Freshwater radiocarbon reservoir age in the lower Yellow River floodplain during the late Holocene

The radiocarbon concentration of the dissolved inorganic carbon (DIC) pool of most freshwater bodies such as lakes and rivers tends to be depleted with respect to that of the contemporaneous atmosphere, resulting in an apparent radiocarbon age of inorganic carbon therein known as freshwater reservoir effect. This phenomenon of radiocarbon age offset is usually site specific and varies over time. By radiocarbon dating pairs of twigs and gastropod shells preserved in an ancient lake, as well as gastropod shells in pre-bomb flooding sediments of known age, we are able to determine the freshwater radiocarbon reservoir effect in the lower Yellow River floodplain during the late Holocene. The regional freshwater radiocarbon reservoir age ranges from 1081 to 233 years with an average of 575 +/- 317 years, slightly older than that obtained from Lake Dongping by radiocarbon dating of live submerged aquatic plants. Our results show that the freshwater radiocarbon reservoir age is much older than its marine counterpart of the Yellow Sea and Bohai Bay. A source inversion using dual carbon isotopes (i.e. C-14 and C-13) and a linear mixing model revealed that the DIC in the surface water bodies was mainly from shallow groundwater and the Yellow River. Our results have broad relevance to the geological and archaeological chronologies based on the radiocarbon method for this area

A CAVEAT ON RADIOCARBON DATING OF ORGANIC- POOR BULK LACUSTRINE SEDIMENTS IN ARID CHINA

Characterized by a dry climate, the arid area of China represents a unique landscape. A proper understanding of the driving mechanisms behind the changes of this ecologically vulnerable landscape requires placing the instrumental records within a geological context. Lakes in this area bear rich information about past climatic and environmental changes presumably regulated by the westerlies at various timescales. The lacustrine records obtained in this area heavily rely on radiocarbon ages, which are usually subject to the temporal and spatial variability of the C-14 reservoir effect. Yet, little is known about the C-14 reservoir age of lacustrine systems in this area. This study reports an anomalously large C-14 reservoir age of about 11,000 +/- 2000 yr from a saline lake in NW China by comparing C-14 and OSL chronologies. The modeling study suggests that this age offset appears to be an inherent phenomenon in lacustrine systems, which mainly arises from the introduction of pre- aged organic matter from the catchment and the conversion of C-14-depleted dissolved inorganic carbon to organic matter by photosynthesis. Compared to the large age offset induced by the C-14-deficient exogenous carbon, the reservoir effect due to retention of organic matter in the lake water appears to be inconsequential. The results reveal the pitfall of C-14 dating on organic-poor bulk lacustrine sediments in this barren landscape, and thus highlight the need for alternate dating methods to constrain the chronology of lacustrine records.</p

Changes in Air Quality from the COVID to the Post-COVID Era in the Beijing-Tianjin-Tangshan Region in China

This article discussed air quality changes in the Beijing-Tianjin-Tangshan (BTT) region. The air quality index (AQI) values, and the concentrations of PM2.5, PM10, SO2, CO, NO2, and O-3 in the BTT region during the COVID-19 outbreak in 2020 were, respectively, 79.4, 47.2 mu g m(-3), 73.4 mu g m(-3), 10.3 mu g m(-3), 0.87 mg m(-3), 33.6 mu g m(-3), and 90.7 mu g m(-3). However, they were, respectively, 102.7, 61.4 mu g m(-3), 121.0 mu g m(-3), 9.0 mu g m(-3), 0.88 mg m(-3), 40.1 mu g m(-3), and 84.0 mu g m(-3) during the same period in 2021, which is an increase of 29.2%, 30.1%, 64.8%, -12.9%, 1.94 %, 19.5%, and -7.4% compared with the values in 2020. The combined proportions of grade I and grade II during the COVID-19 outbreak in 2020 were 16.7% higher than those in the same period in 2021, so the air quality has deteriorated rapidly from 2020 to the post-COVID era in 2021. The possible reasons for poorer air quality are that the frequency of dusty weather and air pollutant discharge has increased, and meteorological conditions have been relatively unfavorable. The average AQI values, and concentrations of PM2.5, PM10, SO2, CO, NO2, and O-3 during the post-COVID period in 2021 respectively decreased by 14.8%, 29.0%, 14.6%, 22.5%, 37.4%, 14.8%, and 8.7%, compared with those in 2020. It is also worth noting that all the changes in air pollution during the post-COVID era have been consistent. The combined proportions of grade I and grade II during post-COVID period in 2021 were 18.4% higher than those during the same period of 2020, which indicates that the air quality during post-COVID 2021 has obviously improved compared with those in the same period of 2020. The possible reasons are a series of clean air policies and clean air actions, as well as favorable atmospheric diffusion conditions. These results indicate that clean air policies play a very important role in improving air quality

Air Pollution Forecasting Using Artificial and Wavelet Neural Networks with Meteorological Conditions

