XA9952953 STUDY ON AROUND CHINA'S LARGEST OIL REFINERY COMPLEX USING MULTIELEMENTS IN BIOMONITORS AND NEUTRON ACTIVATION ANALYSIS TECHNIQUES

Nl BANGFA, HE GAOKUI, TIAN WEIZHI, NIE HUINING, WANG PINGSHENG China Institute of Atomic Energy P.O. Box 275-50, 102413, China

Abstract

Three different kinds of plant leaves, Chinese white poplar, arborvitae and pine needle have been sampled from different places, Yanshan Oil refinery complex. Capital Iron and Steel Factory and Badachu, a control place in Beijing, as bio-monitors for air pollution studies. Each sample was divided into two parts, washed and unwashed, 31 trace elements. As, Au, Br, Ca, Cd, K, La, Lu, Mo, Na, Sb, Sm, U, W, Yb, Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Rb, Sc, Se, Sr, Ta, Tb, Th and Zn have been determined by using KO method of instrument neutron activation analysis techniques with a long irradiation in the 15MW Heave Water Research Reactor, China Institute of Atomic Energy. The results indicated that: 1) the concentration of trace elements in unwashed samples are much higher than that in washed samples; 2) the area of capital iron and steel factory is polluted heavily, and Yanshan oil refinery complex area is polluted moderately; 3) All the three kinds of plant leaves can be used as air pollution biomonitors, because they can absorb some trace elements from the air pollutants. Aspen is good for monitoring in particular seasons and Pine needle is better than arborvitae for yearly monitoring; 4) Elements of As, Cd, Hg, Co, Rb, Sb, W and Zn are highly absorbed by Chinese white poplar. Pine needle is sensitive to absorb the elements of Br, Cr, Cd, Fe, Sc, Cs and rear earth elements, but arborvitae is very sensitive for the absorption of Sr.

1. INTRODUCTION

Biomonitors as indicator of air pollution have a long history. A book entitled "Air pollution and lichens" was published in 1977[1]. A recent summary on this topic was given by M. De Bruin[2]. A kind of lichen samples have recently been collected all over Portugal and analyzed for 44 elements by NAA and PIXE for a nation wide survey of air pollution[3-4]. Similar work was also done in The Netherlands[5] and Norway[6-7].

In China, most of air pollution studies so far have been based on the atmospheric aerosol by air sampler for TSP or PM-10. The disadvantage of this method is that it can only monitor the sampling times. In recent years, the application of biomonitor for air pollution studies has been increased. For example, air pollution in city has recently been studied using barks from different trees as biomonitors[8-9]. In present work, we are trying to search for a suitable kind of plant leave as biomonitor for air pollution studies in Beijing Area. It will be used to indicate the air pollution status for a long period of time. In north China, it is difficult to find moss or lichen because of the dry weather. But the poplar or Chinese white poplar is widely spread in north China. And arborvitae and pine trees are planted all over the country. So these three kinds of tree leaves have been selected as candidates of biomonitors and sampled at different places, Yanshan Oil refinery complex, Capital Iron and Steel Factory and Badachu (a control place). The results indicate that Chinese white poplar is a good seasonable air pollution and pine needle is good for yearly monitoring.

60 2. EXPERIMENT

2.1. Sampling

Three different kinds of plant leaves, Chinese white poplar, oriental arborvitae and pine needle have been sampled at different places, Yanshan Oil refinery complex (a chemical industry area), Capital Iron and Steel Factory (a heave polluted area) and Badachu (a control place). Leaves from the height of 2 to 3 meters were chosen. The oldest leaves of Chinese white poplar, the pine needle and oriental arborvitae leaves grown in last year are chosen as bio-monitors of air pollution studies.

2.2. Sample Treatment

Each sample was divided into two parts. One was washed by using a kind of soft detergent and distilled water. Another is unwashed but with hardly whisking dust from the leaves. The washed and unwashed samples were dried in an oven at a constant temperature of 50 OC for 48 hours, and then 80 OC for 24 hours.

