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Chemosphere 99 (2014) 56–63
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Chemosphere
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Development and mapping of seleniferous soils in northwestern India
0045-6535/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.chemosphere.2013.09.072
⇑ Corresponding author. Address: 288-F, Shaheed Bhagat Singh Nagar, PakhowalRoad, Ludhiana 141013, Punjab, India. Tel.: +91 161 4361919 (R); +91 98724 19199(M).
E-mail addresses: [email protected] (K.S. Dhillon), [email protected] (S.K. Dhillon).
Karaj S. Dhillon, Surjit K. Dhillon ⇑Department of Soil Science, Punjab Agricultural University, Ludhiana 141 004, Punjab, India
h i g h l i g h t s
� Periodic surveys to identify and characterize Se sources and contaminated soils.� Se in soil, plant varied from 0.02-4.9, 0.6-515 mg/kg; present in profile 2 m depth.� Developed map showing different categories of seleniferous soils in northwest India.� Shiwalik rocks and underground water are the main sources of Se contamination.� Se-rich sediments deposited by rain water lead to development of seleniferous soils.
a r t i c l e i n f o
Article history:Received 7 May 2013Received in revised form 30 August 2013Accepted 19 September 2013Available online 7 November 2013
Keywords:Seleniferous soilsDistribution mapRocksSedimentsSeasonal rivuletsShiwaliks
a b s t r a c t
Periodic surveys were undertaken to identify and characterize Se-contaminated soils in northwesternIndia. Total Se content varied from 0.023 to 4.91 mg kg�1 in 0–15 cm surface soil and 0.64–515.0 mg kg�1
in samples of vegetation. Selenium-contaminated land occupying an area of 865 ha was classified intodifferent categories based on total Se content of soils as moderately contaminated (0.5–2.0 mg Se kg�1)and highly contaminated (>2.0 mg Se kg�1). The normal soils contained <0.5 mg Se kg�1. The soil mapwas prepared using village level cadastral maps. Se-contaminated soils were silty loam to silty clay loamin texture and tested pH 7.9–8.8, electrical conductivity 0.3–0.7 dS m�1, calcium carbonate 0.1–4.1% andorganic carbon 0.4–1.0%. Selenium was present throughout the soil profile up to 2 m depth; 0–15 cm sur-face soil layer contained 1.5 to 6.0 times more Se than in subsurface layers.
Selenium content in rock samples collected from lower and upper Shiwalik sub-Himalayan ranges var-ied from 1864 to 2754 and 11 to 847 lg kg�1, respectively. The sediments transported through seasonalrivulets linking the Shiwalik ranges to affected sites contained 0.57–2.89 mg Se kg�1. The undergroundwater containing 2.5–69.5 lg Se L�1 used for irrigating transplanted rice grown in Se-contaminated arearesulted in a net Se addition in soil up to 881 g ha�1 y�1; possibly further aggravating the Se-toxicityproblem. Presence of substantial amount of Se in rock samples and sediments of seasonal rivulets sug-gests that Se-rich materials are being transported from Shiwalik hills and deposited in regions where sea-sonal rivulets end up.
� 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Selenium (Se) acts as an essential micronutrient in case of lowdaily intake for both human beings and animals; but high levelsof dietary intake or ingestion can result in Se toxicity for humans,birds, and aquatic biota (Lemly, 1997). Inclusion of Se in the list ofinorganic carcinogenic agents (Shubik et al., 1970) has promptedthe researchers all over the world to ascertain its level in all con-stituents of environment. Total Se concentration in most soils ofthe world ranges from 0.01 to 2 mg Se kg�1 (Swaine, 1955), but
concentration up to 1200 mg Se kg�1 have also been reported fromseleniferous areas of Ireland (Fleming and Walsh, 1957). Parentmaterial has been considered as an important factor controllingthe level of Se in geoecosystems. Most of the seleniferous soils ly-ing in arid and semi-arid areas of the western states of USA havedeveloped in situ from weathering of underlying rocks derivedmainly from Cretaceous sedimentary deposits of the Niobraraand Pierre shale formations. Selenium contents in different rocktypes constituting these formations ranged from 1 to 300 mg kg�1
(Rosenfeld and Beath, 1964). Besides the native substrate, amountof rainfall also plays an important role in determining Se content insoil (Fleming, 1980). Several anthropogenic activities are also asso-ciated with elevated Se concentrations in soils. Seleniferous soilshave developed due to inadvertent disposal of Se-rich products likestone-coal in China (Zhu et al., 2008); dumping Se-rich slimes from
K.S. Dhillon, S.K. Dhillon / Chemosphere 99 (2014) 56–63 57
copper refinery in Mexico (Rosenfeld and Beath, 1964) and storageof drainage water at Kesterson Reservoir in California (Frankenber-ger and Benson, 1994). As a consequence of various anthropogenicactivities, worldwide emission of Se into soils ranges from 6000 to76,000 t yr�1 (Nriagu and Pacyna, 1988).
The study area is located between 31.0417 and 31.2175�N and76.1363 and 76.4147�E in the Nawanshahar, Garshankar and Sar-oya blocks in the state of Punjab in northwestern India. It receivesabout 900 mm annual rainfall and has been classified as a hot butless dry zone adjoining the hills. Soils of this region have formedfrom the alluvium transported by rainwater run-off through sea-sonal rivulets from nearby hills of the Shiwalik range and depos-ited in low-lying areas (Krishnan, 1968). Parent material of thesoils is derived from upper Shiwalik rocks that are mainly com-posed of polymictic conglomerates of variable composition. Theserocks, in turn, are derived from metamorphic terrain of the Hima-layas (Karunakaran and Rao, 1979). The main crops grown in thisregion are wheat (Triticum aestivum) followed by maize (Zea mays),rice (Oryza sativa), sugarcane (Saccharum officinarum) and mustard(Brassica compestris). The typical symptoms of Se toxicity i.e. snow-white chlorosis were observed on wheat plants growing in thefields during a routine survey of this region (Dhillon and Takkar,1985). Selenium content of different plant species (mg kg�1 drymatter) growing in the affected fields was found to be very highand it ranged from 3 to 58 in cereal straws, 5 to 66 in cereal grains,1 to 51 in vegetables (edible portion), 4 to 41 in green forages and39 to 365 in weed plants (Dhillon and Dhillon, 1997, 2009).Consumption of Se-rich diet results in serious health hazards toanimals and humans in the affected region (Dhillon and Dhillon,1997).
