•The 5- and 6-methyl brGDGTs in soils from an altitudinal transect were investigated.•The 6-methyl brGDGTs in the soils were pH-dependent.•A new liquid chromatography method was used to separate 5- ...and 6-methyl isomers.•Two new isomers of tetramethylated brGDGTs were found.•Global calibrations of IRIIIa′ and IRIIa′ for soil pH reconstruction are proposed.
The methylation index (MBT or MBT′) of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in soils along altitudinal transects of some mountains, e.g. Mount (Mt.) Shennongjia and Mt. Gongga, exhibited no correlation with altitude or mean annual air temperature (MAT) alone. However, a significant correlation between MBT′, cyclization ratio (CBT) of brGDGTs and MAT for each transect could still be found. To investigate the reason, we reanalyzed the brGDGTs in soils from Mt. Shennongjia using an improved liquid chromatography method and examined whether the newly described 6-methyl brGDGTs were the main cause of the large scatter in the correlation between MBT′ and MAT. In contrast to MBT′, the MBT′5ME, based on 5-methyl brGDGTs alone, correlated significantly with MAT (R2 0.89, p<0.001) but had no relationship with soil pH. However, MBT′6ME, based only on 6-methyl brGDGTs, was strongly dependent on soil pH. This suggests that pH dependent 6-methyl brGDGTs introduce large scatter in the correlation between MBT′ and MAT, which is likely to mechanistically explain the poor relationship between MBT′ and MAT, yet good correlation between MBT′, pH and MAT. A series of indices derived from 6-methyl brGDGTs, including IRIIIa′ and IRIIa′ (isomer ratio of structures IIIa′ and IIa′, respectively), correlated with soil pH and can be used as new paleo pH indicators to supplement the classic CBT proxy. The tetramethylated brGDGTs with 0–1 cyclopentyl rings (Ia and Ib) were found to comprise unknown isomers, whose abundances also appear to increase with soil pH. A further optimized liquid chromatography method is needed to quantify these new isomers more accurately and to determine the environmental controls on them.
•Methyltrimethyltridecylchromans (MTTCs) analyzed in Bohai Basin oils biodegraded to various degrees (PM 1 to 8).•MTTCs are biodegradable being absent or nearly totally removed at PM = 8.•The rate of ...biodegradation increases with increasing methylation.•β/γ-MTTC, a maturity parameter, is affected by biodegration.•MTTCs-based paleosalinity parameters remain valid in this sample suite.
Methyltrimethyltridecylchromans (MTTCs), a class of aromatic hydrocarbon molecular marker compounds, provide an assessment of paleosalinity and maturity in sediments and crude oils. However, little is known about the effect of biodegradation on MTTCs. In this study, the saturated and aromatic fractions of a suite of oils from the Neogene Guantao (N1g) and Minghuazhen (N1m) Formation in the Miaoxi Depression, Bohai Bay Basin, were analyzed. Distriubutions of the more bioresistive biomarker show that the oils are derived from similar organic matter (dominantly from higher plants) and depositional environments (low salinity), and have similar maturity (in the middle oil window). Two biodegradation scales, were used to evaluate the level of biodegration. The samples ranged from PM 1 to 8 and MN2 from 140 to 983 (slight to heavy-severe biodegraded).
MTTC concentrations decrease with the increasing biodegradation levels and are or almost completely removed at PM = 8. The degree of alkylation affect their relative susceptibilities to biodegradation: trimethyl-MTTC (α-MTTC) > dimethyl-MTTCs (including β-MTTC, γ-MTTC and ζ-MTTC) > monomethyl-MTTC (δ-MTTC). The relative susceptibilities of dimethyl-MTTC isomers are γ-MTTC > β-MTTC > ζ-MTTC. The β/γ-MTTC, a maturity indicator, is significantly impacted by biodegradation. Paleosalinity inidcators, α/δ-MTTC, α/γ-MTTC, MTTCI and a ternary diagram of the relative abundance in different degree of alkylation of MTTCs, consistently indicate the oils are derived from sources deposited in a low samility environment. Additional research is needed to determine if biodegradation perturbs MTTC distributions in oils from other source environments to influence the inferred paleosalinity assessment.
Since the outbreak of 2019 novel coronavirus infection (2019-nCoV) in Wuhan City, China, by January 30, 2020, a total of 9692 confirmed cases and 15,238 suspected cases have been reported around 31 ...provinces or cities in China. Among the confirmed cases, 1527 were severe cases, 171 had recovered and been discharged at home, and 213 died. And among these cases, a total of 28 children aged from 1 month to 17 years have been reported in China. For standardizing prevention and management of 2019-nCoV infections in children, we called up an experts’ committee to formulate this experts’ consensus statement. This statement is based on
the Novel Coronavirus Infection Pneumonia Diagnosis and Treatment Standards (the fourth edition)
(National Health Committee) and other previous diagnosis and treatment strategies for pediatric virus infections. The present consensus statement summarizes current strategies on diagnosis, treatment, and prevention of 2019-nCoV infection in children.
