Soil Toxicity Research Articles

Analysis of the toxic mechanisms of fluoxastrobin on the earthworm (Eisenia fetida) using transcriptomics

Fluoxastrobin (FLUO), one of the best-selling strobilurin fungicides, could prevent fungal diseases from oilseed crops, fruits, grains, and vegetables. The widespread use of FLUO leads to the continuous accumulation of FLUO in soil. Our previous studies have demonstrated that FLUO exhibited different toxicity in artificial soil and three natural soils (fluvo-aquic soils, black soils, and red clay). The toxicity of FLUO was greater in natural soil than the artificial soil, specifically, showed the highest toxicity in fluvo-aquic soils. To better investigate the mechanism of FLUO toxicity to earthworms (Eisenia fetida), we selected fluvo-aquic soils as representative soil and used transcriptomics to study the gene expression in earthworms after FLUO exposure. The results demonstrated that the differentially expressed genes in earthworms after FLUO exposure mainly presented in pathways involving protein folding, immunity, signal transduction, and cell growth. It may be the reason why FLUO exposure stressed the earthworms and affected their normal growth activities. The present study fills gaps in the literature regarding the soil bio-toxicity of strobilurin fungicides. It also sounds the alarm for the application of such fungicides even at the low concentration (0.1 mg kg−1).

Assessing the toxicity of contaminated soils via direct contact using a gas production bioassay of thiosulfate utilizing denitrifying bacteria (TUDB)

A direct contact bioassay of thiosulfate utilizing denitrifying bacteria (TUDB) based on inhibition of gas production was deployed to assess the toxicity of naturally contaminated field soils and soils artificially contaminated with heavy metals. Test procedure producing optimal conditions responsible for maximum gas production was 0.5 mL test culture, 1 g soil sample, 80 RPM, and 48 h reaction time. Similarly, the concentrations which generated a 50% reduction in gas production by TUDB for the tested heavy metals were 3.01 mg/kg Cr6+; 15.30 mg/kg Ni2+;15.50 mg/kg Cu2+;16.60 mg/kg Ag+; 20.60 mg/kg As3+; 32.80 mg/kg Hg2+; 54.70 mg/kg Cd2+; and 74.0 mg/kg Pb2+. Because soil toxicity is usually influenced by various physicochemical characteristics, ten reference soils were used to determine the toxicity threshold for evaluating the toxicity of naturally contaminated field soils. All eight contaminated soils were toxic to the TUDB bioassay because their levels of inhibition ranged between 72% and 100% and exceeded the determined toxicity threshold of 10%. Compared to other direct contact assays, the newly developed assay TUDB proved to be very robust, producing highly sensitive data while the different soil physicochemical properties exerted minimal influence on the gas production activity of TUDB. Additionally, the simplicity of the developed methodology coupled with the elimination of pretreatment procedures such as elutriation, and ability to perform generate sensitive data in turbid and highly colored samples makes it, cost-effective, and easily adaptable for the assessment of heavy metal and field contaminated soils when compared with other conventional assays which require sophisticated instrumentation and prolonged testing procedures and times.

Comprehensive Assessment of Enantioselective Bioactivity, Toxicity, and Dissipation in Soil of the Chiral Herbicide Flurtamone.

Flurtamone is a typical chiral pesticide with a pair of enantiomers. In this study, the enantioselective biological effects of flurtamone enantiomers were systematically investigated. The bioactivities of R-flurtamone were 6.3-35.6 and 1.7-9.9 times higher than S- and Rac-flurtamone, respectively. The contribution of the R-enantiomer to herbicidal activity was 86.3-97.3%. The carotenoid content in the R-flurtamone treatment group was 1.31-2.14 times lower than that in the S-flurtamone treatment group. Molecular docking found that flurtamone can form aromatic H-bonds with phenylalanine (PHE) 233 of phytoene desaturase (PDS), while R-flurtamone can form π-π stacking with PHE 202 and PHE 311. The binding energies of R- and S-flurtamone were -10.239 and -7.555 kcal/mol, respectively. Furthermore, the acute toxicity levels to Selenastrum capricornutum of R- and Rac-flurtamone were both highly toxic, and S-flurtamone has moderate toxicity. S-Flurtamone dissipated preferentially. Therefore, the development of R-flurtamone can decrease environmental risks and protect human health.

