phosphorous from sediments. In order to investigate how the hydrodynamic factors influence the release of phosphorous from sediments, we used a two-way annular flume device to simulate the release characteristics of phosphorous from sediments under variable water levels and velocities. We found that both water level rising and velocity increasing could enhance the distur- bance intensity to sediments, which caused the increase of suspended solids （SS） concentration, total phosphorus （TP） concentration in the overlying water, and the ability that phosphorus released to overlying water from sediments enhanced as well： when overlying water velocity maintained 0.3 m/s, SS concentration increased to 4035.85 mg/L at the water level 25 cm which was about 25 times compared to the minimum value and TP concentration in the overlying water also reached the maximum value at the water level 25 cm which was 1.2 times that of the value at 10 cm; when water level maintained 15 cm, SS concentration increased to 4363.35 mg/L at the velocity of 0.5 m/s which was about 28 times compared to the value of 0 m/s, and TP concentration in the overlying water increased from 0.11 mg/L to 0.44 mg/L. When the water level maintained 15 cm, the phosphorous release rate reached the maximum value of 4,86 mg/（md） at 0.4 m/s. The concentration of total dissolved phosphorous （TDP） and soluble reactive phosphate （SRP） both in overlying water and sediment-water interface were negatively correlated with pH. Using the parabolic equation, the optimum water level at a velocity of 0.3 m/s was calculated to be 0.57 cm, and the optimum velocity at water level of 15 cm was found to be 0.2 m/s.
