Isotopes serve as effective tracers for identifying pollutant sources, with carbon isotopes (δ13C) enabling the determination of the sources of carbonaceous aerosols in PM2.5. In this study, PM2.5 samples were collected in Changzhi, China, during winter and summer to determine the mass concentrations and stable carbon isotope (δ13C) of the organic carbon (OC) and elemental carbon (EC). The Bayesian mixing model (MixSIAR) was employed to determine the contributions to EC sources in PM2.5 based on δ13C values, and the results were compared with those from positive matrix factorization (PMF) receptor modeling, which used chemical concentrations. During sampling, the δ13COC values exhibited clear seasonal variations in their isotope levels of -23.44‰ in the winter and -26.81‰ in the summer, while δ13CEC exhibited no significant variations in the winter (-25.33‰) or summer (-26.37‰). δ13COC levels in the summer were obviously negative than in the winter, which indicated that δ13COC levels in the summer might be more influenced by secondary organic aerosols. The MixSIAR model identified five sources of EC in PM2.5: gasoline vehicle exhaust (summer: 26.5%; winter: 25.0%), diesel vehicle exhaust (43.5%; 28.0%), coal combustion (14.2%; 22.9%), biomass burning (11.6%; 17.2%), and road dust (4.2%; 6.9%), with distinct seasonal variability in contributions. The results obtained by the PMF model were generally consistent with the results mentioned above. Minor discrepancies in source contributions (e.g., biomass burning, road dust) were attributed to the uncertainty of the tests and methods. The consistency of the results between PMF and MixSIAR models provides cross-validation that reduces overall uncertainty in source apportionment. The preliminary application of carbon isotopes shown in this study highlights that isotopes are effective indicators for source apportionment of the atmospheric pollutants, providing a reliable and cross-validating perspective.

The lead-zinc mining activities have an impact on the metal(loid)s content in the environment within the mining area. However, the influence of these activities on the soil environment at greater distances, such as 30 km away, has received less attention. Furthermore, previous investigations often failed to take into account factors such as topography and weathering in their analyses. The present study explored the influences of lead-zinc mining on the migrations of sulfophilic metal(loid)s in soils, by analyzing geochemical characteristics of forest soil profiles from different locations on Baohua Mountain near a lead-zinc mine in the Nanjing area, China. The results show that Cd, Pb, Zn and Sb enrich in shallow soil (0-15 cm), possibly due to mining. Hillslope and foothill soils exhibit distinct elemental distribution. Slope soils has higher Pb, Cd, Sb, In, Zn, Ni, Cu, Al, Fe, K, Mg, Ti, S, and TOC contents but lower Mn and Ca contents compared to foothill soil. Ni, Cd, Fe, Al, K, Mg, Si, Ti, Na, S and TOC distributions are similar in slope and foothill profiles, while Pb, Sb, Cu, Zn, In, Mn, Ca, P, pH, Av-In and Av-Pb distributions differed obviously. Foothill soils show notable Cd, Pb, Zn and Sb leaching migration at 0-25 cm layer, with exogenous Pb migrating vertically up to 25 cm. Stronger weathering and leaching influence Pb, Zn, Sb, In and Cu migration mainly in slope soil's sub-surface layer (10-25 cm), with Cd leaching more prominent and Pb migrating farther vertically than in foothill soils.

