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Oldest Dryas hydroclimate reorganization in the eastern Iberian Peninsula after the iceberg discharges of Heinrich Event 1
No full textThis study examines the first precisely dated and temporally highly resolved speleothem record from Iberia that reconstructs the Oldest Dryas (OD). The onset of cold conditions in the study area, contemporary with the beginning of Heinrich Stadial 1, is recorded at 18.13 +/- 0.08 ka, with a pronounced drop of 6.1 parts per thousand in delta C-13 in 250 years. Henceforth, stadial conditions depict a period of instability in the Atlantic Meridional Overturning Circulation, peaking in freshwater input from iceberg melting during Heinrich Event 1. Anomalies in the delta O-18 of the stalagmite attributed to such a freshwater event are found from 16.17 to 15.89 ka. Such absolute dates given to the onset of the OD in Iberia and to the main iceberg discharges are reliable anchor points for non-absolute chronologies. Two periods are identified in the OD: OD-a (18.13-16.17 ka) is characterized by wet conditions and a faster growth rate, and OD-b (15.89-14.81 ka) exhibits relative dryness and a slower growth rate. The sudden release of fresh water is considered to be the reason for the disruption of rainfall patterns in eastern Iberia. The present study also highlights the existence of heterogeneous and complex hydrological conditions during the OD in Iberia when both Atlantic and Mediterranean realms are considered
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
Global Impact of ENSO on Dust Activities with Emphasis on the Key Region from the Arabian Peninsula to Central Asia
No full textThe El Nino-Southern Oscillation (ENSO) has been found to be closely related to dust aerosol activities in many parts of the world. However, previous studies have rarely explored the ENSO's impacts in the global context. In this study, the responses of the interannual variability of global atmospheric dust content to the ENSO cycle (including the eastern Pacific and central Pacific types) are examined using the MERRA-2 atmospheric aerosol reanalysis data. The ENSO-related tropical eastern Pacific sea surface temperature (SST) anomalies in the antecedent winter (November to January) have the most significant effect on the airborne dust content in a region from the Arabian Peninsula to Central Asia during the following spring and summer (April to July), which is identified as the key region (KR) of the ENSO's impacts. The positive (negative) tropical eastern Pacific SST anomalies in the preceding winter during the El Nino (La Nina) years correspond to significantly reduced (increased) dust column content in the following spring and summer over the KR, which was confirmed using singular value decomposition. With the above (below)-normal winter SST anomalies in the tropical eastern Pacific, the Walker Circulation weakens (strengthens), and the divergence (convergence) over the western tropical Pacific and the convergence (divergence) over the southern tropical Indian Ocean in the lower troposphere are strengthened, which facilitate (restrain) the southward diffusion of airborne dust in the KR. Meanwhile, the increased (decreased) precipitation and soil moisture and the corresponding vegetation conditions help limit (promote) the dust emission in the KR during the El Nino (La Nina) years
Landscape response to normal fault linkage: Insights from numerical modeling
No full textNormal fault linkage has significant impacts on uplift patterns and erosional processes in extensional regions. However, geomorphic process-based constraints on landscape response to normal fault linkage are still scarce. Here, we use landscape evolution models to examine how a landscape responds to the linkage of two normal faults. The results demonstrate that topography dynamically responds to the changes in uplift patterns that accompany fault linkage. Specifically, our results indicate that after fault linkage, (1) the steepest topography and the highest erosion rate shift from the center of each fault segment to the linkage zone; and (2) the main drainage divide evolves from an M-shape to a bow-shape. We apply these findings to the Langshan Mountains in northern China, and suggest that the two piedmont fault segments have linked and that a high geohazard risk exists near the linkage zone, where the steep, transient topography is experiencing intense erosion. (C) 2021 Elsevier B.V. All rights reserved