Shift of combined ecotoxicity index in petroleum polluted soils during a bacterial remediation

Introduction: Bioremediation has been shown to be an effective strategy for removing toxic pollutants from the environment, particularly organic chemicals such as petroleum hydrocarbons. This paper investigates the changes in toxicity of petroleum-contaminated soil as a result of microbial remediation processes.Methods: Changes in the ecotoxicity of the contaminated soil were examined using a plant, earthworm, enzyme activity and luminescent bacteria toxicity tests.Results: The results showed that bioremediation could effectively degrade petroleum hydrocarbon (C10–C40) pollutants. After 42 days of remediation, the petroleum hydrocarbon (C10–C40) content of Group A (bioaugmented polluted wetland soil) decreased from 1.66 g/kg to 1.00 g/kg, and the degradation rate was 40.6%. The petroleum hydrocarbon (C10–C40) content of Group B (bioaugmented polluted farmland soil decreased from 4.00 g/kg to 1.94 g/kg, and the degradation rate was 51.6%. During the microbial remediation progress, the ecological toxicity of petroleum-contaminated soil first increased and then decreased. The photosynthetic pigment content index in the higher plant toxicity test, the earthworm survival index and the soil catalase activity all showed good agreement with the relative luminescence index of extracted DCM/DMSO in the luminescent bacterial toxicity test. The soil toxicity decreased significantly after remediation. Specifically, the photosynthetic pigment content of wheat were inhibited in the soil during the whole process (remediation for 42 days), and decreased to the minimum on remediation day 21. The 7-day and 14-day survival rate of earthworms in Group A and Group B gradually decreased in the soil remediation process, and then gradually increased, survival rate at the end of remediation was higher than at the beginning. Soil catalase activity was significantly negatively correlated with petroleum hydrocarbon (C10–C40) content (−0.988, −0.989). The ecological toxicity of contaminated soil reached to the maximum on the 21st day of remediation, relative luminosity of luminescent bacteria in dichloromethane/dimethyl sulfoxide extracts from Group A and Group B were 26.3% and 16.3%, respectively.Conclusion: Bioremediation could effectively degrade petroleum hydrocarbon (C10–C40) pollutants. Wheat photosynthetic pigment content, earthworm survival rate, soil catalase activity and relative luminescence of luminescent bacteria can better indicate the ecological toxicity of petroleum-contaminated soil in bioremediation process.

Effect of Pymarc with NPK 17-17-17 and intra-row spacing on soil and bush bean (Phaseolus vulgaris L.) yield in volcanic highland, Rwanda

Bush bean is the poor families’ meat in Rwanda and grown in many corners of the country. However, unevenness application of organic and inorganic amendments brought soil degradation including soil toxicity or deficiency and low bush bean production. The objective of this study was to evaluate the effect of pymarc rates with NPK and spacing on Soil organic matter, physical parameters and bush bean yield parameters in volcanic highland. The design was RCBD with four replications and the experiment had two factors; Pymarc rates: P0(control), P1(250Kg ha-1 NPK), P2(10 tons ha-1 pymarc+250 Kg ha-1 NPK), P3(15 tons ha-1 pymarc+250Kg ha-1 NPK) and P4(20 tons ha-1 pymarc+250Kg ha-1 NPK) and spacing levels: S1(40cm x15cm), S2(40cm x 20cm) and S3(40cm x 30cm). Results showed that, highly significant difference (p<0.01) was in treatments and greatest improvements were brought out by P2S1 with lowest Bd(0.95 g cm-3), highest WHC(38.34 %) and porosity(42.18 %) at harvesting with mean yield of 3.03 t/ha compared to P0S3 with least values of studied attributes. Highest SOM content was found out in P4S3 and P3S1 of 9.84 % and 9.75 % sequentially. The correlation analysis results between WHC, Porosity, SOM and yield varied from weak to strong (0.4>r, r>0.7), significant (p<0.05) and positive while the same relationship but negative existed between Bd and other parameters. Therefore, sowing the bush bean at the spacing of 40cm x15cm with application of 10t ha-1 pymarc+250 Kg ha-1 NPK 17-17-17 could be recommended to agronomists and farmers from volcanic highland in Rwanda for bush bean optimum yield.

