2. Precipitation Chemistry Data

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STIMATING TH ATMSPHRIC INT A WATRSH INPUT F PLLUTANTS PRRY J. SAMSN epartment f Atmspheric and ceanic Science, University f Michigan, Ann Arbr, All 4819-2143, U.S.A. (Received June 2, 1986; revised March 11, 1987) Abstract.

1 STIMATING TH ATMSPHRIC INT A WATRSH INPUT F PLLUTANTS PRRY J. SAMSN epartment f Atmspheric and ceanic Science, University f Michigan, Ann Arbr, All , U.S.A. (Received June 2, 1986; revised March 11, 1987) Abstract. stimating the atmspheric input f ins t a watershed has traditinally been accmplished thrugh either the extraplatin f pint measurements f depsitin r the integratin f mdel estimated depsitin. This paper examines the characteristics f precipitatin chemistry n the eastern seabard f the United States where precipitatin quality culd cnceivably affect fish habitats in estuaries. The measured values presented here have been extracted frm the data base f the Utility Acid Precipitatin Sampling Prgram (UAPSP) precipitatin chemistry netwrk. These data illustrate the nature f inic depsitin at fur pints n the eastern seabrd. The depsitin f H (acidity) is shwn t be dependent upn the amunt f sulfate and, t a lesser degree, nitrate in the precipitatin. It is als shwn that the quantity f inic depsitin n a strm-by-strm basis was influenced by the amunt f water depsitin but the relatinship was nt very strng. Thus the use f water depsitin as a surrgate fr inic depsitin is nt justified in these watersheds. Finally, it is shwn that the depsitin f H +, S42-, N3-, and NH~ were nt clearly seasnal. While a large percentage f ttal inic depsitin ccurred in a small number f precipitatin events, these exceptinal events were nt cnfined t a particular seasn. I. Intrductin The input f inic material int a watershed can be estimated by either extraplating pint measurement values r integrating transprt and depsitin mdel results. The latter technique is still in its infancy and the mdels emplyed have yet t be verified as accurate. Nnetheless these techniques are useful in identifying the regins mst likely t have cntributed t depsitin. This paper, hwever, fcuses n the extraplatin f pint measurements t a watershed. ata available frm the Utility Acid Precipitatin Sampling Prgram were used t examine the characertistics f inic depsitin t watersheds n the eastern seabard. Annual average depsitin amunts are presented fr fur sites with drainage int east cast estuaries. Additinal analysis f ther UAPSP sites has been perfrmed by Samsn and Mdy (1986). 2. Precipitatin Chemistry ata The Utility Acid Precipitatin Study Prgram (UAPSP), having cntinued and expanded a mnitring netwrk established during the lectric Pwer Research Institute (PRI) Sulfate Reginal xperiment, prvided a high quality, lng-term chemical data base fr this applicatin. The UAP SP is a mnitring prgram develped under the guidance f PRI t cllect and analyze daily precipitatin samples in the eastern United States. etails f the UAPSP sampling and analysis prgram may be fund in the UAPSP annual summary reprt (1984). Figure 1 shws the lcatin f Water, Air, and Sil Pllutin 35 (1987) by. Reidel Publishing Cmpany.

2 8 PRRY J. SAMSN Fig. 1. Lcatin f the Utility Acid Precipitatin Study Prgram Precipitatin Chemistry Sampling Netwrk. TABL I Name and lcatin f the utility acid precipitatin study prgram precipitatin chemistry sites Site Lcatin Latitude Lngitude 1 Turners Falls, Massachusetts ' 7255 ' 2 Tunkhannck, Pennsylvania 41 35' 76 ' 3 Indian River, elaware 38 35' 75 15' 8 Raleigh, Nrth Carlina 35 44' 78 41'

