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Phylogeny, alkenone profiles and ecology of Isochrysidales subclades in saline lakes: Implications for paleosalinity and paleotemperature reconstructions
No full textLong-chain alkenones (LCAs) produced by phylogenetically classified Groups 1 and 3 Isochrysidales are increasingly used for paleotemperature and/or paleosalinity reconstructions in oligohaline lakes and marine environments. However, there are considerable difficulties in the paleoenvironmental interpretation of LCAs from Group 2 Isochrysidales thriving in saline lakes. The biggest challenge lies in our poor understanding of the complexity and ecological niches of individual Group 2 subclades in saline lakes. Here, we perform comprehensive analysis of haptophyte-specific 18S rRNA sequences and distributions of LCAs, and long-chain alkenoates (LCEs) in surface sediments and suspended particulate matter (SPM) from 37 saline lakes in northern China. These lakes span a large salinity gradient from 0.5 to 308%. Combined with published genomic data of Group 2 Isochrysidales, our phylogenetic analysis reveals three Group 2 subclades occupying distinct ecological niches: one ice-related bloomer Group 2i and two warm-season bloomers Groups 2w1 and 2w2. Group 2i, the earliest seasonal bloomer, frequently co-occurs with Group 2w1 in sediments from saline lakes with relatively low to intermediate salinity waters, whereas Group 2w2 blooms in hypersaline waters. Based on existing data, C-39:4 methyl alkenone is a chemotaxonomic biomarker for Group 2i. %C-3(7:)4 (relative abundance of C(3)(7:)(4 )to the total C-37 alkenones) values in the three Group subclades follow the order: Group 2i > Group 2w2 > Group 2w1. The %C(37:4 )in sediment cores of saline lakes does not directly record past salinity changes, but instead reflects variable contributions in production by these three subclades. This could indirectly and partially reflect overall salinity changes in some lakes dominated by Groups 2i and 2w1, but can be more complicated in lakes dominated by other assemblages. For our sites, we also demonstrate that direct use of C(37 )alkenone unsaturation indices (U-37(K), U-37(K'), and U-37(K '')) for paleotemperature reconstructions in saline lakes is generally not feasible, except for cases where alkenone-producing Isochrysidales are dominated by one single species/subclade and seasonal production effects can be circumvented. We propose two possible alternative proxies for paleotemperature reconstructions in saline lakes: 1) unsaturation ratios of C-41 and C-42 alkenones, as these compounds are predominantly produced by a limited number of Group 2 species, such as Isochrysis nuda (Liao et al., 2020) 2) C38Et/C36OEt ratio (ratio of C-38 ethyl alkenones and C-36 ethyl alkenoates), which appears to have similar temperature sensitivity for Groups 2w1 and 2w2, in lakes with no Group 2i inputs. Our study provides new insights into the phylogenetic classifications of Group 2 Isochrysidales and their ecological/environmental niches, which are fundamental for more quantitative and rigorous applications of LCAs and LCEs in saline lakes as paleosalinity and paleotemperature proxies. (C) 2021 Elsevier Ltd. All rights reserved
Innovative ochre processing and tool use in China 40,000 years ago
No full textHomo sapiens was present in northern Asia by around 40,000 years ago, having replaced archaic populations across Eurasia after episodes of earlier population expansions and interbreeding(1-4). Cultural adaptations of the last Neanderthals, the Denisovans and the incoming populations of H. sapiens into Asia remain unknown(1,5-7). Here we describe Xiamabei, a well-preserved, approximately 40,000-year-old archaeological site in northern China, which includes the earliest known ochre-processing feature in east Asia, a distinctive miniaturized lithic assemblage with bladelet-like tools bearing traces of hafting, and a bone tool. The cultural assembly of traits at Xiamabei is unique for Eastern Asia and does not correspond with those found at other archaeological site assemblages inhabited by archaic populations or those generally associated with the expansion of H. sapiens, such as the Initial Upper Palaeolithic(8-10). The record of northern Asia supports a process of technological innovations and cultural diversification emerging in a period of hominin hybridization and admixture(2,3,6,11)
Enhanced peroxymonosulfate activation by Cu-doped LaFeO3 with rich oxygen vacancies: Compound-specific mechanisms