Air quality forecasting is a significant method of protecting public health because it provides early warning of harmful air pollutants. In this study, we used correlation analysis and artificial neural networks (ANNs; including wavelet ANNs [WANNs]) to identify the linear and nonlinear associations, respectively, between the air pollution index (API) and meteorological variables in Xian and Lanzhou. Evaluating twelve algorithms and nineteen network topologies for the ANN and WANN models, we discovered that the optimal input variables for an API forecasting model were the APIs from the 3 preceding days and sixteen selected meteorological factors. Additionally, the API could be accurately predicted based solely on the value recorded 3 days earlier. Based on the correlation coefficients between the air pollution index of the targeted day and the tested variables, the API displayed the closest relationship with the API 1 day earlier as well as stronger correlations with the average temperature, average water vapor pressure, minimum temperature, maximum temperature, API 2 days earlier, and API 3 days earlier. When Bayesian regularization was applied as a training algorithm, the WANN and ANN models accurately reproduced the APIs in both Xian and Lanzhou, although the WANN model (R = 0.8846 for Xian and R = 0.8906 for Lanzhou) performed better than the ANN (R = 0.8037 for Xian and R = 0.7742 for Lanzhou) during the forecasting stage. These results demonstrate that WANNs are effective in short-term API forecasting because they can recognize historic patterns and thereby identify nonlinear relationships between the input and output variables. Thus, our study may provide a theoretical basis for environmental management policies

Intensified fire activity induced by aridification facilitated Late Miocene C4 plant expansion in the northeastern Tibetan Plateau, China

There have been a number of suggested driving factors for Late Miocene expansion of C4 plant coverage, including a decline in atmospheric CO2 concentrations, enhanced aridity and seasonality, shifts in fire regimes, and tectonic uplift. In order to identify and discriminate the driving factors of vegetation changes, continuous records from the same section or basin are required. We present micro-charcoal-based fire history and C4 vegetation abundance records spanning the Miocene from the Yanwan Section in the Tianshui Basin, on the northeastern Tibetan Plateau (NE TP). Based on statistical analyses, the micro-charcoal concentrations were relatively low before ~10Â Ma, and after that time, there was an exponential increase. The C4 plant abundance shows a strong increase after 8Â Ma, about 2 million years after the micro-charcoal concentrations started increasing. We compare our records with published CO2, pollen, seasonality, herbivorous mammalian fossil and tectonic records from the same section and basin. We find that C4 vegetation, fire intensities, and opening landscapes increased simultaneously after 8 Ma. This indicates that a fire-grassland feedback, initially driven by aridification, was the trigger for the Late Miocene expansion of C4 plants. We speculate that herbivorous mammalian species may also have played a minor role. During the Miocene, there is a trend towards enhanced seasonality and a decline in atmospheric CO2 concentrations, which were also necessary preconditions for the expansion

Molecular characteristics and stable carbon isotope compositions of dicarboxylic acids and related compounds in the urban atmosphere of the North China Plain: Implications for aqueous phase formation of SOA during the haze periods

In the past five years, Chinese government has promulgated stringent measures to mitigate air pollution. However, PM2.5 levels in the China North Plain (NCP), which is one of the regions with the heaviest air pollution in the world, are still far beyond the World Health Organization (WHO) standard. To improve our understanding on the sources and formation mechanisms of haze in the NCP, PM2.5 samples were collected during the winter of 2017 on a day/night basis at the urban site of Liaocheng, which is one of the most polluted cities in the NCP. The samples were determined for molecular distributions and stable carbon isotope compositions of dicarboxylic acids and their precursors (ketocarboxylic acids and alpha-dicarbonyls), levoglucosan, elemental carbon (EC), organic carbon (OC) and water-soluble organic carbon (WSOC). Our results showed that oxalic acid (C-2) is the dominant dicarboxylic acid, followed by succinic acid (C-4) and malonic acid (C-3), and glyoxylic acid (omega C-2) is the most abundant ketocarboxylic acids. Concentrations of C2, glyoxal (Gly) and methylglyoxal (mGly) presented robust correlations with levoglucosan, suggesting that biomass burning is a significant source of PM2.5 in the NCP. Moreover, C-2 and Gly and mGly linearly correlated with SO42-, relative humidity (RH), aerosol liquid water content (LWC) as well as particle in-situ pH (pH(is)), indicating that aqueous-phase oxidation is the major formation pathway of these SOA, and is driven by acid-catalyzed oxidation. Concentrations and relative abundances of secondary species including SNA (SO42, NO3 and NH4+), dicarboxylic acids, and aerosol LWC in PM2.3 are much higher in the haze periods than in the clean periods, suggesting that aqueous reaction is a vital role in the haze formation. In comparison with those in the clean periods, stable carbon isotopic compositions (delta C-13) of major dicarboxylic acids and related SOA and the mass ratios of C-2/cliacids, C-2/Gly and C-2/mGly are higher in the haze periods, indicating that haze particles were more aged and enriched in secondary species. (C) 2019 The Author(s). Published by Elsevier B.V

Design, synthesis and biological evaluation of carbohydrate-based sulphonamide derivatives as topical antiglaucoma agents through selective inhibition of carbonic anhydrase II

