East Asian summer monsoon intensity inferred from iron oxide mineralogy in the Xiashu Loess in southern China

The Xiashu Loess, in comparison to the well-studied loess sequences in the Chinese Loess Plateau (CLP), provides a good opportunity for studying East Asian monsoon variations from a southern China perspective. Here we present a study of the iron oxide mineralogy of the Xiashu Loess using integrated geochemical and diffuse reflectance spectroscopy (DRS) measurements as well as magnetic data. Our results show that the free iron oxide (Fe_d) to total iron (Fe_t) ratio (Fe_d/Fe_t), hematite (Hm) to goethite (Gt) ratio (Hm/Gt) and saturation isothermal remanent magnetization (SIRM) to magnetic susceptibility (χ) ratio (SIRM/χ) all indicate particularly strong summer monsoons during the formation of paleosols PS5 and PS4 (equivalent to Marine Isotope Stage 13 and 11, respectively). However, magnetic susceptibility and Fe_d/Fe_t are not consistently reliable indicators of summer monsoon intensity for the whole section. Our results indicate that a multi-proxy approach can give a more reliable summer monsoon intensity reconstruction. The summer monsoon shows a cooling trend and a declining of precipitation from 0.5 to ～0.3 Ma, after which it becomes warmer and wetter towards the top of paleosol PS1 (equivalent to MIS 5). However, PS1 was formed under a relatively cooler temperature and wetter soil conditions in comparison to PS5 and PS4. Such supra-orbital variations in the East Asian summer monsoon superimposed on the effects of glacial–interglacial cycles in southern China are also reflected in the 0.4–0.5 Ma cycle of marine carbon isotopes in the global ocean, possibly indicating a strong link between terrestrial weathering and the global carbon cycle.     

Simulation of groundwater dynamics in the North China Plain by coupled hydrology and agricultural models

We simulated the effects of irrigation on groundwater flow dynamics in the North China Plain by coupling the NIES Integrated Catchment‐based Ecohydrology (NICE) model with DSSAT‐wheat and DSSAT‐maize, two agricultural models. This combined model (NICE‐AGR) was applied to the Hai River catchment and the lower reach of the Yellow River (530 km wide by 840 km long) at a resolution of 5 km. It reproduced excellently the soil moisture, evapotranspiration and crop production of summer maize and winter wheat, correctly estimating crop water use. So, the spatial distribution of crop water use was reasonably estimated at daily steps in the simulation area. In particular, NICE‐AGR reproduced groundwater levels better than the use of statistical water use data. This indicates that NICE‐AGR does not need detailed statistical data on water use, making it very powerful for evaluating and estimating the water dynamics of catchments with little statistical data on seasonal water use. Furthermore, the simulation reproduced the spatial distribution of groundwater level in 1987 and 1988 in the Hebei Plain, showing a major reduction of groundwater level due mainly to overpumping for irrigation. Copyright © 2006 John Wiley & Sons, Ltd.     

The Martian Nonhydrostatic Components of Moment-of-Inertia

The author puts forward the proposal in this paper that all the terrestrial planets (Venus, the Earth, and Mars) as well as the Moon deviate from hydrostatic equilibrium to some degree. The Earth's level of deviation of these four celestial bodies is minimum, and that of Mars is maximum. Moreover, the author estimates Martian nonhydrostatic components of the principal moments-of-inertia using five models for the interior of Mars. Comparison with other terrestrial planets shows that setting the range of mean moment-of-inertia ratio, I/MR², in 0.345 ~ 0.355for Mars is reasonable. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contemporary processes of environmental information in the atmosphere-glacier-runoff system in an area of typical monsoon temperate glacier

Sampling was carried out at Baishui No. 1, the largest glacier on Mt. Yulong, China, during the summers of 1999 and 2000, to investigate the spatial variations of oxygen isotopes in the atmosphere-glacier-river system. The results confirm that there is an inverse relation between the oxygen isotopic composition of precipitation and air temperature/precipitation amount. This suggests that a strong “precipitation amount effect” exists in this typical monsoon temperate-glacier region. There are marked differences of the δ¹⁸O values of winter-accumulated snow, glacial meltwater, summer precipitation and the glacier-fed river water. Spatial and temporal variations of isotopic composition are controlled by climatic conditions. Isotopic fractionation and differentiation occur during phase changes, snow-to-ice and ice-to-meltwater transformations, and runoff processes. Variations of stable isotopes in glacier runoff can indicate variations of sources of supply, as well as different discharge-related processes. Ionic changes occur as a result of meltwater contact with glacier bed materials.

     

Generalized plastic ordinary state-based peridynamic model with shear deformation of geomaterials

Acta Geotechnica - This article aims to propose a generalized plastic model in the ordinary state-based peridynamic framework to study the elastoplastic behaviors of geomaterials, in which the...     

Numerical simulation of the Rongcharong paleolandslide river-blocking event: implication for the longevity of the landslide dam

Landslides - Numerous paleolandslide dams are distributed along the upper reaches of the Jinsha River under the special geological setting of the Tibetan Plateau. A field investigation revealed...     

3D DEM method for compaction and breakage characteristics simulation of broken rock mass in goaf

Acta Geotechnica - An accurate understanding of the breakage mechanism of broken coal and rock mass and its coupling relationship with stress and porosity is important for achieving efficient and...     

Excessive greenhouse gas emissions from wastewater treatment plants by using the chemical oxygen demand standard

Chemical oxygen demand(COD)is widely used as an organic pollution indicator in wastewater treatment plants.Large amounts of organic matter are removed during treatment processes to meet environmental standards,and consequently,substantial greenhouse gases(GHGs)such as methane(CH₄)are released.However,the COD indicator covers a great amount of refractory organic matter that is not a pollutant and could be a potential carbon sink.Here,we collected and analysed COD data from 86 worldwide municipal wastewater treatment plants(WWTPs)and applied a model published by the Intergovernmental Panel on Climate Change to estimate the emission of CH₄ due to recalcitrant organic compound processing in China’s municipal wastewater treatment systems.Our results showed that the average contribution of refractory COD to total COD removal was55%in 86 WWTPs.The amount of CH₄ released from the treatment of recalcitrant organic matter in 2018 could have been as high as 38.22 million tons of carbon dioxide equivalent,which amounts to the annual carbon sequestered by China’s wetlands.This suggests that the use of COD as an indicator for organic pollution is undue and needs to be revised to reduce the emission of GHG.In fact,leaving nontoxic recalcitrant organic matter in the wastewater may create a significant carbon sink and will save energy during the treatment process,aiming at carbon neutrality in the wastewater treatment industry.     

Bagging-based machine learning algorithms for landslide susceptibility modeling

Natural Hazards - Landslide hazards have attracted increasing public attention over the past decades due to a series of catastrophic consequences of landslide occurrence. Thus, the mitigation and...     

Quantitative research on drought loss sensitivity of summer maize based on AquaCrop model

Natural Hazards - In this study, the growth periods of summer maize were divided into seedling, booting and flowering-grain stage. Based on the simulation results of AquaCrop model, the drought...