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Defect accumulation and nonradiative recombination at the interface of the electron-transport layer (ETL) and the photosensitive layer are inevitable obstacles to efficient and stable perovskite solar cells (PSCs). Herein, we reported a dual-effect interface modification strategy that employs potassium tetrafluoroborate (KBF

The inorganic perovskite solar cells (PSCs) are now playing an increasingly essential role in the realm of clean energy. However, the application of inorganic perovskite solar cells is usually limited as the spontaneous phase transform. Here, we applied the 1H, 1H-Perfluorooctylammonium iodide (PFOAI) upon the surface of the cesium lead iodide (CsPbI3) films by taking advantage of its excellent defect passivation ability and hydrophobicity. Decreased recombination upon the surface and postponed degradation of the device were achieved for the observation of lower trap density and longer carrier lifetime and better stability based on the PFOAI-CsPbI3 films. The champion PFOAI-CsPbI3 based device showed an increased power conversion efficiency (PCE) of 18.24% with the excellent fill factor (FF) of 81.77% and Jsc of 20.51 mA cm−2 and remain ∼85% of its initial PCE for 1000 h (25 °C) in the N2 glovebox. This work adds slightly weight on the balance of balancing the stability and high efficiency of the inorganic PSCs.

Scleractinian corals exhibit a dual trophic pattern of autotrophic photosynthesis and heterotrophic predation. However, whether corals can adjust their trophic status under contrasting environmental conditions remains unclear. In our study, 70 scleractinian corals (Favia palauensis) were collected from Sanya and the Xisha and Nansha Islands in the South China Sea. We measured the zooxanthellae density (ZD) and δ13C of zooxanthellae (δ13Cz) and host tissue (δ13Ch) and analyzed the difference between δ13Ch and δ13Cz (i.e., Δh−z 13C). The relatively high ZD and δ13Cz values in the samples from Sanya indicate that these corals might have higher photosynthetic rates and autotrophic abilities than those from Xisha and Nansha. In contrast, the relatively low δ13Ch and Δh−z 13C values in the samples from Xisha and Nansha suggest that these corals might have a higher heterotrophic ability than those from Sanya. In addition, we tested the coral tissue biomass and skeletal δ13C (δ13Cs) in the samples from Sanya and examined their correlations with Δh−z 13C. The results showed a negative correlation, indicating that the more the organic material produced by the coral, the stronger its heterotrophic ability. Our results show that corals can adjust their trophic status under different environmental and physiological conditions, which is essential for increasing their adaptability to different environmental conditions.

Because the heterostructure of soft perovskite possesses a weak bonding nature, the photovoltaic performance and stability of devices are limited by numerous under-coordinated ions (Pb2+ or CH3NH3+) or iodine vacancies at the TiO2/CH3NH3PbI3 interface. Herein, organic super-halide salt tetrabutylammonium borohydride (TABH) was introduced to the TiO2/CH3NH3PbI3 interface, and it impeded the movement of decomposed components from the soft CH3NH3PbI3 lattice and thus increased the trap passivation effect. As a result, there was an increase in the power conversion efficiency (PCE) from 18.2% to as high as 20.4% with suppressed hysteresis, which can be ascribed to the incorporated TABH-optimized energy level alignment and fewer iodine vacancies as well as traps. Furthermore, considering the strong chemical interactions of the Pb–BH4−t bond, the under-coordinated lead ions were stabilized by the incorporation of the TABH interlayer and were able to impede ion migration or volatilization, thereby enhancing the stability of perovskite solar cells (PSCs). More importantly, PSCs maintained 80% of their initial efficiency after storage for 1200 h in the ambient environment. This work provides a facile interface strategy that compensates for the intrinsic instability of soft perovskite's heterostructure and demonstrates the fabrication of highly efficient PSCs for further application.

In the past few years, hybrid organic–inorganic perovskite solar cells (PSCs) have shown great potential for solar energy conversion in photovoltaic applications, due to their high power-conversion efficiency and low-cost fabrication. A high-quality perovskite film with large grain size and low-defect density plays a crucial role in high-performance FAPbI3-based PSCs. To date, only a few research efforts have focused on investigating the role of modifiers in precursor solutions of perovskite materials in terms of modulating the nucleation rate to obtain high quality perovskite films. Herein, by introducing ethanedithiol (ED) and tetrabutyl ammonium perchlorate (TAP) into the precursor solution, homogeneous nucleation occurred preferentially and high-quality α-FAPbI3 perovskite films with grain size scales up to the micron-level (∼1.7 μm) were obtained. Obviously, with a decrease in the number of grain boundaries, the defect density of the final modified films was also reduced. The modified FAPbI3-based PSCs achieved a PCE of 20.15% and maintained about 92% of the initial efficiency in an air atmosphere.

