Traffic-related pollution history (1994–2014) determined using urban lake sediments from Nanjing, China

With the development of urbanisation and the increasing number of modern vehicles, traffic contamination has become an important source of environmental pollution. Most previous studies have focused on using roadside soil or plants to determine the spatial pattern of traffic pollutants along roads and the factors that influence this pattern, whereas few studies have reconstructed pollution histories caused by traffic using suitable methods. In this study, two gravity cores were obtained from Qianhu Lake, which is in the Zhongshan tourist area of Nanjing City and is distant from industrial areas. An accurate chronological framework covering the period from 1994 to 2014 was established using the correlation between the variation in grain size of the sediment cores and the variation in annual rainfall in Nanjing City. Moreover, magnetic and chemical parameters were also measured, and the results demonstrated that concentration-related magnetic parameters exhibited different correlations with different heavy metal concentrations. These correlations were significantly positive for Zn, Pb, and Co; weakly positive for Ni; absent for Cr; and negative for V. Combined with statistical data on industrial emissions and private cars in Nanjing City since 1994, the observed variations in magnetic susceptibility, anhysteretic remanent magnetisation, saturation isothermal remanent magnetisation, Zn, Pb, and Co, were controlled by traffic activities in the tourist area but not by industry. Therefore, the variations in these parameters record the traffic pollution history of the study area. Combined with the obtained chronological framework, the traffic-related pollution history could be divided into two stages: 1) from 1994 to 2003, when traffic-related pollution became increasingly serious because of the exponential increase in the number of private cars and the prosperity of tourism; 2) from 2003 to 2014, when traffic-related pollution continuously increased but at a much slower rate than in stage 1. This slower rate of increase was probably related to the maximum carrying capacity of the tourist area and technological innovations in automobile manufacturing, as well as improvements in fuels.

A Historical Record of Trace Metal Deposition In Northeastern Qinghai-Tibetan Plateau For The Last Two Centuries

Owing to rapid socio-economic development in China, trace metal emissions have increased and lakes even in remote areas have experienced marked changes in the last century. However, there are limited studies revealing long-term trends, anthropogenic fluxes and spatial characteristics of trace metals in lakes. In this study, we present a geochemical record from Lake Qinghai in the northeastern Qinghai-Tibetan Plateau and reconstruct trace metal pollution history during the last two centuries. The lacustrine sediment core was dated by 137Cs and 210Pb, and sediments deposited prior to the 1850s were selected as the pre-industrial background. Factor analysis and enrichment factor indicated Cr, Cu and Ni generally originated from natural sources, while Cd, Pb and Zn have been influenced by human contamination since the mid-1980s. The anthropogenic Cd mainly derived from non-ferrous metal smelting in Gansu Province, and fluxes to Lake Qinghai sharply increased after the mid-1980s. The timing is similar to other lake sediment records from China and corresponds well with rapid economic development in China. The spatial pattern of anthropogenic Cd fluxes to lakes is primarily attributed to regional industrial emission, phosphate fertilizers and manure applied in agriculture.

Mongolian peatland documents 5000-year pollution history and a baseline of Pb and Tl in northeastern Asia

<p>Peat records of trace metals pollution history over thousands of years are not widely reported in northeastern Asia, although the mining/metallurgy have already started in the past 5000 years. Peat core was collected in September 2015, from the Nur Sphagnum bog, in Selenge province, in the NW part of the Kenthii Mountains, Mongolia. The Nur Sphagnum bog (49°39’N; 107°48’E; 1250 m.a.s.l.) is the largest wetland located in the mountain taiga forest of Mongolia in the northern part of the Hentei highlands. The mean January and July temperatures are -27.1°C and 18.3°C respectively, while mean annual precipitations are 288 mm. The peatland is composed of than 10 species of Sphagnum, while herb layer is dominated by Carex rostrata, and several species of Sphagnum. The dominant tree species are composed of Betulaplatyphylla, Pinussylvestris, Piceaobovata and Abiessibirica. As for the Nur bog, no research on elemental or isotopic geochemistry was undertaken currently. Our preliminary geochemical study established a baseline for typical heavy metal, Pb, 1.1 mg kg-1, which is reasonable to represent a pre-industrial background value in Mongolia, even in northeastern Asia. The average Pb content through the cores was 2.2 mg kg-1, which was significantly lower than the level in northeastern China and showed that the it was still typical area of pristine ecosystem in northern Mongolia. However, the elevation of Pb and Tl contents in the near surface layers was also observed, with an enrichment factor of 6, which suggested that the anthropogenic impact was approaching in this region and more attention should be paid to safeguard its nature heritage.</p>

Determination of Metal Concentration in Road-Side Trees from an Industrial Area Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Historical pollution can be elucidated with variations of elements’ concentration in tree rings by using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). However, the capacity of chemical elements’ absorption significantly depends on the tree species and element types. Metal concentrations in the rings for five species (Platanus occidentalis, Salix koreensis, Chamaecyparis obtusa, Pinus densiflora, Ginkgo biloba) were investigated in light of metal pollution history in ambient air of D industrial site located in Daejeon, Korea. The calibration for LA-ICP-MS was performed using cellulose-matrix matched standards with 13C normalization. Tree ring series except for Ginkgo sp. showed that the accumulation rates of Pb and Cd were higher between 1992 and 1999. Other elements, such as Fe, Cr, Mn, Cd, Zn, and Sr, showed a variation in the rings, likely due to the different physiological processes of element uptake and radial mobility. Concentrations of Pb and Cd in the annual rings of Pinus sp. corresponded to the metal monitoring data for the ambient air with the correlation coefficients of 0.879 and 0.579, respectively. Moreover, Cd in Platanus sp. and Pb in Salix sp. showed a positive correlation to ambient metal concentration compared to Chamaecyparis sp. and Ginkgo sp. Therefore, caution should be taken to select candidate elements as well as tree species to reconstruct the ambient air metal pollution history by measuring the concentration of metal in the tree ring.