Effect of biochar amendment on the soil-atmosphere exchange of greenhouse gases from an intensive subtropical pasture in northern New South Wales, Australia

We assessed the effect of biochar incorporation into the soil on the soil-atmosphere exchange of the greenhouse gases (GHG) from an intensive subtropical pasture. For this, we measured N2O, CH4 and CO2 emissions with high temporal resolution from April to June 2009 in an existing factorial experiment where cattle feedlot biochar had been applied at 10 t ha-1 in November 2006. Over the whole measurement period, significant emissions of N2O and CO2 were observed, whereas a net uptake of CH4 was measured. N2O emissions were found to be highly episodic with one major emission pulse (up to 502 µg N2O-N m-2 h 1) following heavy rainfall. There was no significant difference in the net flux of GHGs from the biochar amended vs. the control plots. Our results demonstrate that intensively managed subtropical pastures on ferrosols in northern New South Wales of Australia can be a significant source of GHG. Our hypothesis that the application of biochar would lead to a reduction in emissions of GHG from soils was not supported in this field assessment. Additional studies with longer observation periods are needed to clarify the long term effect of biochar amendment on soil microbial processes and the emission of GHGs under field conditions.

Atmospheric deposition as a source of stormwater pollution in Gold Coast, Australia

Atmospheric deposition is one of the most important pollutant pathways for urban stormwater pollution. Atmospheric deposition can be in the form of dry and wet depositions which have distinct characteristics in terms of pollutant types, pollutant sources and influential parameters. This paper discusses the outcomes of a comprehensive study undertaken to identify the characteristics of wet and dry deposition of pollutants. Sample collection was undertaken at eight study sites with distinct characteristics. Four sites were close to road sites with varying traffic characteristics, whilst the other four sites had different land use characteristics. Dry deposition samples were collected for different antecedent dry days and wet deposition samples were collected immediately after rainfall events. The dry deposition was found to increase with the antecedent dry days and consisted of relatively coarser particles (greater than 1 µm) when compared to wet deposition. The wet deposition showed a strong affinity to rainfall depth, but was not related to the antecedent dry period. It was also found that smaller size particles (less than 1 µm) travel much longer distances from the source and deposit mainly with the wet deposition

Soil carbon sequestration rates and associated economic costs for farming systems of south-eastern Australia

Soil organic carbon (C) sequestration rates based on the Intergovernmental Panel for Climate Change (IPCC) methodology were combined with local economic data to simulate the economic potential for C sequestration in response to conservation tillage in the six agro-ecological zones within the Southern Region of the Australian grains industry. The net C sequestration rate over 20 years for the Southern Region (which includes discounting for associated greenhouse gases) is estimated to be 3.6 or 6.3 Mg C/ha after converting to either minimum or no-tillage practices, respectively, with no-till practices estimated to return 75% more carbon on average than minimum tillage. The highest net gains in C per ha are realised when converting from conventional to no-tillage practices in the high-activity clay soils of the High Rainfall and Wimmera agro-ecological zones. On the basis of total area available for change, the Slopes agro-ecological zone offers the highest net returns, potentially sequestering an additional 7.1 Mt C under no-tillage scenario over 20 years. The economic analysis was summarised as C supply curves for each of the 6 zones expressing the total additional C accumulated over 20 years for a price per t C sequestered ranging from zero to AU$200. For a price of $50/Mg C, a total of 427 000 Mg C would be sequestered over 20 years across the Southern Region, <5% of the simulated C sequestration potential of 9.1 Mt for the region. The Wimmera and Mid-North offer the largest gains in C under minimum tillage over 20 years of all zones for all C prices. For the no-tillage scenario, for a price of $50/Mg C, 1.74 Mt C would be sequestered over 20 years across the Southern Region, <10% of the simulated C sequestration potential of 18.6 Mt for the region over 20 years. The Slopes agro-ecological zone offers the best return in C over 20 years under no-tillage for all C prices. The Mallee offers the least return for both minimum and no-tillage scenarios. At a price of $200/Mg C, the transition from conventional tillage to minimum or no-tillage practices will only realise 19% and 33%, respectively, of the total biogeochemical sequestration potential of crop and pasture systems of the Southern Region over a 20-year period.

