Suspended sediment phosphorus composition in tributaries of the Okanagan lakes, B.C.

Wat. Res. Vol. 20, No. 9, pp. 1193-1196, 1986 Printed in Great Britain

0043-1354/86 $3.00+0.00 Pergamon Journals Ltd

RESEARCH NOTE S U S P E N D E D SEDIMENT PHOSPHORUS COMPOSITION IN TRIBUTARIES OF THE O K A N A G A N LAKES, B.C. C. B. J. GRAY and R. A. KIRKLAND National Water Research Institute, Environment Canada, West Vancouver, B.C. V7V IN6, Canada (Received October 1985)

Abstract--The phosphorus composition of suspended sediments transported during snowmelt to the Okanagan lakes averaged 62% apatite P, 16% non-apatite inorganic P (NAIP), and 22% organic P. Based on the average NAIP content, less than 16% of these P inputs were available for algal growth in the lakes. The content of NAIP in some stream suspended sediments was much higher than average, however. Management of the suspended sediment inputs to reduce P loadings will be most effective if applied to those tributaries contributing the most NAIP. Key words--phosphorus, bioavailability, apatite, suspended sediments, eutrophication, Okanagan Valley

INTRODUCTION

Phosphorus (P) associated with suspended sediments in tributaries often represent a large portion of the total annual P loading to lakes (Sonzogni et al., 1982). Furthermore the sediment-transported P loading has been rising in many areas because of increased agriculture, forestry, and urban development (Vollenweider, 1968). However, the effect of suspended sediment P on eutrophication of lakes is often unknown because the bioavailability of this P is variable (Logan, 1982; Sonzogni et al., 1982). Suspended sediment P made up 75% of the P loading from tributaries entering the Okanagan lakes, which are experiencing accelerated eutrophication due to excess P loading (Stockner and Northcote, 1974). While tributary P loadings only represented 40% of the total loading in 1970, their relative importance has increased because sewage effluents are now tertiary-treated which decreases total P loading, and because agriculture and forestry activities are releasing more suspended sediment P than in 1970 (Okanagan Basin Implementation Board, 1982). Most of the suspended sediment originates in glaciolacustrine deposits (Fulton, 1969), which are eroded during snowmelt (May and June) and intense rainstorms. Deposits modified by agriculture and urban developments add suspended sediments to the tributaries in their lower reaches. To assess the impact of suspended sediment P loadings on the Okanagan lakes, their bioavailability must be known. This note reports results of analyses of suspended sediment samples from streams, representing the majority of the drainage basin, for three chemically defined phosphorus components, each having a different level of bioavailability. The three tom-

ponents are apatite P (AP), non-apatite inorganic P (NAIP), and organic P (OP). These components, as measured by the chemical extraction technique of Williams et al. (1976a), have been evaluated for their bioavailability to phytoplankton in some recent studies (Williams et al., 1980; Depinto et al., 1981). The phosphorus in mineral grains of apatite (AP) is considered biologically unavailable in lakes because the grains of apatite settle rapidly (Williams et aL, 1980 and Depinto et al., 1981) and the pore water of sediments is usually supersaturated with respect to apatite (Emerson, 1976). The non-apatite inorganic P (NAIP) is considered potentially available to phytoplankton although it can overestimate bioavailability in the short term by up to 30% (Williams et al., 1980 and Depinto et al., 1981). Organic P (OP) is also potentially available after hydrolysis to inorganic P by biological processes, but is not available during short term incubations (Williams et al., 1980) unless the OP originates from fresh plant tissue or animal wastes (Sonzogni et al., 1982). N A I P is usually larger than the fraction extractable with 0.1 N NaOH which corresponds most directly to biologically available P in short incubations (Williams et al., 1980). However, in a lake there may be more time to fully utilize the N A I P and some of the OP, especially if the biogeochemical processes in bottom sediments are suitable for P release (Bostrom et al., 1982). METHODS

Suspended sediments were obtained from the outlets of 1! streams, which enter the Okanagan lakes or the interconnecting river, and from 6 sites at higher elevations within two sub-basins. All samples were collected, in May 1981, using a continuous flow centrifuge (Ongley and Blachford,

