Search

Given the great importance of Yundang lagoon (China), a detailed evaluation and source identification of multiple potentially toxic elements (PTEs) is required. Low concentrations of the PTEs were found in the Diversion canal, while high in the Main canal, Inner lagoon, and Outer lagoon. Evaluation results indicated that the pollution of PTEs was widespread, and that the extremely high eco-risks and evident toxicity were owing to the great contributions of Hg and Cd. Positive matrix factorization model demonstrated that the PTEs were from both natural and different types of anthropogenic sources. TOC played a critical role in the PTEs. It was also found that the limited environmental carrying capacity and the poor hydrological condition of the lagoon may still accumulate the pollution in a progressive fashion. These findings provide a detailed information on making effective strategies of new directions for long-term prevention of PTEs pollution in the landscape urban lagoon. • The pollution of multiple typical PTEs in Yundang lagoon of China was evaluated. • The eco-risks and toxicity posed by PTEs were assessed. • Natural process and different types of human sources contributed to the enrichment of PTEs. • Efficacy of continuous remediations on sediment quality was tentatively discussed. [ABSTRACT FROM AUTHOR]

Based on the analysis of carbonate content and loss on ignition for a long sediment core (737 m in length) drilled in Heqing, the orbital scale evolution of the Southwest Monsoon is revealed, by using overlapped spectral analysis and filter methods. It is shown that the obliquity cycle and precession cycle are the key factors for the Southwest Monsoon evolution and that the change of the global ice volume and the uplift of the Qinghai-Tibetan Plateau also impose great influences on it. [ABSTRACT FROM AUTHOR]

Dating lake sediment using sedimentary event is the supplement and calibration to traditional dating by radionuclide such as 210Pb and 137Cs. Based on the change of spheroidal carbonaceous particle (SCP) concentration, the age sequence of lake sediments can be deduced. It is one of the dating methods using sedimentary event. SCP is formed from combustion of fossil fuel at high temperature up to 1750°C and at a rate of heating of approaching 104 °C/s. It can be dispersed to several hundred kilometers away from its source and deposited with precipitation or dryly deposited, and kept in sediments. Compared with Cs or Pb, there is no evidence for SCP that it decays in lake sediments and is un-removable once stored except by physical disturbance because it is mainly composed of element carbon. Handy method to extract, identify and calculate has been developed. Although fossil fuel has been used early in China, combustion at high temperature started later since emergence of electricity generation. The productivity of SCP is positively related with the generated thermal power, which is reflected as the SCP concentration in lake sediments increases with the increase of generated thermal power. Therefore, reliable sediment markers from the start of the SCP record and the remarkable variation can be used for dating purpose. In China, electricity industry started from the 1950s, and rapid increase of generated power took place since 1978. Based on these time markers, SCP time sequences of lake sediment cores LH and LL-4 from Longgan Lake, the middle reach of the Yangtze River, have been established, which is comparable with the results from 137Cs and 210Pb, and has eliminated the errors of dating using 137Cs and 210Pb. [ABSTRACT FROM AUTHOR]

Simulated research of internal loading and collecting and analyzing the samples from the lakes were carried out before and after dredging in polluted suburb lakes, Wuli Lake (Wuxi City) and Xuanwu Lake (Nanjing City). The research results showed that dredging can inhibit internal loadings in a certain degree in a short term. The discrepancy of dredging effect and technical level, namely dredging quality, by different dredging methods will result in a difference of control of lake internal loadings. The internal loadings' reversion will gradually appear along with the biogeochemical processes, including suspended particle precipitation, hydrodynamic disturbance and microbio-transformation. The reversion rate mainly depends on the dredging method and the change of interracial processes on the newborn surface layer. The higher nutrient contents and organic matter in the sediment will enhance water-sediment interfacial processes and nutrients regeneration. It is very important to study the physicochemical and biological character of lacustrine sediments before dredging for determining the dredging methods and predicting their environmental effect. [ABSTRACT FROM AUTHOR]

