Stable Isotope Results Research Articles

Subsistence economy in the eastern Ordos Plateau, China during the late Warring States Period (c. 221 BCE) by stable isotope analysis

This case study presents stable carbon and nitrogen isotopic results of 40 human bones (δ13C value range: −9.7 ‰ ∼ −7.7 ‰, mean ± SD value: −8.6 ± 0.4 ‰; δ15N value range: 6.7 ‰ ∼ 10.0 ‰, mean ± SD value: 8.3 ± 0.7 ‰) from the Chuanzhang cemetery in the eastern Ordos Plateau, China during the late Warring States Period (c. 221 BCE), which indicate that the past populations mainly relied on C4-based food. Despite different archaeological cultures, all past populations in the Chuanzhang cemetery had a similar dietary pattern and subsistence economy. Based on archaeological and historical analysis, people in the Chuanzhang cemetery made their living mainly by millet-based agriculture, supplemented by animal husbandry. Comparing isotopic data published from adjacent and contemporary cemeteries, we can conclude that millet-based agriculture was a consistency and dominated subsistence economy in central-south, Inner Mongolia, which also provided a solid material foundation for the central plains government to control the eastern Ordos Plateau during the late Warring States Period.

Compound-specific radiocarbon analysis of sedimentary fatty acids: Potential as a dating tool for lake sediments of Mt. Fuji volcanic region, Japan

Compound-specific radiocarbon analysis (CSRA) is a promising tool for dating sediment sequences where traditional dating methods are impractical. However, the applicability of CSRA of short-chain fatty acids as a dating tool remains poorly understood, especially in lacustrine settings. Accordingly, we determined the radiocarbon content (Δ14C) of individual fatty acids in sediments of Lake Yamanaka (central Japan), as well as their stable carbon and hydrogen isotope ratios, to evaluate the potential of CSRA as a dating tool in volcanic lake environments. We found that the Δ14C values of plant-derived (C24, C26, and C28) n-fatty acids (–99‰ to –149‰) were considerably lower than the Δ14C of charred plants (139‰) within the sediments and those of living aquatic plants (–52‰ to –58‰) in Lake Yamanaka, suggesting that contributions from pre-aged terrestrial and aquatic plant materials likely affect these acids. Similarly, the Δ14C of C16n-fatty acid (–95‰) in surface sediments was much lower than the Δ14C of modern aquatic plants (–52‰ to –58‰), as well as the Δ14C of dissolved organic carbon (DIC) in surface water (–48‰). Together with the stable isotope results, we conclude that in addition to autochthonous aquatic sources, contributions from pre-aged terrestrial carbon sources significantly affect the Δ14C of C16n-fatty acids. Comparing fatty acid Δ14C and concentration data across lakes within the Mt. Fuji region suggests that CSRA of the C16 acid provides valid chronological information only when the C16 originates exclusively from autochthonous aquatic sources, with minor allochthonous terrestrial input.

Does montane meadow restoration influence the mineral association and stability of soil carbon?

Soil carbon (C) stability is an important consideration for management that aims to increase long-term C storage. The fraction of soil C allocated to physico-chemically protected mineral-associated organic matter (MAOM) is a common soil C stability benchmark. However, the reality of soil C persistence is more complex than MAOM content alone—particularly in ecosystems such as meadows with high rates of belowground C inputs that can stimulate MAOM decomposition. Here, we combined three metrics of soil C persistence to characterize soil C stability across a meadow restoration chronosequence averaging belowground C gains of 330 g C m−2 y−1 for ~20 y. The metrics were: (1) the fraction of soil C in MAOM and particulate organic matter (POM), (2) the susceptibility of soil C to decomposition under varying temperatures, and (3) the utilization of MAOM-C by microbes. Two metrics suggested soil C stability may increase following montane meadow restoration. As soil C concentration increased with restoration, C storage in MAOM, but not POM, increased (metric 1). The susceptibility of MAOM-C to decomposition (microbial respiration relative to MAOM-C) decreased with increasing soil C concentration across temperatures (metric 2). Stable isotope results could not definitively determine the source of carbon dioxide efflux (metric 3) but generate hypotheses for future research to address. We posit that C sequestered following montane meadow restoration could be stable, with implications for regional C storage objectives. Further, our data point toward complex mineral-associated C dynamics including the potential importance of plant inputs for MAOM formation in meadow soils.

