Aerobic Soil Research Articles

The Impact of Different Planting Systems on the Bacterial Diversity of Rice Cultivated in Saline Soil Based on 16S rRNA Gene-Based Metagenomic Insights

Soil salinity is considered to be a major impediment to the production of rice among other abiotic stresses. In this study, 16S rRNA Illumina amplicon sequencing was performed to characterise the halophilic communities entrapped in rice rhizosphere soil cultivated in different planting systems (conventional, aerobic and System of Rice Intensification (SRI)) under saline conditions. The physicochemical properties and urease, soil dehydrogenase, alkaline phosphatase and arylsulphatase activity of soil samples were evaluated to understand their influence on the bacterial communities of the soil. Electrical conductivity (EC) of soil was lower in SRI soil samples, while the available major soil nutrients (nitrogen, phosphorous and potassium) content and soil enzyme activities such as dehydrogenase, alkaline phosphatase, urease and arylsulphatase were higher. A total of 2,516,700 reads were generated by amplicon sequencing of the hypervariable V3–V4 regions of bacterial 16S rRNA gene and were clustered into 273,447 OTU operational taxonomic units. The total number of Operational Taxonomic Units (OTUs) was higher in the conventional soil samples compared to the SRI and aerobic soil samples. Metagenomic analysis revealed that Proteobacteria was the most dominant phyla in all the planting systems followed by Actinobacteria, Firmicutes and Chloroflexi. The alpha diversity index was higher in conventional soil samples compared to other samples and more species diversity was found in SRI soil samples. KEGG analysis revealed that bacterial communities in different soil samples showed varied functional properties. The bacterial diversity of saline soil in this study can be utilised to identify microbial communities with biotechnological potential that can be employed for plant growth promotion in saline environments.

In silico analysis of soil, sediment and groundwater microbial communities to predict biodegradation potential

This study examined soil, sediment and groundwater microbial communities for a set of key functional genes important for contaminant biodegradation. This involved PICRUSt2 (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) predictions based on 16S rRNA gene amplicon datasets from three separate studies with different inocula and incubation conditions, as follows: aerobic soils, oxygen-limited microcosms containing sediments and groundwater, as well as methanogenic microcosms with different inocula. PICRUSt2 predicts functional profiles of microbial communities based on marker gene (16S rRNA gene) data. The relative abundances of genera previously associated with the biodegradation of chlorinated solvents/metabolites and/or 1,4-dioxane were also determined.Predicted values for each functional gene varied between the three datasets. In all, values were high for propane monooxygenase and low for soluble methane monooxygenase. Common phylotypes associated with propane monooxygenase in two of the three datasets included Mycobacterium, Rhodococcus and Pseudonocardia. Toluene monooxygenase predicted values were greater in the oxygen-limited microcosms compared to the other two datasets. The methanogenic microcosms exhibited the highest predicted values for particulate methane/ammonia monooxygenase. The most common genera detected, previously reported as chlorinated solvents/metabolites and/or 1,4-dioxane degraders, included Pseudomonas, Sphingomonas, Rhodococcus and Rhodanobacter. Eighteen of the queried genera were not detected. As expected, more potential anaerobic degrading genera were found in the oxygen-limited and methanogenic microcosms compared to the aerobic soils. The results provide key insights as to which genes and genera may be important for biodegradation over a range of inocula and redox conditions.

Impact of Compost Tea and Spirulina platensis Algae on Sugar Beet Grown under Different Levels of Inorganic Nitrogen Fertilizer.

