Dr Dane Lamb

© 2017 This study investigates the effect of contaminant zinc (Zn) on lead (Pb) bioavailability and bioaccessibility in six contrasting soils spiked with 1500 mg Pb/kg and aged 12 months under laboratory conditions. Zn was added to the soils (7500 mgZn/kg soil) and aged for a further two weeks. In vivo studies were conducted using juvenile swine as a surrogate model for young children. Two compartment pharmacokinetic models were used to analyze the biological response produced by Pb oral solution and spiked soils. Absolute and relative bioavailability of Pb in soils (oral dose of 100 µ g Pb/kg body weight/day) were estimated by comparing them with intravenously administered soluble Pb salt (25 µ g Pb/kg/day) and orally administered the same Pb salt [Pb acetate =(CH 3 COO) 2 Pb·3H 2 O] administered to 3 juvenile pigs per treatment. Lead bioaccessibility was calculated using the in vitro RBALP (i.e. relative bioaccessibility leaching procedure) method. The in vitro results of RBALP were compared to in vivo relative Pb bioavailability to ascertain whether the changes in bioaccessibility correlated with the in vivo data. Although the in vivo Pb relative bioavailability (RB) in all soils except in MLA (Mount Lofty Acidic) revealed an increase (18%¿159%) in the presence of Zn, the in vitro RBALP bioaccessibility results indicated otherwise (1%¿38% decrease). In vivo RB of Pb in MLA declined by 37% in the presence of Zn. However, the RBALP in vitro bioaccessible Pb did not correlate with the relative bioavailabilities of Pb in the juvenile swine dosing experiment. Caution is therefore needed when predicting Pb bioavailability/bioaccessibility in the presence of metal mixtures. The literature contains much information on the correlation of metal and metalloid bioaccessibility with their bioavailability. There is, however, a paucity of studies investigating the effects of other metals on Pb and their IVIVC (in vitro and in vivo correlations). The current study addresses this knowledge gap by assessing in vivoand in vitro bioavailability of Pb in the presence of Zn.

© 2017 Elsevier Ltd Arsenic (As) and zinc (Zn) are common co-contaminants in mining impacted soils. Their interaction on solubility and toxicity when present concurrently is not well understood in natural systems. The aim of this study was to observe their interaction in solubility (soil-solution), bioaccumulation (shoot uptake) and toxicity to cucumber (Cucumis sativa L) conducting 4 weeks pot study in 5 different soils spiked with As (0, 2, 4, 8 to 1024 mg kg -1 ) individually and with Zn at two phytotoxic doses. The As pore-water concentration was significantly reduced (df = 289, Adjusted R 2 = 0.84, p < 0.01) in the presence of Zn in the whole dataset, whereas Zn and Zn 2+ activity in pore-water was reduced significantly only in the two alkaline soils. This outcome may be due to adsorption/surface precipitation or tertiary bridging complexation. No homogenous precipitation of zinc arsenate could be established using electron microscopy, XRD or even equilibrium calculations. For bioaccumulation phase, no significant effect of Zn on As uptake was observed except acidic MG soil whereas, Zn uptake was significantly reduced (p < 0.05) by As in whole dataset. However, an additive response was observed mostly except acidic MG soil. The synergistic response (more than additive) was predominant in this soil for a wide range of inhibition concentration (0¿80%) at both Zn EC10 and EC50 levels. Since additive response is mostly considered in risk assessment for mixtures, precautions should be implemented for assessment of toxicity for As-Zn mixture in acidic soil due to their synergistic response in some soils.

© 2015 Elsevier Ltd. Barite contamination of soil commonly occurs from either barite mining or explorative drilling operations. This work reported in vitro data for barite contaminated soils using the physiologically based extraction test (PBET) methodology. The existence of barite in plant tissue and the possibility of 'biomineralised' zones was also investigated using Scanning Electron Microscopy. Soils with low barium (Ba) concentrations showed a higher proportion of Ba extractability than barite rich samples. Barium uptake to spinach from soil was different between short term spiking studies and field weathered soils. Furthermore, Ba crystals were not evident in spinach tissue or acid digest solutions grown in barium nitrate spiked soils despite high accumulation. Barite was found in the plant digest solutions from barite contaminated soils only. Results indicate that under the conservative assumptions made, a child would need to consume extreme quantities of soil over an extended period to cause chronic health problems.

© 2015 Elsevier Ltd. Recent decades have seen a growing popularity of in vitro bioaccessibility being utilised as a screening tool in human health risk assessment. However the existing bioaccessibility studies only focus on single contaminant. Considering human are likely to ingest multi-contaminants, these contaminants could interact within human gastrointestinal tract which may lead to an increase or decrease in bioaccessibility. In this study, seven different types of soil were spiked with arsenic (As) or cadmium (Cd) and aged for one year. The effects of soil properties on the bioaccessibility were examined. Moreover, the interaction between As and Cd in simulated human digestive system was studied by mixing As-spiked soil with Cd-spiked soil of the same type during bioaccessibility test. Results shows the bioaccessibility of As ranged from 40 ± 2.8 to 95 ± 1.3% in the gastric phase and 16 ± 2.0 to 96 ± 0.8% in the intestinal phase whilst a significant difference was observed between Cd gastric bioaccessibility (72 ± 4.3 to 99 ± 0.8%) and intestinal bioaccessibility (6.2 ± 0.3 to 45 ± 2.7%). Organic carbon, iron oxide and aluminium oxide were key parameters influencing the bioaccessibility of As (gastric and intestinal phases) and Cd (intestinal phase). No interactions between As and Cd during bioaccessibility test were observed in any soils, which indicates As and Cd may age independently and did not interact while being solubilised during bioaccessibility test. Thus additive effect may be proposed when estimating the bioaccessibility of mixtures of independently-aged As and Cd in soils.

