123
Tecnología y Ciencias del Agua
, vol. VIII, núm. 2, marzo-abril de 2017, pp. 117-126
Wang
et al
.,
Simulation for non-point source pollution based on QUAL2E in the Jinghe River, Shaanxi Province, China
ISSN 2007-2422
•
to Oct 2007; the period from Nov to Feb of the
following year represented dry seasons while
the period from July to Oct represented wet sea-
sons. The average values of the current velocity
and the flow rate from 2002 and 2007 for the two
sections were selected. The river reaches from
the Jingcun section to Zhangjiashan section is
120 km long.
Results and analysis
PCA was conducted for the 16 sets of water
quality data for dry seasons in the Jingcun sec-
tion and for dry and wet seasons in the Zhangji-
ashan section from Nov 2004 to Oct 2007. The
rotated factor loadings matrixes obtained for the
different periods are give elsewhere (Wang
et
al
., 2012). Six factors with eigenvalues greater
than 1 extracted from the Jingcun section con-
tributed to 87.737% (> 85%) of the variance in
dry seasons, and three and four factors extracted
from the Zhangjiashan section corresponded to
87.253 and 92.865% (> 85%) of the variance in
dry and wet seasons, respectively. The most
meaningful parameters within each component
can be identified by investigating the factor
loadings matrix. It can be reasonably assumed
that parameters of the same component share
the same origin.
The main pollutants in the Jingcun section
during dry season were salt indices (VF1,
including chloride, conductivity, NO
x
, and
salinity) and organic pollution indices (VF2,
including volatile phenol and ammonia ni-
trogen), whereas those of the Zhangjiashan
section in dry seasons were organism indices
(VF1, including sulfate, COD
Mn
, NH
4
+
-N, NO
x
,
and BOD
5
) and salt indices (VF2, including
salinity, electrical conductivity, and chloride).
In dry seasons, the river water was recharged
by the groundwater, and NO
x
and chloride in
the Jingcun section were closely associated on
VF1, which suggests an exchange of water from
the groundwater to surface water system. In the
Zhangjiashan section, NO
x
was loaded on VF1
and was thus associated with point source dis-
charges of domestic sewage, and similar other
discharges. In dry seasons, ammonia nitrogen
and volatile phenol in the Jingcun section were
loaded on VF2, the source of which was waste
water discharged from papermaking enter-
prises in the upper reaches of the Jinghe River;
in the Zhangjiashan section, ammonia nitrogen
and NO
x
, which came from point source dis-
charges of domestic sewage and similar, were
on VF1. In wet seasons, the main pollutants in
the Zhangjiashan section were non-point source
pollution indices (VF1, including nitrogen
nutrient indices (NO
x
and total nitrogen) and
sulfate) and organic pollution indices (VF2,
including volatile phenol, ammonia nitrogen,
and salinity).
The above analysis shows that, regardless
of dry or wet seasons, the water environment
between the Jingcun and Zhangjiashan sections
was mainly polluted by nitrogen nutrient and
organic pollution indices.
The source-sink terms of NH
4
+
-N and
NO
3
−
-N in wet and dry seasons from 2002 to
2007, respectively, were calculated using equa-
tion (11) and tabulated in table 1.
There was a slight variation in the source-
sink terms of NO
3
−
-N in dry seasons of the
years (table 1), showing that the point source
discharges of domestic sewage and similar were
stable; the terms varied considerably in wet
seasons, and the values in 2003 and 2007 were
much higher than in those the other years. The
precipitation and runoff values were large in the
wet seasons of 2003 and 2007, so the non-point
source pollution loads were also quite large.
Examination of the annual precipitation and
corresponding non-point source load of NO
3
−
-N
(figure 3) shows that, when the precipitation was
between 400 and 500 mm, the non-point source
load did not change significantly, but as the
precipitation increased, the load also increased
rapidly, because the increased amount of runoff
carried more pollutants. However, with further
increases in precipitation, the non-point source
load gradually dropped down, which may be
attributed to the smaller amount of fertilizers in
the soil. Even though 2006 was a normal year,
the non-point source load of NO
3
−
-N was less