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Research Note Table I. TP, AP, NAIP and OP in suspended sediment from streams in the Olanagan Valley (,ugg ~dry wt) Sample*

TP

AP(%)

NAIP(%)

OP(%)

3470 1200 1130 1400 1480 1055 1475 1250 1320 1610 1090

270 (7) 800 (66) 890 (78) 660 (47) 950(64) 560 (53) 1020(69) 790(63) 1340(102) 680 (42) 805 (73)

1630 (48) 1l0 (10) 50 (5) 275 (19) 260(18) 255 (24) 200(19) 195(16) -385 (24) 120 (12)

1570 (45) 285 (24) 190 (I 7) 470 (34) 240(18) 240 (23) 180(12) 265(21) -550 (34) 165 (15)

(i) Shingle Creek drainage basin Shingle No. 2 Shatford

1310 1785

870(66) 930 (52)

280(21) 360 (21)

170(13) 490 (27)

(ii) Vaseux Creek drainage basin Middle Vaseux Upper Vaseux Wabash Underdown

I 160 1120 1695 1970

820 (70) 550 (49) 285 (16) 225 (11 )

140 (I 3) 140 (13) 315 (19) 565 (29)

200 (17) 430 (38) 1095 (65) 1t80 (60)

Stream outlet sites

Deep Equesis Coldstream Vernon above Ellison L. Vernon above Wood L. Vernon above Okanagan L. Mission Lambly Trout Shingle Vaseux High elevation sites

*See Gray and Kirkland (1982) for exact dates and location. Numbers in brackets indicate % of TP.

1982). After being frozen in the field, samples were freezedried, and sieved to retain the < 64 #m size fraction (silt and clay). Samples were serially extracted with a dithionitecitrate-bicarbonate solution (0.14, 0.22 and 0.11 M, respectively), 1 N NaOH, and finally with 1 N HC1 to obtain the AP content. Total P (TP) and total inorganic P (TIP) were analyzed in 1 N HC1 extracts of roasted (550°C, 2 h) and unroasted subsamples, respectively. NAIP was the difference between TIP and AP while OP was the difference between TP and TIP. Duplicate samples were extracted, and each solution was measured twice by Technicon Autoanalyzer. The four values were than averaged (Table 1). Analysis of a lake sediment sample yielded a precision of 5% for AP and 10% for TP and TIP. This fractionation scheme was the same as that used by Williams et al. (1976a) except that AP was extraced in 1 N instead of 0.5 N HCI and all HCI extractions were done twice. RESULTS

Most of the stream outlet samples had similar phosphorus concentrations and composition (Table 1). However, both Deep and Trout creek samples had quite dissimilar compositions from the majority and will be treated separately. The remaining outlets had average values in #g g-~ dry wt of 1300 TP, 800 AP, 210NAIP, and 290OP. The relative proportions were 62% AP, 16% NAIP, and 22% OP. DISCUSSION

The suspended sediments analyzed in this study were representative of the high flow period resulting from the snow melt. Because the majority of the sediment loading occurs during this hydrological event (Technical Supplement IV, 1974), the average P composition of the annual sediment yield from each creek will not be very different from these analyses. The P composition of most samples was indicative of a very low P bioavailability. NAIP content ranged

between 5 and 24% except for the Deep and Trout Creek samples. OP content, which could add marginally to the bioavailability, was slightly higher, ranging between 12 and 34%. From 42 to 78% of the P was not bioavailable because of the low solubility of the primary phosphate mineral apatite (Williams et aL, 1980). Among the 9 stream outlet samples included in the above discussion, there was no obvious relationship between relative composition and land use. For example, the drainage basin of the Vernon above Okanagan L. station includes some agriculture and the city of Vernon (population 25,000). Only AP was low compared to the average (560 vs 800#g g - l ) . Another example was Lambly Creek which had 20% of its forested land logged between 1970 and 1980 (Alexander and Wiens, 1982). The composition was very close to the average for the other creeks which were logged at a much lower intensity ( < 10%). Except for Deep and Trout Creeks, suspended sediment P loading from the tributaries during snowmelt was moderately rich in AP and poor in N A I P and OP regardless of the level of forestry, agriculture and urban activities seen in the Okanagan Valley. In Deep Creek, on the other hand, the TP content was the highest measured (3500#g g - l ) and was made up of equal portions of NAIP and OP, with a small amount of AP. Deep Creek traverses an area of intensive agriculture (including dairy farms) and there is a domestic sewage input 15 km above the sampling site. Agricultural runoff, sewage effluents, and organic particulates formed by incorporation of orthophosphate into biomass have enriched this sediment in N A I P and OP. The bioavailability of the OP in these materials is probably high (DePinto et al., 1980; Sonzogni et al., 1982) and thus the availability may equal the sum of NAIP plus OP, or 90% of TP. Trout Creek, however, had no detectable OP or

