### Winter Deposition of Nitroge n a nd Sulf ur in the Eastern C o lumbia River Gorge National
Scenic Are a

Final Report to the USDA Forest Servic e, Region 6 Air Resources Program

Mark E. Fenn and Tim o t hy J. Blubaugh

USDA Forest Service, P acific Southwest Resear ch Station, 4955 Canyon Crest Drive, Riverside,
CA 92507

February 3, 2005



### Executive Summary

As a prelim inary evaluation of the potential im pa cts of air pollution on natural and cultural

resourc e s in the eas tern Colum b ia River Gorge (CRG), nitrogen (N) and sulfur (S) deposition in fog, bulk deposition and throughfall and the level of acidity o f fog and pr ecipitation were
monitored d u ring th e winter wet s e ason (2003- 2 004). Atm o spheric d e pos ition s a m p les were collected at eleven sites along th e C R G, with a focus on the Nati onal Scenic Area in the eastern end of the gorge. Nitrogen deposition inputs in throughfall were surprisingly high w ith N deposition fluxes ranging from 11.5 to 25.4 kg ha -1 . Amm oni um deposition in throughfall was higher in the m o re easterly sites, presum ably b ecause of agricultural em issions of ammonia and possibly industrial em issions. As exp ected, ionic concentratio ns of N and S were m a ny-fold higher in fog than in bulk preci pitation and the pH of fog wa s generally lo wer than the pH of precipitation. The pH of fog and bulk deposition varied te m p orally, but pH values were commonly between 4.0 and 4.5 and lower than 4.0 in som e instances. The levels of atmospheric deposition, and particularly that of N, are at le vels shown to have ecological im pacts in western ecosystem s as a resu lt of N enrichm e nt. Im pacts of N deposition on sensitive lichen co mmunities in the gorge has already been dem o nstrated. Furt her stud ies a r e needed to m o re f u lly ascer tain
the im pacts of acidic deposition and N enrichm e nt on cultural and natural resources within the
eastern CRG.



### Introduction

The Colum b ia River Gor g e Nationa l Scenic Area, located along a portion of the Oregon/W a s h ington border, is an area highly valued for its scenic, cultural, and natural resources. Unfortunately the Colum b ia River Gorge (CRG) has also becom e a conduit of air pollution transport from em issions sources located within the gorge and to the west an d east of the gorge. T h is study was initiated to determ ine the level of nitrogen (N), sulfur (S) and acidic deposition o ccurring in p r ecip itation, fog or cl oudwater. The com b ined deposition of N and S in wet and dry for m s was also estim ated from th roughfall m easurem ents. Throughfall is the flux

m easurem ent of N and S washed from tree can opies during precipitation and fog events. In the Columbia Basin in winter (Novem ber to early March ) air s t agnatio n episodes are a relatively frequent event. During these events, w h ich can last for days to weeks, air pollution

1em itted in th e basin is tra pped by the geogra phic barriers arou nd the bas i n and capped by a

tem p erature inversion which settles over the region preventing verti cal m i xing or transport of the trapped air m a ss. The CRG is the prim ary outlet for this polluted air m a ss. The cold dense and very hum id air se ttles into the lowes t areas – p a rticularly the river bottom a nd in the eastern end of the gorge. This air m a ss slowly drains westwa rd and out of the basin as it m oves through the Gorge. The cold air m a ss drainag e flow is often accom p anied by low clo uds and fog which entrain the trapped air pollutants. Pollution sources in the basin, concentrated m o stly along the rivers, include a num ber of

recen tly con s tructed po wer plants, mostly natu ra l gas, bu t in cluding the Boardm an Coal Fired Power Plant, located about a hundred km east of the Scenic A r ea which is the largest point
source in the Colum b ia Basin. This so urce em itted 13119 tons/year of SO 2 and 10080 tons of
NOx in 2003 from EPA com p iled inventories. Notably, the area imm e diately adjacent to
Boardm an i n cludes a v e ry larg e feed lot, a po int source of ammonia e m issions. Several proposed new plants h a ve perm its and are under constructi o n or are waiting for energy m a rket conditions
to im prove before construction is commenced. Se veral are in the perm itting stag e. W ith the large num ber of existing and proposed facilitie s the basin has becom e an energy farm

