Plant growth and heavy meal accumulation characteristics of Spathiphyllum kochii cultured in three soil extractions with and without silicate supplementation.

A hydroponic method was conducted to test whether Spathiphyllum kochii is tolerant to multiple HMs as well as to evaluate whether sodium silicate promotes plant growth and alleviates HM stress mainly by assessing biomass, HM accumulation characteristics and antioxidant enzyme activities (AEAs). Three soil extractions from an uncontaminated soil, a comparable lightly HM-contaminated soil (EnSE), and a comparable heavily HM-contaminated soil (ExSE) with or without 1 mM sodium silicate supplementation were used. S. kochii showed no obvious symptoms when cultured in EnSE and ExSE, indicating that it was a multi-HM-tolerant species. The biomass and photosynthesis followed the order: UnSE > EnSE > ExSE, but the opposite order was found for HM concentration, AEAs, and malondialdehyde content. Silicate had no effects on the growth and HM bioaccumulation characteristics of S. kochii cultured in UnSE but exhibited a novel role in decreasing HM uptake by 13.61-41.51% in EnSE and ExSE, respectively, corresponding upregulated AEAs, and reduced malondialdehyde contents, resulting in increased biomass and alleviating HM stress. The activities of peroxidase and superoxide dismutase were upregulated by an increase in soil extraction HM concentration and further upregulated by silicate supplementation, indicating that they were important mechanisms alleviating HM stress in S. kochii.

Phytoremediation is an economical and environmentally friendly technology for the alleviation of heavy metal (HM)-contaminated soil. Improving bioremediation efficiency is crucial for this kind of technology. Many studies have shown that silicon plays a novel role in plant growth and adversity responses, but studies in the field of phytoremediation are limited. In addition, phytoremediation plant species are usually hyperaccumulators or may be tolerant crops, commercial crops, or wild species from mining areas, and the use of landscape species in phytoremediation is limited. This is the first report on the effects of silicate on the multi-HM bioaccumulation characteristics of a garden plant (Spathiphyllum kochii) cultured in uncontaminated and HM-contaminated soil extractions. This study will broaden phytoremediation species screening and enrich our understanding of the mechanisms by which Si supports the bioremediation of HM-contaminated environments.HIGHLIGHTSS. kochii was a multi-heavy metal-tolerant species.Silicon played a novel role in reducing heavy metal concentrations by 14­40% and 14­42% in shoots and roots, respectively.Silicon upregulated antioxidant enzyme activities to alleviate heavy metal stress in plants.

Assessment of Aqueous Extraction Methods on Extractable Organic Matter and Hydrophobic/Hydrophilic Fractions of Virgin Forest Soils.

The assessment of water-extractable organic matter using an autoclave can provide useful information on physical, chemical, and biological changes within the soil. The present study used virgin forest soils from Chini Forest Reserve, Langkawi Island, and Kenyir Forest Reserve (Malaysia), extracted using different extraction methods. The dissolved organic carbon (DOC), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and ammonium-nitrate content were higher in the autoclave treatments, up to 3.0, 1.3, 1.2, and 1.4 times more than by natural extraction (extracted for 24 h at room temperature). Overall, the highest extractable DOC, TDN, TDP, ammonium and nitrate could be seen under autoclaved conditions 121 °C 2×, up to 146.74 mg C/L, 8.97 mg N/L, 0.23 mg P/L, 5.43 mg N mg/L and 3.47 N mg/L, respectively. The soil extracts became slightly acidic with a higher temperature and longer duration. Similar trends were observed in the humic and nonhumic substances, where different types of soil extract treatments influenced the concentrations of the fractions. Different soil extraction methods can provide further details, thus widening the application of soil extracts, especially in microbes.

Kinetics Growth and Recovery of Valuable Nutrients from Selangor Peat Swamp and Pristine Forest Soils Using Different Extraction Methods as Potential Microalgae Growth Enhancers.

