3.2. Isotopic data
The dual isotopic data for lake, river and underground water samples are
shown in Table 1. In the nondiversion and diversion water periods, the
δ34SSO4 values in the lake samples
ranged from 9.5‰ (in Zhaoyang sublake) to 13.35‰ (in Nanyang sublake
(SW)) and from 11.78‰ (in Zhaoyang sublake) to 14.63‰ (in Dushang
sublake) respectively, with average values of 11.78‰ and 13.34‰,
respectively. The fluctuation ranges of
δ34SSO4 in the nondiversion and
diversion water periods showed little variation. The
δ34SSO4 values in river samples in the
nondiversion and diversion water periods ranged from -0.07‰ (in the
Chengguo River) to 22.15‰ (in the Zhuzhaoxin River) and from 4.62‰ (in
the Sihe River) to 14.55‰ (in the Zhuzhaoxin River), respectively, with
mean values of 10.92‰ and 10.19‰, respectively. Compared with those for
the lake samples, the fluctuation ranges of
δ34SSO4 values in the river samples
were greater, and the δ34SSO4 value
range during the nondiversion water period was greater than that during
the diversion water period.
The values of δ18OSO4 in lake samples
ranged from 8.33‰ (in Zhaoyang sublake) to 11.22‰ (in Nanyang sublake
(SW)) and from 8.6‰ (in Zhaoyang sublake) to 9.88‰ (in Dushan sublake)
in the nondiversion and diversion water periods, respectively, with
average values of 10.14‰ and 9.34‰, respectively. In the river samples,
the values of δ18OSO4 varied from
7.59‰ (in the Guangfu River) to 13.45‰ (in the Zhuzhaoxin River) and
from 6.27‰ (in the Sihe River) to 11.81‰ (in the Zhuzhaoxin River) in
the nondiversion and diversion water periods, respectively, with mean
values of 9.90‰ and 9.15‰, respectively. The fluctuation ranges of
δ18OSO4 values from lake samples
displayed the same pattern as the
δ34SSO4 values. However, the
fluctuation ranges of δ18OSO4 values
from river samples were definitely smaller than those of
δ34SSO4 values. The maximum
δ18OSO4 and
δ34SSO4 values for both the lake and
river samples appeared at the same location during the nondiversion and
diversion water periods. The change in
δ34SSO4 values was not clear in most
of the samples for different periods, except samples from the Chengguo
River (Table 1 and Fig. 4(i) ), and the
δ18OSO4 values in samples all
approached a trend of 1:1 (Table 1 and Fig. 4(j) ),
except for the Sihe River. It can be assumed that the
SO42- source in these two rivers had
changed. In addition, the δ34SSO4 and
δ18OSO4 values from the gypsum
collected around NSL were 15.70‰ and 15.17‰, respectively.