A GLANCE OF OF CITY BY USING POPLAR LEAVES AND NAA TECHNIQUES

NIBANGFA, TIAN WEEK, WANGPINGSHENG, ZHANG YANGMEI, CHAO LEI, HE GAOKUI

China Institute of Atomic Energy, P.O. Box 275-50, Beijing, 102413, China XAO102858 Abstract:

Forty six Chinese White Poplar (CWP) leave samples were taken from different districts of Beijing proper and outskirt. 32 trace elements, As, Au, Ba, Br, Ca, Cd, Ce, Co, Cr, Cs, Eu, Fe, Iff Hg, K, La, Lu, Mo, Na, Rb, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, U, W, Yb and Zn have been determined by using relative and KQ method of instrumental neutron activation analysis (NAA) techniques. Each element was normalized by the average. Values of two times of average are considered as notable or suspected pollution. Three times of average are considered as very notable or polluted. In this case, the results indicated: 1) Clues of prominent suspected element pollution: Br is prominent in the area of heavy traffic, sites 4, 13, 27 and 38; Four sites (6, 7, 8, 9) at south of downtown are indicated the very notable level for Ni and Sb; Ca is relatively higher in the constructing area, sites 27 and 29; Sites 34 to 36 and sites 43 to 45 indicate the high concentration ofRb, both group sites are located at west of Beijing; At northwest, sites 25 to 28 show the notable level of Co. 2) Very notable pollution sites: In site 6, close to a railway station, concentration of 12 elements are more than two times higher than the average, especially Hf, Ni and Sb; In site 26, a high technical special zone, the concentrations of rare earth elements (REE) are more than 4 times of the average, Hfand Ta are extraordinary high. It might be some source from high technical zone; In site 38, the place close to the Iron and Steel Factory, has a extremely high concentration ofFe and Br, 8 and 5 times higher than the average, respectively. Co, Cr, Hf, K, Na, Ni, Rb and Se are also at notable level; In sampling site 42, located between downtown and outskirt, REE and As, Ba,Cr, Fe, Hf, Hg, Sc, Se, Ta, Th and Zn are shown in the notable level.

1. INTRODUCTION

Chinese economy developed rapidly in the past 20 years. At the beginning, environmental pollution was as long with the increase of economy, especial the air pollution. It once affected the human's health. In recent years, government has paid more attention and allocated a huge amount financial support to improve the environmental pollution problem. In Beijing, the capital of China, the government has took a series of measures to decrease the air pollution, such as replacing some by natural gas in industry and household; Leaded gasoline has been banned for 2 years; The air quality is reported to public every day, which include the contents of SO2, CO, NO2, O3 and density of inhalable air particles (toxic trace elements and organic phases are taking account). This is part of a program so-called "blue sky project". At the same time, another project so-called "green land program" is also bringing into effect. More and more places were covered by grasses, flowers and trees nowadays.

At present, the main means of air pollution monitoring is total suspended paniculate in China. Trace elements from size-fractionated air particulate matter (PM-10 and PM-2.5 sampler) are also used for air pollution studies. Biomonitors as indicator of air pollution have a long history. Most work have been done by Europe countries, such as The Netherlands! 1], Norway[2-3], Portugal[4-5] and Russian[6]. And lichen, moss and trees are usually used as biomonitors.

In China, the application of biomonitor for air pollution studies started recently. Air pollution in city has recently been studied using barks from different trees as

91 biomonitors[7-8]. Three kind of plant leaves, Chinese white poplar, arborvitae and pine trees as biomonitor for air pollution monitoring in Beijing area were studied[9] in last year. The results indicated poplar leaves is relatively better as a biomonitor, in case lichen and moss are difficult to collect.

In present work, 46 Chinese White Poplar leave samples were taken from different districts of Beijing downtown and suburb area to monitor the air pollution of Beijing during the season of spring to autumn. The results indicated that Br is prominent in the areas of heavy traffic; A high technical special zone shows the high concentration of REE and Cr, Hf, Sb, Sc, Ta, Th; Fe and Br are extraordinary high in the area around of the Iron and Steel Factory; Ca is relatively higher in the constructing area; Sb and Ni show strong correlation at south sampling sites.

