The rise and demise of the Paleogene Central Tibetan Valley

Reconstructing the Paleogene topography and climate of central Tibet informs understanding of collisional tectonic mechanisms and their links to climate and biodiversity. Radiometric dates of volcanic/sedimentary rocks and paleotemperatures based on clumped isotopes within ancient soil carbonate nodules from the Lunpola Basin, part of an east-west trending band of basins in central Tibet and now at 4.7 km, suggest that the basin rose from 4.0 km by 29 Ma. The height change is quantified using the rates at which wet-bulb temperatures ( ) decline at land surfaces as those surface rise. In this case, fell from ~8°C at ~38 Ma to ~1°C at 29 Ma, suggesting at least ~2.0 km of surface uplift in ~10 Ma under warm Eocene to Oligocene conditions. These results confirm that a Paleogene Central Tibetan Valley transformed to a plateau before the Neogene

Distribution, bioavailability and contamination assessment of mercury and arsenic in the surface sediments from the Yellow River Estuary, China

The distributions of mercury (Hg) and arsenic (As) in the surface sediments of the Yellow River Estuary (YRE) of China were investigated. The average Hg concentration (54.05 ng g(-1)) in the YRE sediments was much higher than the background, while the average As concentration (9.53 mu g g(-1)) was comparable with the background. Atmospheric deposition Hg might be the major source of Hg in most studied sediments, while the point source Hg discharge might explain the relatively high levels of Hg in the specific site. The agricultural non-point source pollution and the natural sources might be the main source of As in the YRE sediments. The result of the European Community Bureau of Reference (BCR) sequential extraction experiment showed that the most hazardous fraction (F1) contributed only a small percentage of the total concentrations for both Hg and As while the fraction with low mobility and bioavailability (F4) represented the maximum composition, indicating a low risk of mobility and bioavailability for Hg and As in the sediments. In addition, multiple indices and guidelines for sediment quality assessments were used in this study, results suggested a "good state" regarding Hg and As contamination in the surface sediments from the YRE

Levels of metals in fish tissues of Liza haematocheila and Lateolabrax japonicus from the Yellow River Delta of China and risk assessment for consumers

The Yellow River Delta (YRD) is an important spawning and nursery area for numerous fishes. The concentrations of Fe, Al, Mn, Zn, Ni, Cr, Cu, Co, Pb and Cd in muscle, liver, gills and skin of two broadly distributed commercial fish in the YRD were analyzed. The results demonstrated that liver and gills displayed higher accumulation ability of metals than other tissues, while muscle always accumulated the lowest concentrations of metals. Generally, significant opposite relationships (p < 0.05) were observed between fish size and metals in fish tissues especially in muscles of both fish species which may be explained by the lower feeding rate, stronger detoxification and elimination mechanisms in the bigger individuals. All metals in muscles were well below the proposed toxic limit. Besides, the toxic effects were not expected to occur for the consumption of muscles of studied fish according to the results of human health risk assessment

An 87-year sedimentary record of mercury contamination in the Old Yellow River Estuary of China

A sediment core, spanning from the year 1925 +/- 3.03 to 2012, was collected for analyzing historical distribution of mercury (Hg) in the Old Yellow River Estuary (OYRE), China. The Hg concentrations in the sediment core ranged from 14 to 351 ng g(-1), with the high values occurred in the middle layers (1960-1996), which may be resulted from intensive human activities during this period, such as oil exploitation and booming of petrochemical industry, salt chemical industry and chlor-alkali plants. A significant positive correlation was found between THg and loss on ignition (LOI). The main fraction of Hg existed in residual part while the fraction that was easy to leach out from sediments accounted for only a small portion according to the results of BCR sequential extraction procedure. Multiple ecological risks indices and guidelines of Hg indicated that the sedimentary record presented an "intermediate state" for Hg contamination in the OYRE

Metal distribution and bioavailability in surface sediments from the Huaihe River, Anhui, China