Yellow River erosion through Longyang Gorge and Sanmen Gorge at 0.15 Ma corresponds with a rapid uplifting of the Qinghai-Xizang (Tibet) Plateau and strong incision in the middle and upper reaches of the Yellow River. Evidence from the upper reaches, middle reaches and lower reaches suggests that this event was controlled by intensive tectonic movement and climatic change. Evidence suggests that the onset of the last interglacial in the upper reaches began a little earlier than 0.15 Ma, and coincides with lake sedimentary records, and oxygen isotope records from the Guliya ice core in the Tibet Plateau. [Copyright &y& Elsevier]

Wetland is the conjunction of lake and terrene where human activities are concentrated. From the viewpoints of material transport and cycling in the terrene-lake system, wetland is the buffer where sand and mud, heavy metals, pollutants and nutrients are tarried. In this paper, we provide a case study based on the temporal and spatial distribution of elements in the Wangling River catchment, a small sub-catchment of Longgan like in the middle reaches of the Yangtze River. We have found that wetland can buffer major heavy metals such as Cr, Cu, etc. significantly, but has a little buffer function to some active elements such as Fe and Mn, which are always transported as solutions. Human activities not only influence the distribution of elements, but also weaken the buffer function of wetland. Intensive human activities in the Longgan like area in the past 70 years have been recorded in stream, wetland and lake sediments, especially the human activity events such as deforesting and reclaiming on a large scale in 1958 and the 1980's. Human activities caused the increase of sedimentation rates since the 1950's, as well as the increase of elements' concentrations. The extensive use of fertilizers and pesticides since the 1960's have led to the increase of total P concentrations. Increasing SO; emission accelerate the process of cation exchange in soil, and enhance the leaching of Mn out of soils. Permanent storing of water causes the soil gleyification that also intensifies the leaching of Mn. These are two major reasons for the obvious increase of manganese concentrations in recent 20 years in Longgan Lake. Intensive human activities since the 1950s' have intensified the population in this region and thus destroyed the buffer function of wetland. [ABSTRACT FROM AUTHOR]

Taihu Lake is one of the largest freshwater lakes in China. The lake is very shallow with a mean depth of 1.9 m and an area of 2428 km². This is the first time that polycyclic aromatic hydrocarbon concentrations in the surface sediments of Taihu Lake have been analyzed. A distinctive spatial distribution of PAHs was observed. Sediments from Lake Wulihu and Meiliang Bay (sites 1–5) had significantly higher PAH concentrations (858–5260 μg kg?1 dw) than any other area of Taihu Lake. These high PAH levels were associated with the input of untreated and partially treated domestic and industrial sewage from Wuxi, Changzhou, Wujin and other cities. Special PAH ratios, such as phenanthrene/anthracene and fluoranthene/pyrene, were calculated to evaluate the relative importance of different origins. The data confirmed a relatively high level of petrogenic contamination in sites 1–5 (mainly sewage discharge and the river runoff). The other samples were further from the sources of pollution and have relatively low PAH concentrations (410–768 μg kg?1 dw). The sources of PAHs in these sites (6–13) were characterized by combustion-derived PAH contamination associated with atmospheric deposition. In addition, effects range low (ERL) and effects range median (ERM) guidelines (Long et al., 1995) were used to estimate the potential of adverse effects resulting from PAH contamination in Taihu Lake sediments. The results indicated that some sites in the northern part of the lake had levels of PAH that exceeded the ERL value. This was interpreted to mean that acute biological effects may occasionally be expected to occur. [ABSTRACT FROM AUTHOR]

Studies the mechanism of remanence acquisition on sediments. Errors created by depositional remanent magnetization and postdepositional remanent magnetization; Subtle changes in mineralogy into and out of a self-reversal region of a viscous magnetization region; Physical disturbances that may result in the remanence alteration.

Examines the mathematical approach to sedimentary component partitioning of polymodal sediments and its applications. Determination of the sedimentary components of polymodal sediments; Distribution function and numerical partitioning of grain-size component; Application of numerical partition to hydraulic and eolian sediments.