Population growth of two limno-terrestrial Antarctic microinvertebrates in different aqueous soil media.

Terrestrial microinvertebrates provide important carbon and nutrient cycling roles in soil environments, particularly in Antarctica where larger macroinvertebrates are absent. The environmental preferences and ecology of rotifers and tardigrades in terrestrial environments, including in Antarctica, are not as well understood as their temperate aquatic counterparts. Developing laboratory cultures is critical to provide adequate numbers of individuals for controlled laboratory experimentation. In this study, we explore aspects of optimising laboratory culturing for two terrestrially sourced Antarctic microinvertebrates, a rotifer (Habrotrocha sp.) and a tardigrade (Acutuncus antarcticus). We tested a soil elutriate and a balanced salt solution (BSS) to determine their suitability as culturing media. Substantial population growth of rotifers and tardigrades was observed in both media, with mean rotifer population size increasing from 5 to 448 ± 95 (soil elutriate) and 274 ± 78 (BSS) individuals over 60 days and mean tardigrade population size increasing from 5 to 187 ± 65 (soil elutriate) and 138 ± 37 (BSS) over 160 days. We also tested for optimal dilution of soil elutriate in rotifer cultures, with 20-80% dilutions producing the largest population growth with the least variation in the 40% dilution after 36 days. Culturing methods developed in this study are recommended for use with Antarctica microinvertebrates and may be suitable for similar limno-terrestrial microinvertebrates from other regions.

Land application of industrial wastes: impacts on soil quality, biota, and human health.

Globally, waste disposal options such as landfill, incineration, and discharge to water, are not preferred long-term solutions due to their social, environmental, political, and economic implications. However, there is potential for increasing the sustainability of industrial processes by considering land application of industrial wastes. Applying waste to land can have beneficial outcomes including reducing waste sent to landfill and providing alternative nutrient sources for agriculture and other primary production. However, there are also potential hazards, including environmental contamination. This article reviewed the literature on industrial waste applications to soils and assessed the associated hazards and benefits. The review investigated wastes in relation to soil characteristics, dynamics between soils and waste constituents, and possible impacts on plants, animals, and humans. The current body of literature demonstrates the potential for the application of industrial waste into agricultural soils. The main challenge for applying industrial wastes to land is the presence of contaminants in some wastes and managing these to enhance positive effects and reduce negative outcomes to within acceptable limits. Examination of the literature also revealed several gaps in the research and opportunities for further investigation: specifically, a lack of long-term experiments and mass balance assessments, variable waste composition, and negative public opinion.

Preliminary investigation of effects of copper on a terrestrial population of the antarctic rotifer Philodina sp.

Terrestrial microinvertebrates in Antarctica are potentially exposed to contaminants due to the concentration of human activity on ice-free areas of the continent. As such, knowledge of the response of Antarctic microinvertebrates to contaminants is important to determine the extent of anthropogenic impacts. Antarctic Philodina sp. were extracted from soils and mosses at Casey station, East Antarctica and exposed to aqueous Cu for 96 h. The Philodina sp. was sensitive to excess Cu, with concentrations of 36 µg L-1 Cu (48 h) and 24 µg L-1 Cu (96 h) inhibiting activity by 50%. This is the first study to be published describing the ecotoxicologically derived sensitivity of a rotifer from a terrestrial population to metals, and an Antarctic rotifer to contaminants. It is also the first study to utilise bdelloid rotifer cryptobiosis (chemobiosis) as a sublethal ecotoxicological endpoint. This preliminary investigation highlights the need for further research into the responses of terrestrial Antarctic microinvertebrates to contaminants.

The effects of vehicular emissions on the activity and diversity of the roadside soil microbial community.

