A n k a r a Ecz. Fak. D e r . 20, 1-2 (1990)
J. Fac. P h a r m . A n k a r a 20, 1-2 (1990)
Investigation of Trace Metal Accumulation Along Roadside Soil Using Aqua Regia As Extraction Media
Y o l Kenarlarındaki T o p r a k t a Eser Metal Birikiminin Kral Suyu Ekstraksiyonu İle İncelenmesi
Nevin VURAL* Cem YÜCESOY** Gülin GÜVENDİK*
S U M M A R Y
A simple procedure using aqua regia for the extraction of lead, c a d m i u m , zinc and nickel f r o m the soil was optimized. T h e recoveries are 94 % for lead, 95 % for c a d m i u m , 81 % for zinc and 86 % for nickel for the soil-type investigated.
Samples of roadside soil were collected along the highway E-5 at various locations and at b o t h sides between Ankara and Gölbaşı and at t w o circles, one being in the center of the city.
Lead, c a d m i u m , zinc and nickel content of the samples were deter-mined by flame atomic absorption spectrometry. Lead concentration-was the highest a m o n g four metals (ranged f r o m 77 p p m to 226 p p m ) . Z i n c and nickel concentrations of the soil were close to lead concentra-tion b u t wore lower than that. C a d m i u m concentraconcentra-tion was the lowest (ranged f r o m 1 p p m to 6 p p m ) .
Ö Z E T
Kurşun, k a d m i y u m , çinko ve nikelin topraktan kral suyu ile ekst-raksiyonuna dayanan basit bir y ö n t e m optimize edilmiştir. İncelenen
R e d a k s i y o n a verildiği tarih: 1 9 . 6 . 1 9 9 0
* Ankara University, S c h o o l of P h a r m a c y , D e p t . of T o x i c o l o g y * * Ankara University, S c h o o l o f P h a r m a c y , D e p t . o f Anal. Chemistry.
26 N e v i n V U R A L , C e m Y Ü C E S O Y , G ü l i n G Ü V E N D İ K
toprak cinsinde % geriye kazanım kurşun için % 94, k a d m i y u m için % 95, ç i n k o için % 81 ve nikel için % 86 dır.
Numuneler, E-5 karayolunun Ankara- Gölbaşı güzergahı üze-rindeki değişik noktalarda, y o l u n her iki tarafından ve biri şehrin içinde bulunan iki kavşaktan toplanmıştır. Numunelerde bulunan kurşun, k a d m i y u m , çinko ve nikel alevli atomik absorpsiyon spektrometrisi ile tayin edilmiştir. D ö r t metal arasında topraktaki konsantrasyonu en yüksek olan kurşundur (77-226 p p m ) . Çinko ve nikel konsantrasyon-ları kurşun konsantrasyonuna yakın olmakla birlikte daha düşüktür. K o n s a n t r a s y o n u en düşük olan metal ise k a d m i y u m d u r (1-6 p p m ) .
K e y W o r d s : Soil analysis; lead, c a d m i u m , zinc and nickel determi-nation: atomic absorption s p e c t r o p h o t o m e t r y .
A m o n g the nondegradable pollutants, h e a v y metal contamination of environment was widely studied because of the potential hazards to h u m a n health. Industrial processes and fossil fuel c o m b u s t i o n has led to substantial increase of the metals in the atmosphere, especially near urban areas and roadsides (1,2). Lead is p r o b a b l y the m o s t widespread contaminant, in the global environment. It is a d d e d to gasoline as tet-raethyl lead ( T E L ) against k n o c k i n g . It was shown that 70 % of lead exhausted as particle f r o m m o t o r vehicles and 85 % of the total par-ticulate emission is deposited by the roadside ( 3 ) .
Z i n c and c a d m i u m , as an impurity, c o m e f r o m lubricating m o t o r oils, tires and galvanized parts of vehicles. Nickel emission also results from nickel added to gasoline and by a t m o s p h e i i c abrasion of nickel containing parts of automobiles ( 4 ) .
A n u m b e r of studies on the h e a v y metal content of soil along the r o a d including lead, c a d m i u m , zinc and nickel and its relationship to traffic v o l u m e have been reported ( 5 - 9 ) .
