It is now generally believed that elderly may have slightly higher dietary protein requirements than those of the young-middle-aged adults. We have previously conducted related studies by the indicator amino acid oxidation (IAAO) technique, but more research data are needed to revise the protein requirements of the elderly. The main objective was to reevaluate the dietary protein requirements of healthy Chinese adults (65–80 years) without sarcopenia by using the IAAO technique. Nine healthy adult men and seven healthy adult women participated in the study, with protein intakes ranging from 0·1 to 1·8 g/(kg·d). Diets that delivered energy at a 1·5 resting energy expenditure were isocaloric. The amounts of phenylalanine and tyrosine needed to remain constant for each protein dosage. By applying a nonlinear mixed-effects model analysis on the F13CO2 data, which revealed a breakpoint in F13CO2 in response to graded protein intakes, the mean protein requirement was calculated. The mean estimated average requirement (EAR) for healthy elderly Chinese adults without sarcopenia was determined to be 0·94 g/(kg·d). The protein recommended nutrient intake (RNI) determined using various derivation approaches ranged from 1·13 to 1·36 g/(kg·d). The EAR for Chinese adults without sarcopenia aged 65–80 years in this study is 6·8 % higher than the current recommended EAR (0·88 g/(kg·d)). The RNI derived using various derivation approaches are all greater than the current RNI (0·98 g/(kg·d)). This trial was registered with the Chinese clinical trial registry as ChiCTR2200061382.

This study presents the results of a detailed paleoclimate investigation on stalagmite YL-1 (Yelini Cave, Türkiye). YL-1 grew between 117.13 (+0.57/−0.44) ka and 114.87 (+1.63/−2.89) ka within Greenland Stadial 26, indicating a positive moisture balance during the stadial conditions in this semi-arid region. Rainfall is significantly affected by sub-cloud and surface evaporation and decreasing net effective winter precipitation is recorded by high isotope values. Enriched δ18O and δ13C at 116.65 (+0.51/−0.39) ka are interpreted as a drought event that took place ca. 400 years before the end of the MIS 5e. This event, which was reported simultaneously in marine and terrestrial archives in the Northern Hemisphere, is a result of decreased cyclone activity linked to weakening of the Atlantic meridional overturning circulation. 87Sr/86Sr values of YL-1 are close to the host-rock values. Decreased 87Sr/86Sr ratio at 116.67 (+0.54/−0.38) ka reflects the intensified water–rock interaction due to lower precipitation. Along with prior calcite precipitation effect, this is also observed by increased Mg/Ca and Sr/Ca, while low P, Cu, Be, Y, and Zr concentrations indicate a lowered amount of soil-derived colloidal material. The MIS 5e/5d transition is marked by reduced insolation and enriched δ18O at 116.24 (+0.53/−0.86) ka. The Greenland Interstadial 25 phase at 115.87 (+0.83/−1.71) ka is represented by more negative δ18O and δ13C.

The extent to which weed species vary in their ability to acquire and use different forms of nitrogen (N) (inorganic and organic) has not been investigated but could have important implications for weed survival and weed–crop competition in agroecosystems. We conducted a controlled environment experiment using stable isotopes to determine the uptake and partitioning of organic and inorganic N (amino acids, ammonium, and nitrate) by seven common weed and non-weed species. All species took up inorganic and organic N, including as intact amino acids. Concentrations of 15N derived from both ammonium and amino acids in shoot tissues were higher in large crabgrass [Digitaria sanguinalis (L.) Scop.] and barnyardgrass [Echinochloa crus-galli (L.) P. Beauv] than in common lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), and sorghum-sudangrass [Sorghum bicolor (L.) Moench × Sorghum bicolor (L.) ssp. drummondii (Nees ex Steud.) de Wet & Harlan]. In contrast, the concentration of 15N derived from nitrate was higher in wild mustard (Sinapis arvensis L.) shoots than in wild oat (Avena fatua L.) shoots. Root concentration of 15N derived from ammonium was lower in sorghum-sudangrass compared with other species, except for A. retroflexus and A. fatua, while root concentration of 15N derived from nitrate was lower in A. retroflexus compared with other species, except for C. album and S. arvensis. Discriminant analysis classified species based on their uptake and partitioning of all three labeled N forms. These results suggest that common agricultural weeds can access and use organic N and differentially take up inorganic N forms. Additional research is needed to determine whether species-specific differences in organic and inorganic N uptake influence the intensity of competition for soil N.