Niche partitioning and competition between different rabbit breeds using stable isotopes

Stable isotope analysis (SIA) is an evolving method for determining diet, understanding food web and resolving biogeochemical issues in the ecosystem. This study aims to trace out ecological niche preferences/partitioning and competition among the lagomorphs, including two different breeds of European rabbit (Oryctolagus cuniculus), New Zealand rabbit and American Dutch rabbit, using SIA. Thirty-two samples of tooth enamel were analysed, which were collected from different districts of Punjab, Pakistan, including Okara, Sahiwal and Kasur. Among these samples, 16 belonged to the New Zealand breed (08 male and 08 female rabbits) and 16 to the American Dutch breed (08 male and 08 female rabbits). Significant (P<0.001) intergender differences in the isotope content of δ13C in the enamel for New Zealand and American Dutch rabbit were found. The European rabbits showed significant differences for both genders in the stable isotope of oxygen in the enamel (δ18O) values (P=0.05). Nitrogen stable isotope results showed no significant intergender differences between American Dutch and New Zealand rabbits (P=0.24). The stable isotope results for δ13C, δ15N, and δ18O indicate that the trophic niche partitioning of both breeds overlaps, which can potentially cause competition for resources, whereas the water intake may differ among different genders, which may reflect differential gender-related activities. The archaeological and fossilised data of lagomorphs is present, but there is no significant literature available for living lagomorphs (rabbits). In general, this study provides a basic and first dataset for δ13C, δ15N, and δ18O of living lagomorphs, which can serve as a comparative dataset for future studies.

Spatial heterogeneity of sedimentary organic matter sources in the Yangtze River estuary: Implications from fatty acid biomarkers

This study investigated the sources of sedimentary organic matter (OM) in the Yangtze River estuary (YRE), using multiple biomarkers. The results of stable carbon isotope (δ13C) and total organic carbon to nitrogen ratio (TOC/TN) suggests the contribution of marine-derived OM significantly increased seawards, while fatty acid (FA) composition provides more specific information on OM sources. In total, 30 components of FAs were identified at the studied 17 sites, which mainly composed of phytoplankton FA, followed by ubiquitous FA and bacterial FA, while terrestrial FA contributed less to the total FAs. Under the strong impacts of the large physicochemical gradients in the YRE, TOC, TN and FA components showed higher concentrations in the estuary mixing zone (especially within the turbidity maximum zone), attributing to their strong binding with OM-enriched fine particles. The spatial heterogeneity of sedimentary OM sources was highly impacted by salinity and Chl-a, as well as bacteria-mediated OM degradation.

Groundwater quality constrains and new opportunities for water supply from hard rock aquifers in a fast-expanding city of Sub-Saharan Africa, Yaoundé-Cameroon

Expanding cities and their water utilities face a significant challenge ensuring safe and sufficient water supply within a context of great uncertainty. Population growth, urbanisation and economic fluctuation coupled with climate variability further exacerbate these problems in Sub-Saharan Africa (SSA).The study focusing in Yaoundé-Cameroon, Central Africa demonstrates quality constrains and new opportunities of water supply from hard rock aquifers. Stable isotopes and hydrochemical parameters of 56 boreholes, 57 dug wells, 31 springs and 22 rivers, sampled in the dry and wet seasons were used to provide visibility of the groundwater system in addition to its interaction with surface water. Stable isotope results of δ18O and δ2H show uniform mixing of the groundwater masses from rainwater infiltration. Groundwater chemical compositions show variable mineralisation, linked to the environment in which water circulates and the land use change, reflecting classical polluted NaK–NO3 urban groundwater type and CaMg–HCO3 natural water quality in the peri-urban area. The enriched shallow urban groundwater is further reflected in surface water indicating interaction of the two water masses. Hydrochemical processes reveal pollution constrains in urban groundwater uses and the importance of rock-water interaction and residence time in the peri-urban groundwater. The defined NBL/TV coupled with the new water supply scheme could be helpful in the land use management practices, monitoring of the natural water quality and improving access to safe drinking water in SSA.

