ESM202_Lec16_catchment08

ESM202_Lec16_catchment08 - Catchment biogeochemistry:...

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Unformatted text preview: Catchment biogeochemistry: High-elevation environments Environmental issues Environmental issues Atmospheric deposition Land use changes Climate change High-elevation catchments High-elevation catchments of the Sierra Nevada of the Sierra Nevada Many Many small, shallow lakes with dilute, clear water Steep catchments with large areas of talus, thin soils and sparse vegetation Deep, seasonal snow cover Characteristics of atmospheric deposition Acidification and eutrophication patterns Atmospheric deposition to the Atmospheric deposition to the Sierra Nevada Sierra Nevada 0.45 0.50 0.55 0.60 0.65 1974 1979 1984 1989 1994 1999 OP Pesticide Application (1000 T yr-1) 35 40 45 50 55 60 65 70 Mean Daily PM 10 Emission (T day-1) OP Pesticides PM10 Emission Tulare County Agricultural and urban sources (local) Long-range transport Sampling snow water equivalence: snowfall represents 85 to 95% of annual precipitation Snowfall varied about five-fold between drought and El Nino conditions Sampling for chemical composition of snow: Snow is very dilute with ammonium and nitrate low, but significant constituents Snow Chemistry Mean pH = 5.4 Mean ammonium = 2.7 µM Mean nitrate = 2.5 µM S n o w 1 9 9 0 - 9 5 4 . 8 4 . 9 5 . 0 5 . 1 5 . 2 5 . 3 5 . 4 5 . 5 5 . 6 5 . 7 5 . 8 2 0 4 0 6 0 8 0 p H Frequency S n o w 1 9 9 0 - 9 5 1 2 3 4 5 6 7 8 9 1 0 2 0 4 0 6 0 8 0 1 0 0 A m m o n i u m ( µ E q / l ) Frequency M e a n = 5 . 3 9 M e a n = 2 . 7 1 S n o w 1 9 9 0 - 9 5 1 2 3 4 5 6 7 2 0 4 0 6 0 8 0 1 0 0 N i t r a t e ( µ E q / l) Frequency M e a n = 2 . 5 0 Sampling for rain chemistry: solutes in rain are about ten times higher than in snow Rain Chemistry pH is controlled by strong acids: HNO 3 and H 2 SO 4 Ammonium and nitrate concentrations are high 0 5 10 20 40 60 80 100 120 140 160 20 40 60 80 100 120 140 N itra te (µ E q /l) Frequency 0 5 10 20 40 60 80 100 120 140 160 40 80 120 160 Am m onium (µEq/l) Frequency S u m m e r S to rm s 4 .00 4.2 0 4.4 0 4 .60 4 .80 5 .00 5.2 0 5.4 0 5 .60 5 .80 6.00 2 0 4 0 6 0 8 0 1 0 0 p H Frequency Rainfall is highly variable and about 10% of snowfall Deposition by rain and snow are similar (with exceptions)...
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This note was uploaded on 08/06/2008 for the course ESM 202 taught by Professor Keller during the Winter '08 term at UCSB.

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ESM202_Lec16_catchment08 - Catchment biogeochemistry:...

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