Sediment microbial communities are responsible for many chemical biotransformation processes in the aquatic environment and play a critical role in various ecosystems and biogeochemical cycling. ...However, the impact of polyfluoroalkyl substances on sediment microbial communities remains unclear. These substances are increasingly being used in consumer and industrial products to replace environmentally persistent perfluoroalkyl substances. In this study, we investigated the effects of low (5mg/L) and high (15mg/L) doses of 6:2 fluorotelomer alcohol 6:2 FTOH, F(CF2)6CH2CH2OH on the structure of a sediment microbial community. 6:2 FTOH biotransformation was rapid in the sediment mixture with a half-life <3days, regardless of the initial doses. After 28days, major products produced in the high dose condition included 28mol% 5:2 sFTOH F(CF2)5CH(OH)CH3, 9.6mol% 5:3 Acid F(CF2)5CH2CH2COOH and 11mol% PFHxA F(CF2)5COOH, while 73mol% 5:2 sFTOH, 23mol% 5:3 Acid and 26mol% PFHxA were observed in the low dose condition. In the original (control) sediment without 6:2 FTOH dosing, Proteobacteria was the predominant microorganism (18%), followed by Chloroflexi (14%), Verrucomicrobia (13%), Firmicutes (3.4%), Bacterioidetes (2.4%), Actinobacteria (1.7%) and Planctomycetes (1.3%). The presence of 6:2 FTOH and the accumulation of transient transformation products in the sediment exerted selection pressure on the microbial taxonomic distribution and diversity. Our observations indicate that potential 6:2 FTOH degraders and tolerant strains, such as Dokdonella spp., Thauera spp., Albidovulum spp. and Caldanaerovirga spp., existed in the sediment mixture and began to dominate over time. This suggests that these genera might have higher tolerance towards elevated 6:2 FTOH and its transformation products. These findings on the characterization of sediment microbial community stability and dynamics will help predict changes in response to perfluoroalkyl and polyfluoroalkyl substances and also help identify robust microbial strains to degrade polyfluoroalkyl substances in the environment.
Display omitted
•6:2 FTOH was rapidly biotransformed in river sediment at both 5mg/L and 15mg/L doses.•6:2 FTOH and its major transformation products in the sediment impacted microbial taxonomic distribution and diversity.•Proteobacteria, Chloroflexi and Verrucomicrobia were the dominant microbes in the sediment.
In December 2019, a cluster of patients with severe pneumonia caused by a novel coronavirus (SARS‐CoV‐2) emerged in the city of Wuhan, China. The disease is now termed coronavirus disease 2019 ...(COVID‐19). In the early reports, the patients were mainly middle‐aged and elderly men, and children appeared to be less susceptible to this infection. With modern and efficient transportation, the disease quickly spread to almost all corners of the world and the mortality far exceeds that caused by severe acute respiratory syndrome (SARS) coronavirus or Middle East respiratory syndrome (MERS) coronavirus. As the number of children with COVID‐19 gradually increases, the disease has been documented in premature babies, infants, children, and adolescents. Severe and fatal cases in children are relatively rare. The burden of disease in children has been relatively low, but the high proportions of asymptomatic or mildly symptomatic infections in children deserve careful attention. A clear understanding of the immune responses to the virus in children and the transmission potential of asymptomatic children is of paramount importance for the development of specific treatments and vaccine in order to effectively control the ongoing pandemic.
