The
study of arsenic presence in soils is important due to its environmental,
agricultural, and health implications. Arsenic, one of the most toxic and
abundant elements in the Earth's crust, can be present in water, air, and s=
oil,
with its inorganic form being the most dangerous to living organisms. In vo=
lcanic
regions such as the cantons of Mocha, Quero, Cevallos, Pelileo, and especia=
lly
Penipe, which have been affected by volcanic emissions, natural sources of =
this
element exist, posing a potential contamination risk to agricultural soils =
and
the crops grown there. This contamination becomes a threat to human health,
particularly for residents of the area who are exposed to the accumulation =
of
heavy metals through the food chain.
Arsenic
(As)
is one of the most abundant elements in the Earth's crust, present in trace
amounts in rocks, soils, water, and air. In the environment, it is found in=
its
inorganic forms As³⁺ and As⁵⁺, with the former being
more toxic (Gomez-Caminero et al., 2001; Carbonell=
‐Barrachina
et al. 2009; Carbonell et al., 1996). Its toxi=
city
and ability to transform between less and more hazardous species make it a
contaminant of environmental, nutritional, and evolutionary concern (Medina=
-Pizzali
et al., 2018; Velasco, 2018; Fano et al., 2019). In Latin America, volcanic
activity represents a significant natural source of arsenic, especially in
countries like Ecuador, where volcanic emissions and hydrothermal fluids can
contaminate soils and water bodies (Carracedo & Rodríguez, 1993;=
Neaman
et al., 2024).
Additionally,
human activities such as metal smelting, pesticide use, and fossil fuel
combustion have increased its presence in the environment (Medina-Pizzali et
al., 2018). Arsenic has been detected in various foods, including seafood,
meats, rice, and algae, indicating its incorporation into the food chain (<=
/span>Gomez-Caminero
et al., 2001). Chronic exposure has been linked to multiple diseases, such =
as
skin, lung, bladder, and prostate cancers, as well as genetic alterations,
kidney problems, and adverse effects on fetal development (Hall et al., 199=
9; Secretaría Nacional de Planificación y Desarroll=
o [SEMPLADES], 2013). In
agricultural soils, arsenic dynamics depend on factors such as pH, organic
matter, and texture, which influence its absorption by plants and subsequent
transfer to humans (Almberg et al., 2017; Turcios, 2010). Therefore,
organizations such as the WHO and national regulations like INEN and TULSMA
have established maximum permissible limits for arsenic in water, food, and
soils to protect public health and the environment (Ecuadorian
Institute for Standardization [INEN],
2011; Food and Drug Administration<=
span
style=3D'mso-bookmark:_Hlk81775515'> [FDA], 2025; Rodr&iacut=
e;guez-Eugenio,
2019).
This
study aims to evaluate the concentration of arsenic in soils affected by
volcanic ashfall, with the goal of generating scientific information that
contributes to environmental management, food security, and the protection =
of
public health.
It is important to
understand some definitions related to the literature review conducted, to =
gain
a better understanding of arsenic (As) as a chemical element widely
distributed in nature, capable of existing in various chemical forms, both
organic and inorganic. Its toxicity depends on its oxidation state, origin,=
and
potential risks to human beings. This complex interaction between natural a=
nd
anthropogenic sources makes arsenic a priority contaminant in environmental=
and
public health studies.
1.1. Arsenic
Arsenic (As) is one of the most abundant elements =
on
earth and it can be found as traces in rocks, soil, water, and air. The
oxidation states of arsenic are the following: As3-, As0,
As3+, and As5+. However, only As3+ and As<=
sup>5+
are found in the environment. The main organic compounds containing arsenic=
are
arsenobetaine, salts from trimethylarsine acid, arsenic-containing
carbohydrates, and arsenocholine. These types of compounds are less toxic t=
han
inorganic compounds and compounds formed with As3+ are more toxic
than compounds formed with As5+. However, there is the possibili=
ty
of the conversion from less toxic to more toxic species in nature (Gomez-Caminero et al., 2001). Arsenic has been
studied largely as a pollutant in the environment due to its presence at the
ecological, nutritional and evolutional levels (Medina-Pizzali et al=
.,
2018; Velasco, 2018; Fano et al., 2019).
1.2. Arsenic in the
environment
Geothermal fluids and volcanic emissions are
sources of arsenic capable of contaminating soil and water. Since there are
many active volcanoes in Latin America, millions of people are threatened by
these natural phenomena. Numerous volcanoes, hot springs, geothermal wells,=
and
volcanic fumaroles are found in the Pacific region of Latin America in the
countries of Mexico, Guatemala, Honduras, El Salvador Nicaragua, Costa Rica,
Ecuador, Bolivia, and Chile. These geothermic systems contain high
concentrations of As and other geothermic elements such as Li and B.
