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ABSTRACT Nitrate-nitrogen (NO3-N) contamination in groundwater has been worldwide concern, and especially it is a critical issue for the region depending on groundwater for water supply. Kumamoto city depends on only groundwater for all of water supply, however, lowering groundwater level and increasing NO3-N concentration have been revealed recently. In this study, the current situation of NO3-N contamination in the groundwater of Kumamoto city was investigated. Nitrate-nitrogen was detected in the range from 0.2 to 5.8 mg/l in the groundwater of deep wells at 22 points out of total 30 sampling points including drinking water resource. The NO3-N concentration was closely related to the location of wells and groundwater flow. The upward tendency in NO3-N concentration was recognized at a number of wells for recent 20 years, and it was considered due to the agricultural activity in the corresponding area and their upstream areas.
Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 19 - Present Status and Feature of Groundwater Contamination by Nitrate-nitrogen in Kumamoto City Kazuo TOMIIE*, Yasuhiro IWASA**, Kaori MAEDA**, Michiko OTSUZUKI**, Tsutomu YUNOUE**, Ryuji KAKIMOTO*, Yasunori KAWAGOSHI* *Department of Civil and Environmental Engineering, Kumamoto University, Kurokami 2-39-1 Kumamoto, 860-8555, Japan **Kumamoto City Waterworks Bureau, Suizenji 6-2-45, Kumamoto, 862-8620, Japan ABSTRACT Nitrate-nitrogen (NO 3 -N) contamination in groundwater has been worldwide concern, and especially it is a critical issue for the region depending on groundwater for water supply. Kumamoto city depends on only groundwater for all of water supply, however, lowering groundwater level and increasing NO 3 -N concentration have been revealed recently. In this study, the current situation of NO 3 -N contamination in the groundwater of Kumamoto city was investigated. Nitrate-nitrogen was detected in the range from 0.2 to 5.8 mg/l in the groundwater of deep wells at 22 points out of total 30 sampling points including drinking water resource. The NO 3 -N concentration was closely related to the location of wells and groundwater flow. The upward tendency in NO 3 -N concentration was recognized at a number of wells for recent 20 years, and it was considered due to the agricultural activity in the corresponding area and their upstream areas. Keywords: groundwater, contamination, nitrate-nitrogen (NO 3 -N), water quality, drinking water. INTRODUCTION Kumamoto city is an exceptional midsize city, in that 100 % of water supply for about 700 thousands people depends on only groundwater. In addition, water quality of groundwater in Kumamoto city is quite excellent and renowned as good-tasting water in Japan (Hashimoto, 1989). However, decline in the water amount caused by the decrease of a recharge area has been addressed in recent years, and also water quality aggravation such as nitrate contamination is currently identified (Kumamoto City Water Works, 2006; Tsuru et al, 2006). Nitrate contamination of groundwater is a worldwide problem (Tayfur et al, 2008; Shomar et al, 2008; Hu et al, 2005; Nas and Berktay, 2006; Showers et al, 2008; Kumazawa, 2002), especially in agriculture area caused by over fertilizing and insufficient control of livestock-waste. Kumamoto city and the surrounding districts are also agricultural areas, and the gradual elevation of nitrate concentration has become obvious in the groundwater of these areas (Kumamoto City Water Works, 2006). The drinking water standard and ground water quality standard of nitrate nitrogen (NO 3 -N) in Japan were both determined below 10 mg/l according to the recommendation by World Health Organization (WHO) based on the relationship between nitrate intake and methemoglobinemia in infants (WHO, 1970). Since groundwater is the only drinking water resource for Kumamoto city, nitrate contamination of the groundwater will be a serious issue for the future, thus the urgent study on present status and countermeasures must be required. In addition, knowledge obtained from the study on nitrate contamination in Kumamoto city-groundwater might Address correspondence to Yasunori Kawagoshi, Department of Civil and Environmental Engineering, Kumamoto University, Email: goshi@kumamoto-u.ac.jp Received December 18, 2008, Accepted January 28, 2009. Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 20 - be valuable for water environmental administration of other districts where groundwater is important water resource. In this study, the present status and long-term change of nitrate-nitrogen concentration in Kumamoto city-groundwater are investigated and discussed. MATERIALS AND METHODS Subsurface geological structure and groundwater flow in Kumamoto city area Kumamoto prefecture is located at center of Kyushu area in southern part of Japan (Fig. 1). Kumamoto city is the prefectural capital with a 670,000 population and the 267 km 2 area. Kumamoto city depends on 100 % of water supply with only groundwater. Kumamoto prefecture Kumamoto City Kyushu area Fig. 1 - Location of Kumamoto city in Japan. The bed rock in Kumamoto city and its surrounding areas consist mainly of the Pre-Aso volcanic rock, and Aso-pyroclastic flow deposits, which are called Aso1, Aso2, Aso3 and Aso4, cover it in chronological order. The most important groundwater from the perspective of water resource is the second aquifer which flows mainly in the Aso3-lava bed. There are some impermeable beds called Futa-bed and Hanabusa-bed between Aso-3 bed and Aso-4 bed in places, however, all of these areas are not always covered with impermeable beds. Therefore the influent water from a ground surface can easily reach the second aquifer through the first aquifer (Aso-4 bed) in some places where there is no impermeable bed. Figure 2 shows partial subsurface geological structure and groundwater flow in the second aquifer in Kumamoto city (Nagai et al, 1983; Kumamoto prefecture and Kumamoto city, 2005) with sampling points. In Kumamoto city, the areas except western part are covered with the Aso-1~4 lava beds, and the middle area from northeast to the central part lacks the impermeable bed between Aso-3 bed and Aso-4 bed. The northwestern area has Kimbo volcano where the geological condition is different from those of Aso-lava beds and the third aquifer flows in this area. The southwestern part is alluvial area covered with muddy sediment, thus there is not any Aso-lava beds in this part. Groundwater flow in the second aquifer in Kumamoto city is roughly indicated by the arrows in Fig. 2. The main water flow is from the western foot of Mt. Aso to Ariake Sea through the middle-southern part of the city. The area called “Shira river-midstream basin” which extends across Ozu town and Kikuyo town located between Mt. Aso and Kumamoto city is also considered as an important groundwater recharge zone. In addition, the groundwater flows from Kikuchi plateau (north east) and Ueki plateau (north west) contribute the water resource for Kumamoto city. Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 21 - Mountain or volcano Area with impermeable bed Alluvial area Area without impermeable bed Kinbo volcano Mt. Aso Shira River Ariake Sea Ueki Plateau Kikuchi Plateau 1 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 1 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 Lake Ezu Fig. 2 - Partial subsurface geological structure and groundwater flow in the second aquifer (the third aquifer in Kinbo volcano area) in Kumamoto city with sampling points. The allows indicate groundwater flow. Location and grouping of sampling points based on groundwater quality characteristics Figure 3 shows the locations of groundwater sampling points and the regional groups where water-quality characterization analysis was performed previously (Tsuru et al, 1998; Kawagoshi et al, in submission). A total 40 groundwater samples at 30 sampling points were collected and investigated during high-water season (September to November) in 2006. The depth and purpose of the wells are summarized in Table 1. The regional groups characterized by water quality are almost depending on their location