Network Analysis Reveals Species-Specific Organization of Microbial Communities in Four Co-Occurring Elasmobranch Species along the Georgia Coast

Comparing co-occurring species may provide insights into how aspects of ecology may play a role in influencing their microbial communities. During the 2019 commercial shrimp trawl season off coastal Georgia, swabs of skin, gills, cloaca, and gut were taken for three species of batoids (Butterfly Ray, Bluntnose Stingray, and Atlantic Stingray) and one shark species (Atlantic Sharpnose) for high-throughput sequencing of the V4 region of the bacterial 16S rRNA gene. White muscle was analyzed for stable isotopes (δ13C and δ15N) to evaluate potential niche overlap in these four sympatric mesopredators. Significant differences were found in both δ13C and δ15N signatures across species, suggesting a degree of resource partitioning. When examined within tissue type, the host species had a weak effect on β-diversity for cloaca and skin, with no differences found for gill and gut samples. However, network analysis metrics demonstrated a stronger species-specific effect and distinct microbial community relationships were apparent between the shark and batoids, with the former having tighter networks for both internally- and externally-influenced tissues (gut/cloaca and skin/gills, respectively). Despite overlapping habitat use, species’ microbiomes differed in their organizational structuring that paralleled differences in stable isotope results, suggesting a mediating role of species-specific ecology on bacterial microbiomes.

Conservation implications of isotopic variation in nails and blood with wetland quality in three species of Australian freshwater turtle

Abstract Australian freshwater turtles are declining, reflecting global turtle trends. Understanding variation in turtle diets and habitat requirements can guide protection and restoration of ecosystems. Diet and niche overlap were investigated in three co‐existing species of turtle—the broad‐shelled turtle Chelodina expansa, the eastern long‐necked turtle C. longicollis and the Macquarie turtle Emydura macquarii, in three rivers in the Murray–Darling Basin, Australia, in relation to environmental variables. Dietary variation in relation to water quality (salinity) and macrophyte cover was investigated using stable isotope analyses (δ15N and δ13C) of turtle tissues (plasma, red blood cell, whole blood and nail) representing food assimilation over different antecedent periods. These stable isotope results were consistent with current dietary understanding based on stomach flushing, indicating that isotope analyses are a non‐invasive method for obtaining dietary information. There were temporal dietary differences, with strong shifts between spring and summer sampling periods, particularly in the blood plasma. Intraspecific variation in diets reflected in δ15N and δ13C related to body size. There was evidence of high dietary overlap among the three species, potentially creating competition, particularly when they co‐occur or resources might be limited. Continued degradation of turtle habitats and water quality affects turtle diet and reduces habitat availability, forcing the three species of turtle to co‐exist in diminishing refugia, increasing interspecific competition for food. Protecting and restoring freshwater ecosystems, including maintaining freshwater refugia, is essential to conserve already declining populations of the three Australian freshwater turtle species.

The Pleistocene grassland-dominated mammal fauna from Tham Kra Duk (Nakhon Si Thammarat, Peninsular Thailand)

ABSTRACT Controversy exists as to whether the Pleistocene vegetation in northern Sundaland was dominated by lowland tropical grasslands or rainforests, due to limited palaeoecological evidence recorded from the region. We describe a new Pleistocene large mammal fauna from Tham Kra Duk, a cave in the Tham Phedan mountain, Nakhon Si Thammarat Province in Peninsular Thailand, with emphasis on its palaeoecological and palaeoenvironmental investigations using the stable isotope analysis of mammalian tooth enamel. The fossil site has yielded at least nine mammalian taxa almost comparable to late middle to latest Pleistocene faunas in the mainland, thus suggesting the same biogeographic mammal elements with a range extension south of the Kra Isthmus. The stable isotope results indicate that mixed woodland to grassland ecosystems were dominated by C4 vegetation in the area. This supports the assumption that the expansion of Pleistocene tropical savanna ecosystems might have held the key to facilitating the southward distribution range of grazing mammals such as gaurs and Himalayan gorals into the Thai-Malay Peninsula. The presence of the Tham Kra Duk fauna was probably linked to some major biogeographic events of Pleistocene hominin and mammal migration through the land-bridge peninsula into the islands of Southeast Asia during a period of glaciation.