Concentrations of As >73.6 mg L-1 have been found in water wi=
th
high concentration of NaCl and low concentration of sulfates; the As
concentration in water is due to the gases produced in the volcanoes and
leachates are produced when volcanic rocks the water (Carracedo & Rodríguez, 1993).
Arsenic concentration in seawater varies from=
1-2
µg L-1. However, in the presence of volcanoes or mineral
sulfur deposits As concentration has been found to be as high as 12 µ=
g L-1.
Meanwhile, in superficial and ground waters As concentration varies from 1-=
10
µg L-1. On the other hand, arsenic concentration in air is
only around 0.02- 4 ng m-3 in rural areas. In natural sources of=
As,
concentration can reach up to 12 ng m-3 (Gomez-Caminero et al., 2001)<=
!--[if supportFields]>.
Arsenic and its derivatives are found in the
environment due to anthropogenic activities such as the casting of nonferro=
us
metals, the use of fossil fuels and the use of pesticides ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemDa=
ta":{"DOI":"10.17843/RPMESP.2018.351.3604","I=
SSN":"1726-4634","abstract":"Arsenic
is an element that is widely distributed throughout the environment. Its
compounds are mainly in the state of pentavalent and trivalent oxidation; a=
nd
in inorganic and organic forms. Arsenical species vary in their degree of
toxicity, with inorganic compounds being more toxic than organic and trival=
ent
compounds more toxic than pentavalent compounds. There would be interconver=
sion
between the less toxic species and other more toxic species and the cooking=
and
processing methods could affect it. Arsenic is a carcinogenic agent and cau=
ses
multiple negative effects on human health in the short and long term.
Non-occupational human exposure to arsenic occurs mainly through water and
food. The regulation is variable for each country and is based on WHO
standards, the Codex Alimentarius, and the European Union. Many studies foc=
us
on determining the total arsenic content but do not identify arsenical spec=
ies
in foods. Globally, fish and seafood, chicken, meat, rice, and seaweed have
high levels of arsenic. In Peru, there are few studies on total arsenic con=
tent
and arsenical species in food despite the fact that we have areas with high
levels of environmental contamination. The objective of this review is to
discuss exposure to arsenic through food and water intake, related regulati=
ons,
toxicity, consequences on human health and main foods that contribute to its
intake.","author":[{"dropping-particle":"&quo=
t;,"family":"Medina-Pizzali","given":"Ma=
ría","non-dropping-particle":"","parse=
-names":false,"suffix":""},{"dropping-particl=
e":"","family":"Robles","given"=
;:"Pamela","non-dropping-particle":"","p=
arse-names":false,"suffix":""},{"dropping-par=
ticle":"","family":"Mendoza","given=
":"Mónica","non-dropping-particle":"&q=
uot;,"parse-names":false,"suffix":""},{"=
dropping-particle":"","family":"Torres",=
"given":"Celeste","non-dropping-particle":&qu=
ot;","parse-names":false,"suffix":""}],&=
quot;container-title":"Revista
Peruana de Medicina Experimental y Salud
Publica","id":"ITEM-1","issue":"1&q=
uot;,"issued":{"date-parts":[["2018","1&=
quot;,"1"]]},"page":"93-102","title"=
;:"Ingesta
de arsénico: el impacto en la alimentación y la salud
humana","type":"article-journal","volume"=
;:"35"},"uris":["http://www.mendeley.com/documents=
/?uuid=3D8788d0c3-649c-3f26-96be-5d1c88d0ac15"]}],"mendeley"=
:{"formattedCitation":"(Medina-Pizzali
et al.,
2018)","plainTextFormattedCitation":"(Medina-Pizzali et
al., 2018)","previouslyFormattedCitation":"(Medina-Pizz=
ali
et al.,
2018)"},"properties":{"noteIndex":0},"schema&=
quot;:"https://github.com/citation-style-language/schema/raw/master/cs=
l-citation.json"}(Medina-Pizzali et al., 2018). Arsenic has been found in marine organisms and less proportions in
terrestrial and freshwater organisms. Food such as seafood, chicken, beef,
rice, and seaweed has proven to have high levels of As (Gomez-Caminero et al., 2001)<=
!--[if supportFields]>. Table 1 contains
information about the types of arsenic compounds found in several types of
foods.
