Rolling Revision of the WHO Guidelines for Drinking-Water Quality ...

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Figure 5.2 Classification of types of fine soil according to the US-Taxonomy (Russell 1973; Scheffer and Schachtschabel, 1992) Figure 5.2 shows the classification of types of fine soil according to the USA soil taxonomy. Figure 5.3 illustrates the characteristic soil water curve, which is the relationship between the intensity of water binding, the water gauge and water content for three different types of soil. Figure 5.3 Characteristic soil water curve for three different types of soil (Rohmann and Sontheimer, 1985) The field capacity (FK) is the quantity of water which a soil may retain for a few days against gravity, after saturation with water. The usable field capacity (nFK) is the soil water quantity which can be taken up by plants. The remaining water, the ‘dead water fraction’ is adsorptively bound to the rock matrix and neither available to plants nor able to percolate. The permanent wilting point forms the limit between usable field capacity and the dead water fraction. In addition to the pore size distribution, the soil density and the content of organic substance affect the water storage capacity of the soil. Theoretically, in the plant soil zone (the effective root zone, FKRZ) plants are able to use all soil water in the usable field capacity. The maximum quantity of water available to plants (nFKRZ) (mm or l –1 m 2 ) depends upon the quantity of water in the field capacity and the depth of the effective root zone. The annual exchange frequency of soil water gives some indication of the risk of nitrate leaching from the root zone (German Pedological Society, 1992., Frede and Dabbert, 1997). Table 3.7 illustrates the soil water exchange frequencies for soils with different field capacities in the root zone. If the frequency of exchange is greater or equal to 100% the nitrate present in the soil zone before percolation of water is considered to have been displaced from the effective root zone:
EF = (PW/FKRZ) * 100 Where EF = exchange frequency of soil water (% a -1 ) PW = amount of percolating water FKRZ = field capacity in the effective root zone (mm) Table 5.2 Frequency of soil water exchange in the effective root zone (Frede and Dabbert, 1997) Frequency of soil water exchange in the effective root zone average quantity of percolating water (mm/a) FKRZ 50 100 150 200 300 400 (mm) frequency of exchange EF (%/a) 50 100 200 300 400 600 800 100 50 100 150 200 300 400 150 33 67 100 133 200 267 200 25 50 75 100 150 200 250 20 40 60 80 120 160 300 17 33 50 67 100 133 400 13 25 38 50 75 100 500 10 20 30 40 60 80 wash-out factor WF at wash-out frequencies < 100 % WF = EF/100 at wash-out frequencies > 100 % WF = 1 Nitrate pollution of percolating water is influenced by the N-balancemin. surplus and the annual nitrogen net mineralisation rate M (Nmin is the quantity of mobile nitrate-N and exchangeable ammonium-N that is available to plants). The medium Nbalancemin. is derived from the actual nitrogen surplus (e.g. the average over a crop sequence). The annual nitrogen net mineralisation includes the nitrogen returned through mineralisation in organic manure, residues remaining in the soil from past crops and further nitrogen supply from the soil. Therefore to minimise a nitrogen surplus, farmers should take into account past farming practices and nitrogen fertiliser application. The potential hazard to water can be represented by the long-term average nitrate concentration in percolating water under optimised nitrate fertilisation. This can be calculated as follows: NO3 - PW = ((N-balancemin. + M - I - D) * WF / PW) * 4.43 *100 = ((N-balancemin. + M - I - D) / FKRZ) * 4.43 *100 for EF < 1 = ((N-balancemin. + M - I - D) / PW) * 4.43 *100 for EF > 1 Where NO3 - PW = potential nitrate concentration in percolating water (mg/l) N-balancemin. = mineral N share in the N-balance: N area balance (kg N/ha*a) (average over a few years, respectively the mean over a crop rotation), reduced by N from organic manuring (farm manure, wastes) not available in the respective year of application and N content in crop residues M = N net mineralisation (kg N/ha*a) (N return supply from application of organic manure and from crop residues in the past and subsequent N supply from soil)
