Soil's Hidden Power: The Stable Soil Organic Carbon Pool Controls the Burden of Persistent Organic Pollutants in Background Soils.

Persistent organic pollutants (POPs) tend to accumulate in cold regions by cold condensation and global distillation. Soil organic matter is the main storage compartment for POPs in terrestrial ecosystems due to deposition and repeated air-surface exchange processes. Here, physicochemical properties and environmental factors were investigated for their role in influencing POPs accumulation in soils of the Tibetan Plateau and Antarctic and Arctic regions. The results showed that the soil burden of most POPs was closely coupled to stable mineral-associated organic carbon (MAOC). Combining the proportion of MAOC and physicochemical properties can explain much of the soil distribution characteristics of the POPs. The background levels of POPs were estimated in conjunction with the global soil database. It led to the proposition that the stable soil carbon pools are key controlling factors affecting the ultimate global distribution of POPs, so that the dynamic cycling of soil carbon acts to counteract the cold-trapping effects. In the future, soil carbon pool composition should be fully considered in a multimedia environmental model of POPs, and the risk of secondary release of POPs in soils under conditions such as climate change can be further assessed with soil organic carbon models.

First comprehensive assessment of dietary chlorinated paraffins intake and exposure risk for the rural population of the Tibetan Plateau, China.

Knowledge regarding the occurrence of short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) in foodstuffs and their dietary exposure risks for rural Tibetan residents remains largely unknown. Herein, we collected main foodstuffs (including highland barley, vegetables, Tibetan butter, mutton, and yak beef) across the rural Tibetan Plateau and characterized the CP profiles and concentrations. The highest SCCPs concentrations were detected in Tibetan butter (geometric mean (GM): 240.6 ng/g wet weight (ww)), followed by vegetables (59.4 ng/g ww), mutton (51.4 ng/g ww), highland barley (46.3 ng/g ww), and yak beef (31.7 ng/g ww). For MCCPs, the highest concentrations were also detected in Tibetan butter (319.5 ng/g ww), followed by mutton (181.9 ng/g ww), vegetables (127.0 ng/g ww), yak beef (71.2 ng/g ww), and highland barley (30.3 ng/g ww). The predominant congener profiles of SCCPs were C13Cl7-8 in mutton and yak beef, C10Cl7-8 in Tibetan butter, and C10-11Cl6-7 in highland barley and vegetables. The predominant congener profiles of MCCPs were C14Cl7-9 in all sample types. Combined with our previous results of free-range chicken eggs, the median estimated daily intakes (EDIs) of SCCPs and MCCPs via diet for Tibetan rural adults and children was estimated to be 728.8 and 1853.9 ng/kg bw/day and 2565.6 and 5952.8 ng/kg bw/day, respectively. In the worst scenario, MCCPs might induce potential health risks for rural Tibetan population. To our knowledge, this is the first systematic dietary exposure research of SCCPs and MCCPs in the remote rural areas.

Remarkable Contamination of Short- and Medium-Chain Chlorinated Paraffins in Free-Range Chicken Eggs from Rural Tibetan Plateau.

Rapid social-economic development introduces modern lifestyles into rural areas, not only bringing numerous modern products but also new pollutants, such as chlorinated paraffins (CPs). The rural Tibetan Plateau has limited industrial activities and is a unique place to investigate this issue. Herein we collected 90 free-range chicken egg pool samples across the rural Tibetan Plateau to evaluate the pollution status of CPs. Meanwhile, CPs in related soils, free-range chicken eggs from Jiangxi, and farmed eggs from markets were also analyzed. The median concentrations of SCCPs (159 ng g-1 wet weight (ww)) and MCCPs (1390 ng g-1 ww) in Tibetan free-range chicken eggs were comparable to those from Jiangxi (259 and 938 ng g-1 ww) and significantly higher than those in farmed eggs (22.0 and 81.7 ng g-1 ww). In the rural Tibetan Plateau, the median EDI of CPs via egg consumption by adults and children were estimated to be 81.6 and 220.2 ng kg-1 bw day-1 for SCCPs and 483.4 and 1291 ng kg-1 bw day-1 for MCCPs, respectively. MCCPs might pose potential health risks for both adults and children in the worst scenario. Our study demonstrates that new pollutants should not be ignored and need further attention in remote rural areas.

Integrated Omics Approach to Discover Differences in the Metabolism of a New Tibetan Desmodesmus sp. in Two Types of Sewage Treatments.