. Additiona lly there are f o ur alum inum s m elters – two in the gorge at The Dalles and Goldendale, a third near Wenatchee, and one in S pokane. Ho wever, these facilities are currently shut down or operating at low capacity beca use of poor m a rket conditions – the sm elters were not operating
at the tim e of this study. There is als o a pulp and paper m ill and a fertilizer plan t at Wallu la, several food processing plants wi th boilers at Boardm an, and ex tensive agricultural operations with large acreages of grain cr ops. A num b er of urban areas are also found within the river gorge and in the surrounding areas, including Pendleton, Herm iston, the Tri Cities, Hood River, The Dalles, Yakim a , Ellensburg, W e natchee, Spokane, W a lla W a lla, and sm aller comm unities. Each of these has the expected suite of urban em i ssions m o stly dom inated by transportation. The gorge also has two railroad tracks with tr ains approxim a tely every 20 m i nutes, two m a jor highways with car and truck volum e, and on-river ba rge traffic. In the cu mulative s e n s e all of
these sou r ces contribute to the ba sin and gorge air quality proble m -- generally in proportion to their size, distance, and local m e teorological conditions. The polluted air m a ss that drains thru the CRG in winter is believed to be responsible for an air pollution signature se en in the lic hen tissu e sa mples and lichen spec ies community shif ts (Geiser and Neitlich, 20 03). Lichens are an ex cellent bioindicator for air pollution effects. In this case lichen species sensitive to high S concen trations are largely absent even though these species are endem i c to the area. Som e weedy lich e n species known to thrive in N rich polluted
environm ents are abundant (Fenn et al., 2003). Lich en tissues absorb pollutants. T i ssue sam p les
from pollution-tolerant species have been anal yzed for N and S concentrations. The N and S
concentratio ns of the lic hen tissu e c o llec t ed in the CRG are relatively high com p ared to other
areas in the Pacific Northwest. This inform ati on indicates high N and S deposition rates in the
CRG. The potential acidity of atm o spheric deposition in the CRG has raised co ncerns th at p r otected
cultu ral reso urces, pa rtic ular ly India n rock ar t, ar e being ha r m ed and over tim e will d e ter i ora t e from winter imm e rsion in this polluted air m a ss. The data on changes in the chem istry and community com position of lichens indicates othe r adverse ecosystem effects are occurring as a result of atmospheric d e p o sition. Th e purpose of this study was to quantify N and S deposition in fog, bulk precipitation and throughfa ll and to measure the acidity of fog and bulk precipitation at
sites located across the CRG as an indicato rof the potential for ecological and env i ronm ental
im pacts of current levels of atm o spheric deposition.

2

### Methods

At m o spheric deposition monitoring was carried out at eleven sites acros s the CRG (Fig. 1 and Table 1). Three types of sam p les were collected. Bulk precipitation and fogwater were collected in open areas, and throughfall wa s collected under ponderosa pine ( P i nus ponderosa Laws.) canopies. B u lk deposition was collected at all elev en sites, and throughfa ll was collected at all sites except Mt. Zion (MZ) and W i shram ( W I) where there w e re no pine trees. Fog samples were
collected at seven sites. The sa m p le colle ctor s were ins t a lled in the m onitoring sites d u ring th e last week of October 200 3 and contin ued to collect sam p les until M a rch 9, 2004, for a total collection period of 19 weeks, or nearly 4.5 m onths. Three replicate bul k deposition collectors
were installed at each site. Ten throu ghfall collectors were inst alled per site, distribu ted under 5- 7 trees, except at Celilo wher e due to access lim itations, four th roughfall collectors were placed under a single large pine tree.

Table 1. Site s within the Colum b ia River Gorge at which atm o spheric deposition sam p les were
collected.

Site Nam e Site abb r eviation and type of sam p les
collected § Elevation (m ) Coordinates

Mt. Zion MZ (bp, f) 225 N 45° 34' 9.84"
W 122° 12' 41.04" Twin Tunnels High TTH (bp, tf) 164 N 45° 41' 32.77"
W 121° 27' 01.97"
Twin Tunnels Low TTL (bp, tf) 115 N 45° 41' 25 .94"
W 121° 26' 48.29" Catherine Creek High CCH (bp, tf) 385 N 45° 43' 20.66"
W 121° 22' 58.98"
Catherine Creek Low CCL (bp, tf) 125 N 45° 42' 45.28"
W 121° 21' 57.34
Sevenm ile Hill 7MH (bp, f, tf) 520 N 45° 38' 13.20"
W 121° 17' 55.72"
Klickitat KLICK (bp, tf) 207 N 45° 43' 23.76"
W 121° 15' 32.62"
Horse Thief State Park HTSP (bp, f, tf, wd) 33 N 45° 38' 41.42"
W 121° 06' 26.87"

W i shra m W I (bp, f) 232 N 45° 39' 56.98"
W 121° 00' 2.59"
Celilo Celilo (bp, f, tf) 19 N 45° 39' 03.89"
W 120° 57' 34.73" Maryhill MH (bp, f, tf) 216 N 45° 40' 37.36"
W 120° 51' 59.19"

3§ Types of samples are as follows: bulk precipit ation (bp), fog (f), throughfall (tf), or w e t deposition (wd). Note that fog co lle c t ors were ins t alled at Klick itat, but no data are presented because of infrequent fog events, very low fog sample volumes and vand alism of the collectors.