Mixed lead-tin perovskite solar cells (LTPSCs) with an ideal bandgap are demonstrated as a promising candidate to reach higher power conversion efficiency (PCE) than their Pb-counterparts. Herein, a Br-free mixed lead-tin perovskite material, FA

Formamidinium lead iodide-based (FAPbI3 ) perovskite is widely used in the field of photovoltaics, owing to its suitable bandgap (ca. 1.45 eV) and better thermal stability. FAPbI3 has two polymorphs (black α-FAPbI3 and yellow δ-FAPbI3 ) at ambient temperature. The yellow δ-FAPbI3 , which has no photoactivity, has a chain-like structure that likely hinders electron transport and reduces photovoltaic performance. However, pure-phase black α-FAPbI3 without any yellow phase is difficult to obtain and the underlying mechanism of the phase transition is rarely investigated. In this study, a facile bi-additive method (BA method) has been developed to completely eliminate the yellow δ-FAPbI3 phase by inducing a phase transition from δ-FAPbI3 to α-FAPbI3 . HI and Pb(SCN)2 were employed as dual additives. Based on the investigation of the annealing time and temperature, we determined that the BA method can induce the phase transition and enhance the stability of α-FAPbI3 . Owing to the enhanced crystallization as well as uniform morphology of the BA film, the perovskite solar cells (PSCs) exhibited an increased power conversion efficiency (PCE). Furthermore, the optimal devices displayed excellent stability and maintained over 80 % of initial PCE after aging for 400 h in air. This work provides a new insight into the fabrication of high-quality pure α-FAPbI3 perovskite films and makes high efficiency photovoltaic devices a reality.

Perovskite solar cells (PSCs) are susceptible to intrinsic structural instability associated with the presence of inorganic halide anions and organic cation vacancies, thus leading to the deterioration or even premature failure of devices. Herein, we develop an efficient strategy using super-halogen BH4- substitution to simultaneously immobilize methylammonium and substitute iodide vacancy for high-performance PSCs based on the dihydrogen bonding interactions. The introduced super-halogen BH4- groups not only significantly reduce the vacancy density but also effectively inhibit the decomposition of the CH3NH3+ group by forming perovskite CH3NH3PbI3-x(BH4-)x. The power conversion efficiency (PCE) of the assembled mesoporous devices is remarkably promoted from 18.43 to 21.10%, accompanied by significant increase of both Jsc and Voc without obvious hysteresis. The superior PSCs can retain 90 and 80% of their initial PCE even after being stored for 1200 h under environmental conditions (50 ± 10% RH) and 240 h at 85 °C in the dark, respectively. Moreover, it delivers excellent optical stability under ultraviolet illumination. This work provides an avenue to improve both the long-term stability and photovoltaic performance of PSCs.

The low photovoltaic performance of 2D perovskites, which is caused by high exciton binding energy and wide band gaps, has limited their further development and applications. Here, we adopted a new-type strategy to obtain high-quality 2-hydroxyethylamine (HEA)-based quasi-2D perovskite films by incorporating halogenated second spacer cations. Due to the effective passivation of halogenated benzylammonium cations with enhanced electronegativity, the mixed quasi-2D perovskites displayed superior crystallinity and reduced internal defects, leading to an enhanced charge transfer and suppressive carrier recombination. As a result, significantly improved power conversion efficiency (PCE) from 15.19% to 18.75% with an enhanced open-circuit voltage (Voc) and fill factor (FF) was achieved. After aging at 85 °C for 200 h and 45 ± 5% relative humidity (RH) for 1500 h, the unencapsulated optimal devices retained 81% and 90% of the initial PCE, respectively. Our study provides an effective and simple strategy to improve the photovoltaic performance and environmental stability of 2D perovskites for commercial applications.

The decadal variability of ocean primary productivity (PP) has mainly been studied using relatively short term satellite data, limiting its in-depth analysis. Here, by removing the influence of the C Suess effect, we extract the PP signal on decadal timescales using a record of coral δC values from the northern South China Sea (NSCS), where the physical-biogeochemical conditions are influenced largely by the winter monsoon. Our results show that the PP in the NSCS increased from 1851 to the 1920s and decreased from the 1920s to 2007, and large superimposed decadal-scale changes were observed. The in-phase relationship observed between the PP reconstruction and winter monsoon records suggests that the changes in the PP in the NSCS are linked to decadal-scale changes in the winter monsoon. Considering that the winter monsoon intensity may weaken in the future under global warming, the PP in the NSCS might decrease in the coming decades.

