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Assessment of Human Health Risk of Chromium and Nitrate Pollution in Groundwater and Soil of the Matanza-Riachuelo River Basin, Argentina

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This study assesses hexavalent chromium [Cr(VI)] and nitrate (NO3⁻) in polluted groundwater and soil, and evaluates the impact on the health of the inhabitants of the Matanza-Riachuelo River basin, Argentina. Sixty groundwater samples and 18 soil samples were collected. Statistical analysis and Stiff diagrams were used for the hydrochemical characterization of the groundwater. A method developed by the United States Environmental Protection Agency for health risk assessment was applied to the Upper and the Puelche aquifers. The non-carcinogenic (NCR) and carcinogenic risks (CR) posed by Cr(VI) and NO3⁻ in groundwater via ingestion and dermal contact were determined in children and adults. The effect of Cr on children through ingestion, dermal contact and inhalation as a result of exposure to soil was also established. The results indicated that the Cr(VI) and NO3⁻ average values were 0.35 mg/L and 76 mg/L, respectively, in the Upper Aquifer, whereas the Cr(VI) average values were 1.41 mg/L and 38 mg/L for NO3⁻ in the Puelche Aquifer. Children and adults exposed to groundwater via ingestion and dermal contact faced acceptable NCR of NO3⁻, but unacceptable NCR and CR of Cr(VI). Water ingestion was the main exposure route; HQing = 4.15 and 4.07 and CRing = 2.74E−03 and 2.36E−03 in children and adults, respectively, in the Upper Aquifer; HQing = 17 and 14.1 and CRing = 1.04E−02 and 9.81E−03 in children and adults, respectively, in the Puelche Aquifer. As regards the soil exposure pathways, NCR and CR of Cr(VI) are unacceptable, dermal contact being the main route (HQderm = 4.63; CRderm = 9.34E−04).
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Vol.:(0123456789)
1 3
Exposure and Health
https://doi.org/10.1007/s12403-021-00386-9
ORIGINAL PAPER
Assessment ofHuman Health Risk ofChromium andNitrate Pollution
inGroundwater andSoil oftheMatanza‑Riachuelo River Basin,
Argentina
ElinaCeballos1,2· SabrinaDubny1,2· NataliaOthax1,2· MaríaE.Zabala1,2· FabioPeluso1,3
Received: 1 September 2020 / Revised: 3 February 2021 / Accepted: 11 February 2021
© The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature 2021
Abstract
This study assesses hexavalent chromium [Cr(VI)] and nitrate (NO3
) in polluted groundwater and soil, and evaluates the
impact on the health of the inhabitants of the Matanza-Riachuelo River basin, Argentina. Sixty groundwater samples and 18
soil samples were collected. Statistical analysis and Stiff diagrams were used for the hydrochemical characterization of the
groundwater. A method developed by the United States Environmental Protection Agency for health risk assessment was
applied to the Upper and the Puelche aquifers. The non-carcinogenic (NCR) and carcinogenic risks (CR) posed by Cr(VI) and
NO3
in groundwater via ingestion and dermal contact were determined in children and adults. The effect of Cr on children
through ingestion, dermal contact and inhalation as a result of exposure to soil was also established. The results indicated that
the Cr(VI) and NO3
average values were 0.35mg/L and 76mg/L, respectively, in the Upper Aquifer, whereas the Cr(VI)
average values were 1.41mg/L and 38mg/L for NO3
in the Puelche Aquifer. Children and adults exposed to groundwater
via ingestion and dermal contact faced acceptable NCR of NO3
, but unacceptable NCR and CR of Cr(VI). Water ingestion
was the main exposure route; HQing = 4.15 and 4.07 and CRing = 2.74E−03 and 2.36E−03 in children and adults, respectively,
in the Upper Aquifer; HQing = 17 and 14.1 and CRing = 1.04E−02 and 9.81E−03 in children and adults, respectively, in the
Puelche Aquifer. As regards the soil exposure pathways, NCR and CR of Cr(VI) are unacceptable, dermal contact being the
main route (HQderm = 4.63; CRderm = 9.34E−04).
Keywords Human health risks· Groundwater quality· Hexavalent chromium· Nitrate· Matanza-Riachuelo River basin·
Groundwater and Soil pollution
Introduction
Chromium (Cr) is a pollutant that affects both soil and
groundwater and is classed as a priority pollutant by the
United States Environmental Protection Agency (USEPA)
owing to its carcinogenicity and mutagenicity. The sources
of anthropogenic pollution of Cr can be traced to toxic
waste generated by industrial activities such as electro-
plating, tanneries, and chemical industries (Heikoop etal.
2014). In the natural environment, Cr exists in two main
oxidation states, chromium hexavalent [Cr(VI)] and tri-
valent [Cr(III)]. The latter is an essential trace element
given its role in pancreatic hormone insulin and/or glu-
cose metabolism. However, Cr(VI) is toxic in biological
systems owing to its high water solubility and oxidation
potential since it can penetrate cell membranes. Thus,
Cr(VI) is more toxic than Cr(III) because it results in
adverse reactions in the nasal septum and lungs and may
lead to chronic ulcers and dermatitis (Baig etal. 2018).
On the other hand, nitrate (NO3
) is another pollutant
found in groundwater (Puckett etal. 2011). Nitrogen is
generally incorporated into the soil via the use of syn-
thetic and organic fertilizers in agricultural areas. How-
ever, nitrogen from septic sewage leakage in urban areas
that lack sewage treatment plants is another major source
* Elina Ceballos
eceballos@ihlla.org.ar
1 Instituto de Hidrología de Llanuras “Dr. Eduardo J. Usunoff”
(IHLLA), República de Italia 780, Azul, BuenosAires,
Argentina
2 Consejo Nacional de Investigaciones Científicas
y Técnicas (CONICET), Av. Rivadavia 1917,
CiudadAutónomadeBuenosAires, Argentina
3 Comisión de Investigaciones Científicas de la Provincia de
Buenos Aires (CICPBA), LaPlata, BuenosAires, Argentina
E.Ceballos et al.
1 3
of NO3
in groundwater (Sacchi etal. 2013). The organic
and inorganic sources of nitrogen are transformed into
nitrate through microbial mediated redox reactions (Borch
etal. 2010). High NO3
ingestion affects health because
ingested nitrate is reduced to nitrite, which binds to hemo-
globin to form methemoglobin. Elevated levels of meth-
emoglobin interfere with the oxygen-carrying capacity of
the blood causing methemoglobinemia in infants. Moreo-
ver, after ingestion, nitrate may result in the formation of
carcinogenic nitrosamines on reacting with secondary or
tertiary amines (Ward etal. 2005).
The health risk assessment (HRA) method of the USEPA
has been employed in numerous studies on pollutants in
groundwater and soils worldwide. The health risk assess-
ment of heavy metals in groundwater has been studied by
Baig etal. (2016), Naz etal. (2016) and Othax etal. (2019).