Assessing the resilience of potable water supplies in Southeast Queensland Australia

Historically, cities as urban forms have been critical to human development. In 1950, 30% of the world’s population lived in major cities. By the year 2000 this had increased to 47% with further expected growth to 50% by the end of 2007. Projections suggest that city-based densities will edge towards 60% of the global total by 2030. Such rapidly increasing urbanisation, in both developed and developing economies, challenges options for governance and planning, as well as crisis and disaster management. A common issue to the livability of cities as urban forms through time has been access to clean and reliable water supply. This is an issue that is particularly important in countries with arid ecosystems, such as Australia. This paper examines preliminary aspects, and theoretical basis, of a study into the resilience of the (potable) water supply system in Southeast Queensland (SEQ), an area with one of the most significant urban growth rates in Australia. The first stage will be to assess needs and requirements for gauging resilience characteristics of a generic water supply system, consisting of supply catchment, storage reservoir/s and treatment plant/s. The second stage will extend the analysis to examine the resilience of the SEQ water supply system incorporating specific characteristics of the SEQ water grid made increasingly vulnerable due to climate variability and projected impacts on rainfall characteristics and compounded by increasing demands due to population growth. Longer-term findings will inform decision making based on the application of the concept of resilience to designing and operating stand-alone and networked water supply infrastructure systems as well as its application to water resource systems more generally.

Application of electrical resistivity method to detect deep cracks in unsaturated residual soil slope

Crack is a significant influential factor in soil slope that could leads to rainfall-induced slope instability. Existence of cracks at soil surface will decrease the shear strength and increase the hydraulic conductivity of soil slope. Although previous research has shown the effect of surface-cracks in soil stability, the influence of deep-cracks on soil stability is still unknown. The limited availability of deep crack data due to the difficulty of effective investigate methods could be one of the obstacles. Current technology in electrical resistivity can be used to detect deep-cracks in soil. This paper discusses deep cracks in unsaturated residual soil slopes in Indonesia using electrical resistivity method. The field investigation such as bore hole and SPT tests was carried out at multiple locations in the area where the electrical resistivity testing have been conducted. Subsequently, the results from bore-hole and SPT test were used to verify the results of the electrical resistivity test. This study demonstrates the benefits and limitations of the electrical resistivity in detecting deep-cracks in a residual soil slopes.

Development and validation of novel methods for microbial source tracking based on Escherichia coli as an indicator of water quality

Microbial pollution in water periodically affects human health in Australia, particularly in times of drought and flood. There is an increasing need for the control of waterborn microbial pathogens. Methods, allowing the determination of the origin of faecal contamination in water, are generally referred to as Microbial Source Tracking (MST). Various approaches have been evaluated as indicatorsof microbial pathogens in water samples, including detection of different microorganisms and various host-specific markers. However, until today there have been no universal MST methods that could reliably determine the source (human or animal) of faecal contamination. Therefore, the use of multiple approaches is frequently advised. MST is currently recognised as a research tool, rather than something to be included in routine practices. The main focus of this research was to develop novel and universally applicable methods to meet the demands for MST methods in routine testing of water samples. Escherichia coli was chosen initially as the object organism for our studies as, historically and globally, it is the standard indicator of microbial contamination in water. In this thesis, three approaches are described: single nucleotide polymorphism (SNP) genotyping, clustered regularly interspaced short palindromic repeats (CRISPR) screening using high resolution melt analysis (HRMA) methods and phage detection development based on CRISPR types. The advantage of the combination SNP genotyping and CRISPR genes has been discussed in this study. For the first time, a highly discriminatory single nucleotide polymorphism interrogation of E. coli population was applied to identify the host-specific cluster. Six human and one animal-specific SNP profile were revealed. SNP genotyping was successfully applied in the field investigations of the Coomera watershed, South-East Queensland, Australia. Four human profiles [11], [29], [32] and [45] and animal specific SNP profile [7] were detected in water. Two human-specific profiles [29] and [11] were found to be prevalent in the samples over a time period of years. The rainfall (24 and 72 hours), tide height and time, general land use (rural, suburban), seasons, distance from the river mouth and salinity show a lack of relashionship with the diversity of SNP profiles present in the Coomera watershed (p values > 0.05). Nevertheless, SNP genotyping method is able to identify and distinquish between human- and non-human specific E. coli isolates in water sources within one day. In some samples, only mixed profiles were detected. To further investigate host-specificity in these mixed profiles CRISPR screening protocol was developed, to be used on the set of E. coli, previously analysed for SNP profiles. CRISPR loci, which are the pattern of previous DNA coliphages attacks, were considered to be a promising tool for detecting host-specific markers in E. coli. Spacers in CRISPR loci could also reveal the dynamics of virulence in E. coli as well in other pathogens in water. Despite the fact that host-specificity was not observed in the set of E. coli analysed, CRISPR alleles were shown to be useful in detection of the geographical site of sources. HRMA allows determination of ‘different’ and ‘same’ CRISPR alleles and can be introduced in water monitoring as a cost-effective and rapid method. Overall, we show that the identified human specific SNP profiles [11], [29], [32] and [45] can be useful as marker genotypes globally for identification of human faecal contamination in water. Developed in the current study, the SNP typing approach can be used in water monitoring laboratories as an inexpensive, high-throughput and easy adapted protocol. The unique approach based on E. coli spacers for the search for unknown phage was developed to examine the host-specifity in phage sequences. Preliminary experiments on the recombinant plasmids showed the possibility of using this method for recovering phage sequences. Future studies will determine the host-specificity of DNA phage genotyping as soon as first reliable sequences can be acquired. No doubt, only implication of multiple approaches in MST will allow identification of the character of microbial contamination with higher confidence and readability.