Controls on sulfide accumulation in coastal soils during simulated sea level rise

A likely consequence of sea level rise during the next century will be progressive inundation of seawater through the current unsaturated zone in coastal-margin soils. It is unclear how this will change the biogeochemical cycling of iron, sulfur and carbon over different time scales and soil types. A long-term (540 day) laboratory experiment, slowly inundating intact coastal soil cores with seawater from the ‘bottom up’, was conducted to observe how coupled iron and sulfur dynamics change in different soil types. Pore water was extracted from the 60 cm cores at 10 cm depth intervals every 90 days and analysed for pH, electrical conductivity (EC), Fe2+, HS− and dissolved metals (Fe, Mn, As, Cd, Cu, Ni, Pb, Co, Zn) as well as stable sulfur (34S/32S) and radiogenic strontium (87Sr/86Sr) isotopes. Destructive solid phase analyses (for reactive Fe, acid volatile and chromium reducible sulfur (AVS and CRS) and total organic carbon (TOC)) were made at the start and end of the experiment. Iron and sulfate reduction was induced in soils with readily available TOC as anoxic conditions established, evidenced by statistically significant increases (P < 0.001) in dissolved Fe2+ and sulfide concentrations in porewaters, as well as simultaneous and progressive increase in the sulfur isotope (34S/32S) ratios. An increase in AVS indicated formation of metastable iron sulfide (FeS) minerals resulting from Fe2+ and sulfide in porewaters post inundation. This was supported by PHREEQC modelling of local mineral saturation states/indices in the system. Overall, the Fe2+ concentration increased to a peak at between 270 and 360 days, and then began decreasing at some depths, indicating slowing iron reduction, presumably because reactive iron (oxyhydro)oxides became progressively consumed by microbially driven reductive processes. However, microbially mediated sulfate reduction continued as abundant sulfate was still available from seawater. In the absence of free Fe2+, sulfide accumulated in the porewater, but only in those soils inundated the longest (>360 days), and with greater than 5% TOC. The combined use of sulfur (34S/32S) and strontium (87Sr/86Sr) isotopes supported the observed results, and represents a new and robust technique to quantify progressive sulfate reduction and seawater mixing phenomena in coastal soils. This study gives new insights into the biogeochemical cycling of sulfur and iron in soils experiencing seawater inundation from sea level rise over longer timescales. It is likely that sulfidisation (due to in-situ sulfate reduction) will begin to affect coastal wetland soils, especially in areas where TOC is high and where reactive iron depletes over time. This has potential consequences for sulfide toxicity in coastal soils and environments globally.

Effects of rapeseed residue organic fertilizer on cadmium toxicity in soil and its uptake and transfer by rice plants (Oryza sativa L.)

AbstractCadmium (Cd) contamination of rice fields is a global agro‐environmental issue. Rapeseed (canola) residue organic fertilizer (RROF) as a potential strategy to minimize Cd accumulation in rice planted in acidic soil. The results showed that application of 7.5–30.0 g kg−1 RROF increased the soil pH value by 0.01–0.55 units, increased soil organic matter (OM) by 7.8–25.0%, increased soil microbial biomass carbon (MBC) and nitrogen (MBN) by 0.0–89.7% and 0.0–47.5%, respectively, and increased soil dehydrogenase (DH), acid phosphatase (ACP), and urease (UA) activities by 14.3–344.0%, 0.0–127.1%, and 3.5–14.3%, respectively. The application of RROF treatments reduced the soil acid‐extractable Cd (ACI–Cd) content by 8.1–36.4% and increased the reducible Cd (RED–Cd) and oxidizable Cd (OXI–Cd) by 1.3–36.4% and 16.2–47.9%, respectively. The path analysis demonstrated that soil OM, ACP activity, Mn, and Ca ions had a significant negative indirect effect on the decrease in soil ACI‐Cd (rOM = −0.628, rACP = −0.582, rMn = −0.627, rCa = −0.341), while Zn ions showed a strong direct effect (bZn = 0.567) and indirect positive effect (rZn = 0.580). In rice plants, the contents of Cd, Fe, K, Mg, P, and Zn in rice tissues increased, and the Cd content in rice grains decreased by 3.1–31.3% under RROF application. The results of the correlation analysis found that K and Zn in rice husks and Mg in grains were significantly and negatively correlated with the husk–grain translocation factor of Cd (r = −0.88** for Zn, r = −0.81** for K, and r = −0.59* for Mg). In addition, a significant negative correlation of root–straw translocation factors of Cd with Ca and Fe ions in the roots was observed (r = −0.63* and r = −0.60* for Ca at the filling and maturity stages of rice, r = −0.61* for Fe at the tillering stage of rice). RDA showed that the distribution fraction of soil Cd controlled the accumulation of Cd in various parts of rice, with soil ACI–Cd content explaining 22.4% of the total eigen values at a significant level, followed by 14.1% for OXI–Cd. This means that ACI–Cd was the primary factor that controlled Cd accumulation in rice grain, followed by OXI–Cd.