and groundwater flow. The distinctive water quality characteristics of each group is as follows: Group 1: dissolved components (DCs) amount is low and soluble silicate concentration is high, Group 2: concentrations of F ion and boron are high, Group 3: DCs amount is high, Group 4: sulfuric ion concentration is high, Group 5: F ion is involved, Group 6: Cl ion concentration is high and reductive atmosphere, Group 7: DCs amount is quite low (main groundwater flows in the third aquifer and water quality characterization was conducted using the third aquifer-groundwater). Nitrate-nitrogen analysis The NO 3 -N concentration in the groundwater was determined by using ion exchange chromatography according to Japanese Standard Methods for Examination of Water (Japan Water Works, 2001). Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 22 - Table -1 List of the wells for survey in this study No. Well depth Intake depth Purpose Note 18 41 24.7~35.7 monitoring (m) (m) 112 95.3~106.3 monitoring 1 general use 19 32 15.5~26.5 monitoring shallow 2 60 54.0~59.5 monitoring shallow 81 59.0~75.5 monitoring deep 100 83.5~94.5 monitoring deep 65 39.5~55.4 monitoring deep 3 general use 21 10 4.9~9.9 monitoring shallow 4 general use 55 44.0~55.0 monitoring deep 5 general use 22 general use 6 general use 23 46 31.7~42.7 monitoring shallow 7 general use 155 121.5~138.0 monitoring deep 8 110 71.4~93.5 monitoring 24 general use 9 general use 25 109 71.9~93.7 monitoring shallow 10 100 unknown monitoring 135 113.0~129.5 monitoring deep 11 137 120.5~131.5 monitoring 26 15 6.8~12.3 monitoring shallow 12 71 48.0~59.0 monitoring 210 127.5~149.5 monitoring deep 13 general use 27 10 4.5~10 monitoring shallow 14 56 39.0~50.0 monitoring 145 112~145 monitoring deep 15 general use 28 general use 16 35 22.3~33.3 monitoring shallow 29 general use 110 97.0~108 monitoring deep 30 110 71.5~82.5 monitoring 17 115 82.3~98.8 monitoring Mt. Aso Ariake Sea Ueki Plateau Kikuchi Plateau 1 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 1 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 Group 7 Group 1 Group 3 Group 4 Group 5 Group 6 Group 2 Group 7 Group 1 Group 3 Group 4 Group 5 Group 6 Group 2 Fig. 3 - Location of sampling points and grouping characterized by the water quality of groundwater. Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 23 - RESULTS AND DISCUSSION Overall situation of groundwater contamination by NO 3 -N in Kumamoto city Figure 4 shows NO 3 -N concentration in the groundwater at each sampling point in autumn 2006. Only data for deep well are shown for the sampling points of nos. 2, 16, 18, 19, 21, 23, 25-27 which have both deep well and shallow well. Nitrate-nitrogen was principally detected at 22 sampling points located in the area except middle- and southwestern-part. The NO 3 -N concentration range was 0.2~5.8 mg/l, and average and median were 3.0 and 3.1 mg/l, respectively. Figure 5 shows the NO 3 -N concentrations in the deep well and shallow well at nos. 2-27 sampling points mentioned before. Nitrate-nitrogen was not detected even in shallow wells in the southwestern part (nos. 23, 25-27), but detected in shallow wells in the middle part such as nos. 19 and 21. In other areas (nos. 2, 17-19), NO 3 -N concentration in shallow wells was higher than that in deep well. Figure 6 shows the long-term variation in NO 3 -N concentration in deep well at the sampling points representing each water quality-group. The NO 3 -N concentration remained almost the same level for about recent 10 years at nos. 17 and 30 sampling points, but upward tendency was observed in other sampling points. Mountain or volcano Area with impermeable bed Alluvial area Area without impermeable bed Mt. Aso Ariake Sea Ueki Plateau Kikuchi Plateau 1 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 Fig. 4 - Concentration of NO 3 -N in groundwater of the second or third aquifer (nos. 29 and 30) in Kumamoto city (autumn, 2006). Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 24 - Mountain or volcano Area with impermeable bed Alluvial area Area without impermeable bed Mt. Aso Ariake Sea Ueki Plateau Kikuchi Plateau 2 21 16 18 23 25 26 27 19 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 Fig. 5 - Concentration of NO 3 -N in groundwater of shallow well (black bar) and deep well (white bar) at some sampling points in Kumamoto city (autumn, 2006). Situation at northern part (Group 1 and Group 2 areas) In this part, NO 3 -N was detected at any sampling points in a concentration range from 3.2 to 5.4 mg/l. It is presumed that the main groundwater flow into the second aquifer of Group 1 area is from Ueki plateau, and that of Group 2 area is from Kikuchi plateau. Additionally, the water flow from Kinbo volcano into no.3 point and the water flow from Shira river-midstream basin into nos. 6 and 7 points are also presumed. The NO 3 -N concentration in this area was relatively higher than that in other areas, suggesting the presence of a contamination source of NO 3 -N in this area or upstream site. There is impermeable bed in this area except no. 7 point, thus direct NO 3 -N input from a land surface in this area. On the other hand, it was reported that the groundwater at some places in Ueki plateau area was highly polluted with NO 3 -N caused by over fertilizing or inappropriate treatment of livestock wastes (Kumamoto prefectural institute of public-health and environmental, 2000). Kikuchi plateau is also known as an active agricultural area, and crops such as melon and watermelon are famous as a brand-name. Therefore, high NO 3 -N concentration in the groundwater of this part is considered mainly due to the groundwater inflow from these upstream areas. In Ueki city, various measures have been continued to prevent NO 3 -N contamination of groundwater such as fertilizer-management for about recent 10 years, however, the NO 3 -N concentration is still increasing as shown in Fig. 6. Needless to say, continuous monitoring of the groundwater is needed in this area, moreover, further cross-regional efforts to prevent NO 3 -N pollution in the upstream areas should be required. Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 25 - Group 7 Group 1 Group 3 Group 4 Group 5 Group 6 Group 2 0 1 2 3 4 5 95 97 99 01 03 05 0 1 2 3 4 85 88 91 94 97 00 03 06 0 1 2 3 4 95 97 99 01 03 05 0 2 4 6 8 85 88 91 94 97 00 03 06 0 1 2 3 95 97 99 01 03 05 0 1 2 3 4 85 88 91 94 97 00 03 06 0 1 2 85 88 91 94 97 00 03 06 0 1 2 95 97 99 01 03 05 No.7 No.9 No.11 No.15 No.17 No.22 0 0.1 0.2 0.3 0.4 85 88 91 94 97 00 03 06 No.28 No.2 No.30 Fig. 6 - Long-term variation in NO 3 -N concentration of groundwater at the sampling points representing each water-quality group. Situation at eastern part (Group 3 area) and southeastern part (Group 4 area) The groundwater in these areas is the most important as the water resource for Kumamoto city. There is a huge lava bed called Togawa lava bed lying beneath the Group 4 area, and a large amount of groundwater flow into Togawa lava bed from various directions. Nitrate-nitrogen was detected at all sampling points as well as in the northern part, and the highest concentration was detected at no. 9 point in the Group 3 area. At least, it seems that the groundwater is contaminated before it flows into the Group 4 area because the NO 3 -N concentrations were high and showed upward tendency in the zone having impermeable bed (nos. 13-16 points). At nos. 16 and 18 sampling points, the NO 3 -N concentration in shallow well was higher than in deep well as shown in Fig. 5, indicating that the groundwater in the first aquifer was contaminated by NO 3 -N in this area. The groundwater flow in the first aquifer is determined to be almost same as that in the second aquifer in the Group 3 and 4 areas (Kumamoto prefecture and Kumamoto city, 2005), thus it is presumed that the groundwater in the shallow well is also contaminated in upstream area. The NO 3 -N concentration has been flat at no. 17 point for recent 10 years, suggesting no further NO 3 -N pollutant source and the possibility of denitrification activity around here as well as the Group 5 and 6 areas described below. While the Group 4 area is regarded as being groundwater storage