Research Note N A I P and therefore was completely unavailable. The major source of the AP-rich suspended sediments was a glaciolacustrine deposit slumping into the creek I km upstream. AP in glaciolacustrine deposits usually makes up 95% of the TP content (Williams et al., 1976b). The influence of AP-rich sediments was also seen at most sites upstream of the outlets. Only in two small first order tributaries of Vaseux Creek did this dominance decrease. OP was the largest component in Wabash and Underdown Creek samples. These creeks were not large enough to erode the glacial materials along their heavily forested banks. Also, the drainage basins of these two creeks were not disturbed by logging. In summary, the biological availability of the suspended P, transported during snowmelt was generally low in the outlets of the major streams entering the lakes in the Okanagan Valley. These data increase the known area in south-central British Columbia with low bioavailability of particulate P. Reid et al. (1980) reported that more than 70% of the total P loading to Kamloops Lake was AP. Kamloops Lake lies within the interconnected valley system, and is about 100 km northwest of the Okanagan Valley. In the two major rivers entering Kootenay Lake 200 km to the east of the Okanagan Valley, AP was 80% of the suspended sediment P during the early high flow period (Daley et al., 1981). The source of suspended sediments throughout these regions during high runoff periods is glaciolacustrine sediments. Thus, only at those sites where agricultural, industrial and/or municipal inputs are large does the % AP decrease due to inputs of materials rich in N A I P and OP. The Great Lakes region provides an example of this increase in N A I P and OP relative to AP after large-scale agricultural and urban development. While glaciolacustrine deposits are common throughout the region (Sly and Thomas, 1974), N A I P content of suspended sediment in tributaries is generally between 30-40% (PLUARG, 1978; Logan et al., 1979; DePinto et al., 1981). OP content is variable but usually higher than AP (Logan et al., 1979). The effect of low P bioavailability in suspended sediments on management plans to control P loading to the Okanagen Valley lakes will be considerable. Planners should consider both TP loadings and compositional information to determine which areas ar~ contributing large amounts of biologically available P. For example, Trout Creek supplied about 16% of the suspended sediment loading from tributaries to Okanagan Lake in 1970 (Technical Supplement IV, 1974) and suspended sediment control was recommended to reduce the loading of P. From our analysis however, the suspended sediments from this creek can be ignored as a significant factor in the eutrophication of Okanagan Lake. On the other hand, Deep Creek supplied about 8% of the lake's suspended sediment P and approx. 90% of this TP is potentially W.R. 20/9~1

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available. Land management practices which minimize the input of N A I P and OP could be employed in the Deep Creek drainage basin to great effect while similar efforts in the Trout Creek drainage basin would produce no reduction in biologically available P loading. The effect of curtailing suspended sediment inputs in most other Okanagan streams would be more beneficial than in Trout Creek. However, the average maximum reduction of biologically available P would be less than 16% in the other creeks. Acknowledgements--We wish to thank the Okanagan Basin