The m o st wester ly s ite was MZ, which is a National Atm o s pheric Deposition P r ogram (NADP) m o nitoring site, that is located at the Po rtland end of the Gorge. The other ten sites are
to the e a st w ithin the CRG National Scenic Area (Fig. 1). Precipitation decreases dram atically
from west to east across the CRG. Fr om Bonneville Dam

, near MZ to th e west of the Scenic
Area to The Dalles in the easte rn end of the gor ge within th e Nationa l Scen ic Area, ann u al precipitation in the 2003/2004 wa ter year decreased from 176 cm to 39 c m (Table 2). Bulk precipitation sam p les were collected with a standard rain gauge funnel (10 cm i.d.) connected to a polyethylene st orage bottle. Throughfall sample s were collected under ponderosa pine trees with collectors using the sam e funnels described for the bulk precipitation sam p lers. Deposition of N and S i n throughfall was collected using ion exchange resin (IER) throughfall collectors which are composed of a funnel collector openi ng that directs throughfall (precipitation collected below tree canopies) so lutions to percolate th rough an IER colum n. Details of these IER collectors are described in F e nn and Poth (2004). These collectors are designed so that liquid sam p les are not collected. Instead, ions in the throughfall solutions are captur e d by the IER with in the co lumns. At the en d of the m o nitor i ng per i o d, the res i n c o lum n s were extracted with 1 N potassium iodide as described by Simk in et al. (2004). N itrate and sulfate in the extracts were analyzed by high perfor m a nce ion chrom a togra phy (Dionex, Model DX600; Sunnyvale, CA) and a mmonium wa s analyzed w ith a TRAACS 800 Autoanalyzer (Tarrytown, NY). At the Twin Tunnels (TTL, TTH) and Cather ine Creek (CCL, CCH) sites, bulk deposition was also collected with IER collectors as opposed to weekly collections of liquid sam p les. Throughfall m easure m ents provide a m easure of deposition fluxes under plant canopies. Plant canopies function as effective fog and dry deposi tion collectors, resulti ng in elevated ionic deposition to the soil under the canopy. Thus, th e areas under plant canopie s receive th e brunt of concentrated pollutant deposition in fog or cloudwater and w a shoff of ac cum u lated dry deposition. Fog sam p les were obtained with passive fog line collectors that coll ect fog or cloudw ater, using a design slightly modified from that described in Fenn et al. (2000). The fog collecting
surface was com posed of 168 teflon string s, 30 cm in length, arrang ed in two concentric circles,
8.0 and 8.2 cm in dia m e t er. The teflon strings we re 0.4 mm i n diam eter. The liquid collected by the strings during fog events drained into a f unnel base and was collected in a polyethylene bottle. A plastic trash can lid (0.5 m diam eter) was m ounted above the fo g collectors to prevent the collection of rain from above. However, it should be noted that the passive fog collectors were not designed to exclude the collection of wind-blown precipitation. Thus, som e of the fog

sam p les are like l y to in clude prec ipitation in so me instances. However, the m u ch higher ionic
concentratio ns of the samples collected by the fog sam p lers com p ared to the bulk deposition

sam p les demonstrate that a large proportion of the sam p le volum es collected was fog water. Bulk precip ita tion and f og samples were colle cted f o r field pH m e asurem ents and laboratory analysis for N and S on a weekly basis. Sam p les were shippe d overnight to the Forest Fire Laboratory in Riverside, CA for analysis. Nitrate and ammonium in bulk deposition and fog sa m p les were

m easured with the TRAACS 800 Autoanalyzer a nd sulfate was determ ined with a Dionex ion
chrom a tograph. The pH of fog and bulk depositi on sam p les was determ ined with a portable pH

m e ter in the field. Sam p l e pH was also m easur ed in the lab af ter shipp i ng the sam p les to

4Riverside, CA but lab pH values were consiste ntly higher than field pH values. The field pH
values are considered to be m o re reflective of sample pH and thus the lab pH values are not reported.
At Horsethief State Park (HTSP) an NADP we t deposition collector was also installed for

com p arison of wet deposition fluxes to bulk deposition fluxes m easur ed with the bu lk precipitation collectors. The latt er includes a sm all com ponent of dry and fog deposition that
collects on the collecto r funnels in b e tween precipitation events because the funnel is constan tly exposed to the atm o sphere.



### Results

Throughfall: Deposition of N and S i n throughfall under pine trees was highest at Seven Mile Hill (7MH) with throughfall deposition o f 25.4 kg N/ ha and 6.5 kg S/ha. Deposition of NH 4 + and NO 3 - were of
sim ilar m a gnitude at 7MH. At sites to the west of 7MH NO 3 - deposition in throughfall was generally greater than N H 4 + deposition. At sites east of 7MH, NH 4 + deposition in throughfall was greater th an NO 3 - deposition (Fig. 2). Deposition of NH 4 + in throughfall was greater in the sites located to the east of 7MH (average of 8.01 kg N/ha) com p ared to sites west of 7MH (average of 2.76 kg N/ha; Table 3). The east:west ratios of throughfall depos ition inputs were 1.16, 2.90 and 1.36 for NO 3 - , NH 4 +

, and SO 4 2-

. Nitrate deposition in thro ughfall was higher than SO 4 2- deposition at all nine sites. Only at
CCH was SO 4 2- deposition sim ilar to NO 3 - deposition (Fig. 2). Average values for NO 3 - deposition were genera lly higher than NH 4 + deposition except at two of the three m o st eas t erly sites (HTSP and Celilo ). These ar e also the two sites with the lowest elevation. Deposition of
NH 4 + and SO 4 2- in throu ghf all are h i ghly sim ilar at all si tes w e st of 7MH, but at 7MH and all the
sites eas t of 7MH NH 4 + deposition was 2-3 tim es higher than SO 4 2- deposition (Fig. 2).

