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Nanotechnology-based approaches have demonstrated encouraging results for sustainable agriculture production, particularly in the field of fertilizers and pesticide innovation. It is essential to evaluate the economic and environmental benefits of these nanoformulations. Here we estimate the potential revenue gain/loss associated with nanofertilizer and/or nanopesticide use, calculate the greenhouse gas emissions change from the use of nanofertilizer and identify feasible applications and critical issues. The cost-benefit analysis demonstrates that, while current nanoformulations show promise in increasing the net revenue from crops and lowering the environmental impact, further improving the efficiency of nanoformulations is necessary for their widescale adoption. Innovating nanoformulation for targeted delivery, lowering the greenhouse gas emissions associated with nanomaterials and minimizing the content of nanomaterials in the derived nanofertilizers or pesticides can substantially improve both economic and environmental benefits.

Formulations that include nanoparticles of CuO and ZnO are being considered for agricultural applications as fertilizers because they act as sources of Cu or Zn. Currently, few studies of the effects of these nanoparticles (NPs) consider the three-way interactions of NPs with the plant plus its microbiome. At doses that produced root shortening by both nanoparticles (NPs), CuO NPs induced the proliferation of elongated root hairs close to the root tip, and ZnO NPs increased lateral root formation in wheat seedlings (Triticum aestivum L.). These responses occurred with roots colonized by a beneficial bacterium, Pseudomonas chlororaphis O6 (PcO6), originally isolated from roots of wheat grown under dryland farming in calcareous soils. The PcO6-induced tolerance to drought stress in wheat seedlings was not impaired by the NPs. Rather, growth of the PcO6-colonized plants with NPs resulted in systemic increases in the expression of genes associated with tolerance to water stress. Increased expression in the shoots of other genes related to metal stress was consistent with higher levels of Cu and Zn in PcO6-colonized shoots grown with the NPs. This work demonstrates that plants grown with CuO or ZnO NPs showed cross-protection from different challenges such as metal stress and drought. Key words: beneficial bacterium, drought stress response, nanoparticles, root colonization. Des formules qui comportent du CuO et du ZnO a l'echelle nanometrique sont actuellement envisagees en vue d'applications agricoles comme fertilisant car elles agissent comme sources de Cu ou de Zn. En ce moment, peu d'etudes portant sur les effets de ces nanoparticules (NP) ont considere les interactions tripartites des NP avec la plante et son microbiome. A des doses qui provoquent un raccourcissement des racines par les deux types de nanoparticules, les NP de CuO induisaient une proliferation des poils racinaires allonges a proximite du bout de la racine et les NP de ZnO accroissaient la formation de racines laterales chez les jeunes pousses de ble (Triticum aestivum L.). Ces reponses survenaient avec des racines colonisees par une bacterie benefique, Pseudomonas chlororaphis O6 (PcO6), isolee a l'origine des racines de ble cultive en aridoculture dans des sols calcaires. La tolerance au stress de secheresse induite par PcO6 chez les jeunes pousses de ble n'etait pas diminuee par les NP. La croissance des plants colonises par PcO6 en presence de NP s'accompagnait plutot d'accroissements systemiques de l'expression de genes associes a la tolerance au stress hydrique. L'expression accrue d'autres genes relies au stress provoque par les metaux etait coherente avec les niveaux plus eleves de Cu et de Zn chez les pousses colonisees par PcO6 cultivees en presence de NP. Ce travail demontre que les plants cultives en presence de NP de CuO ou de ZnO presentent une protection croisee envers le stress provoque par les metaux et la secheresse. [Traduit par la Redaction] Mots-cles : bacterie benefique, reponse au stress de secheresse, nanoparticules, colonisation racinaire., Introduction Food security is a major factor addressing the world where population size, climate variability, urbanization of land, and water quality and supply are problematic. Drought is one of the [...]

Soil contaminated with creosote remains a potential carcinogenic source for a long time. Researchers sought to create a new test to characterize the bound reside formation process of (carbon 14)pyrene in contaminated soil. They also sought to evaluate the methyl isobutyl ketone (MIBK) fractionation method to predict biological activity upon the contaminants over time. Soil from the Champion International Superfund Site in Libby, CT formed the basis of these studies. The soil was also contaminated with pentachlorophenol, a wood preservative.

Laboratory tests were conducted to determine the effect of soil gas oxygen concentration on the degradation and mineralization of spiked 14C-pentachlorophenol and nonlabeled pentachlorophenol (PCP) present in soil taken from a prepared-bed land treatment unit at the Champion International Superfund Site in Libby, Mont. This soil was contaminated with wood preserving wastes including creosote and PCP. Degradation rates of 14C-PCP and nonlabeled PCP were found to be enhanced under soil gas oxygen concentrations between 2 and 21% in the contaminated soil. Between 48 and 64% of 14C-PCP spiked onto the soil was mineralized after 70 days at soil gas oxygen levels between 2 and 21%. No statistically significant mineralization of PCP was found to occur at 0% oxygen concentrations. Mineralization of 14C-PCP in contaminated soil poisoned with mercuric chloride was determined to be less than 0.2%. Degradation of indigenous nonradiolabeled PCP in the nonpoisoned soil was statistically significantly greater than in poisoned soil. These results indicated that degradation of PCP was biological and would occur under low oxygen concentrations. Soil gas oxygen concentrations necessary for PCP biodegradation (2-5%) could be maintained, for example, using bioventing technology in order to achieve continued treatment of buried lifts of soil while new lifts are added, thus decreasing the total time for soil remediation of the prepared bed.