The sporadic nature of distribution of Se-contaminated soilsmakes the risk assessment due to Se toxicity difficult. Thereforethe current study was designed to identify and demarcate thecontaminated soils into different categories. It should be helpfulin assessing the suitability of different remediation strategies to aparticular category of soil for reducing the risk of Se toxicity to ani-mals and humans living in the high Se areas. A soil map showinghighly and moderately contaminated sites was developed basedon the Se content of surface soil samples analyzed during periodicsurveys of the affected region in northwestern India and inter-preted the data to understand the distribution of Se in soil profilesin relation to different soil characteristics. An attempt has alsobeen made to identify the sources of Se in the region underconsideration.
2. Materials and methods
2.1. Mapping seleniferous soils
An extensive survey was undertaken to identify the highly con-taminated sites on the basis of typical Se toxicity symptoms ofsnow-white chlorosis visible on young wheat plants (30–40 dayold) growing in the fields. It was observed that highly contami-nated pockets are sporadically distributed in the affected area.During an intensive survey of the contaminated sites, soil and plantsamples were collected from each pocket. Data pertaining to Secontent of soil and plant samples thus generated along with someof the previously published data (Dhillon et al., 1992; Dhillon andDhillon, 1997) were used for developing maps showing the distri-bution of seleniferous soils. Keeping in view the small size ofSe-contaminated land, the Cadastral map – a village land mapshowing individual field boundaries and dimensions, was consid-ered as the best choice for conducting land survey. A copy of theCadastral maps was procured from the concerned officials fordifferent villages affected by Se toxicity problem. Thereafter, the
maps of adjoining villages were joined together at the villageboundaries to produce a unified soil map. Depending up on the le-vel of Se in soil, the affected area was demarcated into differentcategories of seleniferous soils. In addition to this, presence ofsnow-white chlorosis on wheat plants was also used in identifyingthe seleniferous fields. When Se toxicity symptoms appeared uni-formly distributed on more than 50% of wheat plants growing ina field (Fig. 1), it was included in the ‘highly toxic soil’ categoryand the fields showing less than half were included in ‘moderatelytoxic soil’ category.
2.2. Selenium distribution in soil profile
Depth wise samples were collected from different layers of thesoil profiles dug at the highly contaminated sites demarcated in themap. The specific location of soil profiles was recorded as: Nazar-pur (31.15112�N, 76.17024�E), Simbly (31.14615�N, 76.18238�E),Jainpur (31.13539�N, 76.18536�E), Barwa I (31.12191�N,76.20175�E) and Barwa II (31.12931�N, 76.21197�E). Soil sampleswere air-dried under shade, ground in a wooden pestle and mortarto pass through 10 mesh (2 mm) sieve and stored for Se analysis ata dry place. Before undertaking Se analysis, a portion of soil samplewas further ground to pass through 100 mesh sieve. Physical andchemical characteristics of soil samples collected from differentlayers were also determined.
2.3. Collection of sediments and rock samples
In the affected region, Se-contaminated soils are located at thedead ends of seasonal rivulets starting from the nearby Shiwalikrange. While traversing along the visible portions of the rivulets,samples of soil (0–15 cm depth) along with plants were collectedfrom the cultivated land lying along their banks. It is quite possiblethat with passage of time period the bed surface of rivulets gotoverlaid with some foreign material from the adjoining areas. Toavoid the impact of such materials, the upper 30 cm layer of thebed was discarded and the sediment samples were collected froma depth of 30–60 cm. Rock samples were collected from the hills ofShiwalik range located near the starting point of rivulets near Poje-wal and Basu Khad areas. In another survey, rock samples werealso collected from relatively higher range of Shiwalik hills alongChandigarh–Basathu–Solan road as well as along Hoshiarpur toGagret, Nurpur Bedi and Una roads.
2.4. Chemical analysis
2.4.1. SeleniumFor analysis of total Se, air-dried soil and rock samples were
ground to pass through 100 mesh sieve. After air drying for 24 h,plant samples were oven dried at 50 ± 5 �C to a constant weightand ground to a fine powder in a Willey grinding mill. A knownportion of the samples were digested in a mixture of perchloricand nitric acids in conical flasks covered with water coolers(Sokkaro and Ohn, 1977). The acid digest was subjected to Se anal-ysis by following the colourimetric method as described by Cum-mins et al. (1964). A known volume of the digest was acidifiedwith concentrated HCl and treated with ascorbic acid to precipitateout Se. The precipitates were separated using sintered funnel offinest porosity (G-5), dissolved in hydrobromic acid–bromine mix-ture and treated with phenol to decolourize the solution. Afteradjusting the pH to 2.8, freshly prepared solution of 3, 30 diam-inobenzidine tetrachloride (Sigma) was added and allowed tostand in dark for 1 h. Thereafter the pH was raised to 7.8, trans-ferred to Teflon stoppered separatory funnel containing knownamount of toluene and the contents were mixed by shaking vigor-ously for one minute. The colour intensity of monopiazselenol
Fig. 1. Typical selenium toxicity symptoms of snow-white chlorosis along with pink colour exhibited by wheat plants growing in the fields included in highly toxic category(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.).