© 2015 Elsevier B.V. Arsenic (As) is a mobile and ecotoxic metalloid that is of serious concern to the environment. In this study, As phytotoxicity was studied using a dose-response approach for seven contrasting soils considering 3 end-points (shoot biomass, root elongation and chlorophyll content) and focusing on predictors of toxicity. Root elongation study was carried out for 4days using both Cucumis sativus L. (cucumber) and Triticum aestivum L. (wheat) and shoot end-points with a 4week a pot study using cucumber only. Root elongation of cucumber was a substantially less sensitive indicator to As than data from the 4weeks pot study. Effective concentrations (50%)(EC 50 ) from cucumber root elongation studies were overall 1.6 times higher than the 4week shoot data. Cucumber was however considerably more sensitive to wheat. Given the large discrepancy in phyt otoxicity end points for 7 soils, root elongation data for ecotoxicological assessment should be treated with some caution. Arsenic phytotoxicity was strongly related to the sorption constants of each of the seven soils in our study. Both root elongation and shoot data were related strongly to Freundlich partitioning constants (K f ) (L/kg). Wheat and cucumber root elongation had R 2 values 0.90 and 0.91 respectively, while cucumber shoot data was 0.79. The K f values were related to soil pH and also EC 50 data and, thus, shows that As phytotoxicity in our study was primarily controlled by sorption reactions. The rate of As bioaccumulation to cucumber shoots depended heavily on the soil under consideration. Chlorophyll and carotenoid content of cucumber shoots increased with As content in 3 soils and decreased in other soils.

© 2016 Elsevier B.V. The sorption behavior of cadmium (Cd(II)) and zinc (Zn(II)) on two virgin soils with different pH levels was studied using single metal and competitive dual metal systems. In the single metal system, Zn exhibited a greater affinity for the alkaline soil, as indicated by the Langmuir constant (K L = 8.85 L/kg) compared with Cd (K L = 1.79 L/kg). However, much less sorption of both Zn (K L = 0.19 L/kg) and Cd (K L = 0.07 L/kg) was observed in the acidic soil. The competitive sorption data were modeled using two-metal Freundlich and Langmuir functions. The competition for metal sorption occurred in the alkaline soil only at a higher concentration of the competing metals, whereas the effect was significant even at lower concentrations in the acidic soil. The cumulative amount of both metals sorbed in the soil was similar to that of single metal systems in the studied concentration range, demonstrating that the number of sites available for sorption remained constant irrespective of the competition. This study indicated that Cd might be more mobile in a mixed-metal system than in a single-metal scenario and thus poses a serious ecotoxicological threat. This study is important for assessing the risks and developing management strategies for multiple heavy metal contaminated soils.

© 2015 Elsevier Inc. Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Zn < inf > pw < /inf > ) and free zinc (Zn < sup > 2+ < /sup > ) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50 < inf > pw < /inf > was 450 and 79.2µM for Zn < inf > pw < /inf > and Zn < sup > 2+ < /sup > , respectively. Total added Zn, soil pore water pH (pH < inf > pw < /inf > ) and dissolve organic carbon (DOC) were the best predictors of Zn < inf > pw < /inf > and Zn < sup > 2+ < /sup > in pore-water. The EC10 (total loading) values ranged from 179 to 5214mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pH < inf > ca < /inf > , although pH < inf > w < /inf > and pH < inf > pw < /inf > were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC.

© 2015 Elsevier B.V. This study introduced a patented novel methodological system for automatically analysis of Fourier Transform Infrared Spectrometer (FTIR) spectrum data located at 'fingerprint' region (wavenumber 670-800 cm < sup > -1 < /sup > ), to simultaneously determinate multiple petroleum hydrocarbons (PHs) in real mixture samples. This system includes: an object oriented baseline correction; Band decomposition (curve fitting) method with mathematical optimization; and Artificial Neural Network (ANN) for determination, which is suitable for the characteristics of this IR regions, where the spectra are normally with low signal to noise ratio and high density of peaks. BTEX components are potentially lethal carcinogens and contained in many petroleum products. As a case study, six BTEX components were determinate automatically and simultaneously in mixture vapor samples. The robustness of the BTEX determination was validated using real petroleum samples, and the prediction results were compared with gas chromatography-mass spectrometry (GC-MS).

