Institute of Earth Environment
Institutional Repository of Institute of Earth Environment, CASNot a member yet
7120 research outputs found
Sort by
East Asian summer monsoon changes in subtropical China since late Pleistocene: Evidence from the Ailuropoda-Stegodon fauna
No full textPrevious studies on the amplitude of East Asian summer monsoon (EASM) changes mainly focused on northern China (represented by the Loess Plateau). However, a rare investigation centered on the subtropical zone of southern China, where the important route for EASM moved northward or southward, especially addressing a lack of the research on mammals. The Ailuropoda-Stegodon fauna is a representative mammal fauna in southern China since the late Pleistocene. It indicates the southern mid-subtropical-tropical forest environment with tropical climate characteristics, and its southward or northward movements in the subtropical zone imply the changes of EASM intensity. Based on previous research, combined with the species characteristics and distribution range of the Ailuropoda-Stegodon fauna with tropical animals during the marine isotope stage 5 (MIS5), MIS3, MIS2, and MIS1 Megathermal periods, this paper mainly investigates its evolution and the fluctuations of EASM. The conclusions include: (1) The distribution geometric centers in the MIS5, MIS3, MIS2, and MIS1 Megathermal periods are (26 degrees 14 ' N, 111 degrees 22 ' E), (24 degrees 35 ' N, 107 degrees 30 ' E), (22 degrees 48 ' N, 112 degrees 01 ' E), and (26 degrees 19 ' N, 112 degrees 25 ' E), respectively. (2) Compared with the MIS5 period, the EASM of the MIS3 and MIS2 moved 180 km and 380 km southwards, and that of the MIS1 Megathermal period moved about 10 km northwards. The EASM movement indicated by the fauna migration happened synchronous with the climate records of stalagmites in subtropical China, the sporopollen from eastern China, and oxygen isotopes from Sulu Sea. They also correspond to the peaks and valleys of the total solar radiation at 35 degrees N in the winter half-year. This suggests that the migrations of the Ailuropoda-Stegodon fauna are consistent with the changes of the global climate, and the driving force is mainly from the changes of total solar radiation at 35 degrees N in the winter half-year
Cropland nitrogen dioxide emissions and effects on the ozone pollution in the North China plain
No full textSoil nitrogen dioxide (NOX = NO2 + NO) emissions have been measured and estimated to be the second most significant contributor to the NOX burden following the fossil fuel combustion source globally. NOX emissions from croplands are subject to being underestimated or overlooked in air pollution simulations of regional atmospheric chemistry models. With constraints of ground and space observations of NO2, the WRF-Chem model is used to investigate the cropland NOX emission and its contribution to the near-surface ozone (O-3) pollution in North China Plain (NCP) during a growing season as a case study. Model simulations have revealed that the cropland NOX emissions are underestimated by around 80% without constraints of satellite measured NO2 column densities. The biogenic NOX source is estimated to account for half of the anthropogenic NOX emissions in the NCP during the growing season. Additionally, the cropland NOX source contributes around 5.0% of the maximum daily average 8h O-3 concentration and 27.7% of NO2 concentration in the NCP. Our results suggest the agriculture NOX emission exerts non-negligible impacts on the summertime air quality and needs to be considered when designing emission abatement strategies
Ancient DNA and deep population structure in sub-Saharan African foragers
No full textMultiple lines of genetic and archaeological evidence suggest that there were major demographic changes in the terminal Late Pleistocene epoch and early Holocene epoch of sub-Saharan Africa(1-4). Inferences about this period are challenging to make because demographic shifts in the past 5,000 years have obscured the structures of more ancient populations(3,5). Here we present genome-wide ancient DNA data for six individuals from eastern and south-central Africa spanning the past approximately 18,000 years (doubling the time depth of sub-Saharan African ancient DNA), increase the data quality for 15 previously published ancient individuals and analyse these alongside data from 13 other published ancient individuals. The ancestry of the individuals in our study area can be modelled as a geographically structured mixture of three highly divergent source populations, probably reflecting Pleistocene interactions around 80-20 thousand years ago, including deeply diverged eastern and southern African lineages, plus a previously unappreciated ubiquitous distribution of ancestry that occurs in highest proportion today in central African rainforest hunter-gatherers. Once established, this structure remained highly stable, with limited long-range gene flow. These results provide a new line of genetic evidence in support of hypotheses that have emerged from archaeological analyses but remain contested, suggesting increasing regionalization at the end of the Pleistocene epoch.
