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The service life of RC is dependent upon the superior nature of concrete and its overall quality and excellence as a suitable cover material. Concrete acting as cover material is the only m...

Taiwan is particularly sensitive to changes in monsoonal precipitation and to typhoon-induced heavy precipitation events, however, rainfall variability in Taiwan on centennial and millennial time scales during the Holocene has not been well understood. This study describes mid-Holocene rainfall features of Taiwan based on pollen, total organic carbon (TOC), total nitrogen (TN), and C/N ratio records of core MD05-2908. The step-wise increase in sedimentation rate, fern spore percentage and concentration, TOC content, and C/N ratio suggests an increasing terrestrial material supply due to the intensified rainfall in Taiwan since 6800 cal. yr BP. This rainfall pattern shows an inverse pattern to the decreasing East Asian summer monsoon (EASM) strength represented by the multi-proxy records from North China. Variation of the East Asian summer circulation and associated moisture transport may account for the long-term rainfall changes in Taiwan. Superimposed on this trend, we interpreted three prominent rainfall changes, which focus on the periods of 6800–6600, 1090–880 and 490–190 cal. yr BP. These centennial time scale rainfall variations in our records are linked to the intensity of El-Nino Southern Oscillations.

This study investigated the bulk sediment geochemistry, U–Pb ages and rare earth element (REE) geochemistry of one hundred detrital zircons recovered from the Brujas beach sands in southwestern Gulf of Mexico to understand the provenance and age spectra. The bulk sediments are high in Zr and Hf contents (∼1400–3773 ppm and ∼33–90 ppm, respectively) suggested the abundance of resistant mineral zircon. The chondrite normalized REE patterns of the bulk sediments are less fractionated with enriched low REE (LREE; La CN /Sm CN = ∼491–693), depleted heavy REE (HREE; Gd CN /Yb CN = ∼44–69) and a negative Eu anomaly (Eu/Eu ∗ = ∼0.44–0.67) suggested that the source rock is felsic type. The results of this study revealed highly varied contents of Th (∼4.2–321 ppm), U (∼20.7–1680 ppm), and Hf (∼6970–14,200 ppm) in detrital zircons compared to bulk sands. The total REE content (∼75 and 1600 ppm) and its chondrite-normalized pattern with positive Ce and negative Eu anomalies as well as low Th/U ratio of zircon grains indicated that they were dominantly of magmatic origin. U–Pb data of zircons indicated two age populations, with predominance of Permian-Triassic (∼216–286 Ma) and Neoproterozoic (∼551–996 Ma). The Permian-Triassic zircons were contributed by the granitoids and recycled metasedimentary rocks of the Chiapas Massif Complex. The major contribution of Neoproterozoic zircons was from the Chaucus, Oaxacan, and Chiapas Massif Complexes in Grenville Province, southern Mexico. U–Pb ages of zircons from the Brujas beach are consistent to the reported zircon ages from the drainage basins of Usumacinta, Coatzacoalcos, and Grijalva Rivers in southern Mexico, suggesting that the sediments delivered by the rivers to the beach area are vital in defining the provenance of placers.

•Chennai (India) received the highest rainfall of 490 mm on 1 Dec 2015.•This study looked at NOAA/NESDIS global analysis of SST anomaly (°C).•Revival of 769 km long Buckingham Canal essential for flood mitigation.•Renovating canals, ponds, and lakes crucial for flood prevention.•India needs better strategies to adapt to future extreme weather situations.

Geological sequestration of atmospheric carbon dioxide (CO2) can be achieved by the erosion of organic carbon (OC) from the terrestrial biosphere and its burial in long-lived marine sediments. Rivers on mountain islands of Oceania in the western Pacific have very high rates of OC export to the ocean, yet its preservation offshore remains poorly constrained. Here we use the OC content (Corg, %), radiocarbon (Δ 14Corg) and stable isotope (δ13Corg) composition of sediments offshore Taiwan to assess the fate of terrestrial OC, using surface, sub-surface and Holocene sediments. We account for rock-derived OC to assess the preservation of OC eroded from the terrestrial biosphere and the associated CO2 sink during flood discharges (hyperpycnal river plumes) and when river inputs are dispersed more widely (hypopycnal). The Corg, Δ14Corg and δ 13Corg of marine sediment traps and cores indicate that during flood discharges, terrestrial OC can be transferred efficiently down submarine canyons to the deep ocean and accumulates offshore with little evidence for terrestrial OC loss. In marine sediments fed by dispersive river inputs, the Corg, Δ14Corg and δ 13Corg are consistent with mixing of terrestrial OC with marine OC and suggest that efficient preservation of terrestrial OC (>70%) is also associated with hypopycnal delivery. Sub-surface and Holocene sediments indicate that this preservation is long-lived on millennial timescales. Re-burial of rock-derived OC is pervasive. Our findings from Taiwan suggest that erosion and offshore burial of OC from the terrestrial biosphere may sequester >8 TgC yr−1 across Oceania, a significant geological CO2 sink which requires better constraint. We postulate that mountain islands of Oceania provide a strong link between tectonic uplift and the carbon cycle, one moderated by the climatic variability which controls terrestrial OC delivery to the ocean.