Numerous studies have demonstrated that PM2.5-bound heavy metals pose non-negligible inhalation carcinogenic risks to the population. As one of the largest megacities in southwest China, Chengdu's industrial activity combined with its geographic features may present ongoing health challenges. By monitoring heavy metals and inorganic ion in atmospheric PM2.5 in Chengdu City for nine years, the inhalation health risks of 12 metal elements were analyzed by applying a year-weighted health risk assessment model. Afterwards, the sources of heavy metals and ions were resolved by using a positive matrix factorization (PMF) model. Further, 34 socio-economic development indicators in Chengdu were collected and analyzed by Spearman correlation and partial correlation to support the source resolution results. The health risks from different emission sources were further quantified. The median hazard index HI (interquartile range) for all metals measured was 0.26 (0.19, 0.31), indicating a negligible non-carcinogenic risk. The order of male’s carcinogenic risk was As (1.90 × 10–6 (1.40 × 10–6, 2.43 × 10–6)) > Cr (4.43 × 10–7 (3.21 × 10–7, 6.21 × 10–7)) > Cd (1.41 × 10–7 (9.68 × 10–8, 2.09 × 10–7)) > Pb (1.17 × 10–7 (8.59 × 10–8, 1.53 × 10–7)) > Ni (1.81 × 10–8 (1.27 × 10–8, 2.46 × 10–8)) > Be (5.01 × 10–9 (5.01 × 10–9, 5.10 × 10–9)), and similar patterns for female and child. PMF identified 5 possible sources of heavy metals, including the chemical industry, motor vehicles, soil dust, coal combustion, and the nonferrous metals industry. These sources were systematically supported and explained through trend and correlation analysis with Chengdu's socio-economic indicators. The non-ferrous metal industry and the chemical industry had the highest population cancer risk levels of 4.71 × 10–6 and 2.24 × 10–6, respectively. As (71.8

Investigating and quantifying the transfer of heavy metals from soil to rice plants under different environmental conditions is crucial. This study explores the characteristics of heavy metals transfer within soil-rice system and the environmental implications of translocation coefficients (TCs) through analysis of data from major rice-growing regions in Asia. The translocation patterns of different heavy metals demonstrate variability, varying across geographical areas. For instance, As and Cd show high transfer propensity from soil to roots (average TCs: 3.71 for As and 3.63 for Cd), but their subsequent retranslocation to straw is substantially constrained, with average TCstraw/root and TCgrain/straw values dramatically decreasing (0.18 for As and ≤ 0.45 for Cd). Rice plants effectively regulate the transport Cu and Zn from roots to aerial tissues: TC of Cu decreases from 0.87 (TCroot/soil) to 0.27 (TCstraw/root), then increased to 0.78 (TCgrain/straw); for Zn, TCroot/soil, TCstraw/root and TCgrain/straw are 0.74, 0.65 and 0.63, respectively. Cluster analysis reveals distinct translocation patterns, with elements like Pb in the Yangtze River Delta showing a “parabola” transfer pattern, characterized by anomalously high TCstraw/root, along with Cr, Ni and Hg. The sketched pattern generated by TCs exhibits available implication for environment condition. The abnormal translocation patterns observed for Pb, Cr, Ni and Hg suggest that these elements in rice aerial tissues may originate from atmospheric sources, influenced possibly by historical Pb-containing petrol use or non-ferrous mining activities.

This study uses a rapidly urbanizing urban agglomeration as a case to quantify the impact of key influencing factors (chemical weathering, geochemical processes, and human activities) on heavy metal(loid) concentration and bioavailability, providing scientific support for soil pollution control. Non–ferrous metal and Pb–Cd industries (e.g., batteries, electroplating, automobile exhaust emissions) serve as the primary anthropogenic sources for As, Cd, Cu, Hg, Pb, and Zn enrichment in soils, with contribution rates of 31–58

The stability of soil organic matter (SOM) is crucial for metal transport and carbon cycling. S,S-ethylenediaminedisuccinic acid (EDDS) is widely used to enhance phytoremediation efficiency for heavy metals in contaminated soils, yet its specific impacts on SOM have been underexplored. This study investigates the effects of EDDS on SOM stability using a rhizobox experiment with ryegrass. Changes in soil dissolved organic matter (DOM) quantity and molecular composition were analyzed via Fourier transform ion cyclotron resonance mass spectrometry. Results showed that the use of EDDS increased the uptake of Cu, Cd and Pb by ryegrass, but simultaneously induced the destabilization and transformation of SOM. After 7 days of EDDS application, dissolved organic carbon (DOC) and nitrogen (DON) concentrations in rhizosphere soils increased significantly by 3.44 and 10.2 times, respectively. In addition, EDDS reduced lipids (56.3%) and proteins/amino sugars-like compounds (52.1%), while increasing tannins (9.11%) and condensed aromatics-like compounds (24.4%) in the rhizosphere DOM. These effects likely stem from EDDS's dual action: extracting Fe/Al from SOM-mineral aggregates, releasing SOM into the DOM pool, and promoting microbial degradation of bioavailable carbon through chain scission and dehydration. Our study firstly revealed that the application of EDDS in phytoremediation increased the mineralization of SOM and release of CO2 from soil to the atmosphere, which is important to assess the carbon budget of phytoremediation and develop climate-smart strategy in future.

