Treatment of lake sediments with salts is a promising approach for preventing phosphorus release from sediments. Five 35-d treatments of undisturbed sediment cores in the East Lake, Wuhan, China were applied under ano...Treatment of lake sediments with salts is a promising approach for preventing phosphorus release from sediments. Five 35-d treatments of undisturbed sediment cores in the East Lake, Wuhan, China were applied under anoxic conditions： nothing added （control）, Al2（SO4）3 added, FeCl3 added, CaCl2 added, and NaNO3 added. To identify changes in the P binding sites in the sediment caused by the treatments, different P binding forms were extracted from the sediment before and after the treatments. We found that the mean P release rates for anoxic treatments with Al2（SO4）3, FeCl3, CaCl2 and NaNO3 were -0.6, 0.03, 0.6 and 2.6 mg/（m^2·d）, respectively, while the P release rate with no additives was 7.3 mg/（m^2·d）. In suboxic conditions, the concentration of total phosphorus （TP ge 657 mg/kg） in sediment was much lower than that of untreated sediment （TPaverage 688 mg/kg） and treatments with salts （TP（Al2（SO4）3） 793 mg/kg, TP（FeCl3） 781 mg/kg, TP（NaNO3） 802 mg/kg, TP（CaCl2） 747 mg/kg）. We also found that adding CaCl2 prevented P release because of apatite formation and because PCa （Ca bound P） increased at the sediment surface. Addition of Fe^3＋ and NO3^- to the sediment increased the amounts of PFe. Mn （Redox-sensitive P, mostly Fe and Mn compounds）, since iron oxide has the ability to combine P. Addition of Al2（SO4）3 increased the fraction of PAl, Fe （P bound to metal oxides （Al, Fe）） and decreased the P and Fe in the water above the anoxic sediment, showing the greater ability orAl in binding P. The results showed that Al2（SO4）3, FeCl3, CaCl2 and NaNO3 all had an effect in controlling phosphorus release. The effect was related to the forms of phosphorus existing in the sediment before treatment and the forms resulting after adding the four reagents. The combination of Al^3＋ or Fe^3＋ with NO3^- promises to be a reasonable chemical treatment for increasing the P retention capacity of sediments in eutrophic lakes. If chemical treatment is combined with bioremediation, the aim of environmental repair may be achieved.展开更多
Water quality in rivers is vital to humans and to maintenance of biotic and ecological integrity.During the Four Major Rivers restoration of South Korea, remarkable attempts have been made to decrease external nutrien...Water quality in rivers is vital to humans and to maintenance of biotic and ecological integrity.During the Four Major Rivers restoration of South Korea, remarkable attempts have been made to decrease external nutrient loads and moveable weirs were designed to discharge silt that may deposit in pools. However, recently eutrophication of the Nakdong River, which was limited to the lower reaches, is seen to be spreading upstream. The reduction of external nutrient loads to rivers is a long-term goal that is unlikely to lead to reductions in algal blooms for many years because of the time required to implement effective land management strategies. It would therefore be desirable to implement complementary strategies. Regulating the amount of water released is effective at preventing algae blooms in weir pools; so, the relationship between discharge, stratification and bloom formation should be understood in this regard. However, pollutants are likely to accumulate in the riverbed upstream from release points. Thus, to control phosphorus levels, total phosphorus density should be lowered by applying in-river techniques as well. As many ecosystem properties are controlled by multiple processes, simultaneous river bottom improvement techniques, such as combined dissolved oxygen supply and nutrient inactivation, are likely to be effective. The purpose of this review is to present a series of technological approaches that can be used to improve the river bottom area and hence sediment nutrient release, and to illustrate the application of these techniques to the Nakdong River.展开更多
文摘Treatment of lake sediments with salts is a promising approach for preventing phosphorus release from sediments. Five 35-d treatments of undisturbed sediment cores in the East Lake, Wuhan, China were applied under anoxic conditions： nothing added （control）, Al2（SO4）3 added, FeCl3 added, CaCl2 added, and NaNO3 added. To identify changes in the P binding sites in the sediment caused by the treatments, different P binding forms were extracted from the sediment before and after the treatments. We found that the mean P release rates for anoxic treatments with Al2（SO4）3, FeCl3, CaCl2 and NaNO3 were -0.6, 0.03, 0.6 and 2.6 mg/（m^2·d）, respectively, while the P release rate with no additives was 7.3 mg/（m^2·d）. In suboxic conditions, the concentration of total phosphorus （TP ge 657 mg/kg） in sediment was much lower than that of untreated sediment （TPaverage 688 mg/kg） and treatments with salts （TP（Al2（SO4）3） 793 mg/kg, TP（FeCl3） 781 mg/kg, TP（NaNO3） 802 mg/kg, TP（CaCl2） 747 mg/kg）. We also found that adding CaCl2 prevented P release because of apatite formation and because PCa （Ca bound P） increased at the sediment surface. Addition of Fe^3＋ and NO3^- to the sediment increased the amounts of PFe. Mn （Redox-sensitive P, mostly Fe and Mn compounds）, since iron oxide has the ability to combine P. Addition of Al2（SO4）3 increased the fraction of PAl, Fe （P bound to metal oxides （Al, Fe）） and decreased the P and Fe in the water above the anoxic sediment, showing the greater ability orAl in binding P. The results showed that Al2（SO4）3, FeCl3, CaCl2 and NaNO3 all had an effect in controlling phosphorus release. The effect was related to the forms of phosphorus existing in the sediment before treatment and the forms resulting after adding the four reagents. The combination of Al^3＋ or Fe^3＋ with NO3^- promises to be a reasonable chemical treatment for increasing the P retention capacity of sediments in eutrophic lakes. If chemical treatment is combined with bioremediation, the aim of environmental repair may be achieved.
基金supported by the Korea Institute of Civil Engineering and Building Technology, KICT, of Korean Government number 2014–0316
文摘Water quality in rivers is vital to humans and to maintenance of biotic and ecological integrity.During the Four Major Rivers restoration of South Korea, remarkable attempts have been made to decrease external nutrient loads and moveable weirs were designed to discharge silt that may deposit in pools. However, recently eutrophication of the Nakdong River, which was limited to the lower reaches, is seen to be spreading upstream. The reduction of external nutrient loads to rivers is a long-term goal that is unlikely to lead to reductions in algal blooms for many years because of the time required to implement effective land management strategies. It would therefore be desirable to implement complementary strategies. Regulating the amount of water released is effective at preventing algae blooms in weir pools; so, the relationship between discharge, stratification and bloom formation should be understood in this regard. However, pollutants are likely to accumulate in the riverbed upstream from release points. Thus, to control phosphorus levels, total phosphorus density should be lowered by applying in-river techniques as well. As many ecosystem properties are controlled by multiple processes, simultaneous river bottom improvement techniques, such as combined dissolved oxygen supply and nutrient inactivation, are likely to be effective. The purpose of this review is to present a series of technological approaches that can be used to improve the river bottom area and hence sediment nutrient release, and to illustrate the application of these techniques to the Nakdong River.