<b>Background and Objective:</b> Nitrogen is an essential macronutrient for plant growth, improving the absorption and utilization of some other nutrients and controlling total plant development. Compost tea (CT) is an aqueous extract of compost that contains high organic matter levels necessary for plants and aerobic soil microorganisms. <i>Spirulina platensis</i> is a multi-cellular blue-green micro-alga that contains green pigments, high levels of nutrients and plant growth regulators. This work was designed to study the possibility of using CT and <i>S. platensis</i> algae culture filtrate (ACF) in improving plant growth, yield and quality of sugar beet grown under different nitrogen fertilizer levels. <b>Materials and Methods:</b> Two field experiments were conducted at Ismailia Research Station, Ismailia Province, Egypt, during the 2019/2020 and 2020/2021 seasons. The study involved two N levels (90 and 120 kg/fed), three CT rates (without, 30 and 60 l/fed) and three ACF levels (without, 1 and 2 l/fed) three times. A split-plot design was used. <b>Results:</b> Adding 120 kg N/fed increased crop growth rate (CGR), root yield/fed (RY) and sugar yield/fed (SY), while, sucrose (%) and quality index (QI) decreased. Soil drench with 60 l CT/fed incremented leaf area index (LAI), CGR, sucrose (%), RY and SY. Increasing ACF level up to 2 l/fed increased LAI, sucrose (%), QI, RY and SY. Root yield was positively correlated with SY and negatively with QI. <b>Conclusion:</b> Applying 90 kg N/fed combined with a soil drench of 60 l CT/fed and foliar spraying with 2 l ACF/fed thrice can be recommended to attain economical root and sugar yields.

Can As concentration in crop be controlled by Se fertilization? A meta-analysis and outline of As sequestration mechanisms.

Arsenic (As) is a pollutant with a strong toxic effect on animals, plants and human beings. Exogenous selenium (Se) has been suggested to reduce the accumulation of As in crops, but contradictory results were found in the published literature. In order to clarify the possible processes, we collected the literature that reports on the effects of Se application on As uptake and accumulation in crops, analyzed the data by meta-analysis, and tested the effects of different factors on As accumulation by meta-regression model and subgroup analysis. The results highlighted a significant dose-dependent reduction of As content in crops after Se addition. Exogenous Se can significantly reduce As concentrations in grains by 18.76%. The reduction was dose-dependent for rice grains under aerobic soil conditions but not for rice grains under anoxic soil conditions. Se-enriched soils (greater than 0.5 mg kg-1) significantly reduced As concentrations in grains. Selenium significantly decreased the transfer factor of As from root to shoot. Moreover, selenite had a stronger inhibiting effect on the transport of As from root to shoot than selenate. The inhibition of selenium fertilization on As concentrations seems to take place in root and soil, while physiological processes in rice may be involved in restricting uptake and transport from root to shoot. These findings provide new ideas for effectively alleviating the transfer of As to the human body through the food chain.

Public health threats of diminished treatment of onsite sewage

Public health threats of diminished treatment of onsite sewage

QTL Pyramiding and Its Use in Breeding for Increasing the Phytoextraction Efficiency of Soil Cd via High-Cd-Accumulating Rice.

Phytoextraction by high-Cd-accumulating rice lacking a functional OsHMA3 allele is promising for Cd removal from paddy soils. To increase rice Cd extraction efficiency, we developed a new high-Cd variety, TJN25-11. For this, we pyramided a nonfunctional OsHMA3 allele from a high-Cd variety, Jarjan, and two QTLs for increased shoot Cd concentrations, which were discovered in a mapping population derived from a high-Cd variety, Nepal 555, and a low-Cd variety, Tachisugata. In two Cd-contaminated paddy fields under drained aerobic soil conditions, TJN25-11 presented significantly higher Cd concentrations in the straw and panicles than the OsHMA3-deficient varieties TJTT8 and Cho-ko-koku. Among the varieties, TJN25-11 had a relatively high shoot biomass, resulting in the highest Cd accumulation in the shoots. The soil Cd decreased by approximately 20% after TJN25-11 growth. The amount of Cd that accumulated in the TJN25-11 aerial parts was much greater than the amount of Cd that decreased in the topsoil, suggesting that Cd was absorbed from deeper soil layers. Thus, we revealed the effects of QTL pyramiding on shoot Cd accumulation and Cd phytoextraction efficiency. Since TJN25-11 has favorable agronomic traits for compatibility with Japanese cultivation systems, this variety could be useful for Cd phytoextraction in Cd-contaminated paddy fields.