Table 1
Main arsenic compou=
nds
related to food=
![3D"https://www.scielosp.org/media/assets/rpmesp/v35n1/1726-4642-rpmesp-=](3D"03-3EvaluationofenvironmentalpollutionL.Carrera-Beltran(2)_archivos/=)
Reference: Medina-Pizzali et al. (2018)
<=
![if !supportLists]>1.3. Arsenic and human hea=
lth
Arsenic is one of the most toxic elements fou=
nd
in the environment which has negative effects on the ecosystem and human
health. Many health problems in pregnant women are associated with the pres=
ence
of As in countries such as Taiwan, China, India, Argentina, Brazil, Chile,
Mexico, among others (Medina-Pizzali et al., 2018; Sánchez, 2017).
Studies performed in drinking water by the
application of biomarkers in the exposure to As, genetic susceptibility and
gene toxicity in Mexico, Chile, Argentina, Brazil, Colombia, Ecuador and
Uruguay between the years of 2011 and 2018 have shown the influence of As in
bladder, breast, larynx, prostate, skin and lung cancer. Moreover, As has
influenced health problems such as the reduction on cognitive performance, =
risk
factors on the uterus, type 2 diabetes, kidney injuries, lung problems in
infants, underweight newborns, low gestational age, anemia, increase on
apoptosis, damage to DNA and alteration of genes and proteins (Hall et al., 1999; SEMPLADES,
2013).
<=
![if !supportLists]>1.4. Arsenic in soil<=
/o:p>
Vegetables contain essential nutrients such as
proteins, vitamins, minerals, and fiber. Some of these nutrients are absorb=
ed
by plants and their basic composition is made by elements and compounds whi=
ch
can be toxic causing negative effects on the plants. Furthermore, toxins can
reach humans through the food chain (Sánchez, 2017).
Minerals in soil have a complex dynamic of
absorption and desorption dependent on the type of soil, pH, organic materi=
al,
humus content, index properties of soil and treatments performed on soils t=
hat
involve the application of fertilizers and other minerals ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemDa=
ta":{"DOI":"10.1016/J.ENVRES.2017.05.010","IS=
SN":"0013-9351","abstract":"Background
Arsenic in drinking water has been associated with adverse reproductive
outcomes in areas with high levels of naturally occurring arsenic. Less is
known about the reproductive effects of arsenic at lower levels. Objectives
This research examined the association between low-level arsenic in drinking
water and small for gestational age (SGA), term low birth weight (term LBW),
very low birth weight (VLBW), preterm birth (PTB), and very preterm birth
(VPTB) in the state of Ohio. Methods Exposure was defined as the mean annual
arsenic concentration in drinking water in each county in Ohio from 2006 to
2008 using Safe Drinking Water Information System data. Birth outcomes were
ascertained from the birth certificate records of 428,804 births in Ohio fr=
om
the same time period. Multivariable generalized estimating equation logistic
regression models were used to assess the relationship between arsenic and =
each
birth outcome separately. Sensitivity analyses were performed to examine the
roles of private well use and prenatal care utilization in these associatio=
ns.
Results Arsenic in drinking water was associated with increased odds of VLBW
(AOR 1.14 per µg/L increase; 95% CI 1.04, 1.24) and PTB (AOR 1.10; 95=
% CI
1.06, 1.15) among singleton births in counties where <10% of the populat=
ion
used private wells. No significant association was observed between arsenic=
and
SGA, or VPTB, but a suggestive association was observed between arsenic and
term LBW. Conclusions Arsenic in drinking water was positively associated w=
ith
VLBW and PTB in a population where nearly all (>99%) of the population w=
as
exposed under the current maximum contaminant level of 10 µg/L.
