Institute of Earth Environment
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Interactive assessment of lignite and bamboo-biochar for geochemical speciation, modulation and uptake of Cu and other heavy metals in the copper mine tailing
No full textThis study was designed to examine the combined effect of bamboo-biochar (BC) and water-washed lignite (LGT) at copper mine tailings (CuMT) sites on the concentration of Cu and other metals in pore water (PW), their bioavailability, and change in geochemical speciation. Rapeseed (first cropping-season) and wheat (second cropping-season) were grown for 40-days each and the influence of applied-amendments on both cropping seasons was observed and compared. A significant increase in pH, water holding capacity (WHC), and soil organic carbon (SOC) was observed after the applied amendments in second cropping-seasons. The BC-LGT significantly reduced the concentration of Cu in PW after second cropping seasons; however, the concentration of Pb and Zn were increased with the individual application of biochar and LGT, respectively. BC-LGT and BC-2% significantly reduced the bioavailability of Cu and other HMs in both cropping seasons. The treated-CuMT was subjected to spectroscopic investigation through X-ray photoelectron spectroscopy (XPS), Fourier transform Infrared spectroscopy (FTIR), and X-ray powder diffraction (XRD). The results showed that Cu sorption mainly involved the coordination with hydroxyl and carboxyl functional groups, as well as the co-precipitation or complexation on mineral surfaces, which vary with the applied amendment and bulk amount of Mg, Mn, and Fe released during sorption-process. The co-application of BC-LGT exerted significant effectiveness in immobilizing Cu and other HMs in CuMT. The outcomes of the study indicated that co-application of BC-LGT is an efficacious combination of organic and inorganic materials for Cu adsorption which may provide some new information for the sustainable remediation of copper mine tailing.
(c) 2021 Elsevier B.V. All rights reserved
Loss of E-cadherin due to road dust PM2.5 activates the EGFR in human pharyngeal epithelial cells
No full textExposure to road dust particulate matter (PM) causes adverse health impacts on the human airway. However, the effects of road dust on the upper airway epithelium in humans remain unclear. We investigated the involvement of the epidermal growth factor receptor (EGFR) after PM with an aerodynamic diameter of < 2.5 mu m (PM2.5)-induced E-cadherin disruption of human pharyngeal epithelial cells. First, we collected road dust PM2.5 from 10 Chinese cities, including Wuhan, Nanjing, Shanghai, Guangzhou, Chengdu, Beijing, Lanzhou, Tianjin, Harbin, and Xi'an. Human pharyngeal FaDu cells were exposed to road dust PM2.5 at 50 mu g/mL for 24 h, cytotoxicity (cell viability and lactate dehydrogenase (LDH)) was assessed, and expressions of the proinflammatory interleukin (IL)-6 and high-mobility group box 1 (HMGB1) protein, receptor for advanced glycation end products (RAGE), occludin, E-cadherin, EGFR, and phosphorylated (p)-EGFR were determined. The E-cadherin gene was then knocked down to investigate EGFR activation in FaDu cells. Exposure to road dust PM2.5 resulted in a decrease in cell viability and increases in LDH and IL-6. Our data suggested that PM2.5 could decrease expressions of occludin and E-cadherin and increase expressions of EGFR and p-EGFR, which was confirmed by E-cadherin-knockdown. Our results showed a negative association between the alterations in E-cadherin and total elemental components in correlation analysis, especially S, Cl, K, Ti, Mn, Fe, Cu, Zn, and Pb. Exposure to metals in PM2.5 from road dust may lead to loss of the barrier function of the upper airway epithelium and activation of the EGFR. Our study showed the adverse effects of road dust PM2.5 on pharyngeal epithelial cells of the human upper airway
Bioremediation of wastewater containing mercury using three newly isolated bacterial strains