The potential of Euglena species as a bioindicator for soil ecotoxicity assessment

Currently, there are no standard international test methods for assessing aquatic and soil toxicity, with aquatic toxicity tests based on limited Euglena species. Here, we proposed Euglena species as extended test species, especially as new soil test species for a paper-disc soil method, considering its ecologically important roles in providing highly bioavailable in-vivo nutrients to upper trophic level organisms. We conducted experiments to identify the optimal exposure duration for two Euglena species (Euglena viridis and Euglena geniculata). We demonstrated the toxic effects of nickel (model contaminant) on their photosynthetic parameters and growth in freshwater. The growth and photosynthetic activity of three Euglena species were significantly inhibited in nickel-contaminated soil during paper-disc soil tests, especially the test species adsorbed onto paper-disc soil. Euglena gracilis was more sensitive to nickel than E. viridis and E. geniculata in freshwater and soil. Thus, E. viridis and E. geniculata have potential as additional test species for improving test species diversity, while all three species have potential as new soil test species for soil toxicity assessment. Thus, results these species may be suitable for routine aquatic toxicity testing and new soil toxicity testing, addressing the current paucity of test species in freshwater and soil toxicity assessment.

Silicon-mediated alleviation of cadmium toxicity in soil-plant system: historical review.

The contamination of crops by Cd is a worldwide problem that needs to be addressed for minimizing risk for human health. Today, numerous investigations have demonstrated that Si plays a role in reducing Cd toxicity and accumulation in cultivated plants. The evolution of scientific understanding - the Cd behavior in soil and in plant is discussed for the first time. Our analysis evidences that the research on Si-Cd interactions in the soil-plant system has quickened only in recent years, although basic interactions between silicic acid and Cd cations in aqueous systems were studied over 40-50years ago. Today, numerous direct and indirect mechanisms of the Si impact on mobility and translocation of Cd in soil and in plants are reported. More productive studies in this area are those that considered the soil-plant system as a whole. Analysis of the development of the Cd-Si-related ideas suggests the prospects of further studies aimed at finding synergetic action of Si and other substances on Cd behavior in the soil-plant system.

Changes in biological activity and toxicity of soil in sweet corn crops

The number of soil microorganisms affect the fertility of the soil and the processes occurring in the soil microflora. An urgent research problem is the rationale for the use of intensive technologies for the cultivation of sweet corn using progressive methods for obtaining a highly productive crop based on the principles of resource conservation, biologization and ecologization. The purpose of the research is to study the toxicity and biological activity of the soil after sowing sweet corn. The tasks are to determine the biological activity and toxicity of the soil, and comparative impact of agricultural practices in the study of soil toxicity. Two-factor experiment in quadruple repetition. The experiments were carried out on the farm enterprise of Popov S.A., the Chernoyarsky district of the Astrakhan region. The research period was 2009…2015. Determination of biological activity and toxicity was carried out at the beginning of the research in 2009 and 2015. According to the assessment of the intensity of the destruction of cellulose on O.E. Pryazhnikova’s scale biological activity was characterized as strong. A close correlation dependence on experience factors was noted, the relationship between the signs was high and direct. When determining the toxicity of the soil, we came to the conclusion that at the beginning of the research favorable conditions for the development of the studied crop were formed on soils cultivated by moldboard cultivation. According to zero tillage, an increase in soil toxicity was observed, which was expressed in a decrease in seed germination, the mass of seedlings. Revisited in 2015. Soil toxicity after zero tillage decreased in all variants, seed germination increased, on average, by 5...8%. As a result of the accumulation of plant residues on the soil surface, an upper humus layer was formed, leading to a constant penetration of ai r into the soil.

