32
Tecnología y Ciencias del Agua
, vol. VIII, núm. 3, mayo-junio de 2017, pp. 27-37
Aburto-Medina
et al
.
, Prevalence of
Enterobacteriaceae
and contaminants survey in sediments of the Atoyac River
•
ISSN 2007-2422
along the river course and at the dam. Another
study has also determined low concentrations
of metals in the river waters (Cedeño, Téllez,
Pacheco, Rosano, &Ascencio, 2008) and the wa-
ter hyacinth (
Eichhornia crassipes
) has been sug-
gested as a phytoaccumulation species within
the Valsequillo dam (Cedeño
et al
., 2008). How-
ever, it has also been established that the con-
centrations of metals have accumulated in soils
throughout the time because of the irrigation
activities (Méndez-García
et al
., 2000) requiring
constant monitoring. Moreover, further studies
have established that these waters should not
be used for the irrigation of crops (Díaz
et al
.,
2005; Bonilla, Vázquez, Silva, & Cabrera, 2013)
and this is supported by a previous study where
long-term irrigation of soils with wastewater
in Germany caused significant heavy metal
contamination and a potential impact on the
underlying aquifers (Lottermoser, 2012).
Organic compounds detection
A total of 20 organic compounds were detected
in the river sediments of sampling point A1
and they are higher alkanes (C11-C16), esters,
organic acids, phenols, phthalates, among oth-
ers (table 5). The detection quality of most of
the compounds ranged from 80 to 98% (table
5). These compounds have been reported as
common contaminants of river waters (Pennell,
Abriola, & Weber, 1993; Gracia, Cortés, Sarasa,
Ormad, & Ovelleiro, 2000). Ten of the twenty
organic compounds detected in the sediment
sample are classified by the USEPA as chemicals
for potential endocrine disruptor screening and
testing and they include n-hexadecanoic acid,
octadecanoic acid, phenol, 2,4-bis(1,1-dimeth-
ylethyl)-, dodecane, cholestan-3-ol, (3.beta,
5.beta.)-, hexadecane, tridecane, undecane,
tetradecane and Cyclopenta[g]-2-benzopyran,
1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-
(USEPA, 2012). Compounds such as cholestan-
3-ol, (3.beta, 5.beta.), known also as coprostanol,
have been used as indicators in faecal pollution
source tracking (FST) to identify the origin(s) of
pollution in water, in areas where diffuse faecal
contamination are often marked by the co-
existence of human and animal sources (Roslev
& Bukh, 2011; Derrien
et al
., 2012). The presence
of coprostanol was correlated with the micro-
bial populations found in situ, as discussed
later. Moreover, a recent study detected other
persistent organic pollutants (POPs) in the river
sediments that included hexachlorocyclohexane
isomers, hexachlorobenzene, many polychlo-
rinated biphenyl congeners and plaguicides
such as DDT, DDE, mirex, and aldrin, (Juárez-
Santacruz
et al
., 2012). Therefore, the presence of
all these organic pollutants could pose a health
risk to the population because the crops in the
sub-basin and those located lands above the
dam are irrigated with these waters. Crops that
are irrigated with polluted waters may contain
pesticide residues; chlorpyrifos, cypermethrin,
and omethoate have been usually detected in
green vegetables such as spinach (Kobayashi
et
al
., 2011).
Table 4. The content of metals, semimetals and other elements in the Atoyac River sediments and comparison
with the USEPA limits.
Code
Elements (mg/kg)
As Ba
Ca Cu Fe
K Mn Mo Pb Rb Sr
Ti
Zn Zr
Av A1 <DL 417 157 019 54.8 21 554 5 881.7 407.2 <DL <DL 24.4 667.8 3 026.3 89.6 169.2
EPA 8
---
---
50 25000 ---
500 ---
60
---
---
---
200 ---
DL
14.5 27.1 70 42.7 113 200 107.3 10
20
10
10 209.5 61
8.1
Av: Average value; A: Atoyac River; EPA: USEPA Guideline (1977); DL: Detection limit.
As, Mo and Pb were below the detection limit.
