How temporal patterns in rainfall determine the geomorphology and carbon fluxes of tropical peatlands

Tropical peatlands now emit hundreds of megatons of carbon dioxide per year because of human disruption of the feedbacks that link peat accumulation and groundwater hydrology. However, no quantitative theory has existed for how patterns of carbon storage and release accompanying growth and subsidence of tropical peatlands are affected by climate and disturbance. Using comprehensive data from a pristine peatland in Brunei Darussalam, we show how rainfall and groundwater flow determine a shape parameter (the Laplacian of the peat surface elevation) that specifies, under a given rainfall regime, the ultimate, stable morphology, and hence carbon storage, of a tropical peatland within a network of rivers or canals. We find that peatlands reach their ultimate shape first at the edges of peat domes where they are bounded by rivers, so that the rate of carbon uptake accompanying their growth is proportional to the area of the still-growing dome interior. We use this model to study how tropical peatland carbon storage and fluxes are controlled by changes in climate, sea level, and drainage networks. We find that fluctuations in net precipitation on timescales from hours to years can reduce long-term peat accumulation. Our mathematical and numerical models can be used to predict long-term effects of changes in temporal rainfall patterns and drainage networks on tropical peatland geomorphology and carbon storage

Genetic drivers of heterogeneity in type 2 diabetes pathophysiology

Type 2 diabetes (T2D) is a heterogeneous disease that develops through diverse pathophysiological processes1,2 and molecular mechanisms that are often specific to cell type3,4. Here, to characterize the genetic contribution to these processes across ancestry groups, we aggregate genome-wide association study data from 2,535,601 individuals (39.7% not of European ancestry), including 428,452 cases of T2D. We identify 1,289 independent association signals at genome-wide significance (P &lt; 5 × 10-8) that map to 611 loci, of which 145 loci are, to our knowledge, previously unreported. We define eight non-overlapping clusters of T2D signals that are characterized by distinct profiles of cardiometabolic trait associations. These clusters are differentially enriched for cell-type-specific regions of open chromatin, including pancreatic islets, adipocytes, endothelial cells and enteroendocrine cells. We build cluster-specific partitioned polygenic scores5 in a further 279,552 individuals of diverse ancestry, including 30,288 cases of T2D, and test their association with T2D-related vascular outcomes. Cluster-specific partitioned polygenic scores are associated with coronary artery disease, peripheral artery disease and end-stage diabetic nephropathy across ancestry groups, highlighting the importance of obesity-related processes in the development of vascular outcomes. Our findings show the value of integrating multi-ancestry genome-wide association study data with single-cell epigenomics to disentangle the aetiological heterogeneity that drives the development and progression of T2D. This might offer a route to optimize global access to genetically informed diabetes care.</p

A Prototype Sensor for In Situ Sensing of Fine Particulate Matter and Volatile Organic Compounds

Air pollution exposure causes seven million deaths per year, according to the World Health Organization. Possessing knowledge of air quality and sources of air pollution is crucial for managing air pollution and providing early warning so that a swift counteractive response can be carried out. An optical prototype sensor (AtmOptic) capable of scattering and absorbance measurements has been developed to target in situ sensing of fine particulate matter (PM2.5) and volatile organic compounds (VOCs). For particulate matter testing, a test chamber was constructed and the emission of PM2.5 from incense burning inside the chamber was measured using the AtmOptic. The weight of PM2.5 particles was collected and measured with a filter to determine their concentration and the sensor signal-to-concentration correlation. The results of the AtmOptic were also compared and found to trend well with the Dylos DC 1100 Pro air quality monitor. The absorbance spectrum of VOCs emitted from various laboratory chemicals and household products as well as a two chemical mixtures were recorded. The quantification was demonstrated, using toluene as an example, by calibrating the AtmOptic with compressed gas standards containing VOCs at different concentrations. The results demonstrated the sensor capabilities in measuring PM2.5 and volatile organic compounds

Reduced methane growth rate explained by decreased Northern Hemisphere microbial sources.