The impact of aerosol size-dependent hygroscopicity and mixing state on the cloud condensation nuclei potential over the north-east Atlantic
No full textWe present an aerosol cloud condensation nuclei (CCN) closure study over the north-east Atlantic Ocean using six approximating methods. The CCN number concentrations (N-CCN) were measured at four discrete supersaturations (SSs; 0.25 %, 0.5 %, 0.75% and 1.0 %). Concurrently, aerosol number size distribution, sub-saturation hygroscopic growth factor and bulk PM1 chemical composition were obtained at matching time resolution and after a careful data validation exercise. Method A used a constant bulk hygroscopicity parameter kappa of 0.3; method B used bulk PM1 chemical composition measured by an aerosol mass spectrometer (AMS); method C utilised a single growth factor (GF) size (165 nm) measured by a humidified tandem differential mobility analyser (HTDMA); method D utilised size-dependent GFs measured at 35, 50, 75, 110 and 165 nm; method E divided the aerosol population into three hygroscopicity modes (near-hydrophobic, more-hygroscopic and sea-salt modes), and the total CCN number in each mode was cumulatively added up; method F used the full-size-scale GF probability density function (GF-PDF) in the most complex approach. The studied periods included high-biological-activity and low-biological-activity seasons in clean marine and polluted continental air masses to represent and discuss the most contrasting aerosol populations. Overall, a good agreement was found between estimated and measured NCCN with linear regression slopes ranging from 0.64 to 1.6. The temporal variability was captured very well, with Pearson's R value ranging from 0.76 to 0.98 depending on the method and air mass type. We further compared the results of using different methods to quantify the impact of size-dependent hygroscopicity and mixing state and found that ignoring size-dependent hygroscopicity induced overestimation of N-CCN by up to 12 %, and ignoring a mixing state induced overestimation of NCCN by up to 15 %. The error induced by assuming an internal mixing in highly polluted cases was largely eliminated by dividing the full GF-PDF into three conventional hygroscopic modes, while assuming an internal mixing in clean marine aerosol did not induce significant error
Environmental and health risks of VOCs in the longest inner-city tunnel in Xi & rsquo;an, Northwest China: Implication of impact from new energy vehicles
No full textTraffic source-dominated volatile organic compound (VOC) samples were collected during four time-intervals in a day (I: 7:30-10:30, II: 11:00-14:0 0, III: 16:30-19:30, and IV: 20:00-23:0 0) in a tunnel in summer, 2019, in Xi & rsquo;an, China. The total measured VOC (TVOC) in periods I and III (rush hours, 107.2 +/- 8.2 parts per billion by volume [ppbv]) was 1.8 times that in periods II and IV (non-rush hours, 58.6 +/- 13.8 ppbv), consistent with the variation in vehicle numbers in the tunnel. The considerably elevated ethane and ethylbenzene levels could have been attributed to emissions from compressed natural gas vehicles and the rapid development of methanol-fueled taxis in Xi & rsquo;an in 2019. The mixing ratios of benzene, toluene, ethylbenzene, and xylenes (BTEX) contributed 9.4%-12.7% to TVOCs, and the contributions were nearly 40% higher in periods I and III than in II and IV, indicating that BTEX levels were strongly affected by vehicle emissions. The indicators of motor vehicle emission, namely ethylene, propylene, toluene, m/p-xylenes, o-xylene, and propane, contributed to more than half of the ozone formation potential in this study. The noncarcinogenic risks of VOCs in this study were within the in-ternational safety standard, whereas the carcinogenic risks exceeded the standard by 2.3-4.6 times, suggesting that carcinogenic risks were more serious than noncarcinogenic risks. VOCs presented 2.2 and 1.4 times noncarcinogenic and carcinogenic risks during rush hours than during non-rush hours, respectively. Notably, the carcinogenic risk in period IV was comparable with that in period III; however, the vehicle numbers and VOC mixing ratios were the lowest at night, which may have attributed to the increasing number and proportion of methanol M100-fueled vehicles in the tunnel. Therefore, VOCs emitted by new energy vehicles should also be seriously considered while evaluating fossil fuel vehicle emissions.