Groundwater chemistry and isotope for interpreting the hydrogeological conditions and hydrochemical evolution of multilayer aquifer system of Donghai island, China

Groundwater is generally important water resource for islands. Groundwater recharge source and its hydrochemical characteristics are vital issues for the sustainable development and management of island groundwater resources. In this study, taking Donghai island which is featured with multi-layer aquifer structure as an example, by comprehensive using of statistical analysis, stable isotope (2H-18O), Gibbs diagram and ion ratio graph, we conducted a comprehensive hydrochemistry investigation for the groundwater in the shallow aquifer (i.e., phreatic and feeble confined aquifers) and middle confined aquifer of this island. And the hydrochemical characteristics, recharge sources, hydrogeochemical processes and source of element components of groundwater in different aquifers of Donghai island were identified. The results show that the major ions and TDS of the shallow groundwater are higher than those of the confined groundwater, and that those aquifers have not suffered significant seawater intrusion. The main hydrochemical types of shallow groundwater and confined groundwater are Cl·SO4-Ca·Na and HCO3-Na·Mg, respectively. Different hydrochemical types and chemical component concentrations between these two aquifers indicate that the hydraulic relationship between aquifers is relatively weak. The results of 2H-18O stable isotope and deuterium excess indicate that the shallow groundwater originated from local precipitation and that the recharge period of the confined groundwater is different from the shallow groundwater. Results of ion ratio reveal that the island groundwater hydrochemistry is mainly controlled by the water-rock interaction, featuring with dissolution of silicate rocks (such as sodium feldspar, potassium feldspar, calcium feldspar and biotite). In addition, cation exchange is also an important hydrogeochemical process controlling the hydrochemical composition of the confined groundwater. The results will be helpful for understanding of the local island hydrogeology and be supportive for the groundwater resources quantitative research such as numerical modeling for Donghai island.

Multiscale characterization of an extensive stromatolite field: a new correlation horizon for the Crato Member, Araripe Basin, Brazil

ABSTRACT There is wide recognition of lacustrine sediments as excellent archives of a basin’s depositional history due to their high sensitivity to environmental changes. Among them, microbial limestones are one of the most valuable tools for paleoenvironmental reconstruction, because the biological agents responsible for their genesis tend to respond to short-lived variations of the depositional setting creating specific precipitation patterns. We here document and investigate the sedimentary features of a specific sedimentary layer, remarkable by the extraordinary lateral continuity of its textural attributes over kilometer distances. This marker horizon occurs among the first carbonate layers of the Crato Member (Aptian, Araripe Basin, NE Brazil), commonly assigned a paleolacustrine system. We build on a multiscale comparative analysis (mesoscale, microscale, and chemical) to outline the main processes and paleoenvironmental settings that prompted this interval’s widespread and laterally nearly uniform deposition. A lamination pattern identified in different well cores was scrutinized and compared, and shows striking lateral continuity attesting to autochthonous biologically induced mineralization as the primary mechanism of the formation of the microbialites. Compositional and stable-isotope results also show similar trends throughout the well cores, where minor differences represent the influence of local processes. The studied interval encompasses the relatively swift transition of organic shales rich in ostracod valves to planar stromatolites, where both developed in the anoxic benthonic zone of a freshwater lake. The precipitation of the overlying thinly laminated limestones is related to a change in the carbonate genetic mechanism as a response to a more stable lacustrine stratification. The widespread formation of microbialites preserving an almost identical textural pattern must be related to a regional event, constituting a rare example of a preserved ancient biostrome. Moreover, the investigation of this sedimentary layer can further contribute to determining the roles of different biotic and abiotic processes in microbialite precipitation over large areas.