The most critical reason for limiting the extensive study and promotion of MA-based perovskites is their intrinsic instability when compared to FA-based perovskites. Therefore, it is necessary to develop a simple and effective method to improve their intrinsic stability. Herein, the 1,1,1-trimethylhydrazinium cation (TMH

Although two-dimensional perovskites have attracted much attention due to their high humidity stability, their poor photovoltaic performances have severely obstructed their further development. As ...

“Refuge theory” suggests that global warming would be beneficial to corals in high latitude waters. In theory, then, the Weizhou Island reef (21°00′–21°10′N, 109°00′–109°15′E), which is located in a relatively high latitude area in the northern South China Sea, is a refuge for corals under global warming. Yet, the corals here have degenerated significantly. We investigated the ecological status of the Weizhou Island reef in 2015 and recorded 11 families, 22 genera, and 41 coral species. The mean living coral cover has decreased from ~ 42% in 1984 to ~ 10% in 2015 and there are many dead Acropora in the study area, especially at the reef flat. Coral assemblage structure has undergone degradation with the dominant group shifting from high complexity branching, foliaceous and massive colonies to a simpler group of massive morphologies. The only sign indicating the corals here benefiting from global warming is the occurrence of a large amount of juvenile Porites lutea (31.91% of the total population), which represents the recovery potential of the Weizhou Island reefs. Further analysis concludes that the main reason for the rapid degeneration is escalating anthropogenic impact, such as seawater pollution, unsustainable tourism activities, ongoing overfishing, all of which degrade the local ecological environment. It seems that intensive anthropogenic activities have weakened the “refuge” function significantly. Decreasing living coral cover as well as degraded assemblage structure all suggest that Weizhou Island offers limited potential as refuge habitat for corals in the context of global warming and intensive human activities.

As a natural laboratory for testing various paleoclimatological and paleoceanographic hypotheses, the Pliocene-Pleistocene stratigraphic sequence from a full-coring major scientific drilling (Well CK2 with total length: 928.75 m) in Yongle atoll of Xisha Islands, northern South China Sea was studied. The Petrography of studied section of the core was dominated by reef carbonate limestones which contain abundant shallow marine organisms, e.g., coralline algae, corals, and foraminifera, which almost consisted of pure carbonates and preserved the primary geochemical message since Pliocene. According to the isolation of Well CK2 and the provenance of elements, the systematic changes and abrupt points of isotope and element geochemical compositions (rare earth element parameters, SiO2 content, Al/Ti ratio, etc.) from coral reef carbonate record presented the elevated terrigenous influences related to the East Asian monsoon after ~2.6 Ma BP, as part of the Pliocene-Pleistocene climate transition. Our results demonstrated that the continental weathering controlled by the East Asian summer monsoon dominated the surface seawater compositions of study area before ~2.6 Ma BP, when the winter monsoon was not strong enough to exert significant influences. Then, the effects of eolian dust associated with the intensity of East Asian winter monsoon, the precipitation driven by summer monsoon, and the global temperature, which played different roles at different periods after ~2.6 Ma BP, should be considered. Our results confirmed that the potentials and significances of shallow-water carbonate deposition from coral reefs, and provided a unique perspective to shed light on the carbonate record of climate changes.

Recently, perovskite solar cells (PSCs) have represented a significant breakthrough due to their excellent photoelectric properties. However, short lifetime and poor moisture stability make it difficult for PSCs to achieve further application. Here, we have introduced a fluorinated ammonium salt (2,2,2-trifluoroethylamine hydroiodide, FEAI) with a high dipole moment to grow a 2D modified layer ((FEA)2PbI4) at the interface of perovskite/HTL. Due to the electronegativity of FEA+, the 2D modified layer brings about an effective passivation effect, leading to reduced interface defect sites and suppressed nonradiative recombination. Moreover, the remarkable hydrophobicity of the 2D modified layer can provide protection of 3D perovskite from moisture erosion but not at the expense of efficiency. As a result, based on (FAPbI3)0.85(MAPbBr3)0.15, the FEAI-modified PSCs showed a high power conversion efficiency (PCE) of 19.24%, with an open-circuit voltage (Voc) of 1.08 V, a short circuit current density (Jsc) of 22.65 mA cm−2 and a fill factor (FF) of 78%. After aging under a relative humidity of 50 ± 5% for 60 days, the modified PSCs retain 88% of their initial PCE. Our work provides a valuable strategy to prepare a 2D perovskite modified layer with a high dipole moment cation for high-performance PSCs with superior moisture stability.