Motor vehicles emit a variety of pollutants including metals, petroleum hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). The relationships between metals, petroleum hydrocarbons and PAHs, soil respiration and microbial diversity (fungi and bacteria) were studied using control (n = 3) and roadside soils (n = 27) with different exposure periods to vehicle emissions (2-63 years). Bacterial diversity was found to be higher than control sites (P = 0.002) but was the same across different categories of road age (P = 0.328). Significant (r = -0.49, P = 0.007) contrasting behaviour of fungal and bacterial diversity was reported, with diversity increasing across all road types for bacteria and decreasing across all road types for fungi compared to control soils. Analysis of the bacterial community identified three distinct clusters, separated on age of contamination, suggesting that roadside bacterial communities change over time with pollution from vehicles with the potential development of metal resistant bacteria in roadside soils. In contrast, for fungal communities, a reduction in diversity with time of exposure to roadside vehicle emissions was observed suggesting the potential for reduced ecosystem functionality and soil health in roadside soils. This is the first study in the published literature to include both bacterial and fungal responses from aged roadside soils. The results from this study suggest that normal functionality of soil ecosystem services is being affected in roadside soils, potentially globally.

Review of the interactions between vehicular emitted potentially toxic elements, roadside soils, and associated biota.

Given the large size of the world road network, the land area affected by vehicular emissions is extensive. This review provides the first global picture of the relationships between vehicular emitted potentially toxic elements, roadside soils, and risks to associated biota. The following potentially toxic elements that accumulate in roadside soils have been examined in this review: As, Co, Cr, Cu, Mn, Mo, Ni, Pb, Pd, Pt, Rh, Se, Sb, Sn, Sr, Ti and Zn. The meta-analysis undertaken demonstrated an increase in concentrations of Cd, Pb, Zn, Pt, Pd and Rh in roadside soils compared to the mean global crustal concentrations. Positive correlations between potentially toxic element concentrations in roadside soil, plants, microbes, and animals were observed. Roadside studies have found increased potentially toxic element concentrations in plants and animals with increasing proximity to roads. The mean concentrations of Pb in roadside plants and vertebrates were at values above the World Health Organisation guidelines. Research has shown a range of impacts of potentially toxic elements in roadside soils on microbial activity including decreased litter decomposition, nitrogen fixation, nutrient cycling and enzyme synthesis. However, aside from the impact on microbial communities, there has been little research investigating the impacts of roadside soil elements on the associated biota. Thus, there is a need for research that investigates the toxicity of elements in roadside soils to plants and animals and to investigate the transfer of roadside elements through the food chain, and thus, risks posed to human health and the environment.

Assessing the Plant Growth Promoting and Arsenic Tolerance Potential of Bradyrhizobium japonicum CB1809.

Accumulation of heavy metals in soil is of concern to the agricultural production sector, because of the potential threat to food quality and quantity. Inoculation with plant growth-promoting bacteria (PGPR) has previously been shown to alleviate heavy metal stress but the mechanisms are unclear. Potential mechanisms by which inoculation with Bradyrhizobium japonicum CB1809 affected the legume soybean (Glycine max cv. Zeus) and the non-legume sunflower (Helianthus annus cv. Hyoleic 41) were investigated in solution culture under 5 µM As stress. Adding As resulted in As tissue concentrations of up to 5 mg kg-1 (shoots) and 250 mg kg-1 (roots) in both species but did not reduce shoot or root biomass. Inoculation increased root biomass but only in the legume (soybean) and only with As. Inoculation resulted in large (up to 100%) increases in siderophore concentration but relatively small changes (±10-15%) in auxin concentration in the rhizosphere. However, the increase in siderophore concentration in the rhizosphere did not result in the expected increases in tissue N or Fe, especially in soybean, suggesting that their function was different. In conclusion, siderophores and auxins may be some of the mechanisms by which both soybean and sunflower maintained plant growth in As-contaminated media.

Arsenic Concentrations and Dietary Exposure in Rice-Based Infant Food in Australia.

Rice-based products are widely used to feed infants and young children. However, the association of rice-based products and high arsenic (As) concentrations have been investigated in a number of studies, but there is limited information from Australia. Therefore, the purpose of this study was to determine the As concentration and dietary exposure in infant rice milk, cereal, crackers and pasta as well as to investigate the relationship between As concentration and rice content, rice type and product origin. Total arsenic (tAs) concentrations were determined by nitric acid digestion and ICP-MS while inorganic arsenic (iAs) was determined by acid extraction, followed by ICP-MS with an interfaced hydride generation system. Nearly 75% of samples had inorganic As exceeding the EU maximum levels for infants and children (0.1 mg kg-1) and the mean iAs percentage of total reached as high as 84.8%. High tAs concentration was positively correlated with rice content and also related to brown (wholegrain). Estimates of dietary exposure showed that infants consuming large amounts of rice pasta or crackers will have an increased risk of health impact associated with excess intake of As through dietary exposure. Moreover, the current Australian guidelines for As in rice (1 mg kg-1) are above the WHO or EU guideline and therefore, will be less protective of high sensitivity consumers like infants and children.