A series of new carbohydrate-based sulphonamide derivatives were designed, synthesised by employing the so-call ‘sugar-tail’ approach. The compounds were evaluated in vitro against a panel of CAs. Compared to their parent compound p-sulfamoylbenzoic acid, these compounds showed nearly 100-fold improvement in their binding affinities against hCA II in vitro. All of compounds showed great water solubility and the pH value of their water solutions of compounds is 7.0. Such properties are advantageous to make them much less irritating to the eye when applied topical glaucomatous drugs, compared to the relatively highly acidic dorzolamide preparations (pH 5.5). Notably, compounds 7d, 7 g, 7 h demonstrated to topically lower intraocular pressure (IOP) in glaucomatous animals better than brinzolamide when applied as a 1% solution directly into the eye. Low cytotoxicity on human cornea epithelial cell was observed in the tested concentrations by the MTT assay

Molecular Characteristics and Formation Mechanisms of Biogenic Secondary Organic Aerosols in the Summer Atmosphere at Mt. Tai on the North China Plain

To investigate the molecular characteristics and formation mechanisms of biogenic secondary organic aerosol (BSOA), daytime and nighttime PM2.5 samples were collected at the summit of Mt. Tai during the summer of 2016. The critical indicators of primary sources, such as elemental carbon (EC) and levoglucosan, displayed similar values during the daytime and nighttime, suggesting that changes in the boundary layer heights (BLHs) produced only inconsequential effects during the observation campaign. The molecular distributions of the BSOA were dominated by isoprene SOA tracers (68.5 +/- 42.6 ng m(-3)), followed by monoterpene (43.5 +/- 24.4 ng m(-3)) and beta-caryophyllene (16.3 +/- 8.6 ng m(-3)) SOA tracers. Due to the higher diurnal temperatures and solar radiation, the concentrations of all of the tracers were higher during the day than at night. The ratio of the combined cis-pinonic and cis-pinic acid to the MBTCA (P/M) was much lower than in Chinese cities and at the Tibetan background site, indicating that the monoterpene SOA was relatively aged in the mountainous atmosphere, in large part because of the stronger solar radiation at the peak of Mt. Tai. The concentrations of the BSOA products exhibited a significantly positive correlation with the level of ozone during the daytime (R-2 = 0.58-0.86) and the temperature over the whole sampling period (R-2 = 0.37-0.75), as higher temperatures can accelerate the emission of biogenic volatile organic compounds and the formation of SOA. By contrast, the BSOA tracers displayed a negative linear correlation with the relative humidity (RH) (R-2 = 0.43-0.84) and the in situ particle pH (pH(is)) (R-2 = 0.55-0.70) because high RH can inhibit the acid-catalyzed formation of BSOA due to the dilution of the aerosol acidity. No correlation between the BSOA tracers and anthropogenic pollutants (e.g., levoglucosan, SO42-, NO3- and EC) was observed during the daytime or nighttime, suggesting that BSOA tracers in the atmosphere of Mt. Tai during summer were primarily derived from the local oxidation of BVOCs rather than long-distance-transported anthropogenic emissions from the lowlands

Molecular Compositions and Sources of Organic Aerosols from Urban Atmosphere in the North China Plain during the Wintertime of 2017

PM2.5 samples were collected from Liaocheng, a typical city in the North China Plain, during a winter haze episode around 2017 Chinese Spring Festival (Lunar New Year, LNY) to investigate the impact of firework on organic aerosols. A comparison of PM2.5 concentrations during different periods, with different air mass origins, and under different pollution situations was done. Organic compounds including normal alkanes (n-alkanes), polycylic aromatic hydrocarbons (PAHs), saccharides, and organic acids in PM2.5 aerosols were determined by GC/MS. Sources were analyzed by diagnostics ratios and principal component analysis/multiple linear regression (PCA/MLR) model. The results showed that fireworks burning has significant impacts on fine particle pollution. During the haze period, a sharp increase in n-alkanes, PAHs, saccharides, and fatty acids were observed, but the influence of fireworks burning on n-alkanes concentration is minor. The concentrations of carcinogenic PAHs during haze and LNY periods were more than three times higher than those in the clean period, indicating that PAHs were more carcinogenic during the two periods. In addition, the estimated ILCR for children and adults were both about three times higher than those in the clean periods, suggesting a moderate potential carcinogenic risk in Liaocheng. The higher concentration and the dominance of levoglucoan in the total saccharides suggested that the biomass burning is the predominance source of saccharides. Both the ratios of C-18(:1)/C-18(:0) and BaP/BeP were the highest during the haze period, indicating that aerosols in the haze period were more oxidized. According to the source precise molecular tracers and the PCA-MLR model, coal combustion, biomass burning, and vehicle emissions were the major sources of organic compounds in PM2.5 aerosols during the winter in Liaocheng, cooking activity and firework burning had impact on organic aerosols obviously during LNY. Our data provided first analysis of the molecular distributions and sources of organic aerosols during Chinese Spring Festival in Liaocheng and their potential effects on human health