Concentrations of vehicular emitted heavy metals in roadside soils result in long term environmental damage. This study assessed the relationships between traffic characteristics (traffic density, ...road age and vehicular speed) and roadside soil heavy metals. Significant levels were recorded for Cd (0.06–0.59 mg/kg), Cr (18–29 mg/kg), Cu (4–12 mg/kg), Ni (7–20 mg/kg), Mn (92–599 mg/kg), Pb (16–144 mg/kg) and Zn (10.36–88.75 mg/kg), with Mn concentrations exceeding the Ecological Investigation Level. Significant correlations were found between roadside soil metal concentration and vehicular speed (R = 0.90), road age (R = 0.82) and traffic density (R = 0.68). Recently introduced metals in automotive technology (e.g. Mn and Sb) were higher in younger roads, while the metals present for many years (e.g. Cd, Cu, Pb, Zn) were higher in medium and old age roads confirming the risk of significant metal deposition and soil metal retention in roadside soils.
•Elevated metal concentrations were recorded from Melbourne roadside soils.•Mn and Sb tended to be higher in younger roads.•Cd, Cu, Pb and Zn were particularly elevated in medium and old age roads.•Accumulation of Ag, Co and Sb were identified as potential emerging risks.•Mn concentrations exceeded Australian ecological investigation levels.
Investigating relationships between road age, traffic density and vehicular speed on the concentrations of metals in roadside soils.
Finding a reliable method to predict soil metal bioavailability in aged soil continues to be one of the most important problems in contaminated soil chemistry. To investigate the bioavailability of ...metals aged in soils, we used roadside soils that had accumulated metals from vehicle emissions over a range of years. We collected topsoil (0–10 cm) samples representing new-, medium- and old-aged roadside soils and control site soil. These soils were studied to compare the ability of the diffusive gradients in thin films technique (DGT), soil water extraction, CaCl2 extraction, total metal concentrations and optimised linear models to predict metal bioavailability in wheat plants. The response time for the release of metals and the effect on metal bioavailability in field aged soils was also studied. The DGT, and extractable metals such as CaCl2 extractable and soil solution metals in soil, were not well correlated with metal concentrations in wheat shoots. In comparison, the strongest relationships with concentrations in wheat shoots were found for Ni and Zn total metal concentrations in soil (e.g., Ni r = 0.750, p = 0.005 and Zn r = 0.833, p = 0.001); the correlations were still low, suggesting that total metal concentrations were also not a robust measure of bioavailability. Optimised linear models incorporating soil physiochemical properties and metal extracts together with road age as measure of exposure time, demonstrated a very strong relationship for Mn R2 = 0.936; Ni R2 = 0.936 and Zn R2 = 0.931. While all the models developed were dependent on total soil metal concentrations, models developed for Mn and Zn clearly demonstrated the effect of road age on metal bioavailability. Therefore, the optimised linear models developed have the potential for robustly predicting bioavailable metal concentrations in field soils where the metals have aged in situ. The intrinsic rate of release of metals increased for Mn (R2 = 0.617, p = 0.002) and decreased for Cd (R2 = 0.456, p = 0.096), Cu (R2 = 0.560, p = 0.083) and Zn (R2 =0.578, p = 0.072). Nickel did not show any relationship between dissociation time (Tc) and road age. Roadside soil pH was likely to be the key parameter controlling metal aging in roadside soil.
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.
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•First comprehensive review of vehicle emitted elements in roadside soil and biota.•Emerging risks from Cd, Cu, Ni and Zn on roadside soil systems identified.•Transfer of potentially toxic elements from soil to the food chain is documented.•Lead concentrations in roadside plants and animals higher than WHO guidelines.
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
) 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
) are above the WHO or EU guideline and therefore, will be less protective of high sensitivity consumers like infants and children.
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.
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.
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•For the first time, the impacts of long-term vehicular emissions on the roadside soil microbial community were studied.•Differing responses of roadside soil bacteria and fungi to long term roadside soil pollution was found.•Three clusters of bacteria were reported from different ages of roads.•No clusters were reported for fungi from different ages of roads.
