Fig. 4. The mean concentrations of Zn (◆), Pb (×), Ni (▼), and Cd (■) in suspended particulate matter (SPM) from monthly measurements between 2000–2004 (source: Rijkswaterstaat, www.waterbase.nl) versus total concentrations in the upper 2 cm of sediment (average of 3 samples). The error bars represent one standard deviation of the SPM values. A solid line represents the 1:1 relation; note the log scales.
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