The introduction of polymer additives is a simple but effective method to achieve highly stable perovskite solar cells (PSCs). However, most polymer additives display the characteristic of being insulating, which will restrain the carrier transport in the perovskite light absorption layer and have a negative impact on the photoelectric performance of the devices. Hence, to address this issue, a new conductive polymer additive of polyaniline (PANI), which has special electrical and optical properties, was employed. Under the multiple effects of PANI, the quality of perovskite films was markedly enhanced, with outstanding crystalline structure, improved light absorption and uniform surface morphology, leading to faster PL quenching and charge transfer. As a result, the device with PANI exhibited a dramatically improved PCE from 16.96% (pristine) to 19.09% and reduced hysteresis behavior. The aging tests indicated that PANI perovskite devices show stronger humidity and heat stability, and they exhibited a larger water contact angle than the pristine perovskite. In particular, a PANI perovskite device maintained 86% of its initial PCE after aging under 50% RH for about 1600 h. Our results reveal that a suitable polymer additive displays a huge potential to improve the PCE and long-term stability of PSCs.

On Xisha Islands, located in the South China Sea, the Neogene succession includes the unconformity-bounded Huangliu Formation that is 210.5 m thick in well CK-2 and formed almost entirely of dolostones. The diverse biota in the Huangliu Formation, which includes corals, algae, bivalves and foraminifera, indicates that the original carbonate sediments accumulated in water that was < 30 m deep. The dolostones are formed of various mixtures of low- and high-calcium calcian dolomite with limpid dolomite lining the walls of many cavities. The O-18 and C-13 stable isotopes suggest that dolomitization was mediated by slightly modified seawater. The Sr-87/Sr-86 ratios from the dolostones suggest that dolomitization took place similar to 9.4 and 2.3 Ma ago, with the age of dolomitization becoming progressively younger towards the top of the formation. "Island dolostones" like these, found on many islands throughout the Pacific Ocean and the Caribbean Sea, have commonly been linked to eustatic changes in sea-level with dolomitization taking place during lowstands, highstands, or transgressive phases. Data from the Huangliu Formation in well CK-2 suggests that dolomitization was associated with (semi-) continuous transgressive conditions that were controlled by the interaction of tectonic subsidence and eustatic changes in sea level.

As one of the most abundant metals in heavy oils, Ni has suffered so notably increasing impacts from industrial and traffic activities that anthropogenic Ni emissions have altered natural geochemical processes. The coral Ni/Ca has become a reliable proxy for characterizing marine pollution, but this potential has been unexploited for highlighting oil pollution. Here, we utilized a high-resolution record of geochemical parameters (Ni/Ca, δ18O, and δ13C) in a Porites coral of an offshore island in the northern South China Sea to reconstruct of Ni distribution patterns in surface seawater from 1984 to 2015. The coral Ni/Ca ratios exhibit minor fluctuations, except for multiple mutation peaks (0.20 ± 0.42 μmol/mol) during the period from 1984 to 1993. The ratio was low and stable (0.10 ± 0.09 μmol/mol) from 1994 to 2008, and then increased rapidly with significant variations (1.60 ± 4.56 μmol/mol) from 2009 to 2015. The coral Ni/Ca ratios captured all significant Ni discharges, and this demonstrates its potential for recording oil spill episodes. The historical variations in the contributions of Ni indicate that industrial and traffic activities should be responsible for changes in the anthropogenic input. The leaks and consumptions of petroleum likely account for the primary Ni emission sources.

Excess anthropogenic phosphorus (P) supplied to marine systems, which may subsequently jeopardize ecosystem structure and function, has altered the P balance and quadrupled its flow. However, due to the diversity of P sources, the unpredictability and variability of human activities, and the absence of long‐term records, it remains uncertain how long the effects of excess P persist in aquatic ecosystems, and whether it stimulates gross primary productivity. In this study, we utilized geochemical proxies in coral skeletons from an atoll in the Xisha Islands of the South China Sea to reconstruct historical patterns of P in surface seawater. This atoll has remained in a natural state for an extended period of time, except for a short period of unambiguously documented guano extraction. Analyses of coral skeletons dating back to 1851 CE distinctly show that the P concentration in surface seawater increased abnormally in the 1960s. We deduced that guano extraction at that time led to an abrupt increase in the long‐term equilibrium of seawater P concentration. Subsequent P addition appeared to have continued for at least ~30 years after phosphorite exploitation ceased, and P showed a decay period that was longer than that of other elements. Similar temporal trends of coral P/Ca and δ13C indicated that elevated marine primary productivity was associated with increased P. Large inputs within a short period, as well as the continued influence of P over the long term, can serve as a natural ecological analog for coral reefs subject to nutrient contamination.