Bulk Deposition: Spatial patterns of bulk deposition dif f

ered from t hose for throughfall. Bulk deposition is based prim arily on wet deposition with m i nim a l inputs from dry deposition and fog. In contras t to th e throughfall data, bulk deposition of NO 3 - , NH 4 + , and SO 4 2- were all higher on average at the sites
to the wes t o f 7MH compared to the eastern sites (Fig. 2). W h ile N and S deposition in throughfall was by far the highest at 7MH, bulk depos ition of the three ions at 7MH were sim ilar to the average bulk deposition fluxes at the west ern sites and higher than the eas tern s ites (Fig. 2). Another contrast with the throughf all data is that for throughfall, NH 4 + deposition tended to be higher than the other ions in the ea stern sites, while in bulk deposition NO 3 - was consisten tly higher than NH 4 + or SO 4 2- deposition in the eastern sites, suggesting that N H 3 was pred om inantly deposited in fog and possibly as dry deposition.

Fog Deposition: Although the passive fog collector s were not designed to preven t the collection of wind-blown precipitation from the side, the f og collectors seem to have samp led m o stly fog, as evidenced by
the low volu m es and the much greater chem ical c oncentr ation s of the f og colle ctor sa mples

com p ared to the bulk deposition samples (Fig. 3). However, at MZ and 7MH the high volum es in the fog collectors on m a ny dates (and low ionic c oncentrations in fog at MZ) suggest that at

5these two sites wind blown precipitation was co llected in the fog co llectors along with fog

sam p les. At Klickitat (KLICK) a nd Celilo liquid sam p les were only co lle cted in the f og sam p lers

on one sam p ling date. This result, along with the low fog volum es relative to prec ipitation
volum es and high ionic concentrations in the fog collector samples, sugge st that contam ination of fog sa m p l e s by rain or snow was probably m i nor in sites other than MZ and 7MH. Ionic
concentratio ns were very high in th e two sam p les f r om KLICK and Celilo , but the vo lum e collected at KLICK was very low (< 10 m l ).

Deposition Acidity : The pH of fog and precipitation va ried tem porally at all the study sites. O n a few occasions pH values were greater than or equal to 5.7, particularly near the beginning of the study in
Nove m b er or early December 2003. The m o st acidic sam p les were collected at W I in January
2004. Howe ver, the fog sam p les at 7MH were the m o st consistently acidic, with fog pH values ranging fro m 3.8 to 5.0 from early Decem ber 2003 through March 2004. On 9 of 12 sam p ling dates during this period, fog pH at 7MH was less than 4.5. Bulk precipitation at 7MH did not go below pH 4.5. Precipitation or fog pH values of 4.5 or lower occu rred at KLICK (4 dates), HTSP (2 dates ) , Ce lilo (3 dates) , W I (3 date s, all as f og), and Maryh ill (MH; 2 d a tes, as f og and bulk precipitation). At MZ the pH of the bulk fog and bulk deposition sam p les were usually between 5.0 and 6.0 except for five dates when the pH of fog sa m p les was between 4.5 and 5.0 and once when fog pH was 6.4-6.6. A sim ilar tem poral trend of lower pH values during the latter part of the study was also observed at KL ICK, HTSP, Celilo, W I and MH. The pH of bulk precipitation at Klickitat ranged f r om 4.1-5.4 co m p ared to a range of 4.6 to 5.8 at HTSP. Fog volumes were very low at HTSP so pH was only m e asured on two dates. In both instances, fog pH was slightly higher than bulk precipitation pH (Fig. 4). The pH of bulk precipitation at Celilo ranged from 4.2-6.3. At WI the pH of bulk precipitation ranged from 4.7- 6.4 and the pH of fog ranged from 3.7-6.7. On three sam p lin g dates in Decem ber and January fog pH values at W I were between 3.7 and 4.5 (Fig. 4). At MH bulk precipitation pH was 4.7-
6.4. On the three dates w h en fog sa mples were co llected at MH, fog pH varied widely with average values of 6.7, 4.4 and 5.6. Fog pH at MH was generally higher than the pH of bulk precipitation (Fig. 4). At MZ, 7MH and W I fog sam p les were usually more acidic than bul k precipitation, although
in som e cases pH was sim ilar or less acidic in fog. On the 1-3 dates when field pH was m easured
in f og at HTSP, Celilo a nd MH f og was less ac idic than bu lk precip ita tion (Fig. 4).



