The State of Arsenic in Nepal - 2003 - Harvard University ...

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Mahendrakot VDC of Kapilbastu and the sixth one (571 ppb) was observed in Sarwal VDC of Nawalparasi. The arsenic concentration at each of 20 districts of the Terai is shown in Figure 7.5. Table 7.3. Basic statistics of arsenic concentration Figure 7.4. Distribution of mean and median arsenic concentrations The maximum concentration 2,620 ppb of arsenic was measured in Rupandehi district. The next three high concentrations were also observed in the same district. These four very high arsenic contaminated tube wells are located in one place called Madangram tole. This place is in Devedaha VDC of Rupandehi district. These arsenic values were recorded at the same year of installation of these tube wells. There were about 30 samples analysed for arsenic in this place, of which 20 samples were exceeding Nepal Interim Standard and 5 samples were below WHO Guideline. The four very high arsenic values concentrated in this place look like outliers in the distribution of arsenic (Figure 7.5). The fifth high value (589 ppb) of arsenic was noticed in Mean Std. Error of Mean Minimum Maximum Std. Deviation Median Total District % Kanchanpur 8.9 1.9 0 221 25.3 1 177 0.9 Kailali 16.7 1.8 0 213 31.1 3 301 1.6 Bardiya 8.7 0.7 0 160 17.0 2 651 3.5 Banke 5.1 0.5 0 270 15.1 1 843 4.5 Dang 2 0.4 0 50 5.5 0 196 1.1 Kapilbastu 8 0.6 0 589 31.1 0 2490 13.4 Rupandehi 10.4 2.3 0 2620 102.5 0 2043 11.0 Nawalparasi 58.7 1.8 0 571 102.6 10 3211 17.2 Chitwan 0.5 0.1 0 8 1.5 0 203 1.1 Parsa 7.2 0.5 0 456 23.3 3 2247 12.1 Bara 5.9 0.4 0 254 15.6 1 1954 10.5 Rautahat 21.4 0.6 0 324 26.1 14 2053 11.0 Sarlahi 9 0.9 0 98 16.4 3 326 1.7 Mahottari 2.1 0.6 0 80 7.8 0 199 1.1 Dhanusha 7.8 0.9 0 106 14.6 5 285 1.5 Siraha 9.3 1.0 0 107 15.4 5 234 1.3 Saptari 6.1 0.4 0 98 10.6 5 570 3.1 Sunsari 3.3 0.5 0 50 6.1 0 172 0.9 Morang 2.7 0.5 0 70 7.7 0 200 1.1 Jhapa 5.3 0.5 0 79 7.8 5 280 1.5 Total 17.8 0.4 0 2620 60.7 2 18635 100.0 (a) Figure 7.5. Distribution of arsenic concentration by district (a) 0 ppb to 2620 ppb, (b) 0 ppb to 600 ppb (b) 19
7.2. Relation of arsenic concentration with depth of tube well Concerning the depth of contaminated tube wells, about 93.4% of arsenic tested tube wells also report well depth. The depth of these tube wells varies from 1 to 174 meters (m) with average depth of 22.4 m. Only 0.1% of these tube wells are deeper than 100 m and 5.5% have depth between 51 and 100 m (Table 7.4). The majority of the arsenic tested tube wells (94.4%) are less than 50 m deep. The scatter diagram of arsenic concentration and depth of tube well shows that most of tube wells with high value of arsenic have depths of less than 50 m, and the majority of tube wells deeper than 50 m have arsenic values below 50 ppb (Figure 7.6). The four tube wells with very high arsenic values were respectively 24, 48, 33 and 35 meters deep. Regarding the relationship between arsenic and depth of tube well, there is significantly very low negative correlation (-0.05) between arsenic concentration and depth of tube wells based on 17,401 samples, which indicates that deeper tube wells have less arsenic concentration. However, there were only 10 tube wells greater than 100 m depth, and 966 tube wells were greater than 50m deep in this study. So, the arsenic concentrations were further classified into small groups of depths up to 50 m in order to examine the relationship between depth and arsenic. Table 7.4. Classification of arsenic concentration by depth % of Arsenic concentration Depth TW in group 0 - 10 ppb 11 - 50 ppb Above 50 Total each (m) depth No. % No. % No. % group 1-10 2347 87.2 250 9.3 93 3.5 2690 15.5 11-20 5165 69.4 1489 20.0 787 10.6 7441 42.8 21-30 2148 65.4 790 24.1 346 10.5 3284 18.9 31-40 1472 83.2 218 12.3 79 4.5 1769 10.2 41-50 1130 90.3 100 8.0 21 1.7 1251 