Other studies have focused on the health risk of Cr(VI)
through different exposure pathways (Fallahzadeh etal.
2018; Mehmood etal. 2019). Moreover, a large number of
works have highlighted the health risk posed by Cr in soils
via ingestion, dermal contact and inhalation (Chabukdhara
and Nema 2013; Xu etal. 2018; Timofeev etal. 2019; Adi-
malla 2020). As for nitrogen, some studies have underscored
the health risk of NO3
pollution in groundwater (Zhang
etal. 2018; Adimalla 2019). Nevertheless, only He and Wu
(2018) have assessed the health risk posed by Cr(VI) and
NO3
in groundwater through drinking water intake.
The Matanza-Riachuelo River basin (MRB) is the most
populated (exceeding 4 million inhabitants), the most indus-
trialized and the most grossly polluted basin in Argentina.
Numerous petrochemical industries, tanneries, slaughter-
houses and meat packing plants release a toxic mix of heavy
metals, hydrocarbons and raw sewage into the basin.
Groundwater is contaminated by both Cr(VI) and NO3
in
the middle sector of the basin (Ceballos etal. 2018). The
processes that control the natural attenuation of both pol-
lutants have been evaluated by Ceballos etal. (2020). These
authors demonstrated that the natural attenuation of Cr(VI)
greatly exceeds that of NO3
and that the source of NO3
in
groundwater can be traced to septic tank residues.
Despite the fact that the MRB is one of the 10 most pol-
luted basins in the world (Blacksmith Institute and Green
Cross Switzerland 2013), relatively few studies on the health
risk posed by these two contaminants have been published.
Pasqualini etal. (2019) estimated the Environmental Health
Risk (EHR) in the MRB using the methodology described
by Díaz Barriga (1999). These authors stressed the need
to integrate multiple environmental determinants of health,
sources of pollution and different qualitative indicators in
the EHR calculation. Nevertheless, the EHR estimate was
limited by the absence of an evaluation of the intensity of
exposures. Cittadino etal. (2020) evaluated the soil pollution
caused by heavy metals in urbanized settlements of a sector
of the MRB. However, these authors considered only the
exposure route through ingestion when applying the HRA.
The present study seeks to evaluate the quality of the
groundwater and soil and apply the HRA methodology for
an exhaustive analysis of the risk scenario. The specific
objectives are as follows: (i) to evaluate the variation of pol-
lution from Cr(VI) and NO3
in groundwater during a three
year period, (ii) to assess the Cr contaminated soil near a
disused chemical plant, (iii) to estimate the health risks in
children and adults via oral and dermal contact with Cr(VI)
and NO3
contaminated groundwater, and (iv) to assess the
health risk in children through ingestion, dermal contact and
inhalation of Cr contaminated soil. This study provides use-
ful information that serves as a basis for the efficient man-
agement of groundwater and soil in the MRB.
Study Area
The MRB is located in the NE of the province of Buenos
Aires, Argentina (Fig.1a). The basin covers an area of
approximately 2065 km2 and has a population exceeding
four million (INDEC 2010) distributed among 15 admin-
istrative jurisdictions. Unchecked industrial development
accompanied by unrestrained population growth has led to
a proliferation of urban slums (Emerging Urbanizations,
UREMs). The UREMs make up 25% of the total population
of the MRB, where close to a million people have high social
vulnerability indexes and are exposed to serious health prob-
lems. According to Monteverde etal. (2013), approximately
50% of the population suffers from waterborne illnesses of
attributed to the use of groundwater extracted from private
supply wells. The study area is a UREM located in the mid-
dle sector of the basin in the north of the Esteban de Ech-
everría jurisdiction (Fig.1b). It has been classified as an
area of high environmental sanitary risk by Pasqualini etal.
(2019). A large number of households have no access to
sanitation and drinking water. Pulmonary, gastric and der-
matological illnesses are common. Approximately, 42% of
the population is under the age of 15 and 6% is over the age
of 60 (ACUMAR 2016).
The MRB consists of a gently undulating plain. The
main water course is the Matanza River, which flows
70km to the NE before being renamed Riachuelo about
15km before it discharges into the Río de la Plata. The
area has a temperate climate with warm summers and cool
winters. Average rainfall for the period 1906–2014 was
1100mm/year (Scioli and Burgos 2015). The main water
supply for human consumption and industry in the MRB
is facilitated by two aquifer systems (Fig.1c): the Upper
Aquifer, which is of medium to low productivity with
variable water quality, and the Puelche Aquifer, which is
of medium to high productivity and good water quality
Assessment ofHuman Health Risk ofChromium andNitrate Pollution inGroundwater andSoil of
1 3
(Zabala etal. 2016). The Upper Aquifer receives natural
recharge through infiltration of rainwater and is recharged
by anthropogenic activity (Scioli and Burgos 2015). Given
that the Puelche Aquifer does not crop out in the MRB, it
is recharged directly from the Upper Aquifer by vertical
filtration (Vives etal. 2013). The piezometric levels of the
Upper and Puelche aquifers respond simultaneously to sea-
sonal recharge elevations and dry-season drawdowns, indi-
cating a close connection between both aquifers (Zabala
etal. 2016). In both aquifers the regional groundwater
flow is SW to NE (Vives etal. 2013). In the study area,
the Ortega stream is the main water course that drains
the area in a N-NW direction before discharging into the
Matanza River (Fig.1b). In this sector, the Upper Aquifer
is approximately 25m thick and consists of sandy-clayey-
silt loess (Holocene), homogeneous fine-grained loess and
sandy loess (Pleistocene), and of interbedded carbonate
(tosca). By contrast, the Puelche Aquifer has a maximum
thickness of 30m and consists of quartz sands at the bot-
tom and silts and clays that are interbedded towards the
top (Upper Pliocene to Pleistocene). According to Auge
(2004), these silty clay sediments behave as an aquitard
(7m thick) in the study area (Fig.1c).
Methodology
Sampling ofGroundwater andChemical Analysis
Groundwater samples were collected from February 2015
to September 2017 in five field campaigns (February
2015, June 2015, August 2016, February and September
2017). Samples were collected from 3 monitoring wells
(samples P13, P28 and P29) and 19 private supply wells
(samples DW1, P14, P15, P16, P17, P18, P19, P20, P21,
P22, P23, P25, P26, P27, P30, P31, P32, P33, and P34)
(Fig.1b). Samples P28 and P20 were obtained from the
Puelche Aquifer (40m well depth) whereas the remaining
samples were collected from the Upper Aquifer (15–20m
well depth). The water in the wells was purged three
times. Groundwater levels were measured with an electri-
cal probe, and parameters such as electrical conductivity
(EC), temperature, pH and dissolved oxygen were deter-
mined insitu using a Multiparameter PCS Testr 35 Series
tester equipped with a flow cell to avoid contact with the
atmosphere. The samples were collected in polyethylene
bottles after the wells had been continuously pumped until
Fig. 1 Location of a the Matanza-Riachuelo River Basin (MRB) and Esteban de Echeverria jurisdiction and b the study area (Emerging Urbani-
zation San Ignacio). The hydrogeological profile of the middle sector of the MRB is shown in c
E.Ceballos et al.