Current regulatory standards may not be protective against reproductive eff=
ects
of prenatal exposure to
arsenic.","author":[{"dropping-particle":"&qu=
ot;,"family":"Almberg","given":"Kirsten
S.","non-dropping-particle":"","parse-names&q=
uot;:false,"suffix":""},{"dropping-particle":=
"","family":"Turyk","given":"M=
ary
E.","non-dropping-particle":"","parse-names&q=
uot;:false,"suffix":""},{"dropping-particle":=
"","family":"Jones","given":"R=
achael
M.","non-dropping-particle":"","parse-names&q=
uot;:false,"suffix":""},{"dropping-particle":=
"","family":"Rankin","given":"=
Kristin","non-dropping-particle":"","parse-na=
mes":false,"suffix":""},{"dropping-particle&q=
uot;:"","family":"Freels","given":&=
quot;Sally","non-dropping-particle":"","parse=
-names":false,"suffix":""},{"dropping-particl=
e":"","family":"Graber","given"=
;:"Judith
M.","non-dropping-particle":"","parse-names&q=
uot;:false,"suffix":""},{"dropping-particle":=
"","family":"Stayner","given":"=
;Leslie
T.","non-dropping-particle":"","parse-names&q=
uot;:false,"suffix":""}],"container-title":&q=
uot;Environmental
Research","id":"ITEM-1","issued":{"=
date-parts":[["2017","8","1"]]},"pa=
ge":"52-59","publisher":"Academic
Press","title":"Arsenic in drinking water and adverse b=
irth
outcomes in
Ohio","type":"article-journal","volume":=
"157"},"uris":["http://www.mendeley.com/documents/=
?uuid=3D3c9d0350-2930-3525-81d8-56f9f0ebdf21"]}],"mendeley":=
{"formattedCitation":"(Almberg
et al., 2017)","plainTextFormattedCitation":"(Almberg et
al., 2017)","previouslyFormattedCitation":"(Almberg et =
al.,
2017)"},"properties":{"noteIndex":0},"schema&=
quot;:"https://github.com/citation-style-language/schema/raw/master/cs=
l-citation.json"}(Almberg et al., 2017).
The metals in the soil have diverse sources s=
uch
as fertilizers, atmospheric deposition, volcanic eruptions, and natural ero=
sion
of rocks. These metals may be absorbed by plants at high rates which involv=
e a
high concentration of metals. Then, the metals may be transferred to
herbivorous animals during feeding (Khan et al., 2015).
Heavy metals from the soil, water or air are
bio-accumulated in plants through roots or via foliar; plants with big foli=
ar
areas and short stems can accumulate a higher concentration of metals.
Meanwhile, other plants can resist higher concentrations of metals and
chemicals. These capabilities depend on the type and species of the plants =
(Turcios, 2010).
Contaminated soils are problematic due to the=
ir
incorporation into agricultural products that can reach humans through diet.
Therefore, it is important to consider the maximum content of metals in the
soil for agricultural purposes which is 12 mg kg-1 (As) <=
/span>(Besoain et al., 1995; Rodríguez-Eugenio, 2019).
1.5.=
Arsenic regulations
In the 1990s, the World Health Organization
reduced the acceptable limits for As in drinking water from 50 µg L-1
to 10 µg L-1 (Carrión, 2010=
; Lozano, 2014). Regar=
ding
food there are differences such as concentration limits established in the
Codex Alimentarius. For example, oils and fats have a limit of 0.1 mg kg-1,
mineral water has a limit of 10 µg L-1, milled rice has a
limit of 0.2 mg kg-1,
and table salt must not have more than 0.5 mg kg-1 of As =
(Food and Drug Administration [FDA], 2025; Jaishankar et al., 20=
14; Sánchez, 2017;=
Sanchez, 2018)=
.
In Ecuador INEN establishes the maximum
concentration of As in drinking water as 0.01 mg L-1. This
regulation is found with the following title: “Anexo
1. NTE INEN 1108 (2011) sobre agua potable” (INEN, 2011) about drinking water
requirements. Meanwhile, TULSMA in its book VI, annex I published on May 4t=
h, 2015,
contains the Standard for Environmental Quality and Effluents Discharge:
Resource Water, in which the As concentration limits depend on how water is
going to be used. In the same book, annex II, the As concentration limits f=
or
soil are established as 12 mg kg-1.
This study was undertaken to provide
comprehensive review of the previous studies on the presence of arsenic in
soils and agricultural products because of the ash fall due to the eruption=
of
the Tungurahua volcano - Ecuador, and the environmental consequences and the
health of the population affected.
<=
![if !supportLists]>=
2. Methodology=
The methodology of this revi=
ew
included defining the topic and establishing the study objectives.
