REV.CHIM.(Bucharest)♦ 67♦ No. 8 ♦ 2016 http://www.revistadechimie.ro 1441

Distribution of Trace Metals in Surface Water and StreambedSediments in the Vicinity of an Abandoned Gold Mine

from Hunedoara County, Romania

LIDIA KIM1, GABRIELA GEANINA VASILE1*, BOGDAN STANESCU1, CRISTINA DINU1, CORINA ENE2

1National Research and Development Institute for Industrial Ecology ECOIND, 71-73 Drumul Podu Dambovitei Str., 060652,Bucharest, Romania,2 Petroleum-Gas University of Ploiesti, Faculty of Economic Sciences, 39 Bucharest Blvd.,100680, Ploiesti, Romania

The present study investigates the distribution of some toxic metals such as As, Cd, Cu, Cr, Co, Hg, Ni, Pb, Tiwithin sediments and surface water from Baiaga stream, situated near an abandoned mining site fromCerteju de Jos, Hunedoara County, in the vicinity of two mining sterile dumps and Coranda Pit. The entirestudied area indicates an acid pH, both in surface water and sediments. Mobile metallic concentrationswere evaluated using first step of BCR 701 sequential extraction modified scheme. The total and mobilecontent of metals from sediments were determinate using inductively coupled plasma optical emissionspectrometry. Calculated bioavailability index (Ibio) was used in order to correlate the presence of toxicmetal in surface water. The experimental data shows important concentrations of metals (Cd, Co, Cu, Ni,Pb) in surface water correlated with relatively high bioavailability index, that include the surface water infifth quality class (the worst) according to Romanian Order 161/2006. Low content of metals (As, Hg, Ti) insurface water despite the high concentrations presented in sediments represents the effect of lack ofmobility (Ibio less than 0.1%). The bioavailability index represents a useful tool for sediment control in acidicmining sites.

Keywords: sediments, bioavailability index, mining site, metals distribution, surface water

Nowadays there is a growing worldwide concern aboutwater contamination with metallic elements [1,2], giventheir environmental persistence and toxicity effects onliving organisms, beside the fact that water qualityevaluation itself may be a complicated practice.

Metals introduced by human activities into the aquaticenvironment accumulate in sediments and representsindicators of anthropogenic inputs, like mining and smeltingactivities, discharge of untreated or partially treatedeffluents with content of toxic metals. Heavy metalsdischarged into a river system by anthropogenic sources(such as industrial sites) during their transport aredistributed between the aqueous phase and bed sediments[3-6], resulting in high ecological risks. Nevertheless,understanding pollutants sources in aquatic sediments isan important step for pollution control, alongside withecological and toxicity risk assessments of theenvironmental pollution for different receptors, includinghumans [1, 2].

Unlike organic chemicals, the majority of metals cannotbe easily metabolized into less toxic compounds, acharacteristic of them being lack of biodegradability. Onceintroduced into aquatic environment, metals areredistributed throughout the water column, accumulatedin sediments or consumed by biota [7]. Due to desorptionand remobilization processes of metals, the sedimentsconstitute a long – term source of contamination to thefood chain. Metals residues in contaminated habitats havethe ability to bioaccumulate in aquatic ecosystems [2, 8] -aquatic flora and fauna - which, in turn, may enter intohuman food chain and result in health problems [9].

Metals accumulation in sediments occurs throughprocesses of precipitation of certain compounds, bindingfine solid particles, association with organic molecules,co-precipitation with Fe or Mn oxides, or species bounded

* email: gabriela.vasile@incdecoind.ro; Tel.: (+40)720048195

as carbonates - according to the physico-chemicalconditions existing between the sediment and theassociated water column [10, 11].

Usually, functional and out of service metalliferousmines are associated with high levels of heavy metals dueto discharge and dispersion of mine wastes into soils andwater systems; the contamination levels around these sitesdepends on geochemical characteristics and sedimentsmineralization [12]. In recent times, as a particular field,gold mining is considered a significant source of Hgcontamination of the environment owing to activities suchas mineral exploitation, ore transportation, smelting andrefining, disposal of the tailings and waste waters aroundmines [13].

Heavy metals contamination affects some areas inRomania, such as Baia Mare, Rosia Montana, Certej, OasLand where for long historical periods, were conductedmining and processing activities [14-16].

The aim of the study was to investigate the process ofaccumulation and distribution of some toxic metals (As,Cd, Cu, Cr, Co, Hg, Ni, Pb, Ti) in sediments and surfacewater from Certej River in the area situated betweenjunctions with Bocsa Mare and Bocsa Mica Creeks. In thestudied area are situated some processing facilitiesbelonging to abandoned gold mines (underground or openmines) and a waste dump.

Experimental partStudy area

The area under study is located in a region with intensivemining activities, zone situated on the territory of Certejude Jos village, in the drainage area of the Certej River. Themining activities of nonferrous ore developed in the regionfor several hundred years have been generated acidwastewaters with high concentration of heavy metals.