Heavy metal contamination in fine particulate matter (PM2.5) emitted in industrial cities is extremely severe. Hence, determining their pollution sources apportionment is critical to inform effective pollution control strategies for reducing the risks associated with heavy metals in PM2.5. This study comprehensively investigated the characteristics, source apportionment, and health risks associated with heavy metals in PM2.5 at three monitoring stations-Jiance, Qinghua, and Shenjiju-in Changzhi, a typical industry city in China, during three seasons: autumn and winter of 2017 and summer of 2018. The daily average concentrations of PM2.5 (65.68 mu gm  3) during the study period were lower than the second-grade limit value established in China (75 mu g m  3). The highest mean PM2.5 concentrations were observed during winter (72.45 mu gm  3) and at the Jiance station (64.51 mu g m  3), respectively. At Qinghua station, vehicle emissions contributed more V to PM2.5, whereas Jiance station showed higher levels of Pb and Zn from coal combustion. In autumn, there was an increased in the Fe content in PM2.5 from vehicle emissions, whereas elevated concentrations of Cr and Ni from industry sources were observed in summer. According to the results of a positive matrix factorization, the main sources of PM2.5-bound heavy metals in Changzhi were coal combustion (34.3%), vehicle emissions (30.9%), fugitive dust (21.8%) and industry (13.0%). The major sources during autumn, winter, and summer were vehicle emissions (39.0%), coal combustion (35.0%), and industrial emissions (61.7%), respectively, showing a clear seasonal pattern. At both the Jiance station and Shenjiju station, extensive coal-based heating was the primary source of emissions, whereas vehicle emissions were the main source of emissions at QH owing to its high levels of traffic. The total hazard quotient (HQ) values for heavy metals were below the safe level (HQ = 1); but the carcinogenic risks (CR) exceed the lower limit of tolerance (1E-6). Stronger emissions from industrial sources in summer and the large amount of coal combustion for heating at the Jiance station are possible reasons for the higher health risk of heavy metals. Identification the source of PM2.5-bound heavy metals could support the targeted reduction of associated emissions, consequently helping alleviate heavy metals contamination and control associated risks to human health.

The Sanjiang orogenic belt in the southeastern Tibetan Plateau provides an excellent record of the Paleo-Tethys tectonic evolution. This study introduces new constraints on the spatio-temporal evolution of the Paleo-Tethys through zircon U-Pb ages, in-situ Lu-Hf isotope data, and analyses of whole-rock major oxides, trace elements, and Sr-Nd-Pb isotopic compositions from Late Paleozoic mafic rocks in the Lancang tectonic belt. The mafic rocks from the Xiaoheijiang, Banpo, and Yakou areas were dated to approximately 281-267 Ma, 295-292 Ma, and 293-291 Ma, respectively. The Xiaoheijiang mafic rocks exhibit geochemical signatures resembling those of fore-arc basalt, characterized by low (La/Sm)N, relatively flat rare earth element (REE)-normalized patterns, positive epsilon Nd(t) (+5.6 to +10.1), and zircon in-situ epsilon Hf(t) values (+10.0 to +14.9). These features indicate an origin from a depleted mantle source with minor contributions from slab-derived components. The Banpo and Yakou mafic rocks display geochemical affinities to back-arc basin basalt, similar to the Okinawa Trough back-arc basin basalt. Their epsilon Nd(t) values range from +5.6 to +9.9 and epsilon Hf(t) values from +9.5 to +15.0, suggesting derivation from a mantle wedge source modified by slab-derived fluids or melts. In combination with available geochronological data concerning the Paleo-Tethys evolution along the Lancang tectonic belt, our findings support the hypothesis that the slow-speed, low-angle subduction of the Paleo-Tethys Ocean led to the formation of a forearc accretionary complex. The slab-derived fluids metasomatized the mantle wedge as subduction depth and angle increased, facilitating the development of the Lincang arc magmatism and the opening of the Banpo-Yakou back-arc basin. Continuous subduction promoted slab retreat under gravitational forces, inducing the upwelling of depleted mantle and the forming of forearc magmas.