The Design and Synthesis of Fluorescent Coumarin Derivatives and Their Study for Cu2+ Sensing with an Application for Aqueous Soil Extracts.

A series of fluorescent coumarin derivatives 2a-e were systematically designed, synthesized and studied for their Cu2+ sensing performance in aqueous media. The sensitivities and selectivities of the on-to-off fluorescent Cu2+ sensing signal were in direct correlation with the relative arrangements of the heteroatoms within the coordinating moieties of these coumarins. Probes 2b and 2d exhibited Cu2+ concentration dependent and selective fluorescence quenching, with linear ranges of 0-80 µM and 0-10 µM, and limits of detection of 0.14 µM and 0.38 µM, respectively. Structural changes of 2b upon Cu2+ coordination were followed by fluorescence titration, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), mass spectrometry, and single crystal X-ray diffraction on the isolated Cu2+-coumarin complex. The results revealed a 1:1 stoichiometry between 2b and Cu2+, and that the essential structural features for Cu2+-selective coordination are the coumarin C=O and a three-bond distance between the amide NH and heterocyclic N. Probe 2b was also used to determine copper (II) levels in aqueous soil extracts, with recovery rates over 80% when compared to the standard soil analysis method: inductively coupled plasma-mass spectrometry (ICP-MS).

Phosphorus-Rich Biochars Can Transform Lead in an Urban Contaminated Soil.

Transformation of soil Pb to pyromorphites and phosphates has the potential to be an effective strategy to immobilize this contaminant in situ. Soil treatment using monocalcium phosphate, a commercial fertilizer (NTS Soft Rock) and biochars prepared from poultry litter and from biosolids at three different temperatures (300, 400, and 500°C) and two doses (1 and 3%) were evaluated. Lead bioaccesibility, mobility, and solid speciation were measured. Leachable Pb (determined with the toxicity characterized leaching procedure) was not significantly ( > 0.05) changed after biochar addition, but a significant decrease in bioaccesible Pb was found for several treatments ( < 0.05). This was particularly notable for treatments receiving biosolids prepared at 400 and at 500°C or monocalcium phosphate at the 3% dose. The decrease in bioaccesible Pb concentration in the biochar treatments was similar to traditional phosphate amendments. Our research found transformation of Pb species to the more stable pyromorphite and Pb-phosphate to be partially responsible for the observed changes, although other mechanisms, including pH changes, might also play an important role. Overall, pyrolysis was an effective method to upgrade waste streams and facilitate Pb immobilization, although key pyrolysis parameters need to be selected carefully.

Probing the effects of different lead compounds on the bioavailability of lead to plants.

Lead (Pb) is an important pollutant and is released into the environment in many forms. Different lead compounds have a variety of solubilities and so may impact on lead bioavailability and toxicity when added to soil. In this experimental study, we investigated the bioavailability of Pb in soil spiked with 300, 900 and 1500 mg/kg of Pb-acetate, PbCl2 and PbO using lettuce and wallaby grass. The concentration of Pb in the shoots of both species from control soils (2-3 mg/kg) was similar to previously reported concentrations in plants grown on uncontaminated soils. The Pb concentrations in the plant shoots increased with Pb concentrations in soil for lettuce (R2 = 0.526, P < 0.001) and wallaby grass (R2 = 0.776, P < 0.001). This study demonstrated that Pb bioavailability in soil was not affected by the type of Pb compound added to the soil for both plant species up to 1500 mg/kg Pb concentrations. Instead, the Pb concentration in the plant was best predicted by the total concentration of lead in the soil, irrespective of the original lead compound added to the soil. This research suggests that the original Pb compounds that contaminated the soil are unlikely to be an important factor in assessing Pb bioavailability, and hence risk, in soils.

