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To assess the feasibility of recovering water from the unsaturated zone, the soil data from this zone at three sites in an agricultural research station in Kuwait and the meteorological data from the station at the nearby location were analysed to investigate the variation of soil properties with depth and any relationship that might exist between these and some of the meteorological parameters. Automatic sensors were set at several depths within the three boreholes installed at the sites, to record the soil water content, temperature, and electrical conductivity (EC) at one-hour intervals. The results of the grain size analysis of the drill cuttings from different depths of these boreholes were used to determine the lithology of the sediment sequence penetrated. The extracts from the drill cuttings were chemically analysed. Graphical and statistical methods were used for the analysis of these data. It was concluded that down to the depth investigated (25 m), the depth and meteorology did not have much influence on the quantity and quality of the soil water content. A continuous increase in the soil water content with time was, however, observed over the monitoring period that was surmised to be related to the infiltration of winter rain and the irrigation water that might lead to water mounding. It was further concluded that there would be sufficient quantity and quality of soil water in the unsaturated zone of the study area that could be profitably recovered. [ABSTRACT FROM AUTHOR]

Outbreaks of Enterohemorrhagic Escherichia coli (EHEC), Salmonella enterica, and Listeria monocytogenes linked to fresh produce consumption pose significant food safety concerns. These pathogens can contaminate pre-harvest produce through various routes, including contaminated water. Soil physicochemical properties and flooding can influence pathogen survival in soils. We investigated survival of EHEC, S. enterica, and L. monocytogenes in soil extracts designed to represent soils with stagnant water. We hypothesized pathogen survival would be influenced by soil extract nutrient levels and the presence of native microbes. A chemical analysis revealed higher levels of total nitrogen, phosphorus, and carbon in high-nutrient soil extracts compared to low-nutrient extracts. Pathogen survival was enhanced in high-nutrient, sterile soil extracts, while the presence of native microbes reduced pathogen numbers. A microbiome analysis showed greater diversity in low-nutrient soil extracts, with distinct microbial compositions between extract types. Our findings highlight the importance of soil nutrient composition and microbial dynamics in influencing pathogen behavior. Given key soil parameters, a long short-term memory model (LSTM) effectively predicted pathogen survival. Integrating these factors can aid in developing predictive models for pathogen persistence in agricultural systems. Overall, our study contributes to understanding the complex interplay in agricultural ecosystems, facilitating informed decision-making for crop production and food safety enhancement. [ABSTRACT FROM AUTHOR]

Outbreaks of Enterohemorrhagic Escherichia coli (EHEC), Salmonella enterica, and Listeria monocytogenes linked to fresh produce consumption pose significant food safety concerns. These pathogens can contaminate pre-harvest produce through various routes, including contaminated water. Soil physicochemical properties and flooding can influence pathogen survival in soils. We investigated survival of EHEC, S. enterica, and L. monocytogenes in soil extracts designed to represent soils with stagnant water. We hypothesized pathogen survival would be influenced by soil extract nutrient levels and the presence of native microbes. A chemical analysis revealed higher levels of total nitrogen, phosphorus, and carbon in high-nutrient soil extracts compared to low-nutrient extracts. Pathogen survival was enhanced in high-nutrient, sterile soil extracts, while the presence of native microbes reduced pathogen numbers. A microbiome analysis showed greater diversity in low-nutrient soil extracts, with distinct microbial compositions between extract types. Our findings highlight the importance of soil nutrient composition and microbial dynamics in influencing pathogen behavior. Given key soil parameters, a long short-term memory model (LSTM) effectively predicted pathogen survival. Integrating these factors can aid in developing predictive models for pathogen persistence in agricultural systems. Overall, our study contributes to understanding the complex interplay in agricultural ecosystems, facilitating informed decision-making for crop production and food safety enhancement.

The accurate detection of Cd2+ and Pb2+ in soils by square-wave anodic stripping voltammetry (SWASV) faces great challenges because the interaction between multiple heavy metal ions (HMIs) interferes seriously with their SWASV signals. To detect Cd2+ and Pb2+ by SWASV with high accuracy, an overlooked but informative signal, i.e., stripping current peak area, was employed and combined with chemometric methods to suppress the above mutual interference. An easy-to-prepare electrode, i.e., in-site electroplating bismuth film modified glassy carbon electrode, was used to sense the multiple HMIs. Two machine learning algorithms, including SVR and PLSR, were used to establish the detection models of Cd2+ and Pb2+. In addition, this study developed a homemade algorithm to automatically acquire the stripping peak heights and stripping peak areas of Zn2+, Cd2+, Pb2+, Bi3+, and Cu2+, which acted as the inputs of machine learning models. Then, the detection performance of various SVR and PLSR models were compared based on the R2 and RMSE values of the validation dataset. Results showed that the SVR detection models established by the algorithmically acquired peak areas presented the best stability and accuracy for detecting both Cd2+ and Pb2+ concentrations under the existence of Zn2+ and Cu2+. The R2 and RMSE values of the SVR models built using the peak heights of HMIs acquired by electrochemical workstation control software (Imanu-SVR) were 0.7650 and 5.3916 μg/L for Cd2+, and 0.8791 and 20.0015 μg/L for Pb2+, respectively; the R2 and RMSE values of the SVR models built using the peak area automatically acquired by the developed algorithm (Aalgo-SVR) were 0.9204 and 2.9906 μg/L for Cd2+, and 0.9756 and 13.1574 μg/L for Pb2+, respectively. More importantly, the detection results of the proposed method in real soil extracts for Cd2+ and Pb2+ concentrations were close to those of ICP-MS, verifying its practicability. This study provides a new solution for the accurate detection of targeted heavy metals under the co-existence of multiple HMIs by the SWASV method. [ABSTRACT FROM AUTHOR]

Due to enhancement of industrial growth and urbanization, soil contamination is increasing prominently. Therefore, it is important to examine possible adverse effects of industrial waste. Soil samples were might to be polluted with several heavy-metals and pesticides. Gas chromatographic results showed occurrence of high-level of organochlorine and organophosphate pesticides in studied soil samples. Genotoxicity of soil extracts was assessed using environmental-risk assessment models. Soil samples were extracted in hexane and dichloromethane solvents and were evaluated for genotoxic potential by prokaryotic (Ames test, plasmid nicking assay and E. coli K-12 DNA repair defective mutants) and eukaryotic (Allium cepa root chromosomal aberration and Vigna radiata seed-germination test) bioassays. Strain TA98 was found the most susceptible among soil extracts. The mutagenicity of hexane soil extract from wastewater irrigation was found to be higher than that of DCM samples in terms of mutagenic index, mutagenic potential, and induction factor for Ames strains. The damage in DNA repair defective mutants of hexane extracts were found higher compared to DCM extracts at dose of 20 μl/ml of culture. Survival in polA, lexA and recA mutants were 39%, 47% and 55% while treated with hexane extract. Allium cepa test, mitotic index was decreased in dose-dependent way and various kinds of chromosomal aberrations were found. Vigna radiata seeds germination and other parameters were also affected when treated with wastewater irrigated (WWI) soil. Oxidative stress in V. radiata roots were also showed under CLS microscope. Genotoxicity of WWI soil extract was also confirmed by plasmid nicking test. Our study provides possible explanation for the assessment of potential health and environmental hazards of the industrial region.

