Project at a Glance

Title: Survey of sensitivity of Southern California lakes to acid deposition

Principal Investigator / Author(s): Melack, John M

Contractor: UC Santa Barbara

Contract Number: A3-107-32

Research Program Area: Ecosystem & Multimedia Effects

Topic Areas: Acid Deposition, Ecosystem Impacts


During 1985-1986 solute composition of 23 California lakes and ponds and of streams entering the lakes was determined. The strategy was to sample the same waters during the autumn and under ice or soon after ice out and to evaluate the necessity of sampling at multiple stations and from more than one depth. Chemical parameters measured included pH, alkalinity, conductance, major cations (calcium, magnesium, sodium and potassium), major anions (nitrate, sulfate, chloride), silica, nutrients (ammonium and phosphate), total and total dissolved nitrogen and phosphorus and total and dissolved levels of aluminum, iron and manganese. Coastal ponds and low elevation ( < 1700 m) lakes exhibited circum neutral to alkaline pH, high alkalinity (500-6000 µeq·l-1) and high levels of dissolved ions (20-150 meq·l-1). Among the high altitude ( > 1800 m) lakes, pH was circum neutral to slightly acid and alkalinity was low (16-338 µeq·l-1). Insignificant spatial variation in pH, alkalinity and dissolved constituents was observed in these lakes during September-October 1985 and July-August 1986. Under ice cover in May 1986 lakes had vertical differences in alkalinity and other constituents. Dissolved and total nutrient determinations for Sierra Nevada lakes suggested that the availability of nitrogen is greater than that of phosphorus. Trace element levels for total aluminum ( < 22 µg·l-1), total iron ( < 73 µg·l-1), and total manganese ( < 11 µg·l-1) were very low in autumn 1985, increased slightly under ice-cover (but were less than 81, 390, 17µg·l-1, respectively) and were somewhat higher than the previous autumn in July-August 1986 for high altitude lakes with aluminum exhibiting the greatest and manganese the smallest change. Levels of chemical constituents in lakes sampled previously (1981 through 1984) or monitored by other surveys were within range of values observed.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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