3 ATMSPHRIC INPUT F PLLUTANTS INT A WATRSH 9 UAPSP sampling statins used in this study. Table I lists the number and lcatin f the sites. The UAPSP data base prvides users with infrmatin which includes: (1) the day and hur the first precipitatin started and the day and hur the last precipitatin ended; (2) the precipitatin amunt; and (3) a thrugh chemical analysis f the majr inic species in slutin. The nly meterlgical infrmatin included in the data set was in the frm f sample cdes which were used t differentiate events as (1) snw/ice events, (2)mixed (liquid and slid sample) events r hail events, (3)uncded events (indicating precipitatin fell as rain), and (4) events with thunder. This infrmatin was used t determine the influence f precipitatin type n inic cncentratins. The fur sites investigated in this wrk include: Site 1, Turners Falls, Massachusetts; Site2, Tunkhannck, Pennsylvania; Site3, Indian River, elaware; and Site8, Raleigh, Nrth Carlina. epsitin at these sites shuld be representative f atmspheric input int the upper Cnnecticut River, the upper Susquehanna River, the elaware/chesapeake Bay regin, and the Nrth Carlina castal plains, respectively. Clearly large variatins in depsitin are pssible acrss a watershed due t variatins in precipitatin amunt and air quality. These sites are presented nly t illustrate the nature f depsitin in these regins. 3. Results The depsitin f H is dependent upn the amunt f anins available in the precipitatin. At the eastern seabard sites the H is largely dependent upn sulfate (S42- ) and nitrate (N;-). Figures 2(a) and 2(b) cmpare the 1979 cncentratins* f S~- and H and N 3 and H, respectively, at the Indian River site. There was a strng linear crrelatin between S~- and H with a rati f H /S42 - which was slightly greater than ne. The H cncentratins were als related t N 3 cncentratins but the rati apprached tw t ne. The amunt f inic material depsited in a strm shuld intuitively be related t the amunt f water being depsited. Figure 3(a) shws, hwever, that day-by-day S4 z- depsitin was nly weakly related t the cncurrent water depsitin. This lack f crrelatin was the result f fluctuatins in the cncentratin f S42- in precipitatin. Such fluctuatins are expected due t varying cncentratins f atmspheric S 2 and S42-. The Sn 2 - cncentratin in precipitatin has been shwn t vary seasnally (cf. Wilsn et al, 198). This alne culd lead t pr crrelatin between day-by-day water and S42- depsitin ver the curse f a year. n the ther hand, Figure 3(b) cmpares N3- depsitin with water depsitin and finds a similar lack f crrelatin even thugh N 3 des nt display a seasnal scillatin in cncentratin. Hence, the pr crrelatin between water depsitin and inic depsitin must be the result f * Inic cncentratin is expressed as mass per unit vlume f water, whereas inic depsitin is expressed in units f mass per area. Cncentratin cmparisns will be used here when discussing prcesses but depsitins wil be cited when discussing input t watersheds.

4 1 PRRY J. SAMSN 5 m " J 4 n t- C +,I U S I I I I I S 4 Cncentratin (geq [1) Fig. 2a. Cmparisn f the cncentratin fh + and S42 in precipitatin events recrded during 1979 at the Indian River, elaware UAPSP site. 5 " t- ) c L) + " n f I I i I, N3Cncentratin (geq [1) Fig. 2b. Cmparisn f the cncentratin f H + and N3 in precipiratin events recrded during 1979 at the Indian River, elaware UAPSP site.

5 ATMSPHRIC INPUT F PLLUTANTS INT A WATRSH 11 4 ', 3 e.-._ 2. J,, ~. 1 ~ I I I Water epsitin (kg-rri 2) Fig. 3a. Cmparisn f the depsitin f Sl- and water in precipitatin events recrded during 1979 at the Indian River, elaware UAPSP site. 2 ' ,m. c~ 5. z l B. ~ 1, Water epsitin (kg-rfi 2) 8 Fig. 3b. Cmparisn f the depsitin f N 3 and water in precipitatin events recrded during 1979 at the Indian River, elaware UAPSP site. the changing clud and pllutant envirnment n a day-by-day basis. Mrever, this demnstrates that water depsitin was a pr surrgate fr inic depsitin at these sites. The depsitin f ins int a watershed via precipitatin is an intermittent prcess with the bulk f the annual depsitin ccurring in a few majr events. Figure 4 shws

