Enhanced Dechlorination of 1,2-Dichloroethane by Coupled Nano Iron-Dithionite Treatment

1,2-dichloroethane (1,2-DCA) is a chlorinated solvent classified as a probable human carcinogen. Due to its extensive industrial applications, widespread contamination and recalcitrance towards abiotic dechlorination, 1,2-DCA remains a challenging compound for the remediation community and one of the great research interests. Batch experiments combining bimetallic or monometallic nZVI (stabilized or non-stabilized) with sodium dithionite were conducted for the degradation of 1,2-DCA. These experiments have yielded up to 92 % degradation of the initial 1,2-DCA concentration over the course of a year. Observed pseudo-first order rate constants (kobs) range from 3.8 x 10-3 to 7.8 x 10-3 day-1. Degradation was also achieved using magnetite and iron sulfide as the metal surface, with kobs values of 6.2 x 10-3 and 4.7 x 10-3 day-1, respectively. Characterization analysis of the nZVI/dithionite nanoparticles shows that zero valent iron as such remains in solution after more than one year of reactivity and that iron sulfide is formed in solution. This novel treatment represents the first nZVI-based formulation to achieve nearly complete degradation of 1,2-DCA

Field-Scale Implementation of Sulfidated Nano Zerovalent Iron for In-Situ Remediation

As far back as the mid-1990s, biogenic sulfidation has been observed during the implementation of iron-based materials for groundwater remediation. This phenomenon has largely been a consequence of natural biogeochemical processes and the prospects of utilizing engineered sulfidated zerovalent iron (ZVI) particles – nano- and/or micro- sized – were not extensively explored. More recently sulfidation of zerovalent iron (ZVI) particles has received considerable attention, highlighting the benefits that engineered/abiotic sulfidation can offer to nZVI, but to date, no field demonstration of the technology has been conducted. The first part of this thesis aims to report the unique challenges and unanswered questions that remain in relation to the emplacement of S-nZVI. nZVI was synthesized on-site using sodium borohydride (NaBH4) and stabilized with carboxymethylcellulose (CMC). Sulfidation was performed in an aqueous-solid fashion with sodium dithionite (Na2S­2O4) as the sulfidating agent. The slurry was gravity fed into a non-native sandy material by a designated injection well. Multiple monitoring wells were installed upstream and downstream of the injection well to monitor particle breakthrough and changes in the aquifer system. In terms of performance, the study suggests the on-site synthesized S-nZVI is mobile in the subsurface. Transport of S-nZVI to the monitoring wells, both downgradient and upgradient, resulted in a significant shift in aqueous phase concentrations of chlorinated volatile organic compounds (cVOCs). Compound specific isotope analysis (CSIA), changes in concentrations of intermediate degradation products, and the increase of ethene concentrations confirmed cVOC dechlorination. The field demonstration was followed by a bench – scale study on the aging characteristics and reactivity of S-nZVI. Particles were aged in dithionite immediately after synthesis (i.e., without washing). Aged S-nZVI remained reactive towards trichloroethene (TCE) after a 21-day aging period. Results from the aging study suggest particles synthesized on-site under these conditions could remain operational after extended storage. As knowledge of this growing area increases, this work presents foundational material on field-application of S-nZVI. Results from this field demonstration show sulfidation is a suitable amendment for the development of more efficient nZVI-based treatments for in-situ remediation

Age and growth of the Amazonian migratory catfish Brachyplatystoma rousseauxii in the Madeira River basin before the construction of dams