DNA analysis of 6 individuals from eastern and south-central Africa spanning the past approximately 18,000 years, and of 28 previously published ancient individuals, provides genetic evidence supporting hypotheses of increasing regionalization at the end of the Pleistocene
Lake eutrophication in northeast China induced by the recession of the East Asian summer monsoon
No full textLakes are one of the most important freshwater resources on Earth and they provide a wide range of ecosystem services. However, due to rapid economic development and the intensification of human activities, many lakes have become eutrophic, which may threaten their status as water resources. Human activities have played a significant role in lake eutrophication, but whether this role is independent of, or coupled with, natural climate change requires further study. We selected Dali Lake, a large lake affected by human activity within the ancient warfare borders, to clarify the ecological response of a lake to climate change and human activity. We used analyses of sedimentary n-alkanes and AMS C-14 dating to reconstruct the paleolimnological evolution of Dali Lake since 15 cal kyr BP, and specifically to assess the timing and causes of eutrophication. The results show that the short-chain n-alkanes (C17-19-alkanes) in Dali Lake are mainly produced by bacteria and algae within the lake, and that the sedimentary absolute abundance of short-chain n-alkanes (A(17-19)-alkanes) can be used as a proxy for assessing the ecological status of the lake. The ecological status of Dali Lake was the most stable during the early to middle Holocene, when the East Asian summer monsoon was strong, but bacterial and algal outbreaks occurred during three episodes of a weakened summer monsoon-the Older Dryas, Younger Dryas, and the Common Era-when the lake experienced different degrees of eutrophication. During the recession of the East Asian summer monsoon, the weakening of precipitation recharge of the lake led to a reduction in lake area and an increase in nutrient concentrations in the lake water, while aeolian dust input was an additional nutrient source, leading to bacterial and algal outbreaks. During the Common Era, lake eutrophication occurred in the context of both summer monsoon recession and enhanced human activities, but their combined effects did not lead to more intense lake eutrophication than was caused by monsoon recession during the Younger Dryas. We conclude that, although human activities have enhanced the eutrophication of Dali Lake, the reduction in lake size due to monsoon recession and the resulting increase in the salinity and nutrient concentration of the lake water, combined with increased aeolian inputs, were a more important trigger of lake eutrophication. (C) 2022 Elsevier Ltd. All rights reserved
Phyto-mediated photocatalysis: a critical review of in-depth base to reactive radical generation for erythromycin degradation
No full textErythromycin (ERY), designated as a risk-prioritized macrolide antibiotic on the 2015 European Union watch list, is the third most commonly used antibiotic, most likely due to its ability to inhibit the protein. ERY has revealed record-high aquatic concentrations threatening the entire ecosystem and hence demands priority remedial measures. The inefficiency of various conventional ERY degradation methodologies opened up a gateway to advanced technologies. The conventional approach comprising of a chemically formulated, single photocatalyst has a major drawback of creating multiple environmental stresses. In this context, photocatalysis is grabbing tremendous attention as an efficient and cost-effective antibiotic treatment approach. Several studies have ascertained that ZnO, TiO2, Fe3O4, and rGO nanoparticles possess remarkable pollution minimizing operational capabilities. Additionally, composites are found much more effective in antibiotic removal than single nanoparticles. In this review, an attempt has been made to provide a comprehensive baseline for efficient reactive radical production by a phyto-mediated composite kept under a certain source of irradiation. Considerable efforts have been directed towards the in-depth investigation of rGO-embedded, phyto-mediated ZnO/TiO2/Fe3O4 photocatalyst fabrication for efficient ERY degradation, undergoing green photocatalysis. This detailed review provides photocatalytic nanocomposite individualities along with a hypothetical ERY degradation mechanism. It is assumed that derived information presented here will provoke innovative ideas for water purification incorporating green photocatalysis, initiating the construction of high-performance biogenic hierarchical nanocatalysts
