NATURE AN POLUUTION DEGREE OF WATER ASSETS STUDIED BY INDUCTIVELY COUPLED PLASMA-OPTICAL EMISSION SPECTROSCOPY

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1 NATURE AN POLUUTION DEGREE OF WATER ASSETS STUDIED BY INDUCTIVELY COUPLED PLASMA-OPTICAL EMISSION SPECTROSCOPY I.Chindea, C.Mânzat*, S.Cintă-Pânzaru** Axente-Sever Theoretical HighSchool, Mediaş, Romania National Society of Natural Gases, Research Center, Mediaş, Romania Babes-Bolyai University, Optics and Spectroscopy Departament, Romania Abstract Indictuvely coupled plasma optical emission spectroscopy (ICP-OES) has been applied for detection of trace elements in environmental media of Copşa Mică region from Romania. Water samples form different drink source as well as from local rivers have been ollected and measured. Sample collection was made taking into account the possible random environmental contamination with industrial residues. The distribution degree of pollution is presented. Keywords: Inductively coupled plasma atomic emission spectrometry; heavy metals, drink water, trace element determination; integrated atom trap system, preconcentration; solvent extraction. 1. INTRODUCTION

2 The ICP-OES has recently turned into an attractive spectral method of analysis, since the acquisition and detection systems are considerably improved [1-3]. Water analysis with ICP-OES is very proper for injection in ICP [4,5]. Excepting the case of very low concetration when a preconcentration is requested, no further chemical treatments are neccesary. Although the concentration level of analyte could be different in water from sample the sample, they are however, low. In this respect, the detection limits generate large calibration range in the ICP system. The interference problems, which occur at low concentrations of Ca, Al, Mg and Fe can be managed. Moreover, analysis of elements that normally are very expensive or hard, e.g. B, S, Si, P are possible. There is only one limitation of ICP, namely that there is no possible to detect the isotope specie. The aim of this paper is to introduce the advantages of ICP-OES in pollution control of one of the damaged area of our contry, namely, Copşa Mică. II. EXPERIMENTAL Inductively coupled plasma was electrically obtained in an argon stream flowing thourgh a series of concentric quartz tubes, surronded by a coil attached by a radiofrecquency (RF) generator. During the plasma flame the gas stream (Ar) is enriched in electrons from an external source. These electrons are accelerated in the electromagnetic field produced by the RF generator, than support collision processes with the Ar atoms, resulting argon ions and a large number of electrons that will be again accelerated in the electromagnetic field. This process is running on until the gas becomes 32

3 strongly ionized (plasma) after that the electrical discharge becomes stable and selfsupported as long as the RF generator is on. The highest possible extent temperature by plasma is K. The optical system The plasma emission resulting light was focused to the entrance slit of Echelle type. The dispersion system consists both of prism and grating. A CCD detector convert the light energy into electrical energy. The detected power is directly converted through the computer into concetration. The liquid samples are introduced into the plasma as stacking aerosols in Ar stream. The aerosol sample gets into the plasma where the atomization takes place and the atoms and ions are excited. After excitaion sample atoms provide the emission spectrum. Sample holding The recipients were carefully washed in diluted HNO 3 (1/20) prior to use. Stabilization with 1% mineral acid of water sample was the applied, in order to reduce the chemisorption of trace metal ions on the surface and prevents the modifications due to the biologic activity, important for elements like Hg, As which easily enter in the biologic cycle. Sample prelevation was made taking into account the possible random environmental contamination with industrial residues. The preconcentration methods consist of evaporation, extraction with solvents, coprecipation, and ions-exchange. Filtering with a plastic membrane with 0,45 µm holes was than applied. The emission spectra have been collected 33