Subsequently, the scientific databases to be used were selected, including
Scopus, Web of Science, and SciELO. Keywords and Boolean operators for the
search were then defined, such as arsenic, volcanic ash, Tungurahua, Latin
America. A systematic search was conducted in the selected databases, and t=
he
information found was organized using Mendeley. The collected data was then
classified, analyzed, and synthesized by considering the key findings of ea=
ch
study and comparing them. The ultimate step was the writing of the article.=
<=
![if !supportLists]>3. &n=
bsp;
Discussion=
This document addre=
sses
the presence of arsenic (As) in Latin America, a subject of increasing
scientific interest due to its significant impact on public health and the
environment (Bundschuh & Litter, 2010). Recent studies conducted in Ecu=
ador
have identified notable concentrations of this metalloid, particularly in a=
reas
influenced by volcanic activity (Rodríguez, 2021; Lillo, 2003). One =
of
the most prominent cases is that of the Tungurahua volcano, whose eruptive
activity has contributed to the dispersion of arsenic-rich volcanic ash. Th=
is
phenomenon has raised concerns about the potential contamination of soil, w=
ater
sources, and agricultural products in surrounding areas, affecting communit=
ies
that rely directly on these natural resources (Narvaez, 2014). T=
he aim
of overarching is to understand the relationship between volcanic activity =
and
arsenic presence to assess environmental risks and inform the development of
effective mitigation strategies.
<=
![if !supportLists]>3.1.
Research on As in Latin America
Studies performed in countries such as Chile,
Mexico, Argentina, Bolivia, Brazil, Colombia, Ecuador, and Uruguay between =
2011
and 2018 have found negative effects of As in human health as shown in the =
As
and human health section. Countries in Latin America have many active volca=
noes
that produce geothermic fluids (water, gas) and together with volcanic rocks
contaminate groundwater and soil with moderate to high concentrations of As=
(Guerrero, 2019). Volcanic ash has also been found to be a source of As in different
geographic areas of Latin American countries (Polo, 2009; Bissen & Frimmel, 2003). Levels of As in Latin America have been found to be > 50
μg L-1 reachi=
ng
about 2000 μg L-1 which is 200 times higher than the maximum
limits established by the World Health Organization (WHO) ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemDa=
ta":{"ISSN":"0028-646X","author":[{"=
;dropping-particle":"","family":"Zhao",&=
quot;given":"F
Jၞ=
0;","non-dropping-particle":"","parse-na=
mes":false,"suffix":""},{"dropping-particle&q=
uot;:"","family":"Ma","given":"=
;J
Fၞ=
0;","non-dropping-particle":"","parse-na=
mes":false,"suffix":""},{"dropping-particle&q=
uot;:"","family":"Meharg","given":&=
quot;A
A","non-dropping-particle":"","parse-names&qu=
ot;:false,"suffix":""},{"dropping-particle":&=
quot;","family":"McGrath","given":"S
P","non-dropping-particle":"","parse-names&qu=
ot;:false,"suffix":""}],"container-title":&qu=
ot;New
Phytologist","id":"ITEM-1","issue":"=
;4","issued":{"date-parts":[["2009"]]},&=
quot;page":"777-794","publisher":"Wiley
Online Library","title":"Arsenic uptake and metabolism =
in
plants","type":"article-journal","volume"=
;:"181"},"uris":["http://www.mendeley.com/document=
s/?uuid=3D890c908b-5418-4397-9da2-65e13a021c5e"]}],"mendeley"=
;:{"formattedCitation":"(Zhao
et al., 2009)","plainTextFormattedCitation":"(Zhao et a=
l.,
2009)","previouslyFormattedCitation":"(Zhao et al.,
2009)"},"properties":{"noteIndex":0},"schema&=
quot;:"https://github.com/citation-style-language/schema/raw/master/cs=
l-citation.json"}(Zhao et al., 2009).
In Peru, studies have
shown the presence of As in Tumbes River at concentrations of 200 ug kg-1;
this river is close to a rice production área (Lin & Puls, 2000)=
. Also in Peru, in the city of Tacna=
, As
has been present in the Sama and Locumba rivers at concentrations higher th=
an
0.01 mg L-1 which is the maximum limit allowed. In the same area,
the concentration of As was tested in the urine of the adult population; 80=
.3%
of the samples had an As concentration higher than the limits established by
the WHO (Ale-Mauricio et al., 2018).
In Chile, there has been gene methylation due=
to
the exposure of newborns and infants to As, lead (Pb), phenols, and phthala=
tes.
This exposure has caused several organic diseases and changes in neurologic=
al
behavior when adulthood is reached (Ale-Mauricio et al., 2018). In Bolivia, the water from Lake Poopó
has been found to have a high concentration of inorganic As which is one of=
the
most toxic and carcinogenic elements in nature (Tchernitchin & Gaete, 2018).
<=
span
style=3D'mso-bookmark:_Hlk31438289'>3.2. Presence of As in Ecuador=
The presence of As in Ecuador is mainly relat=
ed
to hydrothermal processes in volcanic regions such as the Papallacta basin =
and
lagoon, and the Wells of Tumbaco and Guayllabamba (Sánchez, 2017).