(c) 2021 Elsevier Ltd. All rights reserved
Strengthening Influence of El Nino on the Following Spring Precipitation over the Indochina Peninsula
No full textSignificance Statement Spring precipitation variation has profound economic and societal influences for the Indochina Peninsula (ICP) that consists of several agriculture-based countries. Moreover, the local soil moisture anomaly induced by the ICP spring precipitation is an important seasonal predictor for the East Asian summer monsoon and extreme climate. Here this study identifies a strengthening influence of El Nino on the following spring precipitation over the ICP, due to a relatively stronger intensity and longer duration of the El Nino-related warm SST anomalies over the tropical central Pacific since the early 1990s. This may provide an important implication for the seasonal predictions of summer monsoon and extreme climate over East Asia and thus potentially enhance the predictability of regional climate.
El Nino is a dominant source of interannual climate variability around the world. Based on the observed and reanalyzed datasets for the period of 1958-2019, this study explores the influence of El Nino on the spring precipitation over the Indochina Peninsula (ICP). The results show that El Nino has a significant negative correlation with the following spring precipitation over the ICP. However, this climatic teleconnection of El Nino was unstable, with an obvious interdecadal strengthening since the early 1990s. During the decaying spring, the El Nino-related sea surface temperature (SST) anomalies would induce an abnormal downward motion along with an anomalous low-level anticyclone over the western North Pacific. Before the early 1990s, such El Nino-induced atmospheric circulation anomalies were located to the east of the ICP, exerting little influence on the spring ICP precipitation. In contrast, since the early 1990s, the abnormal downward motion and anomalous low-level anticyclone extended westward covering the whole ICP, hampering local spring precipitation. This interdecadal change is owing to a relatively stronger intensity and longer duration of the El Nino-related warm SST anomalies over the tropical central Pacific in the epoch after the early 1990s (1992-2019) than in the previous decades (1958-91). Our findings highlight a strengthening effect of El Nino on the following spring climate over the ICP since the early 1990s, which has great implications for the regional climate prediction
Identification of nitrate sources in the Jing River using dual stable isotopes, Northwest China
No full textNitrate (NO3-) contamination has become a dominant international problem in the aquatic environment, so identifying the sources and transformations of NO3- is the basis for improving water quality. Since the Jing River is the largest tributary of the Wei River, to understand its water quality, this study collected surface water samples from the Shaanxi section of the Jing River during the dry season. The potential sources of NO3- were analyzed by hydrochemical and bi-isotopic methods, and the SIAR model was used to estimate the proportional contribution of each source. Results indicated that NO3--N was the main form of inorganic nitrogen in this area, and the average total nitrogen content was 10.23 mg center dot L-1, which showed that nitrogen pollution was highly serious; the transformation process of nitrogen in this study area was mainly nitrification; The results of Bayesian model showed that manure and sewage contributed to the most NO3- (64.39%) in the dry season, followed by soil nitrogen, which was 26.35%. These results help to adopt better nitrogen management measures to meet the national environmental quality standards for surface water
Clumped isotopic compositions of cultured and natural land-snail shells and their implications
No full textLand snails are widely distributed animals whose clumped isotope (Delta(47)) in shell carbonates can serve as a proxy for temperature in terrestrial environments. However, it is unclear whether the Delta(47) values of snail shells are affected by biological processes known as "vital effects." Here, we report Delta(47) values of whole Achatina fulica snail shells cultured at different temperatures at different growth ages (samples collected monthly). In general, the mean Delta(47) values of the snail shells decrease with higher cultivation temperature, which indicates they have potential use in reconstructing temperature changes. However, the mean reconstructed Delta(47) temperatures (T-47) using the calibrations from Petersen et al. (2019), Bonifacie et al. (2017), and Kelson et al. (2017) are similar to 6 degrees C higher than the actual growth temperatures. Interestingly, this overestimation in T-47 disappears when applying Zhai et al.'s (2019) calibration for the Bradybaena snail. This calibration also yields good agreement between the T-47 data of all field-collected snails and their growing season temperatures. The above-mentioned phenomenon indicates the existence of the vital effect in land-snail shells. The variations in Delta(47) with snail age and the correlations between Delta(47), delta O-18, and delta C-13 values also indicate the potential influence of vital effects. Finally, we suggest that the vital effect may be explained by kinetic fractionation through CO2 degassing associated with dehydration/dehydroxylation during the formation of snail shells