3 research outputs found
Probing and Comparing the Photobromination and Photoiodination of Dissolved Organic Matter by Using Ultra-High-Resolution Mass Spectrometry
Photochemical
halogenation of dissolved organic matter (DOM) may
represent an important abiotic process for the formation of natural
organobromine compounds (OBCs) and natural organoiodine compounds
(OICs) within surface waters. Here we report the enhanced formation
of OBCs and OICs by photohalogenating DOM in freshwater and seawater,
as well as the noticeable difference in the distribution and composition
pattern of newly formed OBCs and OICs. By using negative ion electrospray
ionization coupled with Fourier transform ion cyclotron resonance
mass spectrometry, various OBCs and OICs were identified during the
photohalogenation processes in sunlit waters. The respective number
of OBCs and OICs formed in artificial seawater (ASW) under light radiation
was higher than that in artificial freshwater (AFW), suggesting a
possible role of the mixed reactive halogen species. OBCs were formed
mainly via substitution reactions and addition reactions accompanied
by other reactions and distributed into three classes: unsaturated
hydrocarbons with relatively low oxygen content, unsaturated aliphatic
compounds, and saturated fatty acids and carbohydrates with relatively
high hydrogen content. Unlike the OBCs, OICs were located primarily
in the region of carboxylic-rich alicyclic molecules composed of esterified
phenolic, carboxylated, and fused alicyclic structures and were generated
mainly through electrophilic substitution of the aromatic proton.
Our findings call for further investigation on the exact structure
and toxicity of the OBCs and OICs generated in the natural environment
Aluminum Dialkyl Phosphinate Flame Retardants and Their Hydrolysates: Analytical Method and Occurrence in Soil and Sediment Samples from a Manufacturing Site
Aluminum dialkyl
phosphinates (ADPs) are emerging phosphorus flame
retardants due to their superior characteristics, but their analytical
method, and occurrence and fate in environments have never been reported.
For the first time, we developed a method for the analysis of trace
ADPs and their hydrolysates (dialkyl phosphinic acids, DPAs), and
studied their occurrences and fates in soils and sediments. We found
that ADPs are hardly dissolved in water and organic solvents, but
are dissolved and hydrolyzed to DPAs in 30 mM NH<sub>3</sub>·H<sub>2</sub>O, thus both ADPs and DPAs can be determined by liquid chromatography-electrospray
ionization-tandem mass spectrometry (LC-ESI-MS/MS) in the form of
DPAs. ADPs and DPAs in soil and sediment samples were determined by
(i) extracting both ADPs and DPAs with 75 mM NH<sub>3</sub>·H<sub>2</sub>O, and selectively extract DPAs only with formic acid–water–methanol
(5:5:90, v/v/v); (ii) quantifying the total content of ADPs and DPAs,
and DPAs by LC-MS/MS analysis of the DPA contents in the former and
the latter extract, respectively; and (iii) calculating ADPs from
the content difference between the former and the latter extracts.
The limit of quantifications (LOQs) of the proposed method were 0.9–1.0
μg/kg, and the mean recoveries ranged from 69.0% to 112.4% with
relative standard deviations ≤21% (<i>n</i> = 6).
In soil and sediment samples around a manufacturing plant, ADPs and
DPAs were detected in surface soils in the ranges of 3.9–1279.3
and 1.0–448.6 μg/kg, respectively. While ADPs were found
in all the samples of the soil and sediment cores from the drain outlet
and the waste residue treatment site at levels ranging from 30.8 to
4628.0 μg/kg, DPAs were found in more than 90% of these samples
with concentrations in the range of 1.1–374.6 μg/kg.
The occurrences of ADPs and DPAs are not in correlation with the total
organic carbon, whereas the occurrences of DPAs are highly correlated
with the sample pH. Our study also suggests that the DPAs in the samples
sourced from the hydrolysis of ADPs. The high hydrolysis degrees of
ADPs (up to 49.6%) suggest that once released into the environment,
ADPs are likely to coexist with their hydrolysates. Thus, to evaluate
the environmental safety of ADPs, the environmental behavior and toxicity
of both ADPs and DPAs should be considered
Swelling-Induced Fragmentation and Polymer Leakage of Nanoplastics in Seawater
Nanoplastics (NPs) have been successively detected in
different
environmental matrixes and have aroused great concern worldwide. However,
the fate of NPs in real environments such as seawater remains unclear,
impeding their environmental risk assessment. Herein, multiple techniques
were employed to monitor the particle number concentration, size,
and morphology evolution of polystyrene NPs in seawater under simulated
sunlight over a time course of 29 days. Aggregation was found to be
a continuous process that occurred constantly and was markedly promoted
by light irradiation. Moreover, the occurrence of NP swelling, fragmentation,
and polymer leaching was evidenced by both transmission electron microscopy
and scanning electron microscopy techniques. The statistical results
of different transformation types suggested that swelling induces
fragmentation and polymer leakage and that light irradiation plays
a positive but not decisive role in this transformation. The observation
of fragmentation and polymer leakage of poly(methyl methacrylate)
and poly(vinyl chloride) NPs suggests that these transformation processes
are general for NPs of different polymer types. Facilitated by the
increase of surface functional groups, the ions in seawater could
penetrate into NPs and then stretch the polymer structure, leading
to the swelling phenomenon and other transformations