Water sensitive urban design through the lens of urban metabolism

Stormwater pollution has been recognised as one of the main causes of aquatic ecosystem degradation and poses a significant threat to both the goal of ecological sustainable development as well as human health and wellbeing. In response, water sensitive urban design (WSUD) practices have been put forward as a strategy to mitigate the detrimental impacts of urban stormwater runoff quality and to safeguard ecosystem functions. However, despite studies that support its efficiency in urban stormwater management, the mainstreaming of WSUD remains a significant challenge. This paper proposes that viewing WSUD through the lens of the integrated urban metabolism framework which encourages an interdisciplinary approach and facilitates dialogue through knowledge transfer is a strategy in which the implementation of WSUD can be mainstreamed.

Effects of climate change on the wash-off of volatile organic compounds from urban roads

The predicted changes in rainfall characteristics due to climate change could adversely affect stormwater quality in highly urbanised coastal areas throughout the world. This in turn will exert a significant influence on the discharge of pollutants to estuarine and marine waters. Hence, an in-depth analysis of the effects of such changes on the wash-off of volatile organic compounds (VOCs) from urban roads in the Gold Coast region in Australia was undertaken. The rainfall characteristics were simulated using a rainfall simulator. Principal Component Analysis (PCA) and Multicriteria Decision tools such as PROMETHEE and GAIA were employed to understand the VOC wash-off under climate change. It was found that low, low to moderate and high rain events due to climate change will affect the wash-off of toluene, ethylbenzene, meta-xylene, para-xylene and ortho-xylene from urban roads in Gold Coast. Total organic carbon (TOC) was identified as predominant carrier of toluene, meta-xylene and para-xylene in <1µm to 150µm fractions and for ethylbenzene in 150µm to >300µm fractions under such dominant rain events due to climate change. However, ortho-xylene did not show such affinity towards either TOC or TSS (total suspended solids) under the simulated climatic conditions.

SNP diversity of Enterococcus faecalis and Enterococcus faecium in a South East Queensland waterway, Australia, and associated antibiotic resistance gene profiles

