Institute of Earth Environment
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The role of earthquake-induced landslides in erosion and weathering from active mountain ranges: Progress and perspectives
No full textEarthquakes play a fundamental role in the evolution of Earth's topography through co-seismic uplift and subsidence, as well as erosion through widespread landslides induced by ground motion. Earthquake-induced landslides can result in exceptional increases in the transfer of mass from landscapes, supplying sediment to rivers where impacts can last for decades or longer. Landslides can also erode vegetation and soils, in addition to exposing freshly ground rock mass, which can both result in regionally significant carbon transfers. Recent work has sought to quantify the fluxes, rates, and temporal patterns of the impacts on earth surface processes generated by these tectonic events. In this review, we focus on the impacts of earthquake-induced landslides on erosion and sediment flux, river water chemistry, and carbon export through the lens of the well-studied 2008 Wenchuan earthquake. We then discuss these themes in the context of works from the 1999 Taiwan Chi-Chi earthquake, 2015 Nepalese Gorkha earthquake, and New Zealand historical earthquakes, altogether highlighting an important role of earthquake-induced landslides in erosion and weathering along tectonically active mountain ranges. We suggest that more monitoring, geochemical tracing, paleo-records, and/or modelling studies are needed to compare the processes and fluxes of catchment erosion and weathering before and after earthquake events, which will help to deepen our understanding not only of the impacts of earthquake-induced landslides on earth surface processes, but also the linkage among high magnitude events, continental erosion and weathering, and the long-term global carbon cycle
Seasonal and Inter-Annual Variations of Stable Isotopic Characteristics of Rainfall and Cave Water in Shennong Cave, Southeast China, and Its Paleoclimatic Implication
No full textSpeleothem calcite stable oxygen isotope (delta O-18(C)) is one of the most widely used proxies in paleoclimate research, and understanding its seasonal-annual variability is very significant for palaeoclimate reconstruction. Five-year precipitation and karst cave water from 2016 to 2021 were monitored in Shennong cave, Jiangxi Province, Southeast China. The local meteoric water line (LMWL) is delta D = 8.20 x delta O-18 + 13.34, which is similar to the global meteoric water line. The stable hydrogen and oxygen isotope (delta D and delta O-18) characteristics of precipitation and cave water were studied. delta O-18 and delta D of precipitation and cave water show obvious seasonal variations. Lower precipitation delta O-18 and delta D generally occur during summer and autumn compared with higher delta O-18 and delta D values during winter and spring. Meanwhile, low precipitation delta O-18 values do not only appear in June-July when precipitation is the highest of the year but also appear in August-September when precipitation is limited. The back-trajectory analysis of monsoon precipitation moisture sources shows that the moisture uptake regions vary little on inter-annual scales; the water vapor of rainfall in June-July comes from the South China Sea and the Bay of Bengal, while the moisture source in August-September is mainly from the West Pacific and local area. The El Nino-Southern Oscillation is an important factor affecting the value of delta O-18 by modulating the percentage of summer monsoon precipitation in the annual precipitation and moisture source. The relationship between amount-weighted monthly mean precipitation delta O-18 and Nino-3.4 index shows that the East Asian summer monsoon (EASM) intensifies during La Nina phases, resulting in more precipitation in monsoon season (May to September, MJJAS) and lower delta O-18 values, and vice versa during El Nino phases
Mid-Miocene Lake Level Fluctuations in the Lunpola Basin, Central Tibetan Plateau
No full textKnowledge of paleolake evolution is highly important for understanding the past hydroclimate regime on the Tibetan Plateau and associated forcing mechanisms. However, the hydrological history of paleolakes on the central plateau, the core region of the plateau, remains largely inconclusive. Here we present new biomarker records from lacustrine deposits of the Lunpori section in the Lunpola Basin to reconstruct detailed lake-level fluctuations during the mid-Miocene. A set of n-alkane indexes, including the proportion of aquatic macrophytes (P-aq), average chain length and carbon preference index as well as the content of n-alkanes, vary substantially and consistently throughout the studied interval. Our results altogether show relatively low lake level at similar to 16.3-15.5 Ma and high lake level before and after the interval, which is in line with the lithological observations in the section. Further comparison with existing regional and global temperature records suggests that lake level fluctuations can be largely linked to global climatic conditions during the mid-Miocene, with lake expansion during relatively warm periods and vice versa. Therefore, we infer that global climatic changes might have controlled the lake-level fluctuations in this region during the mid-Miocene, whereas the tectonic uplift likely played a subordinate role on this timescale
Comparison of Equivalent Doses Obtained with Various post-IR IRSL Dating Protocols of K-Feldspar