We measured the concentrations of antifouling biocides in sediment, mangrove leaves and seagrasses from Merambong and Tinggi Island, Johor, Malaysia to evaluate their contamination levels. Although the concentrations of tributyltin (TBT) in mangrove leaves in Merambong in 2013 were significantly lower than those in 2012, the Sea-Nine 211 concentration in 2013 was significantly higher than that in 2012, suggesting that the use of antifouling biocides changed from TBT to Sea-Nine 211. The concentration of each BT (butyltin) and PT (phenyltin) in the mangrove area was significantly higher than the corresponding concentration in the seagrass area in Merambong, but the concentrations of Sea-Nine 211, diuron, chlorothalonil, Irgarol 1051 and M1 in seagrasses were significantly higher than those in mangrove leaves. There were differences in the accumulation profiles of OTs (organotins) and alternative biocides between the seagrass shoots and roots. The concentration of OTs in the seagrass roots was almost the same or higher than those in the shoots, whereas those of alternative biocides shows the opposite pattern to the OTs. Significant high relationships were observed between stable carbon isotope (δ13C) and OTs, Sea-Nine 211 and Irgarols in mangrove leaves. The concentrations of these compounds increased along with the δ13C values of the mangroves. These results suggest that mangroves take up the bicarbonate ions and nutrients in sediment and/or seawater through their roots, along with OTs, Sea-Nine 211 and Irgarols which were accumulated in sediment.

The concentrations of organotin (OT) compounds, butyltin (BT) and phenyltin (PT), in aquatic organisms from Merambong and Tinggi Island, Malaysia, which differ in industrial and economic activities, were measured. Tributyltin (TBT) compounds among BTs ranged from 2.9–28 and <0.1–21 ng g−1 ww in aquatic organisms from Merambong and Tinggi Island, respectively. Triphenyltin (TPT) compounds among PTs ranged from <0.1–25 ng g−1 ww and <0.1–61 ng g−1 ww in aquatic organisms from Merambong and Tinggi Island, respectively. A survey of OT concentrations among the species of OT compounds revealed that the concentrations of BTs and PTs in crabs and clams were high while those in fish were low. Correlation analysis with stable nitrogen isotopes suggest that OT compounds did not accumulate in aquatic organisms through the food web. The measurement of OT compounds in tissues and organs of fish revealed that BT concentrations in liver were higher than those in muscle and that BTs were detected in eggs of fish.

The position of the Banwell Bone Cave mammal assemblage zone (MAZ) in the mammalian biostratigraphy of the British Isles has been the focus of debate for decades. Dominated by fauna typical of cold environments it was originally linked to the marine oxygen isotope stage (MIS) 4 stadial (ca. 72–59 ka). Subsequently it was argued that the Banwell Bone Cave MAZ more likely relates to the temperate interstadial of MIS 5a (ca. 86–72 ka). It is envisioned that “cold fauna” such as bison and reindeer moved into Britain during stadial MIS 5b (ca. 90 ka) and were subsequently isolated by the rising sea level during MIS 5a. Here we investigate environmental conditions during the Banwell Bone Cave MAZ using bone collagen δ13C and δ15N and tooth enamel δ18O and δ13C isotope analysis. We analyse bison and reindeer from the MAZ type-site, Banwell Bone Cave. Our results show unusually high δ15N values, which we ascribe to arid conditions within a temperate environment. Palaeotemperature estimates derived from enamel δ18O indicate warm temperatures, similar to present day. These results confirm that the Banwell Bone Cave MAZ relates to a temperate interstadial and supports its correlation to MIS 5a rather than MIS 4.

The study of paleoclimates enables us to improve and better constrain climate models in order to forecast future climate variations. Marine Isotope Stage 11 (MIS11), which began around 425,000 yr BP and lasted about 65,000 yr, is a warm isotope stage of paramount importance, because the astronomical configuration was similar to the one characterizing the Holocene. Therefore, this warm isotope stage is the most appropriate analog to present-day climate known to date. This study aims to provide new data on sea-surface temperatures (SSTs) inferred from the carbon and oxygen isotope compositions of skeletal carbonates of marine invertebrates preserved in two marine deposits of the Canary Islands located at Piedra Alta, Lanzarote, and Arucas, Gran Canaria. According to published isotopic fractionation equations the marine deposit from Arucas recorded SSTs of 15.9 ± 2.2°C on average, while the tsunamite from Piedra Alta recorded SSTs of 21.2 ± 1.9°C on average. Absolute dating, mollusc assemblages, and calculated marine temperatures suggest that the Arucas marine deposit corresponds to the beginning of MIS11, while the Piedra Alta tsunamite was formed during MIS11c. These results show that low latitudes also experienced sizable SST changes during interglacial stages.