BACKGROUND: Enterococcus faecalis and Enterococcus faecium are associated with faecal pollution of water, linked to swimmer-associated gastroenteritis and demonstrate a wide range of antibiotic resistance. The Coomera River is a main water source for the Pimpama-Coomera watershed and is located in South East Queensland, Australia, which is used intensively for agriculture and recreational purposes. This study investigated the diversity of E. faecalis and E. faecium using Single Nucleotide Polymorphisms (SNPs) and associated antibiotic resistance profiles. RESULTS: Total enterococcal counts (cfu/ml) for three/six sampling sites were above the United States Environmental Protection Agency (USEPA) recommended level during rainfall periods and fall into categories B and C of the Australian National Health and Medical Research Council (NHMRC) guidelines (with a 1-10% gastrointestinal illness risk). E. faecalis and E. faecium isolates were grouped into 29 and 23 SNP profiles (validated by MLST analysis) respectively. This study showed the high diversity of E. faecalis and E. faecium over a period of two years and both human-related and human-specific SNP profiles were identified. 81.8% of E. faecalis and 70.21% of E. faecium SNP profiles were associated with genotypic and phenotypic antibiotic resistance. Gentamicin resistance was higher in E. faecalis (47% resistant) and harboured the aac(6')-aph(2') gene. Ciprofloxacin resistance was more common in E. faecium (12.7% resistant) and gyrA gene mutations were detected in these isolates. Tetracycline resistance was less common in both species while tet(L) and tet(M) genes were more prevalent. Ampicillin resistance was only found in E. faecium isolates with mutations in the pbp5 gene. Vancomycin resistance was not detected in any of the isolates. We found that antibiotic resistance profiles further sub-divided the SNP profiles of both E. faecalis and E. faecium. CONCLUSIONS: The distribution of E. faecalis and E. faecium genotypes is highly diverse in the Coomera River. The SNP genotyping method is rapid and robust and can be applied to study the diversity of E. faecalis and E. faecium in waterways. It can also be used to test for human-related and human-specific enterococci in water. The resolving power can be increased by including antibiotic-resistant profiles which can be used as a possible source tracking tool. This warrants further investigation.

Influence of physical and chemical properties of solids on heavy metal adsorption

Partition of heavy metals between particulate and dissolve fraction of stormwater primarily depends on the adsorption characteristics of solids particles. Moreover, the bioavailability of heavy metals is also influenced by the adsorption behaviour of solids. However, due to the lack of fundamental knowledge in relation to the heavy metals adsorption processes of road deposited solids, the effectiveness of stormwater management strategies can be limited. The research study focused on the investigation of the physical and chemical parameters of solids on urban road surfaces and, more specifically, on heavy metal adsorption to solids. Due to the complex nature of heavy metal interaction with solids, a substantial database was generated through a series of field investigations and laboratory experiments. The study sites for the build-up pollutant sample collection were selected from four urbanised suburbs located in a major river catchment. Sixteen road sites were selected from these suburbs and represented typical industrial, commercial and residential land uses. Build-up pollutants were collected using a wet and dry vacuum collection technique which was specially designed to improve fine particle collection. Roadside soil samples were also collected from each suburb for comparison with the road surface solids. The collected build-up solids samples were separated into four particle size ranges and tested for a range of physical and chemical parameters. The solids build-up on road surfaces contained a high fraction (70%) of particles smaller than 150ìm, which are favourable for heavy metal adsorption. These solids particles predominantly consist of soil derived minerals which included quartz, albite, microcline, muscovite and chlorite. Additionally, a high percentage of amorphous content was also identified in road deposited solids. In comparing the mineralogical data of surrounding soil and road deposited solids, it was found that about 30% of the solids consisted of particles generated from traffic related activities on road surfaces. Significant difference in mineralogical composition was noted in different particle sizes of build-up solids. Fine solids particles (<150ìm) consisted of a clayey matrix and high amorphous content (in the region of 40%) while coarse particles (>150ìm) consisted of a sandy matrix at all study sites, with about 60% quartz content. Due to these differences in mineralogical components, particles larger than and smaller than 150ìm had significant differences in their specific surface area (SSA) and effective cation exchange capacity (ECEC). These parameters, in turn, exert a significant influence on heavy metal adsorption. Consequently, heavy metal content in >150ìm particles was lower than in the case of fine particles. The particle size range <75ìm had the highest heavy metal content, corresponding with its high clay forming minerals, high organic matter and low quartz content which increased the SSA, ECEC and the presence of Fe, Al and Mn oxides. The clay forming minerals, high organic matter and Fe, Al and Mn oxides create distinct groups of charge sites on solids surfaces and exhibit different adsorption mechanisms and bond strength, between heavy metal elements and charge sites. Therefore, the predominance of these factors in different particle sizes leads to different heavy metal adsorption characteristics. Heavy metals show preference for association with clay forming minerals in fine solids particles, whilst in coarse particles heavy metals preferentially associate with organic matter. Although heavy metal adsorption to amorphous material is very low, the heavy metals embedded in traffic related materials have a potential impact on stormwater quality.Adsorption of heavy metals is not confined to an individual type of charge site in solids, whereas specific heavy metal elements show preference for adsorption to several different types of charge sites in solids. This is attributed to the dearth of preferred binding sites and the inability to reach the preferred binding sites due to competition between different heavy metal species. This confirms that heavy metal adsorption is significantly influenced by the physical and chemical parameters of solids that lead to a heterogeneity of surface charge sites. The research study highlighted the importance of removal of solids particles from stormwater runoff before they enter into receiving waters to reduce the potential risk posed by the bioavailability of heavy metals. The bioavailability of heavy metals not only results from the easily mobile fraction bound to the solids particles, but can also occur as a result of the dissolution of other forms of bonds by chemical changes in stormwater or microbial activity. Due to the diversity in the composition of the different particle sizes of solids and the characteristics and amount of charge sites on the particle surfaces, investigations using bulk solids are not adequate to gain an understanding of the heavy metal adsorption processes of solids particles. Therefore, the investigation of different particle size ranges is recommended for enhancing stormwater quality management practices.