Atmospheric methane (CH(4)) increased through much of the twentieth century, but this trend gradually weakened until a stable state was temporarily reached around the turn of the millennium, after which levels increased once more. The reasons for the slowdown are incompletely understood, with past work identifying changes in fossil fuel, wetland and agricultural sources and hydroxyl (OH) sinks as important causal factors. Here we show that the late-twentieth-century changes in the CH(4) growth rates are best explained by reduced microbial sources in the Northern Hemisphere. Our results, based on synchronous time series of atmospheric CH(4) mixing and (13)C/(12)C ratios and a two-box atmospheric model, indicate that the evolution of the mixing ratio requires no significant change in Southern Hemisphere sources between 1984 and 2005. Observed changes in the interhemispheric difference of (13)C effectively exclude reduced fossil fuel emissions as the primary cause of the slowdown. The (13)C observations are consistent with long-term reductions in agricultural emissions or another microbial source within the Northern Hemisphere. Approximately half (51 ± 18%) of the decrease in Northern Hemisphere CH(4) emissions can be explained by reduced emissions from rice agriculture in Asia over the past three decades associated with increases in fertilizer application and reductions in water use

CO 2 emissions from an undrained tropical peatland: Interacting influences of temperature, shading and water table depth

International audienc

Methane production and transport in a tropical peatland

Wetlands are the largest source of CH4 to the atmosphere, but emissions measurements are highly uncertain, particularly in the tropics. We examine CH4 production and transport in a pristine tropical peatland in Borneo. We use the carbon isotopic (stable and radioactive) composition of dissolved CH4, DIC and DOC within the peat porewater to identify the source and mechanism of CH4 production in tropical peat. First, we measure 14C in all carbon phases to identify the source of CH4. In contrast to the peat, which ages with depth to nearly 3000 cal BP, DOC is modern throughout the peat column, to depths of 4.5m. The 14C content of CH4 and DIC are nearly identical, and are intermediate between the DOC and peat 14C content. Thus, despite the presence of modern carbon throughout the peat profile, peat decomposition is an important source of CH4 production. Next, we use the δ13C of CH4 and DIC to identify the mechanism of CH4 production. Within the peat profile, CH4 and DIC concentrations increase with depth and DIC becomes increasingly enriched in 13C. The δ13C of CH4 is relatively uniform with depth, resulting in a δ13C fractionation between DIC and CH4 of 55-70‰ (αCCO2-CH4 = 1.06-1.07). This fractionation suggests CO2 reduction is the dominant pathway for CH4 production at the site. We find consistent trends with depth across the peatland, attributable to the unique hydrologic behavior of the dome. These trends are similar to those observed in northern peat bogs. Finally, we use information on site hydrology, CH4 and DIC concentrations, isotopic compositions and fluxes to build a model of CH4 production and transport. This model allows us to partition CH4 losses from the peat due to diffusion, tree-mediated transport, and ebullition

An Off-Grid PV Power System for Meteorological and Eddy Covariance Flux Station in Kranji, Singapore

This paper describes an off-grid (stand-alone) PV system for powering an eddy flux station on tropical grassland in Kranji (1°25ʹN, 103°43ʹE), Singapore. Eddy covariance flux systems are used to quantify exchanges of CO₂, H₂O and energy between the atmosphere and land. Our system includes gas analyzers for CO₂ and H₂O, and sensors for rainfall, wind speed, wind direction, long-wave and short-wave radiation, diffuse radiation, and soil heatflux. The off-grid PV system consists of eight 160W p monocrystalline solar panels, sixteen 12V deep cycle batteries, a charge controller, and an inverter. To monitor the performance of our off-grid PV system, we developed a Python program to communicate with the controller and inverter, and record data on a small single-board computer. We applied a Matlab program with meteorological measurements to predict the PV array output. The meteorological measurements and operating data of the PV system are presented and discussed here.Singapore. National Research Foundatio