Institute of Earth Environment
Institutional Repository of Institute of Earth Environment, CASNot a member yet
7120 research outputs found
Sort by
A Route Map for Successful Applications of Geographically Weighted Regression
No full textGeographically Weighted Regression (GWR) is increasingly used in spatial analyses of social and environmental data. It allows spatial heterogeneities in processes and relationships to be investigated through a series of local regression models rather than a single global one. Standard GWR assumes that relationships between the response and predictor variables operate at the same spatial scale, which is frequently not the case. To address this, several GWR variants have been proposed. This paper describes a route map to decide whether to use a GWR model or not, and if so which of three core variants to apply: a standard GWR, a mixed GWR or a multiscale GWR (MS-GWR). The route map comprises 3 primary steps that should always be undertaken: (1) a basic linear regression, (2) a MS-GWR, and (3) investigations of the results of these in order to decide whether to use a GWR approach, and if so for determining the appropriate GWR variant. The paper also highlights the importance of investigating a number of secondary issues at global and local scales including collinearity, the influence of outliers, and dependent error terms. Code and data for the case study used to illustrate the route map are provided
Upward trend and formation of surface ozone in the Guanzhong Basin, Northwest China
No full textIncrease trend of surface ozone (O-3) was observed in the Guanzhong Basin (GZB) from 2014 to 2020 with growth rates of 3.9-6.4 mu g M-3 yr(-1) for the maximum daily average 8 h (MDA8) O-3 concentrations. To further understand the formation of O-3 , investigation of volatile organic compounds (VOCs) was carried out in the summer of 2018. High levels of VOCs were observed in both residential area and industrialized cities. Elevated concentrations of none-methane Hydrocarbon (NMHCs) were observed in rush hours, which indicated dominated roles of traffic activities on the loading of ambient VOCs. In the nighttime, both of NMHCs and oxygenated VOCs (OVOCs) were raised, and the peaks of VOCs kept pace with accumulation of O-3 . Wind field indicated that northward and westward air mass, which passed through the remote forest and industrial area in east of the GZB, was responsible to elevated ambient VOCs in the GZB. Traffic emission, fuel evaporation, and solvent using were key contributors to ambient NMHCs, while solvent using and secondary formation dominated the loading of OVOCs. The present study indicated that both local management and regional collaborative control on active VOCs species from typical sources is urgently needed in GZB
Comparison of analytical sensitivity and efficiency for SARS-CoV-2 primer sets by TaqMan-based and SYBR Green-based RT-qPCR
No full textThe pandemic of coronavirus disease 2019 (COVID-19) continues to threaten public health. For developing countries where vaccines are still in shortage, cheaper alternative molecular methods for SARS-CoV-2 identification can be crucial to prevent the next wave. Therefore, 14 primer sets recommended by the World Health Organization (WHO) was evaluated on testing both clinical patient and environmental samples with the gold standard diagnosis method, TaqMan-based RT-qPCR, and a cheaper alternative method, SYBR Green-based RT-qPCR. Using suitable primer sets, such as ORF1ab, 2019_nCoV_N1 and 2019_nCoV_N3, the performance of the SYBR Green approach was comparable or better than the TaqMan approach, even when considering the newly dominating or emerging variants, including Delta, Eta, Kappa, Lambda, Mu, and Omicron. ORF1ab and 2019_nCoV_N3 were the best combination for sensitive and reliable SARS-CoV-2 molecular diagnostics due to their high sensitivity, specificity, and broad accessibility
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
Tree-ring oxygen isotope recorded precipitation variations over the past two centuries in the northeast Chinese Loess Plateau
No full textIt was shown in previous studies that tree-ring oxygen isotope (delta O-18(TR)) was a proxy of regional precipitation. Using two delta O-18(TR) chronologies of Pinus tabulaeformis Carr. in northeast Chinese Loess Plateau (CLP), we synthesized a master series which had a high correlation with regional precipitation from previous-year September to current-year August (P-SA) (r = -0.650, N = 52, p < .001). Thus we reconstructed the P-SA over the past two centuries (AD 1808-2009) for the northeast CLP. The results of calibration-verification tests indicated that the precipitation reconstruction was stable and reliable. Compared with reconstructions based on the tree-ring width and historical documents, the P-SA reconstruction reserved more decadal low-frequency climate signals such as the drying trend since the 1930s. Superposed epoch analysis (SEA) showed that the large tropical volcanic eruptions significantly reduced P-SA in the first year after the eruptions. The contrast of the regional precipitation reconstructions in the west, northeast, and southeast CLP demonstrated that spatial and temporal differences of precipitation variation. In terms of extreme climate events, major droughts in the mid-to-late 1920s were recorded in all three regional precipitation records, while the Ding-Wu Disaster (AD 1876-1878) was only found in the southeast CLP. Under the background of the weakening Asian monsoon and global warming, CLP was more prone to droughts in the last five decades
Soil erosion and human activities over the last 60 years revealed by magnetism, particle size and minerals of check dams sediments on the Chinese Loess Plateau