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.
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•Different Pb compounds (Pb-acetate, PbO and PbCl2) added to soil had no significant effect on plant uptake.•Different Pb compounds added to soil showed a significant linear correlation between Pb concentrations and plant Pb uptake.•Lead compounds are unlikely to be an important factor in assessing Pb bioavailability, and hence risk, in soils.
Capsule: Different Pb compounds added to soil (Pb-acetate, PbO and PbCl2) showed no significant effect on plant uptake and are unlikely to be an important factor in assessing Pb bioavailability, and hence risk, in soils.
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•Highly controlled synthesis method for developing ZnO/TiO2 Core/shell nanoarrays.•Enhanced sensing performance of core/shell compared to pristine ZnO nanoarrays.•UV and external bias ...reduce the working temperature from 350° to 45 °C.•The sensors showed significant sensing performance under light and external bias.
Well-aligned ZnO-TiO2 core–shell nano-arrays (NAs) were synthesized by uniformly coating a thin layer of TiO2 (either ∼ 30 or ∼ 50 nm) on the ZnO NAs. The TiO2-coated ZnO NAs were annealed carefully to preserve the ZnO-TiO2 core–shell NA structure and to limit the formation of any mixed metal oxides (i.e., zinc titanate: ZnxTiOy). The ZnO-TiO2 core–shell NAs acetone gas sensing response was investigated by measuring the current when applying bias voltages ranging between 0.1 and 9 V DC, with and without ultraviolet (UV) illumination. The sensitivity, selectivity, and repeatability at operating temperatures ranging from 45to 350 °C are analyzed and discussed in detail. The ZnO-TiO2 core–shell NAs sensors under UV light illumination significantly improved sensing performance compared to dark conditions. At 45 °C, the 50 nm TiO2-coated ZnO NAs sensor showed a limit of detection (LoD) of 16 ppb under UV illumination, highlighting its utility in applications requiring fast, accurate detection of acetone vapor.
A SiO
2
-coumarin nanohybrid was investigated for its Cu(II) sensing performance in aqueous media, and in comparison with the Cu(II)-selective coumarin used alone. Fluorescence of both coumarin ...itself and the nanohybrid,
λ
ex
/
λ
em
435/481 nm, was selectively quenched by Cu(II) when tested against a range of multivalent cations. The nanohybrid had enhanced Cu(II) sensing properties when compared to the coumarin including (i) improved limit of detection from μM-level (0.48 μM) of Cu(II) using coumarin alone to nM-level (0.033 μM) and (ii) an extended linear detection range of 0.033–260 μM (0.0005–4.1 mg/mL) Cu(II) compared to 0.48–55 μM for the coumarin itself. The lower limit of detection and extended range were achieved with a smaller amount of coumarin and no traces of organic solvents used to help coumarin dissolution. Characterization suggested that under applied test conditions at pH = 5, SiO
2
nanoparticles with negative surface charges adsorbed coumarin and then (when present) Cu(II) ions. The SiO
2
-coumarin nanohybrid was then applied for the determination of Cu(II) levels in aqueous soil extracts reaching over 94% recovery rates when used against the standard soil analysis method by inductively coupled plasma mass spectrometry (ICP-MS).
Graphical Abstract
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.
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•Soil metal concentrations (Cd, Cr, Ni, and Pb) in garden soil were comapred to house age and building material, distance from roads and railway.•Pb concentrations above the Health Investigation Level were recorded in 13% of vegetable gardens.•Pb accumulation was best correlated with the year of construction of the adjoining house and the distance from arterial roads.•Cd accumulation was best correlated with the year of construction of the adjoining house.•Pb and Cd soil concentrations were significantly different in gardens adjacent to wooden houses compared to brick and concrete houses.
The main factors related to Pb and Cd concentrations in vegetable garden soils from Melbourne Australia were house age, building material and distance from the nearest arterial road.
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