Mercury isotopic compositions of mosses, conifer needles, and surface soils: Implications for mercury distribution and sources in Shergyla Mountain, Tibetan Plateau.

Understanding the distribution and sources of mercury (Hg) in the Tibetan Plateau is of great value to study the long-range transport of Hg. Herein, the total Hg (THg) concentrations and the isotopic compositions of mosses, conifer needles, and surface soils collected from both slopes of the Shergyla Mountain of Tibetan Plateau were analyzed. The contents of THg in samples (except mosses on the eastern slope) were significantly positively correlated with altitude in both the western and eastern slopes, possibly caused by topographic factors. In contrast, Δ199Hg in samples was significantly negatively correlated with altitude. On the basis of Hg isotopic compositions, atmospheric Hg0 uptake was indicated as the primary accumulation pathway of Hg in mosses (Δ199Hg: -0.12 ±â€¯0.09‰, -0.26 - 0.00‰, 1 SD, n = 10) and conifer needles (Δ199Hg: -0.21 ±â€¯0.08‰, -0.36 - -0.11‰, 1 SD, n = 9). Moreover, the contributing fractions of atmospheric Hg0 to Hg in surface soils (Δ199Hg: -0.20 ±â€¯0.07‰, -0.31 - -0.06‰, 1 SD, n = 17) increased with altitude and accounted for an average of 87 ± 9% in atmospheric sources. Due to the special geographic positions and environmental conditions of the Tibetan Plateau, the results of this study were essential for further understanding the long-range transport and global cycling of Hg.

Characterization and speciation of mercury in mosses and lichens from the high-altitude Tibetan Plateau.

The accumulation and species of mercury (Hg) in mosses and lichens collected from high-altitude Tibetan Plateau were studied. The altitudes of the sampling sites spanned from 1983 to 5147 m, and a total of 130 mosses and 52 lichens were analyzed. The total mercury (THg) contents in mosses and lichens were in the ranges of 13.1-273.0 and 20.2-345.9 ng/g, respectively. The average ratios of methylmercury (MeHg) in THg in mosses and lichens were 2.4 % (0.3-11.1 %) and 2.7 % (0.4-9.6 %), respectively, which were higher than those values reported in other regions. The contents of THg in both mosses and lichens were not correlated with the THg in soils (p > 0.05). The lipid contents displayed a significantly positive correlation with concentrations of MeHg in mosses (r = 0.461, p < 0.01, n = 90), but not in lichens. The correlations between Hg contents in mosses and the altitudes, latitudes and longitudes of sampling sites indicated the mountain trapping and spatial deposition of Hg in the Tibetan Plateau.

[Distribution and Source Analysis of Polycyclic Aromatic Hydrocarbons (PAHs) and Organochlorine Pesticides (OCPs) in Soils from Shergyla Mountain, Southeast Tibetan Plateau].

Soils were collected from Shergyla Mountain shade slope and south-facing slope in southeast Tibetan Plateau (TP) in August 2012 and they were measured for polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs)(including HCHs and DDTs). The concentrations of ∑16PAHs ranged from 99.3 to 1984 ng·g-1 dw, with a mean value of 1017 ng·g-1 dw. HCHs and DDTs in soils samples were in the range of 0.37-2.07 ng·g-1 dw (mean 1.15 ng·g-1 dw) and 0.70-43.9 ng·g-1 dw (mean 9.87 ng·g-1 dw), respectively. The concentrations of all measured compounds were much higher than those in central or western TP,and the PAHs concentration was even up to two orders of magnitude. The concentrations of α-HCH and DDTs in south-facing slope increased with altitude, but HCHs and DDTs in shade slope had no significant correlation with altitude. There was no consistent increasing or decreasing trend of PAHs in shade slope with altitude, and the concentrations of PAHs in south-facing slope showed a higher value in lower altitude, indicating the existence of local pollution emissions. The PAHs profile was dominated by lighter constituents (2 & 3-ring accounted for higher than 85%),inferring that the PAHs in the study area were largely influenced by long range atmospheric transport (LRAT) of pollutants. The special diagnostic ratios of PAHs suggested that PAHs were mainly produced by low temperature combustion of biomass and fossil fuels, except that two sampling sites of shade slope had been possibly influenced by oil residue. The relatively low ratios of α/γ-HCH inferred HCHs in the research area was the result of the combined contribution of the historical technical HCHs and Lindan. The ratios of p,p'-DDE/p,p'-DDT and o,p'-DDT/p,p'-DDT indicated DDTs were from the combined contribution of the historical technical DDTs and dicofol. According to the profile of PAHs, HCHs and DDTs and the meteorological conditions of Shergyla Mountain, the transport of PAHs and OCPs in the study area was mainly influenced by the Indian Monsoon.