### Discussion

This was a short term study, covering only the m a jor wet season from late October 2003 to early March 2004, a period of slightly over four m onths. The first stor m of the wet season occurred
before sam p ling began in late October 2003. In the CRG Nat i onal Scenic Area 4-5% of the annual precipitation occurred in October, before we began sampling. Thus, we did not sam p le
the in itial r a in events of the new wate r year. The s e f i rst r a in e v ents of ten e n tail the h i g h est deposition fluxes in th ro ughfall as p o llutants th at accum u late on plant canopies durin g the dry
summer are washed off. For exam ple, at the Ho od River and The Dalles m e teorological stations, respectively, only 1.42 and 0.23 cm of precipitation were recorded from J une through Septem ber 2003. This long dry period preced in g the October rain events, suggests th at these first rain ev ents that were no t sam p led may have contained hi gh er levels of accum u lated N and S compounds

6than in subsequent rain events with much s horter antecedent dry peri ods. Based on the high NH 4 + deposition fluxes in this study, dry deposition in the summ er would presum ably result largely
fro m N H 3 em issions from agriculture and other s ources. In summary, the deposition fluxes in throughfall would likely have been significantly higher if throughfall sampling had begun in early Oc tob e r. This con c lusion assu m e s that dry deposition is an im portant atm o spheric deposition com ponent in the CRG.
The sam p ling period of this study included the m a jor wet season, so it is expected that we

m easured the m a jor inputs from fog and wet dep o sition. Th roughfall dep o sition inputs reported in this study are considered to be low e r than annual throughfall fluxes si nce we only sampled for
4.5 m onths. For the 2004 water year (Oct 2003 to Septem ber 2004) 69-74% of the annual precipitation occurred during th e m o nitoring period of this study (Table 3), based on precip itation data from Hood River and The Dall es (http://ipp c 2.orst.edu /cgi-bin /ddm odel.pl). Although, the throughfall fluxes were relatively high in the CRG during this 4.5 m onth study, annual inputs to forested areas from fog, wet a nd dry deposition of N and S are expected to be much higher.

Levels of Atmospheric Inputs in the CRG:
At m o spheric deposition inputs of N in throughfal l were high under ponderosa pine trees in this study. Both oxidized and reduced form s of N we re im portant contributors to atm o spheric N deposition inputs based on throughfall NO 3 - and NH 4 + flux data. Nitrate was generally the m o re im portant ion at sites west of 7MH, while NH 4 + incre a sed in rela tive im portanc e at 7 M H and
sites further east. Elevated NO 3 - deposition is typical of areas exposed to em issions from fossil fuels, generally from transportati on and industrial sources. Elevated NH 4 + deposition generally reflects agricultural sources, su ch as confined anim al feed ing operations, although em issions
from the transportation sector, sewage a nd industrial sources can also contribute.

Throughfall fluxes reported in th is study represent deposition inputs under ponderosa pine trees. Deposition to open or canopy-free areas will be lower because tree canopies serve as collection surfaces for deposition in fog and dry deposition

. Thus, deposition ov er the larg er lan d scape will depend larg ely on the extent of can opy cover. N itrogen deposition inp u ts in th roug hfall at 7M H (25.4 kg N/ha) were the highest report ed in this study. It is widely reported in the literature that at these levels of deposition significant im pacts on nutrient cycling and on plant, soil and aquatic
chem istry can be expected (Fenn et al., 2003). Co mmonly observed effects include increased site
N status observed as reduced C:N ratio of the m i neral soil and orga nic layer, and in creased folia r N, soil acidification, N cycling and N m obilizati on. Nitrogen is m obilized and exported from the
site as leach ed nitrate an d gase ous em issions of N from soil. The key process m e diating these
effects is increased n i trification in so il. On the watershed level, elevated NO 3 - concentrations in

stream water are comm only observed.

Spatial Trends in Deposition: Inputs of NO 3 - , NH 4 + a nd SO4 in bulk deposition were hi gher in the sites west of 7MH,

presum ably because of h i gher precip i tation am ounts in th e western end of the CRG. Bulk deposition is com posed of wet deposition plus a m i nor com p onent of dry deposition that occurs to the funnel collectors between precipitation events . Thus, it is to be e xpected that in sites further west with higher precip itation will show h i gher bu lk d e position levels, even th ough bulk deposition inputs were low at all the sites com p a r ed to throughfall inputs. These patterns

7dem onstrate the greater importance of atm o spheric inputs of N and S in fog and as dry deposition
to forested areas com p ared to deposition in precipitation.

Several factors lead to g r eater atm o spheric d e position in fog or in dry form com p ared to deposition in rain or snowfall. Firs t of all, ionic concentr ations in rain or snow are typically very low, while ionic concentrations are m a ny- fold hi gher in fogwater or cl oudwater. Dry deposition of pollutants to forest canopies or to other surfaces is a m a jor de position pathway because this is a chronic and continuous deposit ion process during precipitati on-free periods. Dry-deposited N
and S com p ounds accu mulate on forest canopies until a precipitation ev ent, at which tim e a flush
of com pounds are washed from the canopy as thr oughfall dep o sition to th e forest floo r. Thus, throughfall deposition p r ovides an es tim ate of dry and fog deposition.