An experimental and computational investigation of performance of Green Gully for reusing stormwater

A new stormwater quality improvement device (SQID) called ‘Green Gully’ has been designed and developed in this study with an aim to re-using stormwater for irrigating plants and trees. The main purpose of the Green Gully is to collect road runoff/stormwater, make it suitable for irrigation and provide an automated network system for watering roadside plants and irrigational areas. This paper presents the design and development of Green Gully along with experimental and computational investigations of the performance of Green Gully. Performance (in the form of efficiency, i.e. the percentage of water flow through the gully grate) was experimentally determined using a gully model in the laboratory first, then a three dimensional numerical model was developed and simulated to predict the efficiency of Green Gully as a function of flow rate. Computational Fluid Dynamics (CFD) code FLUENT was used for the simulation. GAMBIT was used for geometry creation and mesh generation. Experimental and simulation results are discussed and compared in this paper. The predicted efficiency was compared with the laboratory measured efficiency. It was found that the simulated results are in good agreement with the experimental results.

Bribie Island groundwater resources : challenges in development of conceptual and numerical models

Groundwater is a major resource on Bribie Island and its sustainable management is essential to maintain the natural and modified eco-systems, as well as the human population and the integrity of the island as a sand mass. An effective numerical model is essential to enable predictions, and to test various water use and rainfall/climate scenarios. Such a numerical model must, however, be based on a representative conceptual hydrogeological model to allow incorporation of realistic controls and processes. Here we discuss the various hydrogeological models and parameters, and hydrological properties of the materials forming the island. We discuss the hydrological processes and how they can be incorporated into these models, in an integrated manner. Processes include recharge, discharge to wetlands and along the coastline, abstraction, evapotranspiration and potential seawater intrusion. The types and distributions of groundwater bores and monitoring are considered, as are scenarios for groundwater supply abstraction. Different types of numerical models and their applicability are also considered

Mapping of shallow coastal groundwaters, their hydrology and environmental geochemistry : Pumicestone catchment, Southeast Queensland

