Journal of Environmental Treatment Techniques
2020, Volume 7, Issue 3, Pages: 843-852
widely geographically distributed, and their warming is
associated with interactions among different climates factors
from seasonally ice-covered to ice-free lakes [8]. A Recent
study by Jordan et al. (2018) perform a response in riverine
communities to climate variables, and the results
demonstrated that the composition of functional feeding
groups is affected by changing climate conditions, which
case functional change at the ecosystem level [9]. Bogard et
al. (2008), investigated the spatial and temporal variability
of dissolved oxygen in the southern California Current
°퐶
1
°퐶
∆
푇푠 (
) =
× ꢒ ∆푇푠,푗,푖 ( )
푦ꢇꢈꢉ
ꢊ3ꢋ
푦ꢇꢈꢉ
ꢑꢑ
푖,푗
푚ꢀ
푚ꢀ
ꢔ
푦ꢇꢈꢉ
1
ꢔ
푦ꢇꢈꢉ
∆
퐷푂 ꢓ
ꢕ =
× ꢒ ∆퐷푂 ꢓ
ꢕ
ꢊ4ꢋ
ꢊꢑꢋ
푠
11
푠
°퐶
푇 (
푦ꢇꢈꢉ
1
°퐶
)
푦ꢇꢈꢉ
∆
) =
× ꢒ ∆푇 (
푠
11
푠
System in a 22-year (1984-2006), and a large dissolved
휇푚표푙
oxygen up to 2.1 푘ꢀ.푦 were observed [10].
Also,
where Δ푇푠,푗,푖, Δ퐷푂푠,푗,푖 are the rate of temperature and DO
changes (respectively) in station number “s” in year “j”
towards year “i". for each station number of 55 values
existed for Δ푇푠,푗,푖 and 55 values for Δ퐷푂푠,푗,푖 these values are
shown in Table 4 and 5.
significantly oxygen decline over a 50-year (1960-71 and
998-2011) from Newport hydrographic line off central
1
Oregon, one of the few locations in the northeast Pacific, was
reported by Pierce et al. (2012) and suggested that subarctic
influence along 휎 26.6 [11]. Grantham et al. (2004), found
휃
that in 2002, cross-self transects revealed the development
of the abnormally strong flow of subarctic water into the
California Current system [12].
3 Result and discussion
In the present study, temperature changes trending and
dissolved oxygen concentration have been investigated.
After that, the speed of temperature changes in degree and
dissolved oxygen concentration in mg/L were calculated in
each year. To achieve these terms, as can be seen in equation
1, the average of temperature and dissolved oxygen in one
year compared with the same items in other years. An 11-
year period of time (2007-2017) was considered.
Consequently, the number of differences between year i and
j are equal to:
Meinvielle and Johnson (2013), investigated decreasing
dissolved oxygen concentration, increasing warmth and
salinity, and decreasing potential vorticity, using historical
data from the World Ocean Database from 1950 to 2012 in
the California Current System [13]. Kwon et al. (2016),
studied central mode waters in the North Pacific, defined as
neutral densities of 25.6-26.6, and suggest that the area
through which the oxygen-rich mixed layer is detrained into
the thermocline varies on a decade basis, with a connection
to the Pacific Decadal Oscillation (PDO) [2]. Ren et al.
(
2016), presented the hydrographic cruise observation of
declining dissolved oxygen collected along CalCOFI line
6.7 off of Monterey Bay, in the central California Current
11
2
11!
(
) =
= ꢑꢑ
ꢊ6ꢋ
2! × 9!
6
∆
ꢖ
region. Results reported a significant decline in dissolved
oxygen occurring in the northern, central, and southern
California Current region, and between 1998 and 2013,
Therefore, in both cases, the temperature’s speed ꢊ
ꢋ,
ꢆ푒푎푟
ꢗꢘ
∆
and the speed of Dissolved oxygen concentration ꢊ
ꢋ, are
ꢆ푒푎푟
ꢁꢂꢃꢄ
°
ꢙ
dissolved oxygen decreased at the mean rate of 1.92
which means a 40% drop from initial concentration [14].
ꢅ푔.ꢆ푒푎푟
increasing by the rate of ꢊ
ꢋ. Advantages of this method,
ꢆ푒푎푟
which is using for the first time to calculating the mentioned
parameters, is the temperature and dissolved oxygen of the
whole period is comparing with all previous years not only
with the year before, and consequences would be expressed
on average. With regard to the average temperature in all
stations (17.4°C) and table 3, there is a 0.2 mg/L difference
between DO at 17.4 and 18 degrees. It takes 30 years to
temperature from 17.4 to 18 provided that the increasing rate
of temperature continues as the same range is now (0.02
degree per year). Also, dissolved oxygen should decrease
0.12 mg/L, but the results are shown that DO decreases
speed is 0.138 mg/L per a year which means over the next
30 years the lessen dissolved oxygen is going to be 4 mg/L
or so that is 30 times lower than what is expected due to the
temperature rising. Hence, in addition to increasing
temperature on a yearly basis, the rivers in this area of the
America is getting polluted to BOD and COD. The increase
in the sum of BOD and COD is indicating in equation 7 to
2
Data
This study investigated the changes in DO level and T
value. Data obtained from 10 different water quality
monitoring stations (Table 1) in California, USA. These data
consist of 4018 sets of data that belong to 11 years: 1/1/2007
to 31/12/2017 (for each station) that include the daily mean
values of DO concentration (mg/L) and T (ºC). for each
station some of the data missed (around 3% of DO data and
2
% of T data, see Table 1) these data reproduced by
placement them with an average of existed data that day but
in other years. After reproducing the missing data annual
average of data calculated for each year and each station, and
rate of DO and T change calculated by the following
procedure (equation 1 to 5):
°
퐶
푇푠,푗ꢊ°퐶ꢋ − 푇푠,푖ꢊ°퐶ꢋ
ꢌ − ꢍ
∆
푇푠,푗,푖 (
) =
, 2007 ≤ ꢍ, ꢌ ≤ 2017, ꢌ > ꢍ
ꢊ1ꢋ
푦ꢇꢈꢉ
1
3 ꢍ푛 30 푦ꢇꢈꢉꢚ.
ꢎꢏ
ꢎꢏ
퐿
ꢐ
퐿
∆
퐷푂 (
) = × ∑푖,푗 ∆퐷푂푠,푗,푖
ꢊ
ꢋ
(2)
푠
ꢆ푒푎푟
55
ꢆ푒푎푟
8
44