58 K.S. Dhillon, S.K. Dhillon / Chemosphere 99 (2014) 56–63
complex in the toluene phase versus a reagent blank was measuredat 420 lm using Bosch and Lomb spectrophotometer. The calibra-tion curve was prepared using solutions of known Se concentra-tions by following the procedure as described above.
For determining hot water soluble Se (HWS-Se) in the soil pro-file samples, 10 g soil was refluxed with 50 mL of glass-distilledwater for 30 min on a water bath, filtered through Watman 42and the filtrate was analyzed for Se as described above. It consti-tutes mainly selenate-Se and Se complexes with low molecularweight organic matter.
2.4.2. Soil characteristicsSoil samples were analyzed for pH and electrical conductivity in
soil: water ratio of 1:2; organic carbon (Walkley and Black, 1934),calcium carbonate (Puri, 1930) and particle size (Day, 1965). Avail-able S and P in the soil were estimated by extracting 1 g soil with20 mL of 0.5 M NaHCO3 solution. Sulphur in the extract wasanalyzed by following the turbidimetric method as described byChesnin and Yien (1950).Turbidity due to precipitation of sulphateas barium sulphate was measured on a spectrophotometer(Spectronic 20; Bausch and Lomb) at a wave length of 420 nm.Phosphorus in the extract was analyzed by the ascorbic acid bluecolour method of Watanabe and Olsen, 1965). The colour is stablefor 24 h and was measured on the spectrophotometer at a wave-length of 760 nm.
3. Results and discussion
3.1. Distribution and mapping of seleniferous soils
The seleniferous area subjected to detailed investigations islocated between 31.0417 to 31.2175�N and 76.1363 to76.3147�E. Total Se concentration of surface soils (0–15 cm depth)and plants in the affected region varied from 0.023 to 4.91 mg kg�1
soil and 0.64 to 515.0 mg kg�1 dry matter, respectively (Table 1).The soils producing vegetation containing Se more than the maxi-mum permissible level (MPL) of 5 mg kg�1 dry matter for animalconsumption can be referred as Seleniferous, Se-contaminated orSe-toxic soils. Interpretation of data (Table 1) in terms of probabil-ity of occurrence of a particular concentration of Se in soil–plantsystem revealed that soil samples containing >0.5 mg Se kg�1 are,
in fact, associated with plant samples containing >5 mg Se kg�1
and hence were designated as seleniferous soils. This critical levelshould, however, be used cautiously in differentiating seleniferousfrom nonseleniferous soils. The plant species differ greatly in theircapacity to absorb Se from soil (Dhillon and Dhillon, 2009). Ingeneral, plants belonging to the Cruciferae family absorbed thelargest amounts of Se, followed by those of the Leguminoseae andGramineae families. In the present investigation, 88% of the plantsamples belonged to 30–40 day-old wheat (T. aestivum) shootsand the rest belonged to fresh fully developed leaves of sugarcane(Sachharum officinarum). Only about 8% of the plant samples fromthe soils containing <0.5 mg Se kg�1 contained more Se than theMPL in plants for animal consumption.
Depending up on the level of total Se in soil, the contaminatedarea was divided into three different categories. The soils contain-ing <0.5 mg Se kg�1 were designated as ‘Normal’; from >0.5 to2.0 mg Se kg�1 as ‘moderately toxic’ and that with >2.0 mg Se kg�1
as ‘highly toxic’. The limits for moderately toxic and highly toxiclevels of Se in soil were fixed arbitrarily. The fields showingsnow-white chlorosis on more than 50% of wheat plants (Fig. 1)were also included in the ‘highly toxic’ category. All the valuesfor soil-Se were plotted on the unified Cadastral map and differentcategories were demarcated (Fig. 2). The seleniferous soils com-prising 865 ha are sporadically distributed in a number of villageslocated in Hoshiarpur (300 ha) and Nawanshahar (565 ha) districtsof the state of Punjab (Table 1). No significant differences wereobserved among the physical and chemical characteristics of soilsin the seleniferous region. The soils are alkaline in reaction (pH7.9–8.8) with normal electrical conductivity (0.3–0.7 dS m�1),calcium carbonate (0.1–4.1%), organic carbon (0.4–1.0%), cationexchange capacity (2.6–36.7 cmol kg�1), silty loam to silty clayloam in texture and moderately well drained. There are no majordifference in the productivity potential of seleniferous and normalsoils except that the farm produce obtained from contaminatedsoils is always rich in Se and is thus not fit for animal and humanconsumption.
Selenium contents in contaminated soil and plants (Table 1) areseveral times higher than the minimum safe levels permissible innormal soils and plants. This is also true for the Se content in cerealgrains (5–66 mg kg�1), vegetables (1–51 mg kg�1) and forages(4–41 mg kg�1) produced in the contaminated region (Dhillon
Table 1Variation in Se content of plant and soil samples from contaminated land demarcated into different categories.
Soil category Se concentration (mg kg�1) Seleniferous area (ha)
Plantsa Soil
No. of samples Range Mean ± SD No. of samples Range Mean ± SD
Normal soil (<0.5 mg Se kg�1 soil) 66 0.64–16.7 3.31 ± 3.59 65 0.023–0.47 0.31 ± 0.11 –b
Moderately toxic soil (>0.5–2.0 mg Se kg�1 soil) 51 2.8–351.0 61.32 ± 76.13 60 0.53–1.95 1.22 ± 0.45 602Highly toxic soil (>2.0 mg Se kg�1 soil) 25 43.8–515.0 259.1 ± 152.1 49 2.05–4.91 2.75 ± 0.78 263
a 88% of the plant samples belonged to 30–40 day-old wheat (Triticum aestivum) shoots and the rest belonged to fresh fully developed leaves of sugarcane (Sachharumofficinarum).
b Only 865 ha were affected by selenium toxicity problem in this region. The remaining area was found to be normal.