Occurrence of methylmercury in aerobic environments: Evidence of mercury bacterial methylation based on simulation experiments

Methylmercury (MeHg) is mainly produced by anaerobic δ-proteobacteria such as sulfate-reducing bacteria (SRB). However, mercury bio-methylation has also been found to occur in the aerobic soil of the Three Gorges Reservoir (TGR). Using γ-proteobacterial TGR bacteria (TGRB) and δ-proteobacterial Desulfomicrobium escambiense strains, the efficiency of mercury methylation and demethylation was evaluated using an isotope tracer technique. Kinetics simulation showed that the bacterial Hg methylation rate (km) of TGRB3 was 4.36 × 10−9 pg·cell−1·h−1, which was significantly lower than that of D. escambiense (170.74 ×10−9 pg·cell−1·h−1) under anaerobic conditions. Under facultative and/or aerobic conditions, D. escambiense could not survive, while the km of TGRB3 were 0.35 × 10−9 and 0.29 × 10−9 pg·cell−1·h−1, respectively. Furthermore, the bacterial MeHg tolerance threshold of TGRB3 was 3.47 × 10−9 pg·cell−1, which was 98.6-fold lower than that of D. escambiense under anaerobic conditions. However, the MeHg tolerance threshold of TGRB3 remained at 0.50–0.52 × 10−9 pg·cell−1 under facultative and/or aerobic conditions. Notably, bacterial Hg methylation rates (km) were higher than the corresponding bacterial MeHg demethylation rates (kd1). These results establish the contribution of some aerobic and/or facultative anaerobic bacteria to net environmental MeHg production in terrestrial ecosystems and provide a novel understanding of the biogeochemical cycle of MeHg. SynopsisHg methylation of facultative and/or aerobic bacteria may contribute to the net production of environmental methylmercury in terrestrial ecosystems.

Unraveling the Reaction Mechanism of Mo/Cu CO Dehydrogenase Using QM/MM Calculations

Some microorganisms, like the aerobic soil bacteria, Oligotropha carboxidovorans, have the capability to oxidize the highly toxic atmospheric gas carbon monoxide (CO) into CO2 through CO dehydrogenase enzymes, whose active site contains a bimetallic MoCu center. Over the last decades, a number of experimental and theoretical investigations were devoted to understanding the mechanism of CO oxidation and, in particular, the role of a very stable thiocarbonate intermediate that may be formed during the catalytic cycle. The occurrence of such an intermediate was reported to make the CO2 release step kinetically difficult. In this work, by using an accurate QM/MM approach and energy refinement by means of the BigQM method, we were able to determine the role of such an intermediate and propose a novel mechanism for the oxidation of CO into CO2 by Mo/Cu CO dehydrogenase. Surprisingly, we found that the detachment of CO2 occurs directly from the product of the Mo═O nucleophilic attack reaction on the carbon of CO aided by the transient coordination of the active site glutamate to the Mo ion. The estimated activation barrier is in good agreement with the experimental one, while the thiocarbonate turned out to not interfere with the CO-oxidation catalytic cycle. The results highlight the importance of the environmental effects in the assembly of the molecular model and in the choice of the computational protocol. Our accurate modeling of the enzyme also allowed us to exclude the involvement of a frustrated Lewis pair in the CO-oxidation mechanism, which has recently been suggested based on an analysis of structural and electronic features of synthetic mimics of the Mo/Cu CO dehydrogenase active site.

Methane emissions from forested closed landfill sites: Variations between tree species and landfill management practices