Subsistence strategies in the Inner Congo Basin since the 14th century AD: the faunal remains from Nkile and Bolondo (DR Congo)

The faunal remains are described from Nkile and Bolondo, two archaeological sites in the equatorial rainforest of the Democratic Republic of Congo. Both river-side settlements, located in the Ruki-Tshuapa basin and dating to between the 14th century to the second half of the 20th century, show a heavy reliance on aquatic food resources. The animal remains show that fishing was a major subsistence activity, whereas hunting, slaughtering of domestic stock and harvesting of molluscs were less frequent activities. The contribution to the diet of the different animal taxa suggested by the zooarchaeological data is in line with recently published stable isotope results obtained on humans and animals from Bolondo. The type of fish, and in particular their reconstructed sizes, show that the major exploited fishing grounds were shallow waters that became accessible during the low water seasons (nowadays July-August and a minor season in March at both sites). The proportions of the exploited fish taxa are comparable to those marketed nowadays in larger urban centres. Juvenile fish, and to some extent, small crocodiles, were heavily exploited but it is argued that at the time this was still a sustainable activity that did not deplete the fauna as much as today since human populations were smaller and the fishing gear less effective.

Identifying Karst Aquifer Recharge Area Using Environmental Stable Isotopes and Hydrochemical Data: A Case Study in Nusa Penida Island

Identifying the recharge area of karst aquifers is scientifically challenging due to the complexity of karst groundwater flow characteristics. It is essential to identify the recharge zones to conserve the groundwater resources contained within these aquifers. This paper proposes a combined methods for identifying recharge area of karst aquifers on Nusa Penida Island using stable isotopes (18O and 2H) and a hydrogeochemical approach. Based on the analysis of δ18O and δ2H values and their spatial distribution, it is possible to retrace karst aquifer recharge areas using average isotope elevations. In the meantime, groundwater facies will be determined in the karst region of Nusa Penida using the hydrogeochemical approach with the Piper diagram. According to the calculation of water stable isotope results, the average elevation of the groundwater recharge area at the study site is between 62 - 450 meters. If applied to the location of the study, the recharge area is almost entirely distributed across Nusa Penida. In addition, based on the hydrogeochemical analysis, the groundwater type at the study site can be divided into three categories: Na-Cl, mixed, and Mg-HCO3. The water types indicate that the groundwater in Nusa Penida comes from a combination of old water stored from its internal geological formations and mix with modern rainwater.

Hydrochemical Characteristics of Groundwater and Their Significance in Arid Inland Hydrology

Phreatic groundwater hydrochemistry is important for sustainable water utilization and ecological stability in arid regions. Based on the test data from collected water samples, this study explored the phreatic groundwater recharge, hydrochemical evolution, and quality of the Sugan Lake Basin using hydrogeochemical, isotopic, and multivariate statistical analyses. The stable isotopic results showed that the phreatic groundwater in the alluvial fan, plain, and wetland areas of the basin generally originated from modern water, and the phreatic groundwater in the piedmont was mainly recharged by paleowater under low-temperature conditions. Carbonate is the dominant mineral in the regional rock weathering process. Phreatic groundwater in the piedmont is controlled by mineral dissolution and cation exchange; however, phreatic groundwater in other areas of the basin is significantly affected by river infiltration. This indicates that the hydrochemical regime of phreatic groundwater is sensitive to natural river flow without disturbing human activity. Class I–V groundwater samples accounted for 2.86%, 25.71%, 34.29%, 14.29%, and 22.86%, respectively. Total dissolved solids, total hardness, sulfate, chloride, nitrite, Na, Fe, Hg, and Cr VI are important factors that determine groundwater quality. This study deepens the understanding of phreatic groundwater hydrochemical characteristics and hydrologic cycles in the Sugan Lake Basin and provides background values of hydrochemistry without human interference for further study in arid inland basins.

Exceptional preservation in Quaternary Atacama Desert Tufas: Evidence for increased groundwater and surface water in the Calama Basin, Atacama, Chile

