(2) In case arsenic is present in the ores, as it often is and notably at Anaconda, it is given off in the fumes from the smelter in volatile form and deposited on the surrounding land and crops, where it may be present in sufficient amounts to poison cattle browsing on exposed ranges, or living on hay cut from such pasture.

(3) The tailings from the water concentration of the ore and the slag, in a finely divided condition, are discharged on a dump heap through which the water from the plant is constantly percolating on its course to adjacent streams and the "slimes" are left in piles in the open air. Both the slime heap and the dump are also exposed to the percolating action of the rain. In consequence, the streams receiving the waste water from concentrating and smelting plants contain a comparatively large amount of copper in suspension and are apt to hold some copper in solution. If these streams are used for irrigating purposes there is a possible source of injury to growing crops due to the action of the copper present.

a

(4) Finely divided particles of the ore are discharged from the smelter stack and settle on the surrounding country. These fine particles of flue dust may contain sufficient amounts of copper, lead, and zinc to injure vegetation, because of their toxic action through the medium of the soil and because of their caustic action on the foliage. While it is believed by some that the action of this so-called flue dust gives rise to the principal damage caused by smelter smoke, the writer is inclined to the opinion that such injury is not of great significance except in a very limited area about the smelter, and that an investigation of it is in most cases unnecessary, as the owners of smelters are usually perfectly willing to admit damage, even beyond the area likely to be affected by the solid particles of copper, lead, and zinc in the flue dust.

In the first case of this kind studied by the writer in the vicinity of Redding, Cal. (see Pl. I), and in the laboratory at Washington during 1903 and 1904, no complaint had been made of the injury from arsenic or from copper, so that the only problem considered was the action of sulphur dioxid and trioxid fumes on the surrounding vegetation. The results of this study and the original investigations connected therewith have been published, but a résumé will be given, together with certain results obtained since the publication of the Redding investigations, in order that the reader may understand the present status of the work.

Ebaugh, J. Amer. Chem. Soc., 1907, 29: 951.

Haywood, Science, 1907, 26: 476.

C

U. S. Dept. Agr., Bureau of Chemistry, Bul. 89, Injury to Vegetation by Smelter Fumes, 1905.

EXPERIMENTAL INVESTIGATIONS RELATING TO THE ACTION OF SULPHUR DIOXID ON VEGETATION.

ORGANS OF THE PLANT THROUGH WHICH INJURY TAKES PLACE.

In carrying on an investigation of this kind it was first necessary to ascertain whether or not sulphur dioxid was injurious to plant life, how small a quantity was injurious, and through what organs of the plant such injury took place. Light is thrown on this subject by the work of foreign chemists.

Freytag showed that sulphur dioxid and trioxid do not injure the plant through the roots. His experiment consisted in watering wheat, oats, and peas with large amounts of dilute sulphurous acid in one case and sulphuric acid in another. The plants neither wilted nor reduced their yield. Von Schroeder and Schmitz-Dumont made an investigation on pines, firs, lindens, and Norway maples in 1896, in which they treated (1) the aerial parts of the plants with sulphur dioxid, (2) the aerial parts of the plant and the earth with sulphur dioxid, and (3) the earth in which the plant was growing with dilute sulphurous acid. They also showed that the injury to vegetation by sulphur dioxid is not through the roots, but through the medium of the leaves, and that even extremely minute quantities of sulphur dioxid are injurious.

Wieler in his work entitled "Untersuchungen über die Einwirkung schwefliger Säure auf die Pflanzen," which has been published since the work at Redding was done, also gives numerous experiments to show that minute amounts of sulphur dioxid injure plants through the leaves, but he also states that in the course of time the sulphur dioxid and trioxid present in smelter smoke injuriously affect the soil and so indirectly injure the plant through the roots. He is further of the opinion that soils subjected to the action of sulphur dioxid suffer from a reduction in the lower forms of animal and plant life which are so necessary to the series of natural changes taking place in normal soils. He is also of the opinion that such soils suffer a loss in bases, which eventually causes them to become acid, as not enough bases are present to form humates with the humic acid. In proof of the latter point, he has taken soil samples from the vicinity of several smelters and found that all of them contained free humic acid.

Wieler's conception of this additional injurious action of sulphur dioxid on the soil has been published so recently that the writer has not been able to investigate the subject sufficiently to express a defi

a Mitt. d. königl. landw. Akad.. Poppelsdorf, 1869.

Thar. forsti. Jahrb., 1896, 46: 1.

KESWICK SMELTER, NEAR REDDING, CAL., IN OPERATION.

nite opinion in regard to its merits. It would appear, however, from the work done that Wieler lays too much stress on the sulphur dioxid injury to the soil, as compared with the injury caused by the sulphur dioxid acting on the foliage. In support of this opinion several soils from the vicinity of a smelter were tested by the author. These soils were taken from forest land where certain trees were practically annihilated by smelter fumes, as proved by chemical analysis, and yet all of the soils gave an alkaline reaction, showing that there had evidently not been such a loss of bases as to give rise to free humic acid.

On the whole, then, the work done undoubtedly points to the fact that sulphur dioxid injures vegetation through the leaves, but whether it injures the soil, and so indirectly injures the plant through the roots, is a problem which must be studied further before a definite. conclusion can be reached.

AMOUNT OF SULPHUR DIOXID THAT MAY CAUSE INJURY.

In regard to the amounts of sulphur dioxid in the atmosphere that may injure vegetation, Stöckhardt" showed that 1 part of sulphur dioxid to 1,000,000 parts of air injured potted pines seriously after 365 fumigations. Freyag cast doubt on Stöckhardt's data by his investigations, and Stöckhardt's work was repeated by Von Schroeder and Schmitz-Dumont," who showed that great injury was inflicted by fumigating pines 109 times with 1 part of sulphur dioxid to 100,000 parts of air and that injury was to be noted on fumigating pines 583 times with 1 part of sulphur dioxid to 1.000.000 parts of air.

The details of the work done by the writer in relation to injury to pines and young cowpeas by sulphur dioxid show the following results:

(1) Pine trees fumigated 6 times with 1 part of sulphur dioxid to 100 parts of air showed marked injury. All of the needles were drooping, and nearly all had turned yellow or brown.

(2) Pine trees fumigated 9 times with 1 part of sulphur dioxid to 1,000 parts of air were greatly injured in the same manner as the plants just described.

(3) Pine trees fumigated 50 times with 1 part of sulphur dioxid to 10,000 parts of air were badly injured.

(4) Cowpeas fumigated 18 times with 1 part of sulphur dioxid to 10,000 parts of air lost all their leaves and could not be revived, although carefully watered and tended outside the fumigation chamber.

a Haselhoff and Lindau, Die Beschädigung der Vegetation durch Rauch, pp. 58-66.

U. S. Dept. Agr., Bureau of Chemistry, Bul. 89.
Each fumigation lasted for one hour.

40505-Bull, 113-08