OIL AND TAR POLLUTION OF WATERS. 7 



as from lack of oxygen, or from the destruction or spoiling of emergent 

 or littoral vegetation with an oil coating, particularly in tidal areas 

 (by which means wild fowls may also greatly suffer) , and tiie conse- 

 quent loss of a productive habitat. 



From gas houses, tarred roads, and refineries much of the contam- 

 ination eventually finds its way to the bottom to render it more or 

 less sterile according to thickness and completeness of the deposit 

 and the constancy with which the deposit is maintained. Wadham 

 indicates that he found apparently complete strata for each fresh 

 tarring of road, and that it took two or more years for a trout brook 

 to recover proper productivity of fish. 



In some waters the basic fish food consists in part of air-breathing 

 larvae and pupae of insects, wliich, if a layer of oil is present, as is well 

 known, will be unable to come to the surface to breathe and so will 

 be destroyed. Young of food fishes or the small fish on which food 

 fishes feed will in consequence be deprived of an important source 

 of food, and the productivity of the region will be correspondingly 

 decreased. In 1920, through the Gulf States, Mr. Hildobrand found 

 that Gambusia and Fundulus, which feed largely on such larvae and 

 pupje, disappeared from oil-covered water. He took no special notes 

 m regard to larger species, but believed they disappeared also, pre- 

 sumably because their food had disappeared. 



SUMMARY. 



Three main sources of oil and tar pollution have been found: Road 

 washings, carrying great cjuantities of lubricating oil; gas houses and 

 oil refineries; tankers, oil burners, and oil-cngined shipping. Tars, 

 tar oils, and crude distillery products are found generally to be highly 

 poisonous, whether in weak or great dilution. Some oils have been 

 found to emulsify to a suilicient degree, with continued agitation, 

 to coat the gills of fish and so produce death by suff(;cation. An oil 

 iilm, through prevention or checking of aeration, is dangerous, par- 

 ticularly^ in busy harbors. The deleterious eflect on spawning, by 

 rendering spawning grounds unfit or inaccessible, is a grave danger 

 arising from the pollution of harbors and streams. Another serious 

 danger is found to lie in the possible effects on the diminution of the 

 food supply. Thi'ough whatever means, it is an observed fact, 

 according to Weigelt, that in Germany fish have completely disap- 

 peared from pools and ponds following the discharge of mineral oil 

 into the water. In the sea a great danger is suggested by the fact 

 that the eggs of sea fishes are typically fioating, and that oil-burning 

 and oil-engined shipping is greatly increasing. 



Remedial measures may (now or in the future) be found: (1) In 

 the recovery of oils from drainage water, as already has been pro- 

 posed; (2) in the prevention of ga.s-hoiise and refinery pollution, 

 which prevention should be helped by the increased use of "wastes" 

 in by-products; and (8) in prevention, by international arrange- 

 ments, of the dumping of oil from ships in harbors or in the region of 

 spawning grounds or special feicding areas. 