Trees in natural and managed environments can act as conduits for the transportation of methane (CH4) from below ground to the atmosphere, bypassing oxidation in aerobic surface soils. Tree stem emissions from landfill sites exhibit large temporal and spatial variability in temperate environments and can account for approximately 40% of the total surface CH4 flux. Emission variability was further investigated in this study by measuring CH4 and CO2 fluxes from landfill sites with different management strategies and varying tree species over a 7-month period. Stem and soil measurements were obtained using flux chambers and an off-axis integrated cavity output spectroscopy analyser. Analysis showed average stem and soil CH4 emissions varied significantly (p < 0.01) between landfills with different management practices. On average, tree stem CH4 fluxes from sites with no clay cap but gas extraction, clay cap and gas extraction, and no clay cap and no gas extraction were 1.4 ± 0.4 μg m−2 h−1, 47.2 ± 19.0 μg m−2 h−1, and 111.9 ± 165.1 μg m−2 h−1, respectively. There was no difference in stem CH4 fluxes between species at each site, suggesting environmental conditions (waterlogging) and site age had a greater influence on both stem and soil fluxes. These results highlight the importance of management practices, and the resultant environmental conditions, in determining CH4 emissions from historic landfill sites.

Combined morpho-physiological, ionomic and transcriptomic analyses reveal adaptive responses of allohexaploid wheat (Triticum aestivum L.) to iron deficiency

BackgroundPlants worldwide are often stressed by low Fe availability around the world, especially in aerobic soils. Therefore, the plant growth, seed yield, and quality of crop species are severely inhibited under Fe deficiency. Fe metabolism in plants is controlled by a series of complex transport, storage, and regulatory mechanisms in cells. Allohexaploid wheat (Triticum aestivum L.) is a staple upland crop species that is highly sensitive to low Fe stresses. Although some studies have been previously conducted on the responses of wheat plants to Fe deficiency, the key mechanisms underlying adaptive responses are still unclear in wheat due to its large and complex genome.ResultsTransmission electron microscopy showed that the chloroplast structure was severely damaged under Fe deficiency. Paraffin sectioning revealed that the division rates of meristematic cells were reduced, and the sizes of elongated cells were diminished. ICP-MS-assisted ionmics analysis showed that low-Fe stress significantly limited the absorption of nutrients, including N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, and B nutrients. High-throughput transcriptome sequencing identified 378 and 2,619 genome-wide differentially expressed genes (DEGs) were identified in the shoots and roots between high-Fe and low-Fe conditions, respectively. These DEGs were mainly involved in the Fe chelator biosynthesis, ion transport, photosynthesis, amino acid metabolism, and protein synthesis. Gene coexpression network diagrams indicated that TaIRT1b-4A, TaNAS2-6D, TaNAS1a-6A, TaNAS1-6B, and TaNAAT1b-1D might function as key regulators in the adaptive responses of wheat plants to Fe deficiency.ConclusionsThese results might help us fully understand the morpho-physiological and molecular responses of wheat plants to low-Fe stress, and provide elite genetic resources for the genetic modification of efficient Fe use.

Taxonomic and functional trait-based approaches suggest that aerobic and anaerobic soil microorganisms allow the natural attenuation of oil from natural seeps

Natural attenuation, involving microbial adaptation, helps mitigating the effect of oil contamination of surface soils. We hypothesized that in soils under fluctuating conditions and receiving oil from seeps, aerobic and anaerobic bacteria as well as fungi could coexist to efficiently degrade hydrocarbons and prevent the spread of pollution. Microbial community diversity was studied in soil longitudinal and depth gradients contaminated with petroleum seeps for at least a century. Hydrocarbon contamination was high just next to the petroleum seeps but this level drastically lowered from 2 m distance and beyond. Fungal abundance and alpha-diversity indices were constant along the gradients. Bacterial abundance was constant but alpha-diversity indices were lower next to the oil seeps. Hydrocarbon contamination was the main driver of microbial community assemblage. 281 bacterial OTUs were identified as indicator taxa, tolerant to hydrocarbon, potentially involved in hydrocarbon-degradation or benefiting from the degradation by-products. These taxa belonging to lineages of aerobic and anaerobic bacteria, have specific functional traits indicating the development of a complex community adapted to the biodegradation of petroleum hydrocarbons and to fluctuating conditions. Fungi are less impacted by oil contamination but few taxa should contribute to the metabolic complementary within the microbial consortia forming an efficient barrier against petroleum dissemination.

