Freshwater SO 4 pH 2- Al 3+ Al 3+ Research Research O O 2 4 4 Ca 2+ 2 Nutrients PO 4 3- - S 2- - e 2+ + Fe Importance of sample timing, handling p p g g and other methods to low-level analysis of phosphorus in lake water p p Gertrud Nürnberg, Ph.D. Freshwater Research, Baysville, Ontario www.fwr.ca 1
Thank you y • Invitation by Session Chairs • Travel grant by NEMC T l t b NEMC Conference Coordinator, Jerry Parr of the NELAC Institute NELAC Institute Charlie Patton Charlie Patton 1. Reasons NOT to use low-level analysis 2 2. What may be more important instead What may be more important instead 2
Problems with low level analysis y – Contamination – Need a lot of replicates (high analytical effort) – Few comparative data from other studies/ systems available – High cost, effort, specialization, etc. “Trade off” – Transient “Snapshot”: not reproducible (high sampling effort) – example “Blooms” 3
• Urban, larger Metro Toronto area • Well-buffered, hardwater , • Area: 56 ha; Max Depth: 16 m • Dimictic kettle lake • Dimictic kettle lake • Meso- to eutrophic: summer TP 25 - 30 µg/L • Internal phosphorus load is 65% of total load I t l h h l d i 65% f t t l l d • Anoxic hypolimnion Urban Lake Wilcox Urban Lake Wilcox, Southern Ontario, 4 Canada
Cyanobacteria vs SRP (dissolved reactive P, detection limit 0.5 µg/L) ( , µg ) 5 R 2 = 0.25, p<0.0001, n=123
Cyanobacteria vs Ammonium Detection limit: 0 002 Detection limit: 0.002 – 0.005 mg/L 0 005 mg/L 6 R 2 = 0.22, p<0.0001, n=124
Cyanobacteria vs Nitrate&Nitrite Detection limit 0 005 mg/L Detection limit 0.005 mg/L 7 R 2 = 0.17, p<0.0001, n=181
Bluegreen algal bloom in Fanshawe Lake on August 26, 2005 8
Fanshawe Lake Nitrate and Chlorophyll Nitrate and Chlorophyll Nitrate Nitrate Chlorophyll Chlorophyll 14 160 140 12 120 e (mg/L) 10 (ug/L) 100 8 80 80 Nitrate 6 Chl 60 4 40 2 2 20 20 0 0 1988 1988 1989 1989 1990 1990 1991 1991 9
Bloom Indicator: Low-Nitrate-Days The period of time during summer and early fall, when p g y , nitrate concentration is below 1-2 mg/L 2 0 0 ays 1 5 0 ate-Da 1 0 0 1 0 0 w-Nitra 5 0 5 0 Low 0 1 9 6 5 1 9 7 5 1 9 8 5 1 9 9 5 2 0 0 5 Y E A R 10 Nürnberg 2007
The quest for adequate phosphorus measurements in lakes Wh t i th What is the analysis for? l i f ? • Assessment for nutrients by routine • Assessment for nutrients by routine monitoring, trophic state definition (Country, State, County) ( y, , y) • Remediation of eutrophication problems (Specific lake or watershed) ( ) • Modelling (Scenarios, TMDLs) • Specific scientific questions p q 11
What may be more important than LLA - Outline - O tli • Background knowledge g g – Limnological characteristics – Historic data (“blooms”, fish kill) – Knowledge from other studies/systems • Adequate sampling & handling, w/o contamination • Determine related variables (instead or in addition) • Adequate monitoring plan – Spatial and temporal sampling – Specific fractions to be determined • Use a model instead 12
(MOST) Important background ( ) g knowledge • Surface water – Eutrophication – Cyanobacterial blooms What is limiting algal growth? • Hypolimnia in lakes and reservoirs A Anoxic or not? i ? 13
Background knowledge Water is anoxic SRP, dissolved reactive P , filtered through 0.45 µ, colorimetric assay, molybdenum blue - ascorbic acid Sampling & handling: aeration or gas-tight S li & h dli i i h – Interference: H 2 S, Fe, organic (humic) acids id – Differs with method • Auto analyser • Auto analyser • Dilution • Holding & bench time Holding & bench time 14
Interference Fe & H 2 S in SRP analysis Effect of Aeration Effect of Aeration Soluble Fe: 3.15 mg/L g H 2 S: 15 mg/L, SRP= 719 µg/L g , µg 2 16m Lake Magog, 11 Aug 1981 12m Lake St. George, 24 June1982 Nürnberg 1984 15 Water Research 18: 369-377
Analytical complexities in anoxic waters y p Iron and hydrogen sulfide interferences with SRP • Iron: oxygenation of Fe 2+ to Fe 3+ and formation of oxy-hydroxides that adsorb PO 4 → SRP is underestimated SRP i d ti t d Prevention by anoxic filtration Further interference by humic acids F th i t f b h i id • H 2 S: Interference with molybdenum blue PO 4 assay (reductant) assay (reductant) → SRP is underestimated Prevention by aeration before filtration Prevention by aeration before filtration 16