Humic substances are increasingly used as biostimulants in agriculture because of their supposed effects on nutrient uptake and crop yield. The objective of this study was to assess the effect of fulvic acid (FA) and humic acid (HA) addition with and without fertilization (N, P, K, S, and Ca) on (i) grass yield (Poa trivialis) and nutrient uptake and (ii) composition of soil porewater and 0.01 M CaCl2 soil extracts. Therefore, a pot experiment was performed using a loamy soil and a non-calcareous sandy soil. Fertilization increased N and P uptake and grass yield but there was no effect of FA or HA application (200 mg C kg−1 soil) regardless of whether N or P was the growth limiting nutrient. Nutrient availability was assessed in soil pore water samples extracted by centrifugating moist soil and by 0.01 M CaCl2 extracts of oven-dried soil. HA and FA had no effect on the availability of NO3 or ortho-P, neither in soil porewater nor in 0.01 M CaCl2 soil extracts. Fertilization led to an increase in 0.01 M CaCl2-extractable ortho-P but, remarkably, to a decrease in ortho-P and Dissolved Organic Carbon (DOC) concentrations in soil pore water samples. This discrepancy was explained by the higher ionic strength of pore water in the fertilized soils, which caused the pH to drop by 0.2 to 0.4 units and thereby stimulated adsorption of ortho-P and DOC to reactive soil minerals. Such salt-induced effects do not occur in 0.01 M CaCl2 soil extracts where the ionic strength is nearly constant. [ABSTRACT FROM AUTHOR]

The accurate detection of Cd2+ and Pb2+ in soils by square-wave anodic stripping voltammetry (SWASV) faces great challenges because the interaction between multiple heavy metal ions (HMIs) interferes seriously with their SWASV signals. To detect Cd2+ and Pb2+ by SWASV with high accuracy, an overlooked but informative signal, i.e., stripping current peak area, was employed and combined with chemometric methods to suppress the above mutual interference. An easy-to-prepare electrode, i.e., in-site electroplating bismuth film modified glassy carbon electrode, was used to sense the multiple HMIs. Two machine learning algorithms, including SVR and PLSR, were used to establish the detection models of Cd2+ and Pb2+. In addition, this study developed a homemade algorithm to automatically acquire the stripping peak heights and stripping peak areas of Zn2+, Cd2+, Pb2+, Bi3+, and Cu2+, which acted as the inputs of machine learning models. Then, the detection performance of various SVR and PLSR models were compared based on the R2 and RMSE values of the validation dataset. Results showed that the SVR detection models established by the algorithmically acquired peak areas presented the best stability and accuracy for detecting both Cd2+ and Pb2+ concentrations under the existence of Zn2+ and Cu2+. The R2 and RMSE values of the SVR models built using the peak heights of HMIs acquired by electrochemical workstation control software (Imanu-SVR) were 0.7650 and 5.3916 μg/L for Cd2+, and 0.8791 and 20.0015 μg/L for Pb2+, respectively; the R2 and RMSE values of the SVR models built using the peak area automatically acquired by the developed algorithm (Aalgo-SVR) were 0.9204 and 2.9906 μg/L for Cd2+, and 0.9756 and 13.1574 μg/L for Pb2+, respectively. More importantly, the detection results of the proposed method in real soil extracts for Cd2+ and Pb2+ concentrations were close to those of ICP-MS, verifying its practicability. This study provides a new solution for the accurate detection of targeted heavy metals under the co-existence of multiple HMIs by the SWASV method.

With the intensification of industrial development and urbanization, soil pollution is increasingly prominent. Therefore, the potential adverse effects caused by industrial activities need to be investigated. In this study, nine soil samples were collected from the industrial district of Nanjing, China, and the heavy metal concentrations were analyzed. Ambient severity of health (ASI) and ambient severity of ecology (ASII) caused by heavy metals in soil extracts were also evaluated via the multi-media environmental goals (MEG). The environmental risk assessment model was used to assess the health risk of soil extracts. The toxicity of soil extracts was diagnosed for wheat and Vicia faba. The results indicate that the contents of heavy metals were significantly different among the nine soil samples and mass concentration of heavy metals were as followed: Pb > Mn > As > Zn > Cd. Except for CK and S9, the total health impact of all sampling sites were greater than 1. Also, the total ecological hazard degrees of the five heavy metals were all greater than 1, which showed that the soil extracts were harmful to human health and ecological environment. According to the risk characterization model, the carcinogen risk of soil extracts was 1 to 10 orders of magnitude higher than that of non-carcinogens. Drinking water intake was the most direct and primary exposure route. In addition, the ecotoxicological results indicated that with the increase of heavy metal concentration, the activity of amylase (AMS) decreased, while the activity of peroxide (POD) increased, indicating that the soil extracts were toxic to V. faba. The micronucleus rates of V. faba root tips in the sampling soils were significantly higher compared with the control group, reflecting the higher genotoxicity. Our study provides theoretical support for the evaluation of potential health and ecological risks in this industrial district. [ABSTRACT FROM AUTHOR]

