A comparison of phosphorus retention in lakes determined from mass balance and sediment core calculations

46 Pages·1992·3.2 MB·English

by  Dillon, P. J. (Peter James), 1942-

PRDahE eNtE t!h AeSE S2E

A COMPARISON OF
PHOSPHORUS RETENTION
IN LAKES
DETERMINED FROM MASS BALANCE
AND
SEDIMENT CORE CALCULATIONS
JULY 1992
wr”
7 Environment
Environnement
Ontario

ISBN 0-7729-9749-7
A COMPARISON OF PHOSPHORUS RETENTION IN LAKES
DETERMINED FROM MASS BALANCE
AND SEDIMENT CORE CALCULATIONS
Report Prepared By:
P.J Dillon
Ontario Ministry of the Environment
Water Resources Branch
P.O. Box 39, Dorset, Ontario POA 1E0
and
H.E. Evans
RODA Environmental Research Limited
P.O. Box 447, Lakefield, Ontario KOL 2H0
JULY 1992
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Copyright: Queen’s Printer for Ontario, 1992
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Log 92-2345-099
PIBS 2050E

ABSTRACT
Phosphorus retention (TP,.) was determined in 7 lakes in Ontario, Canada from mass
balances and from the direct measurement of phosphorus accumulation in the sediments.
Phosphorus retentions determined using the mass balance technique ranged between 20
+ 3.9 and 94 + 23 mg/m’/yr and were slightly lower than those calculated by multiplying
sediment total phosphorus (TP) concentrations by sediment accumulation rates (49 + 14
to 135 + 48 mg/m?/yr). The lower TP,,. values measured using the mass balance
approach may result from the underestimation of external TP inputs. Alternatively, it is
suggested that in the more acidic lakes, a decrease in TP concentrations in the
lakewaters and/or a decrease in TP export from the catchment may have resulted in a
decrease in TP... through time. Thus, relatively higher TP. values calculated using the
sediment approach (since TP. values calculated from the sediment data are averaged
over a greater number of years than those calculated from the mass balance data).
Provided several cores are collected from the lake, the direct measurement of sediment
TP and sediment accumulation rates for estimating TP,,. may be a suitable alternative to
mass balances, especially in situations where it is not possible to measure all inputs of
TP to the lake.
Short title - phosphorus retention in lakes
Keywords - phosphorus, retention, sedimentation, mass balance, cores
TABLE OF CONTENTS
Abstract. Sse SIMCA JE AR ER ER Bs CPR RSR RE SERRES i
Tableiof: Contents 40108 RECU SMART. SD. St ER PER eee ii
Listiof Bablesyes: 95840 Pe SE A DOE, Ea ails ee eh FREE iii
BistiofiPigures' 2: 400/52 Qa eGR SAAS) CRRA Bites PE RAI ca ce oes MERE iv
Introduction™../.3 5.0.8 Jon Re ES AO ETAT CEE nec io eters Re Tee 1
StudyiAreay: 24-2008. CARRE ES AE SOL ST. ATS ee ee ee eee 3
Methods/£c tattoo NES 10 a LE SRE: See) See err 4
Retention Measured Using Sediment Cores
a) Corescollectionfand tréatment 2am. 4. Se BARON S22 Ss eee 2
b) Analysis of sediment phosphorus concentration ................... 5
che 7° Pbianalyses and dating mouse SEATPORN. S.OR.. Se e 5
d) Measurement of stable Pb concentrations and whole-lake anthropogenic Pb
burdens ..2:5 35.5 RS Heese cree eis ne denisCRE ER 6
e) Calculation ofsediment: TR. retention 7529000 25.0ER0 28ee e 7
Mass Balance Calculations
a) Hydrologic budgets: 2x2... 5:2 c/o. 5. 20 seroistexs CPR 7
b) StreamSampling’ os. 5 rome mens es ice ee CCR 8
c) Precipitation:samplin® =. m0 28e sete a eee: CCE 8
d) Analysis of TP in precipitation and streamwater ................... 9
e) Phosphorus mass balance calculations... 5.6... + ss. sem ole ee 9
f) Calculation of TP retention by mass’ balance! teen ser .- .... - aelneee 10
RESINS). 52. esac ee SiS ce a's hw ec Py ee eer Th wees NN eS 10
DISCUSSION 5 4.52 25.8 Wo see nes nee nee ater tee OR RC ae 11
Acknowledgements::. 2 Scie, peels Seem tow clst oon CR neso yl ene oye RER eee 16
REfCrEnCes aie hc.2 ;5 % cx eee AeA ERI Lee Le ee a RET ee lee a eh eee 17
LIST OF TABLES
Table 1 Locations, morphometric characteristics and anthropogenic whole-lake Pb
burdens (Pb burden (wy) for each of the study lakes. A,= lake area, z =
mean depth, z,,,, = maximum depth
Table 2 Average surface (0-3 cm) concentrations of total phosphorus ([TP]),
sediment accumulation rates (SAR), anthropogenic Pb burdens at each site
(Pb burden,:.,), and TP retention (TP...) at each site calculated according
to equation (1).
Table 3 Total inputs of TP to each lake, output of TP from each lake and the net
retention (TP...) of TP by each lake.
acc
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LIST OF FIGURES
Fig. 1 Total phosphorus concentration in 5 sediment cores collected from Blue Chalk
Lake.
Fig. 2 Total phosphorus concentration in 5 sediment cores collected from Plastic Lake.