Microalgae are now widely applied in municipal (YH_3) and industrial sewage (YH_4) treatments. Through integrated omics analysis, we studied the similarities and differences at the molecular level between the two different types of sewage treatment processes. The most significantly enriched gene ontology (GO) terms in both types of sewage treatments were the ribosome, photosynthesis, and proteasome pathways. The results show that the pathways of differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) were enriched for photosynthesis, glyoxylate and dicarboxylate metabolism, and carbon fixation in photosynthetic organisms. Considering YH_3 vs. YH_4, the metabolism of citrate, sedoheptulose-7P, and succinate was significantly upregulated. In addition, the results showed that the pathways of DEGs and DAMs were enriched in terms of amino acid metabolism and carotenoid biosynthesis in YH_4 vs. YH_3. The metabolism of S-Adenosyl-L-homocysteine was significantly downregulated, 2-oxobutanoate was significantly upregulated and downregulated, and the metabolism of abscisic acid glucose ester (ABA-GE) was also significantly upregulated. Overall, the results of this paper will help to improve the basic knowledge of the molecular response of microalgae to sewage treatments, and help design a response strategy based on microalgae for complex, mixed sewage treatments.

Environmental, economic, and energy analysis of municipal solid waste incineration under anoxic environment in Tibet Plateau.

The first Municipal solid waste incineration (MSWI) plant in Lhasa, Tibet, the plateau region of China, started its operation in 2018. Considering the elevation and extreme climate (low pressure and low oxygen content) in Tibet, noticeable differences may be envisaged compared to MSWI elsewhere. The aim of this study is to evaluate the environmental impacts, economic benefits, and energy efficiency of this MSWI project with three representative MSWI case in plain region using Life cycle assessment (LCA), Cost-benefit analysis (CBA), and energy analysis methods. The result showed that enhancing blast volume and cross-sectional area of the boiler help adapt to the oxygen-deficient environment. GaBi model was employed based on the CML 2001 methodology to perform LCA. LCA shows that the Lhasa MSWI project has lower positive environment impacts than the projects in plain region. More attention is needed for the deficiencies in flue gas emissions of MSWI in the plateau region. CBA shows that the payback period is 11.97 years and the internal rate of return is 8.75%. The energy analysis indicates that the boiler energy efficiency is up to 81.92%. MSWI subject to minor changes seems suitable to Tibetan plateau, and can be deployed further.

A new Desmodesmus sp. from the Tibetan Yamdrok Lake.

Revegetation of exposed sub-soil, while a desirable recovery strategy, often fails due to extreme soil chemical properties, such as low organic matter and pH levels. Microalgae play a key role in maintaining water quality in the lakes and rivers on the Qinghai-Tibet plateau. Plateau microalgae have extensive application prospects in environmental purification, biotechnology, medicine and cosmetics, food industry, and renewable energy. To identify the high biomass of microalgae present in nature, microalgae with the greatest biomass were screened from natural water samples through filtration, pre-culture, and plate scribing separation. Following identification via 18S rRNA sequencing as for the Desmodesmus sp., we constructed a neighbor-joining phylogenetic tree. The novel Desmodesmus sp. from the Tibetan Yamdrok Lake were identified through polyphasic taxonomy. Simultaneously, the sequence of the experimental samples and the target species were shown different following the identification and analysis of SNP and InDel loci. The light-absorbing properties of plateau Desmodesmus sp. have been investigated previously. The characteristic absorption peak of Desmodesmus sp. on the plateau was measured at 689 nm in the visible spectrum using full wavelength scanning with a UV-Vis spectrophotometer. For Desmodesmus sp. which is prone to settling in the process of amplification culture. By monitoring the change trend of total nitrogen, total phosphorus, pH and electrical conductivity in algae solution system, we determined that the logarithmic growth phase and the best transfer window of Desmodesmus sp. were at 15-20 days. This study can provide basic research methods for the study of microalgae in high altitude areas, and lay a foundation for the later study and application of microalgae.

Short-Chain Fatty Acids Production from Anaerobic Fermentation of Sewage Sludge: The Effect of Higher Levels Polyaluminium Chloride.