6 12 PRRY J. SAMSN 1% H2 Z 8% i I- I.LI Q 6% _1,, I-- I-.. " 4% I- z u.i n- 2% uj N 4 H + HALF F TTAL PSITIN FALLS IN LSS THAN 2% F VNTS % 2% 4% 6% 8% 1% PRCNT F PRCIPITATIN VNTS Fig. 4. The cumulative frequency f depsitin f H, S~ -, N3-, NH4 +, and water ver the year 1979 at the Indian River, elaware UAPSP site, TABL II Annual depsitin ttals fr fur UAPSP sites in eastern seabard watersheds Site Year Water H + S42 - Nr NH~ (kgm -2) (kgha -1) (kgha -1) (kgha -1) (kgha -1) Turners Falls, Massachusetts Tunkhannck, Pennsylvania Indian River, elaware Raleigh, Nrth Carlina , ,

7 . ATMSPHRIC INPUT F PLLUTANTS INT A WATRSH 13 TABL III epsitin ttals fr the perid March t May fr fur UAPSP sites in eastern seabard watersheds Site Year Water H + S] - N~- NH~ (kgm -2) (kgha-l) (kgha-l) (kgha-a) (kgha-x) Turners Falls, Massachusetts Tunkhannck, Pennsylvania Indian River, elaware Raleigh, Nrth Carlina '7, 2- n.. m.. f~ 16 12, 8- n m 4- - N~ Annual H2 epsitin (kg m "2) Fig. 5. A scatter plt f annual depsitin f S]- and N~- versus ttal water depsitin fr fur years at Tunkhannck, Pennsylvania. the cumulative frequency distributin fr depsitin f water, H +, Sl-, N3-, and NH4 + at the Indian River, elaware UAPSP site. This plt shws that 5% f the ttal depsitin f all species ccurred in nly abut 2~ f the precipitatin events. Mrever, abut 9 9 f the ttal annual depsitin was accunted fr by nly half f

8 14 PRRY J. SAMSN 8 7,,= tn Q. N I"I i~] [3 n ~ ~ n n ~ n l~l~, Iq~] I~, ~nnq t'1 ~ n, i-i J F M A M J J A S N 1979 Fig. 6a. The amunt f depsited water in each precipitatin event measured at the UAPSP site in Indian River, elaware during H* n A g n J F M A M J J A S N J 1979 Fig. 6b. The amunt f depsited H in each precipitatin event measured at the UAPSP site in Indian River, elaware during 1979.

9 ATMSPHRIC INPUT F PLLUTANTS INT A WATRSH s; 4 3 : u) Q ~,~ ~ nd~ i# ~ ~--~i~ -I n d~] Fig. 6c. J F M A M.J J A S N J 1979 The amunt f depsited S ]- in each precipitatin event measured at the UAPSP site in Indian River, elaware during N~ = 9 g ~ 6 3 ~ u n? ea ~,,% _a J F M A M J J A S N J 1979 Fig. 6d. The amunt f depsited Nr in each precipitatin event measured at the UAPSP site in Indian River, elaware during 1979.