No full textTo successfully clean and recycle heavy metal-contaminated wastewater, we developed a fast, simple, low-cost, and efficient bioremediation method to eliminate mercury (Hg) pollution. We isolated three bacterial strains with strong Hg tolerance and reduction capacities from the polluted waters of the Yellow River. These bacterial strains mainly reduced Hg2+ by the mer operon. The bacterial strains had the best treatment effect on Hg-contaminated wastewater when mixed in equal proportions. Under the optimum growth conditions of the bacterial strains, it would take about 60 L of the three strains in the same proportion in a cultured solution to treat 1 ton of wastewater containing 10 mg/L Hg2+. After 48 h of treatment, the concentration of Hg2+ in the wastewater could reach the national standard (Hg2+ <0.05 mg/L). The bacterial strains also exhibited tolerance and transformational abilities for Pb2+, Cr6+, As5+, and Cd2+, indicating that these bacteria could be utilized in more complex heavy metal-polluted environments. This work revealed a new method for the bioremediation of heavy metal-polluted wastewater. (C) 2021 Elsevier Ltd. All rights reserved
Millennial-scale interaction between the East Asian winter monsoon and El Nino-related tropical Pacific precipitation in the Holocene
No full textBoth the East Asian winter monsoon (EAWM) and El Nino (EN) activities are vital climate modes that regulate the Pacific hydrologic cycle. However, the Holocene interactions among the EAWM, EN activities, and tropical Pacific precipitation remain unclear due to the lack of appropriate EAWM proxies. Here, we present high-resolution grain size records from the East China Sea shelf along with a transient climate model simulation to study the Holocene EAWM evolution and compare the findings with paleo-EN precipitation-related proxies records. The millennial-scale oscillations of grain size records, which are indicative of the intensity of the EAWM-driven coastal current, reveal an anti-phase coupling between the EAWM and EN-related tropical Pacific precipitation on a millennial timescale since 5.8 ka. These results, which are consistent with simulation results, indicate that the intensified EAWM could not only reduce equatorial western Pacific precipitation by reducing the sea surface temperature but also likely change boundary conditions in the tropical Pacific (i.e., the east-west Pacific temperature gradient and westerly anomaly) to favor the formation of subsequent intensive EN activities. The enhanced EN activities, inferred by the positive tropical eastern Pacific precipitation anomalies, could subsequently suppress the EAWM through anomalous low-level anticyclones and associated southerly anomalies, thereby generating intensified tropical western Pacific (mainly tropical monsoon areas) precipitation. Our study highlights these intrinsic interactions during the mid- to late Holocene and has useful implications for understanding this millennial-scale climate oscillation, which may represent periodic atmospheric exchange between high- and low-latitude climate systems by mediating the EAWM
Enhanced formation of secondary organic aerosol from photochemical oxidation during the COVID-19 lockdown in a background site in Northwest China
No full textThe COVID-19 pandemic has drastically affected the economic and social activities, leading to large reductions in anthropogenic emissions on a global scale. Despite the reduction of primary emissions during the lockdown period, heavy haze pollution was observed unexpectedly in megacities in North and East China. In this study, we conducted online measurements of organic aerosol in a background site before and during the lockdown in Guanzhong basin, Northwest China. The oxygenated organic aerosol (OOA) increased from 24% of total OA (3.2 +/- 1.6 mu g m(-3)) before lockdown to 54% of total OA (4.5 +/- 1.3 mu g m(-3)) during lockdown, likely due to substantial decrease of NOx emissions during lockdown which resulted in large increase of O-3 and thus atmospheric oxidizing capacity. OOA showed higher mass concentrations and fractional contributions during lockdown than before lockdown, and increased with the increase of Ox in both periods. In comparison, aqueous secondary organic aerosol (aqSOA) showed high mass concentrations and fractional contributions in both polluted periods before and during lockdown with the increase of aerosol liquid water content (ALWC). The increase of aqSOA under high ALWC conditions is very likely the reason of pollution events during lockdown. Combined with trajectory analysis, the absence of Guanzhong cluster in polluted period during lockdown may play a key role in the OA variations between two polluted periods. In addition, when comparing the clusters from the same transmission directions between before lockdown and during lockdown, the OA fractions showed similar variations during lockdown in all clusters, suggesting the OA variations are widespread in northwest China. (C) 2021 Published by Elsevier B.V