With the annual increase in the sludge production in China's sewage treatment plants, the problem of sewage sludge treatment and disposal is becoming more and more serious. Anaerobic fermentation can convert complex organic matter in sewage sludge into short-chain fatty acid, hydrogen, methane and other resources and is an effective method for sewage sludge treatment and disposal. At the same time, sewage sludge often contains flocculants, which will inevitably affect the effect of anaerobic fermentation. As a high-performance flocculant, polyaluminum chloride (PAC) is widely used in wastewater treatment and sewage sludge dewatering processes. Previous studies indicated that lower levels of PAC inhibit the effect of the anaerobic fermentation process of sewage sludge; on the other hand, it is necessary to understand the effects of higher levels of PAC in anaerobically fermented sewage sludge. The results showed that higher levels (0.2-1 g Al/g total solids (TS)) of PAC could promote acid production from anaerobically fermented sewage sludge. Moreover, mechanism studies suggest that higher levels (0.2-1 g Al/g total solids (TS)) of PAC caused excessive adsorption of the charge on the surface of the sewage sludge colloid and reversed the charge. The sewage sludge colloid was stabilized again, which increases the concentration of soluble proteins, polysaccharides, and soluble extracellular polymers (S-EPS) in the fermentation broth, thereby improving the anaerobically fermented sewage sludge efficiency. The results provided from this study may act as technical reference and guidance for the engineering application of sewage sludge anaerobic fermentation.

Tracing the Transboundary Transport of Mercury to the Tibetan Plateau Using Atmospheric Mercury Isotopes.

Deposition of atmospheric mercury (Hg) is the most important Hg source on the high-altitude Himalayas and Tibetan Plateau. Herein, total gaseous Hg (TGM) at an urban and a forest site on the Tibetan Plateau was collected respectively from May 2017 to October 2018, and isotopic compositions were measured to clarify the influences of landforms and monsoons on the transboundary transport of atmospheric Hg to the Tibetan Plateau. The transboundary transported anthropogenic emissions mainly originated over Indo-Gangetic Plain and carried over the Himalayas by convective storms and mid-tropospheric circulation, contributing over 50% to the TGM at the Lhasa urban site, based on the binary mixing model of isotopes. In contrast, during the transport of TGM from South Asia with low altitude, the uptake by evergreen forest in Yarlung Zangbo Grand Canyon largely decreased the TGM level and shifted isotopic compositions in TGM at the Nyingchi forest site, which are located at the high-altitude end of the canyon. Our results provided direct evidence from Hg isotopes to reveal the distinct patterns of transboundary transport to the Tibetan Plateau shaped by landforms and climates, which is critical to fully understand the biogeochemical cycling of Hg in the high-altitude regions.

Gangba sheep in the Tibetan plateau: Validating their unique meat quality and grazing factor analysis.

Gangba sheep are known for having typical sensory characteristics attributed to free range conditions and grazing on wild plants. The genuine Gangba mutton was selected as the experimental group, and the commercial Tibetan mutton was selected as the control group, the nutritive composition of basic chemical components, amino acids and fatty acids in mutton were investigated to correlate its unique meat quality and eating satisfaction. The results showed that fatty acids were significantly higher (P<0.05) in Gangba mutton than in commercial mutton, and the higher content of flavoring amino acids (glutamic acid and aspartame) were primarily responsible for the taste attributes umami of meat juices. Moreover, the trace elements analysis in mutton and grazing factors (forage, water source and soil) were conducted, to explain the source of essential trace elements in mutton. The concentrations of essential trace elements show that the Gangba mutton was a valuable source for highly available Cu and Zn in human nutrition, and well managed with few detected of toxicity metal. The concentrations of essential trace elements in mutton are closely related to the trace elements in environmental grazing factors. In conclusion, the congenital grazing conditions (a highly mineralized water resource, natural forages and clean soils) were shown to contribute to the unique meat characteristics of Gangba sheep.

Long-range atmospheric transport and alpine condensation of short-chain chlorinated paraffins on the southeastern Tibetan Plateau.

Pristine alpine regions are ideal regions for investigating the long-range atmospheric transport and cold trapping effects of short chain chlorinated paraffins (SCCPs). The concentrations and alpine condensation of SCCPs were investigated in lichen samples collected from the southeastern Tibetan Plateau. The concentrations of SCCPs ranged from 3098 to 6999 ng/g lipid weight (lw) and appeared to have an increasing trend with altitude. For congeners, C10 dominated among all the congener groups. The different environmental behavior for different congener groups was closely related to their octanol-air partition coefficient (Koa). C10 congeners showed an increasing trend with altitude, whereas C13 congeners were negatively correlated with altitude. Volumetric bioconcentration factors (BCF) of SCCPs reached 8.71 in lichens, which were higher than other semivolatile organic compounds (SVOCs) such as organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and hexabromocyclododecane (HBCD). These results suggested that SCCPs were prone to accumulate in the lichen from the air and provided evidence for the role of lichens as a suitable atmospheric indicator in the Tibetan Plateau.

