Abstract
The objective of the paper was to determine the quantity of lead and its potential and actual risks to the environment in gley-muck soil and mucky soil situated on the margins of peatmoors in the headstreams of the Liwiec River, based on the sequential analysis of metals and organic carbon.
The sequential extraction was carried out and the following operational fractions of metal were extracted: soluble in water (H2O); exchangeable (1M KCl); complex metal bound to humic substances (0.1M Na4P2O7); metals with stronger bonds to humic substances (0.1M NaOH); metals with stronger bonds to the organic and mineral solid soil phases (4M HNO3); and residual (aqua regia). The solutions were tested for the content of carbon (on a CHN-TCD autoanalyser) and lead (ICP-AES).
It was found that the organic matter in the tested soil samples showed a substantial degree of transformation with a predominance of mineralisation over humification. A higher level of lead accumulation was detected in the gley-muck soil. In both types of soil its content was assessed as natural. The accumulation of organic matter, the acidity and the content of phosphorus, sulphur and iron have a significant positive impact on the accumulation of lead in the examined types of soil. It was found that the highest concentration of lead was detected in the fractions strongly bound to the organic and mineral solid soil phases and in the complex compounds with humic substances, which indicates the potential for migration of metal outside the levels of organic matter accumulation. Less than 2% of the total lead content is present in most bioavailable fractions. More lead in the complex compounds with humic substances was found in the fraction of fulvic acids and, for other humic substances, in the fraction of humic acids.