China is one of the main locations in which rice agriculture occurs, with East China now playing a significant role in research on rice domestication and culture interactions. However, the exact timing of sustained rice domestication and the process of prehistoric cultural exchange in East China remain unclear. Here, we present phytolith records of two profiles from Lingjiatan in the Chaohu Lake Basin. Our results show that rice cultivation was practiced throughout the Lingjiatan culture period (5800-5300 cal BP), and that sustained rice domestication began around 5500 cal BP, which was later than on the Taihu Plain (similar to 6200 cal BP), Ningshao Plain (similar to 5800 cal BP), and along the middle and lower Huai River (similar to 5800 cal BP). Combining other archaeological records and geomorphological features in East China, we hypothesize three possible routes for the spread of rice cultivation and cultural exchange between the lower Yangtze River and the middle and lower Huai River. Lingjiatan, situated at the intersection of two of the possible routes, experienced a gradual increase in its settled population as a result of cultural exchange and technological innovations in cultivation, thereby giving rise to its distinctive culture. This study demonstrates the significant role of Lingjiatan in facilitating transportation and fostering cultural exchange in East China during the mid-Holocene.

Heavy metals (Ni, Cr, W, Cd, and Pb) and rare earth elements (REE) were investigated in the flood plain sediments of an island of the lower Yangtze River near Nanjing to determine how the vertical distribution of heavy metals could be affected by natural sedimentation processes and anthropogenic contamination. Stratigraphic analyses of magnetic susceptibility and the mean grain size distribution of the deposits enabled us to identify layers associated with a relatively high influx of suspended sediments that resulted in sudden changes in the concentrations of heavy metals. The results show that layers associated with high sediment influx (0.8 m depth) displayed low concentrations of Cr, Ni, W, and Cd that were mainly lithogenic in origin. The Post Archean Australian Shale (PAAS) normalized REE patterns in the flood plain cores were enrichment in Ce and Eu relative to PAAS, indicating that the sediments were most likely derived from a mixture of sediments and not from an anthropogenic source. Sharp increases in Y/Ho ratios, as well as heavy metal (Cd, Cr, Ni, and W) and Y concentrations were observed in the uppermost layer that could have been deposited from the rapid transport of sediment-laden, contaminated waters. The temporal (vertical) trends in Pb concentrations may be strongly influenced by coal burning. Elevated Pb concentrations (350 ppm and 1000 ppm) correlate with high magnetic susceptibility (> 200 m 3 × kg −1 ) and the history of thermal power plant (1910–2002) activity. The anthropogenic inputs of Pb were, however, not diluted by high suspended sediment loads, which supports the argument that Pb was derived from fly ash.

Utilizing sulphidic copper tailings (SCT) with rich sulfur content in cementitious materials presents a challenge due to its incompatibility with cement. For the bulk use of SCT, this paper demonstrated that alkali-activated slag (AAS) can be a good binder for SCT, and the effects of SCT addition on the setting time, hydration products, microstructure, compressive strength, pore structure, and autogenous shrinkage of AAS were investigated. Results showed that introducing SCT into AAS facilitated the generation of sulfate-containing products during GGBS hydration, e. g., gypsum and ettringite, since the pyrite in SCT is prone to oxidation, leading to the formation of sulfates. SCT can work as an auxiliary activator for GGBS along with NaOH to accelerate the hydration of ground granulated blast furnace slag (GGBS). Consequently, the gel pores of AAS mortar increased, the microstructure of AAS mortars was densified and the compressive strength was improved by 5.5-19.8 % at 28d. In addition, the addition of SCT delayed the setting of the AAS paste, and the autogenous shrinkage of the mortars was mitigated by 27.2-35.8 %.

