at seven of the ten stites in the major tributaries of Upper Yangtze River and
continued increasing (with a rate of 4.9 μeq L
À1 year
À1 ) to 112 μeq L
À1 at almost
all the stites during 1998–2007, coinciding with the increase of the emission of NO x
and NH 3 (Duan et al. 2011). However, the contribution of NO 3
À to surface water
acidification was far less than that of SO 4
2À , manifested as the equivalence ratio of
NO 3
À to SO 4
2À in water (averaged at 0.11) much smaller than the equivalence ratio
of N/S in emission (about 0.47 in 2008) (Duan et al. 2011). According to the survey
of 255 forest streams, the NO 3
À concentration (averaged at 110 μeq L
À1 ) in the
stream water was much less than SO 4
2À (averaged at 810 μeq L
À1 ), even under the N
Fig. 8.5 The pH values of the 73 large water bodies (rivers, lakes, or reservoirs; Qiao et al. 2016)
and 255 forest streams (Yu et al. 2017b)
2000 2002 2004 2006 2008 2010 2012 2014
0.0
0.1
0.2
0.3
0.4
NO
3
-
/SO
4
2)
q
e
/
q
e
(
Throughfall
Stream water
2000 2002 2004 2006 2008 2010 2012 2014
0.2
0.4
0.6
(NH
4
+
O
N
+
3
-
O
S
/
)
4
2)
q
e
/
q
e
(
Throughfall
Stream water
Fig. 8.6 The equivalence ratio of NO 3
À
/SO 4
2À and TIN/SO 4
2À in throughfall and stream water
during 2001–2013 at Tieshanping, Chongqing. (This figure was adapted from Yu et al. 2017c with
permission by American Chemical Society)
166
Q. Yu and L. Duan