Solution: total reactive P (TRP), aerated SRP vs TRP in anoxic hypolimnetic samples SRP vs TRP in anoxic hypolimnetic samples from 5 softwater lakes with high Fe 3 hardwater with H 2 S R 2 = 0.998, p<0.0001, n=174 TRP= 2.74 + 1.02 SRP Nürnberg 1984 17 Water Research 18: 369-377
Determine related variables • Simpler to measure: p – In anoxic water: • TRP instead of SRP • TP instead of SRP • SRP instead of BAP • Dissolved iron (SFe) for SRP ( ) – Secchi transparency for chlorophyll a pigment – Hydrogen sulfide smell or low redox potential i instead of low dissolved oxygen t d f l di l d 18
TP instead of SRP in anoxic hypolimnia Hypolimnetic SRP versus TP Hypolimnetic SRP versus TP 100.0 P ( g/L) 1:1 SRP 10.0 1.0 10 100 TP ( g/L) 19 Nürnberg & Peters 1984
In anoxic hypolimnia y • With increasing TP, an increasing g , g proportion is SRP, at 100 µg/L about 80% • Almost all SRP is biologically available BAP* At least 90%, when small amounts of hypolimnetic water are added to large amounts of surface water *Using radioactive bioassays that analyze for PO 4 Nürnberg & Peters 1984 20
SRP instead of BAP in anoxic hypolimnia hypolimnia SRP 100 ) AP ( g/L BA 10 N 51 R 2 N=51, R 2 = 0.99 0 99 1 1 1 10 10 100 100 SRP ( g/L) 21 Data from Nürnberg & Peters 1984
Dissolved iron (SFe) for SRP A Anoxic samples of Fitch Bay, i l f Fit h B Lake Memphremagog, QU, VT R 2 = 0.98, p<0.0001, n=11 22
What may be more important than LLA - Outline - Outline • Background knowledge • Adequate sampling & handling • Determine related variables Determine related variables • Adequate monitoring plan – Spatial and temporal sampling Spatial and temporal sampling – Variables to be determined • Use a model instead • Use a model instead 23
Adequate monitoring plan g 1. Spatial and temporal sampling p p p g – Representative or worse conditions wanted? – Bays with polluted inlets or max depth location – Reservoir sections: riverine, transition, dam – Water intake location (reservoir) – Surface vs. hypolimnion – Growing season, fall turnover, under ice 2. Careful selection of variables to be measured 24
P and Iron Profiles oligotrophic Chub Lake, ON , Sept. 13 1982 oligotrophic Chub Lake ON S t 13 1982 0.0 2.5 5.0 7.5 10.0 0 25 50 75 100 0 0 -5 -5 TP SRP SRP -10 -10 th (m) Dep -15 -15 DO TFE SFE FE2 -20 -20 -25 2 -25 25 0.0 2.5 5.0 7.5 10.0 0 25 50 75 100 mg/L 25 µg/L
TP, SRP Profiles at Dam of Brownlee Reservoir , 11 Aug 1999 at Dam of Brownlee Reservoir 11 A 1999 P (m g/L) 0000 0.000 0100 0.100 0.200 0200 0300 0.300 0400 0.400 0500 0.500 0 10 10 DRP DRP TP 20 30 epth (m) 40 De 50 60 70 26
Brownlee Reservoir, Snake River 27 Hells Canyon Complex, ID/OR
Site 6 71 Below Brownlee Dam (Outflow) Brownlee Dam Brownlee Brownlee Site 5 Site F RM 290 RM 290 Brownlee RM 286 Richland 86 r R Eagle Creek e d i v w e r o P Reservoir, ID/OR C r e e k Site E Site 4 RM 295 RM 300 RM 300 Sturgill Creek Daly Creek Total length: 100 km Deep section: 48 km Deep section: 48 km ek Cree Site 3.5 Site 3 5 Site D Site D Dennet RM 310 OREGON IDAHO Camping Boat Ramp Depth: Depth: 60 m 60 m Site C Site C RM 317 * Surface composite sample 30 R o c taken here k Creek Width: <1 km B u r 95 n Site 3 t Brownlee Dam McCall RM 322 Rive ver 86 86 71 Site B Cambridge RM 327 95 Weiser River Weiser 55 Weiser Weiser 84 Boise Site 1 RM 345 28 (Inflow)
1999 Brownlee Reservoir, 0.150 2000 2000 Gradient along axis TP (mg/L) 0.100 Total phosphorus p p 0.050 concentration averages Inflow ---- Shallow --- ---- Deep --- - in the surface water in Outflow 0.000 summer 1999 and 2000 350 350 340 340 330 330 320 320 310 310 300 300 290 290 280 280 Location (RM) 0.060 0.040 P (mg/L) SRP concentration averages in the surface averages in the surface DRP 0.020 water in summer 1999 Outflow and 2000 ----- Shallow --- ------- Deep ------- Inflow 0.000 350 340 330 320 310 300 290 280 Location (RM) Jul-Sep 1999 May-Sep 2000 29
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