Table 2.

Content of selected heavy metals in sewage sludge between 1977 and 2012 in Germany in (mg/kg DM).

Trace element	1977a	1982a	1986–1990a	2001a	2005a	2012b	Change between 1977 (=100%) and 2012	Change between 2001 (=100%) and 2012
Pb	220	190	113	53	40.4	34	−84.5	−35.8
Cd	21	4.1	2.5	1.2	0.97	1	−95.4	−16.7
Cr	630	80	62	45	37.1	33	−94.8	−26.7
Cu	378	370	322	304	306.4	292	−22.7	−3.9
Ni	131	48	34	27	25.2	25	−80.9	−7.4
Hg	4.8	2.3	2.3	0.8	0.59	0.5	−89.6	−37.5
Zn	2.140	1.480	1.045	794	756.7	762	−64.4	−4.0

References:

^aAdapted from (Bergs, 2015).

^b(Wiechmann et al., 2013).