Assessment of using solid residues of fish for treating soil by the biosolarization technique as an alternative to soil fumigation

Organic food-waste is an ever growing environmental, economic, and social problem. One way to address this problem is to find new ways to valorise food waste in a circular economical manner. In this study, the concept of separating food from waste at its source in eateries was applied to obtain separated fish waste residues from the general waste of our university's canteen. This study is the first known attempt to use separated fish residues as soil amendments for soil biosolarization (SBS), a soil treatment method which is an environment-friendly alternative to chemical fumigation of soil. In this study a unique laboratory simulation system was used which mimics the conditions of field temperature, monitors the soil respiration and the follows the temporal profile of emitted volatile organic compounds. The fish waste residues were used as soil amendment in 2% wt. and the results showed elevated levels of aerobic soil respiration without unwanted CH4 emission. A different profile of volatile organic compounds (VOCs) was also identified in the soils treated with fish residues. The profile of volatiles found in the soil with fish residues included changes in the amounts of compounds such as: Dimethylsulfide, Methanethiol and C9-aldehydes that have been found to supress soilborne plant pathogens. This is the first indication that VOCs can be used as indicators for the SBS process. Greenhouse studies and analyses of soils treated by fish residues showed no soil residual phytotoxicity affecting later growth of lettuce seedlings while not hindering the herbicidal effect of SBS on unwanted Bidens (Bidens pilosa) weeds. These results indicate that fish waste residues can be used as a soil amendment in the SBS process.

Methane emissions from trees planted on a closed landfill site.

Trees have morphological adaptations that allow methane (CH4) generated below ground to bypass oxidation in aerobic surface soils. This natural phenomenon however has not been measured in a landfill context where planted trees may alter the composition and magnitude of CH4 fluxes from the surface. To address this research gap, we measured tree stem and soil greenhouse gas (GHG) emissions (CH4 and CO2) from a closed UK landfill and comparable natural site, using an off-axis integrated cavity output spectroscopy analyser and flux chambers. Analyses showed average CH4 stem fluxes from the landfill and non-landfill sites were 31.8 ± 24.4 µg m–2 h–1 and –0.3 ± 0.2 µg m–2 h–1, respectively. The landfill site showed seasonal patterns in CH4 and CO2 stem emissions, but no significant patterns were observed in CH4 and CO2 fluxes at different stem heights or between tree species. Tree stem emissions accounted for 39% of the total CH4 surface flux (7% of the CO2); a previously unknown contribution that should be included in future carbon assessments.

Investigating the arable land that is the main contributor to global warming between paddy and upland vegetable crops under excessive nitrogen fertilization

Methane (CH4) and nitrous oxide (N2O) have been considered as two of the major greenhouse gases (GHGs) from agricultural land. CH4 is normally emitted from water-logged paddy fields, while N2O is emitted from aerobic upland soils. Both of these arable lands are thought to be major GHG emission sites; however, the type of land that is responsible for the highest contribution to GHG emissions in the same region has not been studied. A two-year field study was conducted to calculate the contributions to global warming of rice paddy fields and red pepper cultivation in upland soil under different nitrogen (N) fertilization levels. Urea was applied as a source of nitrogen at four different levels (0, 50, 100, and 200% of the recommended doses for cultivation), and rice and red pepper were cultivated in paddy and upland fields, respectively, from May to October. CH4 and N2O were measured from both arable lands to quantify GHG fluxes.The CH4 emissions increased in a quadratic response with increasing nitrogen application level in rice paddy fields and upland soil, but rice paddies had significantly higher CH4 emissions than red pepper upland soils. In contrast, N2O emissions showed a linear correlation with increasing N fertilization level in both arable lands; however, upland soil showed significantly higher N2O emissions than rice paddy fields. The rice paddy field had much higher global warming potential (GWP) than upland soil under low levels of N fertilization (below 265 kg N ha−1) according to a carbon dioxide (CO2) equivalent comparison. However, upland soil showed a clearly higher GWP than rice paddy fields under excessive N fertilization. Therefore, we concluded that upland vegetable crops contributed the most to the GHG emissions caused by high N2O fluxes under excessive N fertilizer application.

