Oxalate
and sulfate are ubiquitous components of ambient aerosols
with a high complexation affinity to iron. However, their effect on
iron-driven secondary brown carbon formation in solution from soluble
aromatic and aliphatic reagents was not studied. We report masses
and hydrodynamic particle sizes of insoluble particles formed from
the dark aqueous phase reaction of catechol, guaiacol, fumaric, and
muconic acids with Fe(III) in the presence of oxalate or sulfate.
Results show that oxalate decreases particle yield in solution from
the reaction of Fe(III), with a stronger effect for guaiacol than
catechol. For both compounds, the addition of sulfate results in the
formation of more polydisperse (0.1–5 μm) and heavier
particles than those from control experiments. Reactions with fumaric
and muconic acids show that oxalate (not sulfate) and pH are determining
factors in the efficiency of particle formation in solution. Polymerization
reactions occur readily in the presence of sulfate in solution producing
particles with iron-coordinated and/or pore-trapped sulfate anions.
The addition of oxalate to the reactions of Fe(III) with all organics,
except guaiacol, produced fewer and larger polymeric particles (>0.5
μm). These results imply that even in the presence of competing
ligands, the formation of insoluble and colored particles from soluble
organic precursors still dominates over the formation of soluble iron
complexes.
The present study was undertaken to determine the content of six minerals, five trace elements, and ten pesticide residues in honeys originating from different regions of Malaysia. Calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn) were analyzed by flame atomic absorption spectrometry (FAAS), while sodium (Na) and potassium (K) were analyzed by flame emission spectrometry (FAES). Trace elements such as arsenic (As), lead (Pb), cadmium (Cd), copper (Cu), and cobalt (Co) were analyzed by graphite furnace atomic absorption spectrometry (GFAAS) following the microwave digestion of honey. High mineral contents were observed in the investigated honeys with K, Na, Ca, and Fe being the most abundant elements (mean concentrations of 1349.34, 236.80, 183.67, and 162.31 mg/kg, resp.). The concentrations of the trace elements were within the recommended limits, indicating that the honeys were of good quality. Principal component analysis reveals good discrimination between the different honey samples. The pesticide analysis for the presence of organophosphorus and carbamates was performed by high performance liquid chromatography (HPLC). No pesticide residues were detected in any of the investigated honey samples, indicating that the honeys were pure. Our study reveals that Malaysian honeys are rich sources of minerals with trace elements present within permissible limits and that they are free from pesticide contamination.
In situ molecular-level infrared spectroscopic analysis coupled with surface complexation modeling of organics at the aqueous solution–hematite nanoparticle interface.
Hygroscopic properties and chemical
reactivity of secondary organic
aerosols (SOA) influence their overall contribution to the indirect
effect on the climate. In this study, we investigate the hygroscopic
properties of organic and organometallic polymeric particles, namely
polycatechol, polyguaiacol, Fe-polyfumarte, and Fe-polymuconate. These
particles efficiently form in iron-catalyzed reactions with aromatic
and aliphatic dicarboxylic acid compounds detected in field-collected
SOA. The structure of surface water was studied using diffuse reflectance
infrared Fourier transform spectroscopy (DRIFTS), and the uptake of
gas water was quantified using quartz crystal microbalance (QCM) as
a function of relative humidity. Spectroscopic data show that water
bonding with organic functional groups acting as hydrogen bond acceptors
causes shifts in their vibrational modes. Analysis of the hydroxyl
group stretching region revealed weak and strong hydrogen bonding
networks that suggest cluster formation reflecting water–water
and water–organics interactions, respectively. A modified Type
II multilayer Brunauer–Emmett–Teller adsorption model
described the adsorption isotherm on the nonporous materials, polycatechol,
polyguaiacol, and Fe-polymuconate. However, water adsorption on porous
Fe-polyfumarate was best described using a Type V adsorption model,
namely the Langmuir–Sips model that accounts for condensation
in pores. The data revealed that organometallic polymers are more
hygroscopic than organic polymers. The implications of these investigations
are discussed in the context of the chemical reactivity of these particles
relative to known SOA.
Since the outburst of Covid-19 in China, the world economy is passing in a turmoil situation. Undeniably the economy of Bangladesh is also grappled by the severe public health crisis of the Covid-19. As the public health emergency is heavily interconnected with economic affairs, it has impacted each of the pillars of the economy of Bangladesh. The main purpose of this paper is to make evaluations of the potential impact of the COVID-19 pandemic on the economy of Bangladesh. This study is based on an empirical review of the recent study works, reports, working papers of home, and abroad regarding economic crisis. The review findings of the paper revealed that the COVID-19 pandemic have significant impacts on the different indicators of the economy of Bangladesh especially, Readymade Garments Sector, Foreign Remittance, Bank and Financial Institutions, Food and Agricultures, Local Trade, Foreign Trade (Export and Import), GDP (Gross Domestic Product), SDGs (Sustainable Development Goal), Government Revenue and Employment etc. This study suggested that as Covid-19 still surfacing all over the world so some steps should be ensured by the government agencies of Bangladesh to mitigate possible threats for the economy.
In the present study, the residual pesticide levels were determined in eggplants (Solanum melongena) (n = 16), purchased from four different markets in Dhaka, Bangladesh. The carbamate and organophosphorus pesticide residual levels were determined by high performance liquid chromatography (HPLC), and the efficiency of gamma radiation on pesticide removal in three different types of vegetables was also studied. Many (50%) of the samples contained pesticides, and three samples had residual levels above the maximum residue levels determined by the World Health Organisation. Three carbamates (carbaryl, carbofuran, and pirimicarb) and six organophosphates (phenthoate, diazinon, parathion, dimethoate, phosphamidon, and pirimiphos-methyl) were detected in eggplant samples; the highest carbofuran level detected was 1.86 mg/kg, while phenthoate was detected at 0.311 mg/kg. Gamma radiation decreased pesticide levels proportionately with increasing radiation doses. Diazinon, chlorpyrifos, and phosphamidon were reduced by 40–48%, 35–43%, and 30–45%, respectively, when a radiation strength of 0.5 kGy was utilized. However, when the radiation dose was increased to 1.0 kGy, the levels of the pesticides were reduced to 85–90%, 80–91%, and 90–95%, respectively. In summary, our study revealed that pesticide residues are present at high amounts in vegetable samples and that gamma radiation at 1.0 kGy can remove 80–95% of some pesticides.
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