No full textFive dating protocols with post-infrared infrared (IR) stimulated luminescence signals (i.e. pIRIR) were performed on the K-feldspar of loess samples. Two of them were the single-aliquot regenerative-dose protocol (SAR) with two-step pIRIR stimulation, with the first IR stimulation at 50 degrees C or 200 degrees C and the second at 290 degrees C (pIR(50)IR(290), pIR(200)IR(290)). Two of them were the SAR protocols with five-step or six-step IR stimulation at multiple elevated temperatures to 250 degrees C or 300 degrees C (MET-pIRIR(250), MET-pIRIR(300)). The final one was the multiple-aliquot regenerative-dose (MAR) protocol with the MET-pIRIR(300) signal, together with a 500 degrees C heat treatment administered before the test dose ('MAR with heat'). The results show that when the equivalent dose (D-e) of the sample was less than 500 Gy, all of the protocols gave consistent results; however, when D-e exceeded 750 Gy, all of the SAR protocols underestimated D-e. The pIR(50)IR(290) signal had the highest degree of underestimation, while the pIR(200)IR(290), MET-pIRIR(250) and MET-pIRIR(300) signals had similar D-e values and similar degrees of underestimation. Possible reasons for the SAR D-e underestimation are discussed. We suggest that only the 'MAR with heat' protocol is suitable for samples with D-e exceeding 750 Gy
Evolution of the dry-wet variations since 1834 CE in the Liiliang Mountains, north China and its relationship with the Asian summer monsoon
No full textUnder the background of global climate change, arid to semi-humid areas are more vulnerable to extreme climate, such as floods and droughts. To better predict and cope with future climate change, more local and regional long-term high-resolution climate reconstructions, hydroclimate in particular, are required. Based on a 174-year regional tree-ring-width chronology, we reconstructed the February-June Standardized Precipitation Evapotranspiration Index (SPEI26) history in the Luliang Mountains, North China (NC). Reconstructed SPEI26 is expected to reflect the dry-wet variation from spring to early summer (STES) of NC with an explained variance of 43.8% for the instrumental record (1951-2007 CE). The reconstruction reveals three comparatively dry (1857-1878, 1919-1929 and 1995-2001 CE) and four comparatively wet (1883-1895, 1934-1944, 1952-1961 and 1980-1984 CE) periods during 1834-2007 CE. Although a drying trend is seen since the 1950s, an advent of wetting since the end of the 1990s is expected. As the driest period in the reconstruction, 1919-1929 CE records the widespread catastrophic 1920s drought in northern China. In addition to the local hydroclimatic signal, the reconstruction also reflects hydroclimatic variation over a large portion of northern China, which is evidented by the comparison with other hydroclimatic records and regional dry-wet index. Strength of the Indian summer monsoon and the East Asian summer monsoon in the previous year play vital roles in the STES dry-wet variations. Moreover, Atlantic Multi-decadal Oscillation index influents the hydroclimate in NC by influencing the Asian summer monsoon system
Influence of landfill and land use scenario on runoff, evapotranspiration, and sediment yield over the Chinese Loess Plateau
No full textThe Gully Consolidation and Highland Protection (GCHP) project was implemented across the Loess Plateau. Understanding the impacts of the GCHP requires applications of a distributed hydrologic model. The Soil and Water Assessment Tool (SWAT) and Geography Information System (GIS) were used for evaluating the GCHP project's impact on runoff and sediments in the catchment. The correlation coefficient value, the relative error and the Nash-Sutcliffe index are 0.83, -2.30% and 0.89 for the calibration period of our SWAT model in Yanwachuan (YWC) gully by using SWAT Calibration and Uncertainty Programs (SWAT-CUP) software. The distributed hydrological model was used to simulate five scenarios of a typical watershed YWC gully in Longdong Loess Plateau, and analyzed the response of runoff, sediment, and evapotranspiration under different designed scenarios of GCHP project. The results show that gully head landfill (the loess soil were directly transferred and dumped from other places) can reduce the runoff and sediment. The simulated annual average runoff is about 2.5% lower after landfill than that in the natural state, but the evapotranspiration is about 2.4% higher. The grassland plays a more important role in water conservation than forest vegetation in the YWC watershed. The results also show that the SWAT model is useful for the study of the hydrological response of GCHP at the watershed scale. The results of this study are providing scientific information to predict and prevent soil erosion
The characteristics and sources of roadside VOCs in Hong Kong: Effect of the LPG catalytic converter replacement programme
No full textIn order to improve local air quality of Hong Kong, more than 99% taxies and public light buses were changed from diesel to liquefied petroleum gas (LPG) fuel type in the early 2000s. In addition to the catalytic converters wear and tear, it is necessary to control air pollutants emitted from LPG vehicles. Therefore, an LPG catalytic converter replacement programme (CCRP) was fulfilled from October 2013 to April 2014 by the Hong Kong government. Roadside volatile compounds (VOCs) were measured by on-line measurement techniques before and alter the programme to evaluate the effectiveness of the LPG CCRP. The mixing ratios of total measured VOCs were found decreased from 69.3 +/- 12.6 ppbv to 43.9 +/- 6.5 ppbv after the LPG CCRP with the decreasing percentage of 36.7%. In addition, the total mixing ratio of LPG tracers, namely propane, i-butane, and n-butane, accounted for 49% of total measured VOCs before the LPG CCRP and the weighting percentage decreased to 34% after the programme. Moreover, the source apportionment of roadside VOCs also reflects the large decreasing trend of LPG vehicular emissions after the air pollution control measure. Due to the application of PTR-MS on measuring real-time VOCs and oxygenated volatile compounds (OVOCs) in this study, the emission ratios of individual OVOCs were investigated and being utilized to differentiate primary and secondary/biogenic sources of roadside OVOCs in Hong Kong. The findings demonstrate the effectiveness of the intervention programme, and are helpful to further implementation of air pollution control strategies in Hong Kong. (C) 2020 Elsevier B.V. All rights reserved