area, the Group 3 area plays the role of groundwater recharge especially in the place Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 26 - around nos. 8 and 9 points because of no impermeable bed there. In addition, the Group 3 and further eastward areas are covered with vast upland field as shown in satellite pictures given by Kumamoto city government (Home page of Kumamoto city) and dotted with many livestock farmers. Therefore, not a little influence of these agricultural activities on the NO 3 -N contamination is considered. In fact, the wells containing NO 3 -N of over 10 mg/l have been found in the Group 3 area (Tsuru et al, 2005; 2006). The recharge amount of groundwater in the Shira river-midstream basin shows downward trend (Kumamoto prefecture and Kumamoto city, 2005; Ichikawa et al, 1995) due to the decrease of paddy fields, thus its effect on the groundwater quality has also been concerned. Furthermore, some paddy fields have been turned to upland fields, which may influence the NO 3 -N contamination of groundwater. In any cases, more elaborate study should be conducted as soon as possible to ascertain the source and mechanism of NO 3 -N contamination of the groundwater in these areas. Situation at middle (Group 5 area) and western parts (Group 6 and Group 7 areas) In the Group 5 area, NO 3 -N was detected at only one sampling point of no. 19 located near Group 2 area. Other two sampling points are located at right in the middle of the city where the impermeable bed is lacking and also are nearby the alluvial area. On the other hand, the NO 3 -N concentration in shallow well was relatively high at no. 19 point, and the downward tendency of NO 3 -N concentration in shallow well of no. 19 to no. 21 points was observed as shown in Fig. 5. In addition, the dissolved oxygen (DO) concentration in the groundwater at no. 22 point was 0.6 mg/l (July, 2006) which was obviously lower than that in other areas (7.0~8.4 mg/l), suggesting it is reductive atmosphere in the subsurface environment of Group 5 and Group 6 areas. From these results, the following hypothesis was proposed: the groundwater in the first aquifer of this area is contaminated in upstream areas such as Group 1 and 2 areas, and additionally with direct inflow from a ground surface right above this area, however, the NO 3 -N is removed by biological denitrification under anaerobic condition (reductive atmosphere) during the water permeate through the soil. This hypothesis will be supported by the situation of NO 3 -N pollution in the Group 6 area. The NO 3 -N was detected in low concentration level at only nos. 24 and 28 points, but not detected at other points even in shallow wells. The contribution of biological denitrification activity to nitrate removal in the soil environment was well-known so far (Tayfur et al, 2008; Shomar et al, 2008). The muddy sediment in the alluvial area includes reduced sulfur and organic compounds as an electron donor for NO 3 -N reduction, suggesting that this area has enough capability of NO 3 -N removal. In addition, low-permeable property of muddy soil might contribute to prolongation of retention time of groundwater, which results in promoting a biochemical reaction. However, since the NO 3 -N concentration at nos. 22 and 24 points showed upward tendency for recent 20 years as shown in Fig. 6, the future trend will have to be careful even in this area. In the Group 7 area, the NO 3 -N was detected at all points. However, their concentrations were low and showed flat in recent 10 years as shown in Fig. 6, thus it is not considered to be in severe situation at this time. Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 27 - CONCLUSIONS Current situation of NO 3 -N contamination of groundwater in Kumamoto city was investigated and the following insights were obtained. 