PERMAFROST — BLACK 291 



Throughout the Arctic, however, the quality of water is commonly 

 poorer than in temperate regions. Hardness, principally in the form 

 of calcium and magnesium carbonate and iron or manganese, is com- 

 mon. Organic impurities and sulfur are abundant. In many places 

 ground water and surface water have been polluted by man or or- 

 ganisms. 



Muller (1945) presents a detailed discussion of sources of water and 

 the engineering problems in permafrost areas of distributing the 

 water. Joestings (1941) describes a partially successful method of 

 locating water-bearing formations in permafrost with resistivity 

 methods. 



Sewage disposal. — Sewage disposal for large camps in areas of con- 

 tinuous permafrost is a most difficult problem. Wastes should be 

 dumped into the sea, as no safe place exists on the land for their dis- 

 posal in a raw state. As chemical reaction is retarded by cold temper- 

 atures, natural decomposition and purification through aeration do 

 not take place readily. Large streams that have some water in them 

 the year around are few and should not be contaminated. Promiscu- 

 ous dumping of sewage will lead within a few years to serious pollu- 

 tion of the few deep lakes and other areas of annual surface-water 

 supply. Burning is costly. As yet no really satisfactory solution is 

 known to the writer. In discontinuous and sporadic permafrost zones, 

 streams are larger and can handle sewage more easily, yet even there 

 sewage disposal still remains in places one of the most important 

 problems. 



Agriculture. — Permafrost as a cold reserve has a deleterious effect 

 on the growth of plants. However, as an impervious horizon it tends 

 to keep precipitation in the upper soil horizons, and in thawing pro- 

 vides water from melting ground ice. Both deleterious and beneficial 

 effects are negligible after 1 or 2 years of cultivation, as the perma- 

 frost table thaws, in that length of time, beyond the reach of roots of 

 most annual plants (Gasser, 1948). 



Farming in permafrost areas that have much ground ice, however, 

 can lead to a considerable loss in time and money. Sub-Arctic farming 

 can be done only where a sufficient growing season is available for 

 plants to mature in the short summers. Such areas are in the discon- 

 tinuous or sporadic zones of permafrost. If the land is cleared of its 

 natural insulating cover of vegetation, the permafrost thaws. Over 

 a period of 2 to 3 years, large cave-in lakes have developed in Siberia 

 (I. V. Poii-e, oral comnuuiication), and pits and mounds have formed 

 in Alaska (pi. 10, fig. 4) (Pewe, 1948a, 1949; liockie, 1942). The 

 best solution is to select farm lands in those areas free of permafrost 

 or free of large ground-ice masses (Tziplenkin, 1944). 



Mining. — In Alaska, placer miners particularly, and lode miners 

 to a lesser extent, have utilized permafrost or destroyed it as neces- 



