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Effects of Sewage Sludge on the Growth of Potted Salt Marsh Plants Exposed to Natural Tidal Inundation

Authors

  • Richard R. Vance,

    1. Author for correspondence: Department of Organismic Biology  , Ecology, and Evolution, University of California, Los Angeles, CA 90095, U.S.A.
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  • Richard F. Ambrose,

    1. Environmental Science and Engineering Program and Department of Environmental Health Sciences  , University of California, Los Angeles, CA 90095, U.S.A.
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  • Sean S. Anderson,

    1. Author for correspondence: Department of Organismic Biology  , Ecology, and Evolution, University of California, Los Angeles, CA 90095, U.S.A.
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  • Spencer MacNeil,

    1. Environmental Science and Engineering Program and Department of Environmental Health Sciences  , University of California, Los Angeles, CA 90095, U.S.A.
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  • Timothy McPherson,

    1. Environmental Science and Engineering Program and Department of Environmental Health Sciences  , University of California, Los Angeles, CA 90095, U.S.A.
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  • Irene Beers,

    1. Environmental Science and Engineering Program and Department of Environmental Health Sciences  , University of California, Los Angeles, CA 90095, U.S.A.
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  • Thomas W. Keeney

    1. Environmental Division  , Naval Air Station Point Mugu, Point Mugu, CA 93042, U.S.A.
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Abstract

Abstract A growth experiment with native plants in pots exposed to natural environmental conditions evaluates the use of sewage sludge as a soil amendment in restoration of a southern California salt marsh. Sludge containing desirable organic matter but also undesirable heavy metal contaminants was mixed with a readily available matrix soil to reduce metal concentrations to levels below legal limits for land applications of sludge. Soil nutrient analysis revealed expected increases in total nitrogen and total phosphorus content with increasing sludge concentration. Soil metals analysis, however, revealed decreases in metal content with increased sludge concentration, a trend evidently caused by higher than expected metal content in the matrix soil. Five artificial soil mixtures ranging from 0 to 70% sludge were accompanied by natural wetland soil controls. Pots containing these soils were placed into a natural salt marsh. The pots were then planted with two native salt marsh plant species, Salicornia virginica and Frankenia grandifolia. Aboveground biomass was harvested after 12 months. Plant growth displayed no obvious change with increasing sludge concentration. Over the concentration ranges used, increased nutrient content did not stimulate plant growth and increased metal content did not inhibit plant growth. Plants grew better in natural wetland soil than in artificial soil mixtures, a trend probably caused by the substantially finer texture and higher organic content of natural soil. All sludge treatments differed more from the natural soil than from each other, implying that within the ranges examined, soil texture and organic content exerted more influence on plant growth than did metal or nutrient concentration. These results suggest that incorporating this sewage sludge in the soil of the restored salt marsh will neither benefit nor harm the plants that will live there and that greatest plant growth will be achieved by mixing the sludge with a fine-grained matrix soil.

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