The wide application of neonicotinoid insecticides in soil may affect soil microbial community, yet the information is limited. This study first reports the effects of thiamethoxam and dinotefuranon ...on soil microbial community. Soil from a forest land was collected and spiked with different nominal levels (0.02 mg kg−1, 0.2 mg kg−1 and 2.0 mg kg−1) of thiamethoxam and dinotefuran, respectively, and cultivated for 112 days. During the study, concentrations of the two neonicotinoids and their potential degradation products were monitored by LC-MS/MS. At day 112, the soils were analyzed for genetic profile by high-throughput sequencing and carbon metabolic profile by Biolog-ECO plate. The results showed that thiamethoxam and dinotefuran were both attenuated during the study with rate constants being 0.008–0.017 d−1 and 0.024–0.032 d−1, respectively, and biodegradation played an important role. As compared to the blank control, the exposure to the studied two neonicotinoids changed the microbial community, and the changes were influenced by both the type of neonicotinoid and the level of exposure. As compared to the blank control, the relative abundances of phyla Gemmatimonadetes and OD1 decreased under most exposed conditions, while the relative abundances of Chloroflexi and Nitrospirae increased under most exposed conditions. The community transition changed the functional potential, particularly carbon metabolism (mostly decreased) and nitrogen metabolism (mostly increased). As compared to the blank control, the utilization of total 31 carbon sources (including six categories) was increased under low exposure to thiamethoxam, but was decreased under all other exposed conditions. Low exposure to dinotefuran stimulated the utilization of three categories of carbon sources (amines, carbohydrates and phenolic compounds). Low exposure to both neonicotinoids increased the community diversity, while middle and high exposure to both neonicotinoids decreased the community diversity. These findings provide new insights into the effects of neonicotinoids on microbial community in soil.
Display omitted
•The persistence of thiamethoxam in soil was longer than that of dinotefuran.•Exposure to thiamethoxam and dinotefuran changed bacterial community genetically.•The genetic community transition changed the carbon source utilization profile.•Effect on soil microbial community was influenced by type and level of exposure.•Chloroflexi and Nitrospirae increased after exposure to both studied neonicotinoids.
Estuarine delta is a critical zone for a series of biogeochemical processes including greenhouse gas emissions, organic matter transport and burial. These processes are mainly mediated by microbial ...activities such as heterotroph, methanogenesis, and methanotroph. However, response of microbial activities in the delta to paleoenvironmental change is less constrained. In this study, we analyzed the concentrations and compositions of microbial ether lipids (branched GDGTs and isoprenoid GDGTs) in a core from the Liaohe Delta, the northeast China, to explore the response of bacteria and archaea communities to climate change since 32 ka BP. During the glacial periods, the concentrations of branched GDGTs and isoprenoid GDGTs were low possibly due to the low temperature inhibiting the growth of microorganisms. After the Last Glacial Maximum (LGM), the abundance of GDGT concentrations increased, and reached the maximum during the Bølling/Allerød (B/A) period, then decreased during the Younger Dryas (YD) and increased again during the early Holocene. This pattern indicated that the abundance of the microorganisms in the Liaohe Delta was mainly controlled by temperature since 32 ka BP. In addition to temperature, sea level fluctuation and local hydrological disturbance may also effect microbial growth in the Liaohe Delta. Significant increase in the ratio of GDGT-0 versus crenarchaeol (R0/5) indicates that the rise of lake level provided a favorable anaerobic environment for methanogen blooming during the B/A and the early Holocene. Low lake level and strong water mixing made oxygen content increase, thus inhibited methanogen growth and further led to the decrease of the R0/5 values in the YD, suggesting that methanogenesis in global estuaries may impact atmospheric methane content. Our results provide a means to interpret response of microbial abundance and biogeochemical processes to paleoclimate change since the Last Glacial Maximum in estuarine delta.
•The microbial abundance is closely related to temperature in LHD since 32 ka BP.•The methanogenetic processes in coastal wetland play an important role in atmospheric methane cycle.•GDGTs were invistigated in a sedimentary core collected from Liaohe Delta.
Sublacustrine fans developed in structurally active settings are commonly characterized by complicated depositional characteristics, which create great challenges to hydrocarbon exploration. To ...advance understanding their sedimentary architecture and depositional processes, a large-scale sublacustrine fan system in the Eocene Weixinan Depression, northern South China Sea has been identified and investigated through the comprehensive analysis of 3-D seismic, well-logging, and core data. This fan was deposited during a lake-level falling stage, covering an area of 55 Km2. It can be divided into two sections in the vertical direction by the sedimentary characteristics. The lower section mainly consists of thin layers of well-sorted fine sandstones with parallel bedding, which are interpreted as deposits of turbidity currents. By contrast, the upper section comprises thick layers of gravelly coarse sandstones with various deformation structures and widespread floating clasts, which should be the deposits of cohesive debris flows. Provenance analysis suggests that the development of complicated sedimentary characteristics has a close relationship with the occurrence of multiple sediment supply directions. The lower section was sourced by the western delta with long-distance transported well-sorted sediments, while the northern fan delta sourced the upper section with short-distance transported coarse-grained sediments. Its depositional process was mainly controlled by paleo-geomorphology, sediment supply, and relative lake level changes. The lower section, controlled by the flexure slope belt, is a typical sand-rich sublacustrine fan characterized by the low gradient (<1°–1.5°), while the upper section, controlled by the steep slope fault belt, is a gravel-rich sublacustrine fan dominated by intense faulting and high gradient (3.2°–4.5°). In addition, during the depositional period of the upper section, the relay ramps between en-echelon faults provided major entry points for coarse-grained sedimentary flows into the depression. Therefore, a deep-lacustrine model is proposed for the sublacustrine fan system, showing the detailed “triggering-transportation-deposition” process. This study outlines the complexity of the sedimentary architecture of sublacustrine fans in structurally active settings, and the proposed model may be applicable in other lacustrine basins.