Characteristics of Soil DOM and Its Effect on the Transformation of Potentially Toxic Elements (PTE) Forms under Organic Fertilizer Return Conditions

In order to explore the effects of the composition and structure of soil’s dissolved organic matter (DOM) and its electron transfer capacity (ETC) on the bioavailability of the potential toxic elements chromium (Cr), lead (Pb) and cadmium (Cd) after the application of decomposed pig manure organic fertilizer, three-dimensional fluorescence spectroscopy (3D-EEMs), parallel factor analysis (PARAFAC) and electrochemical methods were used to analyze the composition characteristics of DOM in soil solution and the changes in the ETC, and the dynamic relationship between the relative content of DOM, ETC and various forms of potential toxic elements was explored by means of a Pearson correlation analysis and redundancy analysis (RDA). Among them, Cr, Pb and Cd were the elements with significant biological toxicity in farmland soil. The results indicated the following: (1) The soil DOM before and after returning the organic fertilizer to the field contained four components: UV and UVA humic-like (C1), tryptophan-like and UVA humic-like (C2), Exogenous and visible humic-like (C3) and tyrosine-like (C4). Humus-like was the main component. (2) After applying organic fertilizer, the relative contents of the DOM humus and tyrosine-like components in the soil increased by 8% and 8.73%, respectively. In this process, the DOM electron-accepting capacity (EAC) and electron-donating capacity (EDC) increased by 39.98% and 27.91%, respectively. (3) The humic-like fraction showed a highly significant positive correlation with ETC (p &lt; 0.01), and the tyrosine-like fraction showed a significant negative correlation with ETC (p &lt; 0.05). (4) The humus-like substance and ETC were positively correlated with the total amount, reducible state and oxidizable state of the potential toxic elements and negatively correlated with the weak acid extracted state and residue state; this showed that the humus-like components and ETC were more helpful for the transformation of the weak acid extracted state to the reducible state, oxidizable state and residue state in the interaction between the DOM components and Cr, Pb and Cd. In summary, the reasonable application of organic fertilizer could improve the relative content of DOM and ETC in soil, inhibit the biological toxicity of potential toxic elements in soil and provide a theoretical basis for the safe use of organic fertilizer.

Modeling, Simulation, Optimization, and Experimental Verification of Mercury Removal onto Natural and Sulfur-Impregnated Zeolite Clinoptilolite—Assessment of Feasibility for Remediation of Mercury-Contaminated Soil

In this paper, a series of equilibrium and kinetic experiments of Hg(II) removal in a single-stage batch reactor on natural (NZ) and sulfur-impregnated zeolite (SZ) were performed. Batch sorption of Hg(II) on zeolites was studied using different isothermal and kinetic models. It was found to be best described by the Brouers-Sotolongo isotherm and the Vermeulen’s approximation, which were applied in optimizing the mass and contact time in two-stage cross-current and counter-current flow batch reactors based on the desired criterion of 99.9% removal efficiency. Mathematical models for minimizing zeolite mass and contact time were developed and experimentally verified. The optimum minimum masses of NZ and SZ were calculated for all systems, and a significant saving in SZ consumption was found when the counter-current design was applied. The toxicity characteristic leaching procedure (TCLP) was applied to mercury contaminated soil from the Idrija mine region in Slovenia to evaluate potential soil toxicity. The results showed that the soil is extremely contaminated and represents hazardous waste. The addition of zeolites significantly reduced the concentration of leached Hg, with the most satisfactory results obtained with SZ. It was found that at the lowest dose of 0.25 g of SZ, the leached Hg concentration was reduced below the maximum concentration criterion of 0.2 mg/L according to the TCLP test. This study revealed that SZ could be a potential sorbent for in situ remediation of mercury contaminated soil.