1 3
stabilization of the EC values. The samples for Cr(VI)
analysis were immediately filtered through a 0.45μm
membrane filter, after which the pH was adjusted to 9 with
NaOH (1N). The samples for NO3
analysis were filtered
through 0.22μm nylon filters. All samples were stored in
an insulated cooler with ice and delivered to the laboratory
on the same day and stored at 4°C for further analysis.
The chemical analyses were performed at the IHLLA
Laboratory following the methodology proposed by the
American Public Health Association (APHA 2005). Con-
centrations of calcium, magnesium, sodium and potassium
were measured by flame atomic absorption spectrometry
(AAS); sulphate by turbidimetry; chloride by argentometry;
nitrate by ultraviolet spectrophotometer screening; carbon-
ate, bicarbonate and alkalinity by titration; and Cr(VI) was
determined colorimetrically within 24h of sample collection
using diphenylcarbazide with an UV–Vis spectrophotometer.
The Statistica 8 software using basic statistical calcula-
tions was employed for a general hydrochemical characteri-
zation. Stiff diagrams were employed to identify chemical
types of groundwater and the possible physicochemical pro-
cesses producing them. Moreover, a temporal analysis of the
pollution was carried out using the monitoring wells.
Sampling ofSoil andChemical Analysis
Soil samples were collected in a sector located along the left
margin of the Ortega stream (Fig.1b), where waste from
a disused chemical factory was buried. The soil sampling
consisted in constructing a trench (1m long × 0.6m wide
and 0.75m deep) in the area. Given the presence of blocks
of varying sizes, further drilling took place in the trench
to a depth of 2.3m. In the first 0.75m of the profile, soil
sampling was carried out in the sectors where variations in
color and granulometry were observed. Samples were col-
lected every 0.1m between a depth of 0.75m and 2.3m.
Moreover, blocks (rubble) of variable dimensions were col-
lected from the first meter of the soil profile. All the samples
were placed in polyethylene bags and hermetically sealed.
The samples were dried separately at room temperature for
1week in a clean environment. They were then disaggre-
gated and sieved to < 2-mm fraction. Eighteen samples were
selected to determine the total Cr concentration by means of
multi-acid digestion (HNO3 + HClO4 + HF) before analysis
by inductively coupled plasma mass spectrometry (ICP-MS,
Perkin-Elmer Elan 6000) at the ACME LAB Bureau Veritas
laboratory, Canada.
Health Risk Assessment
Risk to health was estimated by contact with polluted ground-
water and soil. The HRA model for exposure to groundwater
was based on the effect of Cr(VI) and NO3
on the inhabitants
who mostly depend on groundwater for drinking and bathing
in zones 1 and 2 of the study area (Fig.1b). Zone 1 (approx-
imately 21,045 m2) was characterized by a high content of
Cr(VI) and NO3
(samples P15, P17, P18, P19, P21, P22, P29,
P30, P31, P33, P34, DW1, P20, and P28), whereas zone 2
(approximately 1,000,000 m2) was characterized by a negligi-
ble Cr(VI) content and high NO3
content (samples P11, P13,
P14, P23, P25, P26, P27 and P32). As regards the habitats,
the risk to health from exposure through ingestion and dermal
contact was estimated in 10-year-old children and adults in the
two zones. The health risk through the inhalation route was not
evaluated since it was not considered to be a major route of
exposure in groundwater risk assessment (Kelepertzis 2014).
The concentration term for Cr(VI) and NO3
was based on
probability distributions fitted with the concentrations meas-
ured in each zone as a single concentration using Crystal Ball
(Decisioneering 2007).
To study the effect of Cr contaminated soil on 10-year-old
children, the HRA was applied to zone 3, which is the site
of the former chemical plant used by children for recreation
(13,500 m2; Fig.1b).
The risk was calculated using exposure pathways of inges-
tion, dermal contact and inhalation taking into account the
average concentration of two depths (topsoil (0–0.2m) and
1m). Although children were expected to be exposed to top-
soil, the deepest layers of soil were also regarded as a prob-
able scenario of exposure. Note that the total Cr concentration
measured was assumed to be Cr(VI) or Cr(III) in line with
earlier studies (Timofeev etal. 2019).
The methodology used for the HRA was based on that of
the USEPA (2019). As for exposure to water, the average daily
doses (ADDs) (mg/kg/day) of exposure to NO3
and Cr(VI)
via ingestion (ADDingw) and dermal contact (ADDdermw) were
calculated in accordance with the following equations
As for exposure to soil, the average daily doses of expo-
sure to both Cr(VI) and Cr(III) were calculated via inges-
tion (ADDings), dermal contact (ADDderms) and inhalation
(ADDinhs) in accordance with the following equations
(1)
ADD
ingw =
C
IR
Ing
ED
EF
BW AT
(2)
ADD
dermw =
DAevent
EV
ED
EF
SA
BW AT
(3)
ADD
ings =
C
IR
Ing
ED
EF
BW AT
CF
(4)
ADD
derms =
C
SA
SAF
ABS
ED
EF
BW AT
CF
Assessment ofHuman Health Risk ofChromium andNitrate Pollution inGroundwater andSoil of
1 3
The parameters used from Eqs.(1) to (5) show the prob-
ability model, statistical descriptors, minimum and maxi-
mum values for the probabilistic variables, and the value
for the deterministic ones for children and adults (TableS2
in Online Resource 1). The risk was calculated probabil-
istically by applying Monte Carlo (MC) simulations with
Crystal Ball 7.1 software (Decisioneering 2007).
For the risk calculation, the non-carcinogenic effect
was estimated by the hazard quotient (HQ) for Cr(VI) and
NO3
and for each exposure pathway in accordance with the
following expression
where HQi (dimensionless) represents the non-carcino-
genic risk (NCR) quotient via ingestion (HQing), dermal
contact (HQderm) and inhalation (HQinh) exposure to water
and soil, and RfD is the oral (RfDoral), dermal (RfDderm)
and inhalation (RfDinh) reference dosage in mg/kg/day of
each substance (TableS3 in Online Resource 1). In soil,
the conversions proposed by RAIS (2020) were employed
to determine the RfDinh value from the RfDing values for
Cr(VI) and Cr(III).The NCR was calculated for each route of
exposure and for the aggregate risk, which is the sum of the
risk quotient of all the routes of exposure. HQ > 1 represents
an unacceptable NCR.