Studies performed in various samples of water=
and
soil have shown values of 10 ug L-1, and 4.48 ± 3 mg kg-1,
respectively. In rice biomass As concentration has varied depending on the
parts of the plant. Rice grains showed values of 0.042-0.125 mg kg-1,
leafs showed values of 0.123- 0.286 mg kg-1, and stems showed va=
lues
of 0.091-0.201 mg kg-1 (Gomez-Caminero et al., 2001).
Another study related to As was the “Designing
a bacterial biosensor for arsenic detection in water solutions,” this sensor could detect As
concentrations between 0.01-0.08 ppm with an error of only 2.8% in comparis=
on
with measurements performed by ATOMIC ABSORPTION SPECTROSCOPY (AAS) (Daneshpour
et al., 2014).
As has also been foun=
d in
water at the Biological Reserve of Limoncocha in concentrations of 1 ppb wh=
ich
complies with the Ecuadorian Legislation (0.05 mg L-1). Although,
soil and sediments contained As it was concluded that this form of As may h=
ave
had low solubility in water (Carrión , 2010)=
.
Metals and As were
determined in agricultural soils watered with residual water from natural a=
nd
anthropogenic origins. The geo-accumulation and enrichment factors were
determined based on the Cd, Pb, Ni, Cu, Co, Cr, Zn and As contents in Atoya=
c,
Zahuapan, and Alto Balsas rivers, as well as in the Valsequillo Canal (Baque-Mite=
et
al., 2016). Anthropog=
enic
contamination was found in agricultural soils in the Alto Balsas sub-basin =
(Lozano, 2014).
Arsenic has also been
studied in the cities of Cuenca and Azogues. The authors could not find As =
in
the groundwater and drinking water of these two cities. However, many rivers
located in this area contained a certain amount of As; the rivers were the
following: Tomebamba, Yanuncay, Tarqui, y Machangara <=
!--[if supportFields]>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemDa=
ta":{"abstract":"Se
determina la presencia de Arsénico en fuentes de agua en las ciudade=
s de
Cuenca y de Azogues y se evalúa el posible riesgo toxicológico
por el consumo del agua sin tratamiento previo; se analiza el efecto
ecotoxicológico que puede producirse en los sembríos a
través del agua de riego y en los animales que la beben en dichas zo=
nas.
Se estableció un programa de monitoreo con dos campañas duran=
te
los meses de agosto, septiembre, octubre y noviembre del año 2017, en
los ríos Tomebamba, Yanuncay, Tarqui, y Machángara; en
acuíferos dentro de la Universidad de Cuenca y en el páramo de
Quimsacocha en la ciudad de Cuenca; y en la ciudad de Azogues, para los
ríos Burgay y Tabacay. Los monitoreos abarcan dos períodos
climáticos representativos. En los ríos se ubicaron estacione=
s de
control definidas, y se evaluó el riesgo toxicológico en todas
las muestras que presentaron un valor positivo para el Arsénico. \nSe determinan algunos indicadore=
s de
calidad físico-química como: pH, color, turbiedad, conductivi=
dad
y temperatura, en cada fuente de abastecimiento, para establecer alguna
relación con la presencia de Arsénico, cuyos valores se compa=
ran
con los establecidos en la Normativa Ecuatoriana TULSMA Texto Unificado de =
la
Legislación Secundaria del Medio Ambiente.\nLos resultados indican q=
ue
todos los ríos están contaminados con Arsénico, y que =
en
invierno, las concentraciones son mayores debido a un arrastre por
escorrentía. Los páramos y los acuíferos están
libres de este elemento.\nLa evaluación en todas las fuentes, indica=
que
no hay riesgo toxicológico para el abastecimiento, ni riesgo
ecotoxicológico que limite los usos del agua","author"=
;:[{"dropping-particle":"","family":"Vel=
asco
Heras","given":"María
Eugenia","non-dropping-particle":"","parse-na=
mes":false,"suffix":""}],"id":"ITEM=
-1","issued":{"date-parts":[["2018"]]},&=
quot;title":"Evaluación
del riesgo toxicológico por la probable presencia de arsénico=
en
fuentes de agua para consumo humano, en las ciudades de Cuenca y
Azogue","type":"article-journal"},"uris"=
:["http://www.mendeley.com/documents/?uuid=3Dfd776c9d-099c-35c4-951a-5=
57e835870e0"]}],"mendeley":{"formattedCitation":&q=
uot;(Velasco
Heras, 2018)","plainTextFormattedCitation":"(Velasco He=
ras,
2018)","previouslyFormattedCitation":"(Velasco Heras,
2018)"},"properties":{"noteIndex":0},"schema&=
quot;:"https://github.com/citation-style-language/schema/raw/master/cs=
l-citation.json"}(Velasco, 2018).