In order to investigate the allelopathy of alfalfa（Medicago sativa L.）on seed germination and growth of hollyhock（Althaea rosea Cavan）, the surface layer soil（5~10 cm）at the alfalfa rhizosphere（R）and 20, 40 cm, and 60 cm away from the alfalfa rhizosphere（D20, D40, D60, respectively）were collected. The contents of allelochemicals in soil extracts of these samples were detected by high performance liquid chromatography（HPLC）. The effects of different soil extracts on the seed germination of hollyhock were studied using a bioassay method, and physiological and ecological indexes such as biomass, chlorophyll, malondialdehyde（MDA）, and soluble sugar of hollyhock under intercropping conditions were determined by pot experiment. The results showed that the contents of five organic acids were highest at the alfalfa rhizosphere, and decreased gradually with increasing distance. Compared with the control, under R treatment, the germination percentage and germination index decreased by 6.23% and 31.32%, respectively; The root length and seedling length decreased by 56.11% and 48.94%, respectively. The results of the pot experiment showed that the intercropping of alfalfa and hollyhock significantly inhibited the aboveground and underground biomass of the hollyhock by 8.01% and 23.99%, respectively, which could also decrease the chlorophyll content, and increase the MDA content and soluble protein content. The study indicates that alfalfa has an obvious allelopathic effect on hollyhock, and should not be planted too densely, keeping at least 60 cm spacing. [ABSTRACT FROM AUTHOR]

Chromium speciation by spectrophotometric determination of hexavalent chromium (Cr(VI)) with diphenylcarbazide (DPC) has several problems. These include: (1) the inability to directly detect trivalent chromium (Cr(III)) with DPC, (2) positive interference in Cr(VI) determination by other metal cations and (3) negative interference by any reducing agent present in the sample. These are addressed with an ion transfer device (ITD) in a flow injection analysis system. We previously developed the ITD for electrodialytic separations. Here we separate oppositely charged Cr(III) and Cr(VI) species by the ITD into two different acceptor solutions within ~5 s. The acceptor solutions consist of buffered H 2 O 2 to oxidize the Cr(III) to Cr(VI). Then DPC is added to either acceptor to measure Cr(III) and Cr(VI) spectrophotometrically. The system was optimized to provide the same response for Cr(VI) and Cr(III) with limits of detection (LODs, S/N=3) of 0.5 μg L -1 for each and a throughput rate of 30 samples h -1 . The ITD separation was also effective for matrix isolation and reduction of interferences. Potential cationic interferences were not transferred into the anionic Cr(VI) acceptor stream. Much of the organic compounds in soil extracts were also eliminated as evidenced from standard addition and recovery studies. [ABSTRACT FROM AUTHOR]

Reliable estimates of metal speciation are critical for predicting metal bioavailability and the toxicological effects of metal mixtures in the soil environment; however, simultaneous measurements of metal free ion activities in complex matrices pose a challenge. Although speciation models maybe useful, the uncertainty of metal binding to natural organic matter requires that such models be validated with empirical data. In this study, an ion-exchange resin technique (IET) was adapted for the analysis ofCu2+, Ni2+ and Zn2+in soil extracts. The analysis was performed with three different soil types spiked with single and multiple metal additions to obtain a range of metal concentrations and combinations. Method detection limits of 0.006, 0.04 and 0.05 mM for Cu2+, Ni2+ and Zn2+ were achieved. The values obtained by IET were comparable with those estimated byVisual MINTEQ, givinga root mean squared error of0.21, 0.30 and 0.34 (n= 30) for the Cu, Ni and Zn data. The Cu2+ activities obtained by IET were within an order of magnitude of those obtained by a Cu ion-selective electrode, being on average 6-fold greater, with better agreement occurring in samples having lower organic matter contents. The resulting soil metal speciation data revealed that the partitioning of soil Cu to the potentially bioavailable Cu2+ pool differed in the binary mixture with Ni compared with the single-metal Cu treatments. These data can be used to assess metal bioavailability and aid in the interpretation of ecotoxicological effects observed in soils where multiple metals are a concern. [ABSTRACT FROM AUTHOR]

This study evaluated multiple endpoints of algal assays to identify sensitive and easy to use endpoints that could be applied to evaluate algal toxicity in metal-polluted soil extracts. Soil algae play an important role in trophic levels; thus, Chlorococcum infusionum was selected as the test species. Soil extracts were used because they might help identify potential soil retention and ecological hazards caused by pollutants that are present in the soil aqueous phase. The multi-endpoints measured were growth yield, photosynthetic activities, and cell viabilities. Nine parameters were measured to evaluate photosynthetic activity; namely, specific energy fluxes per quinone A-reducing photosystem II reaction center (absorption flux, trapped energy flux, electron transport flux, and dissipated energy flux per reaction center), quantum yields (maximum quantum yield of primary photochemistry, quantum yield of electron transport, quantum yield of energy dissipation, and average quantum yield of primary photochemistry), and the blockage of electron transfer from the reaction center to the quinone pool. Cell viability was evaluated by measuring cell size, cell granularity, and the autofluorescence of chlorophyll using flow cytometry. The results showed that heavy metals reduced growth yield, cell viability, and the photosynthetic activity of C. infusionum in soil extracts. Out of the 13 tested endpoints, the blockage of electron transfer from the reaction center to the quinone pool and cell size represented the most sensitive endpoints. We propose that both endpoints should be measured, along with conventional growth yield, to determine the effect of soil pollutants and to lower pollutant concentrations in soils. [ABSTRACT FROM AUTHOR]

A novel method based on high-performance ion chromatography inductively coupled plasma mass spectrometry employing strong anion exchange chromatography with HNO3 gradient elution for simultaneous analysis of orthophosphate and myo-inositol hexakisphosphate (IP6) in soil solution and plant extracts is presented. As inductively coupled plasma mass spectrometry analysis of phosphorus at m/ z 31 is hampered by N-based interferences, 31P was measured as 31P16O+ at m/ z 47 employing dynamic reaction cell technique with O2 as reaction gas. Orthophosphate and IP6 were separated within a total chromatographic run-time of 12 min revealing a limit of detection of 0.3 μmol/L. The coefficients of determination obtained in a working range of 1-100 and 1-30 μmol/L were 0.9991 for orthophosphate and 0.9968 for IP6, respectively. The method was successfully applied to extracts from three different soils as well as root and shoot extracts of Brassica napus L. The precision of three independently prepared soil extracts was in the range of 4-10% relative standard deviation for PO43− and 3-8% relative standard deviation for IP6. Soil adsorption/desorption kinetics for IP6/orthophosphate were performed for investigating the sorption behavior of the two P species in the experimental soils. [ABSTRACT FROM AUTHOR]