No full textThe degradation reaction mechanisms of organic pollutants by peroxymonosulfate (PMS) activation processes remain controversial. In this study, Cu-doped LaFeO3 samples were prepared and used as heterogeneous catalysts of PMS for the degradation of pharmaceuticals. Compared to LaFeO3 (LFO), the increased catalytic activity of LaFe1-xCuxO3 (LFCO) samples was observed, among which LFCO-7.5 exhibited the best performance. The enhanced catalytic activity of LFCO-7.5 was attributable to the generation of abundant oxygen vacancies. Hydroxyl radicals, sulfate radicals, superoxide and singlet oxygen were detected in the LFCO-7.5/PMS system. However, selective effects of radical scavengers on the degradation of different pharmaceuticals and selective reactivity of singlet oxygen toward different pharmaceuticals indicate the existence of compound-specific degradation mechanisms in the LFCO-7.5/PMS system. Furthermore, possible degradation pathways of SDZ and the toxicity evolution were investigated during sulfadiazine (SDZ) degradation. This study further enhances our knowledge on the degradation reaction mechanisms of organic pollutants in PMS activation processes
Initial soil formation by biocrusts: Nitrogen demand and clay protection control microbial necromass accrual and recycling
No full textMicrobial biomass is increasingly considered to be the main source of organic carbon (C) sequestration in soils. Quantitative information on the contribution of microbial necromass to soil organic carbon (SOC) formation and the factors driving necromass accumulation, decomposition and stabilization during the initial soil formation in biological crusts (biocrusts) is absent. To address this knowledge gap, we investigated the composition of microbial necromass and its contributions to SOC sequestration in a biocrust formation sequence consisting of five stages: bare sand, cyanobacteria stage, cyanobacteria-moss stage, moss-cyanobacteria stage, and moss stage on sandy parent material on the Loess Plateau. The fungal and bacterial necromass C content in soil was analyzed based on amino sugars -the cell wall biomarker. Microbial necromass was an important source of SOC, and was incorporated into the particulate and mineral-associated organic C (MAOC). Because bacteria have smaller and thinner cell wall fragments as well as more proteins than fungi, bacterial necromass mainly contributed to the MAOC pool, while fungal residues remained more in the particulate organic C (POC). MAOC pool was saturated fast with the increase of microbial necromass, and POC more rapid accumulation than MAOC suggests that the clay content was the limiting factor for stable C accumulation in this sandy soil. The necromass exceeding the MAOC stabilization level was stored in the labile POC pool (especially necromass from fungi). Activities of four enzymes (i.e., beta-1,4-glucosidase, beta-1,4-N-acetyl-glucosaminidase, leucine aminopeptidase, and alkaline phosphatase) increasing with fungal and bacterial necromass suggest that the raised activity of living microorganisms accelerated the turnover and formation of necromass. Microbial N limitation raised the production of N acquisition enzymes (e.g., beta-1,4-N-acetyl-glucosaminidase and leucine aminopeptidase) to break down necromass compounds, leading to further increase of the nutrient pool in soil solution. The decrease of microbial N limitation along the biocrusts formation chronosequence is an important factor for the necromass accumulation during initial soil development. High microbial N demands and insufficient clay protection lead to fast necromass reutilization by microorganisms and thus, result in a low necromass accumulation coefficient, that is, the ratio of microbial necromass to living microbial biomass (on average, 9.6). Consequently, microbial necromass contribution to SOC during initial soil formation by biocrust is lower (12-25%) than in fully developed soils (33%- 60%, literature data). Nitrogen (N) limitation of microorganisms and an increased ratio between N-acquiring enzyme activities and microbial N, as well as limited clay protection, resulted in a low contribution of microbial necromass to SOC by initial formation of biocrust-covered sandy soil. Summarizing, soil development leads not only to SOC accumulation, but also to increased contribution of microbial necromass to SOC, whereas the plant litter contribution decreases
<p>Carbon dioxide activated biochar-clay mineral composite efficiently removes ciprofloxacin from contaminated water - Reveals an incubation study</p>
