Chloride and Sulfate in Rain Water W. D. COLLINS~ R ’ DK. T. WILLIAMS.United S t a t e s Geological Survey, Washington, D. C.
T
H E Mississippi River drains over one-third of the area of the United States and thus carries a notable proportion of the rain (including melted snow) that falls in the United States and reaches the ocean, either as fairly direct run-off or after passing underground and reaching the surface again from wells or springs. Data are not available to show the chemical character of this water as it first reaches the earth. Most of the published material is likely to be misleading, even though the authors may have pointed out the fact that their samples were not representative of general conditions. A review of published analyses of rain water summarized by Riffenburg (6) in 1925 indicated an average of about 3.0 parts per million of chloride and 5.0 parts of sulfate (SOn) in the analyses reported in over two hundred journal articles. A continuation of this survey of the literature does not give any grounds for revising these estimated averages of the reported results. A recent publication ( 7 ) gave from 3.6 to 17.2 p. p. m. of chloride in rain water a t Mount Vernon, Iowa. The fact that the results differ by multiples of 3.55, which the authors state was the amount deducted for the blank, suggests that the titrations were made with too small a sample or too strong a solution, or both. A previous paper ( 5 ) from the same laboratory reported that no chloride was found in the samples tested. Some indication of the upper limit for chloiide in rain water may be obtained from analyses of river and lake waters ( 3 ) . In 1906-7 daily samples were collected a t sixty-seven points on rivers for analysis of composites; at eighteen points the average chloride for the year was between 2 and 3 p. p. m., and a t four points the average was less than 2 p. p. in. The average for twelve single samples from Lake Huron was 2.6 p. p. m., and for samples from Lake Superior, 1.1 p. p. m. A better indication of the chloride in rain water is given by so-called chlorine maps (4) published some years ago. The estimates of ‘kormal chlorine” were based on very careful determinations of chloride in samples of pond, well, spring, or stream waters that mere believed to be unpolluted. The generalized map for New York and Kew England shows chloride starting with 6 p. p. m. near the coast and decreasing to 1 p. p. m. between 50 and 100 miles inland, and to 0.2 p. p. m. beyond about 300 miles. A recent report ( 2 ) shows a number of 10-day composites of daily samples of river water in Virginia with less than 0.5 p. p. m. of chloride. These results all lead t o the conclusion that the greater part of the total rainfall over the United States carries much less chloride than is suggested by a mere averaging of reported analyses without regard to the location of sampling points or methods of analysis. During the last two years over two hundred samples of rain water from several different places in the United States have been examined in the Geological Survey for chloride and sulfate. Chloride was determined by titration with silver nitrate solution of which I cc. is equivalent to 0.5 mg. of C1. Each of the results in Table I is the average of two determinations made either on one 250-cc. portion and one 500-cc. portion, or on two 500-cc. portions of the sample after concentration by evaporation to 25 cc. In some determinations a small amount of sodium bicarbonate was added to one aliquot and not to the other. This made no difference in the results and indicated that there was no loss of chloride during the concentration. The correction for the chromate
end point was equivalent to 0.1 p. p, m. of C1 for a 500-cc. sample. TABLE
I.
CHLORIDE A S D SULFATE I S
S A M P L I NPOINT Q .ilfred, Me. Blacksburg, Va. Flagstaff Ariz. Grand Cknyon, Ariz. Kearnev Nebr. Seattle, h’ash.: N. 11‘. section S. W.section Wailuku, Maui, Hawaii Washington, D . C.: Interior Dept. Bldg. Residential districts: A
B
RAIN WATER.
-CHLORIDE--SULFATESAMPLESMax. Min. Av. Max. hlin. Av. Parts wer million
7 4 5 3 18 31 13 8
0.5 0.6 2.0 0.9 0.5
0.05 0.1 0.2 0.1 0.05
0.26 0.30 1.0 0.37 0.14
5.8 0.1 1.3 2.9 0.05 1.4 45 0.8 11
5.8 2.1 4 3.5 3.6
1 0.7 1 1 1
22 1 17 1 9.9 2
2 1.4 2 2
2 6.3 7.2 3.5
54
3.0 0.05
0.70 30
14 7
0.6 0.05 0 . 5 0.05
0.26 13 1.4 3.7 0.26 6.5 1.6 3.5
2.8 9.5
Analyzed by K. T. Williams.