The first ultraviolet photochemical oxidation (UVox) extraction method for marine dissolved organic carbon (DOC) as CO2 gas was established by Armstrong and co-workers in 1966. Subsequent refinement of the UVox technique has co-evolved with the need for high-precision isotopic (Δ14C, δ13C) analysis and smaller sample size requirements for accelerator mass spectrometry radiocarbon (AMS 14C) measurements. The UVox line at UC Irvine was established in 2004 and the system reaction kinetics and efficiency for isolating seawater DOC rigorously tested for quantitative isolation of ∼1 mg C for AMS 14C measurements. Since then, improvements have been made to sampling, storage, and UVox methods to increase overall efficiency. We discuss our progress, and key UVox system parameters for optimizing precision, accuracy, and efficiency, including (1) ocean to reactor: filtration, storage and preparation of DOC samples, (2) cryogenic trap design, efficiency and quantification of CO2 break through, and (3) use of isotopic standards, blanks and small sample graphitization techniques for the correction of DOC concentrations and Fm values with propagated uncertainties. New DOC UVox systems are in use at many institutions. However, rigorous assessment of quantitative UVox DOC yields and blank contributions, DOC concentrations and carbon isotopic values need to be made. We highlight the need for a community-wide inter-comparison study.

Where two species occupy the same habitat and similar niches, competition is likely to drive small-scale spatial niche separation or resource partitioning that may not be immediately apparent. A stable isotope approach was used to investigate potential trophic niche separation between co-existing rocky shore crabs in the North-West (NW) Arabian Gulf. Leptodius exaratus and Pilumnopeus convexus which occupy similar shore height on the same rocky intertidal habitats. We also investigated conspecific differences between males vs females and adults vs juveniles. δ15N results indicated that adults of both species occupy a high trophic level in the rocky shore community, suggesting similar functional roles and potential for competition for food resources, while significant differences in δ13C values indicated differences in dietary sources between the two species, and also changes in diet between juveniles and adults in both species. MixSIAR analysis of δ15N and δ13C data confirmed field observations that both species are generalist omnivores, with potential for direct competition including adult predation on juveniles, including conspecifics. Differentiation in isotopic niches (SIBER analysis) was mainly driven by the significant differences in δ13C values, suggesting that co-existence of the two crab species is at least in part mediated by trophic niche separation or dietary resource partitioning, with some (unquantified) potential for spatial resource partitioning at the microhabitat level.

In order to evaluate effects of three land uses on isotopic compositions of CO2 and O2 of soil air to 5 m soil depth, a field study was conducted in the Calhoun Critical Zone Observatory, located in the subtropical climate of the Southern Piedmont of South Carolina, USA. Soil gas reservoirs were installed in ecosystems with three different land uses, each replicated three times: (i) reference hardwood stands that were never cultivated; (ii) currently cultivated plots; (iii) pine stands, which had been used for growing cotton in 19th century but were abandoned in about the 1930s and 1940s when they were regenerated with pines that are today 70–80 yr old. In addition to soil CO2 and O2 concentration measurements, soil gas samples were analyzed for Δ14C, δ13C, and δ18O. Stable carbon isotopic composition becomes lighter with the depth in soils of all three land uses: in the cultivated site δ13C decreases from –18‰ at 0.5 m to –21‰ at 5 m, in pine site from –22 to –25‰, and in hardwood from –21.5 to –24.5‰, respectively. Δ14C increased with depth from 40 to 60‰ in the top 0.5 m to about 80–140‰ at 5 m depending on land use. While surficial soils had relatively similar Δ14C in CO2, between 40 to 60‰ at 0.5 m, at 3 and 5 m, cultivated soils had the highest Δ14C, hardwood the lowest, and pine in between, a pattern that emphasizes the importance of contemporary respired CO2 in hardwood stands. Oxygen isotopic composition of CO2 did not change with depth, whereas free O2 was greatly enriched in lower horizons of forest soils, which we attribute to strong fractionation by respiration.

