Page 372 - Soil and water contamination, 2nd edition

Patterns in surface water 359

the 1950s. The monitoring of heavy metals started in the late 1960s and was expanded to
include many organic pollutants in the 1970s. The pollution history, however, often goes
much further back in time than the available water quality measurements. To reconstruct
the pollution history before regular water quality monitoring commenced, several proxies can
be used, such as concentration depth profiles in lake or floodplain sediments (e.g. Ayres and
Rod, 1986; Winkels, 1997; Middelkoop, 2000). In Section 16.4.3 an example of pollution
history of the river Rhine as documented by overbank deposits on a section of washland was
discussed.
3-
Figure 18.16 shows the trends in measured dissolved ortho-PO and Zn concentrations
4
in the river Rhine since regular monitoring began. From the start of the monitoring until
3-
the late 1970s the ortho-PO concentrations rose because intensified agricultural practices
4

3-
Figure 18.16 Long-term trends in a) ortho-PO 4 -P and b) Zn concentrations in the river Rhine near Lobith, the
Netherlands (source: Waterbase, 2013).

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