In order to evaluate the effectiveness of the Minamata Convention on mercury, understanding the air–surface mercury exchange in grasslands is important as they cover 20%–40% of the Earth's land surface. An in-depth quantitative understanding of the processes of the mercury cycle, such as dry and wet depositions, evasion from soil, plant uptake, and natural and prescribed biomass burning, is essential to explore the mercury cycle in these regions; however, only a limited number of studies are available on these processes, and many questions regarding them still remain. In this mini-review, the key emission and sinking processes occurring in natural and semi-natural grasslands and the potential of stable mercury isotope measurements for tracing studies of mercury origin(s) in grasslands are discussed.

Quantitative estimation of particulate matter (PM) pollution from coal combustion, which is one of the major anthropogenic emission sources in China, is urgently needed to better understand transboundary pollution in the East Asian region. As a first step, we conducted laboratory experiments for the mass spectrometric characterization of fly ash from coal combustion using a fluidized bed reactor. Here, we report detection of notable signals at m/z 85, 87, and 133 in mass spectra for organic species obtained by an Aerodyne quadrupole aerosol mass spectrometer (AMS). Nine different coals, six of which were mined in north-east Asian region, were tested with three different combustion temperatures. The results showed that signals at m/z 85, 87, and 133 were significantly larger than those at the adjacent m/z, with similar observations having been made in different field studies carried out in western Japan. The m/z 85 to m/z 87 ratios were reproducible over the coals tested, suggesting the potential usefulness of these for fingerprinting coal combustion PM. The average ratio with the standard error of the mean was 2.8 ± 0.1. While the m/z 133 to m/z 87 ratios varied more, the mean ratio with the standard error of the mean was 1.5 ± 0.2, and the results were still reproducible. A comparison of the m/z 85 and 133 to m/z 87 ratios from other studies that also used AMS suggests that the ratios obtained in the current work are distinctive from those for vehicular emissions, plastic burning, and cooking emissions, but close to those for biomass burning. Despite this similarity, the results here still offer useful information for source identification of PM with the use of AMS measurements.

Atmospheric pollutants exist in both gaseous and particulate form and they have significant impacts on human health, air quality, and the climate [...]

In every Spring, prescribed grassland burning, so-called Noyaki in Japanese, has been conducted for over a 1000 years by local residents in the Aso region, Japan, for the purpose of grassland conservation because Noyaki prevents invasion of woody plants in the grassland and helps the growth of grasses, which were an important resource of primary industry for roofing materials of houses and livestock feed. Meanwhile, biomass burning is known to be one of the most significant sources of airborne substances including mercury. Taking advantage of the characteristics and resources of the place we live in, we here describe our on-going study for the emission of gaseous mercury from the traditional Noyaki in the Aso region and other grasslands of western Japan. During Noyaki, we sampled and measured gaseous mercury from the Noyaki plumes to better understand mercury emissions and cycles in the local environment. Results showed, on average, 3.8 times higher atmospheric mercury concentrations, demonstrating the emission of gaseous mercury from the Noyaki. The possible origins, novel information the results inferred, and future research direction are discussed in this chapter.

In order to understand transported and local pollution in an urban area that are strongly affected by long-range transport of air pollution, daily concentrations of 15 polycyclic aromatic hydrocarbons (PAHs) and 20 n-alkanes in the total suspended particles were simultaneously measured at sites in Western Japan on Fukue Island (FI), located downwind of mainland East Asia, and Fukuoka City (FC), a megacity close (< 200 km) to the FI site, in spring and winter 2010 and summer 2011. The average total PAH concentration observed at the FC site (2.93 ± 2.17 ng/m3) was higher than that at the FI site (1.78 ± 1.70 ng/m3). The average total n-alkane concentration at the FC site (34.7 ± 21.8 ng/m3) was also higher than that at the FI site (12.2 ± 9.2 ng/m3). However, the total PAH and n-alkane concentrations measured at the FI site were considerably high, despite its remote location. The seasonal changes in the specific PAH ratios, used to determine the source of pollutants, were similar between the FC and FI sites. The average fluoranthene/(fluoranthene + pyrene) ratio was 0.57–0.65 in winter and spring and 0.48–0.51 in summer. PAHs observed at both sites mainly originated from coal or biomass combustion in spring or winter, whereas those were affected by petroleum combustion as well as coal and biomass combustion in summer. These field results show that pollutants transported from mainland East Asia make a significant contribution to the total PAHs and n-alkanes at the FC site in the winter and spring seasons.

