Trace Elements in Saanich Peninsula Agricultural Soils TRACE
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Trace Elements in Saanich Peninsula Agricultural Soils 1 TRACE ELEMENTS IN AGRICULTURAL SOILS OF SAANICH PENINSULA, VANCOUVER ISLAND, BRITISH COLUMBIA, CANADA By LEKHNATH GHIMIRE M.Sc., Tribhuvan University, 1999 A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in ENVIRONMENT AND MANAGEMENT We accept this thesis as conforming to the required standard .......................................................... Dr. Matt Dodd, Thesis Supervisor Royal Roads University ......................................................... Thesis Coordinator School of Environment and Sustainability .......................................................... Michael-Anne Noble, Director School of Environment and Sustainability ROYAL ROADS UNIVERSITY September 2012 © Lekhnath Ghimire, 2012 Trace Elements in Saanich Peninsula Agricultural Soils 2 Abstract The concentrations of trace elements in 30 Saanich Peninsula agricultural soil samples were determined by acid digestion and inductively coupled plasma – optical emission spectroscopy (ICP-OES). A comparison of the results obtained to a 1995 BC Ministry of Environment data indicated that As, Cu, Mo, Sb, Se and Sn concentrations had increased whereas the concentrations of Ba, Be, Cd, Cr, Co, Mn, Ni, Pb, V and Zn had decreased. The principal sources of the trace elements were anthropogenic sources including fertilizer and manure application, weathering of rocks and atmospheric deposition. The concentrations changes were largely influenced by the individual properties of the elements, soil texture, soil organic matter and clay content. The mobility of the trace elements in the soils was mainly controlled by clay content and followed the order Cd> B >Mo> Cr> V> Zn> Se> Co> Cr> As> Ba> Sb> Mn> Ag, Be, Hg, Ni, Pb. Key words Trace elements, agricultural soils, biogeochemical cycles, weathering of rocks, phosphate fertilizer, soil pH, clay and organic matter, bioavailability and mobility Trace Elements in Saanich Peninsula Agricultural Soils 3 Table of Contents Abstract ......................................................................................................................................................... 2 List of Figures ............................................................................................................................................... 5 List of Tables ................................................................................................................................................ 6 List of Appendices ........................................................................................................................................ 6 Acknowledgements ....................................................................................................................................... 7 Introduction ................................................................................................................................................... 8 Trace Elements.......................................................................................................................................... 8 The Biological Essentiality and Toxicity of Trace Elements .................................................................... 8 Sources of Trace Elements in Agricultural Soils .................................................................................... 10 Elements of Concern (EOC) in Agricultural Soils .................................................................................. 12 Scope of the Study .................................................................................................................................. 13 Research Questions ................................................................................................................................. 14 Literature Review and Background ............................................................................................................ 15 Trace Elements in England and Wales’ Farms ....................................................................................... 15 Trace Elements in Chinese Agricultural Soils ........................................................................................ 15 Trace Elements in USA Farms................................................................................................................ 16 Trace Elements Contaminations in Canadian Farms .............................................................................. 17 Trace Elements in Saanich Peninsula Farms .......................................................................................... 19 Geology and Soil Type of Saanich Peninsula Farms .............................................................................. 20 Mobility and Bioavailability of Trace Elements in Agricultural Soil ..................................................... 22 Factors Affecting Mobility and Bioavailability of Trace Elements ........................................................ 22 Soil pH ................................................................................................................................................ 23 Soil Organic Matter (SOM) ................................................................................................................ 24 Chemical Speciation ........................................................................................................................... 25 Clay Mineral’s Nature and Content .................................................................................................... 25 Trace Elements in Saanich Peninsula Agricultural Soils 4 Cation Exchange Capacity .................................................................................................................. 26 Oxides of Aluminium, Iron and Manganese ....................................................................................... 27 Rhizosphere Chemistry ........................................................................................................................... 27 Methodology ............................................................................................................................................... 29 Site Selection .......................................................................................................................................... 29 Soil Sampling Protocol ........................................................................................................................... 31 Soil Sample Preparation .......................................................................................................................... 31 Soil Characteristics ................................................................................................................................. 31 Total Elements Analysis ......................................................................................................................... 31 Selenium Speciation ................................................................................................................................ 32 Water Extraction Procedure .................................................................................................................... 32 Statistical Analysis .................................................................................................................................. 32 Results and Discussion ............................................................................................................................... 33 Soil Characteristics ................................................................................................................................. 33 Soil pH ................................................................................................................................................ 33 Soil Textures and Types ..................................................................................................................... 33 Soil Organic Matter (SOM) ................................................................................................................ 34 Soil Electrical Conductivity ................................................................................................................ 35 Total Trace Elements in Soils ................................................................................................................. 36 Comparison of Current Results to the 1995 BC Ministry of Environment Data ................................ 38 Antimony ............................................................................................................................................ 41 Barium ................................................................................................................................................ 42 Beryllium ............................................................................................................................................ 42 Boron .................................................................................................................................................. 42 Cadmium ............................................................................................................................................. 43 Chromium ..........................................................................................................................................