Fig. 4. Concentration and time effects on "bioavailable" copper concentration ([Cu]_bio) in water extracts from soil systems. (A) [Cu]_bio measured with the Cu-reporter strain DF57-Cu15 in water extracts from Cu-amended soils after incubation for 1 h (circles), 19 h (squares), 8 d (triangles), 32 d (crosses), and 220 d (diamonds). Fitted linear regression lines for each incubation period are shown. The data presented are from duplicate soil systems and each point represents a single soil system. (B) [Cu]_bio in water extracts in percentage of added Cu, as function of the incubation time and dose of 100 (squares), 200 (crosses), 400 (triangles), and 800 (diamonds) µmol Cu kg^–1 soil. Fitted logarithmic regression lines for each Cu amendment are shown. The data presented are from duplicate soil systems and each point represents a single soil system. (C) [Cu]_bio as fraction of total copper concentration ([Cu]_tot) in water extracts and a dose of 100 (squares), 200 (crosses), 400 (triangles), and 800 (diamonds) µmol Cu kg^–1 soil, as function of the incubation time.