Aerosol chemical species were measured using an Aerodyne quadrupole aerosol mass spectrometer (Q-AMS) in spring 2010, in Fukuoka. The main species were sulfate and organics. Organic data were analyzed using the Positive Matrix Factorization (PMF) method. Two distinct periods (Period 1 and 2) were selected. Period 1 (from March 19 at 19: 50 to March 20 at 10: 00) was influenced by trans-boundary air pollution. Low-volatile, oxygenated organic aerosols (LV-OOA) were dominant and the hydrocarbon-like organic aerosols (HOA) fraction was as low as 15%. About one-fourth (26%) of the observation period in Fukuoka was influenced by trans-boundary air pollution. In Period 2 (from March 22 at 00: 00 to March 22 at 23: 50), both local emissions and trans-boundary air pollutants influenced Fukuoka air quality. The HOA fraction was relatively high, although the LV-OOA fraction was about one-third of OA. The trans-boundary air pollution was analyzed using the oxidation state of organic aerosols (OA), obtained by the PMF method.

Biomass burning is one of the largest sources of particulate matter emissions globally. However, the emission of particulate inorganic species from prescribed grassland burning in Japan has not yet been characterized. In this study, we collected total suspended particulate matter from prescribed grassland burning in Hirado, Akiyoshidai, and Aso, Japan. The collected filter samples were brought to the laboratory, and water-soluble inorganic components were analyzed via ion chromatography. The measurement results showed high excess concentrations of potassium, calcium, and magnesium, and these substances were highly correlated, which agreed with previously reported findings. In contrast, the concentrations of sodium, chloride, nitrate, and sulfate were insignificant, even though their high concentrations were reported in other biomass burning studies. Among these low concentration substances, a high correlation was still observed between sulfate and nitrate. It is possible that the low concentrations of those species could have been biased in the measurements, particularly as a result of subtracting blank and background values from the observed concentrations. Building up more data in this area may allow us to characterize the significance of domestic biomass burning’s contribution to inorganic particulate components in Japanese air, which may consequently contributes to better understanding of adverse health effect of airborne particulate matter.

Biomass burning is one of the major emitters of airborne particulate matter (PM) and gaseous mercury. In order to apply the isotopic fingerprinting method to process identification and source apportionment studies, isotopic characterizations of targeted substances at emission are indispensable. Here, we report the stable isotopic composition of total gaseous mercury (TGM) and the stable and radiocarbon isotopic composition of low-volatile water-soluble nitrogen (LV-WSN) and organic carbon (LV-WSOC) in PM emitted from open grass field burning in the Aso region of Japan. The measurement results showed that TGM concentrations in the air increased during the open field burning events, indicating the presence of TGM emissions. The results of LV-WSN analysis showed very low concentrations; therefore, the stable nitrogen isotope ratios could not be measured. The stable mercury isotope ratios exhibited lighter composition than those observed during non-biomass-burning days. The analysis of LV-WSOC revealed heavy stable carbon isotope ratios (average ± SD, −18 ± 2‰), suggesting a substantial contribution from C4 plant carbon. The 14C analysis showed that more than 98% of the LV-WSOC was modern carbon, indicating the contribution of plant carbon to PM emitted from biomass burning. The findings here provide reference isotope compositions of TGM and particulate LV-WSOC from biomass burning in this region.

Five stable isotope ratios of mercury (199Hg/198Hg, 200Hg/198Hg, 201Hg/198Hg, 202Hg/198Hg, and 204Hg/198Hg) in commercially available thermometers and fluorescent tubes were analyzed to characterize their potential anthropogenic emission source to landfills, manufacturing factories, and our daily lives. The results for the liquid metal mercury yielded from the thermometers showed similar mass-independent fractionation values to those in the literature. The analysis of fluorescent tubes resulted in that more than 96% of mercury in the fluorescent tubes was found in the adsorbed state, and up to 3.5% of mercury was in the gas-phase. Unique mass-independent isotope fractionation values were found in the gaseous and adsorbed mercury in the fluorescent tubes. This fractionation is distinct from other emission sources and systematic; therefore, it can potentially be used to fingerprint mercury in fluorescent tubes in environmental samples.