This study presents the total concentrations and chemical fractionations of metals (Cu, Pb, Zn, Ni, Fe, and Mn) in 54 surface sediment samples collected from the Huaihe River (Anhui Province) in eastern China. Compared with the average shale values, Zn and Pb exhibited the most substantial anthropogenic enrichment, especially in Fengtai and Huainan areas, the main industrial districts along the Huaihe River (Anhui Province). Low levels of Cu and Ni were observed in the sediments. Based on risk assessment code (RAC), the metals associated with weak acid soluble (F1) in the Huaihe River sediments followed the order: Mn &gt; Zn &gt; Cu &gt; Pb &gt; Ni &gt; Fe. Manganese presented the most potential for releasing into the aqueous environment and can easily enter the food chain. Copper, zinc, nickel, and iron were found dominant in the residual fraction, implying that these four metals were strongly bound to the sediments. Lead showed a different partitioning pattern from that of other metals studied, with a large percentage in Fe-Mn oxide fraction, indicating that slight redox potential changes may make significant influence on the removability of Pb. Moreover, Cu in oxidizable (F3) and residual (F4) fractions presented high positive correlation with organic matter, which can explain the high percentage of Cu in these two fractions

The distributions, contamination status, and health risk assessments of mercury and arsenic in the soils from the Yellow River Delta of China

The surface soils were collected from four areas in the Yellow River Delta (YRD), including three functional areas in the natural reserve of the YRD (the core area, buffer area, and experimental area) and a neighboring area of the natural reserve. The total concentrations, speciations, contamination status, and health risk assessments of the mercury (Hg) and arsenic (As) in surface soils of the YRD were investigated. The average Hg concentration was about three times that of the background value, while As was just slightly higher than the background. Hg levels in the sites of experimental area were significantly higher than those in the core area and buffer area, which was consistent with the human activity intensities of the three functional areas. However, no significant differences of As levels were observed across different areas. According to the sequential extraction experiments, only less than 5% of Hg and As were associated with the exchangeable fraction, while over 80% of them were found in the residual fraction, indicating low mobility and bioavailability of both Hg and As. The soil contamination status assessments suggested a "good state," and the health risk assessments indicated a "low risk" of Hg and As in the soils of YRD

Geochemical normalization and assessment of heavy metals (Cu, Pb, Zn, and Ni) in sediments from the Huaihe River, Anhui, China

Fifty-four surface sediment samples were collected in July 2013, from the Huaihe River (Anhui Province) in eastern China, which flows through Shouxian, Fengtai and Huaiyuan counties and Huainan city. The total Cu, Pb, Zn, Ni, Al and Fe concentrations were determined using an inductively coupled plasma-optical emission spectrometer (ICP-OES). Heavy metal geochemical normalization with Al was utilized to minimize the natural metal variability in the sediments before the metal enrichment was evaluated. Moreover, the predicted and maximum Cu, Pb, Zn and Ni natural concentrations were obtained using a linear regression model. A modified geoaccumulation index, where the regional background value was substituted with the predicted natural metal concentrations, was used to assess heavy metal contamination. Zn exhibited the most substantial contamination, followed by Pb, Cu, and Ni. Furthermore, the high Pb concentrations are likely attributed to exhaust discharged by automobile or ships, and coal combustion flue gas deposition, the latter of which may also be the source of Zn. Copper and Ni originate mainly from natural sources, with only a small anthropogenic contribution. (C) 2015 Elsevier B.V. All rights reserved.</p

Characterization of the Origin of Polycyclic Aromatic Hydrocarbons in Sediments from the Yellow River Estuary, China