Higher concentrations of NH 4 + deposition in throughfall at 7MH at sites east of there suggests that higher levels of NH 4 + in fog and/or dry deposition o ccurred in the m o re eas terly sites

com p ared to the m o re westerly sites of the Scenic Area durin g the m onitoring period. Nitrogen
concentratio ns in tissue of the lichen Xanthoparmelia cumberlandia were also higher in the eastern end of the Gorge com p ared to western s i tes (Linda G e iser, p e rson al comm uni cation ) . The most likely ammonia em issions sources for th e CRG Sceni c Area inclu d e the large feedlot surrounding the Boardman power plan t, crop fertilization, a f e rtilizer plant along the river in the Tri Cities area, and power plant em issions.

Nitrogen versus Sulfur Deposition: In throughfall in the sites west of 7MH, nitrat e concentrations were higher than amm o nium or sulfate concentrations a nd ammonium concentrations tended to be slightly greater than sulfate
concentrations. This reflects the em issions profile of the urban source area (greater Portland) that
is the m a jor influence on the western end of th e gorge. High levels of NOx are expected because
of e m issions from the largely urban transportatio n sector. At 7MH and in sites east of 7MH, the throughfall deposition pattern was generally NH 4 + > NO 3 - > SO 4 2- , which is ref l e c tiv e of the greater ag ricultural em issions near th e eastern en d of the CRG.

Acidic Depo sition Ef f

ects on Cultura l and Natur a l Resources : Precip ita tion in equilibr i um with CO 2 has a pH of 5.65, slightly acidic because of the weak
carbonic acid for m ed by the dissolution of CO 2 in water. A pH value of precipitation of 5.65 can
can thus be used as a benchm ark in evaluati ng the extent to which air pollutants m a y be increasing the acidity of pr ecipitation or fogwater.

The finding of fog or bulk precipitation sam p les with a pH of 4.5 or lower on m o re than one

sam p ling date at all six of the m onitoring sites east of MZ demons trates that acidic deposition is occurring throughout the CRG Na tional Scenic Area. The pH of fog or bulk precipitation

sam p les were never below 4.5 at MZ. More extrem el y acidic events, here defined as pH less than 4.0 occurred on three sampling date s at 7MH and once at WI and MH. However, m o re sam p ling dates with unusually low pH valu es m a y have been found if the f og collectors had the capacity to reliably exclude wind-blown precip itation and collect only fogwater.

The detrim e n tal effects of acidic deposition on ro ck buildings and stone monum e nts of certain rock types (e.g., m a rble) is well known. Howeve r, the rock art in the CRG National Scenic Area is largely on basalt or other ro ck types of volcanic origin. The le ve l of acidity in the p r ecip ita tion

8and fog sa mples collected in this study suggest s that the potential for increased risk of
deterioration of cultural resources such as rock paintings should be investigated. Dam a ge to stone from a c id deposition is a com p lex proce ss that depends on m a ny f actors, and we cannot assess or predict the level of dam a ge to rock art in the Gorge from the available inform ation.
Previous research has found m i nim a l stone degrada tion in the arid southwestern U.S. However, studies have found that dry deposition of S and N com pounds is the m a in source of stone
deterioration. Nonetheless in areas where stone materials rem a in wet for long periods of tim e, wet deposition can be a significant or prim ar y cause of da m a ge (Charola, 2001; NAPAP, 1998).
Futherm o re, lichen g r owth can af f

ect the in tegr ity of petroglyphs (Dr. Ron Dorn, Arizona State University, personal communicatio n). It is well docum ented th at atm o spheric deposition has
caused chan ges in lichen communitie s and the e l e m ental composition of lichens in the CRG
National Sc enic Area. T h is ra ises qu estions in r e gard to indirect effects of N deposition on rock art by way of changes in lichen comm unites colonizing the rock art.

Possible Ecological Effects of N itrogen and Sulfur Deposition:
Two m a in types of ecological eff ects are of concern from the depos ition levels indicated by this study. Increased soil acidification is one res pons e to chron i c N and S deposition. Eu trophication
or N enrich m e nt effects is the o t her m a jor categ ory of ecosystem effects, and is in fac t the m o st common response in W e stern forests (Fenn et al., 2003). Air pollution im pacts on lichen
communitie s in the CR G, attr ibuted to N deposition a r e well docum ented. Lichen co mmunities
in m a ny areas of the CRG have shifted to a hi gher proportion of nitrophi lous species and the N content of lichen tissue is elevated (F enn et al., 2 003). Recent studies sho w that the N content of
the lichen X anthoparmelia cumberlandia is significantly higher in the eas tern end of th e Gorge