Abstract Background Humic acid (HA) has been found to affect the solubility, mineralization, and bound residue formation of polycyclic aromatic hydrocarbons (PAHs). However, most of the studies on the interaction between HA and PAH concentrated on one or two of the three phases. Few studies have provided a simple protocol to demonstrate the overall effects of HA on PAH distribution in soil systems for all three phases. Methods In this study, three doses of standard Elliott soil HA (ESHA), 15, 187.5, and 1,875 μg ESHA/g soil slurry, were amended to soil slurry systems. 14C-pyrene was added to the systems along with non-radiolabeled pyrene; 14C and 14CO2 were monitored for each system for a period of 120 days. Results The highest amendment dose significantly increased the 14C fraction in the aqueous phase within 24 h, but not after that time. Pyrene mineralization was significantly inhibited by the highest dose over the 120-day study. While organic solvent extractable 14C decreased with time in all systems, non-extractable or bound 14C was significantly enhanced with the highest dose of ESHA addition. Conclusion Amendment of the highest dose of ESHA to pyrene contaminated soil was observed to have two major functions. The first was to mitigate CO2 production significantly by reducing 14CO2 from 14C pyrene mineralization. The second was to significantly increase stable bound 14C formation, which may serve as a remediation end point. Overall, this study demonstrated a practical approach for decontamination of PAH contaminated soil. This approach may be applicable to other organic contaminated environments where active bioremediation is taking place.

Abstract Background Remediation of tert-butyl alcohol (TBA) in subsurface waters should be taken into consideration at reformulated gasoline contaminated sites since it is a biodegradation intermediate of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-butyl formate (TBF). The effect of temperature on TBA biodegradation has not been not been published in the literature. Methods Biodegradation of [U 14C] TBA was determined using hyporheic zone soil microcosms. Results First order mineralization rate constants of TBA at 5°C, 15°C and 25°C were 7.84 ± 0.14 × 10-3, 9.07 ± 0.09 × 10-3, and 15.3 ± 0.3 × 10-3 days-1, respectively (or 2.86 ± 0.05, 3.31 ± 0.03, 5.60 ± 0.14 years-1, respectively). Temperature had a statistically significant effect on the mineralization rates and was modelled using the Arrhenius equation with frequency factor (A) and activation energy (Ea) of 154 day-1 and 23,006 mol/J, respectively. Conclusion Results of this study are the first to determine mineralization rates of TBA for different temperatures. The kinetic rates determined in this study can be used in groundwater fate and transport modelling of TBA at the Ronan, MT site and provide an estimate for TBA removal at other similar shallow aquifer sites and hyporheic zones as a function of seasonal change in temperature.

Considers the low incidence of active questioning by students in elementary school and points out techniques teachers can use to encourage active questioning. (Author/RH)

In the present study, the relative distribution of endophytic rhizobia in field-collected root nodules of the promiscuous host mung bean was investigated by sequencing of 16S ribosomal RNA (rRNA) and nifH genes, amplified directly from the nodule DNA. Co-dominance of the genera Bradyrhizobium and Ensifer was indicated by 32.05 and 35.84% of the total retrieved 16S rRNA sequences, respectively, and the sequences of genera Mesorhizobium and Rhizobium comprised only 0.06 and 2.06% of the recovered sequences, respectively. Sequences amplified from rhizosphere soil DNA indicated that only a minor fraction originated from Bradyrhizobium and Ensifer strains, comprising about 0.46 and 0.67% of the total retrieved sequences, respectively. 16S rRNA gene sequencing has also identified the presence of several non-rhizobial endophytes from phyla Proteobacteria, Actinobacteria, Bacteroides, and Firmicutes. The nifH sequences obtained from nodules also confirmed the co-dominance of Bradyrhizobium (39.21%) and Ensifer (59.23%) strains. The nifH sequences of the genus Rhizobium were absent, and those of genus Mesorhizobium comprised only a minor fraction of the sequences recovered from the nodules and rhizosphere soil samples. Two bacterial isolates, identified by 16S rRNA gene sequence analysis as Bradyrhizobium strain Vr51 and Ensifer strain Vr38, successfully nodulated the original host (mung bean) plants. Co-dominance of Bradyrhizobium and Ensifer strains in the nodules of mung bean indicates the potential role of the host plant in selecting specific endophytic rhizobial populations. Furthermore, successful nodulation of mung bean by the isolates showed that strains of both the genera Bradyrhizobium and Ensifer can be used for production of inoculum. [ABSTRACT FROM AUTHOR]