Soil extracts are useful nutrients to enhance the growth of microalgae. Therefore, the present study attempts for the use of virgin soils from Peninsular Malaysia as growth enhancer. Soils collected from Raja Musa Forest Reserve (RMFR) and Ayer Hitam Forest Reserve (AHFR) were treated using different extraction methods. The total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and dissolved organic carbon (DOC) concentrations in the autoclave methods were relatively higher than natural extraction with up to 132.0 mg N/L, 10.7 mg P/L, and 2629 mg C/L, respectively for RMFR. The results of TDN, TDP, and DOC suggested that the best extraction methods are autoclaved at 121 °C twice with increasing 87%, 84%, and 95%, respectively. Chlorella vulgaris TRG 4C dominated the growth at 121 °C twice extraction method in the RMRF and AHRF samples, with increasing 54.3% and 14%, respectively. The specific growth rate (µ) of both microalgae were relatively higher, 0.23 d-1 in the Ayer Hitam Soil. This extract served well as a microalgal growth promoter, reducing the cost and the needs for synthetic medium. Mass production of microalgae as aquatic feed will be attempted eventually. The high recovery rate of nutrients has a huge potential to serve as a growth promoter for microalgae.

Analytical method development and validation for the quantification of metaldehyde in soil.

Previously published methods for the analysis of metaldehyde were adapted for its reliable quantification in soil extracts. Varied methanol-water extraction solvents were trialed, but the use of pure methanol proved to be the most reliable approach for the scaled down methodology. Analysis of metaldehyde was done using LC-MS. Initially the method had problems with matrix suppression of the signal. The method was therefore further developed to overcome this challenge to avoid the costs and time demands of laborious clean-up protocols. This modification to the method involved use of the BEH Phenyl column instead of the C18 column initially used, and optimization of the gradient flow of the mobile phase. The optimized LC-MS method was validated and used for further research applications. In brief,•We investigated the recovery of metaldehyde from spiked soil samples.•The optimized LC-MS method achieved acceptable metaldehyde recoveries (100-132%, 109% on average) for a range of soil types.•The optimized method was suitable for high through-put analyzes.

Determination of chlorothalonil metabolites in soil and water samples.

Pesticide metabolites are frequently detected in groundwater at concentrations often exceeding those of their parent pesticides. A well-known example is the metabolites of chlorothalonil, a non-systematic, broad spectrum fungicide. Some of the chlorothalonil metabolites occur frequently and at elevated concentrations in groundwater, which is why the use of chlorothalonil was recently banned in the European Union. To estimate the long-term evolution of the concentration of the chlorothalonil metabolites in groundwater after this ban, it is important to know if metabolite residues in soil and unsaturated zone can affect the concentrations in groundwater. We developed and validated a method for the determination of 5 chlorothalonil metabolites in soil (R471811, R417888, SYN507900, SYN548580 and R611968), including those which are frequently detected in groundwater. The developed protocols, based on a solid phase extraction approach (for R471811, R417888, SYN507900, SYN548580) or a QuEChERS approach (for R611968) followed by UHPLC-MS/MS analysis, provided excellent sensitivity (LOQ of 0.5 µg/kg for all metabolites), precision (RSD<10 % at low, medium and high concentrations) and accuracy (84-115 %). In addition, we developed a simple but highly sensitive (LOQ of 5-10 ng/L) direct-injection method for the analysis of these 5 metabolites in water to compare their occurrence in soil and groundwater. The application of these methods to agricultural soil samples and groundwater samples showed that the detection frequency of the 5 chlorothalonil metabolites in soil and groundwater seems to be inversed and dependent on their sorption coefficient. The latter might control the amount of the chlorothalonil metabolites which is retained in the soil or which leaches towards groundwater. Our results provide insights to estimate the retention of the different chlorothalonil metabolites in soil and unsaturated zone and therefore, to assess the influence of the soil and unsaturated zone on the long-term concentration evolution of these metabolites in groundwater.