In this w o r k , the lead, c a d m i u m , zinc and nickel contents of road-side soil along E - 5 , intercity highway, binding central Ankara to K o n y a through Gölbaşı were determined by a t o m i c absorption spectrometry. A simple extraction m e t h o d was investigated and the relationship bet-ween the metal contents and traffic density was studied.
Investigation o f the M e t a l A c c u m u l a t i o n A l o n g . 27
E X P E R I M E N T A L
Materials and Methods
Apparatus: Varian T e c h t r o n 1200, Flame atomic absorption
spect-r o p h o t o m e t e spect-r .
Reagents: Stock solutions containing 1000 g metal/ml were
prepa-red by using analytical reagent grade ( B D H ) Pb ( N O3)2, 3 C d S 04 .
8 H20 , N i S 04 . 7 H20 and Z n ( N O3)2 . 6 H20 .
W o r k i n g solutions were prepared by diluting of suitable aliquots of stock solutions with distilled water. T h e y were prepared freshly e v e r y d a y and kept in polyethylene bottles.
A q u a regia was prepared by mixing three v o l u m e s of concentrated h y d r o c h l o r i c acid and one of nitric acid.
Sampling sites and collection of soil samples: Six sites and t w o
junctions were selected along E—5 H i g h w a y between central Ankara and Gölbaşı along 30 km as shown in Figure 1. T a n d o ğ a n square is in the center of Ankara which is o p e n e d to highway through Çiftlik j u n c t i o n .
Annual average daily traffic ( A A D T ) along the highway was 7475 vehicles in 1986. T h e average traffic density between T a n d o ğ a n square and Çiftlik j u n c t i o n was 1306 vehicles/hour in the morning and 2385 vehicles/hour in the evening rush-hours (10). T h e highway runs in a north-south direction and consists of four lanes divided by a median b o u n d a r y .
Surface soil (0-3 c m ) samples collected f r o m the t w o sides of the highway and from the median b o u n d a r y according to Jackson (11).
Soil collections were m a d e in September 1986 and in September 1987. T h e weather was dry and temperature was 25°C during the samp-ling dates.
Sample treatment: Samples were allowed to air dry for a week (12).
T h e n each sample was ground t h o r o u g h l y in a mortar and passed through a 1 mm-sieve. Subsamples were then taken by the coning and quartering m e t h o d . F o r collection and treatment w o o d e n a n d / o r plas-tic material were used.
28 N e v i n V U R A L , C e m Y Ü C E S O Y , G ü l i n G Ü V E N D İ K
F i g u r e 1. S a m p l i n g sites at the j u n c t i o n s a n d E-5 H i g h w a y . Sampling sites are shown b y d o s t .
Analysis: T h e effect of acid v o l u m e and heating period on the
digestion of the metals f r o m the soil were investigated ( 7 ) . The follo-wing procedure was applied as the m o s t suitable m e t h o d : 0 . 5 0 0 g of soil samples were accurately weighed into 50 ml p y r e x conical flasks and digested with 5 . 0 ml aqua regia on a water-bath for 15 minutes. The stoppers were kept closed during the procedure. After digestion the samples were allowed to c o o l to r o o m temperature and filtered through W h a t m a n N o . 42 filter papers and m a d e up to 50 ml with dis tilled water. S o i l s a m p l i n g s i t e s TANDOCAN SQUARE GÖLBAŞI TOWN ESKIŞEHİR Ç İ F T L İ K JUNCTION K I Z I L A Y
I n v e s t i g a t i o n o f the M e t a l A c c u m u l a t i o n A l o n g . 29
Samples spiked w i t h 5 0 - 2 0 0 g.g - 1 lead, zinc and nickel and 1-2 g.g 1 c a d m i u m were analysed to c h e c k for m a t r i x interference.
B l a n k was p r e p a r e d b y diluting 5 . 0 m l a q u a regia t o 5 0 . 0 m l with distilled water. It is treated as m e n t i o n e d a b o v e for the sample solutions.
F o r the measurements o f lead, c a d m i u m , zinc and nickel b y ato-m i c a b s o r p t i o n s p e c t r o p h o t o ato-m e t r y , air-acetylene f l a ato-m e was used. A n a l y s e s were p e r f o r m e d a t w a v e l e n g t h s 2 1 7 . 0 n m (for l e a d ) , 2 2 8 . 8 n m (for c a d m i u m ) , 2 1 3 . 9 n m (for zinc) a n d 2 3 2 . 0 n m (for nickel).