No full textCiprofloxacin, a second-generation synthetic fluoroquinolone derivative widely used in human and veterinary medicines, has the potential to pose a serious risk to aquatic organisms and humans. The current research investigated the removal of ciprofloxacin using biochar treated with clay mineral and subsequently activated with carbon dioxide (CO2) produced at two different pyrolysis temperatures (350 and 650 C). Batch adsorption experiments were carried out to assess the removal efficiency of ciprofloxacin by as-synthesized materials. The effects of various factors, such as pH, contact time, adsorbent dose, initial ciprofloxacin concentration, and temperature were studied during the removal process. The physicochemical characterization results verified the successful loading of clay minerals on biochar. Non-linear adsorption models were employed to understand the nature of adsorption processes however, the Pseudo-second-order kinetic and Freudlich and Redlich Peterson isotherm models best fitted with the adsorption data. These findings indicated that the adsorption did not follow an ideal monolayer adsorption suggesting hybrid chemical adsorption process that was spontaneous and endothermic. The maximum adsorption (50.32 mg g(-1)) of ciprofloxacin was achieved by CO2 activated biochar-clay mineral composite prepared at 350 C, and was almost two times higher than the pristine biochar at neutral pH and 40 C. The possible proposed mechanisms involved for the removal of ciprofloxacin were electrostatic attraction, cation exchange, pore-filling effect, and 7C-7C interactions. Our findings demonstrate that application of CO2 activated biochar-clay mineral composite is a promising technique for efficient removal of ciprofloxacin from aqueous solution
Radiocarbon in the Atmosphere and Seawater in the South China Sea: Flux, Inventory and Air-Sea CO2 Exchange Rate Tracing
No full textDelta C-14 values of the atmosphere and seawater dissolved inorganic carbon (DIC) were measured during a cruise in the South China Sea (SCS) in September 2015, in order to determine the C-14 flux and bomb C-14-based air-sea CO2 exchange rates for this region. The background atmospheric Delta C-14 value (13.8 +/- 5.0 parts per thousand) for the SCS during that period was lower than that (35.4 +/- 3.4 parts per thousand) of surface seawater (5 m) DIC, and a net transfer of C-14 from the sea to the atmosphere (7.4 +/- 5.0 x 10(11) atoms m(-2) yr(-1)) was determined at the wind speed of 5.2 +/- 1.7 m s(-1). Seawater DIC Delta C-14 profiles showed the highest value (37.9 +/- 3.7 parts per thousand) at a depth of 100 m, a rapid decrease below that depth to -220.3 +/- 3.2 parts per thousand at 1,500 m, and nearly constant values below 1,500 m. The average mean penetration depth of bomb C-14 was 585.5 +/- 99.2 m, and a value of 8.2 +/- 1.0 x 10(9) atoms cm(-2) was obtained for the bomb C-14 inventory in this region. Based on this inventory, a long-term (1954-2015) average air-sea CO2 exchange rate of 20.2 +/- 2.8 mol m(-2) yr(-1) was traced for the SCS. Combined with the pCO(2) measurements in this region, a net CO2 flux rate of 0.54 +/- 0.08 mol m(-2) yr(-1) was yielded for the SCS, which is comparable to the cruise measured flux (0.44 +/- 0.62 mol m(-2) yr(-1)) obtained from a synthesis study (Li et al., 2020, https://doi.org/10.1016/j.pocean.2020.102272). Our study highlights the importance of continued atmospheric and seawater C-14 observations on determining the air-sea flux in this region
Water Resource Management Implications for a Desert Oasis From Tree-Ring delta O-18 Variations in Populus Euphratica in Northwest China
No full textPaleoclimatic data has often been applied to demonstrate the influence of anthropogenic activities on runoff to desert rivers, and such features as reservoirs are clearly known to influence available water in downstream riparian settings. The impact of human activities on the hydrology of a downstream desert oasis is, however, an open question. High-resolution hydroclimate paleo-reconstructions for desert oases are lacking, partly because paleoclimate proxies in extremely dry deserts are insensitive to extremely low precipitation. Here, we first attempt to reconstruct regional precipitation (r = -0.743, p < 0.001, n = 49) for the interval 1886-2009 from the stable oxygen isotope ratio (delta O-18) of five Populus euphratica trees growing in the Ejina Oasis, on the lower reaches of the Heihe River in extremely arid Northwest China. The delta O-18 series for P. euphratica in the oasis (similar to 900 m a.s.l) abruptly increases relative to an delta O-18 series of Qinghai spruce (Picea crassifolia) growing in upper limit of forest (similar to 3,000 m a.s.l) in Longshou Mountain (middle reaches of the Heihe River) after about 2000, when the Ecological Water Diversion Project on the Heihe River was implemented. This finding implies that the Ejina Oasis suffered from serious drought during the last decade, or at least that the Oasis is stressed more than expected by current climate conditions. Other evidence also indicates that human activities contributed to a decrease in air moisture in the Ejina Oasis after 2000. To mitigate water stress on the oasis, we recommend some practical measures to ensure the rational development of the desert oasis
Novel investigation of pyrolysis mechanisms and kinetics for functional groups in biomass matrix