The use of magnetic susceptibility (χ) as a means of assessing heavy metal pollution in soils has been explored by researchers, yielding varying results in terms of the correlations between χ with heavy metals. The efficacy of χ as an indicator of soil heavy metal pollution remains a topic of debate. This study aims to elucidate the inter-relationships between χ, iron oxides, and heavy metals in soil through the application of a modified 5-step sequential extraction procedure (SEP), and to identify an effective approach for assessing metal concentrations in soil using magnetic susceptibility measurements. The soil samples were collected from a typical alluvial island in the lower Yangtze River, China, and a total of 6 forms (exchangeable and acid soluble fraction, easily reducible fraction, oxidizable fraction, amorphous iron oxide, crystallized iron oxyhydroxides and residual fraction) were partitioned and their heavy metal concentrations and χ were analyzed. The results show that crystalline Fe oxyhydroxides and residual fractions are the two uppermost fractions of heavy metals. By combining the fractionation of elements with the variation of χ of the soil during the processing of SEP, it was inferred that the external input of Fe, Pb, Cr and Cd in the soil likely originated from the vicinal steel production. The correlation analysis revealed a significant correlation between heavy metal concentrations and χ in the residual fraction, whereas no significant correlations were observed between the concentrations of heavy metals and χ in the bulk soil samples. It is recommended that the evaluation of heavy metal contamination in the soil neighboring industrial sites can be conducted via magnetic susceptibility measurements subsequent to the elimination of crystalline iron oxyhydroxides.

Although industrial emissions are the major pollution source of PM2.5-bound Pb, which affects air quality in cities, their influence has gradually decreased with the enhancement of industrial control in recent years. Thus, at present, the source of PM2.5-bound Pb is unclear, especially in an industrial city in North China. In this study, by incorporating the stable Pb isotopic compositions into a Bayesian isotope mixing model (MixSIAR), source apportionment of PM2.5-bound Pb was conducted during autumn and winter in 2017, and summer in 2018 in Changzhi. The daily average concentrations of PM2.5 and PM2.5-bound Pb during the study period were lower than the second-grade limit value of China (75 mu g m(3)) and the Chinese National Ambient Air Quality Standard (1 mu g m(3)), respectively. The pollution sources of PM2.5-bound Pb were fully distinguishable using Pb isotopes. In Changzhi, the Pb-206/Pb-207 ratio in soil (average: 1.0891) and exhaust dust from gasoline (average: 1.0832) and diesel (average: 1.0814) showed low levels of Pb isotope signature in Changzhi, whereas the rest of the source exhibited Pb isotope signature levels. The source apportionment results revealed that in an industrial city with many steel and coking plants, the primary source of PM2.5-bound Pb were motor vehicle emission (29.7%) and coal combustion (26.9%), rather than industrial emission (26.5%). Moreover, seasonal variations in PM2.5 of Pb sub-sources were observed: soil dust (21.7% and 18.4%) and diesel motor vehicles emission (16.4% and 15.6%) in summer and autumn; domestic coal combustion (17.1%) and coal-fired power plant emission (15.5%) in winter. The carcinogenic risk from motor vehicle emission in autumn was higher than that from industrial and coal sources in winter, and higher than that from motor vehicle sources in summer. This finding is a critical evidence of an anomalistic enrichment of PM2.5-bound Pb in an industrial city. These results obtained through Pb isotopic composition and MixSIAR model also improved the accuracy of source apportionment of atmospheric PM2.5-bound Pb, representing a high scientific significance and reference value for Pb pollution control in North China.