The potential carcinogenic risks of Cr(VI) (i) through
ingestion and dermal contact of groundwater and (ii) through
ingestion, dermal contact, and inhalation of soil were calcu-
lated using the following equation
where CRi (dimensionless) denotes the carcinogenic risk
(CR) via oral, dermal contact and inhalation. SFi (mg/kg/
day) is the slope factor for each route of exposure and rep-
resents the probability of developing cancer per unit expo-
sure level. The SFi values are shown in TableS3 in Online
Resource 1. In line with the USEPA (1991), cancer risk
values exceeding 1E−04 are considered to be unacceptable.
Results andDiscussion
Assessment ofGroundwater Pollution
The statistical values calculated from the chemical data
determined in the groundwater samples collected during
the 2015–2017 period are shown in Table1. In the Upper
aquifer, the pH value ranges from 6.9 to 8.1 with an average
(5)
ADD
inhs =
C
IR
inh
ED
EF
Bw AT PEF
(6)
HQ
i=
ADD
i
[
RfD
]
(7)
CRi
=
ADDi
×
SFi
of 7.6, suggesting neutral to alkaline conditions. The electri-
cal conductivity (EC) varies between 992 and 2940 μS/cm
with an average value of 1729 μS/cm. The chemical com-
ponents with the greatest range are HCO3
, SO4
2− and Cl.
Likewise, the Puelche Aquifer shows characteristics similar
to those of the groundwater in the Upper Aquifer (Table1).
The chemical data for the groundwater samples of the Upper
Aquifer (TableS1 in Online Resource 1), collected in the
August 2016 campaign are used to characterize the different
chemical types of groundwater since the samples were col-
lected from a larger area. Figure2 shows the spatial distribu-
tion of the chemical types of groundwater. The groundwater
is mainly of the Na-HCO3 type, which coincides with that
determined regionally for the MRB in the Upper and Puelche
aquifers (Zabala etal. 2016). However, the Na–HCO3Cl,
Na–HCO3SO4 and Na–SO4 types also occur in the study
area, mainly in the groundwater samples taken near the dis-
used chemical factory (zone 3 in Fig.1b). This suggests that
the high contents of SO4
2− and Cl result from waste leached
by infiltrated rainwater.
In 58 samples taken from the Upper Aquifer, the
Cr(VI) concentrations range from below the detection
limit (< 0.001mg/L) to 5.6mg/L with an average value of
0.35mg/L (Table1). Thirty-five per cent of the samples
breach the safety limit for human consumption specified by
the World Health Organization (WHO 2012; 0.05mg/L).
In contrast, the content of Cr(VI) in the Puelche Aquifer
is higher (0.40 and 3.80mg/L) with an average value of
1.41mg/L, which exceeds the limit established by the WHO.
Cr(VI) pollution is prevalent downstream from the waste
disposal site of the disused chemical plant (i.e., zone 1 in
Fig.1b). The areal extension of the pollution is approxi-
mately 200m in the direction of the underground flow
(N-NW, Fig.1b) and has remained relatively constant dur-
ing the study period. The samples taken from the monitor-
ing wells P28 and P29 are used to evaluate the variation
in Cr(VI) concentration during this time (Fig.3). In gen-
eral, the Upper Aquifer (P29) shows greater variations in
Cr(VI) content than the Puelche Aquifer (deep aquifer, P28).
Likewise, the concentration of Cr(VI) is higher in the deep
aquifer (approximately 1mg/L). These variations in Cr(VI)
concentrations could be ascribed to dilution processes owing
to the hydraulic gradient observed between P29 and P28 (see
piezometric level at both wells in TableS1 Online Resource
1). This indicates a downward flow of groundwater, suggest-
ing a migration of Cr(VI) pollution from the Upper Aquifer
towards the deep aquifer. Moreover, Ceballos etal. (2020)
suggested that the spatial variations in the Cr(VI) concen-
trations are attributed to reduction processes. In the present
study, the Cr(VI) concentrations detected during the 3-year
period are higher than those obtained by Berna etal. (2010)
in aquifers contaminated with Cr(VI) with concentrations of
up to 2.6mg/L detected in a five-year period. Nevertheless,
E.Ceballos et al.
1 3
these authors do agree that the variations in Cr(VI) con-
centrations over time are attributed to reduction and dilu-
tion processes. On the other hand, Heikoop etal. (2014),
who studied aquifer systems contaminated with Cr(VI) by a
power plant over a four-year period, reported lower Cr(VI)
concentration in deep aquifers than in shallow aquifers in
contrast to our findings. These authors also reported that
reduction and mixing played an important role in the Cr(VI)
variation observed.
The NO3
pollution is higher in the Upper Aquifer than in
the Puelche Aquifer. The NO3
concentration varies between
14 and 243mg/L with an average value of 76mg/L in the
Upper Aquifer (Table1). Sixty-three per cent of 51 samples
exceed the safety limit for human consumption specified by
the WHO (2012;45mg/L). The concentration of NO3
in
the Puelche Aquifer varies between 8 and 60mg/L with
an average value of 38mg/L. Three in 6 samples exceed
the limit established by the WHO. In contrast to Cr(VI)
contamination, NO3
is detected in the whole study area
(Fig.1b). The samples taken from the monitoring wells P28,
P29 and P13 were used to evaluate the temporal variation of
NO3
(Fig.3). In the sector contaminated with Cr(VI), the
variation in NO3
concentration over time is greater in the
Upper Aquifer (between 49 and 185mg/L, P29) than in the
Puelche Aquifer (P28), where NO3
does not show major
variations (between 21 and 60mg/L). On the other hand, at
P13 located some distance from Cr(VI) pollution (Fig.1b),
the NO3
concentrations vary over time between 67 and
243mg/L in the Upper Aquifer (Fig.3). In this area, there
are no data on the concentration of NO3
in the deep aqui-
fer given the absence of wells that capture water from the
Puelche Aquifer. The high NO3
concentration at P29 and
P13 may be ascribed to the proximity of the Upper Aquifer to
the septic systems. Furthermore, the NO3
concentration in
the groundwater samples taken from the private supply wells
varies in space and time (zone 1 and zone 2 in Fig.1b). Vari-
ations in the content of the pollutant in groundwater could
be due to dispersal processes and to the differences in depth
of the private supply wells (ranging in depth between 10 and
20m). The average NO3
value obtained in the present study
exceeded that obtained in groundwater contaminated by the
excessive use of chemical fertilizers in agriculture in Song-
nen Plain, China (Zahi etal. 2019). Moreover, these authors
also pointed out that the spatial variation of NO3
content
in groundwater could be due to diffusion and transloca-
tion of NO3
in three dimensions after being leached into
Table 1 Statistical analysis
results of physicochemical
parameters for the Upper and
Puelche aquifers samples
Ion concentration is in mg/L
N number of samples, St. Dev. standard deviation, P Percentile
N Mean Median SD Min Max P10 P25 P75 P90
Upper Aquifer
pH 52 7.6 7.5 0.3 6.9 8.1 7.2 7.4 7.8 8.0
EC (µS/cm) 52 1729 1721 383 992 2940 1277 1448 1930 2271
 Ca2+ 54 67.4 62.1 29 19 140 37 43 86 108
 Mg+54 42 40 14 12 71 24 30 51 64
 Na+54 266 262 61 108 456 194 239 297 359
 K+54 17.5 17.0 4 10 27 13 15 21 23
 HCO3
44 666 669 104 407 850 506 598 747 797
 Cl54 127 104 84 33 462 54 79 155 244
 SO4
2− 54 150 106 138 30 729 44 84 167 282
 NO3
51 76 63 53 14 243 26 33 108 146
Cr(IV) 51 0.35 0.03 1.0 0.001 6.0 0.001 0.001 0.2 0.8
Puelche Aquifer
pH 6 7.6 7.7 0.2 7.3 7.8 7.3 7.5 7.7 7.8
EC (µS/cm) 6 1382 1277 218 1245 1803 1245 1252 1526 1803
 Ca2+ 6 33 35 9 21 45 21 24 40 45
 Mg+6 22 22 4 15 26 15 19 25 26
 Na+6 229 239 46 142 276 142 209 255 276
 K+6 12 13 2 9 13 9 11 13 13
 HCO3
5 566 553 55 518 649 518 519 621 649
 Cl6 106 98 43 56 186 56 83 125 186
 SO4
2− 6 101 84 46 71 192 71 72 125 192
 NO3
6 38 20 45 8 60 8 18 53 60
Cr(IV) 6 1.41 1.21 1.03 0.40 3.80 0.40 0.73 1.96 3.80
Assessment ofHuman Health Risk ofChromium andNitrate Pollution inGroundwater andSoil of
1 3
groundwater. Similarly, Adimalla (2019) detected a lower
average NO3
value in contaminated groundwater in South
India. This author reported higher NO3
concentrations in
agricultural areas than in domestic areas.
