Abstract Bulk aerosol samples were collected from 16 July 2008 to 26 July 2009 at Lulang, a high‐altitude (>3300m above sea level) site on the southeast Tibetan Plateau (TP); objectives were to determine chemical characteristics of the aerosol and identify its major sources. We report aerosol (total suspended particulate, TSP) mass levels and the concentrations of selected elements, carbonaceous species, and water‐soluble inorganic ions. Significant buildup of aerosol mass and chemical species (organic carbon, element carbon, nitrate, and sulfate) occurred during the premonsoon, while lower concentrations were observed during the monsoon. Seasonal variations in aerosol and chemical species were driven by precipitation scavenging and atmospheric circulation. Two kinds of high‐aerosol episodes were observed: one was enriched with dust indicators (Fe and Ca 2+ ), and the other was enhanced with organic and elemental carbon (OC and EC), SO 4 2− , NO 3 − , and Fe. The TSP loadings during the latter were 3 to 6 times those on normal days. The greatest aerosol optical depths (National Centers for Environmental Protection/National Center for Atmospheric Research reanalysis) occurred upwind, in eastern India and Bangladesh, and trajectory analysis indicates that air pollutants were transported from the southwest. Northwesterly winds brought high levels of natural emissions (Fe, Ca 2+ ) and low levels of pollutants (SO 4 2− , NO 3 − , K + , and EC); this was consistent with high aerosol optical depths over the western deserts and Gobi. Our work provides evidence that both geological and pollution aerosols from surrounding regions impact the aerosol population of the TP.
Abstract The concept of the “Anthropocene” was first proposed in the early 21 st century and aroused widespread discussion in the public and geological community; however it still requires formal definition. The Global Boundary Stratotype Section and Point (GSSP) is a key tool in this process. Accurate chronology and high-resolution samples are the material basis for studying the Anthropocene. The varved sediment, deposited in Sihailongwan Maar Lake (42°17′N, 126°36′E) in northeast China, is a GSSP candidate site and a new location for studying the Anthropocene as a new stratigraphic unit. Anthropocene strata are the top few centimeters of sediment and characterized by small thickness, high water content, and lack of compaction and consolidation, which is physically different from older strata and requires special sampling and processing methods. There is currently a lack of standard and normative sampling and sample processing methods. Therefore, we propose a new paradigm specifically for the precise study of the top 20 cm of loose sediments. To avoid disturbing and disrupting the deposition sequence and structure of the sediments, freezing techniques and cryogenics were applied in coring and core processing. A freeze corer was used to collect the varved sediments in situ. To eliminate the effect of high water-content on X-ray fluorescence core scanning, core strips were freeze-dried and impregnated with resin prior to scanning. By cross-varve dating between parallel cores, we established a precise chronology with an annual resolution, and the age uncertainty was nearly eliminated. The top 20-cm long core represents approximately the last 210 years of deposition. At present, the early 1950s is recommended as the onset of the Anthropocene, the corresponding depth in 1950 CE was between 85-95 cm in our parallel cores. To obtain samples with high temporal resolution for proxy analyses, the cores were subsampled along the varve direction at 1 or 2 mm intervals with a scalpel knife in a -10 °C room, which represents an average of ~2 years. For loose Anthropocene sediments, freeze coring, freeze subsampling, and cross-dating are key for ensuring research accuracy.
Event stratigraphy is used to help characterise the Anthropocene as a chronostratigraphic concept, based on analogous deep-time events, for which we provide a novel categorization. Events in stratigraphy are distinct from extensive, time-transgressive 'episodes' – such as the global, highly diachronous record of anthropogenic change, termed here an Anthropogenic Modification Episode (AME). Nested within the AME are many geologically correlatable events, the most notable being those of the Great Acceleration Event Array (GAEA). This isochronous array of anthropogenic signals represents brief, unique events evident in geological deposits, e.g.: onset of the radionuclide 'bomb-spike'; appearance of novel organic chemicals and fuel ash particles; marked changes in patterns of sedimentary deposition, heavy metal contents and carbon/nitrogen isotopic ratios; and ecosystem changes leaving a global fossil record; all around the mid-20th century. The GAEA reflects a fundamental transition of the Earth System to a new state in which many parameters now lie beyond the range of Holocene variability. Globally near-instantaneous events can provide robust primary guides for chronostratigraphic boundaries. Given the intensity, magnitude, planetary significance and global isochroneity of the GAEA, it provides a suitable level for recognition of the base of the Anthropocene as a series/epoch.
Open biomass burning is a significant source of trace gases and particulate pollutants on a global scale and plays an important role in both atmospheric chemistry and climate change. To study the emission characteristics of biomass burning, with a focus on crop residue combustion in Northwest China, a combustion chamber was established. This paper describes the design, structure, and operating principles of the chamber. A series of evaluation tests were conducted, demonstrating its applicability in emission studies. The combustion chamber was equipped with a thermoanemometer and a dilution sampler as well as multiple sampling ports for interfacing with different monitors. A case study of wheat straw combustion was performed to demonstrate reproducibility and comparability of the derived emission factors with prior studies. The combustion chamber may be applied to develop emission factors to update emission inventories and source profiles for improving source apportionment.
The impacts of anthropogenic emissions on the reduction of source-specific equivalent black carbon (eBC) aerosol and their direct radiative effects (DREs) were investigated during the lockdown of coronavirus outbreak in a megacity of China in 2020. Five eBC sources were identified by a newly developed hybrid environmental receptor model. Results showed that biomass burning, traffic-related emissions, and coal combustion were the dominant contributors to eBC. The generalized addictive model indicated that the reduction of traffic-related eBC during the lockdown was entirely attributed to the decrease of emission. The decreased biomass-burning activities and favorable meteorological factors are both important drivers for the biomass-burning eBC reduction during the lockdown. A radiative transfer model showed that the eBC DRE efficiency of biomass burning was the strongest, followed by coal combustion and traffic-related emissions. This study highlights that aggressive reduction in the consumption of residential solid fuels would be effective on climate change mitigation.
Using a well drained paddy soil and the derived soil under vegetables in the Taihu Lake region, China, experiments of soil capillary rise, colloid dispersion and adsorption of toxic organics and heavy metals by soil under various degrees of LAS addition were conducted. Also incubation experiments of microorganism activity in soil with added LAS in different concentrations were carried out in laboratory. LAS addition resulted in lower capillary rise of soil solution, higher dispersion of soil colloids and lower capacity of soil for organic pollutants but no significant influence on adsorption of heavy metal cations. The nitrification and amonification in soil were very sensitive to LAS stress while denitrification turned to be stimulated. LAS addition gave stronger growth of soil bacteria while decreased growth of fungus. Meanwhile, soil respiration was stimulated in the first week of incubation and compressed afterwards by LAS at concentration over 5 mg/kg. It seemed that some species of microorganisms were tolerant of LAS in the studied soils.
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