Quantifying factors related to urban metal contamination in vegetable garden soils of the west and north of Melbourne, Australia.

Vegetable gardens in cities provide communities with fresh vegetables but also may contribute towards public exposure to metals present in soil from historical pollution. Contamination of some Melbourne garden soils with Pb (range 12.9-773 mg kg-1 in soil) was found with some soils exceeding the Australian human health screening criteria for residential land use of 300 mg kg-1. Cadmium concentrations (0.12-1.04 mg kg-1) were above the ambient background soil concentrations of <1 mg kg-1. Nickel concentrations (7.6-40.5 mg kg-1) and Cr (11.6-49.4 mg kg-1) were within the range of expected ambient background concentrations. Distance from the nearest arterial road, house age and the likely use of lead-based paints were the main factors explaining approximately 75% of soil Pb variability in garden soils. Metal concentrations in garden soils of wooden houses were found to be significantly higher than the garden soil of brick and concrete houses (Pb (p < 0.0001)) and Cd (p < 0.001)). Significant correlations were found between backyard garden soil metal concentration and house age for Pb (R2 = 0.83, p < 0.0001) and Cd (R2 = 0.40, p < 0.0002) and the distance from arterial roads for Pb (R2 = 0.38, p < 0.002), while Cr and Ni are related to soil characteristics cation exchange capacity, organic matter, and pH. Vegetable garden with elevated Pb and Cd had recognizable risk factors such as older, painted structures on adjacent houses and closer proximity to arterial roads with higher frequency traffic.

Immobilisation of geogenic arsenic and vanadium in iron-rich sediments and iron stone deposits.

Determination of how geogenic arsenic (As) and vanadium (V) is mobilised from naturally-enriched soils and iron (Fe) stones is integral for understanding the potential risk to the environment from changed land use conditions. Thus, the association of As, V and Fe in As-enriched sediments and Fe stones in Tertiary sediments of Melbourne, Australia, was assessed using chemical extraction methods, micro focused X-ray fluorescence and X-ray absorption spectroscopy. We show that the selective association of As with Fe during Fe stone formation has resulted in As enrichment of up to 60 times the concentration of surrounding soils, and 1000 times higher than mean As concentrations in world soils. In both soil and Fe stones, As was distributed with goethite as arsenate and relatively immobile under oxic conditions. The presence of V on the outer edge of the assessed Fe stone provided evidence of differences in historical As and V solubility; that is, As was immobilised by Fe during an earlier stage of Fe stone formation than V.

The guard cell ionome: Understanding the role of ions in guard cell functions.

The ionome is critical for plant growth, productivity, defense, and it eventually affects human food quantity and quality. Located on the leaf surface, stomatal guard cells are critical gatekeepers for water, gas, and pathogens. Insights form ionomics (metallomics) is imperative as we enter an omics-driven systems biology era where an understanding of guard cell function and physiology is advanced through efforts in genomics, transcriptomics, proteomics, and metabolomics. While the roles of major cations (K, Ca) and anions (Cl) are well known in guard cell function, the related physiology, movement and regulation of trace elements, metal ions, and heavy metals are poorly understood. The majority of the information on the role of trace elements in guard cells emanates from classical feeding experiments, field or in vitro fortification, micropropagation, and microscopy studies, while novel insights are available from limited metal ion transporter and ion channel studies. Given the rejuvenated and recent interest in the constantly changing ionome in plant mineral balance and eventually in human nutrition and health, we looked into the far from established guard cell ionome in lieu of the modern omics era of high throughput research endeavors. Newer technologies and tools i.e., high resolution mass spectrometry, advanced imaging, and phenomics are now available to delve into the guard cell ionomes. In this review, research efforts on guard cell ionomes were collated and categorized, and we highlight the underlying role of the largely unknown ionome in guard cell function towards a systems physiology understanding of plant health and productivity.

Environmental and anthropogenic influences on ambient background concentrations of fluoride in soil.