Polycyclic aromatic hydrocarbons (PAHs) are organic contaminants that are widespread in the environment. A knowledge of their sources is of great significance for effective pollution control. In the present study, 23 PAHs were determined in surface sediments collected from the Yellow River Estuary, China. Potential toxicity analysis indicated that four dibenzopyrene isomers were the major carcinogenic contributors of the PAHs in the study area, underlining the importance of determining these compounds in future analysis. Principal component analysis combined with multiple linear regression and positive matrix factorization were used with diagnostic ratios to identify possible sources of PAHs in the sediments. Coal, biomass, and petroleum combustion were identified by these methods. However, the diagnostic ratios only offered a qualitative reference, and there were differences between the relative contributions estimated by principal component analysis/multiple linear regression and positive matrix factorization. The results suggest that positive matrix factorization is preferred, but more convincing results may be obtained by applying multiple methods to the same data set to more definitively identify PAH sources

Tracking historical mobility behavior and sources of lead in the 59-year sediment core from the Huaihe River using lead isotopic compositions

A historical perspective of past 59 years (1955-2014) for contamination and isotopic composition of Pb in sediment core system of the Huaihe River, Huainan City, Anhui Province of China is presented. Detailed investigation regarding changes in Pb sources, enrichment factor, sequential extraction and isotopic analysis revealed that high Pb concentrations were detected along the core, especially during the first two decades (1955-1974). Large variations in Pb isotopic compositions were observed, with Pb-206/Pb-207 and Pb-208/Pb-207 values ranging from 1.1504-1.1694, and 2.0817-2.1380, respectively. Diverse Pb sources were identified for sediment contamination over the time. Among anthropogenic sources, metallurgic dust and leaded petrol were on top during 1955-1974, especially when the Great Leap Forward Movement (1958-1960) was in progress in China, the time numerous small industries were established without wastewater treatment facility. However, coal and coal combustion were recognized as the primary sources of Pb emissions for the recent four decades (1974-2014) due to tremendous increase of coal consumption for power and heat generation. Unleaded vehicle exhaust, waste incineration and industrial emission were also sources of Pb during the years 1974-2014. Our estimates based on geochemical and lead isotopic approaches have shown that anthropogenic Pb contributions varied from 4.35 to 92.01%, and 13.28-99.06%, respectively. Assessment of lead speciation indicated an overwhelming presence of reducible fraction (Fe-Mn hydro-(oxides)) in the sediment core, except during 1995-1997, which was thought to be affected by water pollution accidents caused by heavy rainfall. (C) 2017 Elsevier Ltd. All rights reserved

Fractional distribution and risk assessment of heavy metals in sediments collected from the Yellow River, China

Bohai Sea is one of the most intensively exploited region in the world and its environment has been severely impacted by the extensive human activities. The Yellow River is the most important river which connects with the Bohai Sea. Therefore, this study focused on analyzing heavy metals (HMs) in 21 surface sediment samples collected from the Yellow River, China. Sequential extraction procedure (SEP), proposed by the Community Bureau of Reference (BCR), was applied in the present study to determine the concentration and fractionation characteristics of these HMs. The aim of this study was to investigate the spatial distribution, fractionation, risk assessment, and sources of HMs, including copper (Cu), zinc (Zn), lead (Pb), chromium (Cr), iron (Fe), manganese (Mn), and nickel (Ni). The results obtained from this research will play a significant role in understanding the migration, transformation, and accumulation of HMs for future research in study area. Results of fractionation revealed that most of the HMs in the study area mainly existed in residual fraction; however, Mn mostly existed in exchangeable fraction. A high percentage of reducible fractions was found for Cu and Pb. The mean contamination factor (C-f) values indicated that Pb was the highest. It was &gt; 1 and showed moderate contamination, followed by Cr, Cu, Mn, Ni, and Zn, had &lt; 1 and indicated low contamination. Among studied HMs Pb had higher enrichment factor (EF) as compared to others. Significant positive correlations within all studied HMs and principal component analysis (PCA) results indicated their common sources, however, Pb showed the different contamination sources. The total contents of HMs in sediment were compared with the threshold effect level (TEL) and probable effect level (PEL) sediment quality guideline (TEL/PEL-based SQGs) values for trace metals in sediment, as well as literature reported data for comparative purposes, which indicated that the selected river in present study is not severe