AbstractExceptionally well‐preserved tufas located west of Calama, Atacama Desert, Chile, designated Santa Juana tufas, record episodic wetter conditions, relative to today, over the past 500,000 years. Globally, tufa architecture and depositional details are poorly understood as most described tufas have been degraded by weathering and erosion. In the hyperarid Atacama, post‐depositional alteration is negligible, therefore, the exceptional preservation of Santa Juana tufas documented in this study provides new information about tufa facies and their complex interactions. Santa Juana facies include microbial stromatolites, phytoherms, cascadestone, flowstone and porous limestone. Phytoherms, consisting of former plant stems coated with calcite, developed in channels, within pools, and along spring discharge aprons. Cascadestone, representing former waterfalls, preserves microbial filaments and delicate V‐shaped calcite crystals. Flowstone lines shallow subvertical to subhorizontal channels, representing sites of rapidly sluicing water flow. Porous limestone, containing sparse calcite and/or gypsum and anhydrite cement crystals, represents detrital accumulations. Stable isotope results, coupled with U/Th ages, show that by the Quaternary, relative to the Neogene, groundwater was less supercharged with volcanogenic CO2 so degassing was moderated. The δ18O ratios from Miocene–Pliocene palustrine and lacustrine freshwater carbonates that underlie Santa Juana tufas indicate significant evaporation, but the tufa δ18O signal indicates a less evaporative trend due to shorter atmosphere exposure time. Biological fractionation in δ13C is largely masked by the region's volcanogenic carbon footprint, although tufa petrography shows well‐preserved microbial filaments and laminations. The range of tufa ages in this study shows that there were wetter time periods within the drainage basin headwater area in the Quaternary, but that by the late Pleistocene to early Holocene, aridity to hyperaridity became established. The lack of diagenesis or alteration within the Santa Juana tufas indicates that there has been minimal rainfall since their deposition.

안정동위원소 분석을 통한 신석기시대 생업에 관한 연구의 성과와 방향

Although the question of the subsistence strategies in the Neolithic period is a central topic in Korean archaeology, the changes in subsistence activities have been investigated on the basis of preserved fauna and floral remains. Most previous studies on subsistence patterns have focused on the quantitative analysis of floral and fauna remains preserved in the shell middens. In contrast to traditional methods such as quantitative analysis of floral and fauna remains, stable isotope analysis provides a direct measurement of past human diets. This method provides information about whether individuals derived the protein in their diet from plant or animal sources.
 Until now, stable isotopic results of humans from Neolithic period (Ando, Janghang, Daepo, Tongsamdong humans) revealed that the Neolithic people were mainly dependent on marine food resources as hunter-gatherers. Based on the stable isotope data, we can propose that marine resource exploitation was the main subsistence strategy in the Neolithic period. However, there is also a regional difference in stable isotope values between west (Konamri human) and east-south coast. This indicates that there might be a possibility to have regional difference in subsistence strategies during Neolithic period.

Positive response of nitrite-dependent anaerobic methane oxidation to both gradual and abrupt increases of atmospheric CO2 concentration in paddy soils

The global ongoing increase in the atmospheric CO2 concentration is a gradual rather than an abrupt process. Although the abrupt increase in atmospheric CO2 concentration has been reported to greatly affect nitrite-dependent anaerobic methane oxidation (n-damo), the effect of a gradual increase in atmospheric CO2 concentration on n-damo remains unclear. To better evaluate the role of n-damo in paddy soils, this study investigated the responses of n-damo to different CO2 treatments: the ambient CO2 concentration (CK), a gradual increase (GI), and an abrupt increase (AI) in the CO2 concentration across different growth periods and soil depths. The 13CH4 stable isotope and quantitative PCR results revealed that compared to the CK, GI and AI significantly increased the activity of n-damo by 91.6 % and 90.0 % (p < 0.05), respectively, and also significantly increased the abundance of Candidatus Methylomirabilis oxyfera (M. oxyfera)-like bacteria by 67.7 % and 98.6 % (p < 0.05), respectively. Although there was no significant variation between GI and AI. In addition, the activity and abundance differed significantly between growth period and soil depth. The high-throughput sequencing results showed that GI and AI had little effect on bacterial community, while the soil depth had a significant impact on bacterial community. The changes in several soil physiochemical factors (e.g., the contents of soil water, organic carbon, and inorganic nitrogen) had important impacts on n-damo activity and the bacterial community structure. Overall, the results indicate a positive and similar response of n-damo to both gradual and abrupt increases in the atmospheric CO2 concentration in paddy soils.