Millennial and centennial CO2 release from the Southern Ocean during the last deglaciation
No full textFor its greenhouse effects, atmospheric CO2 can critically influence the global climate on millennial and centennial timescales. Pleistocene atmospheric CO2 variations must involve changes in ocean storage of carbon, but the mechanisms and pathways of carbon transfer between the oceanic and atmospheric reservoirs are poorly understood due, in part, to complications associated with interpretation of carbonate system proxy data. Here we employ a recently developed approach to reconstruct upper Atlantic air-sea CO2 exchange signatures through the last deglaciation. Using this approach, proxy and model data each suggest that there was a net release of CO2 via the Atlantic sector of the Southern Ocean during the early deglaciation, which probably contributed to the millennial-scale atmospheric CO2 rise during Heinrich Stadial 1 at similar to 18.0-14.7 kyr ago. Moreover, our data reveal a previously unrecognized mechanism for the centennial-scale atmospheric CO2 rise at the onset of the Bolling warming event around 14.7 kyr ago, namely, the expansion of Antarctic Intermediate Water, a water mass that is especially inefficient at sequestering atmospheric CO2. Our findings highlight the role of the Southern Ocean outgassing and intermediate water-mass production and volume variations in governing millennial- and centennial-timescale atmospheric CO2 rises during the last deglaciation
Characterization of PM2.5-bound parent and oxygenated PAHs in three cities under the implementation of Clean Air Action in Northern China
No full textAmbient polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (oPAHs) could act as carcinogenic substances and cause severe health outcome on human beings through inhalation exposure. To protect human health, China government implemented strict control actions (Air Pollution Prevention and Control Action Plan, APPC) to reduce air pollutants emission. Notable achievement of PM2.5 pollution reduction was reported in several studies, while the pollution characteristics of non-routine monitoring PAHs and oPAHs under the impact of APCC were poorly understood. In this study, daily PM2.5 samples in three Chinese cites (Xingtai, Liaocheng, and Heze) were collected for one month in four seasons form 2018-2019 and determined for the PM2.5-bound PAHs and oPAHs. The results showed that the annual PAHs and oPAHs were 58.3 & PLUSMN; 86.1 and 62.7 & PLUSMN; 75.2 ng/m(3) in Xingtai, 36.2 & PLUSMN; 55.6 and 35.9 & PLUSMN; 28.3 ng/m(3) in Liaocheng, and 24.5 & PLUSMN; 37.7 and 35.1 & PLUSMN; 24.7 ng/m(3)& nbsp;in Heze, respectively, suggesting that the PAHs pollution in the measured cities was still considerable and more solid control measures are needed. Significant variations in seasonal concentrations were observed in all the cities with the highest occurring in winter, which is mainly due to solid fuel burning for house heating. Meanwhile, composition profiles of PAHs and oPAHs also showed significant seasonal variations due to the source differences in different seasons. The results of PMF model showed both vehicle exhausts emission and solid fuels burning dominated the PAHs pollution. In summer, vehicles were the major contributor to the total PAHs pollution, while in winter, the contribution of coal combustion emission increased sharply. The correlations analysis between PAHs (oPAHs) and K+ and hopanes also showed a stronger impact of coal combustion in winter time. The result of this study confirmed the goal of clean air in China was calling for continuous actions
Sea spray as an obscured source for marine cloud nuclei