The goliath catfish Brachyplatystoma rousseauxii has crucial economical and ecological functions in the Amazon basin. Although its life history characteristics have been studied in the Amazon, there is little information in the Madeira River basin, which holds genetically distinct populations and where dams were recently built. Using fish collected in Bolivia, Brazil and Peru, this study provides a validation of growth rings deposition and details the growth patterns of B. rousseauxii in the Madeira before the dams' construction. Age structure and growth parameters were determined from 497 otolith readings. The species exhibits two growth rings per year and sampled fish were between 0 and 16 years old. In the Brazilian portion of the basin, mainly young individuals below 5 years old were found, whereas older fish (> 5 years) were caught only in the Bolivian and Peruvian stretches, indicating that after migrating upstream to reproduce, adults remain in the headwaters of the Madeira River. Comparing with previous publications, B. rousseauxii had a slower growth and 20 cm lower maximum standard length in the Madeira River than in the Amazon River. This study provides a baseline for future evaluation of changes in population dynamics of the species following dams closure.Santo Antonio Energia (SAE)Universidade Federal de Rondonia (UNIR)Instituto de Estudos e Pesquisas Agroambientais e Organizacoes Sustentaveis (IEPAGRO)CAPES [1402376, 047/2012, 6632/14-9]CNPq [204344/2015-8]Foundation of Support to Research of the Amazon [PAREV/FAPEAM 019/2010]FAPESP (Sao Paulo Research Foundation) [2016/07910-0]Univ Fed Rondonia UNIR, Dept Biol, Lab Ictiol & Pesca, BR 364,Km 9,5, BR-76801059 Porto Velho, RO, BrazilPrograma Posgrad Rede Biodiversidade & Biotechnol, BR 364,Km 9,5, BR-76801059 Porto Velho, RO, BrazilUAGRM, IRD, IIAP, LMI,EDIA, Montpellier, FranceINPA, Av Andre Araujo 2936, BR-69067375 Manaus, AM, BrazilUniv Fed Alagoas UFAL, Av Lourival Melo Mota,S-N Tabuleiro Martins, BR-57072900 Maceio, AL, BrazilUniv Fed Sao Paulo, Rua Doutor Carvalho Mendonca 144, BR-11070100 Santos, SP, BrazilUniv Fed Amazonas, Av Gen Rodrigo Octavio Jordao Ramos 3000, BR-69077000 Manaus, AM, BrazilIIAP, Vv Jose Quinones Km 2-5,Apartado Postal 784, Iquitos, PeruIRD, UMR BOREA, MNHN, CNRS 7208,SU,UCN,UA,IRD 207, Ave Agropolis 911, F-34394 Montpellier, FranceUMSS, ULRA, FAUNAGUA, ECOSINTEGRALES SRL, Ave Max Fernandez Final S-N, Cochabamba, BoliviaECOSINTEGRALES SRL, Res Act, Carlos Muller St 211, Cochabamba, Cercado, BoliviaInst Amazon Invest Cient SINCHI, Ave Vasquez Cobo Entre Calles 15 & 16, Bogota, ColombiaUniv Fed Sao Paulo, Rua Doutor Carvalho Mendonca 144, BR-11070100 Santos, SP, BrazilCAPES [1402376, 047/2012, 6632/14-9]CNPq [204344/2015-8][PAREV/FAPEAM 019/2010]FAPESP [2016/07910-0]Web of Scienc

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Enhanced Dechlorination of 1,2-Dichloroethane by Coupled Nano Iron-Dithionite Treatment

1,2-Dichloroethane (1,2-DCA) is a chlorinated solvent classified as a probable human carcinogen. Due to its extensive use in industrial applications, widespread contamination, and recalcitrance toward abiotic dechlorination, 1,2-DCA remains a challenging compound for the remediation community. Over the past decade, nano zerovalent iron (nZVI) has been efficiently used to treat many of the chlorinated compounds of concern. However, thus far, even nZVI (monometallic or bimetallic) has been unable to dechlorinate 1,2-DCA. Therefore, an alternative treatment coupling nZVI with dithionite to treat 1,2-DCA is proposed in this work. Coupled nZVI-dithionite was able to degrade >90% 1,2-DCA over the course of a year. The effects of dithionite and nZVI loadings, carboxymethyl cellulose (CMC) coating, addition of palladium, and other iron species as metal surfaces on the degradation kinetics were also investigated. Observed pseudo-first-order rate constants (<i>k</i>_<i>obs</i>) ranged from 3.8 × 10^–3 to 7.8 × 10^–3 d^–1. Both nucleophilic substitution and reductive dechlorination are the proposed mechanisms for 1,2-DCA degradation by coupled nZVI-dithionite treatment. Characterization analysis of the nZVI-dithionite nanoparticles shows that most of the iron was still preserved in the zerovalent state even after more than one year of reactivity with some iron sulfide (FeS) formation. Scanning electron microscopy (SEM) analysis shows that the nanosized spherical particles were still present along with the FeS platelets. This novel treatment represents the first nZVI-based formulation to achieve nearly complete degradation of 1,2-DCA

Subsurface Transport of Sulfidated Nano Zero Valent Iron and In Situ Biogeochemical Transformation of Chlorinated Solvents: A Field Study

