Abstract:
Manganese is an essential and important mineral element for plants. The content of available manganese in soil is very beneficial to plant growth. Exchangeable manganese (ExMn) and reducible manganese (RMn) are the two most important forms of available manganese in soil. Establishing an accurate and rapid method for detecting ExMn and RMn in soil is of great significance for the evaluation of manganese availability in soil. In this paper, ammonium chloride was used to extract ExMn from soil, and ammonium chloride-hydroquinone and ascorbic acid (1:2,
m:
m) were used to extract RMn. Ammonium chloride was used instead of ammonium acetate in the extraction process, which not only inhibited the precipitation of carbonate-bound manganese in calcareous soil but also effectively extracted ExMn and RMn from soil. Ultrasonic extraction was used instead of shaking extraction, reducing the extraction time from 30 minutes to 5 minutes. The content of ExMn in the solution was directly determined by inductively coupled plasma-optical emission spectrometry (ICP-OES), and the content of RMn was obtained by the difference method. During the detection process, the instrument conditions were optimized, and the spectral line of 257.61nm was selected, with a detection limit of 0.13mg/kg. By using this method (ICP-OES) to detect ExMn, the relative standard deviation (RSD) of the determination results was 0.4%-3.3%, while the RSD of the AAS method was 2.1%-6.9% and that of the colorimetric method was 3.6%-9.8%. When detecting RMn, the RSD of this method was 0.7%-3.6%, that of the AAS method was 0.9%-5.3%, and that of the colorimetric method was 1.1%-9.2%. It indicates that the ICP-OES method established in this paper can simultaneously determine ExMn and RMn in soil samples, and has high precision.