This is the first report investigating the transformation of gaseous elemental mercury (GEM), the major form of airborne mercury, into oxidized mercury in bulk liquid, a possible sinking pathway of atmospheric GEM in clouds, fog, rain droplets and ocean spray. A 100–150 ng m−3 GEM standard gas, a 50–150 times higher concentration than the typical atmospheric concentration, was introduced into a 2.5 L rectangular glass vessel, at the bottom of which a 0.5 L uptake solution of pure water (pH 6–7), weakly acidified pure water with sulfuric or nitric acid (pH 3.2–3.6) or seawater (pH 8) was resting. The standard gas was introduced into the space above the solution in the vessel at the rate of 0.82 L min−1 and exited from the opposite end of the vessel, which was open to the room’s pressure. After exposing the solution to the gas for 0.5–4 h, a portion of the uptake solution was sampled, and the dissolved elemental mercury (Hg0aq) and dissolved oxidized mercury (Hg2+aq) in the solution were analyzed by the conventional trapping method, followed by cold vapor atomic fluorescent spectrometer measurements. The results showed that the quantities of total dissolved mercury (THgaq = Hg0aq + Hg2+aq) in the pure water and seawater were compatible, but those were slightly lower than the equilibrated Hg0aq concentrations estimated from Henry’s law, suggesting non-equilibrium throughout the whole solution. In contrast, the quantity of Hg2+aq and THgaq in the acidified pure water with sulfuric acid was significantly enhanced. Over the 4 h exposure, the THgaq concentrations were two times higher than the equilibrated Hg0aq concentration. This was due to the slow oxidation reaction of Hg0aq by the sulfuric acid in the bulk phase. Using the collision rate of GEM with the surface of the solution and the observed uptake, the estimated uptake coefficient of GEM by this uptake was (5.5 ± 1.6) × 10−6. Under the typical atmospheric concentration, this magnitude results in an atmospheric lifetime of 4970 years, negligibly small compared with other atmospheric oxidation processes.

Here, we introduce a new methodology developed for highly precise stable mercury isotope ratio (δHg) analysis: the sampling method collecting sufficient amount of gaseous elemental mercury (GEM) from air within 24 h or less and the extraction method effectively converting the collected GEM to Hg2+ in less than 10 mL of acidified solution.A big gold-amalgam trap (BAuT), which has approximately 11 times larger inner diameter of the tube and more gold-amalgam granular than a conventional gold-amalgam trap, was designed for quick and effective sampling of GEM in a short time period. A 24-h sampling demonstrated that the collection efficiency was higher than 99.9% under the flow rate of 55 LPM. Prior to the extraction the collected GEM by BAuT was pre-concentrated to a conventional gold-amalgam trap to reduce the dead volume.The GEM pre-concentrated was transferred into a four side sealed 2L Tedler bag with a PTFE stopcock by heating the gold-amalgam trap to 600 ºC for ~ 4 min under the 0.5 LPM flow of Hg-free air. Prior to this transfer 5mL of 0.5~40% (v/v) reversed aqua resia or RAR (hydrochloric acid: nitric acid = 1:2) was pre-introduced into the bag. The bag with GEM and RAR was left for the conversion of GEM into the stable state in the solution (i.e., Hg2+). The solution recovered was then analyzed by multi collector-ICP-MS for the Hg concentration and δHg.Results with a standard reference material showed that the recovery from the test with 10% RAR and the extraction duration of 8 days was the highest, 97%, with the 5% of recovery for the residual GEM in the gas-phase. The δHg analysis for five isotope ratios exhibited that the accuracy was between 0.01 and 0.3 ‰. Results from the analytical tests of ambient GEM using this methodology will be discussed.

A method involving fast large-volume sampling and bag extraction of total gaseous mercury (TGM) using a 5 mL acid solution was developed for stable mercury isotope ratio measurements. A big gold-coated sand trap (BAuT)—a 45 (i.d.) × 300 mm (length) quartz tube with 131 times more trapping material than a conventional gold trap—was used for the collection of a large amount of TGM. The collected TGM was extracted using 5 mL inversed aqua regia in a 2 L Tedlar bag followed by isotope measurements using a cold vapor generator coupled with a multicollector inductively coupled plasma mass spectrometer. Sampling tests demonstrated that the collection efficiency of the BAuT was 99.9% or higher during the 1–24 h sampling period under the flow rate of 20–100 L min−1. Recovery tests of 24 h bag extraction using 100 ng NIST SRM 8610 exhibited nearly 100% recovery yields. The five measured stable mercury isotope ratios agreed with reference values within 2σ intervals. The overall methodology tested during the pilot field and laboratory studies demonstrated its successful application in analysis, promising highly precise stable mercury isotopic data with a time resolution of less than 24 h.