The dried samples were crushed by using an agate roller. And the size of less than 40 mashes were used as the analytical samples.

2.3. Sample and Standards Preparation

Around 300 mg of crushed sample was sealed into a pure aluminum foil bag. 150 mg of NBS-1632a () and 250 mg of NBS-1575 (pine needle) were prepared in the same procedure for analytical quality controls. Pure metal wire or chemical compounds was dissolved and mixed into a reasonable multi-elements solution, and then dropped on the ashless filet paper with the size of O7X2 mm pad. Around 2 mg each of Pure zirconium foil and iron wire were prepared as the neutron flux monitor and comparator for KO method respectively. All the samples, controls, monitor and comparator were packed together and put into an irradiation can.

2.4. Irradiation and Counting

Samples was put into a vertical channel of the 15 MW heave water research reactor, China Institute of Atomic Energy, and irradiated for 48 hours at position with the neutron flux of 3.5x1013 n cm-2 S-1. Irradiated samples with the Al bag removed were counted in 3000 seconds by using a HPGe, PCA-II multichannel board and computerized gamma spectrometer system (with resolution of 2.1keV and relative efficiency of 30% for 1332.5 keV and peak/Computton ratio of 50:1) after 5 days decay for the determination of As, Au, Br, Ca, Cd, K, La, Lu, Mo, Na, Sb, Sm, U, W and Yb, and another 5000 seconds was counted after 12 days decay for the determination of Ba, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Rb, Sc, Se, Sr, Ta, Tb, Th and Zn.

3. RESULTS AND DISCUSSION

3.1. Results

Thirty one trace elements have been determined by NAA. The results of the washed and unwashed samples are listed in Table 1 and Table 2, respectively.

3.2. Content Differences Between Washed and Unwashed Samples

Table 1 and Table 2 indicate that the concentrations of trace elements in unwashed samples are much higher than those in washed samples, especially for the

61 rare earth elements and Hf, Cr, Co and Fe etc. Data from both washed and unwashed samples show that the area of capital iron and steel factory is heavily polluted and the oil refinery complex area is taken second place which are indicated in Table 1 and Table 2.

3.3. Pollution Status

Figures 1, 2, 3 give the trace element contents normalized by those from Badachu samples, which are considered to be relatively unpolluted. From Figure 1, 2 and 3, we can see that all the three kinds of leaves can be used as biomonitors for air pollution studies. Figure 1 indicate that the concentration of most elements in Chinese white poplar are increased along with the air pollution status, such as As, Br, Cd, Fe, Hg, Co, Rb and W etc. Because poplar leaves grow in the Spring and fall off in the Autumn, it is good for monitoring in the period of Spring to Autumn. For the yearly monitoring, arborvitae and pine needle are possible. From Figure 1 and 2, pine needle as a biomonitor is better than arborvitae. But from Table 1, we can see the concentrations of most elements in arborvitae are higher than those in pine needle.

3.4. Quality Control

Two procedures were used for analytical quality control. 1) relative chemical standard and KO method, each analytical indicator has two independent results: One is from relative and another from kO method. They are listed in two columns at same time. If the difference is greater than 5% of the indicator, the reason must be found. Another routine is to use certified reference materials as unknown samples, such as NBS-1632a and pine needle. In present work, the values between analytical and certified have a good agreement, especially for 1632a.

4. WORK IN THE FUTURE

4.1. Continue to sample these three kinds of leaves together with soil and atmospheric aerosol particulate by PM-10 sample to clarify if the trace elements are from air pollutants or from the soil.

4.2. According to the above results, we found that the concentrations of most trace elements in arborvitae are higher than Chinese white poplar and pine needle at same place. The content of trace elements in arborvitae leave and pine needle will be determined at same branch but different grown time, respectively. So that we can study the air pollution at different period of time and make a conditional sampling procedure.

4.3. 200 sampling points will be arranged in Beijing downtown area with a radius of 15 km by using Chinese white poplar leaves as a biomonitor for the study of air pollution.