2. SAMPLING

Forty six Chinese White Poplar leave samples were taken from different districts of Beijing proper and outskirt. It covers 70 km diameters of ellipse from west to east of Beijing city. The sampling sites are listed in Table 1 and marked in fig. 1, map of Beijing city proper (lined square attached at the bottom left comer is part of Beijing city map, shaded area is proper). Leaves were taken from the height of 2 to 3 meters above ground. Samples were collected during first week of August 1999, representing the integrated airborne paniculate matter status during spring and summer of 1999.

3. SAMPLE TREATMENT

Samples were washed by using a kind of soft detergent and distilled water. The washed samples were dried in an oven at a constant temperature of 50 °C for 48 hours, and then 80 °C for 24 hours. About 25 grams of the dried samples were crushed by using an agate roller. And grinded materials with the size of less than 40 mashes were used as the analytical samples.

4. SAMPLES AND STANDARDS PREPARATION

Around 300 mg of crushed sample was packed into a pure aluminum foil bag. 150 mg of NBS-1632a (Coal) was prepared in the same procedure for analytical quality controls. Pure metal wires or chemical compounds were 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 1 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.

5. 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 3xlO13 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,

92 industry factory, such as the Capital Iron and Steel Factory and Oil Refinery Complex. Both of them are located at southwest area of Beijing.

4) Quality Control: Two procedures were used for analytical quality control. First procedure is relative chemical standard and Ko method, each analytical indicator has two independent results: One is from relative and the other from ko method. They are listed in two columns at same time. If the difference is greater than 5% of outside uncertainties, the reason must be found. Another procedure is to use certified reference materials, such as NBS-1632a. In present work, the values between analytical and certified have a good agreement for 1632a, listed in Table 2.

Table 2, Analytical Results and literature Values of NBS-1632a, Quality Control

Element Anl. Error Literature Element Anl. Error Literature Value Value Value Value As 9.2 0.7 9.3 La 14.5 0.4 16 Ba 127 11 130 Na 846 18 840 Br 41 2 43 Rb 29 2 31 Ce 28.5 1.9 30 Sb 0.63 0.06 0.6 Co 6.6 0.2 6.8 Sc 6.22 0.32 6.3 Cr 35.4 1.6 34.4 Sm 2.5 0.3 2.3 Eu 0.51 0.03 0.54 Ta 0.36 0.04 0.4 Fe 11100 400 11100 Th 4.7 0.3 4.5 Hf 1.3 0.1 1.6 Yb 1.07 0.07 1.1 K 4400 200 4200 Zn 25.5 2.5 28

7. WORK IN THE FUTURE

1) Environmental and meteorological conditions for suspected sites (Very notable and notable sites) will be further investigated to reach more reasonable explanations of possible pollution sources. 2) Sampling in exiting sites (especially, the suspected sites) will continue, to study the elemental concentration variations with time and the change of surrounding situations. Sampling and NAA of CWP leaves will also be carried out in 10 to 15 new sites, to fill-up the relatively less sampled north areas. 3) Sampling sites will also be arranged around the Oil Refinery Complex in order to match the project contents. 4) Considerations have to be taken on the contributions of elements in CWP leaves from media other than airborne paniculate matter, e.g. soil and ground/rain water. Some lichen samples (although rarely found in Beijing) will be taken and analyzed to try to clarify the problem. Hopefully, that may bring some information on pollution from soil and water, as a by-product. 5) Sampling sites will be arranged close to the airborne particulate sampling site, where airborne particles is sampled once a week, in order to compare the pollution results from both biomonitor and air particle monitor.