Sulfate determinations were made on all samples by turbidity ( I ) , and on many of the samples sulfate was also determined gravimetrically.‘ The results given in Table I are averages of closely agreeing determinations on duplicate samples. Rain samples collected in a city are obviously contaminated by the soot and fumes from the combustion of fuel and should not be given much weight in considering the total precipitation. A collecting basin allowed to stand in the open before a rain will collect solid particles, which n ill increase the quantity of dissolved material in the rain sample. Samples collected near the seashore are contaminated by sea spray when the wind is landward. The distance the spray is carried inland and the amount carried must vary with wind conditions. Although the average chloride for the samples collected on the roof of the Interior Department Building a t Washington was over twice and the sulfate nearly three times the average for samples collected in residential sections, the results are low for the metropolitan area of a city. The Seattle samples were collected within 2 miles of Puget Sound and show the effects of city contamination and ocean salt. When the wind is blowing landward from the salt water, the rain contains slightly more chloride than when the wind is blowing seaward from the land. From the point of collection in Wailuku the distance to the ocean in the direction of the n-ind ranges froin 0.2 to 8 miles. The maximum chloride was obtained when the wind blew salt spray 0.2 mile to the sampling point, and the minimum was obtained when a weak wind traveled 7 miles overland to the sampling point. Although the sampling point a t Alfred, Me., could receive salt particles from ocean spray carried only 13 to 30 miles according to the direction of the wind, the chloride did not average much more than a t points several hundred miles inland. The samples from Kearney, Nebr., are probably most like the rain that falls on the farms, forests, and uncultivated lands that make up nearly all the land area of the United States, but the sulfate in the rain water from Kearney undoubtedly comes in part from the combustion of fuel in homes. The results summarized in Table I and others from places a t which only one or two samples were obtained suggest that the greater part of the water being carried t o the ocean from the United States contains less than 0.3 p. p. m. of chloride and not more than 2 p. p. m. of sulfate when it reaches the surface of the earth as rain or snow. These quantities are
944
1
T h e gravimetric sulfate determinations were made b y L. G . Davidson.
\ogast, 1933
13 I A
I.
A 1 I)
ii
>G
w~uivaIeritto U.Oi pound of C1 and 0.15 pound of S per acre iier inch oi rain. I,ITEaa'P17llE ClTED
( I ) Coliins.
W. I).. and Fester, M. D.. IND.
C'm>r., 15, 111%
I N E IS II I N
(;
c I I IS 51 I s 'r w Y
945
W Doie, R. B., U. S. Gecl. Surrey, Water Supply Paper 236 (1~09). (.1) .JarBon, D. D., Ibid., 144 (IBO5).
(5) Moore. W. A , . and Ilrowning, Glen, Cbcm. A'cvs, 122,51-2 (1921). (6) Riffonburg,H. 13.. U. S. Grol. Survey, Water Supplu Paper 560, 31-53 (1!m). i i i William, F. S.,ami Bcdhr-,
Ii. O., C6em Newa. 145, 4a-3
(1982).
(1923). ( 2 ) Collins, W. D.. Lohr. E. W., WiYiams, Xi. T.. Ilalle~, Kenworthy, 0. C.. Va. Stato Comrn. Conaorvatior velopmont. Lfir. Water Resources and Power. Bull.. 3 (1st
RECELVBD February 15. V S Geoioyieai Survey.
l9SS.
i'ublisiied
by p e r i n i ~ s i o nof lie Director.
AMERICAN CONTEMPORARIES b'ranz
I?. l3xner
11IXTY years ago rm :tIumnus, fvrsh from his dociornte at Penirrylvania, returnod t o Carleton College, Sorthfield, Minn., i ~ n dt h e 1,egn.n his career BR a teacher and friend TodsLy, Frprnz F. Exnw is the senior of students in chemi culty and is loved and rrvrred hy reniricmber of the Carlet erat,ions of students have through him
.)