Improving air quality in the Yellow River Golden Triangle Demonstration Area (YRGTDA) is an important practice for ecological protection and high-quality development in the Yellow River Basin. Preventing and controlling PM2.5 pollution in this region will require a scientific understanding of the spatiotemporal patterns and characteristics of PM2.5 pollution. PM2.5 data from different sources were combined in this study (the annual average of PM2.5 concentrations were obtained from the Atmospheric Composition Analysis Group of Dalhousie University, and the daily PM2.5 concentration data were obtained from the China National Environmental Monitoring Centre). Then, the temporal variation of PM2.5 concentrations at annual, seasonal, and monthly scales, the spatial variation of PM2.5 concentrations, and the variation of PM2.5 pollution classes were analyzed. Results showed that: (1) at the annual scale, the PM2.5 concentrations showed a decreasing trend from 2000 to 2021 in the study area. The variation of PM2.5 concentrations were divided into two different stages. (2) At the seasonal scale, high PM2.5 concentrations occurred mainly in winter, low PM2.5 concentrations occurred in summer. At the monthly scale, PM2.5 concentrations showed a U-shaped variation pattern from January to December each year. (3) The hotspot analysis of the PM2.5 concentrations in the study area showed a cyclical variation pattern. (4) The PM2.5 concentrations exhibited a spatial pattern of high values in the central and low values in the northern and southern parts of YRGTDA. (5) The number of days for different PM2.5 pollution classes from 2015 to 2021 followed the order of Good > Excellent > Light pollution > Moderate pollution > Heavy pollution > Severe pollution in YRGTDA. The results of this study have great theoretical and practical significance because they reveal the spatiotemporal patterns and pollution characteristics of PM2.5 and will lead to the development of scientifically based measures to reasonably prevent and control pollution in YRGTDA.

In order to explore the migration and transformation of lead（Pb） and the contribution of human activities to Pb in the soil, we collected the samples from two soil profiles at the hillside and piedmont of Baohua Mountain, which is located in the vicinity of a Pb-Zn mine from the Ning-Zheng area. By using the chemical sequential extraction and Pb isotopic fingerprint, the transformation of Pb in the soil profiles was investigated and the anthropogenic contribution of Pb was quantified. The results showed that the mining activities led to a marked Pb enrichment in the topsoil with the concentration of 2.9-7.7 μg/g higher than the local background. The exogenous Pb in the topsoil transported downward via the particle migration and leaching, and the migration mainly occurred at the layer of 10-25 cm. The maximum migration distance of Pb at the piedmont increased by 5 cm compared to that at the hillside. Pb in the soil was mainly bound to the residual fraction, iron/manganese oxides, and subordinately, bound to carbonates and humid fraction. Compared to the soil at the hillside, the soil at the piedmont were observed with significantly lower concentrations of Pb bound to carbonates, humid fraction Pb and exchangeable fraction Pb, respectively, but higher concentration of Pb bound to iron/manganese oxides. Part of Pb bound to carbonates and humid in the topsoil resolved and moved into the deeper soil, in where was fixed by iron/manganese oxides. The Pb isotopic fingerprinting pinpoints that approximately 17.1% of Pb in the forest topsoil（0-5 cm） at the hillside was sourced from the Pb-Zn ore mining activity, and the contribution of anthropogenic activity on Pb concentration deceased with the increasing soil depth（＜ 3% at 15-20 cm）, implies that the exogenous Pb had moved down no more than 30 cm. Due to the eluviation, the contribution rate of anthropogenic source on the Pb in the topsoil（0-5 cm） at the piedmont was obviously lower than that at the hillside, and the contribution rate of anthropogenic source on the Pb in the other layers at the piedmont was similar, showed no evident descend with the depth increases. The Pb isotopic fingerprinting and high-resolution sampling on soil profile can quantify the influence of anthropogenic activity on the metal in the environment, and also recommend the scientific basis for environmental management.

This paper was carried out to functionalize the surface of powdery waste plastics (PWP) using polydopamine (PDA) for better utilization of this waste. The effects of PDA-functionalization of PWP on the compressive strength and durability of mortars were investigated. Experimental results confirmed the formation and deposition of PDA film on PWP, which gives the functionalized PWP improved wettability and chelating capacity with Ca2+. By adding PDA-functionalized PWP, the fluidity of the produced mortars was improved, and the interface of the PDA-functionalized PWP and surrounding pastes was densified with few cracks and less pores. The durability in terms of capillary water absorption and electric flux of mortars were respectively reduced by 4.08—11.93% and 12.16—21.86% by adding PDA-functionalized PWP. Moreover, the compressive strength of these mortars was increased by 10.8—26.1% at 3d, 13.5—24.7% at 7d, and 4.2—19.4% at 28d.