7.2 >50 922 95.4 35 3.6 9 0.9 966 5.6 Total 13184 2882 1335 17401 100.0 On comparison of the percentages of arsenic tested tube wells that exceed both the WHO Guideline and Nepal Interim Standard with well depth, the highest percent of contaminated wells is in the depth group of 11-30 m followed by 31-40 m, 1-10 m, and 41-50 m. Among this depth group of 11- 30 m, 11% of arsenic tested tube wells were above Nepal Interim Standard, 32% of tube wells were above WHO Guideline and 68% of the wells tested were below WHO Guideline (Table 7.4 & Figure 7.7). Figure 7.6. Scatter diagram of depth of tube wells and arsenic concentration ranging from (a) 0 ppb to 2620 ppb (b) 0 ppb to 600 ppb (c) 0 ppb to 600 ppb for below 50 meter deep tube wells (a) (b) (c) 20
Page 2 and 3: National Arsenic Steering Committee
Page 4 and 5: Project Team Project Co-ordinator R
Page 6 and 7: Contents Acknowledgement Contents L
Page 8 and 9: Abbreviations AAN AAS AIRP As As 2
Page 10 and 11: tube wells contain 0-10 ppb of arse
Page 12 and 13: 1. Introduction Providing safe drin
Page 14 and 15: 3 . Arsenic in groundwater in East
Page 16 and 17: groundwater extraction is about 685
Page 18 and 19: 5.3. Arsenic mitigation measures un
Page 20 and 21: Bangladesh and solves the problem o
Page 22 and 23: 6. Data and map preparation The qua
Page 24 and 25: Table 6.3 presents arsenic tested t
Page 26 and 27: 6.2.2. Preparation of digital spati
Page 28 and 29: 7. Analysis of arsenic concentratio
Page 32 and 33: with tube well age, there is signif
Page 34 and 35: (a) (b) Figure 7.11. Distribution o
Page 36 and 37: 81°30'0"E 81°35'0"E 81°40'0"E 81
Page 38 and 39: 80°55'0"E 81°0'0"E 81°5'0"E 81°
Page 40 and 41: 82°0'0"E 82°5'0"E 82°10'0"E 82°
Page 42 and 43: 87°35'0"E 87°40'0"E 87°45'0"E 87
Page 44 and 45: 79°55'0"E 80°0'0"E 80°5'0"E 80°
Page 46 and 47: 27°10'0"N 27°5'0"N 27°0'0"N 26°
Page 48 and 49: 83°35'0"E 6 68 67 83°40'0"E 69 25
Page 50 and 51: 85°0'0"E 85°5'0"E 85°10'0"E 85°
Page 52 and 53: 86°30'0"E 86°35'0"E 86°40'0"E 86
Page 54 and 55: 86°10'0"E 28 38 47 95 56 62 11 94
Page 56 and 57: The distribution of percentage of a
Page 58 and 59: Low uncertainty: VDCs where proport
Page 60 and 61: 81°30'0"E 81°35'0"E 81°40'0"E 81
Page 62 and 63: 81°0'0"E 81°5'0"E 81°10'0"E 81°
Page 64 and 65: 82°0'0"E 82°5'0"E 82°10'0"E 82°
Page 66 and 67: 87°40'0"E 87°45'0"E 87°50'0"E 87
Page 68 and 69: 80°0'0"E 80°5'0"E 80°10'0"E 80°
Page 70 and 71: ! 26°35'0"N 26°40'0"N 26°45'0"N
Page 72 and 73: 83°35'0"E 83°40'0"E 83°45'0"E 83
Page 74 and 75: 85°0'0"E 85°5'0"E 85°10'0"E 85°
Page 76 and 77: 86°30'0"E 86°35'0"E 86°40'0"E 86
Page 78 and 79: ! ! 86°10'0"E ! ! ! ! ! ! ! ! ! !
Page 80 and 81:
81°30'0"E 81°35'0"E 81°40'0"E 81
Page 82 and 83:
80°55'0"E 81°0'0"E 80°55'0"E 81
Page 84 and 85:
80°20'0"E 80°25'0"E 80°30'0"E 80
Page 86 and 87:
82°45'0"E 82°50'0"E 82°55'0"E 83
Page 88 and 89:
83°35'0"E 83°40'0"E 83°45'0"E 83
Page 90 and 91:
85°0'0"E 85°5'0"E 85°10'0"E # "#
Page 92 and 93:
86°30'0"E 86°35'0"E 86°40'0"E 86
Page 94 and 95:
83°38'0"E 83°40'0"E 83°42'0"E Ar
Page 96 and 97:
83°38'0"E 83°39'0"E 83°40'0"E Ar
Page 98 and 99:
83°36'0"E 83°38'0"E 83°40'0"E 27
Page 100 and 101:
83°45'0"E 83°46'0"E Arsenic Conce
Page 102 and 103:
83°30'0"E 83°32'0"E 83°34'0"E 83
Page 104 and 105:
8. Distribution of arsenic in the T
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81°0'0"E Kanchanpur Kailali Bardiy
Page 108 and 109:
81°0'0"E 82°0'0"E 83°0'0"E 84°0
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9. Recommendations to improve the N
Page 112 and 113:
with anomalous arsenic concentratio
Page 114 and 115:
Annex 2 Basic Statistics of arsenic
Page 116 and 117:
(a) (b) (c) (d) (e ) (f) (g) (h) (i
Page 118 and 119:
(a) (b) (c) (d) (e) (f) (g) (h) (i)
Page 120 and 121:
(a) (b) (c) (d) (e) (f) (g) (h) (i)
Page 122 and 123:
References BGS and DPHE (2001). Ars
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