com p ared to the western end. These findings ag ree with the th roughfall data in this study. Throughfall is a good in dicato r of to tal N and S deposition b ecause it in cludes deposition from dry deposition, fog deposition and wet depos itio n. Th e throu ghfall data also sugges t that over half of the N deposition is in reduced for m , sugge sting an agricultural or industrial source in the eastern end of the gorge.
Lichens are sensitive ind i cato r s of N depositi on effects to terrestrial ecosy tem s , andt the
lichen studies in the CR G clearly show that eco logical effects from ai r pollution are occurring. Lichen studies in the western U.S. sugge st that N deposition as low as 3-5 kg ha -1 yr -1 can cause signif i cam t changes in lichen chem istry and lic he n communities. However, based on pr evious
studies in western North Am eri ca (F enn et al., 2003) and consid ering the throughfall deposition levels in the CRG, it is likely that other less sensitive ecosystem com pone nts and processes are also being impacted. Chronic N deposition of 10-25 kg N/ha/yr as repo rte d in this stu dy is with in the rang e at which N fertilization typ e responses are expected , leading to increas ed N levels in soil, plants, and in soil leachate and runo ff. Nitrogen cycling increases an d the key N
mobiliza tion process of n itr if ication increas es, l e a d ing to nitra t e le aching losses f r om the f o rest. This syndro m e of ecosystem responses to N dep o sition is often referred to as N saturation. Soil acidification is caused by both N and S deposition as a gradual process. Increased nitrification rates, as described a bove, also results in soil acidif ication. As nitrate and sulfate is
leached fro m soil, coun ter-b alan cin g base catio n leach ing losses also in creas e, furth e r leading to
soil acidification. The risk to the ecosystem from soil acidific ation depends on the inherent
buf f

e ring capacity of the soil. Mos t s o ils in western sem i -arid ecosystem s are well buffered

com p ared to m e sic forests. Thus, N enrichm e nt effects are m o re comm on concerns in western forests exposed to chronic atm o spheric depositio n inputs. Further studies m a y be needed to

ascer tain the risk of soil acidif i c a ti on or depletion of base cations f r om f

o rested s ite s in the CRG.

9

### Literature Cited

Charola, E.A. 2001. Ac idic deposition on stone. US/ICOMOS Scientific Journal 3:19-58. Fenn, M.E., Baron, J.S., Allen, E.B., Rueth, H.M ., Nydick, K.R., Geiser, L., Bowm an, W

. D.,
Sickm a n, J.O., Meixner, T., Johnson, D.W ., a nd Neitlich, P. 2003. Ecol ogical effects of nitrogen deposition in the wester n U n ited States. BioScience 53:411-420. Fenn, M.E., and Poth, M

. A. 2004. Monitoring nitrogen depos ition in th ro ughfall usin g ion exchange resin colum n s: A field test in th e San B e rnardino Mountains. J. Environ. Qual.
33:2007-2014. Fenn, M.E., Poth, M.A., Schilling, S.L., a nd Grainger, D.B. 2000. Throughfall and fog deposition of nitrogen and sulfur at an N-lim ite d and N-saturated site in the San Bernardino Mountains, southern California. Canadian Journal of Forest Research 30:1476-1488. Geiser, L., and Neitlich, P. 2003. Air quality gradients in western Oregon and W a shington
indica ted by lichen communities an d chem ical analysis of lic h en tissu e. www. fs.fed. u s/r6/aq NAPAP Biennial Report to Congress: An Integr ated Assessment. Natio nal Acid Precipitation
Assessm ent Program . 1998. National Science and Technology Council, Committee on
Environm ent and Natural Resour ces. Silver Spring, Maryland.
Sim k in, S.M ., Lewis, D.N., W eathers, K.C., Lo vett, G.M., and Schwarz, K. 2004. De term ination of sulfate, nitrate, and chlori de in throughfall using ion-excha nge resins. Water, Air, and Soil
Pollut. 153: 343-354.

10Table 2. Precipitation amounts at weather sta tio ns and at deposition m onitoring sites in the
Colum b ia River Gorge §

.

Precip ita tion (cm ; % of total in paren t heses )

Dates Bonneville Da m Hood River The Dalles

10/1/03 to 10/28/03 (before collection) 12.75 (7.3) 2.79 (4.9) 1.57 (4.6)
10/29/03 to 3/9/04 (during collection) 110.39 (62.8) 39.67 (69.2) 25.25 (73.7)
3/10/04 to 9/30/04 (after collection) 52.68 (29.9) 14.91 (26.0) 7.44 (21.7)
2004 W a ter Year (Oct. 1, 2003 to Sept. 30, 2004) 175.82 57.38 34.26

D e p o s i t i o n S t u d y S i t e s M Z K l i c k 7 M H H T S P W I C e l i l o M H
10/29/03 to 3 / 9 / 0 4 9 5

. 2 3 2 8

. 9 5 2 8

. 1 7 2 2

. 0 3 2 2

. 1 6 1 8

. 0 8 2 0

. 3 6

§ Precip i tatio n data f r om the In tegra t e d Plant Protection Center – De gree Day Calculator ( http://ippc2.orst.edu /cgi-bin/ddm odel.pl ). Locations of the weathe r statio ns are as follows:
Bonneville Da m : Bureau of Reclamation Agrimet
Bonneville Da m , WA – BNDW
Latitud e : 45 ° 38’ Longitude: 121° 55’ Elevation: 24m

Hood River: Bureau of Reclam ation Agrim e t station Hood River Experim e ntal Station Oregon -- HOXO
Latitud e : 45 ° 41’ Longitude: 121° 31’ Elevation: 174m

The Dalles: KDLS ME TAR Station The Dalles Municipal A i rport, WA
Latitud e : 45 ° 38’ Longitude: 121° 10’ Elevation: 7 4 m

11Table 3. Comparison of nitrogen and sulfur deposition (kg/ha) in throughfall and bulk deposition at eastern versus western sites in th e Colum b ia River Gorge §

.