Multiproxy paleodietary reconstruction using stable isotopes and starch analysis: The case of the archaeological site of Playa del Mango, Granma, Cuba

Paleoethnobotanical and stable isotope studies have demonstrated that the indigenous groups that populated the Antilles, traditionally understood as dependent exclusively on wild resources, cultivated and consumed both C3 and C4 plants even before the arrival of the ceramic-bearing Arawak groups. However, the relative importance of cultigens and the differential use of plants, especially maize, between populations and individuals remains unknown. In this paper we combined the analysis of stable isotopes (δ15N, δ13Cco, δ13Cen, δ13Cap, δ34S) of 27 individuals from the archaeological site of Playa del Mango, Cuba with the identification of starch grains in dental calculus. The stable isotope results indicate that the sampled population had a 70:30 C3/C4 diet, where at least 65 % was based on C3 protein. Starches from C3 (e.g., Marantaceae, Ipomoea batatas) and C4 plants (Zea mays) were found in similar proportions (50:50). These results support that the lack or abundance of starch grains cannot be used to infer directly the frequency at which C3 and C4 plants were consumed within a small population. Statistically significant differences between females and males in the carbon isotope composition of diet, and its energy portion, suggests a differential consumption of plants by sex. Playa del Mango individual diets were statistically different from those of coeval sites, supporting our previous findings that groups with different dietary traditions concurrently inhabited Cuba in precolonial times. The study demonstrates the power of combined use of stable isotope models, and starch analysis, to provide a more nuanced reconstruction of dietary practices in past human populations.

Validation of lipid extraction and correction methods for stable isotope analysis of freshwater food webs in southern Africa

Stable isotope analysis is ubiquitous as a method to investigate food-web dynamics at various scales in aquatic ecology. Most studies make use of dorsal muscle tissue, which involves lethal sampling of the fish. The sampling of muscle tissue is often followed by chemical lipid extraction pre-treatment before stable isotope analysis. In this study we tested whether stable light isotope results obtained from fin tissue were comparable to those from muscle, and we investigated whether lipid correction could be used as a substitute for lipid extraction. Various lipid correction equations were evaluated. Based on our results, we propose ethical and efficient methods of sample collection and preparation for stable isotope analysis of freshwater fish. We found that dorsal muscle and fin tissue samples could yield similar interpretations of freshwater food-web dynamics in South Africa, demonstrating that fin clippings might be more widely applied as a nonlethal sampling method for stable isotope studies. Existing lipid correction equations either over- or underestimated true lipid extracted δ13C values, therefore an amended lipid correction equation is proposed as it was successfully tested against a population of wild fish. The errors arising from existing lipid correction equations suggest that site-specific calibration should be employed.

Comparison of pollution status and source apportionment for PCBs and OCPs of indoor dust from an industrial city.

In this study, the pollution status of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) was investigated in indoor and outdoor dust from three different functional areas of Hefei, China. The relationship between the concentrations of PCBs and OCPs and different influencing factors in dwellings was studied. The results showed that the concentrations of PCBs and OCPs were higher in samples from dwellings with higher smoking frequency, lower cleaning frequency, higher floors and smaller household size. The results of Spearman's correlation coefficient analysis indicated that PCBs and OCPs were not consistently associated with each other, while sources of low-chlorinated PCBs and high-chlorinated PCBs were different. Scanning electron microscopy (SEM) shows the shape of indoor dust was a mixture of blocky, flocculated, spherical structures, and irregular shapes. The results of principal component analysis (PCA) and positive matrix factorization model (PMF) showed that the PCBs and OCPs of indoor dust came from both indoor and outdoor sources between local and regional transport. Carbon (δ13C) and Nitrogen (δ15N) stable isotope results indicate or show that the indoor dust (δ13C: - 24.37‰, δ15N: 6.88‰) and outdoor dust (δ13C: - 12.65‰, δ15N: 2.558‰) is derived from fossil fuel, coal combustion, road dust, fly ash, C4 biomass and soil. Potential source contribution factor (PSCF) and concentration weighted-trajectory analysis suggest that sources of pollutants were local and regional transport from surrounding provinces and marine emissions. The average daily dose (adult: 8.20E-04, children: 2.37E-03) of pollutants and the carcinogenic risks (adult: 1.23E-02, children: 2.65E-02) were relatively greater for children than adults. This study demonstrates the utility of SEM to characterize indoor dust morphology while combining PMF, PSCF, and stable isotope methods in identifying indoor PCBs and OCPs sources and regions.