No full textSoil erosion has become more serious in semiarid areas around the world. However, the discrimination of the impact of concurrent climate change and human activity on soil erosion in a particular study area remains a challenge. Check dams are important engineering measures to prevent soil erosion on the Chinese Loess Plateau, and the dam sediments, as the product of soil erosion, are related to both climate change and human activities in a small watershed. The present study selected a check dams sediment profile in the upper Jinghe Basin on the Chinese Loess Plateau as a case study. Based on AMS C-14 dating and Cs-137 measurement, we established the soil erosion timescale and employed multiple methods including magnetic susceptibility, particle size, and minerals to trace the soil erosion history. We compared them with a local hydrometeorological record in the Jinghe Basin to explore the relationship between soil erosion and human activities. AMS C-14 and Cs-137 results indicated that the profile was deposited since 1953. The results of magnetic susceptibility, particle size, and minerals revealed 3 soil erosion phases during the last 60 years. Soil erosion in this region is not only related to precipitation changes, but also closely related to human activities. Prior to the Reform and Opening-up in China in 1978, climatic change played a leading role in check dams sedimentation and hydrological changes. Subsequently, despite accelerated soil erosion associated with the family contract responsibility system, the check dams, afforestation and a warmer climate mitigated the soil erosion to some extent, runoff and sediment load continued to decrease. Since 1999, China's Grain for Green project has greatly reduced the runoff and sediment load. However, the policy of filling gullies and creating land since 2010 should be reconsidered carefully in terms of all aspects, including the eco-environment, hydrological cycle, and economics
Assessing the Modern Multi-Decadal Scale Aridification Over the Northern China From a Historical Perspective
No full textNorthern China (35 degrees-50 degrees N; 105 degrees-125 degrees E) has experienced a multidecadal aridification since 1950s, which was mainly manifested by multi-decadal scale decreases of regional precipitation and soil moisture, and brought severe influences on societal and economic developments. However, the position of this aridification among the historical aridification events over northern China during the last millennium has not been fully assessed. Furthermore, the contributions from anthropogenic forcings, natural forcings, and internal variability on this aridification have not been quantitatively differentiated. In this study, observations, proxy reconstructions, and model simulations from community Earth system model last millennium ensemble archive were used to assess this aridification from a historical perspective, and differentiate the contributions from different forcings and internal variability. It was found that duration and magnitude of this aridification are more prominent than most of aridifications during the last millennium. The comparisons between control experiment and sensitivity experiments show that the external forcings, especially anthropogenic forcings, result in a significant larger aridification rate than other historical aridifications. Only combined impacts from internal variability (i.e., Pacific Decadal oscillation, PDO and Atlantic Multidecadal oscillation (AMO)) and anthropogenic forcings (e.g., greenhouses gas emission, anthropogenic aerosol emission, and land use cover changes) can result in such a severer aridification than historical aridifications. The results also confirm that the phase shifts of PDO and AMO trigger this aridification over the northern China, and, whether external forcings contribute to these phase shifts were also discussed
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
Enhanced peroxymonosulfate activation by Cu-doped LaFeO3 with rich oxygen vacancies: Compound-specific mechanisms
No full textThe degradation reaction mechanisms of organic pollutants by peroxymonosulfate (PMS) activation processes remain controversial. In this study, Cu-doped LaFeO3 samples were prepared and used as heterogeneous catalysts of PMS for the degradation of pharmaceuticals. Compared to LaFeO3 (LFO), the increased catalytic activity of LaFe1-xCuxO3 (LFCO) samples was observed, among which LFCO-7.5 exhibited the best performance. The enhanced catalytic activity of LFCO-7.5 was attributable to the generation of abundant oxygen vacancies. Hydroxyl radicals, sulfate radicals, superoxide and singlet oxygen were detected in the LFCO-7.5/PMS system. However, selective effects of radical scavengers on the degradation of different pharmaceuticals and selective reactivity of singlet oxygen toward different pharmaceuticals indicate the existence of compound-specific degradation mechanisms in the LFCO-7.5/PMS system. Furthermore, possible degradation pathways of SDZ and the toxicity evolution were investigated during sulfadiazine (SDZ) degradation. This study further enhances our knowledge on the degradation reaction mechanisms of organic pollutants in PMS activation processes
Impacts of Transboundary Transport on Coastal Air Quality of South China
No full textTransboundary transport plays an important role in air pollution formation in China. The coastal area of south China (CA-SCHN) frequently experiences air pollution in spring and autumn, but the contribution of transboundary transport to the air quality is still not clear. Meteorological field analyses reveal that large-scale synoptic patterns over east China in spring and autumn provide favorable situations facilitating southward transport of air pollutants originated from the North China Plain (NCP) and Yangtze River Delta (YRD). A springtime case study using the WRF-Chem model shows that trans-boundary transport of air pollutants from the NCP and YRD contributes to 27% and 46% of ozone (O-3) and fine particulate matter (PM2.5) concentrations in the CA-SCHN, respectively. In the autumn case, the contribution is around 11% for O-3 and 24% for PM2.5. In the spring, air pollutants in the NCP and YRD are transported over seas by large-scale synoptic systems to the South China Sea and re-circulated by the sea breeze to the CA-SCHN during daytime. In the autumn, the transport is driven by northerly winds over the land induced by large-scale synoptic systems, and is also modulated by the local mountain-valley breeze circulation. The results provide support for design and implementation of air pollutants control strategies in the CA-SCHN