Assessment ofSoil Pollution
Total Cr concentration of the soil samples ranges between 32
and 3997mg/kg at the waste disposal site near the disused
chemical factory (zone 3 in Fig.1b). As for the distribution
of total Cr in depth, Fig.4a shows that the highest total Cr
concentration occurs in the first meter of the profile. Fur-
thermore, the soil pH varies in depth (Fig.4b), indicating
acid conditions in the first meter (soil pH = 3.6 to 3.9) and
neutral conditions at 2m depth (soil pH = 7). Hence, the
two soil zones defined in the soil profile are as follows: an
upper zone (0–1m deep) characterized by Cr concentrations
that range between 185 and 3997mg/kg and acidic pH and
a lower zone (varying in depth between 1 and 2m) with Cr
concentrations close to levels of the natural chemical back-
ground (approximately 30mg/kg, Limbozzi 2011; Blanco
etal. 2012) and neutral pH. In the upper zone, the blocks
also reveal high total Cr contents, between 482 and 3607mg/
kg. Therefore, the Cr content in the first meter of the profile
is between 6 and 130 times greater than that established for
the Cr background. This suggests an anthropogenic source
of Cr mainly from solid waste at the disused chemical fac-
tory. The Cr content was lower than that in acid soils due
to leakage from plating tanks (Baron etal. 1996). However,
Wanner etal. (2012) reported Cr concentrations (similar to
those detected in the soil of the present study area) in the
polluted soils of a former chromite ore processing plant.
Fig. 2 Stiff diagram of the groundwater samples taken in the August 2016 campaign
E.Ceballos et al.
1 3
The study area is not heavily polluted and undergoing
rapid industrial development but it is also home to numerous
socially vulnerable inhabitants, the great majority of whom
are under the age of fifteen. The present study stresses the
need to adopt and implement remediation measures to tackle
the pollution and the dangerous levels of Cr in the soil.
Health Risk Assessment
Carcinogenic andNon‑carcinogenic Risk Assessment
ofGroundwater
The non-carcinogenic risk (NCR) of NO3
and Cr(VI)
Fig. 3 Temporal variation of
Cr(VI) and NO3
concentrations
during the 2015–2017 period
Fig. 4 Depth soil profiles showing the variation of total Cr concentrations in soil (a) and pH (b) at the polluted site
Assessment ofHuman Health Risk ofChromium andNitrate Pollution inGroundwater andSoil of
1 3
using P95 in children and adults for zones 1 and 2 is shown
in Fig.5.
The NCR of NO3
is lower than the acceptable levels
established by USEPA (< 1) for both age groups exposed
to water extracted from the Upper and the Puelche aquifers
(Fig.5a and b). This indicates a negligible NCR through
ingestion or dermal exposure in the two zones. In zone
1, the HQing and HQderm values are 6 and 800 times for
children and 5 and 1100 times for adults smaller than 1 in
the Upper Aquifer. The HQing and HQderm values are 8 and
2000 times for children and 11 and 2500 times for adults
smaller than 1 (Fig.5a) in the Puelche Aquifer. However,
in zone 2 (Fig.5b), the HQing value calculated for the
Upper Aquifer is almost twice as high as that for children
and adults in zone 1 owing to the elevated NO3
concen-
trations (between 25.4 and 243mg/L). In this case, the
HQing value is 3 times smaller than 1. Despite the low
HQing and HQderm values the risk to health is negligible.
These findings tally with those of Wu and Su (2015) and
Zhai etal. (2017), who revealed that children are more
susceptible to disease than the adults.
The NCR of Cr(VI) in zones 1 and 2 is shown in
Fig.5c, d. In zone 1, the aggregate risk exceeds the
acceptable level for the two age groups in both aqui-
fers. In the Upper Aquifer, the aggregate risk in children
and adults exceeds the safety limit by a factor of five
(TableS4 in Online Resource 1) whereas in the Puelche
Aquifer, the aggregate risk is 20 times higher than the
acceptable limit for children and 16 times higher in
the case of adults. These values suggest that the water
extracted from the deep aquifer (Puelche Aquifer) may
lead to an increase in NCR owing to high Cr(VI) concen-
trations (between 0.4 and 3.8mg/L). The main route of
NCR is water ingestion (Fig.5). In the Upper Aquifer, the
HQing value is 2.5 times higher than the HQderm value for
children whereas for adults it is 3.5 times higher. How-
ever, in the Puelche Aquifer, exposure via ingestion is
5.4 and 5.8 times higher than dermal contact in children
Fig. 5 Graphic representations of the non-carcinogenic Hazard Quo-
tients (HQ) of NO3
and Cr(VI) through ingestion and dermal contact
of groundwater (Upper and Puelche aquifers): a Non-Carcinogenic
Risk (NCR) of NO3
in zone 1; b NCR of NO3
in zone 2; c NCR of
Cr(VI) in zone 1 and d NCR of Cr(VI) in zone 2
E.Ceballos et al.
1 3
and adults, respectively. The NCR results of Cr(VI) in the
present study exceed those obtained by Fallahzadeh etal.
(2018) at drinking water wells with Cr(VI) contents of up
to 1.3mg/L. Nevertheless, these authors do agree that the
risk is greater for children than for adolescents and adults.