Fig. 2. Map showing the distribution of highly and moderately Se-toxic soils in the Punjab state of northwestern India.
K.S. Dhillon, S.K. Dhillon / Chemosphere 99 (2014) 56–63 59
and Dhillon, 1997). The greatest risk of Se exposure to domesticanimals and humans living in the affected region appears to beby the possible consumption of forages and grains containing Seabove the maximum permissible level of 4–5 mg kg�1 (Underwoodand Suttle, 1999). In fact, typical symptoms of Se poisoning resem-bling chronic selenosis (Rosenfeld and Beath, 1964) have beenobserved in both animals and humans due to inadvertent con-sumption of Se-rich farm produce (Dhillon and Dhillon, 1997).The farmers are experiencing substantial losses in cattle wealthdue to Se poisoning. Thus it is quite obvious that the animals andhumans consuming farm produce from the fields belonging tothe highly toxic category will always be at higher risk as comparedto others with adjoining fields.
In addition to Se content, redox potential and pH of the soilsdetermine the extent of toxicological or environmental risks dueto Se. In the well aerated alkaline seleniferous soils of this region,selenate-Se is the dominant species (Dhillon and Dhillon, 2004)which is the most mobile and readily available for plant uptake.In semiarid western USA, Se toxicity problems are usually associ-ated with alkaline soils where Se is present in the selenate form(Jump and Sabey, 1989). When alkaline soils are subjected to re-duced conditions, the available fraction of Se is drastically reduceddue to conversion of selenate to selenite species (Dhillon andDhillon, 2004). Due to strong adsorption on clays and hydrous
oxides of Fe, selenite-Se becomes fairly insoluble and thus, largelyunavailable to plants (Mikkelsen et al., 1989).
There is also risk of spreading Se contamination to the normalsoils situated on the periphery of the seleniferous region throughmoving water as a consequence of heavy rainfall and irrigationevents. Studies under simulated rainfall conditions revealed thatsignificant amounts of Se could be lost from seleniferous to theadjoining soils through run-off and drainage processes The losseshowever were controlled by soil properties like total and watersoluble Se content, calcium carbonate and texture of the soils(Dhillon et al., 2008). Highly significant and positive relationshipof total Se have been recorded with hot water soluble (available)Se (r = 0.83��), CaCO3 content (r = 0.42��), electrical conductivity(r = 0.39��) and silt content (r = 0.31��) of seleniferous soils (Dhillonet al., 1992). Although Se levels in soil and plants (Table 1) indicatethe potential risk of Se toxicity problem in animals and humans,but no incidence of selenosis have been reported in the recentyears from northwestern India. This suggests that either the localpopulation may have adapted to the high Se intake or have substi-tuted their diet with foods from outside the high Se areas.
Selenium accumulation in plant parts may also affect the eco-logical interactions of plants. Results of several laboratory and fieldstudies indicate that elevated Se concentrations in Se accumulatorsand hyperaccumulators are toxic to a wide variety of herbivores
Fig. 3a. Distribution of total selenium in soil profiles representing different seleniferous sites.
Fig. 3b. Distribution of hot water soluble selenium (HWS-Se) in soil profiles representing different seleniferous sites.
Table 2Physical and chemical characteristics of soil profiles representing seleniferous sites in northwestern India.
Soil profile parameters Nazarpur Simbly Jainpur Barwa I Barwa II
Depth (cm) 0–170 0–195 0–155 0–166 0–163Total Se content (lg kg�1)a 402–2485 1044–3247 294–1729 698–1432 507–2322Water-soluble Se (lg kg�1)a 11–71 9–98 8–36 10–31 6–27pH 7.7–8.6 8.2–8.7 8.1–8.8 8.3–8.8 7.8–8.6Electrical conductivity (dS m�1) 0.15–0.28 0.14–0.25 0.23–0.32 0.16–0.23 0.23–0.34Organic carbon (%) 0.41–0.65 0.34–0.63 0.39–0.58 0.33–0.53 0.32–0.53Calcium carbonate (%) 0.50–0.87 0.50–9.92 0.32–4.75 0.30–2.65 0.35–4.87Available P (mg kg�1) 35.8–102.0 39.0–84.3 19.6–45.7 30.4–40.3 20.6–94.8Available S (mg kg�1) 5.1–20.3 11.8–18.9 13.2–34.3 14.6–23.3 9.1–16.0Silt (%) 44.2–65.8 45.7–53.9 41.2–51.7 48.6–52.0 44.0–49.1Clay (%) 11.2–36.0 23.6–41.0 22.9–81.2 26.2–30.4 35.1–42.8
a The highest values belong to surface layer in all the soil profiles.
60 K.S. Dhillon, S.K. Dhillon / Chemosphere 99 (2014) 56–63
and pathogens ranging from prairie dogs to a variety of arthropodsand fungi (Fusarium and Alternaria) (Barillas et al., 2011). Hladunet al. (2012) observed significant reduction in productivity, longev-ity and survival rate of honey bees (Apis mellifera L.) foragingBrassicas growing on seleniferous soils. In Brassica juncea Seaccumulation >0.05–0.1% leads to decrease in biomass, pollen
germination, individual seed and total seed weight, number ofseeds produced, and seed germination (Prins et al., 2011).