Liming impacts barley yield over a wide concentration range of soil exchangeable cations.

Liming has widespread and significant impacts on soil processes and crop responses. The aim of this study was to describe the relationships between exchangeable cation concentrations in soil and the relative yield of spring barley. The hypothesis was that yield is restricted by the concentration of a single exchangeable cation in the soil. For simplicity, we focused on spring barley which was grown in nine years of a long-term experiment at two sites (Rothamsted and Woburn). Four liming rates were applied and in each year the relative yield (RY) and the concentrations of exchangeable cations were assessed. Liming had highly significant effects on the concentrations of most exchangeable cations, except for Cu and K. There were significant negative relationships (either linear or exponential) between the exchangeable concentrations of Mn, Cd, Cr, Al, Fe, Cu, Co, Zn and Ni in soil and soil pH. The relationships between RY and the concentrations of selected exchangeable cations (Mn, Ca and Al) were described well using log-logistic relationships. For these cations a significant site effect was probably due to fundamental differences in soil properties. At both sites the concentrations of exchangeable soil Al were excessive (> 7.5 mg kg-1) and were most likely responsible for reduced barley yields (where RY ≤ 0.5) with soil acidification. At Rothamsted barley yield was non-limited (where RY ≥ 1) at soil exchangeable Mn concentrations (up to 417 mg kg-1) greater than previously considered toxic, which requires further evaluation of critical Mn concentrations. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s10705-020-10117-2) contains supplementary material, which is available to authorized users.

A Sensitive Single Particle-ICP-MS Method for CeO2 Nanoparticles Analysis in Soil during Aging Process.

The increasing prevalence of products that incorporate engineered nanoparticles (ENPs) has prompted efforts to investigate the potential release, environmental fate, and exposure of the ENPs. However, the investigation of cerium dioxide nanoparticles (CeO2 NPs) in soil has remained limited, owing to the analytical challenge from the soil's complex nature. In this study, this challenge was overcome by applying a novel single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) methodology to detect CeO2 NPs extracted from soil, utilizing tetrasodium pyrophosphate (TSPP) aqueous solution as an extractant. This method is highly sensitive for determining CeO2 NPs in soil, with detection limits of size and concentration of 15 nm and 194 NPs mL-1, respectively. Extraction efficiency was sufficient in the tested TSPP concentration range from 1 mM to 10 mM at a soil-to-extractant ratio 1:100 (g mL-1) for the extraction of CeO2 NPs from the soil spiked with CeO2 NPs. The aging study demonstrated that particle size, size distribution, and particle concentration underwent no significant change in the aged soils for a short period of one month. This study showed an efficient method capable of extracting and accurately determining CeO2 NPs in soil matrices. The method can serve as a useful tool for nanoparticle analysis in routine soil tests and soil research.

Predicting the modifying effect of soils on arsenic phytotoxicity and phytoaccumulation using soil properties or soil extraction methods.

Soils have the ability to modify contaminant bioavailability and toxicity. Prediction the modifying effect of soil on arsenic phytoaccumulation and phytoavailability using either soil property data or soil chemical extraction data in risk assessment of contaminated soil is highly desirable. In this study, plant bioassays important to ecological receptors, were conducted with 20 soils with a wide range in chemical and physical soil properties to determine the relationships between As measured by soil chemical extraction (soil pore water, Bray-1, sodium phosphate solution, hydroxylamine hydrochloride, and acid ammonium oxalate) or soil physico/chemical properties on arsenic phytotoxicity and phytoaccumulation. Soil pore water As and Bray-1 extracted As were significantly (P < 0.01) correlated with lettuce tissue As and those extractants and sodium phosphate were correlated with ryegrass tissue As. Hydroxylamine and acid ammonium oxalate extractions did not correlate with plant bioassay endpoints. Simple regression results showed that lettuce tissue relative dry matter growth (RDMG) was inversely related to tissue As concentration (r2 = 0.85, P < 0.01), with no significant relationship for ryegrass. Soil clay exhibited strong adsorption for As and significantly reduce tissue As for lettuce and ryegrass. In addition to clay content, reactive aluminum oxide (AlOx), reactive Fe oxide (FeOx) and eCEC was inversely related to ryegrass tissue As. Multiple regression equation was strongly predictive (r2 = 0.83) for ryegrass tissue As (log transformed) using soil AlOx, organic matter, pH, and eCEC as variables. Soil properties can greatly reduce contaminant phytoavailability, plant exposure and risk, which should be considered when assessing contaminant exposure and site-specific risk in As-contaminated soils.

