Mercury isotopic compositions in fine particles and offshore surface seawater in a coastal area of East China: implications for Hg sources and atmospheric transformations

Abstract

Abstract. Isotopic compositions of Mercury (Hg) in atmospheric particles (HgPM) are probably the mixed results of emission sources and atmospheric processes. Here, we present Hg isotopic compositions in daily fine particles (PM2.5) collected from an industrial site (Chunxiao – CX) and a nearby mountain site (Daimeishan – DMS) in a coastal area of East China, and in surface seawater close to the industrial area, to reveal the influence of anthropogenic emission sources and atmospheric transformations on Hg isotopes. The PM2.5 samples displayed a significant spatial difference in δ202Hg. For the CX site, the negative δ202Hg values are similar to those of source materials, and the HgPM contents were well correlated with chemical tracers, indicating the dominant contributions of local industrial activities to HgPM2.5, whereas the observed positive δ202Hg at the DMS site was likely associated with regional emissions and extended atmospheric processes during transport. The Δ199Hg values in PM2.5 from the CX and DMS sites were comparably positive. The unity slope of Δ199Hg versus Δ201Hg over all data suggests that the odd mass independent fractionation (MIF) of HgPM2.5 was primarily induced by the photoreduction of Hg2+ in aerosols. The positive Δ200Hg values with a minor spatial difference were probably associated with the photooxidation of Hg0, which is generally enhanced in the coastal environment. Total Hg in offshore surface seawater was characterized by negative δ202Hg and near-zero Δ199Hg and Δ200Hg values, which are indistinguishable from Hg isotopes of source materials. Overall, the PM2.5 collected from industrial areas had comparable δ202Hg values but more positive Δ199Hg and Δ200Hg as compared to surface seawater. The results indicate that atmospheric transformations would induce the significant fractionation of Hg isotopes and obscure the Hg isotopic signatures of anthropogenic emissions.

Stable Isotopes Reveal Photoreduction of Particle-Bound Mercury Driven by Water-Soluble Organic Carbon during Severe Haze

“…Most physical and chemical processes lead to MDF, but odd-MIF is mainly produced by photochemical reactions (e.g. photoreduction of aqueous Hg­(II), photodemethylation of methylmercury). − Even-MIF is mainly observed in atmospheric samples, and its mechanism may be attributed to atmospheric redox processes. − Previous studies have reported Hg isotopes of PBM in different regions (e.g., urban, rural, and coastal areas) ,− and seasonal even diurnal variation of odd-MIF ,, and indicate that the isotopic compositions of PBM emitted from primary sources would be modified during atmospheric transformation or transportation. However, the mechanism that drives Hg isotope variations of PBM is still poorly understood, especially during the transformations of PBM in severe haze events.…”

Atmospheric Mercury Isotope Shifts in Response to Mercury Emissions from Underground Coal Fires

“…By comparison, PBM samples collected at background sites (e.g., forested mountains and coastal/offshore sites) with low Hg levels commonly had distinctly positive Δ 199 Hg (0.15−0.66‰) values. 54,55,67,71,72,79 The isotope compositions of our TGM samples from the urban Wuda district partly overlapped those measured at urban/industrial sites of large cities in China and other countries (Figure 2). Specifically, our winter TGM samples with low Hg concentrations (1.32 ± 0.85 ng m −3 ) exhibited rather stable and small negative δ 202 Hg values (−0.65 ± 0.37‰), which are very similar to those of large Chinese cities such as Guiyang (−0.62 ± 0.25‰), Shijiazhuang (−0.56 ± 0.44‰), Jinan (−0.58 ± 0.43‰), Chengdu (−0.68 ± 0.44‰), and Wuhan (−0.70 ± 0.23‰).…”

“…Atmospheric samples, including TGM (typically used to represent GEM) ,− ,− and PBM of different particulate sizes (TSP, PM 10 , and PM 2.5 ), − ,,,,− that were collected from diverse regions (urban/industrial, rural/background, and coastal/offshore sites) have been reported for Hg isotope compositions. TGM samples collected at inland background sites (e.g., forested mountains) far from the urban/industrial centers and tectonically active regions (e.g., volcanos and faults) are commonly characterized by positive δ 202 Hg (−0.16 to 1.19‰, site-specific mean values) and slightly negative Δ 199 Hg (−0.28 to −0.05‰) and Δ 200 Hg (−0.11 to −0.02‰) values (Figure ).…”

“…TGM samples collected at inland background sites (e.g., forested mountains) far from the urban/industrial centers and tectonically active regions (e.g., volcanos and faults) are commonly characterized by positive δ 202 Hg (−0.16 to 1.19‰, site-specific mean values) and slightly negative Δ 199 Hg (−0.28 to −0.05‰) and Δ 200 Hg (−0.11 to −0.02‰) values (Figure ). ,− In contrast, TGM samples collected at urban/industrial sites and areas affected by direct anthropogenic Hg emissions typically have negative δ 202 Hg (−0.96‰ to −0.08‰, site-specific mean values) and near-zero Δ 199 Hg (−0.15‰ to 0.06‰) and Δ 200 Hg (−0.03‰ to 0.02‰) values. ,,,,, The PBM samples were mostly measured at urban/industrial sites that had high Hg levels, ,− which were generally characterized by very negative δ 202 Hg (−2.60‰ to −0.53‰, site-specific mean values) and variable Δ 199 Hg (−0.31‰ to 0.47‰) and slightly positive Δ 200 Hg (0.01–0.11‰) values (Figure ). By comparison, PBM samples collected at background sites (e.g., forested mountains and coastal/offshore sites) with low Hg levels commonly had distinctly positive Δ 199 Hg (0.15–0.66‰) values. ,,,,, …”

Sampling and determination of antimony isotopes in airborne particles: an assessment of membrane filter materials

“…It has also been proven to be ideal for PM 2.5 sampling. 30,[47][48][49] In comparison, namely, PTFE lter is characterized by high blank value and hard to be digested, and PC, MCE, CA lters are not suitable for PM 2.5 sampling owing to their high-ow resistance and compactness (pore size of 0.45 mm). Therefore, the QM membrane lter was the best medium for collecting Sb from airborne particulate matter.…”