壤全氮、土壤有机质的测定对农业生产和科学研究都有重要意义。因此在许多实验室里,土壤全氮、土壤有机质都被作为一项常规分析项目。土壤全氮量的测定百余年来沿用杜马氏法和凯氏定氮法。测定土壤有机质的方法主要有3种:干烧法、化学...壤全氮、土壤有机质的测定对农业生产和科学研究都有重要意义。因此在许多实验室里,土壤全氮、土壤有机质都被作为一项常规分析项目。土壤全氮量的测定百余年来沿用杜马氏法和凯氏定氮法。测定土壤有机质的方法主要有3种:干烧法、化学氧化法、灼烧法,1989年农业部颁布了国标GB9843-88《土壤有机质测定法》。近年来使用元素分析仪(Elementar Vario MACRO)测定土壤C、N也越来越广泛,元素分析仪是一台用于快速,定量测定元素C、H、N、S的全自动分析仪。用元素分析仪测定C、H、N的方法属于灼烧法,灼烧温度为960摄氏度,对酸性、中性土壤的测定无疑是省时准确的首选。石灰性土壤中由于碳酸盐的存在,在高温灼烧时碳酸盐分解,形成CO2,使土壤有机质的测定结果偏高。降低燃烧管温度测定(630摄氏度),由于样品用锡箔纸包裹,锡箔纸在燃烧管内燃烧生成氧化锡为放热反应,增加燃烧管内的温度高于设定温度,增加碳酸钙的分解测定值偏高,燃烧管温度设定在低于碳酸盐分解点时仪器密封不严实,使测定结果偏低。用盐酸处理土壤中碳酸盐,其后测定有机质时,因土壤中的富里酸溶于酸,使测定结果偏低。因此元素分析仪不适于石灰性土壤有机质的测定。展开更多
Up to this day I still can vividly remember a routine in my elementary school:the daily school-wide morning calisthenics. It started at about 7:45 am in the school courtyard.Our physical education teacher stood on the...Up to this day I still can vividly remember a routine in my elementary school:the daily school-wide morning calisthenics. It started at about 7:45 am in the school courtyard.Our physical education teacher stood on the concrete stage where our principal would give her talk at school assemblies.All children and teachers would follow the teacher’s lead to do the eight-segment national calisthenics in unison with loud music from loudspeakers affixed on trees around the courtyard.When I visited the school last May,I saw that students still performed the routine faithfully but with a different set of展开更多
Sludge production is an avoidable problem arising from the treatment of wastewater.The sludge remained after municipal wastewater treatment contains considerable amounts of various contaminants and if is not properly ...Sludge production is an avoidable problem arising from the treatment of wastewater.The sludge remained after municipal wastewater treatment contains considerable amounts of various contaminants and if is not properly handled and disposed,it may produce extensive health hazards.On the other hand,this sludge has benefit for plants and soils.Sludge samples were collected over a 12 month period from sewage treatment plants(STP's),i.e,Khairathabad and Meeralam Tank,Hyderabad,India and analyzed for C,H,N,S by elementar analyzer,P,K,Ca,Mg by spectrophotometer and heavy metals like Zn,Pb,Ni,Cu,Cd by atomic absorption spectrophotometer.The sludge contained approximately 50%organic matter and 1-4%inorganic carbon.Organic and inorganic carbon,organic nitrogen,inorganic phosphorous,Ca and Mg were found to be present in sludge at a relatively constant concentration with respect to sampling time.Inorganic N,organic P,K,and all metals were found to be quite variable with time when sludge produced from different STP's.展开更多
文摘壤全氮、土壤有机质的测定对农业生产和科学研究都有重要意义。因此在许多实验室里,土壤全氮、土壤有机质都被作为一项常规分析项目。土壤全氮量的测定百余年来沿用杜马氏法和凯氏定氮法。测定土壤有机质的方法主要有3种:干烧法、化学氧化法、灼烧法,1989年农业部颁布了国标GB9843-88《土壤有机质测定法》。近年来使用元素分析仪(Elementar Vario MACRO)测定土壤C、N也越来越广泛,元素分析仪是一台用于快速,定量测定元素C、H、N、S的全自动分析仪。用元素分析仪测定C、H、N的方法属于灼烧法,灼烧温度为960摄氏度,对酸性、中性土壤的测定无疑是省时准确的首选。石灰性土壤中由于碳酸盐的存在,在高温灼烧时碳酸盐分解,形成CO2,使土壤有机质的测定结果偏高。降低燃烧管温度测定(630摄氏度),由于样品用锡箔纸包裹,锡箔纸在燃烧管内燃烧生成氧化锡为放热反应,增加燃烧管内的温度高于设定温度,增加碳酸钙的分解测定值偏高,燃烧管温度设定在低于碳酸盐分解点时仪器密封不严实,使测定结果偏低。用盐酸处理土壤中碳酸盐,其后测定有机质时,因土壤中的富里酸溶于酸,使测定结果偏低。因此元素分析仪不适于石灰性土壤有机质的测定。
文摘Up to this day I still can vividly remember a routine in my elementary school:the daily school-wide morning calisthenics. It started at about 7:45 am in the school courtyard.Our physical education teacher stood on the concrete stage where our principal would give her talk at school assemblies.All children and teachers would follow the teacher’s lead to do the eight-segment national calisthenics in unison with loud music from loudspeakers affixed on trees around the courtyard.When I visited the school last May,I saw that students still performed the routine faithfully but with a different set of
文摘Sludge production is an avoidable problem arising from the treatment of wastewater.The sludge remained after municipal wastewater treatment contains considerable amounts of various contaminants and if is not properly handled and disposed,it may produce extensive health hazards.On the other hand,this sludge has benefit for plants and soils.Sludge samples were collected over a 12 month period from sewage treatment plants(STP's),i.e,Khairathabad and Meeralam Tank,Hyderabad,India and analyzed for C,H,N,S by elementar analyzer,P,K,Ca,Mg by spectrophotometer and heavy metals like Zn,Pb,Ni,Cu,Cd by atomic absorption spectrophotometer.The sludge contained approximately 50%organic matter and 1-4%inorganic carbon.Organic and inorganic carbon,organic nitrogen,inorganic phosphorous,Ca and Mg were found to be present in sludge at a relatively constant concentration with respect to sampling time.Inorganic N,organic P,K,and all metals were found to be quite variable with time when sludge produced from different STP's.
