Sherri A. Mason

Eleven globally sourced brands of bottled water, purchased in 19 locations in nine different countries, were tested for microplastic contamination using Nile Red tagging. Of the 259 total bottles processed, 93% showed some sign of microplastic contamination. After accounting for possible background (lab) contamination, an average of 10.4 microplastic particles >100 um in size per liter of bottled water processed were found. Fragments were the most common morphology (66%) followed by fibers. Half of these particles were confirmed to be polymeric in nature using FTIR spectroscopy with polypropylene being the most common polymer type (54%), which matches a common plastic used for the manufacture of bottle caps. A small fraction of particles (4%) showed the presence of industrial lubricants. While spectroscopic analysis of particles smaller than 100 um was not possible, the adsorption of the Nile Red dye indicates that these particles are most probably plastic. Including these smaller particles (6.5–100 um), an average of 325 microplastic particles per liter of bottled water was found. Microplastic contamination range of 0 to over 10,000 microplastic particles per liter with 95% of particles being between 6.5 and 100 um in size. Data suggests the contamination is at least partially coming from the packaging and/or the bottling process itself. Given the prevalence of the consumption of bottled water across the globe, the results of this study support the need for further studies on the impacts of micro- and nano- plastics on human health.

Microplastics (MPs; p value <0.05). The sediments with the highest numbers of MPs were from sites in the vicinity of highly populated centers and municipal effluent discharges. FTIR analysis showed that polyethylene (PE), nylon, and polyethylene terephthalate (PET) were the most abundant polymer types. More than half of the observed MPs (56%) were in the size category of 1–4.7 mm length, with the remaining particles (44%) being in the size range of 10 μm to <1 mm. Compared to literature data from other regions, intertidal sediments in the Persian Gulf cannot be characterized as a hot spot for MP pollution. The present study could, however, provide useful background information for further investigations and management policies to understand the sources, transport, and potential effects on marine life in the Persian Gulf.

Rate constants for the gas-phase reactions of the OH radical with 1,4-butanediol, 4-hydroxybutanal, and 3-hydroxypropanal were measured at 298 ± 2 K and atmospheric pressure using a relative rate technique and with 4-hydroxybutanal and 3-hydroxypropanal being formed in situ from the OH + 1,4-butanediol reaction, and were (in units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹) 3.67 ± 0.31, 3.0_−1.0^+1.5, and 3.5_−1.0^+1.3, respectively, with the latter being a lower limit because of the possibility of second-generation formation of 3-hydroxypropanal from OH + 4-hydroxybutanal. The measured formation yields of 4-hydroxybutanal and 3-hydroxypropanal from the OH + 1,4-butanediol reaction in the presence of NO were 58 ± 19% and 55 ± 12%, respectively. In addition to the formation of 4-hydroxybutanal and 3-hydroxypropanal, gas chromatography−mass spectrometric analyses of reacted OH + 1,4-butanediol reactions showed formation of glycolaldehyde [HOCH₂CHO], malonaldehyde [HC(O)CH₂CHO], and 1,4-butanedial [HC(O)CH₂CH₂CHO]. Glycolaldehyde, malonaldehyde, and 1,4-butanedial are expected products of the reaction of OH radicals with 4-hydroxybutanal, and glycolaldehyde and malonaldehyde are expected products of the reaction of OH radicals with 3-hydroxypropanal. Reaction mechanisms are presented and discussed.

Rate constants for the gas-phase reactions of NO₃ radicals and O₃ with a series of C₆−C₁₄ 1-alkenes and 2-methyl-1-alkenes have been measured at 296 ± 2 K and atmospheric pressure of air using relative rate methods. For the NO₃ radical reactions, the rate constants obtained (in units of 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹) were: 1-hexene, 2.00 ± 0.16; 1-octene, 2.35 ± 0.15; 1-decene, 2.55 ± 0.16; 1-dodecene, 2.79 ± 0.36; 1-tetradecene, 2.87 ± 0.21; 2-methyl-1-pentene, 43.8 ± 2.3; 2-methyl-1-hexene, 52.4 ± 2.5; 2-methyl-1-octene, 57.8 ± 2.6; 2-methyl-1-nonene, 60.8 ± 2.9; 2-methyl-1-undecene, 60.8 ± 3.3; 2-methyl-1-tridecene, 60.3 ± 3.4; and cycloheptene, 49.4 ± 2.0. For the O₃ reactions, the rate constants obtained (in units of 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹) were: 1-hexene, 0.898 ± 0.054; 1-heptene, 1.05 ± 0.07; 1-octene, 1.01 ± 0.04; 1-decene, 1.11 ± 0.05; 1-dodecene, 1.38 ± 0.14; 1-tridecene, 1.92 ± 0.12; 1-tetradecene, 2.44 ± 0.24; 2-methyl-1-pentene, 1.26 ± 0.13; 2-methyl-1-heptene, 1.35 ± 0.05; 2-methyl-1-octene, 1.38 ± 0.06; 2-methyl-1-decene, 1.48 ± 0.07; 2-methyl-1-undecene, 1.46 ± 0.11; and 2-methyl-1-tridecene, 2.85 ± 0.42. The rate constants for the NO₃ radical reactions significantly increase with increasing carbon number, attaining a plateau at ≥C₁₄ for the 1-alkenes and at C₁₀−C₁₄ for the 2-methyl-1-alkenes. In contrast, the rate constants for O₃ reactions increase only slightly with increasing carbon number up to ∼C₁₀ for the 1-alkenes and ∼C₁₂ for the 2-methyl-1-alkenes, with the significant increase in the measured rate constants for the >C₁₀ 1-alkenes and >C₁₂ 2-methyl-1-alkenes possibly being due to heterogeneous reactions. Reasons for the observed trends in NO₃ radical and O₃ reaction rate constants with alkene carbon number are discussed.