A field assessment of bauxite residue rehabilitation strategies.

Bauxite residue, the by-product of the alumina industry, is mainly stored in land-based bauxite residue disposal areas (BRDAs). Environmental concern has been raised due to the large volumes in stockpile, the high alkalinity of the material, as well as the presence of elevated concentrations of trace elements. If not adequately managed, BRDAs can act as a source of pollution. In order to minimize the environmental risk, revegetation is implemented to stabilize the residue against water and wind erosion. Currently, two main approaches are used: the use of amendments or the installation of a capping layer. However, few studies evaluating the long-term success and self-sustainability of the rehabilitation programs have been published. A series of field-established rehabilitation strategies reflecting both direct revegetation and revegetation on capping layer were assessed in terms of both soil and plant quality. Soil physico-chemical properties, including pseudo-total and plant-available fractions of nutrients and trace elements, were determined over a summer and winter seasons and aerial portions of vegetation were analysed for nutrients and trace elements. Failure to adequately lower alkalinity remains the major constraint to long-term rehabilitation success of bauxite residue. This is evidenced from poor soil properties in unamended residue and in residue capped with a shallow soil layer, as well from vegetation displaying excessive concentrations of certain elements. Certain elements exceeded typical ranges for non-contaminated soils (i.e. Cr, Fe, Na, Ni and V), with some showing excessive plant-available fractions (i.e. of Al, As, Cr, Hg and V). Vegetation analysis found excessive uptake of some elements (i.e. of Al, Na, Fe, Cr and V). Future attempts for bauxite residue rehabilitation should include both gypsum and organic amendments, while a capping layer may only be effective if either a deep layer (>1 m) is installed or if the underlying residue is sufficiently treated prior to capping.

Mitochondrial DNA Extraction from Burial Soil Samples at Incremental Distances: A Preliminary Study.

Preservation variance of soil DNA is neglected in the literature, and exceptional cases exaggerate amplification capabilities. This study sought to amplify a short mitochondrial fragment (212 bp) specific to Sus scrofa domesticus from the soil surrounding decomposing pig remains from an open-air locale. Samples collected above the body at incremental distances after 145 days of initial placement yielded pig DNA. A secondary sampling was collected in 2017, approximately 768 days after burial. Inhibition tests corroborated that pig DNA was no longer present in the soil resulting in a loss of original DNA between 145 and 768 days. The results provide evidence that genetic material leaches out radially from the source and DNA fragments longer than 200 bp do not persist in soil for a relatively short timeframe in western Montana. The conclusions support the collection of soil in crime scene investigation procedures within the first few months of decomposition.

A two-stage extraction procedure for insensitive munition (IM) explosive compounds in soils.

