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 (Fed) to total iron (Fet) ratio (Fed/Fet), hematite (Hm) to goethite (Gt) ratio (Hm/Gt) and saturation isothermal remanent magnetization (SIRM) to magnetic susceptibility (c) ratio (SIRM/X) 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 Fed/Fet 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 0.5to～0.3Ma, after which it becomes warmer and wetter towards the top of paleosol PS1 (equivalent to MIS5). 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 super-imposed on the effects of glacial-interglacial cycles in southern China are also reflected in the 0.4-0.5 Macycle of marine carbon isotopes in the global ocean, possibly indicating a strong link between terrestrial weathering and the global carbon cycle.

Surface sediments (0-5cm) from 59 stations within the Yangtze River intertidal zone (YRIZ) were sampled for metal contamination analysis in April and August 2005. The concentrations ranged (in mg kg-1 dry weight): Al, 40,803-97,213; Fe, 20,538-49,627; Cd, 0.12-0.75; Cr, 36.9-173; Cu, 6.87-49.7; Mn, 413-1,112; Ni, 17.6-48.0; Pb, 18.3-44.1; and Zn, 47.6-154; respectively. Among the 59 sampling stations, enrichment factors (EF) indicate enrichment of Cd (52 stations), Cr (54 stations), Cu (5 stations), Ni (26 stations), Pb (5 stations) and Zn (5 stations). Geoaccumulation indexes (Igeo) also suggest individual metal contamination in localized areas. This study indicates that Cd, Cr and Nienrichment in the YRIZ sediment is widespread whereas Cu, Mn, Pb and Zn enrichment is localized or nonexistent. Factor and cluster analyses indicate that Cd is associated with total organic carbon whereas Cu, Cr, Ni, Pb and Zn have a close association with Mn.

Magnetic susceptibility (χif) and other magnetic parameters of 11 typical profiles of Quaternary Red Clay (QRC) in subtropical China were measured. χlf curves of the QRC profiles show similar vertical variations: χlf of the uppermost yellow-brown earth (YBE) and uniform red clay (URC) of the profiles is high, mostly ranging from 50 to 150×10-8 m3 kg-1; that of the reticulate red clay (RRC) sharply decreases downwards. Especially in the Lower RRC (LRRC) with dense reticulate pattern, χif is often less than 10×10-8 m3 kg-1. Grain-size characteristics and geochemical properties of the QRC suggest that the sharp decrease of χif in the RRC is not related to sudden change of parent materials, but to the formation of the reticulate pattern. Further study indicates that pedogenic fine ferrimagnetic minerals (FM) (superparamagnetic particles (SP) and/or stable single domain (SSD)) are the main magnetic carriers of the QRC. The YBE and URC, with higher χif, show low coercivity and magnetic soft behavior; the RRC, especially the LRRC, with weak magnetism, shows high coercivity and magnetic hard behavior. The temperature-dependent susceptibility (TDS) of the QRC suggests that the dominant type of FM in the YBE and URC is pedogenic maghemite; the RRC, especially the LRRC, however, contains little maghemite but a trace amount of lithogenic multi-domain (MD) magnetite inherited from the parent rock. During post-depositional hydromorphic processes, pedogenic maghemite was more easily dissolved than hematite, which caused the sharp decrease of χif in the RRC. As χif of the QRC was mainly controlled by the intensity of hydromorphic processes, rather than the weathering degree, χif of the QRC in subtropical China cannot accurately indicate the paleoclimate during the Quaternary period, when the red clay was initially formed.

This paper describes 20th century climate and human impacts on terrestrial and fluvial systems in the Dabie Mountains, Anhui Province, China, based on analyses of four types of information. Analyses of particle size, mineral magnetism, organic carbon, nitrogen and phosphorus in a sediment core taken from the Longhekou reservoir, built in 1958 AD in the upper reaches of Hangbu River, provide an ～45 year record of fluvial responses, while monitored meteorological and hydrological data provide records of climate and river discharge. Census data compiled for the local Shucheng County provide records of population and land use, complemented with analyses of satellite images. The Xiaotian river delivers over 65% of the total water and silt to the reservoir. Analyses indicate that the fluvial regime tracks the monsoon climate over seasonal timescales, but human activities have a strongly mediating effect on sediment supply, sediment delivery and, to a lesser extent, runoff over longer timescales. Notable periods of human impact on erosion include the Great Leap Forward (1958-1960) and Great Cultural Revolution (1966-1976). A rising trend in precipitation and new land use changes at the present time may be leading to an enhanced flood risk.

Five soils derived from different parent materials were sampled from red so ll region of so uthern China and studied by magnetic methodology to understand to what extent iron reduction would afect so ll magnetic properties and how iron reduction would afect the magnetic minerals in soils. Reduction associated with organic matter decomposition strongly afected so il magnetic parameters at low pH. The losses of orlginal soil magnetic signals in terms of magnetic susceptibility (x), ‘Soft’isothermal remanent magnetization ('Soft' IRM), anhysteretic remanent magnetization (ARM)and saturation isothermal remanent magnetization (SIRM)at pH 4—6 during the two-month saturation treatment, were 66％～94％, 54％～90％, 64％～95％and 33％～83％, respectively. These changes were interpreted as a consequence of substantial dissolution of maghaemite and haematite in the soils. At pH 10, however, there was no significant magnetic changeobserved. M oreover, stable single domain soil maghaemite grains were also sensitive to red uction, which suggested that both pedogenic and detrital maghaemite were not stable in acid and reducing environments. Goethite, instead, was the most stable iron form under reducing conditions.