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Due to enhancement of industrial growth and urbanization, soil contamination is increasing prominently. Therefore, it is important to examine possible adverse effects of industrial waste. Soil samples were might to be polluted with several heavy-metals and pesticides. Gas chromatographic results showed occurrence of high-level of organochlorine and organophosphate pesticides in studied soil samples. Genotoxicity of soil extracts was assessed using environmental-risk assessment models. Soil samples were extracted in hexane and dichloromethane solvents and were evaluated for genotoxic potential by prokaryotic (Ames test, plasmid nicking assay and E. coli K-12 DNA repair defective mutants) and eukaryotic ( Allium cepa root chromosomal aberration and Vigna radiata seed-germination test) bioassays. Strain TA98 was found the most susceptible among soil extracts. The mutagenicity of hexane soil extract from wastewater irrigation was found to be higher than that of DCM samples in terms of mutagenic index, mutagenic potential, and induction factor for Ames strains. The damage in DNA repair defective mutants of hexane extracts were found higher compared to DCM extracts at dose of 20 μl/ml of culture. Survival in polA , lexA and recA mutants were 39%, 47% and 55% while treated with hexane extract. Allium cepa test, mitotic index was decreased in dose-dependent way and various kinds of chromosomal aberrations were found. Vigna radiata seeds germination and other parameters were also affected when treated with wastewater irrigated (WWI) soil. Oxidative stress in V. radiata roots were also showed under CLS microscope. Genotoxicity of WWI soil extract was also confirmed by plasmid nicking test. Our study provides possible explanation for the assessment of potential health and environmental hazards of the industrial region., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors.)

Abstract: Smoke plays a positive role in promoting seed germination and enhancing post-germination processes. The compound in smoke is 3-methyl-2H-furo[2,3-c]pyran-2-one (KAR1). Recently a structurally related butenolide [3,4,5-trimethylfuran-2(5H)-one, (trimethylbutenolide, TMB)], which inhibits germination and reduces the effect of KAR1, was isolated. The mechanisms of action and interaction of these karrikins are unknown. In addition, the ecological significance of fires in altering soil-smoke-chemistry and the spatial dimensions of the influence on burnt sites and neighbouring areas are undetermined. This study quantified KAR1 and TMB residues in soils following fire and assessed the germination activity of burnt soil extracts. Soil samples from 0 to 2, 2 to 4, 4 to 6 and 6 to 8cm depths were extracted using dichloromethane and bioassayed using Lactuca sativa L. achenes (seeds). At all soil depths, L. sativa seeds exhibited significantly greater percentage germination when treated with burnt soil extracts compared to the no-burn soil (control). The L. sativa seeds also showed significantly greater percentage germination when treated with soil extracts from the adjacent plots. Compared to the no-burn soil, higher concentrations of KAR1 and TMB were detected in the surface layers of the burnt soils. Considerable concentrations of KAR1 and TMB were also detected in no-burn soil indicating that sources other than fire may also generate karrikins. Findings of this study imply that post-fire increases in KAR1 residues in the soil may influence soil seed bank stimulation of certain smoke-responsive plant communities in both burnt and adjacent non-burnt areas. [Copyright &y& Elsevier]

Abstract: NaOH extracts of soil and vegetation have been shown to have antioxidant capacity (AOC). However, the identification of specific antioxidant compounds within extracts has proved to be difficult. In earlier work we demonstrated that the presence of some lignin-derived phenolic compounds, which were antioxidants, could only account for a very small percentage of the overall antioxidant capacity of soil extracts. The aims of the work reported here were to measure AOC of both vegetation and soil extracts by the Trolox equivalent antioxidant assay and photochemiluminescence and to analyse them using pyrolysis-field ionisation mass spectrometry (Py-FIMS), which allows a tentative assignment of specific compounds and an amalgamation to broad groups of compounds (e.g. carbohydrates) for the soil extracts. With this information we could find which compounds were closely related to the AOCs of the extracts and of those which might potentially be antioxidants. We extracted six soil samples, which had a range of antioxidant capacities, and the vegetation associated with those soils. The AOC results by the two methods were well correlated, and comparing soil and vegetation AOCs suggested that some antioxidants in vegetation were lost during humification, and that some others were soil-derived. For the soil samples we found that, because most of the compound groups quantified by Py-FIMS were correlated with the antioxidant capacities, a clear assignment of antioxidant properties to groups was restricted. However, individual compounds could be linked to the AOC using multivariate statistics, grouping the samples by their antioxidant capacity. Some compounds were present in both soil and vegetation, and presumably survived humification, while others were only found in the soil, in which they had probably been formed. Further investigation of these tentatively identified compounds provides a way forward in explaining the AOC of soil and vegetation extracts. [Copyright &y& Elsevier]

Determination of major cations in soil extracts is important for soil research. This study introduced a new buffer system (Buf-I) for capillary-zone electrophoresis (CZE) for the detection of major cations in soil. The Buf-I system achieved baseline separation of major cations with a wider detection range, in less time, and with better reproducibility than the old buffer system (Buf-M). Storage stability and running stability experiments showed that the running current of Buf-I was also more stable and the relative standard deviation (RSD%) was significantly less than those of Buf-M. The recovery (91.13–107.64%) by Buf-I was better than that (78.38–103.87%) by Buf-M. The results by Buf-I method were highly consistent with traditional analysis techniques (with a correlation of 0.9963). Therefore, we conclude that the new Buf-I system is more stable and accurate than the old Buf-M system and is especially suitable to determine major cations in soil extract. [ABSTRACT FROM AUTHOR]

Abstract: A simple and rapid bioassay was implemented to detect the germination activity of extracts from soils in pre/post-burn conditions. Soil samples taken from burnt, unburnt and adjacent plots at depths of 0–2, 2–4, 4–6 and 6–8cm before and after burning mesic grassland in South Africa were analysed for germination activity over an eight-week period. Soil samples were extracted using dichloromethane and bioassayed using Grand Rapids lettuce (Lactuca sativa L.) achenes (seeds). The Grand Rapids lettuce seeds exhibited greater germination percentages when treated with extracts from burnt soil compared to the other plots. The magnitude of the germination activity declined with time since the burn. The Grand Rapids lettuce seeds also exhibited significantly higher germination when treated with unburnt soil extracts compared to the control (distilled water) which indicates the existence of other factors controlling germination in unburnt soil. Germination activity in the adjacent plots decreased with time. These findings indicate that the germination activity of the smoke derived from burning plant-material diffuses into the soil and its persistence declines with time. Considering that the soil seed bank contains viable seeds, at a moderate depth, and that they are initially unaffected by the heat of the fire, then smoke residues following a fire can influence the germination and recruitment of plant species that are responsive to smoke-derived compounds and are represented in the germinable soil seed bank. [Copyright &y& Elsevier]

