Provenance of Aerosol Black Carbon over Northeast Indian Ocean and South China Sea and Implications for Oceanic Black Carbon Cycling.

Aerosol black carbon (BC) is a short-lived climate pollutant. The poorly constrained provenance of tropical marine aerosol BC hinders the mechanistic understanding of extreme climate events and oceanic carbon cycling. Here, we collected PM2.5 samples during research cruise NORC2016-10 through South China Sea (SCS) and Northeast Indian Ocean (NEIO) and measured the dual-carbon isotope compositions (δ13C-Δ14C) of BC using hydrogen pyrolysis technique. Aerosol BC exhibits six different δ13C-Δ14C isotopic spaces (i.e., isotope provinces). Liquid fossil fuel combustion, from shipping emissions and adjacent land, is the predominant source of BC over isotope provinces "SCS close to Chinese Mainland" (53.5%), "Malacca Strait" (53.4%), and "Open NEIO" (40.7%). C3 biomass burning is the major contributor to BC over isotope provinces "NEIO close to Southeast Asia" (55.8%), "Open NEIO" (41.3%), and "Open SCS" (40.0%). Coal combustion and C4 biomass burning show higher contributions to BC over "Sunda Strait" and "Open SCS" than the others. Overall, NEIO near the Bay of Bengal, Malacca Strait, and north SCS are three hot spots of fossil fuel-derived BC; the first two areas are also hot spots of biomass-derived BC. The comparable δ13C-Δ14C between BC in aerosol and dissolved BC in surface seawater may suggest atmospheric BC deposition as a potential source of oceanic dissolved BC.

Assessment of trace metal contamination and ecological risk in the forest ecosystem of dexing mining area in northeast Jiangxi Province, China.

Samples of soil, earthworms, and tree roots from the forest ecosystem in the Dexing Pb/Zn mining area of Jiangxi Province were collected and the status of trace metal pollution analyzed to assess potential ecological risks. Chemometric and geographic information system methods were used to identify and describe the spatial distributions and the main contamination sources of trace metals. The order of potential ecological risks of trace metals in this area are as follows: cadmium (Cd) > arsenic (As) > copper (Cu) > nickel (Ni) > lead (Pb) > chromium (Cr) > zinc (Zn). Elemental spatial distribution maps showed the existence of zones heavily polluted by trace metals around the mining area. Earthworms and roots of three tree species were also heavily contaminated, with concentrations of trace metals in earthworms much higher than in previous studies. The potential ecological risk index and other soil quality indices indicated that soil had moderate to severe contamination and there were high ecological risks, with Cd making the greatest contribution. Multivariate statistical analyses showed that Cd, As, Cu, Pb, and Zn in soil came from a mining activity source, whereas Ni and Cr primarily originated from a natural source.

Persistent DNA methylation changes in zebrafish following graphene quantum dots exposure in surface chemistry-dependent manner.

Modified nano-graphene quantum dots (M-GQDs) are widely used in bioimaging, drug delivery, and chemical engineering. Because M-GQDs could induce reactive oxygen species and DNA damage, we hypothesized that M-GQDs modulate DNA methylation. To test this hypothesis, zebrafish were exposed to reduced, hydroxylated, or aminated GQDs (graphene quantum dots) at different concentrations for 7 days; global DNA methylation in liver, gill, and intestine was then studied. M-GQDs induced global DNA hypermethylation in various tissues in a dose-dependent manner. The global DNA methylation of reduced and aminated GQDs exposure showed a significant increase in intestines even at low concentrations (2 mg/L), suggesting that intestines are the main target for these two M-GQDs. The effects of global DNA methylation were evaluated 14 days after exposure had ceased. DNA methylation in the livers of exposure groups was significantly higher than in control zebrafish. Global DNA methylation increased in livers of zebrafish even after exposure to aminated GQDs (2 mg/L) had ceased, indicating a more complex mechanism of DNA methylation deregulation. The present results showed that chemical groups in the surface of GQDs are a critical factor for modulating DNA methylation.

Trace metal pollution and ecological risk assessment in agricultural soil in Dexing Pb/Zn mining area, China.

Surface agricultural soil samples obtained from Dexing Pb/Zn mining area in Jiangxi province were analyzed for trace metals to assess their pollution status and potential ecological risk. The spatial distributions and the major trace metals pollution sources were described and identified with the combination of chemical measures and geographic information systems technology. The level of pollution in seven metals is decreasing in the following order: zinc (Zn 128.9 mg/kg) > chromium (Cr 64.1 mg/kg) > lead (Pb 58.4 mg/kg) > arsenic (As 45.3 mg/kg) > copper (Cu 41.9 mg/kg) > nickel (Ni 31.3 mg/kg) > cadmium (Cd 1.5 mg/kg). Trace metal spatial distribution maps established by geographic information system techniques displayed two high-pollution zones around mining sites in the study area. Multivariate statistical analyses were also applied, and the results demonstrated that Cd, As, Pb, Cu and Zn in the soils originated from mining activities, whereas Cr and Ni primarily originated from natural sources. The values of pollution index ranged from 4.79 to 71.59, and the values of modified pollution index ranged from 1.98 to 24.69. Moreover, the potential ecological risk values ranged from 264.0 to 3263.5, which indicated considerable ecological risk to very high ecological risk. The potential ecological risk values and other soil contamination indices showed similar patterns that the high-risk areas were around Dexing Pb/Zn mining site. The surface agricultural soil in study area is heavily to extremely polluted , with Cd that made the most dominant contribution.