•The sublacustrine fan is characterized by complicated sedimentary characteristics.•It consists of two types of gravity flows: cohesive debris flows and turbidity currents.•The development of complicated sedimentary characteristics is related to multi-source supply.•Its deposition process was controlled by small infections in gradient of paleo-slopes.•A deep-lacustrine model is proposed for sublacustrine fans in structurally active settings.
Recent time‐series from sediment traps show abnormally high chlorophyll‐a concentrations and primary productivity in the oligotrophic central South China Sea (SCS), especially during wintertime. Here ...we present new insights from compound‐specific hydrogen isotopic analysis of leaf wax n‐alkanes and Sr‐Nd isotope compositions extracted from four basin‐wide surface sediment transects. We find that the deepest surface sediments in the central basin contain the most depleted n‐alkane hydrogen isotopes, suggesting inputs from higher latitude soils in northern China. This is supported by the Sr‐Nd isotope compositions of the same surface sediments. We propose that aeolian dust is transported by the winter monsoon and might fertilize the phytoplankton bloom in the central SCS. This process may have been enhanced in ancient times when the winter monsoon was stronger, driving both vertical mixing and dust transport to the central basin.
Plain Language Summary
Recent studies observe abnormally high winter primary productivity and nitrate concentrations in the surface waters of the central South China Sea (SCS). However, this is a nutrient limited region of the ocean, so the drivers of this primary productivity are unclear. Here we analyze leaf wax carbon and hydrogen isotopes, and Sr‐Nd isotopes, along four shallow‐to‐deep‐water sediment transects to trace the sources of dust and organic matter in the sediments of the central basin. Our results suggest the central basin sediments receive significant terrestrial inputs of dust and nutrients from northern Asia via long‐range aeolian transport during the winter monsoon. These results give new insights to terrestrial‐marine connections and the carbon cycle of the SCS. This process may provide a new mechanism to understand the glacial‐interglacial productivity changes in marginal seas.
Key Points
High concentrations of leaf‐wax n‐alkanes are observed in the South China Sea (SCS) central basin
n‐Alkane carbon preference index and hydrogen isotopic composition trace aeolian dust deposition from higher latitudes to the central basin
Aeolian dust plays a significant role in regulating deposition of terrestrial organic matter in the central SCS
•Distinctive distributions of 3-OH-FAs in marine surface sediments vs soils.•16S rRNA analysis shows distinct bacterial populations in marine sediments.•We propose RAN13 as a new proxy for sea ...surface temperature reconstruction.
3-Hydroxy fatty acids (3-OH-FAs), derived from Gram-negative bacterial outer membranes, have received recent attention for their potential as new terrestrial pH and temperature proxies for palaeoclimate studies. However, it is not known whether 3-OH-FA based proxies can be developed and applied to the marine environment. Here we analyze 3-OH-FAs from a latitudinal transect of marine surface sediments from the North Pacific Ocean (12°N to 61°N with a annual mean sea surface temperature (SST) range of 28.1–1.3 °C). The results show that distributions of 3-OH-FAs in marine sediments yield overall higher abundances of anteiso 3-OH-FA homologues compared to soils. Furthermore, 16S rRNA gene sequencing of the marine sediments and soils shows the Gram-negative bacterial community is dominated by Proteobacteria (ca. 94%) at the phylum level. In contrast, in regional soils the Gram-negative bacterial community is more diverse with significant contributions from Proteobacteria (ca. 50%), Acidobacteria (ca. 24%), Verrucomicrobia (6%), Bacteroidetes (6%) and other phyla. These distinct genomic and molecular differences suggest distinctly different aggregate compositions of bacteria that produce 3-OH-FAs in the marine realm vs soils. Moreover, we find that the ratio of anteiso to normal C13 3-OH-FA (RAN13) measured in surface sediments is highly correlated with annual mean SST throughout the temperature transect. When applied to a short sediment core from the East China Sea, the SST changes reconstructed by the RAN13 proxy are comparable to instrumental SST data. These findings demonstrate that RAN13 and potentially other, so far undiscovered, proxies based on 3-OH-FAs have potential for environmental and palaeoclimate applications in marine environments.
PDF