We have developed the techniques for determination of perchlorate in soil extracts by chemiluminescent and photometric methods based on the formation of an ionic pair by cuproinate Cu(I) with perchlorate. The detection limit—respectively 0.1 and 0.3 mg/kg of the soil. [ABSTRACT FROM AUTHOR]

Abstract: Many empirical equations have been developed to predict the properties of saturation extracts, primarily electrical conductivity, from the properties of soil water extracts of 1 to 5 ratio. Soil water 1:5 extracts are more rapidly and reproducibly prepared than saturation extracts. However, the electrical conductivity of saturation extracts (EC se) is the benchmark to assess soil salinity. Analysis of the information provided by the electrical conductivity of soil 1:5 extracts (EC 1:5) is a prerequisite to guide equation development and to use EC 1:5 for soil salinity assessment. A total of 135 soil samples were taken from 39 sites at up to four different depths per site, down to a maximum depth of 95cm in an irrigated agricultural area in SE Spain. Soil 1:5 extracts obtained from each sample were analysed for twelve chemical properties: concentration of sodium, ammonium, potassium, magnesium, calcium, chloride, nitrite, nitrate, sulphate, alkalinity and electrical conductivity. A principal component analysis (PCA) was applied to the correlation matrix of the log-transformed data set. The equilibrium status of 1:5 extracts with regard to gypsum was assessed with the chemical speciation programme SALSOLCHEMIS. The soil gypsum content was determined by using an adaptation of the classical method of total dissolution of soil gypsum, adequate to determine low gypsum contents, i.e. lower than 2%. Three principal components, accounting for 82% of the variance in the correlation matrix, were retained after eigenvector extraction. The first component accounted for 53% of the variance and was interpreted as representing the extract salinity due to gypsum dissolution. The second component accounted for 16% of the variance and was interpreted as representing the component of the extract salinity due to salts more soluble than gypsum, such as sodium and chloride salts. The information about soil salinity is split in two components in the 1:5 extracts, which are not easily resolved, whereas only one salinity component was obtained in the saturation extracts. The EC 1:5 is a reliable property to estimate EC se, with a 95% confidence interval of ±1.2dSm−1, only when it is lower than 1dSm−1. When EC 1:5 is higher than 2.4dSm−1 it could also be reliably used to estimate soil salinity only if the 1:5 extract is gypsum-saturated, which is highly probable when the soil gypsum content is higher than 1.5%, or when the saturation extract is not gypsum-saturated, situation which happens when soil gypsum content is lower than 0.2%. When the EC 1:5 is between 1 and 2.4dSm−1, it provides poor information about the EC se, which could be between 4 and 14dSm−1 unless the soil gypsum content is negligible, i.e. lower than 0.2%. The usefulness of the EC 1:5 to estimate soil salinity can be extended when it is used in conjunction with an estimate of soil gypsum content. The development of more than one equation to estimate EC se from EC 1:5 depending on soil gypsum content is recommended. [Copyright &y& Elsevier]

Abstract: A bulk-modified screen-printed carbon electrode characterised for metal ion detection is presented. Bismuth oxide (Bi2O3) was mixed with graphite-carbon ink to obtain the modified electrode. The best composition was 2% Bi2O3 (wt%) in the graphite-carbon ink. The modified electrode with onboard screen-printed carbon counter and silver–silver chloride pseudo-reference electrodes exhibited good performance in the electrochemical measurement of lead (II) and cadmium (II). The electrode displayed excellent linear behaviour in the concentration range examined (20–300μgL−1) with limits of detection of 8 and 16μgL−1 for both lead (II) and cadmium (II), respectively. The analytical utility of the modified electrode was illustrated by the stripping chronopotentiometric determinations of lead (II) in soil extracts and wastewater samples. [Copyright &y& Elsevier]

Human alteration of the nitrogen cycle has stimulated research on nitrogen cycling in many aquatic and terrestrial ecosystems, where analyses of nitrate (NO3 −) by standard laboratory methods are common. A recent study by Colman et al. (Biogeochemistry 84:161–169, 2007) identified a potential analytical interference of soluble iron (Fe) with NO3 − quantification by standard flow-injection analysis of soil extracts, and suggested that this interference may have led Dail et al. (Biogeochemistry 54:131–146, 2001) to make an erroneous assessment of abiotic nitrate immobilization in prior 15N pool dilution studies of Harvard Forest soils. In this paper, we reproduce the Fe interference problem systematically and show that it is likely related to dissolved, complexed-Fe interfering with the colorimetric analysis of NO2 −. We also show how standard additions of NO3 − and NO2 − to soil extracts at native dissolved Fe concentrations reveal when the Fe interference problem occurs, and permit the assessment of its significance for past, present, and future analyses. We demonstrate low soluble Fe concentrations and good recovery of standard additions of NO3 − and NO2 − in extracts of sterilized Harvard Forest soils. Hence, we maintain that rapid NO3 − immobilization occurred in sterilized samples of the Harvard Forest O horizon in the study by Dail et al. (2001). Furthermore, additional evidence is accumulating in the literature for rapid disappearance of NO3 − added to soils, suggesting that our observations were not the result of an isolated analytical artifact. The conditions for NO3 − reduction are likely to be highly dependent on microsite properties, both in situ and in the laboratory. The so-called “ferrous wheel hypothesis” (Davidson et al., Glob Chang Biol 9:228–236, 2003) remains an unproven, viable explanation for published observations. [ABSTRACT FROM AUTHOR]

By using Eriochrome Cyanine R modified anion-exchange resin as solid phase extraction cartridge coupled with ICP-AES, a novel method for the determination of Al fractionation in soil extracts has been developed. The proposed method possesses the following distinct advantages: (1) Good selectivity. The Eriochrome Cyanine R modified resin shows good recognizing ability for Al fractions. The total monomeric Ala can be adsorbed on the modified resin in the pH range of 6 ∼ 10 by column procedure, and the organic monomeric Alo can be determined by batch procedure rapidly while no adsorption of inorganic monomeric Ali was found in 30 min at least. Thus Ali can be obtained by subtraction between Ala and Alo. Major matrix's interference (Fe, Mn and organic substances) in soil extracts can be avoided. (2) Simple manipulation. The modified resin is very easy to prepare just simply by impregnating the resin with a solution containing Eriochrome Cyanine R. This method has been applied to the determination of five fractions of Al in soil extracts with the experimental results being in agreement with those obtained by Driscoll's method. In addition, Calcon, 8-hydroxyquinoline-5-sulfonic acid, Tiron, Solochrome Violet RS, Pyrocatechol Violet, Xylenol orange, Ferron and Alizarin Red S are also modified to anion-exchange resin as solid-phase extractants. Their conditions to pre-concentrate and determine Al fractionation are investigated, and the adsorptive characteristics of various chelating reagents have been discussed and compared. [ABSTRACT FROM AUTHOR]