Meteorology driving the highest ozone level occurred during mid-spring to early summer in Shanghai, China
No full textMore recent studies highlighted the aggravated surface ozone (O-3) pollutions occurred in Spring and Autumn in China, but presenting clear distinctions for different cities. In this study, we observed the most elevated mean daily and maximum daily 8-h (MDA8) O-3 concentrations occurred from mid-Spring to early Summer (April, May and June, AMJ) at both urban and remote sites in Shanghai compared to other warm months (March, July, August, September, October), based on the long-term measurements from 2010 to 2019. The typical weather pattern of G-SW (High pressure with predominant winds of southwesterly) recognized by T-mode principal component approach (T-PCA), exhibits the strongest solar radiation and highest daily maximum temperature relative to other weathers in AMJ, leading to not only the most elevated O-3 concentration, but also the largest O-3 increasing variability in daytime. More importantly, under the G-SW weather condition, the MDA8 O-3 concentration presents the greatest increasing rate at 3.95 ppbv/yr from 2010 to 2019 in Shanghai downtown compared to other weather patterns, suggesting that more occurrence and faster exacerbation of O-3 pollutions could be expected under the G-SW weather condition in the future. To understand and mitigate high O-3 occurrences under the weather pattern of G-SW during AMJ, process analysis by a chemical/dynamical model (WRF-Chem, Weather Research and Forecasting (WRF) model coupled with Chemistry) is conducted to elucidate the strong O-3 productivity (19 ppbv/h in daytime), that dominates the high O-3 occurrence under the G-SW weather condition. Sensitive studies suggest that under the G-SW weather condition, reduction of VOCs emissions is very effective to prevent the high O-3 pollution in Shanghai. The model results show that photochemical productivity decreases by 35% in daytime response to 30% reduction of VOCs emissions, leading to 17.6% mitigation of peak O-3 concentration in Shanghai downtown. This result provides valuable information for the development of emission control strategy in Shanghai under different weather conditions. (C) 2021 Published by Elsevier B.V
Evaluation of PM2.5 fluxes in the "2+26" cities: Transport pathways and intercity contributions
No full textTo comprehensively evaluate the transport pathways and regional sources of PM2.5 in the "2 + 26" cities, air quality simulations using WRF-Chem were pursued over January, April, July, October 2015. The seasonal characteristics, vertical distributions of PM2.5 fluxes, and transport pathways were investigated. The model reasonably predicted the meteorological parameters (e.g., T2, Q2, WS10, and WD10) and air pollutants in both evaluated domains. The horizontal PM2.5 fluxes were strong in October (1221 kt, -1222 kt) and April (1119 kt, -1142 kt) and weak in January (933 kt, -997 kt) and July (589 kt, -809 kt). The directions of horizontal flux contributors relative to their target cities were entirely different in January and July. The same pattern can also be found at vertical layers. However, there was no uniform direction seen in April and October. A total of 14 pathways at the boundaries of the "2 + 26" cities were identified. The SW-NE pathways, which were dominant in Beijing and Tianjin with flux contributions of 65% and 75%, were found in all four months. The NW-SE pathways, which were the major pathways of Taiyuan (87%), and the W-E pathways, which were the major pathways of Zhengzhou (44%) and Jinan (43%), always showed different directions in January and July, following the directions of prevailing winter and summer monsoon winds. Moreover, Shijiazhuang (42%) and Handan (48%) were dominated by S-N pathways, which showed different patterns throughout the four months. The results could be helpful for implementing policies aimed at ecological compensation and joint air pollution control
Records of iodine isotopes (I-129, I-127) in the Barkol peat bog from northwest China and their sources, transport and preservation
