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Patterns of contaminated zones of water in the ground
Author(s) -
Legrand H. E.
Publication year - 1965
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr001i001p00083
Subject(s) - groundwater , contamination , environmental science , dilution , water table , vadose zone , saturation (graph theory) , water well , geology , hydrology (agriculture) , soil science , geotechnical engineering , ecology , physics , mathematics , combinatorics , biology , thermodynamics
Movement of contaminants from many waste sites into the subsurface water circulation system results in contaminated zones, or enclaves, in the zone of saturation (below the water table). Difficulty in predicting the areal extent of a contaminated zone stems from the multiplicity of factors that need consideration, including: the great variety of waste materials, their range in toxicity and adverse effects; man's variable pattern of waste disposal and of accidental release of contaminants in the ground; man's variable pattern of water development from wells; behavior of each contaminant in the soil, water, and rock environment; ranges in geologic and hydrologie conditions in space; and ranges in hydrologie conditions in time. Two opposing tendencies need to be in focus before an evaluation of contaminated zones is undertaken: (1) the tendency of contaminants to be entrained in groundwater flow and (2) the tendency for contaminants to be attenuated to varying degrees by dilution in water, decay with time, or some other ‘die‐away’ mechanism, and sorption on earth materials. Once a contaminated zone is approximately stable, an increase in concentration may cause it to remain about the same size under some conditions and to enlarge in others, according to combined attenuation effects. Where attenuation occurs only by dilution, the contaminated zone will become enlarged with increased concentration, and, where dilution is also slight, it may become greatly elongated in the direction of groundwater, and perhaps also of surface‐water, flow. Where attenuation occurs also through decay or sorption, or through both mechanisms, the contaminated zone may not enlarge appreciably, even if the concentration of contamination is increased. The upper part of the zone of saturation in populated parts of the Earth may be considered as a galaxy in which millions of enclaves of contaminated water are scattered in uncontaminated groundwater. Interspersed with these enclaves are millions of water‐supply wells, some of which pump contaminated water or help to disperse it even if it does not reach them. Although too few contaminated zones have been delineated to enable a statistical analysis of areal patterns, an approximation of their patterns of distribution can be deduced.