The Department of Defense (DoD) is developing a new category of insensitive munitions (IMs) that are more resistant to detonation or promulgation from external stimuli than traditional munition formulations. The new explosive constituent compounds are 2,4-dinitroanisole (DNAN), nitroguanidine (NQ), and nitrotriazolone (NTO). The production and use of IM formulations may result in interaction of IM component compounds with soil. The chemical properties of these IM compounds present unique challenges for extraction from environmental matrices such as soil. A two-stage extraction procedure was developed and tested using several soil types amended with known concentrations of IM compounds. This procedure incorporates both an acidified phase and an organic phase to account for the chemical properties of the IM compounds. The method detection limits (MDLs) for all IM compounds in all soil types were <5 mg/kg and met non-regulatory risk-based Regional Screening Level (RSL) criteria for soil proposed by the U.S. Army Public Health Center. At defined environmentally relevant concentrations, the average recovery of each IM compound in each soil type was consistent and greater than 85%. The two-stage extraction method decreased the influence of soil composition on IM compound recovery. UV analysis of NTO established an isosbestic point based on varied pH at a detection wavelength of 341 nm. The two-stage soil extraction method is equally effective for traditional munition compounds, a potentially important point when examining soils exposed to both traditional and insensitive munitions.

Selenium speciation and extractability in Dutch agricultural soils.

The study aimed to understand selenium (Se) speciation and extractability in Dutch agricultural soils. Top soil samples were taken from 42 grassland fields and 41 arable land fields in the Netherlands. Total Se contents measured in aqua regia were between 0.12 and 1.97 mg kg(-1) (on average 0.58 mg kg(-1)). Organic Se after NaOCl oxidation-extraction accounted for on average 82% of total Se, whereas inorganic selenite (selenate was not measurable) measured in ammonium oxalate extraction using HPLC-ICP-MS accounted for on average 5% of total Se. The predominance of organic Se in the soils is supported by the positive correlations between total Se (aqua regia) and total soil organic matter content, and Se and organic C content in all the other extractions performed in this study. The amount of Se extracted followed the order of aqua regia > 1 M NaOCl (pH8) > 0.1 M NaOH>ammonium oxalate (pH3) > hot water>0.43 M HNO3 > 0.01 M CaCl2. None of these extractions selectively extracts only inorganic Se, and relative to other extractions 0.43 M HNO3 extraction contains the lowest fraction of organic Se, followed by ammonium oxalate extraction. In the 0.1M NaOH extraction, the hydrophobic neutral (HON) fraction of soil organic matter is richer in Se than in the hydrophilic (Hy) and humic acid (HA) fractions. The organic matter extracted in 0.01 M CaCl2 and hot water is in general richer in Se compared to the organic matter extracted in 0.1M NaOH, and other extractions (HNO3, ammonium oxalate, NaOCl, and aqua regia). Although the extractability of Se follows to a large extent the extractability of soil organic carbon, there is several time variations in the Se to organic C ratios, reflecting the changes in composition of organic matter extracted.

Persistence of heterorhabditis infective juveniles in soil: comparison of extraction and infectivity measurements.

The persistence of Heterorhabditis megidis in soil was studied over a 4-week period. On days 0, 2, 14, and 28, infective juveniles (IJ) were extracted by centrifugal flotation, Baermann funnel, and baiting of soil with Tenebrio molitor larvae, which were then dissected. Extraction efficiencies on day 0 were 82% by centrifugal flotation, 56% by Baermann funnel, and 19.8% by bait insect. The relative efficiency of the three methods changed over time. The relationship between the density of nematodes in the soil and the proportion recovered by dissection was non-linear. Up to a dose of approximately 60 IJ/insect, less than 12% became established, while at higher doses (up to 200 IJ/insect) the invasion efficiency was 23%. Mortality of bait insects increased from day 0 to day 2, but decreased to day 28. A novel method of assessing soil pathogenicity by preparing a soil density series and calculating the dose of soil or IJ that kills 50% of the bait insects gave a similar pattern. This method is recommended as a means of tracking changes in pathogenicity over time when bait insect mortality in undiluted soil is at or near 100%. Two methods of preparing a series of Heterorhabditis IJ densities in soil, either by diluting the soil itself with IJ-free soil or by adding diluted suspensions of IJ to the soil, resulted in the same bait insect mortalities.