R E S U L T S A N D D I S C U S S I O N
T a b l e 1 indicates that 5 ml a q u a regia a n d a heating p e r i o d of 15 m i n . ( W o r k i n g C o n d i t i o n N r . 9 ) is sufficient for digestion of lead, c a d m i u m , zinc and nickel f r o m the soil. A l t h o u g h in different w o r k i n g c o n d i t i o n s higher results m i g h t be o b t a i n e d for the metals, the differen-ces are n o t significant at the 95 % c o n f i d e n c e level.
T h e recoveries for the e x t r a c t a b l e a m o u n t s o f metals a d d e d t o the soil are 94 % for lead, 95 % for c a d m i u m , 81 % for zinc and 86 % for
T a b l e 1. T h e effects of acid v o l u m e and heating p e r i o d on the digestion o f m e t a l s f r o m the soil.
N o t e 1 . - a , allowed a t r o o m temperature for 1 5 minutes. 2 . * , w o r k i n g c o n d i t i o n s c h o s e n f o r f o l l o w i n g e x p e r i m e n t s . 3 . * * , t = 2 . 7 8 ( p = 0 . 0 5 ) . 4 . T h e c o n c e n t r a t i o n s are the arithme-tic m e a n o f three e x p e r i m e n t s . 5 . T h e determinations were carried o u t o n p o r t i o n s o f the same soil sample.
C O N D I T I O N S o f D I G E S T I O N M E T A L C O N T E N T ( p p m ) N o . V o l u m e o f a q u a regia a d d e d ( m l ) H e a t i n g p e r i o d ( m m ) N o . V o l u m e o f a q u a regia a d d e d ( m l ) H e a t i n g p e r i o d ( m m ) L e a d C a d m i u m Z i n c N i c k e l 1 2 3 4 5 6 7 8 9* 10 11 15 15 15 10 10 10 5 5 5 5 5 30 20 15 30 20 15 30 20 15 10 —a 278 ± 18 289 ± 27 285 ± 9 296 ± 44 293 ± 53 278 ± 18 285 ± 27 285 ± 35 296 ± 35 300 ± 62 228 ± 18 3 . 8 ± 0 . 5 4 . 0 ± 0 . 2 4 . 0 ± 0 . 7 3 . 8 ± 0 . 2 3 . 9 ± 0 . 2 3 . 8 ± 0 . 2 3 . 9 ± 0 . 2 3 . 9 ± 0 . 2 4 . 0 ± 0 . 3 4 . 0 ± 0 . 2 3 . 7 ± 0 . 2 139 ± 17 139 ± 25 123 ± 35 154 ± 49 135 ± 8 142 ± 58 142 ± 28 134 ± 7 145 ± 11 125 ± 9 112 ± 11 4 2 . 2 ± 1.3 4 4 . 3 ± 6 . 6 3 9 . 6 ± 3 . 9 4 2 . 7 ± 2 . 6 4 1 . 7 ± 1.3 3 8 . 5 ± 2 . 6 4 1 . 7 ± 2 . 6 4 2 . 2 ± 2 . 6 4 1 . 7 ± 2 . 6 3 7 . 5 ± 1.3 3 2 . 2 ± 1.3
30 N e v i n V U R A L , C e m Y Ü C E S O Y , G ü l i n G Ü V E N D İ K
nickel, respectively. B u t before accepting these values, the m e t h o d should be applied to another soil types as well.
Soil usually contains high levels of silicates, in the crystal lattice of which trace amounts of metal salts c o u l d be t r a p p e d . Somer and Ay-dm (9) stated that if the sample is heated immediately after adding the acid, a gel of silicic acid is formed which my slow d o w n the acid diffusion and consequently metal salts extraction. T h e formation of this gel can be prevented by allowing the sample to stand overnight in acid at r o o m temperature. Our observations confirmed that gel forma-tion did n o t affect the extracforma-tion of metal salts significantly and is in accordance with B e r r o w and Stein (13).
T h e arithmetic mean concentration of lead, c a d m i u m , zinc and nickel in the roadside soil investigated were shown in Table 2.