Ion W e stern Sites Eastern Sites East:W est Ratio

T h r o u g h f a l l D e p o s i t i o n NO 3 - N 5

. 1 1 5

. 9 4 1

. 1 6
NH 4 - N 2

. 7 6 8

. 0 1 2

. 9 0
SO 4 - S 2

. 1 8 2

. 9 7 1

. 3 6

§ W e stern sites include T w in Tunnels high and lo w elevation and Catherine Creek high and low
elevation s i tes. Eastern s ites includ e Horsethi ef S t ate Park, W i shram (bulk deposition only), Celilo and Maryhill s i tes. The Seve n Mile Hill s ite was no t included in these west- t o

- east

com p arisons because this site is high er in elev atio n and m o re exposed to fog depositio n than the
other sites and because this si te is lo cated app r o x im ately m i dpoint between the western and
eastern sites. Data from t h e Mt. Zion site are no t included eith er, becau se this is an extrem ely western site and strongly infl uenced by the Portland urban pollu tion p l um e. The Klickitat site
was also excluded from t h e east/west com p arison because it is located within a separate side drainage north of the m a in gorge and m a y not be exposed to the prinicipal air m a sses com i ng through the gorge to the sam e ex tent as the other sites.

12Fig. 1. Map showing the location of the atmospheric deposition monitoringsites in theGorge.13Fig. 1 continued.14

### Throughfall Deposition

T

T

H T T

L CCH C CL 7 M

H K L

I CK HT S

P C E

L

I L

O M Hkg/ha

0 2 4 6 8 10 12 14 16 18



### Bulk Deposition

M

Z

NA D

P M Z

T

T

H I E

R
T

T

L

I E

R CC H

I E

R CC L

I E

R 7 M

H K L

I CK

HT S

P

NA DP H T

S

P W I CE L

I L

O M Hkg/ha

0. 0 0. 2 0. 4 0. 6 0. 8 1. 0 1. 2 1. 4 1. 6 1. 8

NO 3 -N k g /ha

NH 4 -N k g /ha

SO 4 - S kg /h a

Fig. 2. Throughfall and bulk de position fluxes during the 19 week m onitoring period (October 2003 to March 2004). All throughfall sam p les we re determ ined with ion exchange resin (IER) collectors and bulk depositi on IER collectors were used for bulk deposition at the Tw in Tunnels
and Catherine Creek sites.

15Nov Dec Jan Feb Mar A p r 0 200 400 600 800 1000 1200

7MH

X Data 0 5 10 15 20

Nov Dec Jan Feb Mar A p r 0 200 400 600 800 1000 1200 B u lk Vo lum e Fo g V o l u me Kl icki tat

0 5 10 15 20

Bul k N O 3 -N Fog N O 3 -N
Bul k S O 4 -S Fog SO 4 -S

Bul k N H 4 -N Fog N H 4 -N Mt. Z i onConcentraion (mg/L)

0 5 10 15 20

Nov Dec Jan Feb Mar Ap rVolume (ml)

0 20 0 40 0 60 0 80 0 100 0 120 0

HTSP

0 5 10 15 20

Nov Dec Jan Feb Mar Ap r 0 200 400 600 800 1000 1200mraion (entConcg/L)Volume (ml)

Fig. 3. Concentrations of nitr ate, su lfate and am monium in bulk deposition and fog sam p les.

16Celi lo

0 5 10 15 20

Bulk NO 3 -N Fo g NO 3 -N Bulk SO 4 -S Fo g SO 4 -S Bulk NH 4 -N Fo g NH 4 -N

No v Dec Jan Feb M a r Apr 0 20 0 40 0 60 0 80 0 100 0 120 0

Bulk Volum e Fo g V o lu m e

Mar y hill

0 5 10 15 20

Nov D e c Ja n Feb Mar Ap r 0 200 400 600 800 1 000 1 200 Wishram

0 5 10 15 20

Nov De c Jan Feb Ma r A p r 0 20 0 40 0 60 0 80 0 10 00 12 00

Fig. 3. Continued.Concentraion(mg/L)Volume (ml)Volume (ml))g/Lon (mntraieConc

177MH pH

No v De c Jan Feb M a r A p rpH

3 4 5 6 7

Kl ick i t a t pH

N o v De c Ja n Fe b M a rpH

3 4 5 6 7 MZ p H

N o v De c Ja n Fe b M a r A p rpH

3 4 5 6 7

Bulk Field pH
F og F i e l d p H
NADP Fi eld p H HT SP pH

No v De c Jan Feb M a r A p rpH

3 4 5 6 7

Fig. 4. The pH of fog or bulk precipitation sam p les. At Horsethief State Park (HTSP), an NADP style wet deposition collector wa s used and pH data is also shown for the NADP sa m p ler.

18