Irrigation and phosphorous fertilization management to minimize rice grain arsenic content

This research sought to minimize inorganic arsenic levels in polished rice grain by using different irrigation and phosphorous fertilization practices while also maintaining crop yield and water productivity. Two experiments were conducted during seasons 2018–2019 and 2019–2020 using a split-plot design with three blocks, five irrigation treatments (main-plots) and two phosphorous levels (sub-plots). Irrigation treatments consisted of a traditional continuous flood (CF) control and four alternatives irrigation techniques with one or two drying events during the irrigation cycle. The phosphorous fertilization levels investigated were an unfertilized control (0 kg P2O5 ha−1) and the recommended fertilization level of 50 kg P2O5 ha−1. Soil pH and redox potentials were measured in each treatment. Strategically-timed, low severity drying events were effective at achieving aerobic soil conditions, resulting in Eh values over 50 mV. The alternative irrigation treatment with two drying events, implemented at panicle initiation and full flowering, was the most effective in reducing inorganic arsenic in grain without affecting grain yield or the amount of irrigation water applied. This irrigation technique could be considered as an alternative management to the traditional continuous flooded to reach minimal inorganic arsenic accumulation in grain in order to attend special quality standards or specific market requirements. Accumulated inorganic arsenic in grain was below international maximum levels in all analyzed samples, with an average value of 0.084 mg kg−1.

Biofertilizing Effects of Anabaena cylindrica Biomass on the Growth and Nitrogen Uptake of Wheat

ABSTRACT There are a substantial number of studies on the biofertilization effects of cyanobacteria in rice paddy fields, mainly attributed to biological fixation of N2, but not much attention has been given to their fertilizing capacity in aerobic soils. Few studies have used solid media (i.e. a soil) when testing the plant-growth-promoting effects of microalgae on plants, and particularly on wheat. The purpose of this study was to test the biofertilizing effect of a filamentous cyanobacterium, previously isolated from an agricultural soil, in order to evaluate the potential substitution of chemical fertilizers and to test its phyto-stimulating capacity. Seedlings of Triticum aestivum were grown in pots with a peat-vermiculite mixture (1:1 weight basis) in an experiment designed as a complete randomized block, consisting of four treatments and with four replicates each: a pure culture of Anabaena cylindrica concentrated by centrifugation to 2 g dry matter L−1 (treatment B); spent cyanobacteria growth medium filtered at 0.22 µm (treatment F); harvested cyanobacterial mat re-suspended in distilled water (treatment WB); and distilled water as a control (treatment W). Aboveground wheat plant mass was improved by 40% in both treatments with cyanobacterial biomass (B and WB), as compared to the control (W) and filtrate (F), demonstrating that the co-cultivation with living cyanobacterial biomass was key to plant improvement. Chlorophyll contents were also increased by nearly 50% and nitrogen by over 10% in the treatment WB, clearly indicating that nutrients in the filtrate were irrelevant to the beneficial effects on plant growth.

Fate of the neonicotinoid insecticide cycloxaprid in different soils under oxic conditions

Neonicotinoids are the most widely used pesticides worldwide due to their high toxicity to invertebrates. However, these compounds also increase the probability of environmental contamination. Cycloxaprid (CYC) is a promising neonicotinoid due to its insecticidal effectiveness and low cross resistance, but little is known about its fate in soils. Using radioisotope tracing techniques, the fate of 14C-labeled CYC enantiomers and racemic mixtures in aerobic soil was investigated in this research. After 100 d of incubation, the extractable residue (ER) of CYC decreased from 89.6% to 36.4% in red clay soil, from 46.1% to 10.1% in yellow loam soil, and from 93.2% to 12.2% in coastal saline soil. The radioactivity was substantially lower in methanol than in the other two solvents, but the distribution of CYC ER in various solvents across the three soils dramatically differed. The fraction of radioactive CYC that diffused into bound residue (BR) in the three soils increased over time to 56.8–83.0%. The variability in BR was influenced by soil properties such as organic matter concentration, pH, and residual microbial activity. Among the soils, yellow loam soil had the greatest tendency (53.0–83.0%) to form BR, while red clay soil showed the lowest capacity (7.5–61.2%). Cumulative mineralization (MI) to 14CO2 accounted for 0.12–0.23%, 6.69–7.31% and 14.82–20.06% in acidic soil, neutral soil and alkaline soil, respectively, which suggests that the environmental fate of chiral pesticides may be influenced by soil pH. No stereoselective behavior was detected in this study. These findings provide a framework to assess the environmental impact and ecological safety of CYC application.