Investigations were carried out on sandy forest soils from Wielkopoiski National Park (west-central Poland), which have been exposed for a long time to anthropogenic pressure. Two comparative extract recovery methods were performed for aqueous soil extracts (ME) at ratios 1: 1, and those obtained from so-called saturated paste (MP). Recovered extracts were analyzed for sodium, potassium, magnesium, calcium, aluminium, chloride, fluoride, nitrate and sulphate concentrations, at various depths of two slightly different soil profiles. Higher levels of alkaline cations were obtained in extracts recovered at ratios 1: 1, in the case of sandy soils along the entire profile, whereas in profiles with variable lithology, the granulometric composition clearly affected the mechanism of ion release. The patterns of changes in the contents of chlorides and sulphates were similar to those of calcium and magnesium, while fluoride levels in the topsoil differed significantly, depending on the method applied. Differences between the two methods were also significant in the case of aluminium content. The elaboration of aluminium toxicity indices should consider such approaches. [ABSTRACT FROM AUTHOR]

The article reports on a study which evaluates the toxicity of chemicals and contaminated soils and waste waters through automated short-term genotoxicity testing. It aims to show the applicability of an automated test system for evaluating genotoxic effects of different various chemicals and environmental samples. It applies chemicals with different physical, chemical and toxilogical properties in automated test systems during optimization. It shows that both the testing of non-volatile substances with genotoxic effects and the testing of water and soil samples in the automatic system work well.

Abstract: With the objective of detecting and quantitating low concentrations of perfluorinated carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), in soils, we compared the analytical suitability of liquid chromatography columns containing three different stationary phases, two different liquid chromatography–tandem mass spectrometry (LC/MS/MS) systems, and eight combinations of sample-extract pretreatments, extractions and cleanups on three test soils. For the columns and systems we tested, we achieved the greatest analytical sensitivity for PFCAs using a column with a C18 stationary phase in a Waters LC/MS/MS. In this system we achieved an instrument detection limit for PFOA of 270ag/μL, equating to about 14fg of PFOA on-column. While an elementary acetonitrile/water extraction of soils recovers PFCAs effectively, natural soil organic matter also dissolved in the extracts commonly imparts significant noise that appears as broad, multi-nodal, asymmetric peaks that coelute with several PFCAs. The intensity and elution profile of this noise is highly variable among soils and it challenges detection of low concentrations of PFCAs by decreasing the signal-to-noise contrast. In an effort to decrease this background noise, we investigated several methods of pretreatment, extraction and cleanup, in a variety of combinations, that used alkaline and unbuffered water, acetonitrile, tetrabutylammonium hydrogen sulfate, methyl-tert-butyl ether, dispersed activated carbon and solid-phase extraction. For the combined objectives of complete recovery and minimization of background noise, we have chosen: (1) alkaline pretreatment; (2) extraction with acetonitrile/water; (3) evaporation to dryness; (4) reconstitution with tetrabutylammonium–hydrogen–sulfate ion-pairing solution; (5) ion-pair extraction to methyl-tert-butyl ether; (6) evaporation to dryness; (7) reconstitution with 60/40 acetonitrile/water (v/v); and (8) analysis by LC/MS/MS. Using this method, we detected in all three of our test soils, endogenous concentrations of all of our PFCA analytes, C6 through C10—the lowest concentrations being roughly 30pg/g of dry soil for perfluorinated hexanoic and decanoic acids in an agricultural soil. [Copyright &y& Elsevier]

Abstract: Methods were developed for the extraction from soil, identification, confirmation and quantitation by LC/MS/MS of trace levels of perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA). Whereas PFOA, PFNA and PFDA all can be quantitated using the method of standard additions, PFOA also can be quantitated less laboriously using 13C4-PFOA as a matrix internal standard. The impact of extract matrices on signal varied between soils and temporally during analytical runs rendering 13C4-PFOA unsuitable as a matrix internal standard for quantitating perfluorinated carboxylic acids (PFCAs) other than PFOA, which co-elutes with 13C4-PFOA. In fact, for soil extracts, quantitation of PFCAs based on external calibrations proved about as accurate as use of matrix internal standards for target analytes that do not co-elute with the matrix internal standard. Also, 13C4-PFOA should be used carefully as a matrix internal standard for trace levels of PFOA because some 13C4-PFOA standards contain trace impurities of unlabelled PFOA. When the presence of PFCAs in soil extracts is being determined by LC/MS/MS, detection limits are best defined by statistical methods that quantify the significance of contrast between analytical signal and background noise using multiple analyses. Further, when developing a calibration of low concentrations using weighted regression, the central tendency of the calibration line is best fitted using graphical depictions of error. As the MDL for the transition-product quantitation ion is approached in LC/MS/MS, relatively weak signals of transition-product confirmation ions can be used as a rejection criterion by looking for anomalously high values of the ratio of the confirmation to the quantitation ion. [Copyright &y& Elsevier]

Abstract: Capillary electrophoresis (CE) coupled to ion trap mass spectrometry (MS) was evaluated for the separation and identification of chemical warfare agent degradation products (alkylphosphonic acids and alkyl alkylphosphonic acids). Different analytical parameters were optimized in negative ionization mode such as electrolyte composition (15mM CH3COONH4, pH 8.8), sheath liquid composition (MeOH/H2O/NH3, 75:25:2, v/v/v), nebulization and ion trapping conditions. A standard mixture of five alkylphosphonic (di)acids and five alkyl alkylphosphonic (mono)acids containing isomeric compounds was used in order to evaluate CE selectivity and MS identification capability. The obtained electropherograms revealed that CE selectivity was very limited in the case of alkyl alkylphosphonic acid positional isomers, whereas isomeric isopropylphosphonic and propylphosphonic acids were baseline-separated. CE–MS–MS experiments provided an unambiguous identification of each isomeric co-migrating alkyl alkylphosphonic acids thanks to the presence of specific fragment ions. On the other hand, CE separation was mandatory for the identification of isomeric alkylphosphonic acids, which led to the same fragment ion and could not be differentiated by MS–MS. The developed method was applied to the analysis of soil extracts spiked with the analytes (before or after extraction treatment) and appeared to be very promising since resolution and sensitivity were similar to those observed in deionized water. Especially, analytes were detected and identified in soil extract spiked at 5μgmL−1 with each compound before extraction treatment. [Copyright &y& Elsevier]