[Contamination levels and source analysis of polycyclic aromatic hydrocarbons and organochlorine pesticides in soils and grasses from lake catchments in the Tibetan Plateau].

Soils and grasses samples were collected from 6 typical lake catchments in the central and northern Tibetan Plateau (TP) in August 2007 and analyzed for polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs, including HCHs and DDTs). The concentrations of sigma16 PAHs, sigma HCHs and sigma DDTs in soil samples were in the range of 60.6-614 ng x g(-1) (mean 194 ng x g(-1)), 0.06-0.74 ng x g(-1) (mean 0.31 ng x g(-1)) and N. D. -0.17 ng x g(-1) (mean 0.07 ng x g(-1)) while those of sigma15 PAHs (excluding NAP), sigma HCHs and sigma DDTs in grasses were in the range of 262-519 ng x g(-1) (mean 327 ng x g(-1)), 0.55-3.92 ng x g(-1) (mean 2.17 ng x g(-1)) and 0.20-2.19 ng x g(-1) (mean 0.92 ng x g(-1)), respectively. All compounds were significantly lower than those in European high mountains. The biological concentration effect of grasses to soils was notable with the values of BCF ranging from 4.2 to 19.3. No significant correlations were observed between the concentrations of POPs and the content of OM/lipid, or the altitude of the sampling sites. The PAHs profile was dominated by lighter constituents (2 & 3-ring PAHs accounted for higher than 80%). The special diagnostic ratios of PAHs suggested that PAHs in the TP were mainly produced by low-temperature combustion of biomass and fossil fuels, and the relatively low ratios of alpha/gamma-HCH and high ratios of o,p'-DDT/p,p'-DDT implied that the wide applications of lindane and dicofol contributed to the OCPs contamination in the TP. According to the backward airmass trajectory models, it was deduced that the westerly wind was the main source for both central and northern sites in the TP during winter. During summer, pollutants in the central sites of the TP were mainly from the Indian subcontinent while the northern sites were also affected by Chinese inland provinces.

[Vertical distribution pattern and ecological risk assessment of heavy metals in a sediment core from Pumoyum Co, Tibet].

The sediment core was collected in Pumoyum Co, a lake located in southern Tibetan Plateau, in July 2008. Samples were digested using microwave equipment and analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), to determine the content of heavy metals in the sediments. The average concentrations for Cr, Co, Ni, Cu, Zn, Cd, Pb, Mn and Fe were 26.4 µg x g(-1), 6.64 µg x g(-1), 16.2 µg x g(-1), 26.2 µg x g(-1), 50.2 µg x g(-1), 0.363 µg x g(-1), 16.8 µg x g.(-1), 0.302 mg x g(-1) and 9.84 mg x g(-1) , respectively. The concentrations of analysed metals in Pumoyum Co were slightly higher than those in Antarctic, but lower than those from Dianchi in Yunnan, Daihai in Inner Mongolia, the Great lakes in North America and Taihu in China, which were obviously affected by anthropogenic activities. Overall, these metals in sediments from Pumoyum Co represented a low concentration level. Vertical profiles of heavy metals in the sediment core kept stable without large fluctuation and the concentrations in surface slices were relatively higher. Results of principle component analysis and cluster analysis indicated that organic matter and Mn were affected by surface runoff markedly while other metals were mainly correlated to natural diagenetic weathering and atmospheric deposition. Sediment quality guideline and potential ecological risk index were introduced to assess sediment quality and both of their results indicated that the Pumoyum Co as a whole can be ranked as low potential ecological risk.

[Study on the contamination status of butyltins in Taihu Lake].