Mesothermal, gold-bearing quartz veins are widespread within allochthonous terranes of Alaska that are composed dominantly of greenschist-facies metasedimentary rocks. The most productive lode deposits are concentrated in south-central and southeastern Alaska; small and generally nonproductive gold-bearing veins occur upstream from major placer deposits in interior and northern Alaska. Oreforming fluids in all areas are consistent with derivation from metamorphic devolatilisation reactions, and a close temporal relationship exists between high-T tectonic deformation, igneous activity, and gold mineralization. Ore fluids were of consistently low salinity, CO2-rich, and had δ18O values of 7‰- 12‰ and δD values between −15‰ and −35‰. Upper-crustal temperatures within the metamorphosed terranes reached at least 450-500°C before onset of significant gold-forming hydrothermal activity. Within interior and northern Alaska, latest Paleozoic through Early Cretaceous contractional deformation was characterised by obduction of oceanic crust, low-T/high-P metamorphism, and a lack of gold vein formation. Mid-Cretaceous veining occurred some 50-100 m.y. later, during a subsequent high-T metamorphic/magmatic event, possibly related to extension and uplift. In southern Alaska, gold deposits formed during latter stages of Tertiary, subduction-related, collisional orogenesis and were often temporally coeval with calc-alkaline magmatism.

A comparative study was undertaken to adopt and evaluate a radiocarbon (14C) preparation procedure for accelerator mass spectrometry (AMS) measurements of cremated bones at our laboratory, including different types of archaeological samples (cremated bone, bone, charcoal, charred grain). All 14C analyses were performed using the EnvironMICADAS AMS instrument at the Hertelendi Laboratory of Environmental Studies (HEKAL) and the ancillary analyses were also performed at the Institute for Nuclear Research (ATOMKI). After the physical and chemical cleaning of cremated bones, CO2 was extracted by acid hydrolysis followed by sealed-tube graphitization and 14C measurement. The supplementary δ13C measurements were also performed on CO2 gas while FTIR was measured on the powder fraction. Based on the FTIR and 14C analyses, our chemical pretreatment protocol was successful in removing contamination from the samples. Good reproducibility was obtained for the 0.2–0.3 mm fraction of blind-tested cremated samples and a maximum age difference of only 150 yr was found for the remaining case studies. This confirms the reliability of our procedure for 14C dating of cremated bones. However, in one case study, the age difference of 300 yr between two cremated fragments originating from the same urn shows that other processes affecting the cremated samples in the post-burial environment can substantially influence the 14C age, so caution must be exercised.

Sediments containing terrestrial and aquatic mollusks and ostracodes from the Ziegler Reservoir fossil site (2705 m elevation) near Snowmass Village, Colorado, span ~130–87 ka (MIS 5e through 5b). The southeastern area of the site where taxa were recovered was a relatively fresh, shallow, well-vegetated wetland during MIS 5e through 5c time, approximately 2 m deep, with a total dissolved solids value of ~200–1000 mg L− 1. The wetland was seasonally or annually variable and groundwater discharged along the margins of the bounding moraine. Groundwater likely contributed solutes to the system and may have contributed 18O-enriched water. Based on stable isotopes from ostracode calcite (δ18OOST and δ13COST), seasonal evaporation occurred and the dissolved inorganic carbon pool was unexpectedly enriched in 13C. The mollusk and ostracode faunas changed little across the MIS 5e/5d/5c boundaries, whereas a distinct change in the ostracode fauna occurred between the deposition of Unit 11 and Unit 13, which corresponds in time to the MIS 5c/5b boundary, indicating some combination of increased surface and/or groundwater flow, a decrease in water temperature, and a freshening and a possible deepening of the wetland.

Stable isotopic analysis of carbon and nitrogen in human and faunal remains has been widely used to reconstruct prehistoric diets and environmental changes. Isotopic analysis of plant remains allows for a more extensive consideration of paleodiets and can potentially provide information about the environment in which the crops were grown. This paper reports the results of δ13C and δ15N analyses performed on modern and charred archaeological foxtail millet samples collected from the western part of the Chinese Loess Plateau. The δ13C mean value of modern samples is lower than that of ancient samples. There is a significant difference between grain and leaf δ15N values. These results challenge the standard assumption in isotope studies that the nitrogen isotope signals of the different part of plants consumed by humans and animals are the same. The 3–5‰ difference between human and animal δ15N values is always regarded as an indicator of whether human diets contained considerable animal protein. The difference between grain and leaf δ15N values makes this assumption problematic in a foxtail millet-dominated society.