The importance of submarine groundwater discharge (SGD) is becoming increasingly recognized because of its potential significance as a source of dissolved species. To explore the probable coral geochemical signal of SGD and verify the validity of potential reliable proxies, multiple geochemical proxies over the last 137 years were identified from a Porites coral near a subterranean estuary in the northern South China Sea, where the SGD was reported to be the predominant flux of terrestrial waters to the coastal ocean. Results indicated that the SGD in the coastal zone was the dominant source of trace elements, especially REE and Ba, due to the various dissolution reactions occurring during groundwater flow in the karst terrain. The time- and frequency-domain comparison between the coral geochemical proxy and the local/regional precipitation indicated that coral REE/Ca ratios are predominantly impacted by the SGD associated with local precipitation, while coral Ba/Ca ratios are also affected by the primary productivity and allochthonous seawater Ba from surrounding areas. The REE signal from coral allows us to reconstruct the coastal surface seawater REE concentrations and the SGD rates on the coast of Sanya during 1870–2006. In a novel approach to developing a proxy for historic SGD to coastal waters, this study provides evidence that the coral REE/Ca record from the karst coast with large SGD has potentials to be a promising paleohydrological indicator.

Formamidinium lead iodide-based (FAPbI

Oil, is one kind of natural product of biological origin which is depleted in 13C. Coral skeletal δ13C is an important archive of environmental and climatic change. However, few studies have been conducted on the effect of oil spill on the coral skeletal δ13C at present. This kind of research is useful for us to obtain environmental and climatic information from coral skeletal δ13C. In this study, two continuously growing Porites corals (W1 and W3), aged 22 and 31 years (1994–2015 and 1985–2015), respectively, were collected from the fringing reef of Weizhou Island in October 2015, coral skeletal δ13C and δ18O were analyzed. Besides, seawater was collected during an oil spill in 28 January 2018, and was used for δ13CDIC (δ13C values of DIC) analysis. The purpose is to explore the potential impact of oil spills on δ13CDIC and coral δ13C. δ13CDIC value during oil spill was significantly lower than that of normal seawater (Δδ13C≈-2.38‰). Coral δ13C of both two coral colonies showed lower values since 2008 (average value of δ13C before and after 2008 change from −2.04 ± 0.48‰ to −3.33 ± 0.55‰ ‰ and −1.77 ± 0.49‰ to −2.88 ± 0.54‰ of W1 and W3 respectively), especially, several abrupt negative shifts in 2008, 2009, 2011, 2012 and 2014 when oil spills occurred (extent of δ13C variation were W1：−3.08‰, −1.82‰, −1.82‰, −1.53‰, −1.37‰; W3：−3.27‰, −1.8‰, −1.91‰, −1.21‰, −1.13‰ respectively). Our results clearly show that degradation of oil by microorganisms when oil spill occurs should render a decrease in the 13C/12C ratio of the seawater dissolved inorganic carbon (DIC) which is the ultimate carbon source of coral calcification.

The East Asian winter monsoon (EAWM) plays a significant role in the Asian climate system. However, the scarcity of direct high-resolution records, especially those covering recent centuries, limits our understanding of monsoonal dynamics. Here we present a reconstruction of annual EAWM strength over the past century and a half using a Porites coral from Yongxing Island in the northern South China Sea (SCS), where the variations in the rare earth element (REE) parameters in surface seawater are dominantly controlled by the input of aeolian dust. Our record indicates that the EAWM strength weakly increased overall during the latter half of the nineteenth century but decreased during the twentieth century, especially after ~1950 Common Era. Additionally, during the past century and a half, the relationship between the EAWM and the East Asian summer monsoon, as recorded in speleothems, varied temporally and depended on the strength of the EAWM. Our findings suggest that the REE proxy of corals from the offshore SCS can be applied as an excellent indicator of the winter monsoon strength.