Validation of user- and environmentally friendly extraction and clean-up methods for compound-specific stable carbon isotope analysis of organochlorine pesticides and their metabolites in soils.

In order to evaluate the potential of compound-specific stable carbon isotope analysis (CSIA) for tracking organochlorine pesticides in soil systems, sample pre-treatment methods have to be developed, which can provide recoveries sufficient for low detection limits without altering the isotope ratio of the target compounds. In this study we tested the compatibility of CSIA with user- and environmentally friendly extraction methods, including the Quick, Easy, Cheap, Effective, Rugged and Safe procedure (QuEChERS), Ultrasonic Assisted Extraction (USE) and Focused Ultrasonic Extraction (FUSE), as well as clean-up methods, including sulfuric acid clean-up and Florisil(®) column chromatography for hexachlorocyclohexanes (HCHs), p,p'-dichlorodiphenyltrichloroethane (DDT) and their environmental metabolites (chlorinated benzenes, dichlorodiphenyldichloroethylene - DDE and dichlorodiphenyldichloroethane - DDD) in soils. We optimized the extraction methods for maximum recovery and pre-concentration. At optimal conditions, all extraction methods and clean-up procedures, as well as the pre-concentration of the extract by solvent evaporation, led to insignificant changes in carbon isotope ratios of the target compounds. We modified the USE procedure to increase the volume of withdrawn organic extract, resulting in a higher pre-concentration of the target compounds by the subsequent solvent evaporation step. This Modified Ultrasonic Assisted Extraction (MUSE) was the most suitable procedure, and it was validated for the determination of carbon isotope ratios of the target compounds using two different types of soil matrices. The method could be applied to analyze carbon isotope ratios of HCHs, DDT, and their chlorinated metabolites in soil samples with concentrations ranging from 0.3 to 0.8mg/kg. The analytical uncertainty of MUSE, incorporating both accuracy and precision, was ≤0.4‰.

On-matrix derivatization extraction of chemical weapons convention relevant alcohols from soil.

Present study deals with the on-matrix derivatization-extraction of aminoalcohols and thiodiglycols, which are important precursors and/or degradation products of VX analogues and vesicants class of chemical warfare agents (CWAs). The method involved hexamethyldisilazane (HMDS) mediated in situ silylation of analytes on the soil. Subsequent extraction and gas chromatography-mass spectrometry analysis of derivatized analytes offered better recoveries in comparison to the procedure recommended by the Organization for the Prohibition of Chemical Weapons (OPCW). Various experimental conditions such as extraction solvent, reagent and catalyst amount, reaction time and temperature were optimized. Best recoveries of analytes ranging from 45% to 103% were obtained with DCM solvent containing 5%, v/v HMDS and 0.01%, w/v iodine as catalyst. The limits of detection (LOD) and limit of quantification (LOQ) with selected analytes ranged from 8 to 277 and 21 to 665ngmL(-1), respectively, in selected ion monitoring mode.

Risk assessment for Cd, Cu, Pb and Zn in urban soils: chemical availability as the central concept.

To assess the geochemical reactivity and oral bioaccessibility of Cd, Cu, Pb and Zn in urban soils from the Porto area, four extractions were performed including Aqua Regia (AR; pseudototal), 0.43 M HNO3 (reactive), 0.01 M CaCl2 (available), and 0.4 M glycine at pH = 1.5, SBET method (oral bioaccessible pool). Oral bioaccessibility in urban soils was higher than in samples from rural, industrial and mining areas which is most likely related to sources of metals and parent materials of corresponding soils. The availability and reactivity were described well by non-linear Freundlich-type equations when considering differences in soil properties. The resulting empirical models are able to predict availability and reactivity and can be used to improve the accuracy of risk assessment. Furthermore, a close 1:1 relationship exists between results from the 0.43 M HNO3 method and the SBET method which substantially facilitates risk assessment procedures and reduces analytical costs.