No full textSea spray aerosols (SSAs) make up a substantial proportion of aerosols in the global atmosphere and, especially when considering marine haze and cloud layers, can have a large impact on cloud formation and atmospheric radiative balance. Although SSA has the highest cloud condensation nuclei (CCN) activation potential, the majority of its population, residing in sub-micrometre sizes, are often obscured by non-sea-spray CCN. Quantification of SSA-derived CCN is fundamental in understanding the radiative budget. Recent approaches to estimate the sub-micrometre SSA employed a free-monomodal lognormal analysis that depicts the global oceanic CCN population comprising less than 30% SSA. Here we derive SSA distributions from a unique five-year dataset of aerosol microphysics and hygroscopicity (water uptake ability) over Atlantic waters. This approach utilizes the distinctive ultra-high hygroscopicity signature of inorganic sea salt and is able to identify the sub-micrometre sea spray down to 35 nm diameter with high time and size resolution. In stark contrast to previous studies, the hygroscopicity coupled multimodal fitting analysis yields SSA-derived CCN as much as 500% in excess of estimates produced using the free-monomodal approach. Our results suggest the contribution of SSA to global CCN, particularly Aitken mode SSA, has probably been overlooked
<p>Worsening summertime ozone pollution in the Guanzhong Basin, China from 2014 to 2018: Impacts of synoptic conditions and anthropogenic emissions</p>
No full textThe ozone (O-3) pollution in the Guanzhong Basin (GZB), China has progressively deteriorated from 2014 to 2018, with the summertime near-surface maximum daily 8 h average (MDA8) O-3 concentration ([O-3]) increasing from about 104 to 141 mu g m(-3), although the emission mitigation strategies have been carried out since 2013. However, it remains elusive about whether anthropogenic emissions or meteorological conditions contribute to the worsening of O-3 pollution in the GZB. A subjective classification method is first used to classify the synoptic patterns influencing the GZB into favorable and unfavorable conditions. The unfavorable synoptic conditions generally correspond to less precipitation, more solar radiation and higher near-surface temperature, which facilitate formation of the O-3 pollution, and it is opposite for the favorable conditions. The increasing trend of MDA8 [O-3] is correlated well with the increase in occurrence of unfavorable synoptic conditions and near-surface temperature from 2014 to 2018. Sensitivity experiments using the WRF-Chem model reveals that the emission mitigation strategies from 2014 to 2018 enhance MDA8 [O-3] by 19.2% on average in the GZB, which counts about 54% of the observed MDA8 O-3 increasing trend. Particularly, the particulate matter decrease due to the emission mitigation contributes about 11.5% of the observed trend, caused by the reduced HO2 heterogeneous uptake and enhanced photolysis. The rest 46% of the observed MDA8 O-3 increasing trend can be mainly contributed by the variation of occurrence days of unfavorable synoptic situations
Diurnal Variations of Isoprene, Monoterpenes, and Toluene Oxidation Products in Aerosols at a Rural Site of Guanzhong Plain, Northwest China
No full textIn this study, the characteristics and formation mechanism of summertime isoprene, monoterpene, and toluene-derived secondary organic aerosols (SOAs) were investigated in a rural area of Guanzhong Plain, Northwest China. The variations in key indicators of primary sources indicated a significant influence of biomass burning on PM2.5 during the observation period. The concentrations of total measured SOA tracers from isoprene, monoterpene, and toluene were 40.85 +/- 17.31, 24.27 +/- 7.50, and 10.61 +/- 0.33 ng/m(3), respectively. The average ratio of cis-pinonic and pinic acids to 3-Methyl-1,2,3-butanetricarboxylic acid (MBTCA)(P/M) were 0.45 and 0.85 by day and by night, respectively. The low ratio in the daytime was mainly due to the stronger photo-degradation and particle-to-gas distribution of semi-volatile cis-pinonic and pinic acids. The monoterpene SOA tracers were significantly correlated with levoglucosan at night (R-2 = 0.51, p 0.67, p < 0.01), indicating the significant contribution of biomass combustion to these SOAs. The mass concentration of isoprene-, monoterpenes-, and toluene-derived SOC was estimated by using the tracer yield method. The total calculated SOCs by day and by night were 0.25-0.71 (average: 0.46) and 0.26-0.78 (average: 0.42) mu gC/m(3), accounting for 3.35-10.58% and 3.87-13.51% of OC by day and by night, respectively