Terrestrial mercury transformation in the Tibetan Plateau: New evidence from stable isotopes in upland buzzards.

Understanding the geochemical cycle of mercury (Hg) in the high-altitude Tibetan Plateau is of great value for studying the long-range transport of Hg. Herein, speciation and isotopic compositions of Hg in the muscle and feathers of upland buzzards (Buteo hemilasius) were studied to trace the terrestrial transformation of Hg in the Tibetan Plateau. Very low Hg content and relatively low δ202Hg values (feather: -0.77 ± 0.50‰, n = 9, muscle: -1.29 ± 0.29‰, n = 13, 1SD) were observed in upland buzzards. In contrast, the Δ199Hg values could be as high as 2.89‰ in collected samples. To our knowledge, this is the highest Δ199Hg value reported in avian tissues. Moreover, upland buzzards showed significantly different Δ199Hg values from fish collected from the same region, suggesting different generation and transformation processes of methylmercury (MeHg) in terrestrial and aquatic ecosystems. We speculated that different percentages of Hg undergoing photochemical reactions and contributions of atmospheric MeHg were possible reasons for observed differences. The results provide new clues for different circulation histories of Hg in terrestrial and aquatic ecosystems, which will be critical for further study of geochemical cycle and ecological risk of Hg in the environment.

New classes of organic pollutants in the remote continental environment - Chlorinated and brominated polycyclic aromatic hydrocarbons on the Tibetan Plateau.

Halogenated polycyclic aromatic hydrocarbons are carcinogenic and ubiquitous environmental organic pollutants. The abundance and sources of these compounds have not been studied in remote environments. We collected and analyzed air, soil, lichen, and moss samples from the Tibetan Plateau. Concentrations of chlorinated polycyclic aromatic hydrocarbons were 0.78-4.16 pg/m3 in air, 3.11-297 pg/g in soil, 260-741 pg/g in lichens, and 338-934 pg/g in mosses. Concentrations of brominated polycyclic aromatic hydrocarbons were 0.15-0.59 pg/m3 in air, 0.61-72.3 pg/g in soil, 33.5-64.9 pg/g in lichens, and 20.5-72.5 pg/g in mosses. The dominant congeners were 9- and 2-chlorophenanthrene, 1-chloropyrene, 3-chlorofluoranthene, and 1-bromopyrene. We found correlations between congener concentrations in lichens and in air, and lichens effectively predicted near-ground atmospheric concentrations of the pollutants. The enrichment of photochemically stable compounds in high-altitude environments is influenced by their physicochemical properties. Principal component analysis with multivariate linear regression of chlorinated polycyclic aromatic hydrocarbons measured in lichens provided an assessment of the relative source contributions, and suggested that in Medog County of Tibetan Plateau, 48% was likely from long-range combustion sources, 26% was from local burning sources, and 26% was from photochemical formation.

Trophic Dilution of Short-Chain Chlorinated Paraffins in a Plant-Plateau Pika-Eagle Food Chain from the Tibetan Plateau.

Little is currently known about the trophic transfer behavior of short-chain chlorinated paraffins (SCCPs) in terrestrial ecosystems. The trophodynamics of SCCPs were investigated in a typical terrestrial food chain (plant-plateau pika-eagle) from the interior of the Tibetan Plateau with an altitude of 4730 m. Pervasive contamination by SCCPs was found in the Tibetan Plateau samples, and the average concentrations of SCCPs in soil, plant, plateau pika, eagle, and gut content of eagle samples were 81.6 ± 31.1, 173 ± 70.3, 258 ± 126, 108 ± 59.6, and 268 ± 93.9 ng/g (average ± standard deviation, dry weight, dw), respectively. The trophic magnification factor (TMF) of SCCPs was 0.37, implying the trophic dilution of SCCPs in this terrestrial food chain. The TMF values of individual congener groups were positively correlated with the values of log Kow, log Koa and biotransformation half-life. As a result of long-range transport, SCCPs congeners with low molecular weight dominated in Tibetan Plateau species (C10+11 congeners = 76.9%, Cl5+6+7 congeners = 71.5%), which could partly explain the low biomagnification factors (BMFs) of SCCPs in the Tibetan Plateau.