Soil amendments for vanadium remediation: a review of remediation of vanadium in soil through chemical stabilization and bioremediation.

Immobilization of vanadium (V) in soils is one option to prevent groundwater contamination and plant uptake. Phytoremediation, microbial remediation, and chemical stabilization using soil amendments are among the leading environmentally friendly and economically feasible techniques in V remediation. Soil amendments were used to reduce V mobility by immobilizing it in the soil matrix through chemical stabilization, while bioremediation methods such as phytoremediation and microbial remediation were used to remove V from contaminated soils. Vanadium exists in several species and among them V5+ species are the most prevalent, toxic, and soluble form and present as a negatively charged ion (H2VO4- and HVO42-) in oxic soils above pH 4. Amendments used for chemical stabilization can change the physicochemical properties enhancing immobility of V in soil. The pH of the soil environment, point of zero charge of the colloid surface, and redox conditions are some of the most important factors that determine the efficiency of the amendment. Commonly used amendments for chemical stabilization include biochar, zeolites, organic acids, various clay minerals and oxides of elements such as iron, titanium, manganese, and aluminum. For bioremediation, chelating agents and microbial communities are used to mobilize V to enhance phyto-or microbial-extraction procedures. The objectives of this review were to discuss remediation methods of V while considering V speciation and toxicity in soil, and soil amendment application for V removal from soil. The information compiled in this review can guide further research on soil amendments for optimal V remediation in largely contaminated industrial sites.

Effect of Carbide Slag Combined with Biochar on Improving Acidic Soil of Copper Sulfide Mines

Heavy metal-rich acidic soils of copper sulfide mines can easily cause harm to the surrounding environment and ecosystem safety if not treated properly. Currently, the most common method of mine ecological remediation is to improve acidic soils of copper sulfide mines by adding different types of amendments. In this paper, different dosages of biochar and carbide slag applied singly and in combination were designed to investigate the changes of physicochemical properties and ryegrass growth in the acidic soil of copper sulfide mines. Through soil incubation experiments and potting tests, different treatments explored the improvement effect of carbide slag combined with biochar on the acidic soil of copper sulfide mines. Then, it was found that 2% (w/w) carbide slag in combination with 10% (w/w) biochar had the best effect on the improvement of copper-sulfide mine acidic soil. Among them, carbide slag significantly increased the pH, cation exchange capacity (CEC) and acid neutralization capacity (ANC), and reduced the electrical conductivity (EC), net acid generation (NAG) and sulfate ion (SO42−) concentrations in the acidic soil of copper sulfide mines; biochar obviously reduced the bio-effectiveness of heavy metals Cu, Pb and Zn, and DPTA-Cu, Pb and Zn decreased by 8~80%, 7~76% and 17~79%, respectively. Apart from that, there was a positive cooperativity between carbide slag and biochar, and their application effectively controlled the acidification process and heavy metal toxicity in the acidic soil of copper sulfide mines. In summary, the results will provide a theoretical basis for the large-scale reclamation of carbide slag and biochar in improving acidic soils of copper sulfide mines, filling the gap of calcium carbide slag and biochar in soil remediation.

A Green Approach Used for Heavy Metals ‘Phytoremediation’ Via Invasive Plant Species to Mitigate Environmental Pollution: A Review

Heavy metals (HMs) normally occur in nature and are rapidly released into ecosystems by anthropogenic activities, leading to a series of threats to plant productivity as well as human health. Phytoremediation is a clean, eco-friendly, and cost-effective method for reducing soil toxicity, particularly in weedy plants (invasive plant species (IPS)). This method provides a favorable tool for HM hyperaccumulation using invasive plants. Improving the phytoremediation strategy requires a profound knowledge of HM uptake and translocation as well as the development of resistance or tolerance to HMs. This review describes a comprehensive mechanism of uptake and translocation of HMs and their subsequent detoxification with the IPS via phytoremediation. Additionally, the improvement of phytoremediation through advanced biotechnological strategies, including genetic engineering, nanoparticles, microorganisms, CRISPR-Cas9, and protein basis, is discussed. In summary, this appraisal will provide a new platform for the uptake, translocation, and detoxification of HMs via the phytoremediation process of the IPS.

