Comparison of methods for measuring heavy metals and total phosphorus in soils contaminated by different sources

摘要

The relationships between the concentrations of zinc (Zn), lead (Pb), copper (Cu), nickel (Ni) and chromium (Cr) as measured by X-ray fluorescence analysis (XRF), aqua regia, and HNO_3 pressure digestion were studied in soil samples covering a wide range of heavy metal concentrations. The soils were contaminated by sewage sludge, exhaust depositions, river sediments of mining residues, and dump material. The question was addressed whether the source of heavy metals or other soil properties affect therelationship between these three methods. The aqua regia-digestible fraction of the five heavy metals reached on average 64% of the XRF-detectable content. The pressure accelerated HNO_3-digestible fraction of the five heavy metals was on average 71% ofthe XRF-detectable content; the respective phosphorus (P) fraction reached a median of 75%. This suggests that HNO_3 pressure digestion can also be used for characterizing the total P content of soils. Aqua regia extraction and HNO_3 pressure digestiongave similar values for Zn, Pb, and Cu, which dominate the heavy metal load of most contamination sources. Significantly higher Cr values were obtained by HNO_3 pressure digestion than by aqua regia extraction. Additionally, the Cr contents were affectedby the source, e.g. sewage sludge had relatively high contents of aqua regia and HNO_3 pressure extractable contents in comparison to the XRF values. The element-specific relationships between the three methods were all highly significant. However, therespective multiple linear regression models were in most cases affected by soil organic carbon (C), in some cases by clay or soil pH.