Leveraging Thousands of Contrail Observations from GLOBE Citizen Scientists

The GLOBE (Global Learning and Observations to Benefit the Environment) Program is NASA's largest and longest-operating citizen science program contributing Earth observations. Over 800,000 cloud observations have been reported worldwide since YEAR that include reports of short-lived, persistent, and persistent-spreading contrails. While contrails can be challenging to observe with space-borne platforms, humans are adept at spotting contrails from the ground. The NASA GLOBE Clouds team at NASA Langley Research Center in Hampton, Virginia matches cloud observations to multiple satellite platforms for comparison, including: NASA's CERES (Clouds and Earth's Radiant Energy System) instrument onboard Terra and Aqua, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation), and geostationary satellites. A pilot project was started with select students in the United States to track airplanes above 25,000 ft and report airplane type, altitude, and report if a contrail was being or was not being produced. The objective of the pilot project was to establish if this is a scalable approach for building an international observational dataset documenting what types of airplanes are creating what types of contrails (short-lived, persistent, spreading) under what atmospheric conditions. Preliminary results of this pilot project will be presented

Legacy Impacts of All-Time Anthropogenic Emissions on the Global Mercury Cycle

Elevated mercury (Hg) in marine and terrestrial ecosystems is a global health concern because of the formation of toxic methylmercury. Humans have emitted Hg to the atmosphere for millennia, and this Hg has deposited and accumulated into ecosystems globally. Here we present a global biogeochemical model with fully coupled atmospheric, terrestrial, and oceanic Hg reservoirs to better understand human influence on Hg cycling and timescales for responses. We drive the model with a historical inventory of anthropogenic emissions from 2000 BC to present. Results show that anthropogenic perturbations introduced to surface reservoirs (atmosphere, ocean, or terrestrial) accumulate and persist in the subsurface ocean for decades to centuries. The simulated present-day atmosphere is enriched by a factor of 2.6 relative to 1840 levels, consistent with sediment archives, and by a factor of 7.5 relative to natural levels (2000 BC). Legacy anthropogenic Hg re-emitted from surface reservoirs accounts for 60% of present-day atmospheric deposition, compared to 27% from primary anthropogenic emissions, and 13% from natural sources. We find that only 17% of the present-day Hg in the surface ocean is natural and that half of its anthropogenic enrichment originates from pre-1950 emissions. Although Asia is presently the dominant contributor to primary anthropogenic emissions, only 17% of the surface ocean reservoir is of Asian anthropogenic origin, as compared to 30% of North American and European origin. The accumulated burden of legacy anthropogenic Hg means that future deposition will increase even if primary anthropogenic emissions are held constant. Aggressive global Hg emission reductions will be necessary just to maintain oceanic Hg concentrations at present levels.Engineering and Applied Science

Modelling the mercury stable isotope distribution of Earth surface reservoirs: Implications for global Hg cycling

Mercury (Hg) stable isotopes are useful to understand Hg biogeochemical cycling because physical, chemical and biological processes cause characteristic Hg isotope mass-dependent (MDF) and mass-independent (MIF) fractionation. Here, source Hg isotope signatures and process-based isotope fractionation factors are integrated into a fully coupled, global atmospheric-terrestrial-oceanic box model of MDF (delta Hg-202), odd-MIF (Delta Hg-199) and even-MIF (Delta Hg-200). Using this bottom-up approach, we find that the simulated Hg isotope compositions are inconsistent with the observations. We then fit the Hg isotope enrichment factors for MDF, odd-MIF and even-MIF to observational Hg isotope constraints. The MDF model suggests that atmospheric Hg-0 photo-oxidation should enrich heavy Hg isotopes in the reactant Hg-0, in contrast to the experimental observations of Hg-0 photo-oxidation by Br. The fitted enrichment factor of terrestrial Hg-0 emission in the odd-MIF model (5 parts per thousand) is likely biased high, suggesting that the terrestrial Hg-0 emission flux (160 Mg yr(-1)) used in our standard model is underestimated. In the even-MIF model, we find that a small positive atmospheric Hg-0 photo-oxidation enrichment factor (0.22 parts per thousand) along with enhanced atmospheric Hg-II photo-reduction and atmospheric Hg-0 dry deposition (foliar uptake) fluxes to the terrestrial reservoir are needed to match Delta Hg-200 observations. Marine Hg isotope measurements are needed to further expand the use of Hg isotopes in understanding global Hg cycling. (C) 2018 Elsevier Ltd. All rights reserved

Toward an assessment of the global inventory of present-day mercury releases to freshwater environments

Aquatic ecosystems are an essential component of the biogeochemical cycle of mercury (Hg), as inorganic Hg can be converted to toxic methylmercury (MeHg) in these environments and reemissions of elemental Hg rival anthropogenic Hg releases on a global scale. Quantification of effluent Hg releases to aquatic systems globally has focused on discharges to the global oceans, rather than contributions to freshwater systems that affect local exposures and risks associated with MeHg. Here we produce a first-estimate of sector-specific, spatially resolved global aquatic Hg discharges to freshwater systems. We compare our release estimates to atmospheric sources that have been quantified elsewhere. By analyzing available quantitative and qualitative information, we estimate that present-day global Hg releases to freshwater environments (rivers and lakes) associated with anthropogenic activities have a lower bound of ~1000 Mg· a−1. Artisanal and small-scale gold mining (ASGM) represents the single largest source, followed by disposal of mercury-containing products and domestic waste water, metal production, and releases from industrial installations such as chlor-alkali plants and oil refineries. In addition to these direct anthropogenic inputs, diffuse inputs from land management activities and remobilization of Hg previously accumulated in terrestrial ecosystems are likely comparable in magnitude. Aquatic discharges of Hg are greatly understudied and further constraining associated data gaps is crucial for reducing the uncertainties in the global biogeochemical Hg budget