Arsenic was studied in
soils and drinking water in Papallacta parish. The study found out that
drinking water contained 11-24 μg L-1 of As which is higher
than the parameters established by the WHO (10 μg L-1). This
high concentration of As may have been related to the presence of thermal
springs and diluted volcanic gases. In the case of soils, As concentration =
was
higher than 12 mg kg-1 which exceeds the limits established in t=
he
Unified Text of the Secondary Legislation of the Environment of Ecuador (Ministerio
del Ambiente de Ecuador [MAE],=
2015;
Besoain et al., 1995). Finally, the sediments of the Papallacta Lagoon =
had
concentrations of As lower than 102 mg kg-1 (Jolliffe, 1993), higher than 5.9 mg kg-1, established =
in
the Canadian Council of Ministers of the Environment [=
CCME],
2001).
Treatment of As has a=
lso
been studied in Ecuador. One study applied cocoa-bean husk for the adsorpti=
on
of Sb (III) and As (III); this material was more efficient than other
lignocellulosic biomass (Cullen & Reimer, 1989). Another study used nanofiltration =
with
an NF 270 membrane at 90 and 100 psi of pressure to reduce the concentratio=
n of
As from drinking water. This treatment reduced the As concentration to 0.05=
mg
L-1 which is an acceptable value in the environmental regulation=
s of
Ecuador for drinking water (Bissen & Frimmel, 2003)<=
/span>.
<=
span
style=3D'mso-bookmark:_Hlk31438289'>3.3.
Arsenic and volcanic ASH
Volcanic ash is a source of toxic metals for
water, especially arsenic (Fano et al., 2019). Arsenic is dispersed naturally in the
atmosphere at high temperatures due to the burning of vegetation, burning of
fossil fuels and volcanic eruptions; out of all the sources, volcanic erupt=
ions
contribute 60% of all the atmospheric flux of As. Arsenic is dispersed in t=
he
atmosphere as particulates in the form of trioxide of As. The latter return=
to
the ground by dry or humid deposition (McClintock et al., 2012; Medina-Pizzali et al., 2018).
Using X-Ray Absorption Fine Structure (XAF=
S)
the oxidation state of As and its coordination number has been determined in
the volcanic ash of different natures (recent, old, and in loess chacopampe=
anos
sediments). Most of the As had an oxidation state of 5+ in the loess sedime=
nts.
Meanwhile, in volcanic ash, As has oxidation states of 1- and 3+. The loess
sediments (As5+) could be in the form of arsenates adsorbed in
ferric =
oxyhydrox=
ides.
The ashes from recent eruptions could be associated with arsenic-containing
pyrites and there might have been impurities of As3+ in the structure in the form =
of oxyhydroxides. In the ashes from old eruption, the dominant
oxidation state is 3+ and in lesser quantity As5+ (Khan, et al., 2015; Khan et al., 2020).
<=
span
style=3D'mso-bookmark:_Hlk31438289'>3.4. Tungurahua volcano
The Tungurahua volcano has a height of
approximately 5023 meters (Briceño et al., 2020), located in the Andes range at 140km south of
Quito. The most violent eruption took place in 2006 in which lava columns
reached 8km of height and there were huge quantities of hot rocks and ash
affecting the cities of Ambato, Pelileo, Cevallos, Quero, Mocha, Tisaleo,
Riobamba and Penipe (Hall et al., 1999). The eruption of the volcano destroyed most =
of
the crops of the region and changed the epidemiological map of the populati=
on (Guerrero, 2019).
The last eruptive process of the volcano took
place from 1999-2014 discharging and depositing almost 0.13km of tephra to =
the
west and southwest of the volcano. Most of the tephra was discharged in the
following years: 2001, 2006 and 2014. The Tungurahua volcano is a dangerous
geological zone affecting all the cities around it. However, the volcano co=
uld
work as a natural lab to study the effects of long-lasting eruptions (Bissen & Frimmel, 2003). Based on the mineralogy and size of the ash discharged by the volc=
ano,
human health could be severely affected (Coral et al., 2019)<=
!--[if supportFields]>.
<=
![if !supportLists]>3.5.
Contamination by As in the influence zone of the Tungurahua volcano
This sect=
ion
considers research studies on the presence of As in soils, biomass, and
agricultural products in the influence zone of the Tungurahua volcano. The
studies are scarce and most of them were done 7 years before the end of the
eruption process.
