A water quality study with emphasis on pesticides in Shiroud river catchment in southern part of Caspian sea, Iran
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Date
2007
Authors
Shaban, Najafpour
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Abstract
Shiroud River of Iran was chosen in this study to monitor its water quality. The river
has a span of 32 km starting from Albourz mountainous and end up at the southern part of
Caspian Sea. The monitoring was done regularly over a period of one year (July 2003 to
June 2004) for different physico-chemical parameters (16) as well as organochlorine
pesticides (OCPs) compounds (15). A total of eight stations were selected for observation
in three different regions of the river (3 on the mountainous, 4 in plain and 1 in estuary).
The physico-chemical parameters were measured by ASTM method while organochlorine
pesticides (OCPs) were analyzed by GC-ECD according to US-EPA (508) procedure. The
complex data matrix (31 96) was treated with multivariate statistical techniques such as
factor analysis (FA) and discriminant analysis (DA). The physico-chemical parameters
were analyzed by FA and it was observed that there are six factors explaining up to
74.17% of the total variation in water quality. Six factors were observed for OCPs which
account for 73.39% of the total variation in water quality. DA was done to understand the
role of the stations (spatial) and seasonal variation (temporal) on water quality of the river.
DA gave four parameters (water temperature, conductivity, mean river depth and dissolve
oxygen) affording more than 86% correct assignations (return to the same station) in
spatial analysis, while eight parameters (water temperature, dissolved oxygen, silicate,
calcium ion, total hardness, total dissolved solids, orthophosphate and nitrate) to afford
more than 93% correct assignations in temporal analysis. DA showed nine compounds (
-BHC, -BHC, DDE, heptachlor, dieldrin, -BHC, endrin, -endosulfan and endrin
aldehyde) affording more than 80% correct assignations in spatial analysis, while five compounds ( -BHC, -endosulfan, -BHC, endosulfan sulfate and endrin aldehyde) to
afford 76% correct assignations in temporal analysis. Therefore, DA allowed reduction in
dimensionality of the large data set, defining a few indicator parameters responsible for
large variations. The variations of water quality are due to temperature, usage of different types
of fertilizer in agricultural lands, bio-chemicals activities and nutrients consumption by aquatic in
the river ecosystem. The number of compounds detected out of 15 OCPs components
during four seasons were 14 compounds with maximum fluctuation of -BHC (60μg/L) to
-endosulfan (5.2 μg/L) in spring, 10 compounds with maximum fluctuation of DDT and
DDE (25μg/L) to endosulfan sulfate (3.6μg/L) in summer, 6 compounds with maximum
fluctuation of aldrin (38 μg/L) to endrin (4.2 μg/L) in autumn and 11 compounds with
maximum fluctuation of heptachlor epoxide (50.8 μg/L) to dieldrin (3.2 μg/L) in winter.
However, according to the percentage of these chemicals were distributed in eight stations
from upstream to downstream classified as; (i)- moderate polluted (33 to 40%), (ii)-
polluted (47 to 54%), and (iii)- highly polluted (60 to 80%) regions. The variation of OCPs
caused by usage of chemicals in agricultural lands or by washed out of land soils from
rainfall discharged to the river by runoff. The OCPs compounds concentrations (5.2 to
60.0μg/L) in Shiroud River water were compared with European countries and US-EPA
standards for OCPs concentration in surface water (individual compound should not
exceed 0.1μg/L and sum of all pesticides <0.5μg/L) were considered very high.
Description
Ph.D
Keywords
Biological Science , Water quality