4 with the Perkin-Elmer, Thermo Jarrell Ash spectrometer with a resolution of 0,5 nm. 3. RESULTS AND DISCUSSIONS In order to avoid contamination in trace analysis (lower than µg/ml) high attention was given to the recipients during collecting samples. Contaminants could be however removed, when the metal extraction was made, analyzing the chelate agents, before extraction, the acids have to be redistributed and the water for analysis has to be distilled and deionized. Table 1 indicated the detection limits easily reached with the ICP system with pneumatic nebulizer. The medium values of the determined elements in river or seawater and the maximal allowed concentrations are also given. The allowed concentrations by the medical and hygenical departments in drink water are presented for comparison. A large range of elements easily determined through direct analysis (Na, K, Mg, Ca, Sr, Ba, Fe, B,S, Si) can be observed, without pre-concentration requirements. The only interferences that could appear in sweat water are due to the background introduced by Ca and Mg. This effect is however weak and can be corrected through the off peak and on peak methods. Anyway, the applied corrections present errors leading to the decrease of the sensitivity in the analysis channels and as consequence, the detection limits of several elements are gently affected. Table 2 shows these effectcs on detection limits produced by a maximum content of Ca and mg in sweat waters and in pre-concentrated (20X) water. 34

5 In order to characterize the fountainhead water quality of the region Copşa Mică, and to establish the impurity degree, there were extracted and analyzed samples from eight fountains at different distanced from the pollution source. From the physical chemistry point of vue it can say that the underground fountainhead is characterized through the high degree of minerals, specific for the fountainhead water in the field area. Analysis or the results from the collected and area classified samples including SC. SOMETRA SA plant leads to the following remaeques (see Table 3): In areas located near pollution source, the fountainhead contains Cd in concentration greater than the drink limits (STAS 1342/91). It has to be point out the presence of the sulfur quantities is greater than CMA[6]. Pb is also present in fountainhead but the quantities are located under the allowed limits, due to the low solvability at neutral values of ph (Pb becomes soluble at ph 6.3). The presence of toxic pollutants is a consequence of the metal and sulfurs soil pollution from the washed residues toward underground. The zones Copşa village, Tîrnăvioara, Micăsasa belong to the maximal polluted area. The pollution degree is decreased with the distance from the pollution source. Due to its nature, the underground has a weak versatility to selfcleaning and this fact leads to a time acquisition of pollution source. Moreover, the hygenic procedures of cleaning do not contribute to the heavy metal reduction or depollution. Obviously, the pollution degree of fountainhead is strictly dependent of the soil pollution degree [6,7]. Beneath of Copşa Mică, in addition to the pollution degree mentioned above, there is a supplementary pollution especially with heavy metals from the Industrial LAND Copşa Mică. In this area, the Pb, Cd and 35

6 Zn rich the greatest values from the entire Tîrnava Mare River. For example, Pb content is between 0,32 (year 1990) and 0,95 (year 1991), the yearly medium value being 0,6 mg/l; Cd has yearly values between 0,002 (year 1996), 0,1 (year 1990) the medium being 0,059 mg/l; Zn content, between 0,49 (1996) and 3,60 (1992), with the medium of 1,87 mg/l. During one year of normal porduction, in the Tîrnava Mare river arrive from the industrial area Copşa Mică 54 t Pb, 639 t Zn and 37 t Cd, and these values embody the river in the second and third quality class, respectively. The nitrites have values between 0,06 (1994) and 0,61 (1996), the nitrates annually maximal values of 8,85 mg/l (1992), ammonia between 0,06 (1992) and 3,22 (1991) with a medium of 1,46 mg/l. In addition, the sulfurs in this section record the greatest media value. Quantitative analysis after calibration clearly demonstrates the dangerous presence of Cd, Pb and other toxic elements in drink water sources. BIBLIOGRAFIE 1. J.A.Nobrega, Y.Gelinas, A.Krushevska, M.R.Barnes Determination of Elements in Biological and Botanical Materials by Inductively Coupled Plasma Atomic Emission and Mass Spectrometry After Extraction With a Tertiary Amine Reagent J.Anal.Atomic Spectr., Oct.01, 1997, H.Matusiewicz, M-Kopras Methods for Improving the Sensitivity in Atom Trapping Flame Atomic Absorption Spectrometry: Analytical 36

