© 2004. SuperSoil 2004: 3 rd Australian New Zealand Soils Conference, 5 – 9 December 2004, University of Sydney, Australia. Published on CDROM. Website www.regional.org.au/au/asssi/ 1 Influence of copper on soil microbial biomass and biodiversity in some NSW soils. Nargis A. Banu, Balwant Singh and Les Copeland Faculty of Agriculture, Food and Natural Resources, the University of Sydney, NSW 2006, Australia. banu_nargis@hotmail.com Abstract Copper is one of the essential elements for all living organisms; however it becomes toxic at concentration exceeding certain limits. Eight surface soils (0-15 cm) including one Ferrosol (Robertson), two Tenosols (Catombal, Windsor), two Kurosols (Somersby, Box Hill), one Sodosol (Pine), one Chromosol (Brinsley) and one Kandosol (Lucerne), were collected from mainly pasture sites in NSW. The soils had different physico-chemical properties and there were some differences between the sites in climatic conditions. Copper was added as Cu(NO 3 ) 2. 4H 2 O salt to 1 kg oven-dry equivalent soils at six different levels (0, 60, 150, 300, 600, 1500 mg Cu kg -1 dry soil) in polythene bags and samples were incubated at room temperature. Soil microbial biomass carbon (MBC) was estimated by the chloroform- fumigation (CF) extraction method, and substrate utilization patterns determined by the Biolog method were used to assess the functional diversity of the microorganisms in these soils after 45 and 270 days of incubation. The extractable Cu in soils was determined using EDTA and CaCl 2 solutions at each sampling time. After 45 days of incubation, soil microbial biomass and diversity in soils were significantly affected from 300 mg Cu kg -1 soil in all studied soils. However after 270 days of incubation, significant effects were observed at all Cu concentration in all the studied soils. Soil properties such as pH, organic carbon and clay content affected the Cu toxicity to soil microbes. Key Words Microbial biomass, diversity index, richness, evenness. Introduction There have been increasing concerns in Australia and world wide about heavy metal contamination of soil by urban wastes and by-products of rural, industrial, and agricultural activities. The effective toxicity of heavy metals to soil ecosystems depends not only on their total metal concentrations and soil properties, but also, and perhaps more importantly, on their biochemical speciation and available form (Singh 2002). Heavy metals affect growth, morphology and metabolism of microorganisms in soils, through functional disturbance, protein denaturation or the destruction of the integrity of cell membranes (Leita et al. 1995). Copper is one of the essential elements for all living organisms; however it becomes toxic at concentration exceeding certain limits. It is required for the functioning of more than 30 enzymes, all of which are either redox catalysts or dioxygen carriers (Wright and Welbourn 2002). Soil bacteria and fungi have mechanisms for transporting Cu into cells. Copper transfer between proteins protects the organism from the toxic effects of inappropriate Cu binding and to deliver the metal to the correct enzymes (Pufahl et al. 1997). Major sources of Cu entering into the environment are extraction from its ore (mining, milling, and smelting), agricultural activities, and waste disposal (Ross 1994). Soils have become contaminated with Cu by deposition of dust from local sources such as foundries and smelters, as well as from direct application of fungicides and sewage sludge. Olszowy et al. (1993) observed 466 mg Cu kg -1 soil in Australian urban soils, where Tiller (1992) observed 360 mg kg –1 soil at one of the Sydney contaminated site. The National Environmental Protection Measure has set the Ecological Investigation Levels (EILs) for soil Cu concentration at 100 mg kg -1 (Interim Urban) in Australia in 1999 as trigger for remediation. Generally, heavy metals in soil exist in soluble and exchangeable forms and as organic and inorganic complexes. Different forms of heavy metals have different mobilities and, therefore, different bioavailabilities. Adsorption and desorption strongly affect bioavailability of heavy metals and therefore toxicity in soil. However, measured availability of metal ions also depends on pH, ionic strength of the extractant, contact time between metal ion and soils and on the competition with other metals ions as well as presence of inorganic or organic ligands (Renella et al. 2004). In the soil solution, Cu 2+ ions compete with more abundant soil cations such as Ca 2+ and Na + for exchange sites.