Butyltins in surface water, sediments and biota samples from Taihu Lake were determined. The results show that butyltins content in most of the surface water samples is under the limit of the detection; five out of ten sediment samples are measured detectable butyltins. Monobutyltin (MBT) was the main species with the concentrations ranging from below the detection limits to 0.95 ng/g; while all biota samples were detected relatively higher butyltin concentrations with a range of 27.05 - 181.23 ng/g due to the obvious bioaccumulation. Tributyltin (TBT) was the main composition that occupied almost 70% of the total butyltins. The antifouling paints applied on the aquatic cultural box and boats was the possible main source of butyltin compounds in Taihu Lake.

Butyltin accumulation in the marine clam Mya arenaria: an evaluation of its suitability for monitoring butyltin pollution.

The use of Mya arenaria as a new sensitive biomonitor of butyltins pollution in the oceanic system was investigated. Field survey indicated that much higher levels of butyltin compounds were found in M. arenaria compared with the other species investigated. Using Mytilus edulis as a control organism, a 28 days exposure of tributyltin chloride (TBT) to M. arenaria for accumulation and subsequent 28 days breeding in clean seawater for elimination were conducted under laboratory conditions in order to confirm its high accumulation ability and characterize its kinetic behavior to TBT. Bioconcentration factor (BCF) of M. arenaria ranged from 15,538 to 91,800 after 28 days exposure. The rapid uptake and low rate to eliminate TBT of M. arenaria displayed first-order kinetics. M. arenaria shows potential as a new bioindicator to monitor TBT pollution in marine environment.

The levels and distribution of organochlorine pesticides (OCPs) in sediments from the Haihe River, China.

The levels and distribution patterns of the selected organochlorine pesticides (OCPs=p,p'-DDT, o,p'-DDT, p,p'-DDE, p,p'-DDD, alpha-, beta-, gamma- and delta-HCH) in surficial sediments from the Haihe River and Dagu Drainage River of Tianjin were investigated by means of gas chromatography coupled with micro-electronic capture detector (GC-microECD). Concentrations of OCPs in the sediments from the Haihe River ranged from 1.88 to 18.76ng g(-1) (mean 7.33ng g(-1)) for sum HCH, 0.32-80.18ng g(-1) (mean 15.94ng g(-1)) for sum DDT. Compared with the Haihe River, the Dagu Drainage River was much more contaminated by HCHs and DDTs, wherein sum HCH ranged from 33.24 to 141.03ng g(-1) (mean 87.74ng g(-1)) and sum DDT ranged from 3.60 to 83.49ng g(-1) with a mean value of 35.52ng g(-1). The concentration distribution of sum DDT and sum HCH was different indicated their different contamination sources. Composition analyses indicated that a recent usage or discharge of HCH and DDT into the Dagu Drainage River.

Occurrence and distribution of organochlorine pesticides (HCH and DDT) in sediments collected from East China Sea.

Sediments used in this study were collected from different depths of eight sites in East China Sea in November 2002. The levels and distribution patterns of the selected organochlorine pesticides (OCPs=p,p'-DDT, o,p'-DDT, p,p'-DDE, p,p'-DDD, alpha-, beta-, gamma- and delta-HCH) in samples were investigated by the technique of sonication extraction followed by the analysis of gas chromatography (GC) coupled with a micro-electron capture detector (muECD). The concentrations of SigmaHCH and SigmaDDT in the surface sediments were in the range of <0.05-1.45 ng/g (mean 0.76 ng/g), <0.06-6.04 ng/g (mean 3.05 ng/g) based on dry weight (dw), respectively. In the vertical distributions, the SigmaHCH and SigmaDDT were in the range of <0.05-2.52 ng/g, <0.06-10.94 ng/g dw, respectively. Residues of OCPs varied significantly with different sampling sites. SigmaDDT in the surface sediments was correlated well with total organic carbon (TOC) content (r2=0.71), while SigmaHCH showed no obvious correlation. The distribution showed that the sediments from the vicinity estuary or near shore had higher TOC contents, and higher OCPs concentrations. The contamination record indicated an extensive use of OCPs in the catchments from Yangtze River in the past might greatly affect the OCP residues.