No full textThe research on geochemical behaviors of iodine is significant for deep understanding of the source and distribution of iodine on the earth. However, as one of the most important sources, the ocean emissions and relative transport pathways of iodine, as well as the preservation after deposition are still not well known, especially in the arid areas of central Asia. A peat sediment core collected nearby Barkol Lake from northwest China was analyzed for iodine isotopes (I-127 and I-129). The observed high I-127 concentration in the top 2 cm indicated a significant accumulation of iodine in the surface oxic conditions due to the continuous sources of incompletely decomposed organic matter. Dissociation of iodine into pore waters occurred once the anoxic conditions established beneath the surface by a serial reduction reaction during the degradation of organic matter. The temporal variation of anthropogenic I-129 in the peat sediment recorded its sources and transport pathways. Besides the global fallout I-129 during late 1950s and early 1960s, the significantly increased air releases from the European nuclear fuel reprocessing plants during 1975-1997 and the increased marine discharges since 1990s contributed the major portion of I-129 in the peat core. The major transport pathway of I-129 from the Europe was through Westerlies following the re-emission of the marine discharged I-129 to the atmosphere, indicating a clearly ocean emitted iodine in the concerned central Asia. (C) 2021 Elsevier Ltd. All rights reserved
Salinity-controlled isomerization of lacustrine brGDGTs impacts the associated MBT5ME terrestrial temperature index
No full textBranched glycerol dialkyl glycerol tetraethers (brGDGTs) are microbial molecular fossils ubiquitous in natural environments. The correlation between the Methylation Index of brGDGTs (the MBT5ME paleothermometer) and temperature offers an important tool for reconstructing past terrestrial temperatures. However, factors other than temperature could also affect the distribution of brGDGTs in lacustrine systems, hampering the quantitative application of this paleothermometer. Here we investigated brGDGT distributions in contemporary sediments collected from 52 lakes in mid-latitude Asia. Combined with published brGDGT data from other lakes across the globe, we have found a strong salinity control on the relative abundance of 5-methyl brGDGTs versus their late-eluting isomers (including 6-methyl, 7-methyl, and unknown isomers). This allows the development of novel indices based on the isomerization of brGDGTs for tracing past lake water salinity. We also demonstrate , that salinity-controlled isomerization of pentamethylated and hexamethylated brGDGTs can significantly impact the MBT5ME paleothermometer, , potentially leading to an overestimation of past temperature, but the temperature signal can be extracted out of the MBT5ME index after correcting the salinity effect. As demonstrated in application to a Lake Qinghai (China) sediment core spanning the last 18 kyr, our finding could facilitate the simultaneous retrieval of reliable temperature and salinity records using brGDGTs in lacustrine settings, in particular for lakes that have experienced large salinity changes during the geological past. (C) 2021 Elsevier Ltd. All rights reserved
The impact of COVID-19 lockdown on atmospheric CO2 in Xi'an, China
No full textLockdown measures to control the spread of the novel coronavirus disease (COVID-19) sharply limited energy consumption and carbon emissions. The lockdown effect on carbon emissions has been studied by many researchers using statistical approaches. However, the lockdown effect on atmospheric carbon dioxide (CO2) on an urban scale remains unclear. Here we present CO2 concentration and carbon isotopic (813C) measurements to assess the impact of COVID-19 control measures on atmospheric CO2 in Xi'an, China. We find that CO2 concentrations during the lockdown period were 7.5% lower than during the normal period (prior to the Spring Festival, Jan 25 to Feb 4, 2020). The observed CO2 excess (total CO2 minus background CO2) during the lockdown period was 52.3% lower than that during the normal period, and 35.7% lower than the estimated CO2 excess with the effect of weather removed. A Keeling plot shows that in contrast CO2 concentrations and 813C were weakly correlated (R2 = 0.18) during the lockdown period, reflecting a change in CO2 sources imposed by the curtailment of traffic and industrial emissions. Our study also show that the sharp reduction in atmospheric CO2 during lockdown were short-lived, and returned to normal levels within months after lockdown measures were lifted