During the last deglaciation temperatures over midcontinental North America warmed dramatically through the Bølling-Allerød, underwent a cool period associated with the Younger-Dryas and then reverted to warmer, near modern temperatures during the early Holocene. However, paleo proxy records of the hydroclimate of this period have presented divergent evidence. We reconstruct summer relative humidity (RH) across the last deglacial period using a mechanistic model of cellulose and leaf water δ18O and δD combined with a pollen-based temperature proxy to interpret stable isotopes of sub-fossil wood. Midcontinental RH was similar to modern conditions during the Last Glacial Maximum, progressively increased during the Bølling-Allerød, peaked during the Younger-Dryas, and declined sharply during the early Holocene. This RH record suggests deglacial summers were cooler and characterized by greater advection of moisture-laden air-masses from the Gulf of Mexico and subsequent entrainment over the mid-continent by a high-pressure system over the Laurentide ice sheet. These patterns help explain the formation of dark-colored cumulic horizons in many Great Plains paleosol sequences and the development of no-analog vegetation types common to the Midwest during the last deglacial period. Likewise, reduced early Holocene RH and precipitation correspond with a diminished glacial high-pressure system during the latter stages of ice-sheet collapse.

A 30 ka paleo-climate record of the Boise area, Idaho, USA has been delineated using groundwater stable isotopic compositions. Groundwater ages are modern (cold batholith), 5–15 ka (thermal batholith), 10–20 ka (frontal fault), and 20–30 ka (Snake River plain thermal). The stable isotopic composition of groundwaters have been used as a surrogate for the stable isotopic composition of precipitation. Using δ2H and δ18O compositions, local groundwater lines (LGWL's) were defined for each system. Each LGWL has been evaluated with defined slopes of 6.94 and 8, respectively, and resulting deuterium excess values (d) were found for each groundwater system for each slope. Time dependent changes in moisture source humidity and temperature, and Boise area recharge temperatures, calculated from stable isotopic data and the deuterium excess factors, agree with previous paleo-climate studies. Results indicate that from the last glacial maximum to the present time the humidity over the ocean moisture source increased by 9%, sea surface temperature at the moisture source increased 6–7°C, and local Boise temperature increased by 4–5°C. A greater increase of temperature at the moisture source as compared to the Boise area may impart be due to a shift in the moisture source area.

A sediment core from Hulun Lake, Inner Mongolia was analyzed for species assemblages and shell chemistry of ostracodes to investigate changes in the hydrology and climate of the East Asian summer monsoon margin during the Holocene. Darwinula stevensoni was abundant, Ilyocypris spp. scarce, littoral ostracodes absent and Mg/Ca, Sr/Ca and δ18O were low 11,100 to 8300 yr ago, indicating high lake levels and cool/fresh waters. Darwinula stevensoni declined largely, Ilyocypris spp. throve, littoral ostracodes were rare and chemical indicators remained in low values 8300 to 6200 yr ago, suggesting that the lake continued high stands but water became warm. The lake then contracted and water became cool/brackish 6200 to 4300 yr ago. Littoral ostracodes flourished 4300 to 3350 yr ago, marking the lowest lake levels of the entire Holocene. The lake level recovered and water salinity decreased 3350 to 1900 yr ago. From 1900 to 500 yr ago, the lake maintained the preceding status albeit lowered stands and increased salinities 1100 to 800 yr ago. During the recent 500 yr, the lake expanded and water salinity decreased. The data imply that the East Asian summer monsoon did not intensify until 8300 yr ago and weakened dramatically 4300 to 3350 yr ago.

Holocene sediments from Nelson Lake, on Michigan's eastern Upper Peninsula, provide isotopic, pollen, and charcoal evidence for a two-step sequence of changes in moisture source and increased lake-effect precipitation during the late Holocene. Between 8000 and 5300 cal yr B.P., a warm, dry climate and zonal atmospheric circulation produced enriched stable oxygen and carbon isotopic values in combination with high percentages of pine pollen and sustained influx of charcoal particles. After 5300 cal yr B.P., decreasing isotopic values in marl and increasing pollen percentages of mesic hardwoods and northern white cedar indicate increased meridional air flow and precipitation from cold winter storms generated in Alberta, Canada. After 3000 cal yr B.P., abrupt declines in values of δ13C and δ18O and increased pollen representation of hemlock, American beech, spruce, and aquatic plants indicate paludification from increased lake-effect snowfall. The moisture was derived from the Great Lakes and transported by Alberta cyclonic storms that were steered across Lakes Superior and Michigan by a southward shift in the modal winter position of the polar jet stream.