Soils with as high as 10 mg Se kg�1 exist in the state of Haryana,India (Singh and Kumar, 1976); but no relationship has beenreported between high Se levels and health of animal and humans.Only at one location near Karnal at village Chamar Khera,
Tabl
e3
Sele
nium
cont
ent
ofse
ason
alri
vule
tabe
dse
dim
ents
,soi
l,pl
ant
and
sedi
men
tary
rock
sam
ples
colle
cted
from
diff
eren
tlo
cati
ons
inth
ese
leni
fero
usre
gion
.
Sam
ples
from
the
seas
onal
rivu
let
bed
Sam
ples
from
cult
ivat
edla
nd
nea
rth
ese
ason
alri
vule
t
Sedi
men
tPl
ants
Soil
bPl
ants
Loca
tion
Seco
nc
(mg
kg�
1)
Plan
tsp
p.Se
con
c(m
gkg�
1)
Loca
tion
Seco
nc
(mg
kg�
1)
Plan
tsp
p.Se
con
c(m
gkg�
1)
Sim
bly
choe
0.73
Aru
ndo
dona
x0.
59Si
mbl
y4.
38Br
assi
cato
ps44
.1Ja
inpu
rch
oe0.
95A
rund
odo
nax
0.76
Jain
pur
2.75
Trit
icum
aest
ivum
shoo
ts23
.5D
ham
aidr
ain
0.78
Aru
ndo
dona
x0.
57B
arw
a4.
21Tr
itic
umae
stiv
umsh
oots
53.9
Gar
hi
choe
1.62
Aru
ndo
dona
x0.
76M
ehin
dpu
r3.
63Tr
itic
umae
stiv
umsh
oots
30.9
Mal
ewal
choe
0.57
––
Ru
rki
Kh
urd
0.86
Trif
oliu
mal
exan
drin
uman
dBr
assi
cato
psm
ixtu
re2.
74M
ujh
otch
oe2.
81–
–A
chal
pur
1.83
––
Jhan
dupu
rch
oe2.
89–
–Jh
ugi
an1.
94–
–
Sedi
men
tary
rock
sam
ples
coll
ecte
dfr
omn
earb
yh
ills
ofSh
iwal
ikra
nge
Loca
tion
No.
ofsa
mpl
esTy
peof
rock
sSe
con
ten
t( l
gSe
kg�
1)
Ran
geM
ean
±SD
Clu
ster
ofro
cks
oflo
wer
Shiw
alik
sn
ear
Poje
wal
alon
gth
ero
adfr
omG
rah
shan
ker
toN
urp
ur
Bed
ian
dat
Bas
uK
had
5C
lays
ton
e,Sa
ltan
dpe
pper
san
dsto
ne,
yell
owis
hbr
own
san
dsto
ne,
ligh
tgr
eysa
nds
ton
e18
64–2
754
2341
±33
6
Upp
erSh
iwal
ikh
ills
alon
gth
ero
adfr
omH
osh
iarp
ur
toG
agre
t,N
urp
ur
Bed
ian
dU
na
25Sa
nds
ton
e,sh
ale,
clay
-sto
ne,
con
glom
erat
es,s
ilts
ton
e,li
mes
ton
e11
–847
242
±19
0U
pper
Shiw
alik
sal
ong
the
Ch
andi
garh
–Bas
ath
u–S
olan
road
9Sa
nds
ton
es,c
lays
ton
e,si
ltst
ones
,woo
dco
al46
–644
247
±21
1
aTh
ese
ason
alri
vule
tslo
call
ykn
own
asch
oeem
anat
ing
from
nea
rby
hil
lsof
Shiw
alik
ran
gedu
rin
gra
iny
seas
onh
elpe
din
tran
spor
tin
gfl
ood-
wat
erlo
aded
wit
hSe
-ric
hse
dim
ents
and
depo
siti
ng
inth
epl
ain
area
atth
eir
dead
ends
.b
Firs
tfo
ur
loca
tion
sre
pres
ent
hig
hly
toxi
cso
ils
loca
ted
atth
ese
ason
alri
vule
ten
din
gsan
dth
ere
stre
pres
ent
the
soil
slo
cate
dn
ear
the
seas
onal
rivu
let
ban
ks.
K.S. Dhillon, S.K. Dhillon / Chemosphere 99 (2014) 56–63 61
symptoms resembling Se toxicity were observed on some buffaloes(Bubalus bubalis) feeding on fodders containing 0.9–6.7 mg Se kg�1
(Arora et al., 1975). In the sub-Himalayan region of West Bengal, Secontent of soil from the contaminated pastures ranged from 1.45 to2.25 mg kg�1 (Ghosh et al., 1993). Selenium-rich soils have beenidentified in many parts of the world. In the contaminated regionof Western United States, Se content of surface soils ranged from1.5 to 20 mg kg�1 (Anderson et al., 1961). In China, soils containingtotal Se > 3.0 mg kg�1 and water-soluble Se > 0.02 mg kg�1 areassociated with Se poisoning and are located in Sangliao, Weiheand Hua Bei plains (Tan et al., 1994). Acute poisoning and chronicselenosis has been reported from the regions where Se content insoil ranged from 0.3 to 0.7 mg kg�1 in Canada, 0.3 to 20 mg kg�1
in Mexico, 1 to 14 mg kg�1 in Columbia, 1.2 to 324.0 mg kg�1 inIreland and up to 6.0 mg kg�1 in Israel (Rosenfeld and Beath, 1964).