Transboundary secondary organic aerosol (SOA) from the Asian continent may substantially influence the urban air quality of western Japan, where the local anthropogenic emissions are expected to be the major sources of airborne particulate organic matter. To better understand the influence of transboundary SOA, we conducted simultaneous field studies in March 2012 and December 2010 at sites in Fukuoka city and Fukue Island, representing an urban and a background site of the northern Kyushu region in western Japan, respectively. During the studies, high time resolution (10 min) measurements of organic aerosol (OA) and its carboxylate component (m/z 44) in fine particulate matter (PM1.0) were conducted using aerosol mass spectrometers. Independently, total suspended particulate matter was collected daily on filter media, and the concentration of the low-volatile water-soluble organic carbon (LV-WSOC) component, which was expected to include SOA, and its stable carbon isotope ratio (delta C-13) were analyzed by an elemental analyzer coupled with a high-precision isotope ratio mass spectrometer. Results showed that the concentrations of m/z 44 and LV-WSOC at Fukue were higher than those at Fukuoka, while the magnitude of OA at Fukue was comparable to or less than that at Fukuoka during the study periods. A comparison of the daily averaged concentrations of m/z 44 and LV-WSOC between the two sites showed high correlations during both study periods (r(2) higher than 0.72), while the OA concentrations were less correlated (r(2) higher than 0.47). Given that the OA, m/z 44, and LV-WSOC at Fukue were the transboundary transport origin, the high correlations imply the predominant contribution of m/z 44 and LV-WSOC from the transboundary origin in the Fukuoka urban air. A comparison between m/z 44 and LVWSOC concentrations showed high correlations (R-2 > 0.91) with similar slopes of linear regressions (ca. 0.3 mu g mu g(-1) of C) at both sites during the spring study. Furthermore, the delta C-13 plot of LV-WSOC as a function of the m/z 44 fraction in OA in the urban air showed a systematically increasing trend, which is evidence of predominant SOA in LV-WSOC and a binary mixture of primary and secondary OA in PM1.0. Although the same comparison for the winter study also displayed high correlations between LV-WSOC and m/z 44 at both sites (R-2 > 0.85), the slopes of the linear regressions were significantly different (0.58 and 0.22 mu g mu g(-1) of C for Fukuoka and Fukue, respectively) and the delta C-13 plot exhibited a random variation, indicating a complex mixture of OA and/or LV-WSOC. The series of findings suggest that SOA from the transboundary transport origin predominated LV-WSOC, even in the urban air of western Japan, where OA from the local origin was significant.

To study the origins of airborne particulate organic matter in southern Ontario, molecular marker concentrations were studied at Hamilton, Simcoe, and York Gateway Tunnel, representing industrial, rural, and heavy traffic sites, respectively. Airborne particulate matter smaller than 10 μm in aerodynamic diameter was collected on quartz filters, and the collected samples were analyzed for total carbons, 5-6 ring PAHs, hopanes, n-alkanes (C20 to C34), and oxygenated aromatic compounds. Results showed that PAH concentrations at all three sites were highly correlated, indicating vehicular emissions as the major source. Meanwhile, in the scatter plots of α,β-hopane and trisnorhopane, concentrations displayed different trends for Hamilton and Simcoe. The slopes of the linear regressions for Hamilton and the tunnel were statistically the same, while the slope for Simcoe was significantly different from those. Comparison with literature values revealed that the trend observed at Simcoe was explained by the influence from coal combustion. We also found that the majority of oxygenated aromatic compounds at both sites were in the similar level, possibly implying secondary products contained in the southern Ontario air. Regardless of some discrepancies, absolute principal component analysis applied to the datasets could reproduce those findings.