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WHO/SDE/WSH/04.08/56 Rolling Revisi
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List of contents Chapter 1 Origin o
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7.3 Soil and organic matter 7.4 Sit
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Table 1.1 Trend in nitrate concentr
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NH4 + + 1.5 O2 --> NO2 - + H2O + 2
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In developed countries, urban groun
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Saharan Africa correlate with popul
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through microbial denitrification a
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Figure 1.7 From overproduction to r
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total emissions is between 0.2 and
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1999 Marker species for identifying
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NEERI 1991 Water Mission Report on
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Chapter 2 Human Exposure and Risk a
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of nitrogen fertiliser or manure. O
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nitrate and nitrite concentrations
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methaemoglobinaemia observed in inf
Page 33 and 34: 2.3.4 Reproductive and development
Page 35 and 36: Accidental human intoxications have
Page 37 and 38: of nitrates, nitrites and N-nitroso
Page 39 and 40: McKnight et al. (1999) suggest that
Page 41 and 42: nitrate in the etiology of the hype
Page 43 and 44: Gonzalez, C.A., Sanz, J.M., Marcos,
Page 45 and 46: Lagerstedt, E., Jacks, G. and Sefe,
Page 47 and 48: thyroids of rats.] Schrifte für Ge
Page 49 and 50: Northern China. Agriculture, Ecosys
Page 51 and 52: top soil ⎫ ⎫ ⎫ ⎪ ⎪ ⎪
Page 53 and 54: nitrate is not of significance. Den
Page 55 and 56: Figure. 3.4: Nitrate concentration
Page 57 and 58: observed in various parts of the wo
Page 59 and 60: groundwater recharge as a result of
Page 61 and 62: oxygen, are quickly displaced to gr
Page 63 and 64: Chapter 4 Treatment and disposal of
Page 65 and 66: 4. Formulation and implementation o
Page 67 and 68: the sludge. Table 4.3 Permissible a
Page 69 and 70: sewage quality, higher requirements
Page 71 and 72: In all types of organic fertilisers
Page 73 and 74: • Use of maintenance-free enginee
Page 75 and 76: (Chan and Guterstam, 1996). Constru
Page 77 and 78: Staatsministeriums für Landesentwi
Page 79 and 80: und Grundwasserbeschaffenheit bei n
Page 81 and 82: Figure 5.1 Calculation of the nitro
Page 83: in an accumulation of organic nitro
Page 87 and 88: groundwater zone, due to capillary
Page 89 and 90: This information may help to optimi
Page 91 and 92: Figure 5.7 Potential rate of minera
Page 93 and 94: Figure 5.8 Cumulative NH3 emissions
Page 95 and 96: 5.3.5 Grassland farming Compared wi
Page 97 and 98: In order to calculate the optimum a
Page 99 and 100: 5.5 References Arbeitsgemeinschaft
Page 101 and 102: 21. Belastungen der Oberflächengew
Page 103 and 104: Rejesus, R.M. and Hornbaker, R.H. 1
Page 105 and 106: Chapter 6 Water treatment processes
Page 107 and 108: Nitrate-selective resins also add l
Page 109 and 110: 6.2.2 Heterotrophic denitrification
Page 111 and 112: small reactor volumes and areas. Th
Page 113 and 114: 2. NO - 2 + 2AL + 3H2O → NH3 + 2A
Page 115 and 116: denitrification in cooler climates
Page 117 and 118: Chapter 7 Problem evaluation and ma
Page 119 and 120: inputs from point sources, land run
Page 121 and 122: most commonly used methods for anal
Page 123 and 124: sulphuric acid to 1 litre of sample
Page 125 and 126: The nitrite produced is determined
Page 127 and 128: concentrations of NO - 3-N, dilutio
Page 129 and 130: Figure 7.4 Actions required in the
Page 131 and 132: 7.5 References Ballance, R. 1996a P
Page 133: ions. Part 1: Method for water with
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