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The area was mapped using a GPS receiver with anaccuracy of ± 5m. The schematic map of the studied areashowing the sampling points is provided in figure 1, alsothe description of sampling points is presented in table 1.

Sample collection and preparationTen sediment and surface water samples in contact

with sediments were collected from ten sampling pointssituated in Certej catchment area (Hunedoara County,Romania) in a sampling campaign performed in April 2014.

Water samples were collected and stored inpolyethylene bottles. From each sampling location, 10 L ofwater were collected. The sediment samples were takenusing a Van Veen Bottom Sampler and collected in glassbottles (SR ISO 5667/6, SR ISO 5667/12) [17, 18]. Allsamples were kept in cooling boxes at 4° C duringtransportation and the analyses were performedimmediately after receiving the samples in the PollutionControl Department, Water, Soil, Wastes Pollution ControlLaboratory from National Research and DevelopmentInstitute for Industrial Ecology, Bucharest, Romania, inaccreditation system according to (SR EN ISO 17025/2005)referential standard [19].

Analytical proceduresA part of sediment samples was dried on laboratory

temperature, homogenized, crushed to fine particles andsieved in a Fritsch Analysette 3 Spartan Vibratory SieveShaker and the fraction less than 63 µm was collected forevaluation of the total content of metals. The other part ofsediment samples, in order to maintain the same structureas in natural conditions, was sieved in wet condition usingsurface water from same sampling point and particle sizeless than 63 µm was collected. A subsample of each drysediment sample (particle size less than 63 µm) wasdissolved with a mixture of strong mineral acids (HCl:HNO3 = 1:3) in a Microwave Laboratory Ethos System, sothat the total concentrations of metals were obtained.

In order to determinate de total content of metals insurface water, 150 mL of samples was digested with 5 mLof ultrapure nitric acid and concentrated to 25 mL(volumetric flask).

In a previous study [20], the optimal extraction methodof metallic mobile fraction from analyzed sediments wasestablished. Figure 2 presents the steps followed for thedetermination of metals in sediments, starting with thesieving step and ending with the detection step usinginductively coupled plasma optical emission spectrometrytechnique.

The sediment dry weight was determined on a separatesubsample and a correction to dry matter (quantity of metalper g dry sediment) was applied to all analytical results(total content).

In case of wet sediments, a dry matter correction wasperformed before the suspensions were prepared, in orderto maintain same ratio between sediment and solution.

Analytical technique used for determination of As, Cd,Cu, Cr, Co, Hg, Ni, Pb, Ti, V, W from surface water andsediment samples (total and mobile fraction) wasinductively coupled plasma optical emission spectrometryperformed using an Perkin Elmer Optima 5300 DV ICP-EOS Spectrometer. All the chemicals were of analyticalreagent grade (Merck quality). Matrix of the solution usedfor calibration curve matched with the extraction solutions.

Table 1DESCRIPTION OFSAMPLING POINTS

FROM CERTEJMINING SITE

Fig. 1. Map of samplingpoints, Certej Area

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Results and discussionsTotal concentrations of metallic elements in surface water

The experimental data obtained for surface watersamples are presented in table 2. Bolded results representconcentrations situated over the maximum admissible for5th class surface water quality [21]. Comparing the resultswith the limits imposed by the Romanian Order no. 161/2006 [21] for surface water quality, the pH values werewithin the acid range, around 3.7 pH unit, outside the setpoints. Within the entire area, the quality of surface waterwas situated in 5th class, represented the worst quality.

Coranda and Ciongani Springs represents receptors forpercolated water from career and sterile mining wastedump. Career water collects mine water and washingwater dumps and represents an important source ofcontamination of the springs. Pollution in surface water isstrongly dependent by the water flow that is in contactwith rocks / sediments and causes leaching of the metals.Depending on the amount of rainfall in the area, surfacewater can be loaded or diluted.

Total concentrations of metallic elements in sedimentThe total content of analyzed metallic elements

dissolved in aqua regia from sediment samples arepresented in table 3.

Fig. 2. Flow scheme for metals determination (total and mobile)in sediment sample

Table 2TOTAL CONTENT OF METALS IN SURFACE WATER SAMPLES (µg/L)

Table 3TOTAL CONTENT OF

METALS IN SEDIMENTSSAMPLES (mg/kg d.m.)

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As presented in table 3, all sediment samples show Asand Cd contents over the maximum admissible limitimposed by in force legislation [20]. By far, the most pollutedsediment sample is the one collected from the point S3,sampling point situated at the exit of Nicodim gallery, inwhich all metals monitored by law (As, Cd, Cr, Cu, Hg, Ni,Pb) reach values above maximum limits.

Based on current legislation, exceeding concentrationswere observed for Cr (S3, S5, S7, S9, S10), Cu (all thesamples without S1, S4 ÷ S6), Hg (S3, S6 ÷ S10), Ni (S1,S3, S5, S7 ÷ S10), Pb (S3, S6 ÷ S10). Regarding non-standardized elements, concentrations above hundreds ofmg/kg d.m. and even thousands in the case of titanium,tens in the case of cobalt and vanadium, and units in thecase of tungsten were observed.

