Stable ‘Non-Traditional’ Isotopes - Application of Geochemical Tracers to Fluvial Sediment - page 121

One of the first detailed analyses pertaining to riverine systems was carried out
by Chen and his colleagues on both the dissolved (Chen et al. 2008 ) and particulate
(Chen et al. 2009 ) load within the Seine River of France. The Seine River is highly
contaminated by a number of toxic trace metals (e.g., Cu, Ni, Pb, and Zn) derived
from both industrial and urban sources in and around Paris. With regard to particulate
matter, the study by Chen et al. ( 2009 ) consisted of two primary components: (1) a
longitudinal study of the spatial changes in Zn concentrations and

66 Zn values
that includes reaches located both up- and downstream of Paris, and (2) a study
of the changes in Zn concentration and

ʴ

66 Zn values through time at a site near the
center of Paris. The latter primarily focused on the geochemical differences observed
between low and high flow events.

ʴ

66 Zn values were calculated using the JMC
3-0749-L standard solution. Zn concentrations were primarily presented in terms
of the magnitude of anthropogenic Zn enrichment above background values where
background was taken as the Zn and Al concentrations measured in uncontaminated
pre-historic deposits and forest soils.
Along the length of the channel, EFs varied semi-systematically from up- to
downstream, ranging from about 1 to 5

ʴ

3, respectively (concentrations ranged from
about 100 to 400ppmZn). The increase presumably reflected the increase inZn inputs
from industrial and urban sources around Paris.

.

66 Zn values decreased downstream

ʴ

66 Zn data collected in Paris for

from 0 . 30 to 0 . 08 in SPM. Temporally, the ʴ

varying flow conditions ranged from about 0 . The combined spatial

and temporal data exhibited an inverse relationship between EFs and

. 08 to 0 . 26

66 Zn values
(Fig. 5.2 ). Chen et al. ( 2009 ), after ruling out other factors such as adsorption, argued
that the semi-systematic trends between increasing Zn concentration and decreasing
ʴ

ʴ

66 Zn values was the result of particulate mixing of Zn from differing sources. Thus,
the trend could be interpreted as a mixing curve defined by two end-members. The
end-member characterized by the highest

66 Zn values (lowest Zn concentrations)

ʴ

66 Zn value of 0

was consistent with a measured in granitic basement rocks

within the catchment, and which is similar to the mean integrated value of 0

ʴ . 33

. 30%

66 Zn
end-member was interpreted to represent Zn in the particulate matter of a wastewater
treatment plant (0.08-0.15

reported for Zn in other earth materials (Cloquet et al. 2008 ). The lower ʴ

) and samples of roof and road runoff ( − 0 . 10 to 0 . 08 ).

66 Zn values formed a mixing line,
Chen et al. ( 2009 ) were able to determine the proportions of Zn from both natural
and anthropogenic sources. They found that the proportion of anthropogenic Zn
increased downstream, reaching a maximum value at the catchment mouth (pre-
estuary) of 86%; the average basin valuewas 62 %. Given ameasured SPMZn load of
∼

By assuming that the variations in EF and ʴ

315 t/yr, the Zn load from natural sources is about 44 t/yr, a value which was similar
to the 42 t/yr value determined from monitoring data on the Seine River. Temporal
variations in anthropogenic Zn contributionswere also observed at themonitoring site
in Paris. Here, anthropogenic contributions decreased within increasing discharge,
and ranged from about 40% during high flows to 100% during low flows.
Interestingly, Zn isotopic data collected in the Seine River suggest that the source
of Zn in dissolved and particulate load may differ. More specifically,

66 Zn values
suggested that the primary natural source of Zn within the SPM was granitic rocks

ʴ