Arsenic mobility and toxicity on soil acid phosphatase activity increased with added phosphorus in contaminated mine soils

AbstractSoil phosphatase activity is identified as sensitive to arsenic (As) pollution and therefore, often used as an indicator to estimate As toxicity in soil. Nevertheless, the effect of As on soil phosphatase activity after its desorption by P is not adequately studied. This study employed sequential extraction procedure and ecological dose parameters to show As mobility and its toxicity to acid phosphatase (AcP). Results indicated that P application significantly increased As desorption ratio in the As ageing process. In S1 (As 2895 mg kg−1) soil, after P addition, the water‐soluble (FWS) fraction had the highest proportion of As, while for S2 (As 645 mg kg−1) and S3 (As 39 mg kg−1) it was residual (FRES) fraction. Additionally, P addition increased the As bioavailability in all soils. Generally, P addition significantly reduced soil AcP activity under all P concentrations and increased in the soil with minimum As content. The variation partitioning analysis indicated that for S1, P concentration was the major factor, for S2 and S3 soils, it was As desorption and ageing time, respectively, that influenced the AcP activity in soils. The calculated ecological dose (ED50) showed that in most cases, As toxicity increased at the end of ageing. Thus, it is essential to control the phosphorus fertilizer applications in silty soils with acid and neutral pH, since it can lead to increased As mobility and toxicity to soil AcP.

Sustainable agricultural use of sewage sludge: impacts of high Zn concentration on on Folsomia candida, Enchytraeus crypticus, Lactuca sativa, and Phaseolus vulgaris.

Zinc (Zn) is an essential micronutrient for plants and an important component for maintaining soil quality. Commonly found in the soil due to anthropogenic activities, such as industrialization and application of organic waste as fertilizers, in high concentrations, Zn may induce soil toxicity, affecting important communities, such as edaphic fauna. Despite its high concentrations found in the environment, Zn bioavailability can be affected by the type of soil, organic matter content and pH. In this work, Zn had its toxicity evaluated in a natural tropical soil, sampled in São Paulo-Brazil, for two soil invertebrates (Folsomia candida, Enchytraeus crypticus) and two seeds (Lactuca sativa and Phaseolus vulgaris), through ecotoxicological tests. The invertebrate E. crypticus was exposed to Zn concentrations of 10.0 (T1); 100.0 (T2); 150.0 (T3); 200.0 (T4); 400.0 (T5) mg Zn kg-1 of dry soil, while F. candida, L. sativa and P. vulgaris were exposed to Zn concentrations of 100.0; 200.0; 400.0; 800.0 (t6); 1600.0 (t7); and 2000.0 (t8) mg Zn kg-1 of dry soil. The outcome evaluated were seed germination, for L. sativa and P. vulgaris, and reproduction, for F. candida and E. crypticus. The EC50 obtained for E. crypticus, F. candida, L. sativa, and P. vulgaris were 261.5, 1089.7, 898.5, and 954.5mg Zn kg-1 of dry soil, respectively, being E. crypticus the most sensitive organism, and only at the highest Zn's concentrations the organisms' reproduction and seeds' germination showed a statistically significant inhibitory effect (p < 0.05). Therefore, this work's results showed that Zn does not present significant toxicity for the tested soil organisms and seeds and that at 100mg Zn kg-1 of dry soil it can be beneficial to F. candida and E. crypticus' reproduction and L. sativa's germination. These results imply that the presence of Zn in low concentrations, both in soil and biofertilizers, such as sewage sludge, not only is not a concern, but it can even benefit certain crops and functions of edaphic organisms, which may contribute to the engagement of sustainable agricultural practices and the quest for food security.