7 Scheme for the Direct Determination of Trace Elements in Beer J.Anal.Atomic Spectr., Nov.1,1997,12,11, G.J.Batterham, N.C.Munksgaard, D.L.Parry Determination of Trace Metals in Sea-water by Inductively Coupled Plasma Mass Spectrometry After Off-line Dithiocarbamate Solvent Extraction J.Anal.Atomic Spectr., Nov.1,1997,12,11, P.Thomas, J.K.Finnie, J.G.Williams Feasibility of Identication and Monitoring of Arsenic Species in Soil and Sediment Samples by Coupled High-performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry J.Anal.Atomic Spectr., Dec. 01, 1997,12,11, B.Boss Charles, J.Fredeen Kenneth Concepts, Instrumentation and Techniques in Inductively Coupled Plasma Optical Emission Spectrometry, Ed.Perkin Elmer 1997, International Labmate, 22,7, January S.W.Reader Guidelimes for Surface Water Quality Inorganic Chemical Substances Inland Waters Directorate, Ottawa, Canada, M.G.Lai, H.W.Weiss Anal.Chim.Acta, 143,3,

8 Table 1. The detection limits reached with the ICP system with pneumatic nebulizer Element λ Detection Medium concentration Allowed concentration [nm] limits [µg/l] rivers [µg/l] Sea [µg/l] in drink water [µg/l] Elements directly determined Na ,5*10 6 1,8*10 5 K 766, ,8*10 5 1,2*10 4 Mg 279, ,3*10 6 5*10 4 Ca 317, *10 5 1**10 5 Sr 407, Ba 455, Fe 259, B 249, S 180, ,8*10 5 8,3*10 4 Si 288, Elements determined after pre-concentration (20 X) Li 670, Be 313 0,1 0,4 6*10-4 Ve 311,1 2 0,9 2 Cr 267, ,05 50 Mo 281,6 4 1,5 10 Mr 257, Ni 231,6 8 1,

9 Cu 324, Zn 202, Al 308, P 178, Elements not determined after pre-concentration (20 X) Co 228,6 7 0,1 0,1 Ag 328,1 2 0,3 0,04 10 Cd 226,5 2 0,03 0,1 5 Hg 194,2 5 0,07 0,03 1 Pb 220, ,03 50 As 193, Sb 206, ,5 10 Bi 223,1 30 0,005 0,02 Se 196,1 80 0,2 0,4 10 Te 214,3 20 Table 2. Random errors in detection limits produced by Ca and Mg Element λ Detection Random errors [nm] limit [µg/l] Medium values in rivers [µg/l] Medium values in rivers (x 20) [µg/l] V 311,1 2 0,01 0,2 Ca 267,7 3 0,01 0,2 Ma 281,6 4 0,03 0,6 Ni 321,6 8 0,01 0,2 Zn 202,5 8 0,02 0,4 Si 288, Pb 220,3 20 0,1 2 P 178,3 10 0,03 0,6 S 180,7 80 6,1 120 Table 3. The pollutants content in fountainhead measured by ICP-OES Area Pb Cd Ag As Ca Cu In Zn Ti Sb Copşa Mică 0,0102 0,0229 0,0415 0, ,1 0,0249 0,0535 0,2883 0,0131 0,0481 fountain Copşa 0, , ,1 0,0051 0,0438 0,01 0, village fountain Prostea 0,0021 0, ,2 0,0085 0,0715 0,044 0,0126 0,0043 fountain Wevern Mediaş 0,0018 0, ,9 0,0093 0,0306 0,014 0,

10 spring Dumbrăven i fountain Iapu fountain Valea Lungă fountain Tîrnava Mare upper (Prostea) Tîrnava Mare beneath (Micăsasa) CMA (ppm) - 0, ,6 0,0105-0,0949 0, ,1 0,0049 0,0597 0,2285 0,0058 0,0008 0, ,5 0,0017 0,0638 0,0618 0,0105 0,0024-0,0003-0,002 88,24 0,0162 0,0817 0,0052 0,0006 0,0015 0,0098 0, ,97 0,124 0,052 0,0334 0,0026-0,05 0,005 0,01 0, ,05? 0,03?? 40