Traditional and novel organophosphate esters (OPEs) in PM2.5 of a megacity, southern China: Spatioseasonal variations, sources, and influencing factors.

Organophosphate esters (OPEs) are ubiquitous contaminants in the environment, whereas their atmospheric processes and fate are poorly understood. The present study revealed the spatial heterogeneity and seasonal variations of traditional and novel OPEs in PM2.5 (particulate matter with diameters < 2.5 µm) across a megacity (including residential areas and potential source sites) in South China. Potential influencing factors on the contamination levels of OPEs were addressed. The total concentrations of 11 traditional OPEs ranging from 262 to 42,194 pg/m3 (median = 1872 pg/m3) were substantially higher than those of 10 novel OPEs (33.5-3835 pg/m3, median = 318 pg/m3). Significant spatial and temporal variations in the concentrations of most OPEs were observed. The overall district-specific contamination levels in this city showed dependence on the secondary industry sector for non-predominant OPEs and on the tertiary industry for predominant OPEs. The seasonal variations of the OPE concentrations suggest difference in their sources or influence of meteorological conditions. The correlations between the individual OPEs in PM2.5 are determined largely by either their applications or physicochemical properties (in particular vapor pressure). The correlations between OPE concentrations and each meteorological factor (temperature, relative humidity, wind speed, and surface solar radiation) were inconsistent (positive and negative). Wind speed had the greatest effect on the OPE levels; While most OPEs bound to PM2.5 were not efficiently scavenged by below-cloud rainfall. The results suggest that atmospheric half-life and Henry's Law Constant of OPEs are also determining factors for the wind speed and rainfall influence, respectively. However, mechanisms underlying the influence of meteorological conditions on atmospheric OPEs still need further research.

Legacy and emerging organophosphorus flame retardants and plasticizers in frogs: Sex difference and parental transfer.

Black-spotted frogs and bullfrogs from an e-waste polluted area were collected and examined for legacy and emerging organophosphorus flame retardants (PFRs) and plasticizers. Total concentrations of PFRs and plasticizers were 0.62-15 ng/g wet weight (ww) and 316-4904 ng/g ww in muscles, 2.2-59 ng/g ww and 127-5757 ng/g ww in eggs and gonads, and 1.2-15 ng/g ww and 51-1510 ng/g ww in oviducts, respectively. For muscle tissues, concentrations of ∑PFRs, triethyl phosphate, tris-(2-chloroethyl) phosphate, and tris-(chloro-2-propyl) phosphate were significantly higher in the males than females (p < 0.05). However, for reproductive tissues, eggs exhibited higher levels of those contaminants than gonads (p < 0.05). No significant sex difference in levels of plasticizers was observed in muscles. In contrast, levels for (2-ethylhexyl) phthalate, di-n-butyl phthalate, and di-iso-butyl phthalate in gonads were significantly higher than those in eggs (p < 0.05). Significantly negative linear correlations between maternal transfer ratios and log KOW were found in female frogs. Paternal transfer potentials were first significantly and positively correlated to log KOW (<6) and then decreased afterward in the males. These results indicated that parental transfer was answer for the sex-specific accumulation of PFRs and plasticizers in frogs.

Dechlorination of p,p'-DDTs coupled with sulfate reduction by novel sulfate-reducing bacterium Clostridium sp. BXM.

A novel non-dsrAB (without dissimilatory sulfite reductase genes) sulfate-reducing bacterium (SRB) Clostridium sp. BXM was isolated from a paddy soil. Incubation experiments were then performed to investigate the formation of reduced sulfur compounds (RSC) by Clostridium sp. BXM, and RSC-induced dechlorination of p,p'-DDT in culture medium and soil solution. The RSCs produced were 5.8 mM and 4.5 mM in 28 mM sulfate amended medium and soil solution respectively after 28-day cultivation. The p,p'-DDT dechlorination ratios were 74% and 45.8% for 5.8mM and 4.5 mM RSCs respectively at 6h. The metabolites of p,p'-DDT found in the two reaction systems were identified as p,p'-DDD and p,p'-DDE. The dechlorination pathways of p,p'-DDT to p,p'-DDD and p,p'-DDE were proposed, based on mass balance and dechlorination time-courses. The results indicated that RSC-induced natural dechlorination may play an important role in the fate of organochlorines.