Blooms of the toxic cyanobacterium majuscula Lyngbya in the coastal waters of southeast Queensland have caused adverse impacts on both environmental health and human health, and on local economies such as fishing and tourism. A number of studies have confirmed that the main limiting nutrients (“nutrients of concern”) that contribute to these blooms area Fe, DOC, N, P and also pH. This study is conducted to establish the distribution of these parameters in a typical southeast Queensland coastal setting. The study maps the geochemistry of shallow groundwater in the mainland Pumicestone catchment with an emphasis on the nutrients of concern to understand how these nutrients relate to aquifer materials, landuse and anthropogenic activities. The results of the study form a GIS information layer which will be incorporated into a larger GIS model being produced by Queensland Department of Environment and Resource Management (DERM) to support landuse management to avoid/minimize blooms of Lyngbya in Moreton Bay, southeast Queensland, and other similar settings. A total of 38 boreholes were established in the mainland Pumicestone region and four sampling rounds of groundwater carried out in both dry and wet conditions. These groundwater samples were measured in the field for physico-chemical parameters, and in the laboratory analyses for the nutrients of concern, and other major and minor ions. Aquifer materials were confirmed using the Geological Survey of Queensland digital geology map, and geomaterials were assigned to seven categories which are A (sands), B (silts, sandy silts), C (estuarine mud, silts), D (humid soils), E (alluvium), F (sandstone) and G (other bedrock). The results of the water chemistry were examined by use of the software package AquaChem/AqQA, and divided into six groundwater groups, based on groundwater chemical types and location of boreholes. The type of aquifer material and location, and proximity to waterways was found to be important because they affected physico-chemical properties and concentrations of nutrients of concern and dissolved ions. The analytical results showed that iron concentrations of shallow groundwaters were high due to acid sulfate soils, and also mud and silt, but were lower in sand materials. DOC concentrations of these shallow groundwaters in the sand material were high probably due to rapid infiltration. In addition, DOC concentrations in some boreholes were high because they were installed in organic rich wetlands. The pH values of boreholes were from acidic to near neutral; some boreholes with pH values were low (< 4), showing acid sulfate soils in these boreholes. Concentrations of total nitrogen and total phosphorus of groundwaters were generally low, and the main causes of elevated concentrations of total nitrogen and total phosphorus are largely due to animal and human wastes and tend to be found in localized source areas. Comparison of the relative percentage of nitrogen species (NH3/NH4< Org-N, NO3-N and NO2-N) demonstrated that they could be related to sources such as animal waste, residential and agricultural fertilizers, forest and vegetation, mixed residents and farms, and variable setting and vegetation covers. Total concentrations of dissolved ions in sampling round 3 (dry period) were higher than those in sampling round 2 (wet period) due to both evaporation of groundwater in the dry period and the dilution of rainfall in the wet period. This showed that the highest concentrations of nutrients of concern were due to acid sulfate soils, aquifer materials, landuse and anthropogenic activities and were typically in aquifer materials of E (alluvium) and C (estuarine muds) and locations of Burpengary, Caboolture, and Glass Mountain catchments.

Role of solids in heavy metals build-up on urban road surfaces

Solids are widely identified as a carrier of harmful pollutants in stormwater runoff exerting a significant risk to receiving waters. This paper outlines the findings of an in-depth investigation on heavy metal adsorption to solids surfaces. Pollutant build-up samples collected from sixteen road sites in residential, industrial and commercial land uses were separated into four particle size ranges and analysed for a range of physico-chemical parameters and nine heavy metals including Iron (Fe), Aluminum (Al), Lead (Pb), Zinc (Zn), Cadmium (Cd), Chromium (Cr), Manganese (Mn), Nickel (Ni) and Copper (Cu). High specific surface area (SSA) and total organic carbon (TOC) content in finer particle size ranges was noted, thus confirming strong correlations with heavy metals. Based on their physico-chemical characteristics, two different types of solids originating from traffic and soil sources were identified. Solids generated by traffic were associated with high loads of heavy metals such as Cd and Cr with strong correlation with SSA. This suggested the existence of surface dependent bonds such as cation exchange between heavy metals and solids. In contrast, Fe, Al and Mn which can be attributed to soil inputs showed strong correlation with TOC suggesting strong bonds such as chemsorption. Zn was found to be primarily attached to solids by bonding with the oxides of Fe, Al and Mn. The data analysis also confirmed the predominance of the finer fraction, with 70% of the solids being finer than 150 µm and containing 60% of the heavy metal pollutant load.

Inadequacy of land use and impervious area fraction for determining urban stormwater quality

Urban stormwater quality is multifaceted and the use of a limited number of factors to represent catchment characteristics may not be adequate to explain the complexity of water quality response to a rainfall event or site-to-site differences in stormwater quality modelling. This paper presents the outcomes of a research study which investigated the adequacy of using land use and impervious area fraction only, to represent catchment characteristics in urban stormwater quality modelling. The research outcomes confirmed the inadequacy of the use of these two parameters alone to represent urban catchment characteristics in stormwater quality prediction. Urban form also needs to be taken into consideration as it was found have an important impact on stormwater quality by influencing pollutant generation, build-up and wash-off. Urban form refers to characteristics related to an urban development such as road layout, spatial distribution of urban areas and urban design features.