Environmental fate studies with 14C-polyoxyethylene tallow amine (POE-T) to characterize environmental exposure and inform environmental risk assessments

Polyoxyethylene tallow amine (POE-T) is a member of the polyoxyethylene alkylamine (POEA) class of nonionic surfactants and is a component of some glyphosate-based formulations. The presence of POE-T improves foliar uptake of glyphosate in weeds, thereby reducing the amount of glyphosate needed for weed control. To further characterize the environmental fate of POE-T, aerobic soil degradation, hydrolysis, adsorption/desorption, and aerobic aquatic degradation studies were conducted according to U.S. EPA and OECD pesticide regulatory testing guidelines. POE-T labeled with carbon-14 was used in the studies to aid in analysis, assess mineralization to CO2, and allow for mass balance determinations. The aerobic soil half-lives (DT50) for POE-T ranged from 20 to 166 days with DT50 values increasing with increasing soil percent organic carbon (OC). POE-T was hydrolytically stable at pH 4–9. POE-T adsorbed strongly to soil (KFocads = 17,600–114,000) with sorption generally increasing as soil percent OC increased. The aerobic aquatic (water-sediment) system DT50s for POE-T were 14–29 days, with POE-T dissipating from the water column with DT50s of 0.10–0.12 days through metabolism and adsorption to sediment. Based on these results, aquatic organisms are unlikely to be exposed to POE -T in the water column for more than a few hours following waterborne exposure and sediment is a significant sink for POE-T in aquatic systems. However, bioavailability of POE-T in sediment and soil is predicted to be low based on strong adsorption and it is not readily desorbed.

Remediation of Agricultural Soils with Long-Term Contamination of Arsenic and Copper in Two Chilean Mediterranean Areas

Soil amendments may decrease trace element accumulation in vegetables, improving food security and allowing the recovery of contaminated farmlands. Despite some promising results in the laboratory, validation of soil amendments in field conditions are scarce, especially in aerobic soils. Here, we assessed the effect of different potential soil amendments on arsenic (As) accumulation in lettuces. Then, we compared them in terms of food security and the associated investment (efficacy and efficiency, respectively). We also hypothesized that the soil amendments do not lead to side effects, such as yield decrease, phytotoxicity of Cu, or undesired changes in soil properties. Thereby, we assessed lettuces grown on untreated contaminated soils (C+), treated contaminated soils, and untreated uncontaminated soils (C−) in two contrasting soil types (sandy and loamy soils). The treated contaminated soils consisted of multiple soil amendments. Soil amendments were: diammonium phosphate (DP), iron sulfate (IS), ferrous phosphate (FP), calcium peroxide (CP), and organic matter (OM). We found that phosphate amendments (DP and FP) reduced the As in edible tissues of lettuce in both areas, while CP only reduced As accumulation in the sandy soils area. The As intake through lettuces grown on these amended soils was about 30% lower than on the unamended ones. Cu concentrations in lettuces above 25 mg kg−1 grown in contaminated soils without reducing growth were found, a result that differed from non-field studies.

Complete Genome Sequence of Rhodococcus opacus Strain MoAcy1 (DSM 44186), an Aerobic Acetylenotroph Isolated from Soil.

ABSTRACTWe report the genome of Rhodococcus opacus strain MoAcy1 (DSM 44186), an aerobic soil isolate capable of using acetylene as its primary carbon and energy source (acetylenotrophy). The genome is composed of a single circular chromosome of ∼8 Mbp and two closed plasmids, with a G+C content of 67.3%.