In zone 2, the aggregate risk values are below the
safety limits for children and adults (Fig.5d). The HQing
value is 0.081 for children and 0.065 for adults whereas
the HQderm value is 0.02 for children and 0.0143 for
adults (TableS5 in Online Resource 1). Hence, there
is an absence of risk posed by water extracted from the
Upper Aquifer for exposure routes owing to the negligible
Cr(VI) concentrations in the zone. As regards the NCR of
Cr(VI) and NO3
in the study area, the risk is attributed
to Cr(VI) because of its toxicity.
The Cr(VI) species is considered a carcinogenic com-
pound by the International Agency for Research on Can-
cer (IARC 2015). Figure6 shows the cancer risk (CR)
posed by Cr(VI) for the two age groups in both zones.
The CR values in zone 1 exceed the acceptable cancer
risk value (< 1.00E−04) specified by USEPA via inges-
tion in children and adults (TableS6 in Online Resource
1). In the Upper Aquifer, the CRing value is 2.74E−03 for
children and 2.36E−03 for adults whereas that of CRderm
is 5.70E−06 for children and 4.49E−06 for adults. How-
ever, the CR value is raised for both exposure routes in
the Puelche Aquifer. CRing is 1.04E−02 for children and
9.81E−03 for adults whereas CRderm is 1.23E−05 for chil-
dren and 9.03E−06 for adults, which suggests that the
water extracted from the deep aquifer has a more harmful
impact on health via ingestion. In contrast, the cancer risk
is negligible in zone 2 because the Cr(VI) content does
not exceed 0.001mg/L in the Upper Aquifer.
Carcinogenic andNon‑carcinogenic Risk Assessment ofSoil
In zone 3, the NCR assessment shows that the HQ values
for Cr(III) are lower than the acceptable levels (HQ < 1) for
all exposure pathways whereas the values for Cr(VI) breach
the acceptable limits for topsoil (0–0.2m) to a depth of one
meter (TableS7 in Online Resource 1). Figure7a shows that
NCR of Cr(VI) exists for both the topsoil and 1m deep soil.
The aggregate risk value of Cr(VI) is three times higher in
the first meter than in the topsoil. The HQing value estimated
for the topsoil indicates the absence of NCR of Cr(VI) via
ingestion. However, the HQing value for the 1m deep soil
increases to 2.84, which exceeds the safety level owing to a
higher Cr concentration in soil (between 180 and 3997mg/
kg; Fig.4). This considerably increases the risk to health.
The HQderm value is 1.45 for the topsoil and 4.63 for the
upper soil zone, suggesting that the soil poses a risk to chil-
dren via dermal contact. By contrast, the HQinh value is 3
orders of magnitude lower than the HQ values for dermal
and ingestion exposure, indicating that inhalation pathways
do not pose a risk to health. These results show that dermal
contact is the main exposure pathway for NCR in children.
Furthermore, the three exposure pathways of Cr occurred in
descending order as follows: der mal > ingestion > > inhala-
tion. However, other authors such as Adimalla (2020) found
that the main route for NCR exposure in children was inges-
tion whereas dermal contact and inhalation pathways posed
no risk to health except for Cr concentration between 81 to
751mg/kg (mean of 244.1mg/kg) in urban soil. Similarly,
in their study of an industrial area and a recreational area,
Timofeev etal. (2019) reported Cr concentrations that were
lower than those in zone 3 of the present study. According
to these authors, ingestion was the main route for NCR in
contrast to dermal absorption in children. On the other hand,
Fig. 6 Graphic representations of the carcinogenic risk of Cr(VI) in groundwater (Upper and Puelche aquifers) in zone 1 (a) and zone 2 (b)
Assessment ofHuman Health Risk ofChromium andNitrate Pollution inGroundwater andSoil of
1 3
risk via ingestion was reported for the industrial area despite
the absence of children. However, in the present study, zone
3 is used as a play area by children with the result that the
site is now a potential health threat, the main exposure route
being dermal contact.
Figure7b shows the cancer risk (CR) of Cr(VI) via dif-
ferent exposure pathways and the aggregate risk (CRaggr) for
both the topsoil and the first meter of soil.
A CRaggr value was estimated to be 3.4 times greater for
the first meter than for the topsoil owing to the increase in
the Cr concentration with soil depth as shown in Fig.4a.
Similarly, CR values for ingestion and dermal contact are
higher than the acceptable cancer risk value (< 1.00E−04)
established by USEPA. The CRing values estimated for the
topsoil and for the first meter are 1.91E−04 and 6.09E−04,
respectively (TableS8 in Online Resource 1). Moreover,
the CRderm value is 3.11E−04 for the topsoil whereas it is
9.34E−04 for the first meter. However, the risk of soil inha-
lation (CRinh) is lower than the acceptable level, suggesting
the absence of a cancer risk via inhalation in the recrea-
tional area. Dermal contact and ingestion of contaminated
soil therefore pose the greatest carcinogenic risk to chil-
dren (Fig.7b). Although zone 3 is an industrial area (out
of bounds to children) the area is nevertheless frequented
by children. Timofeev etal. (2019) reported carcinogenic
risk of direct contact with skin and through ingestion in
urban and industrial sites used as play areas by children. Xu
etal. (2018) found carcinogenic aggregate risk for children
exposed to Cr in urban and industrial areas. The CR values
decreased for ingestion, dermal contact and inhalation. How-
ever, De Miguel etal. (2007) and Chabukdhara and Nema
(2013) pointed out that the carcinogenic risk for children
posed by Cr was within an acceptable range in urban soils
used for recreation near industrial sites. It should be noted
that only inhalation was considered in the aforementioned
studies. Similar CRinh values were obtained in the present
work.
To better understand the harmful impact of soil contami-
nation on the health of children in zone 3, further studies
including the implementation of soil management of Cr
is warranted. Moreover, given the HQaggr and CRaggr val-
ues obtained from groundwater ingestion in zones 1 and
3 (industrial area used for recreation), children are at an
increased risk of exposure to Cr(VI). These results indicate
that the elevated concentrations of Cr in water and soil zones
1 and 3 of Esteban de Echeverría pose serious health risks
to children.
Despite the uncertainties that accompany the risk values
calculated from polluted soil and groundwater, the health
risk assessment has proved helpful in distinguishing the
toxic pollutants and exposure routes described in the study
area. The findings focus attention on the pressing need
to adopt and implement remediation measures that must
include epidemiological studies of the local population.
Conclusions
Over the three year study period, the average Cr(VI) con-
centration was 0.35 and 1.41mg/L in the Upper and Puelche
aquifers, respectively. In the study area, Cr(VI) pollution was
detected downstream from the industrial waste disposal site
(about 200m), and its areal extension has remained more
or less constant over the period of observation. NO3
pol-
lution in the Upper Aquifer was higher (average concen-
tration = 76mg/L) than in the Puelche Aquifer (average
concentration 38mg/L). Unlike Cr(VI) pollution, NO3
pol-
lution is prevalent in the study area.