in the value I h e r obtiiirrell for the atomic weight of tungsten. The average of his dete,nninutions as published a year later is given :m 184.05, ahieli agrees with the accepted value of 184.Bin use today. In li~t,eryen, B teacher, ICxner has successfdy instilled t,hesc same habit rrccumcy in many oi his students. Because of the promise shown in research, he wit.; ernnted the IIii,rrison Resenrch Fellowship r-hieh he hrdd during theacadeniio year 19023. 'The fall of tW3 found Dr. Zmer back a t his
received their first stimul;it,ing contact with the Fiindamenlals and intricecies of chemistry. It rnny truly be said that Doctor Isxner has unalma mater and t h e w he has remained &B stintingly given of his time and effort tu the d e v e l o p m e n t of il first&cli%ss dcpartment oi tencher, wise councilor, a.nd friend of students. chemistry a t Carletm. l m g d y as a rcsrilt lnays stressed the fundaof tiis effort.^ over this thirty-year period, .elationships in tho scicnce Carleton today !masts of one of the liest chem:md iwi-ti4 on II high order of achievement in his students. Ifis CIRIY~E arc cnlivened by istry buildings and dep'lrtments of any of the lilieral arts colleges of the country. bits of droll humor. Pranz Frederick Exner \vas horn in the As a young man Ennei w a much intereated d h g e of Wokendor1 in Sileain, at, that time in i n gpmnnstic work, such as ono finds in the t,he Austrian part of Anstriidrringhry. As a German I'urns?rrin, as a means of keeping physical fitnws. So strongly did he believe Iwy he came to this country and in 1888 entcrod the preparatory deportment, oi Carlotori t!mt some form of physical activity ,%-asneeded Colle~e, lie r:ompleted this work in three liy thr student Iiody that hc organized the first p a r s and entered the college propci in 1891, F n . k ~ zF. E K ~ e r i elssses in gyrriiiaStic work at Cnrleton. He himself was an excdent gymnast and, even graduat,ing with Ibis bnchelor's degree in 1895. I t was his intention nn entering college to prepare liimsrlf for whm physicd cducation developed to thc point of becoming ademedicine with the hope that he could become a mediral rnission:rry. p r t m e n l ~of tlir college, he oft,en assisted in training stutient,s for On leaving collage it Ijociime necessary for him t o teilrii for gym" events. In spite of the fact, t,liat he does not impress :t time in ordcr tlint he might Ist,er enter h i s chosen field. In one R ng physically strong. Emer'n diligent application of t!ir meantime he w m s becoming more and more interested in ihr ~ o o dplrysic,ill-trainiiig principles has kept him in excellent hcnlth. vtpidly developing science of clremistry rmd by 1900 he h:uI deA s is expected in a cnllege of the type oi Carlet,on, teaching ihicd to give iip B career in niotlicinc for one in chemistry. mines before invtwtigntion, rind Professor Ikner carly decided The clrnracter of work being done by lklgsr F. Smith mcl his to g i w his liest to t,raehing young students. Elowever, lie has co-workers at 1'rnnaylvmni;i appealed to young Exner; lie 1,here- OPVW lost iriterest in research :mi! there is ~thrayssome work fore Amtrieulated at I'cnnsylvanis and cndcred on his graduatt going on in his own laboratory. Ire i s continually working out w r k under the guidnnce of Professor Smit,h. %ith mudi en- new methods or new rcfinernentsuf old methods for his clnsaes in m arid energy he at,t;tcked the problem of defcrmining rinnlytical chemistry. Some of these results are of considerable tlrc rrtomic weight, of tungsten. By the Fpring of IN):% t h i s E- importance, Iiot Exner has always Ireen more i n l w w t d in obt.ninsearch had been completed and the i-erultsobtnined were intended ing results than in rustring (,hem into print. Jle much prefers to mrry on his own work in the absence of public recognit.ion, and to he iisod as t h e doctor's dissertation. One afternoon Smith ~ ~ i i to i e the young invcstigator and informed him of the- work this retiring nature has kept him from being better known by his then in progress under Goooh u t Yale on the use nf :irotating fellon chmrists. In addition to the investigations in analyt,ical cr&hude in the electrodeposition of mehls for nnnlyticirl work. rhemis?ry he lias done :i ronsider.%blramount of work on the It w:is suggest.ed that a rota,ting unode be tried a,nd Exner in]- catalytic dehydration of orgnoic compounds, using slightly oxlniediritely seized upon tho idea. Within three days he had de- dised copper a6 tho eatdyst. He has also been interested in veloped 2% method and obtained quantitative result? that indi- using ngriculturd products in chemical indodry. These fields of cttted the valiie of this method in a n d y t i d chemistry. T l w e work studied in his own i d m a t o r y with his own hands indicate results looked so promising that the next three months were rpmt his breadth of interest in the science. A m ~ yfrom the college, Exner has been B home hady and home in rounding out bhe preliminary investigation. Long hours of intense sctivity were needed, but, in the end it was this pime of lover. He was married to llannah Longstreet Alythe in 1897. research which was used by E h e r for his degrec. They !mve six children, four boys and two girls, and in them they Tho care and accuracy of his work at Pennsylvmia i s reflected have tnken great pride and comfort. Four of the children have