The sorption of chromium (Cr) species to soil has become the focus of research as it dictates the bioavailability and also the magnitude of toxicity of Cr. The sorption of two environmentally important Cr species [Cr(III) and Cr(VI)] was examined using batch sorption, and the data were fitted to Langmuir and Freundlich adsorption isotherms. The effects of soil properties such as pH, CEC, organic matter (OM), clay, water-extractable SO 4 2- and PO 4 3- , surface charge, and different iron (Fe) fractions of 12 different Australian representative soils on the sorption, and mobility of Cr(III) and Cr(VI) were examined. The amount of sorption as shown by K f was higher for Cr(III) than Cr(VI) in all tested soils. Further, the amount of Cr(III) sorbed increased with an increase in pH, CEC, clay, and OM of soils. Conversely, the chemical properties of soil such as positive charge and Fe (crystalline) had a noticeable influence on the sorption of Cr(VI). Desorption of Cr(VI) occurred rapidly and was greater than desorption of Cr(III) in soils. The mobility of Cr species as estimated by the retardation factor was higher for Cr(VI) than for Cr(III) in all tested soils. These results concurred with the results from leaching experiments which showed higher leaching of Cr(VI) than Cr(III) in both acidic and alkaline soils indicating the higher mobility of Cr(VI) in a wide range of soils. This study demonstrated that Cr(VI) is more mobile and will be bioavailable in soils regardless of soil properties and if not remediated may eventually pose a severe threat to biota. © 2013 Springer Science+Business Media Dordrecht.

As land application becomes one of the important waste utilization and disposal practices, soil is increasingly being seen as a major source of metal(loid)s reaching food chain, mainly through plant uptake and animal transfer. With greater public awareness of the implications of contaminated soils on human and animal health there has been increasing interest in developing technologies to remediate contaminated sites. Bioremediation is a natural process which relies on soil microorganisms and higher plants to alter metal(loid) bioavailability and can be enhanced by addition of organic amendments to soils. Large quantities of organic amendments, such as manure compost, biosolid and municipal solid wastes are used as a source of nutrients and also as a conditioner to improve the physical properties and fertility of soils. These organic amendments that are low in metal(loid)s can be used as a sink for reducing the bioavailability of metal(loid)s in contaminated soils and sediments through their effect on the adsorption, complexation, reduction and volatilization of metal(loid)s. This review examines the mechanisms for the enhanced bioremediation of metal(loid)s by organic amendments and discusses the practical implications in relation to sequestration and bioavailability of metal(loid)s in soils. © 2010 Elsevier B.V.

The effects of pH and Cu loading on the solid/solution partitioning of Cu in a Podosol from south-east Queensland, Australia was examined. Sorption-desorption of Cu exhibited maximum linear distribution coefficients (K D ) at approximately pH 5. Observed decrease in K D values at pH > 5 was attributed to increased solubility of native dissolved organic carbon (DOC) at higher pH and subsequent formation of non-sorbing Cu-DOC complexes. Speciation modelling with the MINTEQA2 code indicated that > 90% of aqueous Cu was present as Cu-DOC complexes at pH > 5.5. The effect of Cu loading was examined with sorption isotherm analysis at pH 5 using solid:solution ratio approaches that were both constant (1:2 and 1:10) and variable. As the solid:solution ratio increased, the proportion of Cu sorbed decreased due to the formation of Cu-DOC complexes. However, this effect was negligible once these Cu-DOC complexes were accounted for via free Cu 2+ sorption isotherms. This indicated that Cu 2+ sorption at concentrations < 0.08 mg/L was described by a K D value of approximately 3000 L/kg. Despite this relatively high K D value for Cu 2+ sorption, the results indicate that Cu-DOC complexes significantly enhance Cu solubility in soils high in DOC. © CSIRO 2005.

The sorption-desorption and leaching behaviour of Cu in a Podosol from south-east Queensland, Australia, was examined. Copper sorption was described by a linear distribution coefficient at low sorption levels (K D Ca¿0 ) of 481 L/kg and a sorption capacity (C S,Max ) of 382 mg/kg. Selective removal of soil organic matter reduced these values by approximately 95%, indicating that Cu was sorbed predominantly to soil organic matter. The K D Ca¿0 and C S,Max values from Cu desorption experiments were 934 L/kg and 516 mg/kg, respectively, which indicates that sorption was not fully reversible. This irreversibility was related to aqueous Cu speciation (modelled with MINTEQA2), showing that aqueous complexes between Cu and dissolved organic carbon (DOC) comprised 28.3-72.8% and 21.3-45.4% of aqueous Cu in the sorption and desorption experiment, respectively. Sorption irreversibility was not evident when the corresponding data was presented as free Cu 2+ isotherms. Both sorption and desorption experiments with free Cu 2+ < 0.2 mg/L were described by a K D Ca¿0 value of approximately 3000 L/kg. Sequential extraction of sorbed Cu indicated that at low concentrations, sorption occurred primarily via specific interactions, with non-specific sorption becoming increasing important at higher concentrations. Desorption of Cu in a column leaching experiment was attributable to exchange of sorbed Cu 2+ with Na + . Leaching with a DOC solution of pH 7 and 135 mg/L greatly enhanced Cu mobility due to the formation of aqueous Cu-DOC complexes. © CSIRO 2005.