Historical Mercury Releases from Commercial Products: Global Environmental Implications

The intentional use of mercury (Hg) in products and processes (“commercial Hg”) has contributed a large and previously unquantified anthropogenic source of Hg to the global environment over the industrial era, with major implications for Hg accumulation in environmental reservoirs. We present a global inventory of commercial Hg uses and releases to the atmosphere, water, soil, and landfills from 1850 to 2010. Previous inventories of anthropogenic Hg releases have focused almost exclusively on atmospheric emissions from “byproduct” sectors (e.g., fossil fuel combustion). Cumulative anthropogenic atmospheric Hg emissions since 1850 have recently been estimated at 215 Gg (only including commercial Hg releases from chlor-alkali production, waste incineration, and mining). We find that other commercial Hg uses and nonatmospheric releases from chlor-alkali and mining result in an additional 540 Gg of Hg released to the global environment since 1850 (air: 20%; water: 30%; soil: 30%; landfills: 20%). Some of this release has been sequestered in landfills and benthic sediments, but 310 Gg actively cycles among geochemical reservoirs and contributes to elevated present-day environmental Hg concentrations. Commercial Hg use peaked in 1970 and has declined sharply since. We use our inventory of historical environmental releases to force a global biogeochemical model that includes new estimates of the global burial in ocean margin sediments. Accounting for commercial Hg releases improves model consistency with observed atmospheric concentrations and associated historical trends.Engineering and Applied Science

Liver toxicity of Crude extract of Ficus natalensis traditionally used in South Western Uganda

Background: Traditional healers have used medicinal plants to treat infectious diseases since time immemorial. These natural products have not only played a vital role in healing, but have also contributed to the discovery of many pharmaceutically active agents. Objectives: This research was aimed at assessing the effects of crude extract of Ficus natalensis on the liver. Methodology: Test and control Wistar albino rats were fed on either Water or Ethanolic extract of Ficus natalensis and water-only (control) respectively and their serum harvested. Biochemical analysis of liver function tests was performed and Human Diagnostic Test Kits were used to assay for the enzymes ALT (alanine aminotransferase), (AST (serum aspartate aminotransferase) and γ-GT (gamma glutamyl transpeptidase).The organ body weight ratio was also recorded. Results: The cold water decoction once administered to the rats showed adverse effects leading to death of the experimental animals by day 3. The ethanolic extract results showed that there was a dose-dependent alteration in the indices of liver function as well as enlargement of the liver following feeding on the ethanolic extract of Ficus natalensis. All the serum enzyme activity of ALT, AST and GGT were increased in a dose-dependent manner and the groups of animals being fed on the ethanolic extract, showed a reduction in weight. Discussion: The cold water extraction might have extracted all the active ingredients including some that were toxic to the laboratory animals leading to their death. The ethanolic extracts exhibited alterations in the indices of liver function as well as enlargement of the liver in a dose-specific manner. All the serum enzyme activity of ALT, AST and GGT was increased in a dose-dependent manner. This could possibly be due to hepatotoxicity resulting from the metabolites of the Ficus natalensis. Key words: Ficus natalensis, Ethanolic extract, Liver toxicit

Gas-Particle Partitioning of Atmospheric Hg(II) and Its Effect on Global Mercury Deposition

Atmospheric deposition of Hg(II) represents a major input of mercury to surface environments. The phase of Hg(II) (gas or particle) has important implications for deposition. We use long-term observations of reactive gaseous mercury (RGM, the gaseous component of Hg(II)), particle-bound mercury (PBM, the particulate component of Hg(II)), fine particulate matter (PM2.5), and temperature (T) at five sites in North America to derive an empirical gas-particle partitioning relationship log10(K−1) = (10±1)–(2500±300)/T where K = (PBM/PM2.5)/RGM with PBM and RGM in common mixing ratio units, PM2.5 in μg m−3, and T in K. This relationship is within the range of previous work but is based on far more extensive data from multiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II) between the gas and particle phases. The resulting gas-phase fraction of Hg(II) ranges from over 90 % in warm air with little aerosol to less than 10 % in cold air with high aerosol. Hg deposition to high latitudes increases because of more efficient scavenging of particulate Hg(II) by precipitating snow. Model comparison to Hg observations at the North American surface sites suggests that subsidence from the free troposphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associated with high aerosol loads. Simulation of RGM and PBM at these sites is improved by including fast in-plume reduction of Hg(II) emitted from coal combustion and by assuming that anthropogenic particulate Hg(p) behaves as semi-volatile Hg(II) rather than as a refractory particulate component. We improve the simulation of Hg wet deposition fluxes in the US relative to a previous version of GEOS-Chem; this largely reflects independent improvement of the washout algorithm. The observed wintertime minimum in wet deposition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).Earth and Planetary SciencesEngineering and Applied Science