Field observations to investigate the correlation between New Particle Formation (NPF) and the long-range transport of air pollutants in the East Asia region were carried out on a rural Island of Japan in the East-China Sea (Fukue Island, 32.8 degrees N, 128.7 degrees E) over three periods (February 23 to March 7, 2013; November 7 to 20, 2013; and November 2 to 24, 2014). Frequent NPF events were identified (16 events in 50 days), typically in association with sudden increases in particle number concentrations and the successive growth of particles to mobility diameters of several tens of nanometers. The NPF events were classified into two types (A and B) according to the initially detected particle sizes (onset diameters). Type-A consisted of strong NPF events with onset diameters as small as 5 nm. Type-B consisted of NPF events whose onset (<10 nm) was not clearly identifiable. The correlations of SO2 concentrations, solar radiation, PM2.5 concentrations, and chemical composition were analyzed based on the types of NPF events. (C) 2016 Elsevier Ltd. All rights reserved.

Molecular marker analysis of environmental samples often requires time consuming preseparation steps. Here, analysis of low-volatile nonpolar molecular markers (5-6 ring polycyclic aromatic hydrocarbons or PAHs, hopanoids, and n-alkanes) without the preseparation procedure is presented. Analysis of artificial sample extracts was directly conducted by gas chromatography-mass spectrometry (GC-MS). After every sample injection, a standard mixture was also analyzed to make a correction on the variation of instrumental sensitivity caused by the unfavorable matrix contained in the extract. The method was further validated for the PAHs using the NIST standard reference materials (SRMs) and then applied to airborne particulate matter samples. Tests with the SRMs showed that overall our methodology was validated with the uncertainty of ~30%. The measurement results of airborne particulate matter (PM) filter samples showed a strong correlation between the PAHs, implying the contributions from the same emission source. Analysis of size-segregated PM filter samples showed that their size distributions were found to be in the PM smaller than 0.4 μm aerodynamic diameter. The observations were consistent with our expectation of their possible sources. Thus, the method was found to be useful for molecular marker studies.

Carbon kinetic isotope effects (KIEs) at natural abundances during photolysis of Fe3+-oxalato, malonato, and succinato complexes in aqueous solution were studied to identify the C-C bond cleaving mechanism of Fe3+-oxalato complexes under sunlight irradiation. Observed overall KlEs were 5.9 parts per thousand,11.5 parts per thousand, and 8.4 parts per thousand, respectively. This variation is inconsistent with secondary carbon KIEs for the Fe-O bond cleavage, but consistent with primary carbon KlEs for sequential cleavage of Fe-O and C-C bonds. Position-specific probability of C-13 content estimated KIEs of 5.9 parts per thousand, 17.2 parts per thousand, and 17 parts per thousand for C-12-C-13 bond cleavage, respectively, indicating the different KlEs for carboxyl-carboxyl and methyl-carboxyl cleavage. (C) 2016 Elsevier B.V. All rights reserved.

To understand the influence of transboundary secondary organic aerosol (SOA) in the urban air of Fukuoka, we conducted simultaneous field studies in December 2010 and March 2012 on Fukue Island and in the city of Fukuoka, representing a rural and an urban sites of western Japan. During the studies, organic aerosol in PM1.0 was analyzed by aerosol mass spectrometers. Independently, airborne total suspended particulate matter (TSP) was collected on filters, and low-volatile water soluble organic carbon (LV-WSOC) extracted from the TSP samples was analyzed by an elemental analyzer coupled with a high precision isotope ratio mass spectrometer for its concentration and stable carbon isotope ratio (d13C). Plots of LV-WSOC concentrations versus m/z 44 concentrations for the study in December 2010 showed high correlations (r2 > 0.85), but different slopes between the two sites (0.58 microg microgC-1 at Fukuoka and 0.22 microg microgC-1 at Fukue), indicating additional contribution of m/z 44 from local sources. Because of this complex composition, evaluation of transboundary SOA was unsuccessful in this case study. In contrast, comparison of LV-WSOC concentrations with the m/z 44 concentrations during the study in March 2012 showed high correlations (r2 > 0.91) with similar slopes (0.3 microg microgC-1) at both sites, indicating predominance of transboundary LV-WSOC. Furthermore, the plot of d13C of LV-WSOC as a function of m/z 44 fraction showed a systematic increasing trend, indicating SOA. These findings suggest that the observed LV-WSOC and m/z 44 in the Fukuoka air were predominated by transboundary SOA in this case study.