Surface soil lead levels ranged from 76 to 314 . g_ 1 ( p p m ) at T a n
-d o g a n square an-d from 102 to 298 p p m at the highway in 1986. L e a -d content of soil of T a n d o g a n square was the highest. This was attribu-table to higher traffic v o l u m e at T a n d o ğ a n Square than the highway traffic. Our results indicates that lead level of roadside soil in the highway is n o t as high as that in some U.S.A. highways (4,5,8), and in Istanbul ( 7 ) . This can be e x p e c t e d as the traffic is n o t as dense in the highway as those m e n t i o n e d . B u t the lead content of soil was found far higher than the initial lead level of the soil (16 p p m according to Swaine (14)). C a d m i u m levels of soil near the highway was found higher (mean 4 . 1 p p m ) than the T a n d o g a n square in the central Ankara (mean 3.5 p p m ) . A l t h o u g h the difference was n o t found significant, our results were far higher than m a n y other studies (4,6,7). Z i n c and nickel contents of the roadside soil were found at the same order but somewhat lower than lead.
No significant correlation between any pairs of lead, c a d m i u m , zinc and nickel were found (coefficient of correlation were ranged from 0 . 0 3 3 to 0250 in 1986 and f r o m 0 . 0 0 2 to 0 . 2 3 0 in 1987). Only in 1986, a correlation was found between lead and zinc at one side of E-5 highway (coefficient of correlation is 0 . 4 3 3 , p < 0 . 0 0 5 ) . Our results confirms with the findings of some authors (4) b u t differs from some authors(6).
Investigation of the M e t a l A c c u m u l a t i o n A l o n g . . . 31
T a b l e 2. Arithmetic m e a n concentrations of lead, c a d m i u m , zinc and nickel in roadside soil in t w o circles and 6 selected sites in E-5 highway.
Sampling 1986 September 1987 September
Site Mean ± Sd ( p p m ) Mean ± Sd ( p p m ) L E A D
T a n d o ğ a n Sq. Mean (n:7) 165 ± 89 173 ± 101
R a n g e 76 + 314 99 — 338
Çiftlik June. Mean (n:14) 152 ± 56 162 ± 67
R a n g e 102 — 298 94 — 326
E-5 Higliway Mean (n:18) 108 ± 36 152 ± 42
R a n g e 29 — 177 77 — 226
Z I N C
T a n d o ğ a n Sq. Mean (n:7) 184 ± 35 166 ± 20
R a n g e 141 — 263 144 — 199
Çiftlik June. Mean (n:14) 124 ± 26 120 ± 21
R a n g e 53 — 166 8 5 — T 6 6 E - 5 H i g h w a y Mean (n:18) 84 ± 48 108 ± 45 R a n g e 37 — 161 46 — 206 C A D M I U M T a n d o ğ a n Sq. Mean (n:7) 3 . 5 ± 1 . 2 3 . 4 ± 1.0 R a n g e 2 . 7 ± 6 . 2 1.8 — 5 . 4 Çiftlik June. Mean (n:14) 2 . 9 ± 0.8 3 . 3 ± 1.2
R a n g e 1.9 ± 4 . 3 1.5 ± 5.1 E-5 H i g h w a y Mean ( n : 1 8 ) 4 . 1 ± 1.5 4 . 4 ± 1.2 R a n g e 1.0 — 6 . 4 2 . 4 — 5 . 8 N I C K E L T a n d o ğ a n Sq. Mean (n:7) 127 ± 70 132 ± 84 R a n g e 67 — 249 64 — 284
Çiftlik June. Mean (n:14) 90 ± 15 88 ± 18
R a n g e 65 — 125 68 — 122
E - 5 H i g h w a y Mean (n:18) 78 ± 23 78 ± 26
R a n g e 39 — 118 20 — 117
A l t h o u g h metal levels in the roadside soil in 1987 were found so-mewhat higher than in 1986, the difference was n o t significant by Whit-ney U-test.
As conclusion; lead, c a d m i u m , zinc and nickel contents of soils adjacent to the highway and cityroads were found far higher than the ground level of those metals. Further studies are needed in T u r k e y to m o n i t o r trace metal accumulation on roadsides and find out the rela-tionship between trace metal concentrations and traffic, r o a d construc-tion t y p e , meteorological condiconstruc-tions, time and other factors.
3 2 N e v i n V U R A L , C e m Y Ü C E S O Y , G ü l i n G Ü V E N D İ K
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