Polo (200=
9)
studied the concentration of As in potatoes (Solanum tuberosum), carrots
(Daucus carota) and raw milk in zones close to the Tungurahua volcano. The
levels of As in this study were below 0.1 mg kg-1 which complies
with the Codex
Standard 193-1995 of Ecuadorian
National Institute of Standardization (INEN, 2013), limits for As in food.<=
o:p>
Carri&oac=
ute;n
(2010) studied the concentration of As in potatoes (Solanum tuberosum), corn
(Zea mays) and raw milk in Guano and Penipe which are cities located in the
influence zone of the Tungurahua volcano. The concentrations of As in this
study were also below 0.1 mg kg-1, Lozano (2014) studied the concentrations of Cd and As in water sources affected =
by
the volcanic ash of the Tungurahua volcano. It was concluded that the
concentrations of these metals were within the acceptable limits establishe=
d in
TULSMA, book VI, and annex I.
<=
![if !supportLists]>4. &n=
bsp;
Conclusions
· =
Arsenic is considered a toxic metal or metalloid f=
ound
in nature in organic and inorganic compounds; the latter is more toxic than=
the
former. Arsenic in nature can be found as trivalent and pentavalent. Compou=
nds
containing trivalent As are more toxic than compounds containing pentavalent
As. However, there is the possibility of the conversion from less toxic to =
more
toxic species in nature.
· =
Metals such as As, Li, and B can be dispersed
naturally in the environment by processes involving elevated temperatures s=
uch
as hot springs, volcano fumes, geothermic wells, and volcanic eruptions. La=
tin
America is exposed to these metals due to the presence of various volcanoes=
in
the Pacific region.
· =
Arsenic and its derivatives are found in the
environment due to anthropogenic activities such as the casting of nonferro=
us
metals, the use of fossil fuels and the use of pesticides.
· =
High concentrations of As influence various diseas=
es
such as bladder, breast, larynx, prostate, skin, and lung cancer. The reduc=
tion
in cognitive performance, risk factors on the uterus, type 2 diabetes, kidn=
ey
injuries, lung problems in infants, underweight newborns, low gestational a=
ge,
anemia, increase in apoptosis, among others.
· =
In Latin America, As has been found at high
concentrations in soil, water, and agricultural products. The countries with
the most scientific production regarding As in different databases are Mexi=
co
and Argentina (Science Direct), Bolivia and Brazil (Scielo), Mexico (Web of
Science), Mexico and Argentina (Scopus).
· =
Volcanic ash and the concentration of As in the
atmosphere are closely related; the types of arsenic compounds in the
environment depend on the time that the eruption process has taken place. <=
o:p>
· =
No information was found in scientific databases a=
bout
the effects of the eruption process of the Tungurahua volcano in its influe=
nce
zone; most of the information was taken from undergraduate thesis collection
from universities. These studies were only developed in specific places and=
the
effects of As in food (potatoes, carrots, corn, and raw milk) were only stu=
died
in Cevallos town.
· =
The limited information in scientific databases of=
fers
an opportunity to study the effects of As in the environment and human
population in the influence area of the Tungurahua volcano.
<=
![if !supportLists]>=
4.1.
Acknowledgements
People or
institutions that have contributed in some way to research or drafting text,
whether through funding, knowledge contribution or research activity.<=
/o:p>
This research work has been carried out under the project entitled:
"Evaluation of bioavailability of heavy metals and their degree of
affectation in the areas of influence of the Tungurahua volcano and study of
bioaccumulation in soils and products derived from agricultural
activities", being carried out under the collaboration of the <=
/span>Grupo
Asociado de Investigación en Biotecnología, Ambiente y
Química (GAIBAQ) of the Escuela Superior Politécnica de Chimborazo- Ecuador and Grupo=
s de
Investigación en Mercados, Calidad y Seguridad Alimentaria (CSA=
) y
el Grupo en Investigación Aplicada en Agroquímica y Medio
Ambiente (GIAAMA) de la Universidad Miguel Hernández de
Elche-España,, for which the authors are grateful for their funding.=
5. Conflict of interest
The authors declare that there is no conflict of interest in relatio=
n to
the article presented.
6. Authors' Contribution Statement
All authors contributed significantly to the elaboration of the arti=
cle.
7. Financing costs
This research was funded entirely with the authors' own funds.<=
/o:p>
8.&n=
bsp;
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El
artículo que se publica es de exclusiva responsabilidad=
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