3.2. Selenium in soil profiles
At the contaminated sites (Fig. 2), Se was present in the soil pro-file up to 2 m depth, but its distribution in different layers of thesoil profile did not follow any specific pattern (Figs. 3a and 3b).At all of the contaminated sites, surface soil layer was found tobe rich in Se as it contained 1.5 to 6.0 times more Se in comparisonto the lower layers. Among the surface soil layers at different sites,total Se content was the greatest at Simbly followed by that at Naz-arpur, Barwa II, Jainpur and Barwa I sites. However the trend in hotwater soluble Se was slightly different and was: Simbly > Nazar-pur > Jainpur > Barwa I > Barwa II. Wheat plants exhibited toxicitysymptoms of Se at all the contaminated sites except Barwa I. Lowertotal and water soluble Se content at Barwa I may be responsiblefor differential response. In twenty soil profiles examined in theseleniferous area of eastern Colorado, no apparent uniformity inSe distribution was observed with origin of soils, location anddepths of soil profiles (Rosenfeld and Beath, 1964). As in case ofsurface soils (Dhillon et al., 1992), total Se content in the soil profilealso exhibited significant coefficients of correlation with hot watersoluble (available) Se (r = 0.80), organic carbon (r = 0.72), availableP (r = 0.57) and available S (r = �0.24) content of the soil. The mainfactors influencing the biological availability of soil Se, in order oftheir importance are CaCO3, silt particles, organic matter and clayparticles (Zhao et al., 2005). The ranges in physical and chemicalcharacteristics of different soil layers are reported in Table 2.Among the various soil characteristics, the values of pH, organiccarbon and available P was always the highest in surface layer,whereas the CaCO3 content was the highest in last layer of the soilprofile except in Barwa II and Jainpur. A few Fe–Mn concretions ofblack colour were visible in the 2nd and 3rd layers of different soilprofiles except at Barwa I and Barwa II sites. On the basis of phys-ico-chemical characteristics of surface and profile samples, it maybe concluded that the seleniferous soils identified in northwesternIndia belong to Order – Inceptisol, Great group – Haplustept andSubgroup – Fluventic.
3.3. Sources of Se contamination
3.3.1. Deposition of Se-containing sedimentsLocation of Se contaminated sites at the dead ends of seasonal
rivulets provided a valid reason to believe that Se-rich sedimentscould have been transported through these rivulets along withflood-waters. During rainy season, these rivulets emanate fromthe nearby hills of Shiwalik range and become extinct in the planearea. Although majority of these are not visible now, some portionswere relocated with the help of toposheets as well as discussionwith local revenue officials and farmers, The data presented inTable 3 indicate that all the sediment samples contained highlevels of Se and it was 1.2 to 5.8 times more than the minimum
Table 4Net Se balance in the soil under different cropping sequences irrigated with underground water in the seleniferous region in northwestern India.
Parameters Maize–wheat sequence Rice–wheat sequence
Amount of underground water required for irrigation up to maturity (cm ha�1) 60 200Range in Se concentration of underground water at the seleniferous sites (lg Se L�1) 2.5–69.5 2.5–69.5Total Se addition through irrigation water (g ha�1 y�1) 19–525 56–1417Total Se removal through harvested biomass (g ha�1 y�1) 138–520 203–536Net Se balance in soil (g ha�1 y�1) �119–+5 �147–+881
62 K.S. Dhillon, S.K. Dhillon / Chemosphere 99 (2014) 56–63
permissible level (0.5 mg Se kg�1) for the normal soils (Table 1).Presence of Se in sediments suggests that Se-rich sediments werebeing transported through these channels. Moreover, the soils lo-cated at the dead ends of channels contained significantly moreamount of Se (1.7–7.7 times) than recorded in the bed sediments.Deposition of Se containing sediments repeatedly at the same sitemay have resulted in building up Se level in soil. Selenium contentof surface soils is several times more than lower layers of soil pro-file (Fig 3a). The area remained uncultivated for a long time andthus Se absorbed by natural vegetation from lower layers of soilgot deposited in the surface layer following countless cycles ofgrowth and death. This fact may be partly responsible for higherconcentration of Se in the surface soil.
The nature of the parent material of seleniferous soils is not ade-quately known. It could be related to rocks in upper Shiwalik range(Karunakaran and Rao, 1979). Majority of the rock samples collectedfrom upper and lower Shiwaliks in the present investigation com-prised of sandstones and a few shales (Table 3). Both the rocks arehighly permeable and may contain more than 80–90% of the totalSe in water soluble form (Rosenfeld and Beath, 1964). In comparisonto the rock samples from upper Shiwaliks, the average Se content ofsedimentary rocks from the lower Shiwaliks (i.e. near to the startingpoint of rivulets) was about 10 times higher (Table 3). Seleniumbeing highly soluble, the rain-water helped in depleting Se fromrocks and the solubilized Se was transported along with alluvialsediments and deposited at the channel endings. This process oftransportation and deposition of Se-rich sediments continued fora long period before the soils were brought under cultivation. Obvi-ously the sedimentary rocks were even richer in Se initially than atthe present time. The process of decomposition of parent rocks bywater and its subsequent transport by ground or surface water playsan important role in the development of seleniferous soils (Rosen-feld and Beath, 1964). While reviewing the distribution of rare met-als like Se in sedimentary rocks, Krauskopf (1955) has observed thatthe processes responsible for enrichment of Se in geological materi-als are: mechanical enrichment, precipitation, adsorption, substitu-tion and presence of organic material in the deposits. The SakesarLimestone formation of Eocene age rich in shales and fossils (med-ian Se concentration of 7.2 mg kg�1) has been identified as thesource of Se in saline lakes of Soan–Sakesar Valley, Salt Range, Paki-stan (Afzal, 1999). Significant Se losses through drainage and run-off(water + sediment) from seleniferous soils have also been observedin experiments conducted under simulated rainfall (250–260 mm)with intensities ranging from 56 to 120 mm h�1 (Dhillon et al.,2008). The results suggest that due to heavy irrigation or rainfall,Se lost through drainage and run-off from seleniferous soils(materials) on higher slopes may reach sub-surface soil as well asadjoining nonseleniferous areas. Vertical displacement of dissolvedSe due to rainfall infiltration and evaporation has been reported byZawislanski et al. (1992). In Se-contaminated regions of China, theleaching conditions controlled by microtopography features aremainly responsible for the distribution and redistribution of Se inthe soil–plant system (Zhu and Zheng, 2001).