Also, it was noted that most of the analyzed metallicelements accumulate in sediment collected from BaiagaSpring, as a result of repeated washing of polluted areasfrom abandoned gold mines and waste dump, as result ofrain falls.

Mobile fractions of metallic elements in sediments - Indexof Bioavailability (iBA), %

The ability of sediment to transfer metals to surroundingenvironment (e.g. plants) was estimated using theBioavailability index, according to the following formula[22, 23]:

iBAm (%) = (Cm(I) . 100)/Cm(total) (1)where:

Cm(I) is the content of metal from exchangeable form,water soluble and weak acid soluble fraction (carbonates),table 2; Cm(total) is the total concentration of metal insediment sample.

The data reported in table 4 indicate that bioavailabilityindex for Hg and W is zero and so, the impact of these

elements in the environment is extremely low, correlatedwith the metals content in surface water samples (table2).

Bioavailability indexes of Ti are either 0% or fall below0.02% in S3 and S5 samples. In the case of vanadium,bioavailability indexes fall in the value range of 0.2 - 2.5%,its mobility being low. The results correlate both with thetotal amount extracted from the aqua regia, and the valuesrecorded in surface water. The bioavailability index for Crwas situated in the range 0.04% to 1.65%. The Cr mobilitytowards surface water is low, as evidenced by the smallconcentrations of these elements in surface water.

Repartition of metallic elements in aquatic ecosystemcomponents

In figures 3-5 are shown metals distribution maps ininvestigated points by reporting each metal concentrationsto the average metal concentrations in all 10 samplingpoints, expressed as high values, moderate values andvalues below average compared to the averageconcentration. Both for surface water and the sediment,the most polluted area corresponds to the area associatedto Nicodim gallery (S3) and the area of the mine waterdisposal, corresponding to S6 and S7 sampling points.

Bioavailability indexes for Cd and Ni are ranked between2.80 - 13.9% (Cd) and between 1.45%and 36.7% (Ni). Thetransfer of these metals in surface water is high in S1, S2and S10 sampling points for Cd and in S1, S2, S3, S4, and S6for Ni. In other sampling points, high concentrations ofsediment elements correlated with their mobility lead tothe presence of these metals in surface water atconcentrations exceeding 1000µg / L in S3 sampling pointfor Cd and 500 µg / L in S5, S7 S8, S9, S10 stations for Ni(table 2, fig. 3).

Fig. 3. Distribution ofNickel and Cadmium

concentrations in surfacewater and sediments

Table 4BIOAVAILABILITYINDEX (%) FOR 11

METALS INSEDIMENTS

SAMPLES

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Fig. 5. Distribution of Lead andArsenic concentrations in surface

water and sediments

Fig. 4. Distribution of Copper andCobalt concentrations in surface

water and sediments

Metals Co and Cu are found in a bioavailable form ineach investigated samples. In S1-S6 sampling points,bioavailability indexes exceed 14%, indicating a hightransfer of these metals in the sediment surface water.Even if the Co content is not high within the sediment, itshigh percentage of availability allows this element to befound in concentrations between 150 ÷ 550 µg / L in surfacewater. Regarding the Cu content, surface water values (400÷ 3300 µg / L) is due both to total Cu content within thesediment and the fact that it is present in a bioavailableform (fig. 4).

Bioavailability indexes are situated in the range 0 % to0.03% for As and between 0.05% and 6.63 for Pb. Theselow percentages of mobility are reflected in relatively lowconcentrations of these elements in surface water, even ifthe total metal content in the sediment is exceeded insome sampling points. The exception is the S3 samplingpoint, situated at the exit of Nicodim gallery (infiltrationwater, red-orange color), where the correlation betweenthe low water flow, extremely high concentration ofarsenic in the sediment and the bioavailability index of Aslead to concentrations above 1 mg / L (fig.5).

ConclusionsThe study zone represents a heavily polluted area due to

mining activity carried out in the past, therefore the areacontinues to pollute both surface water and sediments

(Coranda, Ciongani and Baiaga Springs). Some generalcharacteristics of the area can be highlighted, such as:acid pH values, high contents of total metals (As, Cd) andmobile metals (Cd, Co, Cu, Ni).

The experimental data showed a significant pollutionwith As, Cd, Co, Cu, Ni in surface water, hence the qualityof surface water was situated in 5th class, represented theworst quality.

Using bioavailability index in the chemicalcharacterization of the studied area allowed the obtainingof important information on the metal potential to migratefrom the sediment structure, entering into the water body.The experimental data have shown a strong connectionbetween the bioavailability percentage of the metal andits content in surface water.

AcknowledgementsThis study has been carried out within the framework of the NUCLEUProgram (Environmental Research - Priority in Sustainable IndustrialDevelopment – MEDIND, PN 09 13-02-19).

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Manuscript received: 15.12.2015