Moody P.W.,0 Meiers Rd
Soil Research | Year: 2011
Soluble reactive phosphorus (SP) present in groundwater (GW) is generally considered insignificant, and therefore of little consequence to the quality of waters receiving base-flow discharges. In this study we investigated whether: (i) significant quantities of SP were present in GW (GW-SP); (ii) potential existed for GW-SP to be exported to streams via base-flow discharge; and (iii) the exports are a health risk to ecosystems receiving base-flow discharges. Investigations were carried out at two sites in the Tully River Catchment (TRC) during three consecutive rainy seasons, and 24 wells in the Johnstone River Catchment (JRC) were also monitored during one rainy season, in the north-eastern wet tropics of Australia. In the TRC, the GW-SP varied temporally, within and between rainy seasons, from 2 to 158μgP/L at Site 1 and from 3 to 31μP/L at Site 2. The temporal variations in GW-SP were driven by fluctuating water-table at Site 2, but no such trend was observed at Site 1. The SP in drain-water (DW-SP) varied temporally from 0.6 to 110μgP/L at Site 1, compared with 2-83μgP/L at Site 2. The positive association between DW-SP and GW-SP at Site 2 indicated an export of SP from GW to a drain via base-flow discharge. In the JRC, the GW-SP in the 24 wells varied temporally from 0 to 300μgP/L with the means across the wells ranging from 5 to 190μgP/L, with the variations driven by fluctuating water-tables. More than 50% of the GW-SP or DW-SP concentrations in TRC were significantly higher than the P trigger values, 2-5μgP/L, proposed to sustain the health of aquatic ecosystems in this region; a similar result was observed in the JRC. Speciation analysis via filtering (i.e. P passing through a 0.45-μm filter) for selected GW samples indicated substantial quantities of soluble organic P in some wells, ranging from 5 to 89% (mean 38%) of the total soluble P (SP plus soluble organic P). Because the soluble organic P was not included in GW-SP determinations, the hazard/risk mentioned above is an underestimate. The GW-SP exported during rainy seasons, from both catchments, ranged from 0.16 to 0.43kgP/ha. Our findings indicate there were significant quantities of SP and soluble organic P in GW, it was exported to streams, and there is a health risk to receiving surface water bodies. © 2011 CSIRO.
Chan Y.C.,Griffith University |
Sinha R.K.,Griffith University |
Wang W.,0 Meiers Rd
Waste Management and Research | Year: 2011
This study investigated greenhouse gas (GHG) emissions from three different home waste treatment methods in Brisbane, Australia. Gas samples were taken monthly from 34 backyard composting bins from January to April 2009. Averaged over the study period, the aerobic composting bins released lower amounts of CH 4 (2.2 mg m - 2 h -1) than the anaerobic digestion bins (9.5 mg m -2 h -1) and the vermicomposting bins (4.8 mg m -2 h -1). The vermicomposting bins had lower N 2O emission rates (1.2 mg m -2 h - 1) than the others (1.5-1.6 mg m -2 h -1). Total GHG emissions including both N 2O and CH 4 were 463, 504 and 694 mg CO 2-e m - 2 h -1 for vermicomposting, aerobic composting and anaerobic digestion, respectively, with N 2O contributing >80% in the total budget. The GHG emissions varied substantially with time and were regulated by temperature, moisture content and the waste properties, indicating the potential to mitigate GHG emission through proper management of the composting systems. In comparison with other mainstream municipal waste management options including centralized composting and anaerobic digestion facilities, landfilling and incineration, home composting has the potential to reduce GHG emissions through both lower on-site emissions and the minimal need for transportation and processing. On account of the lower cost, the present results suggest that home composting provides an effective and feasible supplementary waste management method to a centralized facility in particular for cities with lower population density such as the Australian cities. © The Author(s) 2010.
Allen D.E.,0 Meiers Rd |
Pringle M.J.,0 Meiers Rd |
Page K.L.,0 Meiers Rd |
Dalal R.C.,0 Meiers Rd |
Dalal R.C.,University of Queensland
Rangeland Journal | Year: 2010
The accurate measurement of the soil organic carbon (SOC) stock in Australian grazing lands is important due to the major role that SOC plays in soil productivity and the potential influence of soil C cycling on Australia's greenhouse gas emissions. However, the current sampling methodologies for SOC stock are varied and potentially conflicting. It was the objective of this paper to review the nature of, and reasons for, SOC variability; the sampling methodologies commonly used; and to identify knowledge gaps for SOC measurement in grazing lands. Soil C consists of a range of biological materials, in various SOC pools such as dissolved organic C, micro- and meso-fauna (microbial biomass), fungal hyphae and fresh plant residues in or on the soil (particulate organic C, light-fraction C), the products of decomposition (humus, slow pool C) and complexed organic C, and char and phytoliths (inert, passive or resistant C); and soil inorganic C (carbonates and bicarbonates). Microbial biomass and particulate or light-fraction organic C are most sensitive to management or land-use change; resistant organic C and soil carbonates are least sensitive. The SOC present at any location is influenced by a series of complex interactions between plant growth, climate, soil type or parent material, topography and site management. Because of this, SOC stock and SOC pools are highly variable on both spatial and temporal scales. This creates a challenge for efficient sampling. Sampling methods are predominantly based on design-based (classical) statistical techniques, crucial to which is a randomised sampling pattern that negates bias. Alternatively a model-based (geostatistical) analysis can be used, which does not require randomisation. Each approach is equally valid to characterise SOC in the rangelands. However, given that SOC reporting in the rangelands will almost certainly rely on average values for some aggregated scale (such as a paddock or property), we contend that the design-based approach might be preferred. We also challenge soil surveyors and their sponsors to realise that: (i) paired sites are the most efficient way of detecting a temporal change in SOC stock, but destructive sampling and cumulative measurement errors decrease our ability to detect change; (ii) due to (i), an efficient sampling scheme to estimate baseline status is not likely to be an efficient sampling scheme to estimate temporal change; (iii) samples should be collected as widely as possible within the area of interest; (iv) replicate of laboratory analyses is a critical step in being able to characterise temporal change. Sampling requirements for SOC stock in Australian grazing lands are yet to be explicitly quantified and an examination of a range of these ecosystems is required in order to assess the sampling densities and techniques necessary to detect specified changes in SOC stock and SOC pools. An examination of techniques that can help reduce sampling requirements (such as measurement of the SOC fractions that are most sensitive to management changes and/or measurement at specific times of the year preferably before rapid plant growth to decrease temporal variability), and new technologies for in situ SOC measurement is also required. © Australian Rangeland Society 2010.