3.3.2. Underground waterSelenium is also being continuously deposited in the soils
through underground water – the only source of water available
for irrigation and drinking purposes in the affected region.Selenium concentration ranged from 0.25 to 69.5 lg L�1 (av.4.7 lg L�1) in underground water drawn from a depth varyingfrom 24 to 36 m (Dhillon and Dhillon, 2003). However, the watersamples collected specifically from the contaminated sites con-tained 2.5 to 69.5 lg Se L�1 (av. 24.6 lg Se L�1). As per water qual-ity guidelines (NAS-NAE, 1973), 90% of water samples contained Sein the safe range, 11% were not fit for drinking purposes and only5% of the samples were unfit for irrigation of crops.
Addition of Se through underground water was computed forthe copping sequences being practiced by the farmers in theaffected region (Table 4). Selenium inputs were assessed by multi-plying total amount of water applied for raising crops to maturityand the concentration of Se in underground water. Removal of Seby different crops was calculated by multiplying the average yieldand concentration of Se in biomass. As a consequence of higherwater requirement of rice, the addition of Se through irrigationwas 2–3 times more in case of rice–wheat as compared tomaize-wheat system (Table 4). By raising rice–wheat system withwater having higher Se concentration, Se addition into the soilthrough irrigation far outweighed the Se removal by harvestedplant biomass. Positive Se balance in the soil observed underrice–wheat system implies that cultivation of rice in the selenifer-ous region is further aggravating the Se toxicity problem. Ifcultivation of rice–wheat sequence is continued for a decade atthe same site using irrigation water containing 69.5 lg Se L�1,net addition of 8810 g Se ha�1 may obviously lead to the develop-ment of a highly contaminated soil. A similar situation at Kestersonreservoir has been described by Ohlendorf and Santolo (1994). Thereservoir spread over 500 ha was constructed in the San JoaquinValley for storage of agricultural drainage water and furtherredistribution for irrigation purposes. Unfortunately, the storageof drainage water resulted in the deposition of 9000 kg Se justwithin a period of five years and it proved highly toxic for aquaticwildlife species. Human activities have played an important rolein the distribution, transport and bioavailability of Se in theseleniferous soils developed in Enshi county of Hubei province inChina (Zhu et al., 2008).
References
Afzal, S., 1999. Determination of selenium speciation of saline lakes from Soan–Sakesar Valley Salt Range, Pakistan. Ph. D. Thesis, Institute of Chemistry,University of Punjab, Lahore, Pakistan.
Anderson, M.S., Lakin, H.W., Beeson, K.C., Smith, F.F., Thacker, E., 1961. Selenium inAgriculture, USDA Handbook 200. U.S. Government Printing Office, Washington,DC.
Arora, S.P., Kaur, P., Khirwar, S.S., Chopra, R.C., Ludri, R.C., 1975. Selenium levels infodders and its relationship with Degnala disease. Indian J. Dairy Sci. 28, 246–253.
Barillas, J.R.V., Quinn, C.F., Pilon-Smits, E.A.H., 2011. Selenium accumulation inplants – Phytotechnological applications and ecological implications. Int. J.Phytorem. 13 (Suppl 1), 166–178.
Chesnin, L., Yien, C.H., 1950. Turbidimetric determination of available sulphates.Soil Sci. Soc. Amer. Proc. 15, 149–151.
Cummins, L.M., Martin, J.L., Maag, G.W., Maag, D.D., 1964. A rapid method for thedetermination of selenium in biological material. Anal. Chem. 36, 382–384.
Day, P.R., 1965. Particle fractionation and particle size analysis. In: Black, C.A. (Ed.),Methods of Soil Analysis. Part 1. American Society of Agronomy, Madison, WI.
Dhillon, K.S., Dhillon, S.K., 1997. Distribution of seleniferous soils in north–westIndia and associated toxicity problems in the soil–plant–animal–humancontinuum. Land Contam. Reclam. 5, 313–322.
K.S. Dhillon, S.K. Dhillon / Chemosphere 99 (2014) 56–63 63
Dhillon, K.S., Dhillon, S.K., 2003. Quality of underground water and its contributiontowards selenium enrichment of the soil–plant system for a seleniferous regionof northwest India. J. Hydrol. 272, 120–130.
Dhillon, S.K., Dhillon, K.S., 2004. Pools of selenium in some Indian soils at fieldcapacity and submerged moisture regimes. Aust. J. Soil Res. 42, 247–257.
Dhillon, K.S., Dhillon, S.K., 2009. Selenium concentrations of common weeds andagricultural crops grown in the seleniferous soils of northwestern India. Sci.Total Environ. 407, 6150–6156.
Dhillon, K.S., Takkar, P.N., 1985. Disease in wheat crop. Tribune 105 (46), 7.Dhillon, K.S., Bawa, S.S., Dhillon, S.K., 1992. Selenium toxicity in some plants and
soils of Punjab. J. Indian Soc. Soil Sci. 40, 132–136.Dhillon, S.K., Dhillon, K.S., Kohli, A., Khera, K.L., 2008. Evaluation of leaching and
runoff losses of selenium from seleniferous soils through simulated rainfall. J.Plant Nutr. Soil Sci. 171, 187–192.