1) Nitrate nitrogen was detected in the groundwater at 22/30 points in various area of Kumamoto city. 2) The NO 3 -N concentration was in the range from 0.2 to 5.8 mg/l, which was presumed to be related with area-location and groundwater flow. 3) Upward tendency in NO 3 -N concentration was recognized in the groundwater at most of wells that NO 3 -N was detected. Finally, The NO 3 -N concentration level in the Kumamoto city groundwater is considered to be not critical situation, however, it still shows continued increase and there is no denying that it will exceed the drinking water quality standard in near future. The earliest possible every effort to determine the primary pollutant source and to reduce the pollution should be conducted before it is too late. ACKNOWLEDGEMENTS The authors thank Mr. Katsunobu Onitsuka and Mr. Shinichi Kanehira of Kumamoto City Water Preservation Section for kindness and support to carry out this study. REFERENCES Annual Report on Public Water quality (2006). Kumamoto City Water Works Bureau, Kumamoto, Japan. European Standards for Drinking Water. 2nd edition (1970). World Health Organization (WHO), Geneva, Swiss. Hashimoto S. (1989). Evaluation of water quality of healthy and/ or tasty drinking water and its application to Japanese waters. J. Society Heating, Air-Conditioning Sanit. Eng. Japan, 63, 463-468. Hu K., Huang Y., Li H., Li B, Chen D. and White R. E. (2005). Spatial variability of shallow groundwater level, electrical conductivity and nitrate concentration, and risk assessment of nitrate contamination in North China Plain. Environ. Int., 31, 896-903. Ichikawa T., Naitoh T. and Hoshida Y. (1995). Observation and Water Balance of Flow Rate in Springs of an Urban Area. Bull.School Eng., Kyushu Tokai Univ., 21, 143-151. Japan Water Works Association method (2001). Japan Water Works Association, Tokyo, Japan. Kawagoshi Y., Iwasa Y., Yunoue T., Maeda K., Tomiie K. and Kakimoto R. (submitted). Water quality characterization and evaluation as a tasty-water for Kumamoto-city drinking groundwater. J.Japan Soc. Water. Environment. Kumamoto prefectural institute of public-health and environmental science (2000). The investigation report on the mechanism of groundwater contamination by nitrate, Kumamoto, Japan. Kumamoto prefecture and Kumamoto city (2005). The investigation report on the groundwater protection and management in Kumamoto area, Kumamoto, Japan. Journal of Water and Environment Technology, Vol. 7, No. 1, 2009 - 28 - Kumazawa K. (2002). Nitrogen fertilization and nitrate pollution in groundwater in Japan: Present status and measure for sustainable agriculture. Nut. Cycl. Agroecosys., 63, 129-137. Nagai S., Ishii T. and Kuroda K. (1983). Hydrochemical investigation of ground water in the Kumamoto plain. Ind. Water, 296, 27-43. Nas B. and Berktay A. (2006). Groundwater contamination by nitrates in the city of Konya, (Turkey): a GIS perspective. J. Environ. Manage., 79, 30-37. Shomar B., Osenbruck K. and Yahya A. (2008). Elevated nitrate levels in the groundwater of the Gaza Strip: distribution and sources. Sci. Total. Environ., 398, 164-174. Showers W. J., Genna B., McDade T., Bolich R. and Fountain J. C. (2008). Nitrate contamination in groundwater on an urbanized dairy farm. Environ. Sci. Technol., 42, 4683-4688. Tayfur G., Kirer T. and Baba A. (2008). Groundwater quality and hydrogeochemical properties of Torbali Region, Izmir, Turkey. Environ. Monit. Assess., 146, 157-169. Tsuru N., Mori M. and Baba M. (1998). Groundwater quality in Kumamoto city (1) ~geographic characteristics based on the mineral components in the groundwater~. Ann. Report Kumamoto City Environ. Res. Inst., 6, 34-43. Tsuru N., Sueyoshi E., Akahoshi H., Iwanaga T., Iwao A., Shinya T., Murakami M., Mori M., Baba M., Nakaguma H. and Tajima K. (2005). The interannual variation of the groundwater quality in Kumamoto city. Ann. Report Kumamoto City Environ. Res. Inst., 13, 52-63. Tsuru N., Akahoshi H. and Miyamoto H. (2006). Groundwater pollution by nitrate-nitrogen in Kumamoto city. Ann. Report Kumamoto City Environ. Res. Inst., 14, 59-67. . 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 1 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29. 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 1 2 4 5 3 6 7 8 9 10 11 12 13 14 20 21 17 16 18 23 24 25 26 27 19 28 22 29 30 15 Group 7 Group 1 Group