No full textBiomass, as a renewable and sustainable energy resource, can be converted into environmentally friendly and practically valuable biofuels and chemical materials via pyrolysis. However, the process optimization and pyrolysis efficiency are restricted by the limited perception of the complicated mechanisms and kinetics for biomass pyrolysis. Here, to establish an in-depth mechanism model for biomass pyrolysis, we presented a novel investigation for the thermal evolutions and pyrolysis kinetics of the functional groups in peanut shell matrix by using in-situ Fourier transform infrared spectrometry (in-situ FTIR) and thermogravimetric analysis-Fourier transform infrared spectrometry-mass spectrometry (TG-FTIR-MS). The in-situ FTIR spectrum deconvolution for the solid matrix was innovatively introduced to identify and quantify the real-time evolution and thermal dynamics of the functional groups during peanut shell pyrolysis. The result for the first time proposed that the pyrolysis mechanisms of total OH at 20-380 degrees C, aliphatic C-H-n groups at 20-500 degrees C, C=O groups at 260-500 degrees C, and C-O groups at 300-500 degrees C were dominant by diffusion and order-based chemical reactions. The TG-FTIR-MS analysis was conducted for the online monitoring of the released volatiles and gases, the amounts of which were in the sequence of C=O > CO2 > aliphatic C-O-(H) > C-O-(C) in esters > aromatics > H2O > phenolic hydroxyl > aliphatic hydrocarbons > CO. The study established a novel methodology to evaluate the biomass pyrolysis mechanisms at the molecular level, which provided valuable information for developing advanced pyrolysis techniques on a large scale for sustainable ecosystem
Geochemistry of evaporitic deposits from the Cenomanian (Upper Cretaceous) Maha Sarakham Formation in the Khorat Basin, northeastern Thailand
No full textThe Cenomanian (Upper Cretaceous) Maha Sarakham Formation of the Khorat Basin, northeasternThailand consists of three evaporite units (Lower, Middle and Upper Salt) interbedded with clasticsediments and exhibits abundant deposits of potash. Although numerous studies have been carried outon the Khorat potash deposit, results are still equivocal with regard to the origin of the rock salt, whetherit was marine or non-marine (hydrothermal and/or mixedfluids). The purpose of this study is to examinethe origin of rock salt based on elemental compositions and boron isotope analyses in the southwesternpart of the Khorat Basin. A stratigraphic correlation offive boreholes (K-201e205) located in BamnetNarong and Chaturat districts, Chaiyaphum province, Thailand, revealed a salt dome structure. Theelemental composition andd11B values in the longest borehole K-203 indicate a precipitation of haliteand carnallite from seawater. Rare earth elements (REE) of claystone and siltstone fromfive boreholes (K-201e205) are comparable to the REE of sandstone from the Simao Basin in China, which suggest asimilar provenance. Stratigraphic comparisons and geochemical signatures are important for a betterunderstanding of the recharge models of paleoseawater. In agreement with some previous studies, weconclude that the Cenomanian evaporites within the Khorat Basin are marine deposits. (c) 2021 Elsevier Ltd. All rights reserve
Assessment of the juvenile vulnerability of symbiont-bearing giant clams to ocean acidification
No full textOcean acidification (OA) severely affects marine bivalves, especially their calcification processes. However, very little is known about the fate of symbiont-bearing giant clams in the acidified oceans, which hinders our ability to develop strategies to protect this ecologically and economically important group in coral reef ecosystems. Here, we explored the integrated juvenile responses of fluted giant clam Tridacna squamosa (Lamarck, 1819) to acidified seawater at different levels of biological organization. Our results revealed that OA did not cause a significant reduction in survival and shell growth performance, indicating that T. squamosa juveniles are tolerated to moderate acidification. Yet, significantly reduced net calcification rate demonstrated the calcifying physiology sensitivity to OA, in line with significant declines in symbiont photosynthetic yield and zooxanthellae density which in turn lowered the amount of energy supply for energetically expensive calcification processes. Subsequent transcriptome sequencing and comparative analysis of differentially expressed genes revealed that the regulation of calcification processes, such as transport of calcification substrates, acid-base regulation, synthesis of organic matrix in the calcifying fluid, as well as metabolic depression were the major response to OA. Taken together, the integration of physiological and molecular responses can provide a comprehensive understanding of how the early life history stages of giant clams respond to OA and make an important leap forward in assessing their fate under future ocean conditions