Rapid communications in mass spectrometry : RCM · 2020
Dynamics of nitrite in acidic soil during extraction with potassium chloride studied using 15 N tracing.
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Dai Shenyan, Wen Teng, Cai Zucong, Zhang Jinbo
Аннотация
RATIONALE: Nitrite is well known to be unstable, including during soil extraction with KCl (especially in acidic soils), but the source and fate of NO2 - in the short duration of the extraction process remain unclear.
METHODS: A series of 15 N-tracing studies explored NO2 - transformations during KCl extraction in acidic and alkaline soils. Tests considering multiple factors assessed the interactions of such factors as soil sterilization, extraction time, and pH adjustment. After addition of 15 NO2 - , 15 NH4 + , and 15 NO3 - tracers, the concentrations and isotopic compositions of N2 O, N2 , NH4 + , NO3 - , NO2 - , and dissolved organic nitrogen (DON) were measured to investigate the production and consumption of NO2 - .
RESULTS: Nitrite was stable in alkaline soils during KCl extraction. In contrast, changes did occur in acidic soils during KCl extraction: NO2 - declined rapidly in the first 10 min of extraction although the subsequent rate of decrease lessened as the extraction time progressed. Significant dilution of 15 NO2 - suggested high rates of NO2 - production and even higher rates of consumption. The soil's organic N was the only source of NO2 - and also its main destination. Soil sterilization showed that NO2 - processes during extraction were chemical, not microbial. The pH adjustment of acidic soil stabilized its NO2 - .
CONCLUSIONS: Overall, the pH adjustment of KCl solution appears favorable for investigating NO2 - dynamics. For example, this work recommends an extraction solution comprising a 4:1 mixture of 2.5 M KCl solution and pH 8.4 buffer, which was more convenient to operate than the method reported by Stevens and Laughlin.
METHODS: A series of 15 N-tracing studies explored NO2 - transformations during KCl extraction in acidic and alkaline soils. Tests considering multiple factors assessed the interactions of such factors as soil sterilization, extraction time, and pH adjustment. After addition of 15 NO2 - , 15 NH4 + , and 15 NO3 - tracers, the concentrations and isotopic compositions of N2 O, N2 , NH4 + , NO3 - , NO2 - , and dissolved organic nitrogen (DON) were measured to investigate the production and consumption of NO2 - .
RESULTS: Nitrite was stable in alkaline soils during KCl extraction. In contrast, changes did occur in acidic soils during KCl extraction: NO2 - declined rapidly in the first 10 min of extraction although the subsequent rate of decrease lessened as the extraction time progressed. Significant dilution of 15 NO2 - suggested high rates of NO2 - production and even higher rates of consumption. The soil's organic N was the only source of NO2 - and also its main destination. Soil sterilization showed that NO2 - processes during extraction were chemical, not microbial. The pH adjustment of acidic soil stabilized its NO2 - .
CONCLUSIONS: Overall, the pH adjustment of KCl solution appears favorable for investigating NO2 - dynamics. For example, this work recommends an extraction solution comprising a 4:1 mixture of 2.5 M KCl solution and pH 8.4 buffer, which was more convenient to operate than the method reported by Stevens and Laughlin.