10 16 PRRY J. SAMSN 8 6 ~ I g.j 4 2 n n rl ~ nb~. ~% Fig. 6e. d F M A M d J A S N d 1979 The amunt f depsited NH4 + in each precipitatin event measured at the UAPSP site in Indian River, elaware during the precipitatin events in the year. Thus the influence f inic depsitin n the chemistry in precipitatin and hence in streams was generally dminated by extreme events. In nrthern regins, hwever, it is pssible that the accumulatin frm several strms in snwpack culd als have caused significant changes in stream chemistry during melting perids. This is nt addressed in this paper. The annual depsitin amunts f H +, S]-, N3, NH4 +, and water at the fur sites are listed in Table II. The amunt f depsitin varied frm site-t-site and year-t-year. Nte, fr example, that 1983 exhibited relatively high depsitin f inic material at each f the available sites due in large part t the greater depsitin f water. The elaware site exhibited the highest depsitin f H + and S42- f the fur sites but this was based n nly ne year f data. The variatins in depsitin amunts when the data were stratified by spawning seasn did nt mirrr the annual results. Table III lists the amunt f depsitin during the warming mnths (assumed t be March t May) when anadrmus fish were presumably spawning in these watersheds. While the number f years f depsitin measurements in the eastern seabard area were limited, the data shwed that variatins in annual inic depsitin have nt been linearly related t variatins in annual water depsitin. Figure 5 shws a plt f S4 a - and N3- depsitin versus the ttal water accumulatin fr each year at the Tunkhannck, Pennsylvania site. The irregularity f the scatter implies that it is nt reliable t infer variatins in even annual inic depsitin based n the fluctuatins f annual precipitatin amunt.

ATMSPHRIC INPUT F PLLUTANTS INT A WATRSH 17 The variatins in depsitin f H +, S42-, N3, NH2, and water ver the curse f the year are displayed in Figures 6(a) thrugh 6(e), respectively.

11 ATMSPHRIC INPUT F PLLUTANTS INT A WATRSH 17 The variatins in depsitin f H +, S42-, N3, NH2, and water ver the curse f the year are displayed in Figures 6(a) thrugh 6(e), respectively. All ins shwed cnsiderable variability ver the curse f the year with n cnsistent seasnal trend evident. nly S42- exhibited any seasnal scillatin as a result f a few high depsitin events in the warmer mnths. Nnetheless, the prbability f high depsitin values was similar in virtually all mnths. 4. iscussin The depsitin f H + has been shwn t be dependent upn the amunt f sulfate and, t a lesser degree, nitrate in the precipitatin. This relatinship has been demnstrated t be true fr mst measurements sites in the eastern United States (Samsn and Mdy, 1986) and is nt surprising. It has als shwn that the quantity f inic depsitin n a strm-by-strm basis was influenced by the amunt f water depsitin but the relatinship was nt very strng. The variatins in inic depsitin were due t variatins in cncentratin. ven the annual depsitin ttals shwed little relatinship between ttal water depsitin and the ttal depsitin f S42- and N 3. Hence, the use f annual precipitatin amunt t infer variatins in inic depsitin is nt justified. The depsitin f inic material (and water, fr that matter) was highly weighted twards a few 'exceptinal' events during the year. Further, these high depsitin events ccurred in any seasn in the eastern seabard regin f the United States. The year-t-year variatins in depsitin amunt during 'spawning seasn' were relatively large. The relatinship f these fluctuatins t changes in anadrmus fish ppulatins remains t be studied. The extraplatin f inic depsitin measurements t a watershed is prbably the mst reliable methd fr estimating atmspheric input f pllutants. Nnetheless, this paper has illustrated hw this prcess has limitatins. These limitatins include the nnhmgeneity f precipitatin patterns acrss the watershed (cf. Napp et al., 198) and nnlinearity between inic depsitin and water depsitin. It will be useful in the future t identify ther envirnmental factrs such as extremes in temperature and precipitatin t see if these factrs can be linked t changing fish ppulatins. The relative imprtance f climatic factrs, pllutant depsitin and ther prcesses remains t be identified. References Napp, C. J. and Gabbard, L. J.: 198, Mnthly Weather Rev. 18, Samsn, P.J. and Mdy, J. L: 1986, The Influence f Meterlgical Factrs n Precipitatin Chemistry, Reprt UAPSP-111, lectric Pwer Research Institute, Pal Alt, CA. UAPSP Summary Reprt: 1984, Acid Precipitatin Study Prgram Secnd Summary Reprt, Reprt UAPSP-19, lectric Pwer Research Institute, Pal Alt, CA. Wilsn, J., Mhnen, V. A., and Kadlecek, J. A.: 1982, Atms. nvirn. 16, 1667.

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