Excess exposure to fluoride causes substantive health burden in humans and livestock globally. However, few studies have assessed the distribution and controls of variability of ambient background concentrations of fluoride in soil. Ambient background concentrations of fluoride in soil were collated for Greater Melbourne, Greater Geelong, Ballarat and Mitchell in Victoria, Australia (n = 1005). Correlation analysis and machine learning techniques were used to identify environmental and anthropogenic influences of fluoride variability in soil. Sub-soils (>0.3 m deep), in some areas overlying siltstone and sandstone, and to a lesser extent, overlying basalt, were naturally enriched with fluoride at concentrations above ecological thresholds for grazing animals. Soil fluoride enrichment was predominantly influenced by parent material (mineralogy), precipitation (illuviation), leaching during palaeoclimates and marine inputs. Industrial air pollution did not significantly influence ambient background concentrations of fluoride at a regional scale. However, agricultural practices (potentially the use of phosphate fertilisers) were indicated to have resulted in added fluoride to surface soils overlying sediments. Geospatial variables alone were not sufficient to accurately model ambient background soil fluoride concentrations. A multiple regression model based on soil chemistry and parent material was shown to accurately predict ambient background fluoride concentrations in soils and support assessment of fluoride enrichment in the environment.

Geochemical indices and regression tree models for estimation of ambient background concentrations of copper, chromium, nickel and zinc in soil.

Geochemical ratios between elements of environmental concern and Fe have been recommended for estimation of "background" concentrations of Cr, Cu, Ni and Zn in soil. However, little research has occurred to assess the consistency of geochemical ratios across soils developed in different environments. Broad application of generic geochemical ratios could result in under or over estimation of anthropogenic impacts to soil and subsequent inaccurate assessment of risk to the environment. A soil survey was undertaken in Victoria, Australia, including collection of samples (n = 622) from surface (0-0.1 m below ground level) and sub-surface (0.3-0.6 m below ground level) soils, overlying Tertiary-Quaternary basalt, Tertiary sediments and Silurian siltstones and sandstones. Samples were analyzed for metals and soil physical and chemical properties (particle size, cation exchange capacity, organic matter and pH). Geochemical correlations between elements in soils from different parent materials and environments were compared against geochemical relationships reported in Australia and internationally. Ratios of Cr and Fe were relatively consistent across parent materials, and comparable to published models for estimation of background Cr. Conversely, ratios between Cu, Ni, and Zn with Fe, were variable between soils developed in different weathering environments and/or soil depths. Alternative regression equations and rule based regression tree models were developed as an improved means for prediction of ambient background Cu, Ni and Zn concentrations in soil. Ambient background concentrations of Ni and Cr were predictable across parent materials and depths, allowing these models to be extended to soils across Australia and potentially internationally.

Assessment of soil metal concentrations in residential and community vegetable gardens in Melbourne, Australia.

Gardening and urban food production is an increasingly popular activity, which can improve physical and mental health and provide low cost nutritious food. However, the legacy of contamination from industrial and diffuse sources may have rendered surface soils in some urban gardens to have metals value in excess of recommended guidelines for agricultural production. The objective of this study was to establish the presence and spatial extent of soil metal contamination in Melbourne's residential and inner city community gardens. A secondary objective was to assess whether soil lead (Pb) concentrations in residential vegetable gardens were associated with the age of the home or the presence or absence of paint. The results indicate that most samples in residential and community gardens were generally below the Australian residential guidelines for all tested metals except Pb. Mean soil Pb concentrations exceeded the Australian HIL-A residential guideline of 300 mg/kg in 8% of 13 community garden beds and 21% of the 136 residential vegetable gardens assessed. Mean and median soil Pb concentrations for residential vegetable gardens was 204 mg/kg and 104 mg/kg (range <4-3341 mg/kg), respectively. Mean and median soil Pb concentration for community vegetable garden beds was 102 mg/kg and 38 mg/kg (range = 17-578 mg/kg), respectively. Soil Pb concentrations were higher in homes with painted exteriors (p = 0.004); generally increased with age of the home (p = 0.000); and were higher beneath the household dripline than in vegetable garden beds (p = 0.040). In certain circumstances, the data indicates that elevated soil Pb concentrations could present a potential health hazard in a portion of inner-city residential vegetable gardens in Melbourne.