93 REFERENCES

[1] J.E. Sloof, Ph. D. Thesis, Tu Delft, The Netherlands, Sep. 1993. [2] E. Steinnes, et al., J. Radioanal. Nucl. Chem., 114(1987)69. [3] E. Steinnes, et al., J. Radioanal. Nucl. Chem., 192(1995)205. [4] M.C. Freitas, et al., J. Radioanal. Nucl. Chem., 217(1997)17, [5] M.C. Freitas, et al., J. Radioanal. Nucl. Chem., 217(1997)22, [6] M.V. Frontasyeva, et al, J. Radioanal. Nucl. Chem., 181(1994)363, [7] Jiang Gaoming, Chinese J. of Applied Ecology, 7(1995)310. [8] Shang He, et al., J. shenyang Agr. Univ., 25(1994)98. [9] Ni Bangfa, at all, Biological Trace Elements Research, 1999(71 -72)267-272

94 Table 1, Beijing Poplar Sampling Sites and suspected pollutants Sampling Site and Name High Concentration Sub-High Cone. Element elements in sample 1. Tuoli Rb, Sb Cs 2. Liangxiang Ba, Se ,Hg 3. Daxing-Liangxiang Ba, Sr 4. Daxing Br,Ni Lu, Na, Rb, Sb 5. Daxing(2) As, Sb 6. Baiguanglu Hf, Ni, Sb, Ta Ce, Cr, Na, Se, Sm, Th 7. Xuanwumen Ni K, Rb, Sb 8. Hufangqiao Ni, Sb Zn 9. Tiantan Ni, Sb As, Zn 10. Muxidi 11. Fangzhuang Lu 12. Langjiayuan Sb, 13. Shuangqiao Br,Ni Co,Rb 14. Tongxian Lu 15. Tongxian(2) 16. Guanzhuang Lu 17. Balizhuang Ni 18. Hongmiao Sb 19. Changhongqiao Lu, Ni, Sr, Zn 20. Siyuanqiao Hg,Se,Br 21. Xiaoying Sr 22. Yayuncun Ni, 23. Datun Lu, Zn 24. Jianxiangqiao Sb, Sr 25. Zhongguancun Sr, Lu Co, Na, Rb, Zn 26. Sitongqiao Ce,La,Lu,Eu,SmTa, Cr, Sb, Se, Th 27. Weigongcun Br Hf 28. Baishiqiao Sb Co, Lu 29. Tianwenguan Rb,Ni 30. Chegongzhuang 31. Fuwaidajie 32. Ganjiakou As, Cr, Hf, Lu, Th 33. Fuchenglu 34. Gongzhufen Rb,Ni 35. Wanshoulukou Rb Zn 36. Yuquanlu Rb Sr, Lu, Zn 37. Shijingshan 38. Shougangqiangwai Fe,Br Co, K, Rb, Se 39. Xinqiaodajie Ba 40. Mentougou Ba 41. Liuliqu Ni 42. Wulidian Ta REE,As,Ba,H£Hg,Sc,Se,Th,Zn Fe,Tb 43. Lugouqiao Na, Ni, Rb Lu, Ta, K 44. Changxindian Hf, Ni, Rb, Ta 45. Zhaoxindian Rb 46. Changyang Co Hg,Ni,Zn

95 FI . ESl , Kl ,

" 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 |20 ¡15 10 i 5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 |8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 ¡6 4 \2

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1â 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 Fig. 2 Map of Br, Co, Ni, Sb and Rb for 46 sampling sites

9 te-6

AsBaBrOaCeCoCrQsEuFeHfi Hg K—La-4 j Ma N—Rb Sb Se Se Sm Sr Ta Th Zft- ^PopSite-26

asa . ma . m

10 u ^ U3 u es bu i-e m Ra M K) so se be am sr la in ¿n

Ba Br Ca rb rv\ Crvr Cr>S Eu 4aI -,- I M Mn N—Rb Sb Se Se Sm Sr Ta Th 2 i te-42

¿sBaBrCaCeCo&CsEuFeHfHgK La Lu Na Ni FbSbScSeSmSrTaThZn Fig. 3 Elements Distribution of sampling sites 6, 26, 38 and 42

96