Laboratory-dried specimens yield distorted information about the state of hydromorphic soil. Changes in the gas medium, humidity, temperature, aggregation capacity and illumination have an irreversible impact on the dried and powdered soil specimen. Properties of the dried hydromorphic soil can be altered significantly. Most altered are (1) the colour of the hydromorphic soils, (2) the рН value, and (3) the content of mobile trace metal (TM) compounds after drying the wet soil. Colour change (browning) of the hydromorphic soil is related to the oxidation of Fe(II). In a highly ferruginous soil, the browning is rapid and visible even to the naked eye. In the weakly ferruginous gley, the colour change is invisible to the naked eye, but instrumental field measurements reveal a slow and slight yellowing of the dried gley. In dried soils, laboratory рН values determined in soil suspension differ from the values determined in soil solution at the same time. The process of drying provokes a significant decrease in the content of mobile TM compounds, resulting in the illusion of less soil contamination than the real situation during hydromorphic soil humidification. When studying hydromorphic soils, it is desirable to accomplish the maximum possible field measurements. Laboratory analyses should only be carried out for specimens stored under dark conditions since they retain the initial humidity, temperature and gas composition.

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