Fig. 7 Graphic representations of the health risk assessment of Cr(VI) for children in soil in zone 3: a non-carcinogenic risk (NCR) and b carci-
nogenic risk (CR)
E.Ceballos et al.
1 3
The soil of the disused factory contains Cr concentrations
that range from 185 to 3997mg/kg in the first meter of the
profile, which exceeds the Cr background concentration by
as much as 6–130 times. This indicates that Cr in ground-
water has an anthropogenic source.
The NCR of NO3
in children and adults exposed to water
extracted from both the Upper and the Puelche aquifers is
acceptable. By contrast, the NCR posed by Cr(VI) down-
stream from the waste disposal site is unacceptable to both
age groups. Water ingestion is the main exposure route. The
HQing value is 4.15 for children and 4.07 for adults in the
Upper Aquifer. However, exposure via ingestion increased
HQing to 17 and 14.1 in children and adults, respectively, in
the Puelche Aquifer.
Importantly, the cancer risk posed by Cr(VI) mainly via
groundwater ingestion is unacceptable to both age groups.
The CR via ingestion of water extracted from the Upper
Aquifer is 2.74E−03 and 2.36E−03 for children and adults,
respectively. Likewise, CR via ingestion of water extracted
from the deep aquifer (Puelche Aquifer) reached 1.04E−02
and 9.81E−03 for children and adults, respectively. Water
extracted from the Puelche Aquifer led to an increase in non-
carcinogenic and carcinogenic risks due to the higher Cr(VI)
contamination.
The NCR posed by Cr(III) for children exposed to soil
is within acceptable levels whereas that posed by Cr(VI)
mainly via dermal contact exceeds safety limits. In topsoil,
the NCR posed by Cr(VI) through ingestion is 8.91E−01
whereas it is 1.45 via dermal contact. However, in the
first meter of depth, the HQing and HQderm values reached
2.84 and 4.63, respectively. The carcinogenic risk in chil-
dren is due to dermal contact and ingestion of contami-
nated soil. CRing is 1.94E−04 and CRderm is 3.11E−04 in
topsoil. In the first meter of depth, CRing = 6.09E−04 and
CRderm = 9.34E−04. However, the inhalation pathways pre-
sent no health risk.
From the above, it follows that children are at an increased
risk owing to the elevated concentration of Cr in water and
soil. It has therefore been recommended that the inhabitants
in Emerging Urbanizations abstain from using groundwater
extracted from private supply wells. This is of particular
relevance to those inhabitants living in the vicinity of the
disused chemical factory. Our study underscores the urgent
need for remediation measures to tackle exposure to CR in
groundwater and soil in the MRB.
Supplementary Information The online version of this article contains
supplementary material available at (https ://doi.org/10.1007/s1240
3-021-00386 -9).
Acknowledgements This research was funded by projects PIP 2013-
2015 (Consejo Nacional de Investigaciones Científicas y Técnicas,
CONICET, Argentina) and PICT 2013-2422 (Ministerio de Ciencia,
Tecnología e Innovación, MINCYT, Argentina). Thanks are due to the
IHLLA technical staff, Ms. M.F. Altolaguirre and Ms. O. Floriani for
their assistance in water sampling. Authors gratefully acknowledge
Dr. Jordi Cama i Robert for his generous help. Language assistance by
native English speaker George Von Knorring is also acknowledged.
Compliance with Ethical Standards
Conflict of interest The authors declared that there is no conflict of
interest.
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... In the past, various studies were conducted for the pollution exposure assessment of metals and ecological and human health risk assessment of different contaminated sites viz risk assessment of chromium contamination in the Ranipet region, Tamilnadu, India (Manoj et al., 2021), computation of health risks due to presence of Cd and Cr in the water supply chain of Langat River Basin, Malaysia (Ahmed and Mokhtar, 2020), assessment of geological and anthropogenic impacts on the heavy metal pollution in the western Birbhum district, West Bengal, India (Mukherjee et al., 2020), analysis of spatial distributions of heavy metals in the surface soil of 30 km 2 (agricultural and industrial region) area of South eastern China and its associated ecological risk indexes (Wu et al., 2021), health risk assessment due to presence of chromium and nitrate in the groundwater and soil of Matanza-Riachuelo River basin, Argentina (Ceballos et al., 2021), risk assessment due to contaminated groundwater in the vicinity of Estarreja Chemical Complex (ECC), in northwest Portugal (Cabral Pinto et al., 2020). Most of these studies covered the ecological and human health risk assessment of J o u r n a l P r e -p r o o f various heavy metals, i.e., arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), etc. ...
... The HQ value for teens playing in the mud scenario was 2 -4 times higher than the safe limit, while HQ values were within the safe limit (Fig. 6). Similar findings of high HQ values (HQ = 4.63) were reported in the study by Ceballos et al., (2021), investigating the risk due to Cr-contaminated soil near to chemical factory in Esteban de Echeverria, Argentina. The order of posing a risk as per average HQ value was found as Rania (pre-monsoon) > Khanchandpur (monsoon) > Rania (monsoon) > Khanchandpur (pre-monsoon). ...
... Similar results for CR (CR = 9.34 x 10 -4 for skin dermal contact via soil pathway) were reported for soil near to chemical factory in Esteban de Echeverria, Argentina (Ceballos et al., 2021). Overall, on the basis of CR values for both the sites in pre-monsoon and monsoon, the order of posing cancer risk was observed to be in order of teen playing in mud (CR > 10 -4 ) > adultstaged activitywet soil (CR ~ 6 x 10 -6 ) > adultutility workerscommercial activity (CR ~ 2x10 -5 ) > adultfarmer (CR ~ 1.7 x 10 -5 ) > adultgardener (CR ~ 1.2 x 10 -5 ) > adultconstruction worker (CR ~ 1 x 10 -5 ) > adultirrigation installer (CR ~ 8 x 10 -6 ) > ...
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... This is because the wastewater is often channeled directly into the pit without treatment [21,22]. The wastewater can also serve as a collection point for contaminants, which eventually percolate into the ground water aquifer [23]. A polluted aquifer can have its water recycled back to humans that drink from the bore hole sunk at the abattoir. ...
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... Nowadays, environmental samples are usually polluted with a variety of compounds and it is uncommon to find an aquatic or other environmental system which is impacted by a single toxicant (Jarque et al., 2016). In Argentina, years ago, there was an indiscriminate release of pollutants, including PAHs, such as Phe (Rotondo et al., 2021); heavy metals just like Cr(VI) (Ceballos et al., 2021); organochlorine pesticides for instance γ-HCH (Aparicio et al., 2018b); azo dyes, e.g. RB5 (Martorell et al., 2018), among others. ...