Implementation Board and members of the Diffuse Source Loading Update Committee for support of this work, in particular, G. Alexander. Technical assistance from V. Chamberlain, G. Oliphant and K. Suzuki is greatly appreciated. Dr E. Ongley and D. Blachford of Envirodata Ltd provided and operated the suspended sediment collection apparatus. We thank Dr C. Pharo for his editorial comments. REFERENCES Alexander D. G. and Wiens J. H. (1982) An estimate of phosphorus loadings from forestry activities in the Okanagan. Report MS. Terrestrial Studies Branch, Ministry of Environment, Victoria, B.C. Bostrom B., Jansson M. and Forsberg C. 0982) Phosphorus release from lake sediments. Arch, Hydrobiol. Beih. Ergebn. Limnol. 15, 5-59. Daley R. L, Carmack E. C., Gray C. B. J., Pharo C. H., Jasper S. and Wiegand R. C. (1981) The effects of upstream impoundments on the limnology of Kootenay Lake, B.C. Scientific Series No. 117, National Water Research Institute, Inland Waters Directorate, Environment Canada, Vancouver, B,C. DePinto J. V., Young T. C. and Martini S. C. (1981) Algal-availablephosphorus in suspended sediments from lower Great Lakes tributaries. J. Great Lakes Res. 7, 311-325. DePinto J. V., Edzwald J. K., Switzenbaum M. S. and Young T. C. (1980) Phosphorus Removal In Lower Great Lakes Municipal Treatment Plants. U.S. EPA Report No. 600/2-80-177. Cincinnati, Ohio. Emmerson S. (1976) Early diagenesis in anaerobic lake sediments: chemical equilibria in interstitial waters. Geochim. cosmochim. Acta 40, 925-934. Fulton F. J. (1969) Glacial lake history, southern interior plateau, British Columbia Geological Survey Canada Paper 69-37. Ottawa, Ontario. Gray C, B. J. and Kirkland R. A. (1982) Nutrient composition and bioavailability in major tributaries and interconnecting rivers of the Okanagan Basin. Inland Waters Directorate Report, Pacific and Yukon Region, Vancouver, B.C. Logan T. J. (1982) Mechanisms for release of sedimentbound phosphate to water and the effects of agricultural land management on fluvial transport of particulate and dissolved phosphate. Hydrobiologia 92, 519-530. Logan T. J., Oloya T. O. and Yakisch S. M. (1979) Phosphorus characteristics and bioavailability of suspended sediments from streams draining into Lake Erie. J. Great Lakes Res. 5, 112-123. Okanagan Basin Implementation Board (1982) Report on the Okanagan Basin Implementation Agreement. Canada-British Columbia, Victoria B.C. Ongiey E. D. and Blachford D. P. (1982) Application of continuous flow centrifugation to contaminant analysis of suspended sediments in fluvial systems. Envir. Technol Lett 3, 219-228.

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Research Note

Pollution from Land Use Activities Reference Group (1978) Environmental management strategies for the Great Lakes. International Joint Commission, Windsor, Ontario. Reid R. P., Pharo C. H. and Barnes W. C. (1980) Direct determination of apatite in lake sediments. Can. J. Fish. Aquat. Sci. 37, 640--646. Sly P. G. and Thomas R. L. (1974) Review of geological research as it relates to an understanding of Great Lakes limnology. J. Fish. Res. Bd Can. 31, 795-825. Sonzogni W. C., Chapra S. C., Armstrong D. E. and Logan T. J. (1982) Bioavailabihty of phosphorus inputs to lakes. J. envir Qual. 11, 555--563. Stockner J. G. and Northcote T. G. (1974) Recent limnological studies of Okanagan Basin lakes and their contribution to comprehensive water resource planning. J. Fish Res. Bd Can. 31, 995-976.

Technical Supplement IV (1974) Water quality and waste loadings in the Okanagan Basin. Canada-British Columbia Okanagan Basin Agreement Report, Victoria, B.C Vollenweider R. A. (1968) Scientific fundamentals of the eutrophication of lakes and flowing waters, with particular reference to nitrogen and phosphorus as factors in eutrophication. Technical Report OECD, Paris. Williams J. D. H., Jaquet J. M. and Thomas R. L. (1976a) Forms of phosphorus in the surficial sediments of Lake Erie. J. Fish. Res. Bd Can. 33, 413-429. Williams J. D. H., Murphy T. P. and Mayer T. (1976b) Rates of accumulation of phosphorus forms in Lake Erie sediments. J. Fish. Res. Bd Can. 33, 430~39. Williams J. D. H., Shear H. and Thomas R. L. (1980) Availability to Scenedesmus quadricauda of different forms of phosphorus in sedimentary materials from the Great Lakes. Limnol. Oceanogr. 25, 1-11.