Coral bleaching is becoming a serious issue for coral reefs under the stress of global warming. However, whether it has occurred in the past in times of thermal stress remains unclear. Moreover, an understanding of historic coral bleaching events would greatly improve our insight into the adaptive capabilities of corals under such stresses. It is known that Porites corals, a massive coral, have relatively high levels of symbiotic zooxanthellae and a strong thermal tolerance when compared with most other corals (and particularly branched corals). Thus, growth hiatuses and/or mortality surfaces of fossil Porites may be used to indicate past ecological or environmental stress events, such as severe bleaching. In this study, monthly geochemical and isotopic environmental proxies of four fossil Porites corals with well-preserved growth hiatuses and mortality surfaces (aged 3,800–4,200 years before 2013 A.D.), collected from Wenchang fringing reef, Hainan Island, Northern South China Sea were analyzed. Specifically, the Sr/Ca, δ18O, and δ13C were measured with a monthly resolution for each sample. These environmental proxies were used to reconstruct the sea surface temperature (SST), sea surface salinity (SSS), and physiological activity of the coral at the time when the growth hiatuses and/or mortality surfaces occurred. These data were subsequently used to determine the causes of coral mortality and growth discontinuity in each case. The results show that growth hiatuses and mortalities mainly occurred in summer, with high SST (31–34°C) and SSS (32.8–38.4). In addition, abrupt negative shifts of 2–3‰ in δ13C were observed in almost all of the surfaces of growth hiatus and mortality, indicating a dramatically reduced level of photosynthetic activity in symbiotic zooxanthellae. Because of the above reasons, we conclude that the frequently observed mortality and growth discontinuity of Porites corals from the mid-Holocene is evidence for thermal bleaching events in the past. That is, coral bleaching has occurred 3,800–4,200 years ago and is not a new phenomenon.

The micro-conditions that control dolomitization processes were still not well known in natural environments. Cenozoic “island dolostones” are ideal for examining the processes since they are geologically young and have not experienced deep burial conditions. Miocene dolostones from the Xisha Islands, located in the South China Sea, are similar to those found on Grand Cayman Island, located in the Caribbean Sea. These dolostones are composed of low-Ca dolomite (LCD, 55 %Ca). Individual dolomite crystals are commonly formed entirely of LCD or HCD, and/or HCD cores that are encased by LCD and alternating zones of HCD and LCD (1–10 μm thick). The crystal textures indicate that the LCD and HCD are primary growth features (no obvious recrystallization) that formed as the dolomite replaced the limestone precursor. The compositional features (%Ca in LCD and HCD, average %Ca, and proportion of LCD and HCD) and geochemical parameters (O/C isotopes, Sr, Fe and Mn) of dolomite indicate that the Mg was incorporated into dolomite crystals in an orderly manner that was mainly controlled by the interaction of fluid properties and crystal structure. The fact that dolomite stoichiometry varied laterally and vertically throughout the successions shows that micro-scale physicochemical conditions played a critical role in the evolution of individual dolomite crystals. The similarities between the dolostones of the Xisha Islands and Grand Cayman, which are 15,795 km apart, indicate that the factors that control the micro- and large-scale features of these dolostones must have undergone similar processes or experienced similar physicochemical conditions despite their disparate settings.

Holocene coral reef development is valuable to understanding the behavior and impacts of paleoclimate and sea level changes. This study focuses on the Holocene carbonate sequences of a drill core extracted from Well CK2 in the northern South China Sea (SCS). This drill core consists of an 873.55 m thick carbonate layer overlying 55.20 m of volcanic basement. High precision U-series dating of 22 coral samples suggests that the Holocene coral reef, which has a thickness of 16.7 m, initiated at ~7800 yr BP (years before 1950 CE) and stopped vertical accretion at 3900 yr BP. The mean vertical accretion rate in the Holocene in Well CK2 was 3.48 m kyr−1, varying from 6.44 m kyr−1 during 7800–6000 yr BP to 0.87 m kyr−1 during 6000–3900 yr BP. After 3900 yr BP, the vertical development of the reef ceased, indicating that the reef development likely involved lateral accretion. The Holocene section mostly consists of unconsolidated coarse sediments, mainly including corals, coralline algae, large benthic foraminifera, and mollusks. Based on the relationship between coral reef development and sea level, together with the age profile, we determined that the relative sea level near Chenhang Island rose rapidly between 7800 and 6000 yr BP, slowed at ~6000 yr BP, and reached a position of about 2 m above the present-day mean sea level by 3900 yr BP. After 3900 yr BP, the sea level was stable or fell, resulting in a cessation in the reef's upward development.