Comparison of the Effectiveness of Micro- and Nanoparticles of Zero-Valent Iron in the Detoxification of Technogenic Polluted Soil

We studied the safety of sorbents based on zerovalent iron in the form of micro- and nanoparticles and their detoxifying activity in peat eutrophic soil (Eutric Histosol) polluted by emissions from a copper-nickel (Cu/Ni) plant (Kola Peninsula, Russia). Iron nanoparticles, as well as iron microparticles at a dose of 2%, turned out to be non-toxic according to the results of three standard bioassays based on the reactions of test organisms of different taxonomic affiliation. Toxicity was assessed by the change in the length of the roots of seedlings of plants Sinapis alba L. in uncontaminated peat, by the survival of Ceriodaphnia affinis Lilljeborg and the protozoan Parameciun caudatum Ehrenberg in water extracts of the samples. Fe-containing preparations significantly reduced the ecotoxicity of the soil due to the extremely high content of copper (6877 mg/kg) and nickel (2580 mg/kg). Differences in the remediating ability of the preparations were revealed. According to the results of soil phytotesting, iron nanoparticles significantly outperformed the detoxifying effect of microparticles (iron powder). When analyzing the water extract, the superiority of nanoparticles in reducing soil toxicity was not found. The dependence of the assessment of the detoxifying ability of zerovalent iron nanoparticles on soil properties and the plant species used in phytotesting is discussed.

Rice Soil Fertility Classification in the Mekong Delta, Vietnam

The rice crop intensification led to soil degradation and yield decline in the Mekong Delta, Vietnam. Therefore, it is necessary to classify soil fertility and identify the constraints for proper soil use. The soil legend classified by World Reference Based was converted to the Fertility Capability Classification system. The soil constraints and recommendations for appropriate services are suggested. The findings indicate seven primary soil categories, ten diagnostic layers, three diagnostic features, and three diagnostic materials in the rice soils of the Mekong Delta. Eleven soil constraints were found, most of which were associated with acid sulfate and saline soils. These constraints included low acidity, strong acidity, low available P, high P fixation, high potential Fe toxicity, slightly actual acid sulfate and shallow potential acid sulfate, deep potential acid sulfate, slight salinity, and strong salinity, low mineral supply capacity, limited organic carbon content, and low nutrient retention capacity. Reclamation of acid sulfate and saline soils by leaching soil toxicity and boosting soil nutritional status with organic matter and P, K treatment were recommended for degraded, acid sulfate, and saline soils.

Comparative assessment of environmental impacts, mitigation potentials, and economic benefits of rain-fed and irrigated apple production systems on China's Loess Plateau

Although the repaid development of China's apple industry heavily depends on excessive fertilizer-water-pesticide (FWP) inputs, little information is available that systematically evaluates environmental impacts, mitigation potential, and economical benefits of apple production systems in China. In this study, life cycle assessment (LCA) was conducted to elucidate environmental risks and mitigation potentials of rain-fed and irrigated apple production systems on China's Loess Plateau based on survey data from 847 farmers, and economic benefits were analyzed simultaneously. Results showed that irrigated orchards caused more severe environmental risks associated with energy depletion (ED), global warming potential (GWP) and acidification potential (AP) than those in rain-fed orchards, whereas an opposite was true for eutrophication potential (EP), human toxicity potential (HTP), aquatic toxicity potential (ATP) and soil toxicity potential (STP). ED and GWP occurred primarily in the agricultural material stage, while AP, EP, HTP, ATP, and STP occurred mostly in the orchard management stage. Optimized FWP management can markedly mitigate environmental impacts in both irrigated and rain-fed orchard systems. Synthetic fertilizer, because of production and field-associated emissions, was the greatest contributor to environmental impacts of an apple production system. An environmental pollution index (EPI) that integrated environmental categories was highest in conventional irrigated orchards (0.946), followed by conventional rainfed orchards (0.857), and optimized irrigated orchards (0.459), and the lowest EPI was in optimized rainfed orchards (0.389). Economic analysis revealed that the benefits of rainfed orchards were higher than those of irrigated orchards because of higher apple prices and lower labor costs. Optimized FWP management sharply decreased input costs, thereby substantially increasing net income in irrigated and rain-fed apple orchards. Overall, severe environmental risk and large mitigation potential co-exist in rain-fed and irrigated apple orchards on China's Loess Plateau. Integrated soil-crop-market management potentially exhibited considerable environmental and economic advantages, thereby efficiently developing high-quality apple production.