Evaluation of environmental and anthropogenic influences on ambient background metal and metalloid concentrations in soil.

There has been a global shift in environmental risk assessment towards quantifying ambient background concentrations of metals/metalloids in soil. Whilst bedrock has been shown to be a key driver of metal/metalloid variability in soil, few researchers have assessed controls of ambient background concentrations in soils of similar bedrock. A soil survey was undertaken ofGreater Melbourne, Greater Geelong, Ballarat and Mitchell in Victoria, Australia for elements of potential environmental concern: As, Cd, Cr, Cu, Ni, Hg, Pb and Zn. Samples (n=622) were collected from surface (0 to 0.1m) and sub-surface (0.3 to 0.6m) soils, overlying Tertiary-Quaternary basalt, Tertiary sediments and Silurian siltstone and sandstone. In addition, background soil data from open-source environmental assessment reports (n=5512) were collated to support the understanding of natural enrichment, particularly at depths >0.6m. Factor analysis, supported by correlation analysis and auxiliary geo-spatial data, provided an improved understanding of where and how background metal/metalloid enrichment occurs in the environment. Weathering during paleoclimates was the predominant influence of background metal/metalloid variability in soils overlying similar bedrock. Other key influences of metal/metalloid variability in soil included hydraulic leaching of alkali elements, biological cycling, topography and alluvial transfer of silt and sand from mineralised regions. In addition, urbanisation positively correlated with Pb and Zn concentrations in surface soils suggesting that anthropogenic activities may have resulted in diffuse Pb and Zn contamination of urban soil.

Evaluation of methods for managing censored results when calculating the geometric mean.

Currently, there are conflicting views on the best statistical methods for managing censored environmental data. The method commonly applied by environmental science researchers and professionals is to substitute half the limit of reporting for derivation of summary statistics. This approach has been criticised by some researchers, raising questions around the interpretation of historical scientific data. This study evaluated four complete soil datasets, at three levels of simulated censorship, to test the accuracy of a range of censored data management methods for calculation of the geometric mean. The methods assessed included removal of censored results, substitution of a fixed value (near zero, half the limit of reporting and the limit of reporting), substitution by nearest neighbour imputation, maximum likelihood estimation, regression on order substitution and Kaplan-Meier/survival analysis. This is the first time such a comprehensive range of censored data management methods have been applied to assess the accuracy of calculation of the geometric mean. The results of this study show that, for describing the geometric mean, the simple method of substitution of half the limit of reporting is comparable or more accurate than alternative censored data management methods, including nearest neighbour imputation methods.

Assessment of ambient background concentrations of elements in soil using combined survey and open-source data.

Understanding ambient background concentrations in soil, at a local scale, is an essential part of environmental risk assessment. Where high resolution geochemical soil surveys have not been undertaken, soil data from alternative sources, such as environmental site assessment reports, can be used to support an understanding of ambient background conditions. Concentrations of metals/metalloids (As, Mn, Ni, Pb and Zn) were extracted from open-source environmental site assessment reports, for soils derived from the Newer Volcanics basalt, of Melbourne, Victoria, Australia. A manual screening method was applied to remove samples that were indicated to be contaminated by point sources and hence not representative of ambient background conditions. The manual screening approach was validated by comparison to data from a targeted background soil survey. Statistical methods for exclusion of contaminated samples from background soil datasets were compared to the manual screening method. The statistical methods tested included the Median plus Two Median Absolute Deviations, the upper whisker of a normal and log transformed Tukey boxplot, the point of inflection on a cumulative frequency plot and the 95th percentile. We have demonstrated that where anomalous sample results cannot be screened using site information, the Median plus Two Median Absolute Deviations is a conservative method for derivation of ambient background upper concentration limits (i.e. expected maximums). The upper whisker of a boxplot and the point of inflection on a cumulative frequency plot, were also considered adequate methods for deriving ambient background upper concentration limits, where the percentage of contaminated samples is <25%. Median ambient background concentrations of metals/metalloids in the Newer Volcanic soils of Melbourne were comparable to ambient background concentrations in Europe and the United States, except for Ni, which was naturally enriched in the basalt-derived soils of Melbourne.