Two-dimensional perovskite solar cells (PSCs) with high moisture resistance are a key topic in the photovoltaic field. However, their lower power conversion efficiencies (PCEs) in comparison to 3 D PSCs is still an urgent problem to be solved. It is vital to understand the impact of constituent ratios and ammonium salt sizes on the photovoltaic performance and humidity stability. Based on the formula of (RNH3 )2 (MA)n-1 Pbn I3n+1 (n=1, 3, 5, 7, 9, and 11), a series of 2 D perovskites is prepared by introducing varisized ammonium salts of ethylammonium iodide (EAI), propylammonium iodide (PAI), and butylammonium iodide (BAI). The effects of the constituent ratios and varisized ammonium salts on the properties of the 2 D perovskites were studied. 2 D perovskite devices based on larger n and smaller ammonium salt size are found to exhibit better performances. However, the moisture resistance of the 2 D perovskite devices is higher when n is smaller and the ammonium salt size is larger. Therefore, the EA2 MA10 Pb11 I34 (n=11) 2 D perovskite device displays the best photovoltaic performance, with the highest PCE of 16.93 %, whereas BA2 MA2 Pb3 I10 (n=3) 2 D perovskite, with the largest contact angle of 79.8°, can retain over 85 % of the initial PCE after 1440 h aging at 50 % relative humidity. This work indicates the PCE and stability of 2 D perovskites can be conveniently and effectively adjusted by controlling the 2 D constituent ratios and ammonium salt sizes, so as to obtain efficient 2 D PSCs with high stability.

The ionic nature of hybrid perovskites indicates the existence of inevitable and multi-type defects. Design of effective passivation molecules becomes a vital means to suppress charge recombination and reduce the voltage loss in perovskite solar cells. However, most of the reported passivation molecules show single effect and the passivation mechanism of molecules with multiple functional groups is unclear. Herein, on the premise of making sure the combined passivation effect of amine, carbonyl group and benzene ring, we tailored multifunctional passivation molecules (4-fluorobenzamide and 4-chlorobenzamide) by introducing halogen functional group. After employing high-electronegativity halogen groups, the hydrogen bond with organic cations and ionic bond with Pb2+ were formed, which is the key to prevent defect regeneration and ion migration. The perovskites with halogenated passivation molecules displayed reduced trap densities and increased carrier lifetimes. Finally, multifunctional passivation molecules can not only effectively heal defects but also improve the stability of perovskite materials. The optimal devices with 4-fluorobenzamide achieved a 5.6% enhancement of open-circuit voltage (Voc) and the power conversion efficiency yielded to 21.35%. Our findings confirm the enhanced passivation based on the multiple functional groups combination and provide a guideline for new multifunctional passivation molecules in perovskite photovoltaics.

Scattered evidence indicates the occurrence of coral thermal bleaching events during the mid-Holocene. However, information on such occurrences is still very rare. Ten Porites coral cores were drilled from the Wenchang fringing reef of Hainan Island, northern South China Sea. These cores contain mortality surfaces and/or growth discontinuities dating from the mid-late Holocene between 3.4 and 5.7 thousand years ago (ka, before 1950 AD). Monthly Sr/Ca, δ18O and δ13C were analyzed to reconstruct sea-surface temperature (SST), sea-surface salinity (SSS), and photosynthesis intensity during the events. Results show that the mortality surfaces and growth discontinuities of five corals are associated with high SST of 30.3 °C–33.6 °C and high SSS of 34.3–38.3. The abrupt concurrent negative shifts of 1.8‰ or more in δ13C indicate a decrease in the photosynthesis intensity, most likely attributable to the loss of zooxanthellae. These lines of evidence imply that the mortality surfaces and growth discontinuities were the consequence of coral bleaching under abnormally high temperature. The observed recovery directly after bleaching events indicates that corals in the South China Sea are capable of rehabilitation after experiencing severe environmental stresses.

Radioactive isotopes are extremely useful for determining the age of corals, which can also provide extremely useful archives of past climate change and environmental pollution. In this study, we present a novel approach for dating young corals (