In situ chemical reduction of chlorinated volatile organic compounds (cVOCs) by nano zero-valent iron (nZVI) has been widely applied in the past 20 years, but with limited effectiveness for bare nZVI due to rapid particle settling, short lifespan, and low reactivity. Stabilization and sulfidation of nZVI have improved its mobility and longevity, increased reactivity towards cVOCs, and reduced toxicity to microbes (Nunez Garcia et al. 2021).In the first-ever CMC-S-nZVI field trial, nZVI sulfidated by dithionite (S-nZVI) and stabilized by carboxymethyl cellulose (CMC) was injected into the subsurface of a site contaminated with a wide range of cVOCs. Multi-level wells were installed to monitor the transport of the CMC-S-nZVI suspension and its remedial performance for two years. Short-term (0-17 days) monitoring demonstrated a good transport of the suspension in the down- and up-gradient wells, in terms of total iron, boron, and sulfides which were major constituents of CMC-S-nZVI. Changes in concentrations of parent compounds, intermediates, and ethene showed effective dechlorination of high-chlorinated VOCs such as tetrachloroethene (PCE) and carbon tetrachloride (Nunez Garcia et al. 2020a, Nunez Garcia et al. 2020b). Long-term (157-729 days) performance was evaluated through temporal analyses of microbial communities, total iron, boron, and cVOCs in groundwater samples. Microbial populations, including organohalide-respiring bacteria, increased by >1 order of magnitude; with Geobacter being the most abundant. This long-term enrichment can be attributed to the low toxicity of CMC-S-nZVI and biostimulation by CMC and perhaps Fe3+. Non-metric multidimensional scaling analysis was carried out on microbial data grouped by depth range and proximity to the injection well. At locations that clearly received CMC-S-nZVI, there was a significant shift in microbial communities that was sustained for the long term.Iron concentrations increased substantially in long-term samples while boron concentrations decreased, suggesting that this iron did not come from CMC-S-nZVI. Microbial dissolution of iron minerals might have contributed to the increased iron content (Jones et al. 2006). Excess dithionite in CMC-S-nZVI would also have reductively dissolved native iron from the soil, as successfully demonstrated in the in situ redox manipulation (ISRM) technology wherein subsurface Fe3+ in soil was reduced to Fe2+ for long-term remedial purposes (Vermeul et al. 2000).Long-term changes in concentrations of lesser-chlorinated VOCs and hydrocarbons suggest that PCE was degraded via both the microbially-mediated sequential hydrogenolysis as well as the abiotic β-elimination. The intermediate vinyl chloride (VC) surprisingly did not accumulate in the current study, in contrast to the significant VC accumulation in a previous un-sulfidated CMC-nZVI trial at the same location (Kocur et al. 2016). Excess dithionite injected in this study might have avoided VC accumulation, as previously reported for ISRM treatment of a cVOCs-contaminated site (Vermeul et al. 2000). Additionally, the identified bacterial populations might have utilized sulfur species (from dithionite decomposition) and iron to form iron sulfides, which could dechlorinate cVOCs via in situ biogeochemical transformation (Kennedy et al. 2006).In summary, this study has demonstrated the long-term efficiency of CMC-S-nZVI for cVOCs removal through a combination of abiotic, biotic, and biostimulatory processes in the subsurface.

Sulfidation of Iron-Based Materials: A Review of Processes and Implications for Water Treatment and Remediation

Iron-based materials used in water treatment and groundwater remediationespecially micro- and nanosized zerovalent iron (nZVI)can be more effective when modified with lower-valent forms of sulfur (i.e., “sulfidated”). Controlled sulfidation for this purpose (using sulfide, dithionite, etc.) is the main topic of this review, but insights are derived by comparison with related and comparatively well-characterized processes such as corrosion of iron in sulfidic waters and abiotic natural attenuation by iron sulfide minerals. Material characterization shows that varying sulfidation protocols (e.g., concerted or sequential) and key operational variables (e.g., S/Fe ratio and sulfidation duration) result in materials with structures and morphologies ranging from core–shell to multiphase. A meta-analysis of available kinetic data for dechlorination under anoxic conditions, shows that sulfidation usually increases dechlorination rates, and simultaneously hydrogen production is suppressed. Therefore, sulfidation can greatly improve the efficiency of utilization of reducing equivalents for contaminant removal. This benefit is most likely due to inhibited corrosion as a result of sulfidation. Sulfidation may also favor desirable pathways of contaminant removal, such as (i) dechlorination by reductive elimination rather than hydrogenolysis and (ii) sequestration of metals as sulfides that could be resistant to reoxidation. Under oxic conditions, sulfidation is shown to enhance heterogeneous catalytic oxidation of contaminants. These net effects of sulfidation on contaminant removal by iron-based materials may substantially improve their practical utility for water treatment and remediation of contaminated groundwater

The International Linear Collider: Report to Snowmass 2021

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community