The contributions of natural versus anthropogenic forces on temporal changes of metals in the soil of the Yangtze River delta region were successfully quantified by combining repeated soil sampling, geostatistics and the modified principal component scores and multiple linear regressions approach. The findings show that the mean concentrations of Cu, Cd, As, Hg, Cr and Ni generally exhibited a decrease trend from 2010 to 2020. The decline of soil Hg was most outstanding, decreased by 20 % as a whole. The result of the modified principal component scores and multiple linear regressions approach suggests that the decrease of Hg content was predominately driven by the geochemical processes, with 48 % contribution. The mean soil Pb concentration increased by 40 % from 2010 to 2020. Approximately 76 % of the Pb change was attributed to the strengthened development of Pb-containing battery industry in the south part of the Yangtze River delta region. The Pb battery industry development also contributed 48 % of the change of Cd. The anthropogenic activities involving Cu, Zn or fossil fuel consumption contributed 32-35 % of the changes of As, Cu and Zn concentrations in the soil, and the steel industries contributed 82 % of Cr and 60 % of Ni changes, respectively.

Trace elements play a crucial role in the growth and health of organisms. Imaging the distribution of trace elements in organisms at micron resolution scale can reveal the chemical form and transfer mechanism of trace elements in organisms and their influence on the growth of organisms. In the present study, we used a high-resolution secondary ion mass spectrometer (NanoSIMS) to image the trace elements zinc (Zn), iron (Fe), magnesium (Mg) and potassium (K) in the wheat grain and analyzed the chemical form of Zn. The NanoSIMS images indicate that the micro-distributions of Zn, Fe, Mg and K in the wheat grain are similar, especially for Zn and Fe, mostly in the phytate granules of the aleurone and closely associated with P and H–O. Besides being distributed in phytate granules, some or a small amount of Mg and K are also distributed in starch granules of the endosperm. The S and C–N distributions are very similar, mainly in the protein matrix of the endosperm and aleurone. P and H–O, rather than S and C–N, are the two dominant ligands to Zn, Fe, K and Mg in wheat grain. The dominant chemical form of Zn and Fe in the wheat grain is in the phytate, not the protein. The P is crucial to Zn, Fe, Mg and K accumulation in the wheat, and agricultural producers should pay special attention to adjust the application of P fertilizer to affect the concentrations of Zn in the crop. In situ imaging of NanoSIMS can elucidate the relations between trace elements in grain samples with clear visualization, and it also has great significance in chemical analysis, crop breeding and environmental monitoring.

Ammonia is essential for the generation of secondary inorganic aerosols (SIA) in particulate matter, which affects severely the air quality in north China. In this study, PM2.5 sampling was conducted as well as gaseous pollutant concentration and meteorological parameters were measured from November 2017 to January 2018. PM2.5 concentration was highest in the industrial site (94.8 +/- 41.7 mu g m- 3), followed by urban (40.9 +/- 24.1 mu g m(-3)) and rural (35.6 +/- 20.3 mu g m(-3)) sites. The mass ratio of NO3-/SO42-exhibited clear site variations, with the highest average value of 1.2 was found at the urban site, likely due to the dense traffic volume resulting in higher emissions of NO2, and the lowest value of 0.9 at the industry site. The presence of Excess-NHx (E-NHx), raising the pH 24 by 1.4, 1.3, and 1.4 units in industry, urban, and rural sites, respectively, might be vital for raising the aerosol pH. Correlation coefficients of Nitrogen oxidation rate (NOR, NOR = [NO3-]/[NO3-] + [NO2]) vs. Photochemical oxidants (Ox, NO2 +O-3 in our study) and NOR vs. aerosol water content (AWC) at three sites were implied that both homogeneous and heterogeneous reactions occurred for nitrate formation in industry site, while heterogeneous reactions were dominant in urban and rural sites. Oxidation rates were most sensitive to the variation of E-NHx concentration at rural site, followed by the urban and industry sites, which was shown by the fact that the increase in E-NHx concentration by 1.0 mu gm(-3) increased the SIA concentration by 1.21, 1.02, and 0.37 mu gm(-3) at rural, urban, and industry sites, respectively. With the increase in NHx emissions at present, the role of NHx in SIA formation at ammonia-rich atmosphere requires more attention, especially in the less-noticed rural areas.