REFERENCES [1] B.W. Ferry, et al, Air pollution and lichen, Athlone Press, London, 1977 [2] M.De Bruin, IAEA Bulletin, 4(1990) 22 [3] M.C. Freitas, at al., J. Radioanal. Nucl. Chem., 217(1997)17, [4] M.C. Freitas, at al., J. Radioanal. Nucl. Chem., 217(1997)22, [5] J.E. Sloof, Ph. D. Thesis, Tu Delft, The Netherlands, Sep. 1993. [6] E. Steinnes, et al., J. Radioanal. Nucl. Chem., 114(1987)69. [7] E. Steinnes, et a!., J. Radioanal. Nucl. Chem., 192(1995)205. [8] Jiang Gaoming, Chinese J. of Applied Ecology, 7(1995)310. [9] Shang He, et al., J. Shenyang Agr. Univ., 25(1994)98.

62 Table 1. The NAA results of the washed samples* Sample ID Arborvit POPLAR PINE Arborvit POPLAR PINE Arborvit POPLAR PINE ae-ctl -ctl NEEDLE ae-isf -isf NEEDLE ae-orc -ore NEEDLE -ctl -isf -ore As ng/g 891 688 370 528 4985 310 596 845 649 Au ng/g 1.18 0.91 0.30 0.31 0.53 0.33 0.30 1.00 1.79 Ba ug/g 18.3 11.2 3.29 18.5 14.9 3.68 47.5 32.6 9.88 Br ug/g 1.82 1.70 0.98 6.54 8.08 3.54 4.72 2.67 3.69 Ca mg/g 10.9 14.7 3.56 10.7 13.2 4.06 17.3 19.3 10.1 Cd ng/g 804 366 0 2360 1365 0 0 1133 0 Ce ng/g 880 189 141 812 684 230 1145 225 251 Co ng/g 272 485 84 231 3195 147 326 1140 86 Cr ng/g 1145 316 144 1480 1290 369 1190 436 364 Cs ng/g 78 28 13 84 80 74 133 75 31 Eu ng/g 15.0 4.33 3.28 13.1 9.29 3.26 18.5 5.07 Fe ug/g 801 213 133 4595 1845 718 684 269 188 Hf ng/g 57.5 13.8 6.2 39.2 66.5 11.3 60.6 11.9 13.1 Hg ng/g 33.8 30.6 40.6 12.9 55.3 55.6 53.0 90.0 36.4 K mg/g 6.2 5.8 6.0 7.3 18.2 2.2 9.8 13.6 4.5 La ng/g 564 123 85.5 Ml 401 145 779 217 175 Lu ng/g 5.0 0.8 8.0 4.0 1.0 4.7 1.5 Mo ng/g 788 507 Na ug/g 171 85.4 755 110 202 140 146 87.5 50.1 Rb ug/g 1.5 1.4 0.9 1.3 10.9 3.4 3.5 10.9 1.3 Sb ng/g 1085 279 3875 285 600 2885 707 529 15900 Sc ng/g 149 34.6 18.1 106 96.6 32.8 167 41.9 36.0 Se ng/g 55.5 464 42.1 285 361 87.4 Sm ng/g 69.4 19.7 9.8 57.6 60.8 16.7 83.2 27.9 17.7 Sr ug/g 47.0 66.3 32.3 93.2 78.5 128 151 64.1 Ta ng/g 12.2 1.8 8.4 5.3 3.3 11.8 3.8 Tb ng/g 2.7 13.6 Th ng/g 180 41.3 18.8 138 129 45.4 196 48.7 44.6 U ng/g 54.8 39.5 32.2 73.0 W ng/g 86.2 42.1 300 100 304 75.1 216 343 Yb ng/g 33.5 4.9 26.3 20.4 7.7 44.3 11.3 Zn ug/g 24.3 83.5 13.5 25.2 103 30.9 29.4 182 21.2

* Note: ctl, isf and ore representing the control place, iron and steel factory and oil refinery factory, respectively