Abstract: A new analytical procedure for the simultaneous determination of trace oxyhalides and haloacetic acids (HAs) in drinking water and aqueous soil extracts is described. The method uses micro-bore ion chromatography (IC) coupled with suppressed conductivity (SC) and electrospray ionization mass spectrometric detection (ESI-MS). The IC–SC–ESI-MS system included a secondary flow of 100% MeOH, which was added to the column eluate (post-suppressor) and resulted in a significant increase in sensitivity for all analytes. All ESI-MS parameters were optimized for HA analysis and sensitivity quantitatively compared to suppressed conductivity. Full analytical performance characteristics for the developed method are presented for monochloro-, monobromo-, dichloro-, dibromo-, trichloro-, bromochloro, chlorodifluoro-, trifluoro-, dichlorobromo- and dibromochloroacetic acid, as well as the oxyhalides iodate, bromate, chlorate and perchlorate. In the case of the HAs, an optimised 25-fold SPE preconcentration method meant all analytes could be readily detected well below the USEPA 60μg/L regulatory limit using conductivity and/or ESI-MS. The IC–ESI-MS method was applied to the determination of oxyhalides and HAs in both soil extracts and drinking water samples. Soil samples were extracted using ultra pure water with subsequent determination of perchlorate at 1.68μg/g of soil. A drinking water sample containing HAs was preconcentrated using LiChrolut EN solid phase extraction cartridges with subsequent sulphate and chloride removal. Total HAs were determined at 13μg/L. [Copyright &y& Elsevier]

Abstract: The occurrence of water repellent spots can inhibit a homogeneous wetting progress in soil. Although the wettability is an important factor for sorption and transport processes, the knowledge about the reasons for water repellent behavior and its effects on other soil properties is still insufficient. In this study, water repellent and wettable soil samples from two urban locations were compared. It was examined, to which extent differences in the actual water repellency of closely neighboring spots are associated to variable factors like the water content or to stable properties of soil organic matter (SOM). In order to analyze the interrelations between the moisture status and the wettability behavior, soil samples were either subjected to drying–remoistening cycles or pre-conditioned under various conditions. For the characterization of stable SOM properties, the soil samples were investigated by ESEM (Environmental Scanning Electron Microscope) and FT-IR spectroscopy. Beside the investigation of solid soil samples, selected properties of aqueous soil extracts were measured. The results of this study indicate that the water content is not the only factor responsible for the differences in actual water repellency. For different locations, the wettability behavior probably is based on different mechanisms. For one of the examined sites, differences in actual repellency of closely neighboring samples were interrelated with differences in pH and the ionic strength of the soil solutions. For both locations, amphiphilic substances probably are an important factor of influence for the wettability behavior. Additionally, the results suggest that the time which proceeds after a change of the moisture status in soil is an important factor for water repellency. [Copyright &y& Elsevier]

Screen-printed carbon electrodes were fabricated with amino acid functionality by using in situ co-deposition of mercury and cysteine. The three-electrode configuration (graphite carbon working electrode, carbon counter electrode and silver/silver chloride reference electrode) incorporating a cysteine-modified working electrode exhibited good sensitivity towards cadmium(II). Several experimental variables affecting the sensor stripping response were characterised and optimised. These include cysteine and mercury concentrations, deposition time, deposition potential and stripping current. Surface analysis was also conducted using scanning electron microscopy (SEM) in order to characterize the electrode surface during cadmium analysis. The stripping chronopotentiometric response for cadmium(II) was linear in the concentration range 0.4–800 μg L−1 when a deposition time of 2 min was used. A detection limit of 0.4 μg L−1 was obtained using 0.025 M Tris–HCl buffer containing 0.1 M KCl (pH 7.4) as the supporting electrolyte. The analytical utility of the cysteine-modified sensor was demonstrated by applying it to cadmium analysis in various wastewater and soil samples collected from a contaminated site and extracted using acetic acid. The results obtained using the developed electrodes agreed satisfactorily with the values achieved using atomic absorption spectrometry and inductively coupled plasma mass spectrometry analysis. These results demonstrate the feasibility of using this type of sensor for cadmium analysis. [ABSTRACT FROM AUTHOR]

Abstract: As copper(II) is a common ion in a variety of analytical samples, its effect on the stripping response of lead(II) at bismuth film screen-printed carbon electrode (BFSPCE) was investigated. The study was conducted using a screen-printed three-electrode system (working, counter and reference electrodes), with the carbon-working electrode plated in situ with bismuth film. Copper present at significant concentration level in samples was found to affect the sensitivity of the electrode by reducing the constant current stripping chronopotentiometric (CCSCP) response of lead(II). Recovery of the lead stripping response at the BFSPCE in the presence of copper was obtained when 0.1mM ferricyanide was added to the test solution. The ferricyanide added circumvents the detrimental effect of copper(II) by selectively masking the copper ions by forming a complex. The analytical utility of the procedure is illustrated by the stripping chronopotentiometric determinations of lead(II) in soil extracts. [Copyright &y& Elsevier]

Abstract: In the last decade, significant advances in flow analysis have been reported, namely the extensive use of computer-controlled devices to enhance the autonomy and performance of analysers. In the present work, computer-controlled multi-syringe flow injection systems are proposed to perform the spectrophotometric determination of available iron and boron in soil extracts. The methodologies were based on the formation of ferroin complex (determination of iron) and azomethine-H reaction (determination of boron). Both determinations were performed in manifolds with similar configurations by changing the reagents present in the different syringes. In the determination of iron, elimination of Schlieren effect in the detection system was achieved through the binary sampling approach, where a three-way valve was actuated to intercalate small slugs of sample and reagent, promoting better mixing conditions for solutions with different values of refractive index. In the determination of boron, in-line sample blank measurement was attained by omitting the introduction of reagent through software control, without manifold reconfiguration. Linear calibration curves were established between 0.50 and 10.0mgFel−1 and between 0.20 and 4.0mgBl−1. No systematic difference was found when soil extracts were analysed by the proposed methodologies and compared to the respective reference procedures. [Copyright &y& Elsevier]