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This study was carried out to investigate the current status of groundwater quality in Wuqi County, northwest China. The health risk assessment was also performed to quantify the negative impacts of hexavalent chromium (Cr⁶⁺) and nitrate (NO3⁻) in groundwater on human health by fully considering the gender and age of local residents. For this study, thirty groundwater samples were collected from wells and boreholes distributed in the study area and analyzed for pH, total dissolved solids (TDS), total hardness (TH), major ions (Na⁺ + K⁺, Ca²⁺, Mg²⁺, HCO3⁻, SO4²⁻, and Cl⁻), NO3⁻, nitrite (NO2⁻), and Cr⁶⁺. Statistical analysis and graphical approaches were adopted to delineate the physicochemical parameters and hydrochemistry of groundwater. Fuzzy comprehensive method was applied in this study to appraise overall groundwater quality. The model recommended by the Ministry of Environmental Protection of the People's Republic of China was selected to assess the non-carcinogenic and carcinogenic risks caused by Cr⁶⁺ and NO3⁻ through drinking water intake. Indicated by statistical mean values, the order of cations is Na⁺ + K⁺ > Ca²⁺ > Mg²⁺, and that of anions is SO4²⁻ > Cl⁻ > HCO3⁻. The averages of TH, TDS, NO3⁻, and NO2⁻ are 432, 1253, 23.2, and 0.099 mg/L, respectively. Piper diagram indicates that groundwater in the study area is SO4·Cl–Na type, SO4·Cl–Ca·Mg type, and HCO3–Na type. Gibbs diagrams suggest that the major ion chemistry of groundwater in the area is governed by rock weathering and water–rock interaction, while evaporation plays a minor role. According to the results of groundwater quality assessment, over one-third (36.67%) of the groundwater samples are of poor or very poor quality. Through oral pathway, female and male adults in the study area face acceptable non-carcinogenic risks, while children face unacceptable non-carcinogenic risks caused by Cr⁶⁺ and NO3⁻. Both children and adults face unacceptable carcinogenic risks from Cr⁶⁺. In addition, children face higher carcinogenic risks than females and males owing to smaller body weight than adults. This study may provide local authorities with insights into making scientific decisions for sustainable groundwater exploitation and efficient groundwater environmental protection.
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Nitrogen pollution of groundwater is becoming more and more serious due to intense and extensive industrial and agricultural activities. This may exert great influence on human health. In this paper, human health risk due to groundwater nitrogen pollution in Jinghui canal irrigation area in Shaanxi Province of China where agricultural activities are intense was assessed. Forty-seven groundwater samples were collected from shallow wells and analyzed for physicochemical indices in the study area. Water samples were analyzed for pH, total dissolved solids (TDS), total hardness (TH), major ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO³⁻, CO3²⁻, Cl⁻ and SO4²⁻), nitrate (NO3–N), nitrite (NO2–N) and ammonia nitrogen (NH4–N). General groundwater chemistry was described by statistical analysis and the Piper diagram. Water quality was quantified via comprehensive water quality index (CWQI), and human health risk was assessed considering the age and exposure pathways of the consumers. The results show that the shallow groundwater is slightly alkaline and groundwater types are HCO3·SO4·Cl–Mg and HCO3·SO4·Cl–Na. Rock weathering and evaporation are main natural processes regulating the groundwater chemistry. The CWQI indicates that groundwater in the study area is seriously polluted by TH, TDS, SO4²⁻, Cl⁻ and NO3⁻. Human health risk is high because of high concentrations of nitrate in drinking water. The results also show that children are at higher risk than adults. The health risk through dermal contact is much lower than that through drinking water intake and can be ignored.
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The groundwater contamination by hexavalent chromium (Cr(VI)) in a site of the Matanza-Riachuelo river basin (MRB), Argentina, has been evaluated by determining the processes that control the natural mobility and attenuation of Cr(VI) in the presence of high nitrate contents. The groundwater Cr(VI) concentrations ranged between 1.9E-5 mM and 0.04 mM, while the nitrate concentrations ranged between 0.5 mM and 3.9 mM. In order to evaluate the natural attenuation of Cr(VI) and nitrate in the MRB groundwater, Cr and N isotopes were measured in these contaminants. In addition, laboratory batch experiments were performed to determine the isotope fractionation (ε) during the reduction of Cr(VI) under denitrifying conditions. While the Cr(VI) reduction rate is not affected by the presence of nitrate, the nitrate attenuation is slower in the presence of Cr(VI). Nevertheless, no significant differences on ε values were observed when testing the absence or presence of each contaminant. The εCr determined in the batch experiments describe a two- stage trend, in which Stage I is characterized by εCr ~−1.8‰ and Stage II by εCr ~−0.9‰. For nitrate, the respective εN obtained is −23.9‰ whereas εO amount to −25.7‰. Using these ε values and a Rayleigh fractionation model we estimate that an average of 60% of the original Cr(VI) is removed from the groundwater of the contaminated site. Moreover, the average degree of nitrate attenuation by denitrification is found to be about 20%. This study provides valuable information about the dynamics of a complex system that can serve as a basis for efficient management of contaminated groundwater in the most populated and industrialized basin of Argentina. Postprint version available at: http://hdl.handle.net/2445/161641
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Toxic element's accumulation in the urban environment not only worsens the quality of air, water, soils, and foodstuffs but also threatens the health of people because of entering human bodies through lungs, stomach, and contact with skin. The aim of this study is to assess the current geochemical and ecological state of the soil cover in the city of Darkhan (Mongolia) and to estimate health risks on this basis. Soil geochemical survey was performed in 2012–2013, the result was a collection of 126 soil samples. The bulk contents of 13 potentially toxic elements (PTEs) were determined by ICP-MS and ICP-AES. The soils of the industrial zone are most heavily polluted and contain increased concentrations of Pb, Mo, Sb, Zn, W, Cr, As, Cd, and Cu (geo-accumulation index Igeo = −1.87–4.13), which form four multi-elemental anomalies. First contrasting anomaly extends from thermal power plant in the north–northeastern direction where contamination degree (CD) reaches 39.5–45. Second and third anomalies are located near leather goods plant (CD = 44.2) and metallurgical plant (CD = 33) respectively. The last one is founded in the northern part of the city near granary and railway station (CD = 39.4–42.2). Soils of unused areas and part-recreation zone are not polluted, Igeo < 0 for all PTEs. The most significant impact on human health is exerted by Co, V, Cr, Pb, W, As, and Sb in all land-use zones. These elements contribute more than 97% to the value of health index (HI). Health risk is low for adults (HI ≤ 0.14) and medium for children (HI = 1.16). The HI values for children are above 1 for more than 60% of the city. Oral admission is the main type of element's input (As, Cd, Cr, and Pb) in the human body, it's share in the total risk (TR) of cancer development is 86–97%. The TR values are within 1.09 × 10⁻⁵-5.68 × 10⁻⁵, which corresponds to the medium risk level. Maximum values are in the industrial zone of Darkhan. The contribution of Cr and As is most pronounced among the studied elements.