Coralline algae are excellent archives for recording paleo-water depth, but to date few studies have used them for long-term paleo-water depth reconstruction. This study focuses on the Plio-Pleistocene section of Well CK2, which was drilled in the northern South China Sea. The section consists of 55.2 m of volcanic basement overlain by 873.55 m of carbonates. The chronological framework of Well CK2 has been well established using magnetostratigraphy and bulk sediment strontium isotope ratios. The Plio-Pleistocene section includes the uppermost 341 m (5.18 Ma). Based on observations of 201 petrologic thin sections, we identified nine coralline algae genera (nongeniculate: Mesophyllum, Spongites, Lithothamnion, Lithoporella, Lithophyllum, and Hydrolithon; articulated: Amphiroa, Jania, and Corallina), and five coralline algal assemblages (Mesophyllum assemblage, Spongites assemblage, Lithothamnion assemblage, Mesophyllum-Lithophyllum assemblage, and Lithoporella-Lithophyllum assemblage). The Mesophyllum assemblage dominates in the interval between 341 and 312 m (5.18–4.36 Ma; early Zanclean) and developed in a water depth between 15 and 25 m. The Spongites assemblage dominates in the interval between 312 and 309 m (4.36–4.28 Ma; middle Zanclean) and is characterized by subspherical rhodoliths (3 to 9 cm in diameter). This assemblage is probably related to the very shallow (0 to 5 m) water of the distal reef flat/reef crest. The Lithothamnion assemblage dominates in the interval between 309 and 200 m (4.28–2.20 Ma) and developed in a reef platform zone at a water depth of more than 25 m. The Mesophyllum-Lithophyllum assemblage dominates in the interval between 200 and 80 m (2.20–1.16 Ma) and developed in a water depth between 15 and 20 m. The Lithoporella-Lithophyllum assemblage dominates in the interval between 80 and 0 m (1.16–0 Ma) and develops in a water depth of 15 m or less. Our paleo-water depths are basically in agreement with global sea-level variations over time, indicating that paleo-water depths in the South China Sea were controlled mainly by eustatic variations. Based on the relationship between coral reef development and water depth, we further divided the Quaternary intervals into four long-term developmental stages. They consist of two catch-up stages: 1) from 5.18 to 4.28 Ma and 2) from 2.2 to 1.16 Ma; a give-up stage from 4.28 to 2.2 Ma; and a keep-up stage from 1.16 Ma to present. Our results confirm that the coralline algae in the coral reefs of the South China Sea can accurately record past water depth variations.

Particulate organic carbon (POC) in the Pearl River estuary (PRE), South China, along a salinity gradient from freshwater to seawater in four months was studied in order to determine its temporal and spatial changes in source and processing. Analytical parameters included chlorophyll-a (Chl-a), POC, and carbon isotopic composition of POC and the dissolved inorganic carbon (DIC) (δ 13 C POC , δ 13 C DIC ). POC varied greatly from freshwater to seawater, exhibiting a significant power law distribution with a rapid decrease (from >2.5 mg l −1 to −1 ) in a narrow salinity range of 0–5 and then a slow decline to ∼0.4 mg l −1 along the large salinity gradient in the estuary. POC was sourced predominantly from in situ phytoplankton, and hence largely reflective of primary production, in February, August, and November as indicated by mostly lower POC/Chl-a values ( 13 C POC and δ 13 C DIC . But in May, soil-derived OC was dominant in freshwater and low salinity estuarine water, as suggested by low POC% in total suspended substance, low Chl-a values and high POC/Chl-a ratios, and higher δ 13 C POC values that was not in parallel with δ 13 C DIC excursion. The offset between δ 13 C POC and phytoplankton δ 13 C (inferred from δ 13 C DIC ) was trivial or positive in salinity

The compound-specific stable carbon isotope compositions (δ 13C) of leaf wax n-alkanes from two short sediment cores recovered off the Pearl River estuary (PRE) were analyzed to check for their capability of indicating decadal scale catchment environmental change. Sedimentary long-chain n-alkanes exhibited an odd-over-even predominance, with a maximum at n-C29 or n-C31, indicating their leaf wax origin was from vascular plants. The δ 13C values of C29 and C31 n-alkane in all the sediment samples were in the range of -28.8‰ to -31.2‰, consistent with the C3 plant-dominated vegetation in the Pearl River catchments. The time series of δ 13C records from the two cores were comparable and displayed a decreasing trend from the early 20th century to the end of the 1970s, followed by a reversal in that change leading to continued increase for ca. 15 years. After being corrected for the effect of atmospheric CO2 rise and δ 13Catm decline, the δ 13C29 records largely retained their raw changing pattern; the post-1980 increase being more conspicuous. The slightly decreasing trend in corrected δ 13C records before around 1980 may have been caused by an increase in precipitation, whereas the subsequent increase of δ 13C is likely associated with the observed dry climate and/or intensive anthropogenic deforestation. Our results thus demonstrate that leaf wax n-alkanes buried in the sediments off the PRE may well reflect change in the regional climate and/or human activity in the river catchments over the past century.