The development of mercury-free electroanalytical systems for in-field analysis of pollutants requires a foundation on the electrochemical behaviour of the chosen electrode material in the target sample matrices. In this work, the behaviour of gold working electrodes in the media employed in the BCR sequential extraction protocol, for the fractionation of metals in solid environmental matrices, is reported. All three of the BCR sequential extraction media are redox active, on the basis of acidity and oxygen content as well as the inherent reducing or oxidising nature of some of the reagents employed: 0.11 M acetic acid, 0.1 M hydroxylammonium chloride (adjusted to pH 2) and 1 M ammonium acetate (adjusted to pH 2) with added trace hydrogen peroxide. The available potential ranges together with the demonstrated detection of target metals in these media are presented. Stripping voltammetry of copper or lead in the BCR extract media solutions reveal a multi-peak behaviour due to the stripping of both bulk metal and underpotential metal deposits. A procedure based on underpotential deposition–stripping voltammetry (UPD-SV) was evaluated for application to determination of copper in 0.11 M acetic acid soil extracts. A preliminary screening step in which different deposition times are applied to the sample enables a deposition time commensurate with UPD-SV to be selected so that no bulk deposition or stripping occurs thus simplifying the shape and features of the resulting voltammograms. Choice of the suitable deposition time is then followed by standards addition calibration. The method was validated by the analysis of a number of BCR 0.11 M acetic acid soil extracts. Good agreement was obtained been the UPD-SV method and atomic spectroscopic results. [Copyright &y& Elsevier]

Abstract A study was conducted to assess the phytotoxicity of Ageratum conyzoides , a weed of cultivated areas, to the growth and establishment of wheat (Triticum aestivum ). The lengths of the radicle and coleoptile and the seedling dry weight of wheat were significantly reduced when wheat was grown in field soil previously infested with A. conyzoides , compared to control soil collected from an area devoid of this weed. Even extracts prepared from A. conyzoides soil were inhibitory, indicating the presence of some water-soluble phytotoxins in the soil. To determine the possible contribution of the weed in releasing these phytotoxins, growth studies involving leaf residues and their extracts and amended soils (prepared by incorporating leaf residues and residue extracts) were also performed on wheat. With all treatments, an inhibitory effect of A. conyzoides was found, compared to respective controls. A significant amount of water-soluble phytotoxins (the phenolics) was found to be present in the soil infested with A. conyzoides , leaf residues and the amended soils. The amount of phenolics correlated well with growth performance in the respective treatments. This study establishes the phytotoxicity of leaf residues of A. conyzoides to wheat through the release of phenolics into the soil, which may serve as possible tools in establishing its allelopathy. [ABSTRACT FROM AUTHOR]

An on-line solid-phase extraction (SPE) technique, linked to spectrophotometry, has been developed to overcome the problem of high matrix concentration, which is thought to interfere with the determination of low levels of aluminum (Al) in environmental samples. Tiron modified resin was prepared and used as a SPE absorbent, which can quantitatively adsorb Al(III) at pH 4–6 with an adsorption capacity of 5.6 mg g−1 resin. The main advantages of this novel method are: (1) a much higher sensitivity has been obtained by SPE technology; and (2) a large amount of Na+, K+, Ca2+ and Mg2+ can be removed and the interference of Fe(III), Mn(II) and F− can be efficiently eliminated by eluting with 0.25 mol l−1 NaOH. It is a highly selective and sensitive method for simple and quick determination of dissolved Al in soil extracts and ground waters, particularly suitable for the analysis of complex environmental samples. [Copyright &y& Elsevier]

A sensitive atomic spectrometric method for the redox speciation analysis of antimony in soils is described. The method is based on the selective generation of stibine from Sb(III) in a continuous flow system using atomic fluorescence spectrometry for detection. Sb(V) is masked by citric or oxalic acid in HCl medium. The procedure was optimized with synthetic solutions of Sb(III) and Sb(V). The effect of carboxylic acid and HCl concentration on the recovery of Sb(III) and Sb(V) species from standard solutions, and on the fluorescence signal were studied. Both species were extracted from soil with H2O, 0.05 mol l−1 EDTA and 0.25 mol l−1 H2SO4. Since the soil samples were collected from sites impacted by copper mining activities, the effect of Cu2+ on the determination of antimony in synthetic solutions and soil extracts was studied. Cu2+ decreased the Sb(III) signal, but had no effect on the total antimony determination. Therefore, the selective determination of Sb(III) was carried out in citric acid–HCl medium, using the analyte addition technique. Total antimony in soil extracts was determined using the standard calibration technique after reducing Sb(V) to Sb(III) at room temperature with KI–ascorbic acid. The Sb(V) concentration was calculated from the difference between total antimony and Sb(III). The limits of detection (PS Analytical, Excalibur Millennium model) were 17 and 10 ng l−1 for Sb(III) and total antimony, respectively, and the R.S.D. at the 0.5-μg l−1 level were 2.5 and 2.4%, respectively. The total antimony concentration of soils is in the mg kg−1 range; the Sb recovery from the different soils by the extracting solutions was between less than 0.02% and approximately 10%. Similar recoveries were obtained using EDTA and sulfuric acid solutions. Sb(V) was found to be the main antimony species extracted from soils. [Copyright &y& Elsevier]

For the assessment of contaminated or remediated soils, in addition to chemical analyses, ecotoxicological tests are performed which focus on the retention function of soils (determined by tests with aqueous soil extracts) and on the habitat function (determined by tests with soil). While numerous standardized test guidelines exist to investigate effects by chemical substances, respective test procedures for soil assessments are lacking. To close this gap, a round robin test was performed to support standardization. Four contaminated soils were tested using a total of fifteen test systems including ecotoxicological and genotoxicological tests with soil extracts and soil. The results obtained from the tests with soil extracts are presented in this article. [ABSTRACT FROM AUTHOR]

Aqueous extracts of burnt soil, unburnt soil and oven-heated unburnt soil were tested as to their effects on vesicular-arbuscular mycorrhizal (VAM) fungi (spore germination, mycelial propagule activity and root colonization). The extracts of burnt or heated soil inhibited VAM spore germination and extrarrhizal mycelium activity. [ABSTRACT FROM AUTHOR]