Sediment core OS03-1 retrieved from the Akademia Nauk Rise in Southern Okhotsk Sea was analyzed for the contents of rare earth elements (REEs) and combined with carbon isotope (δ13C) time series of benthic foraminifera to infer changes in terrigenous accumulation and bottom water ventilation on glacial–interglacial timescales in the study area. The age model of OS03-1 was constructed by a combination of foraminifer δ18O stratigraphy and 14C AMS dating, revealing that the 380 cm long core provides a window on climate change in the southern Okhotsk Sea since ∼180 ka. A grain size-controlled-REE content shows strong glacial–interglacial changes. The Cerium and Europium anomalies vary from 0.89 to 1.32 and from 1.14 to 1.37, respectively. The (La/Yb)N values range between 0.55 to 0.92. Both results suggest a significant contribution of volcanic debris in the core sediments. In addition, the relationships between Sm vs. Nd suggest main contribution origin from the Amur River and sea ice during warm intervals and from the sea ice during cold intervals, indicating that the sea ice played an important role in transporting terrigenous materials to the study site in the southern Okhotsk Sea. During the last 180 ka, the mass accumulation rates (MAR) of ∑REEs are relatively higher during glacials and lower during interglacials with a peak accumulation during the early deglacial period. We infer that an intensified Mongolia High is responsible for the first-order accumulation pattern of ∑REEs in the southern Okhotsk Sea by mediating the dynamic changes in sea ice extent. Furthermore, six δ13C minima are associated with intensified Asian monsoon (AM) precipitation and maximum MARs of ∑REEs, indicating that the dominance of barrier layer effects by high fresh water input through sea ice melting. The maximum MAR of ∑REEs during the Marine Isotope Stage (MIS) 5c coincides with the minimum of benthic foraminiferal δ13C, indicating a major interruption of ventilation in the bottom water in the Okhotsk Sea. The major low ventilation event in the deep water of the Okhotsk Sea appears to be dampened by a cooling condition and a major blooming of surface productivity preceded the event.

We used multi-decadal pollen and diatom records from sediment core TFL-1 from Tsuifong Lake to reconstruct the vegetation dynamics and hydroclimate in northeastern Taiwan during the past 3500 cal BP. Coarse grained sediments in association with higher percentages of wetland pollen (Cyperaceae) and upper conifer pollen (Tsuga and Pinus) in the lower part of the core indicate low lake levels and a relatively cold/dry climate between 3500 and 2030 cal BP, reflecting a decline of the East Asian summer monsoon (EASM). Muddy sediments coupled with reduction of wetland pollen represent the rise of lake levels, implying the re-strengthening of the EASM during the past 2000 years. Paleotemperature was inferred from the variation of pollen origin from the upper and lower mountain forest, indicating the global temperature anomalies of the Medieval Warm Period (MWP) and the Little Ice Age (LIA). In comparison to the main climate forces in the North Pacific, we suggest that the long-term climatic trend in Taiwan was controlled by variations in EASM intensity, while increased precipitation over the past 2000 years may also be linked to warmer sea surface temperature (SST) of the western Pacific Warm Pool (WPWP) and increased El Nino-Southern Oscillation (ENSO) events, which increased typhoon intensity. Higher diatom-inferred pH during 2930–2030 cal BP and the LIA suggest strong hydrological disturbances, reflecting more typhoons passing over Taiwan. The frequent typhoon events could be linked by an abrupt shift of typhoon track, due to the reduction of the WPWP and expansion of the Northwestern Pacific High, which move typhoons in a more westerly direction.

Reconstruction of modern climate and environmental changes in east Asia using inland natural climate archives can provide valuable insights on decadal–multidecadal climate and environmental patterns that are probably related to both natural and anthropogenic forcing. Here we investigated an 89-cm-long sediment core (TH1) from Tian Lake, southeastern China, for sedimentological, physical and geochemical parameters in order to understand climate and environmental changes for the latest two centuries. 137Cs- and 210Pb-based age models show that the fine sand–coarse silt-dominated core contains ~170 years (c. AD 1842–2011) of continuous sedimentation. Sediments with fine sands, low MS values, high water content, high TOC content and a high C:N ratio from c. AD 1842 to 1897 suggest intense hydrological conditions and strong runoff in the catchment, probably because of a humid climate. From AD 1897 to 1990, sediments with very fine sand and coarse silt, high MS values, low water content and unchanged TOC and C:N ratios indicate normal hydrological conditions and in-lake algae-derived organic matter. During this interval, the chemical weathering indicators show stronger weathering conditions compared with sediments deposited during AD 1842–1897, supporting the dominance of weathered surface soil input in the earlier interval and physical erosion dominance in the later period, respectively. Since AD 1990, the continuous decrease of geochemical proxies suggests human-interacted Earth surface processes in the catchment of Tian Lake. A PCA revealed four dominant geochemical controlling factors – detrital input, trophic status, grain size and early diagenesis –, accounting for 26, 20, 18 and 16% of total variance, respectively. This study for the first time provides lacustrine geochemical evidence for the most recent two centuries of climate and environmental changes in coastal southeastern China, a region that is currently undergoing an inversion of critical zone, i.e. an overturning of its soil profile, owing to swift modernization.