63 Table 2. The NAA results of the unwashed samples Sample ID POPLAR POPLAR POPLAR ARBOR ARBOR ARBOR PINE PINE PINE -ctl -isf -ore VITAE- VITAE- VITAE- NEEDLE- NEEDLE- NEEDLE- ctl isf orfc ctl isf orc As ug/g 1.26 11.70 1.49 1.15 1.47 1.06 0.70 0.94 1.01 Au ng/g 0.24 0.78 1.38 1.02 0.53 0.68 0.95 0.73 2.78 Ba ug/g 11.3 27.2 47.7 25.0 38.0 43.5 5.8 12.7 11.7 Br ug/g 1.95 8.19 2.69 1.82 7.40 3.54 1.22 3.81 3.22 Ca mg/g 11.0 13.9 20.3 9.0 15.3 16.5 4.7 4.9 10.9 Cd ug/g 0.13 3.19 1.61 9.61 4.54 1.49 Ce ng/g 309 2550 559 1570 2160 1910 193 788 341 Co ng/g 526 1690 1400 439 645 440 92 304 139 Cr ng/g 517 3480 799 2050 4610 1960 378 1740 501 Cs ng/g 35 228 121 131 187 224 22 119 43 Eu ng/g 6.7 42.5 10.2 24.4 34.2 30.4 11.9 Fe mg/g 0.40 4.81 0.50 1.57 18.30 1.16 0.27 6.66 0.29 Hf ng/g 23.1 285.0 36.5 112.0 127.0 110.0 15.7 63.4 15.9 Hg ng/g 53.1 65.4 101.0 9.3 26.1 100.0 26.0 58.6 84.7 K mg/g 6.41 20.00 11.70 6.00 6.44 7.56 4.20 2.31 4.65 La ng/g 219 1440 391 847 1360 1220 161 449 279 Lu ng/g 1.64 2.45 7.87 10.70 0.81 4.18 1.66 Mo ng/g 86.0 587.0 352.0 Na ug/g 60 545 117 213 240 284 416 163 78 Rb ug/g 1.60 12.10 10.20 2.21 3.03 3.47 0.66 3.49 1.54 Sb ug/g 0.24 0.90 0.36 1.19 1.43 1.54 8.54 12.70 24.20 Sc ng/g 58 387 91 252 328 289 38 119 58 Se ng/g 560.0 517.0 59.4 492.0 3.8 120.0 87.7 Sm ng/g 32 232 52 123 169 137 19 54 29 Sr ug/g 64.5 68.5 181.0 39.3 96.2 92.8 43.2 76.5 Ta ng/g 5.2 33.9 6.2 23.5 32.1 22.5 Tb ng/g 43.00 18.50 27.10 Th ng/g 66 489 104 309 408 319 46 152 73 U ng/g 10.9 147.0 46.5 103.0 117.0 W ng/g 42.2 337.0 152.0 137.0 292.0 135.0 Yb ng/g 10.0 93.6 23.6 57.6 73.9 65.7 16.0 Zn ug/g 85.2 119 187 29.3 36.7 27.9 11.9 28.2 21.4

64 BAspen-ctl • Aspen-isf • Aspen-ore

As Au Ba Br Ca Cd CeCoCr CsEu Fe HfHg K La Lu Mo Na Rb Sb Sc Se Sm Sr Ta Tb Th II I ft Zn Fig. 1. Element content of Aspen in different places normalized by control place

EArborvitae-ctl Arborvitae-isf DArborvitae-orc

'•Hi As Au Ea Br Ca Cd Ce Co Cr Cs Eu Fe Hf Hg K La Lu Mo Na Rb Sb Sc Se Sin Sr Ta Tb Th U W Yb Zn Fig. 2. Element content of Arborvitae in different places normalized by control place

CJP ineNeedl-cti ^XV-'^-'-' i Os^ "• *"\ PineNeedl-isf PineNeedl-orc

AsAuBiiBrCetCdCeCoCrCsEuFeHfHj K LaLuMoNaRbSbScSeSuSrTaTbThU W YbZn

Fig. 3. Element content of pine needle in different places normalized by control place

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