Fleming, G.A., 1980. Essential micronutrients II: Iodine and selenium. In: Davies, B.E.(Ed.), Applied Soil Trace Elements. John Wiley & Sons, pp. 199–234.
Fleming, G.A., Walsh, T., 1957. Selenium occurrence in certain Irish soils and itstoxic effects on animal. Roy. Irish Acad. Proc. 58, 151–166.
Frankenberger Jr., W.T., Benson, S., 1994. Selenium in the Environment. MarcelDekkar, New York.
Ghosh, A., Sarkar, S., Pramanik, A.K., Chowdhary, S.P., Ghosh, S., 1993. Seleniumtoxicicosis in grazing buffaloes and its relationship with soils and plants of WestBengal. Indian J. Anim. Sci. 63, 557–560.
Hladun, K.R., Smith, B.H., Mustard, J.A., Morton, R.R., Trumble, J.T., 2012. Seleniumtoxicity to honey bee (Apis mellifera L.) pollinators: Effects on behaviors andsurvival. PLoS One. 7 (4), e34137. http://dx.doi.org/10.1371/journal.pone.0034137.
Jump, R.K., Sabey, B.R., 1989. Soil test extractants for predicting selenium in plants,In: Jacobs, L.W. (Ed), Selenium in Agriculture and the Environment. Spl. Publ.No. 23, Soil Science Society of America, Madison, WI, pp. 95–105.
Karunakaran, C., Rao, A.R., 1979. Status of exploration for hydrocarbons in theHimalayan region – Contribution to stratigraphy and structure, In: GeologicalSurvey of India. Misc. Publ. No. 41, Part IV, pp. 1–66.
Krauskopf, K.G., 1955. Sedimentary deposits of rare metals. Econ. Geol. Anniv. 50,411–463.
Krishnan, M.S., 1968. Geology of India and Burma. Higginbotham, Madras.Lemly, A.D., 1997. Environmental implications of excessive selenium: A review.
Biomed. Environ. Sci. 10, 415–435.Mikkelsen, R.I., Page, A.L., Bigham, F.T., 1989. Factors affecting selenium
accumulation by agricultural crops. In: Jacobs, L.W. (Ed), Selenium inAgriculture and the Environment. Spl. Publ. No. 23. Soil Science Society ofAmerica, Madison, WI, pp. 65–94.
National Academy of Sciences – National Academy of Engineering, 1973. Waterquality criteria – 1972: A report of the committee on water quality criteria. USEnvironmental Protection Agency, pp. 232–353.
Nriagu, J.O., Pacyna, J.M., 1988. Quantitative assessment of worldwidecontamination of air, water and soils by trace metals. Nature 333, 134–139.
Ohlendorf, H.M., Santolo, G.M., 1994. Kesterson reservoir – past, present and future:an ecological risk assessment. In: Frankenberger, W.T., Jr., Benson, S. (Eds.),Selenium in the Environment. Marcel Dekker, New York, pp. 69–118.
Prins, C.N., Hantzis, L.J., Quinn, C.F., Pilon-Smits, E.A.H., 2011. Effects of seleniumaccumulation on reproductive functions in Brassica juncea and Stanleya pinnata.J. Exp. Bot. 62, 5633–5640.
Puri, A.N., 1930. A new method of estimating total carbonates in soils. ImperialAgricultural Resaerch, Pusa Bull.. 206.
Rosenfeld, I., Beath, O.A., 1964. Selenium: Geobotany, Biochemistry, Toxicity andNutrition. Academic Press, New York.
Shubik, P., Clayson, D.B., Terracini, B., 1970. The Quantification of EnvironmentalCarcinogens. International Union against Cancer. Technical Report Series: 4.
Singh, M., Kumar, P., 1976. Selenium distribution in soils of bio-climatic zones ofHaryana. J. Indian Soc. Soil Sci. 24, 62–67.
Sokkaro, H.M., Ohn, A., 1977. Determination of selenium in soils. Acta Agril. Scand.27, 285–288.
Swaine, D.F., 1955. The trace element content of soils. Tech. Common W. Bur. SoilSci. 48, 1–157.
Tan, J.A., Wang, W.Y., Wang, D.C., Hou, S.F., 1994. Adsorption, volatilization andspeciation of selenium in different types of soils in China. In: Frankenberger,W.T., Jr., Benson, S. (Eds.), Selenium in the Environment. Marcel Dekker, NewYork, pp. 47–68.
Underwood, E.J., Suttle, N.F., 1999. The Mineral Nutrition of Livestock, Third ed. CABInternational, Wallingford. pp. 421–476.
Walkley, A., Black, I.A., 1934. An examination of the Detjareff method fordetermining soil organic matter and proposed modification of the chromicacid titration method. Soil Sci. 37, 29–38.
Watanabe, F.S., Olsen, S.R., 1965. Test of an ascorbic acid method for determining Pin water and NaHCO3 extract from soil. Soil Sci. Soc. Amer. Proc. 29, 677–678.
Zawislanski, P.T., Tokunaga, T.K., Benson, S.M., Oldfather, J.M., Narasimhan, T.N.,1992. Bare soil evaporation and solute movement of selenium in contaminatedsoils at Kesterson reservoir. J. Environ. Qual. 21, 447–457.
Zhao, C., Ren, J., Xue, C., Lin, E., 2005. Study on the relationship between soilselenium and plant selenium uptake. Plant Soil. 277, 197–206.
Zhu, J., Zheng, B., 2001. Distribution of selenium in a mini-landscape of Yutangba,Enshi, Hubei province. China. Appl. Geochem. 16, 1333–1344.
Zhu, J., Wang, N., Li, S., Li, L., Su, H., Liu, C., 2008. Distribution and transport ofselenium in Yutangba, China: Impact of human activities. Sci Total Environ. 392,252–261.