Strategies for arsenic pollution control from copper pyrometallurgy based on the study of arsenic sources, emission pathways and speciation characterization in copper flash smelting systems
No full textArsenic in copper flash smelting (FS) systems not only affects the quality of products but also poses significant technological and environmental problems. Based on the assessment of arsenic mass partitioning in the FS system, arsenic elimination in off-gassing and tailings is 22%, and most of the arsenic output (69%) is recycled in the FS system. Circulating arsenic, especially arsenic in recycled dust and slag concentrate, is the key reason for high-arsenic-content feed. Dust-type recycled materials (RMs) contribute much more arsenic to the feed than slag-type RMs. Flash smelting furnace electrostatic precipitator (FSF ESP) dust contributes makese the largest contribution to arsenic among the dust-type RMs of mixed dust, especially trivalent arsenic, followed by FSF and flash converting furnace waste heat boiler (FCF WHB) dust, which contributes pentavalent arsenic. FCF WHB dust exhibits a relatively low arsenic content, consisting mainly of As(V)-O. Slag-type recycled materials contribute As(V)-O to the total feed, and As(III) originates from copper concentrates. Considering the arsenic contribution and environmental risk, reducing the recovery of FSF ESP dust can greatly decrease the arsenic grade of FSF feed and volatile As2O3. As one of the main arsenic sources in feed, FSF slag concentrate should be carefully disposed of if separated from feed materials because of its high arsenic-related environmental risk. In contrast, WHB dust and FCF slag are more suitable as RM due to their high copper content and low arsenic risk. (C) 2020 Elsevier Ltd. All rights reserved
Monsoon variations inferred from high-resolution geochemical records of the Linxia loess/paleosol sequence, western Chinese Loess Plateau
No full textChinese eolian deposits have been investigated intensively to reconstruct East Asian monsoon changes at tectonic to millennial timescales. However, high-resolution elemental proxies sensitive to rapid monsoon changes remains sparse. Here we present multiple elemental ratios of the Linxia loess sequence generated by scanning and conventional X-ray fluorescence (XRF) to assess East Asian monsoon variability at glacial-interglacial to sub-orbital timescales. The results show that 11 elements (Al, Si, K, Ca, Ti, Mn, Fe, Rb, Sr, Zr and Ba) can be reliably measured by XRF scanning of loess cores, albeit with relatively lower precision and increased noise levels (due to variable water content and matrix effects) when compared to XRF scanning of dry and homogenized powder samples. Seven elements (Ca, Fe, Ti, Mn, Zr, Rb and Sr), measured by XRF scanning of the core face and powder samples show high correlation (R-2 > 0.7, n = 100) with those measured by conventional XRF methods, and thus can be considered as robust indicators for chemical weathering and grain-size sorting. We employ element ratios of Ca/Ti and Rb/Sr to reflect precipitation-induced weathering intensity, and the Zr/Rb ratio and mean grain size to infer the sorting effects related to winter-monsoon winds. These element ratios exhibit significant glacialinterglacial fluctuations, similar to records of magnetic susceptibility and mean grain size. Precessional- to millennial-scale monsoon changes are also persistent in our high-resolution elemental proxies, consistent with those in Gulang loess elemental ratios and Hulu/Sanbao speleothem d18O records. Our results suggest that high resolution XRF scanning elemental ratios of Chinese loess have great potential for evaluating co-evolution of orbital- and millennial-scale monsoon variations
Relative humidity variation derived from tree-ring delta O-18 and possible large-scale atmospheric circulations linkage over the Guanzhong Plain, central northern China, since 1760 CE
No full textChina is drastically influenced by the Asian monsoon. Based on the relationship (r = -.636, N = 62, p < .001) between tree-ring delta O-18 values from nine cores of Pinus tabulaeformis Carr. from Nanwutai and the Asia monsoon-related June-August relative humidity (RHJJA), we designed a transfer function reconstructing the RHJJA variation from 1760 to 2018 CE. Our RHJJA reconstruction captured some extreme climatic events that occurred in the past, such as the Ding-Wu disaster (1876-1878 CE), which was the most serious drought event of northern China in the 19th century, and the severe drought event of 1925-1930 CE. The spatial correlation analysis shows that our RHJJA reconstruction has not only local but also large-scale hydroclimate circulations. Our reconstruction compared well with other hydroclimate series from northern China, indicating the large-scale representativeness of our reconstruction. Both the ensemble empirical mode decomposition (EEMD) and the periodicity analyses revealed that the El Nino-South Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), the Arctic Oscillation (AO) and the solar activity strongly affected Asian monsoon-related RHJJA changes over Guanzhong Plain in the past. We believe this study is of great significance and provides an in-depth understanding of climate change in the Guanzhong Plain and in northern China