86 research outputs found

    Variability of particulate organic carbon in inland waters observed from MODIS Aqua imagery

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    LETTER • THE FOLLOWING ARTICLE IS OPEN ACCESS Variability of particulate organic carbon in inland waters observed from MODIS Aqua imagery Hongtao Duan1, Lian Feng2, Ronghua Ma1, Yuchao Zhang1 and Steven Arthur Loiselle3 Published 19 August 2014 • © 2014 IOP Publishing Ltd Environmental Research Letters, Volume 9, Number 8 Article PDF Figures References Citations PDF 2919 Total downloads Cited by 6 articles Article has an altmetric score of 1 Turn on MathJax Share this article Article information Abstract Surface concentrations of particulate organic carbon (POC) in shallow inland lakes were estimated using MODIS Aqua data. A power regression model of the direct empirical relationship between POC and the atmospherically Rayleigh-corrected MODIS product (Rrc,645-Rrc,1240)/(Rrc,859-Rrc,1240) was developed (R2 = 0.72, RMSE = 35.86 μgL−1, p < 0.0001, N = 47) and validated (RMSE = 44.46 μgL−1, N = 16) with field data from 56 lakes in the Middle and Lower reaches of the Yangtze River, China. This algorithm was applied to an 11 year series of MODIS data to determine the spatial and temporal distribution of POC in a wide range of lakes with different trophic and optical properties. The results indicate that there is a general increase in minimum POC concentrations in lakes from middle to lower reaches of the Yangtze River. The temporal dynamics of springtime POC in smaller lakes were found to be influenced by local meteorological conditions, in particular precipitation and wind speed, while larger lakes were found to be more sensitive to air temperature

    Community monitoring of coliform pollution in Lake Tanganyika

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    Conventional water quality monitoring has been done for decades in Lake Tanganyika, under different national and international programs. However, these projects utilized monitoring approaches, which were temporally limited, labour intensive and costly. This study examines the use of citizen science to monitor the dynamics of coliform concentrations in Lake Tanganyika as a complementary method to statutory and project-focused measurements. Persons in five coastal communities (Kibirizi, Ilagala, Karago, Ujiji and Gombe) were trained and monitored total coliforms, faecal coliforms and turbidity for one year on a monthly basis, in parallel with professional scientists. A standardized and calibrated Secchi tube was used at the same time to determine turbidity. Results indicate that total and faecal coliform concentrations determined by citizen scientists correlated well to those determined by professional scientists. Furthermore, citizen scientist-based turbidity values were shown to provide a potential indicator for high FC and TC concentrations. As a simple tiered approach to identify increased coliform loads, trained local citizen scientists could use low-cost turbidity measurements with follow up sampling and analysis for coliforms, to inform their communities and regulatory bodies of high risk conditions, as well as to validate local mitigation actions. By comparing the spatial and temporal dynamics of coliform concentrations to local conditions of infrastructure, population, precipitation and hydrology in the 15 sites (3 sites per community) over 12 months, potential drivers of coliform pollution in these communities were identified, largely related to precipitation dynamics and the land use

    CDOM, oxygen and bacterial abundance in the SML and ULW of a marine monocolture in the presence and absence of polystyrene microparticles

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    These data accompany the perspective paper "Plastic Accumulation in the Sea Surface Microlayer: An Experiment-Based Perspective for Future Studies" authored by L. Galgani and S. A. Loiselle. The data reflect the results obtained from a small pilot laboratory experiment used to support the hypothesis that plastic accumulation in the sea surface microlayer (SML) might have effects on organic matter cycling in the surface ocean. Bacterial abundance, chromophoric dissolved organic matter (CDOM), and oxygen concentrations were measured

    Functioning and dynamics of wetland vegetation of Lake Victoria: an overview

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    he aquatic macrophytic vegetation constituting the wetlands situated along the coast of Lake Victoria provides valuable services to both local and regional communities as well as an important ecological function through the transition between terrestrial and aquatic ecosystems. The wetland vegetation is typically rooted in the substrate on the landward side of the lake, but forms a floating mat towards the middle of the wetland and at the wetland/lake interface. Cyperus papyrus and Miscanthidium violaceum vegetation typically dominate the permanently inundated wetland areas along most of the shores of Lake Victoria. Due to the prevailing climatic and hydrological catchment conditions, these macrophytic plants (papyrus in particular) tend to exhibit high net productivity and nutrient uptake which strongly influences both wetland status and lake water quality. In addition, these wetlands provide important economic livelihoods for the local populations. The integrity and physical structure of these wetlands strongly influences their associated mass transport mechanisms (water, nutrients and carbon) and ecosystem processes. Wetland degradation in Africa is an increasing problem, as these ecosystems are relied upon to attenuate industrial, urban and agricultural pollution and supply numerous services and resources. In an integrated project focused on the wetlands of Lake Victoria, the ecological and economic aspects of littoral wetlands were examined and new instruments developed for their sustainable management

    Selective Mechanochemical Dehalogenation of Chlorobenzenes over Calcium Hydride

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    We have shown that in the presence of a reactive substrate, chlorinated organic compounds can be dehalogenated by mechanical treatment, and a specific reaction product can be obtained. We have used a ball milling process at low temperature and atmospheric pressure to produce a dechlorination of up to 100% for both liquid and solid chlorinated compounds. The products of the completed reaction for trials with hexachlorobenzene and chlorobenzene were both principally restricted to benzene and chloride salts. The use of CaH2 as a source of active hydrogen produces a much more specific reaction in significantly less time in comparison with CaO and MgO substrates reacted under hydrogen atmosphere. The process was found to depend on the injected mechanical energy and the collision frequency. In the case of hexachlorobenzene, an explosive-type reaction was observed to occur at specific milling times as a function of the kinetic energy employed

    The Assessment of Landsat-8 OLI Atmospheric Correction Algorithms for Inland Waters

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    The OLI (Operational Land Imager) sensor on Landsat-8 has the potential to meet the requirements of remote sensing of water color. However, the optical properties of inland waters are more complex than those of oceanic waters, and inland atmospheric correction presents additional challenges. We examined the performance of atmospheric correction (AC) methods for remote sensing over three highly turbid or hypereutrophic inland waters in China: Lake Hongze, Lake Chaohu, and Lake Taihu. Four water-AC algorithms (SWIR (Short Wave Infrared), EXP (Exponential Extrapolation), DSF (Dark Spectrum Fitting), and MUMM (Management Unit Mathematics Models)) and three land-AC algorithms (FLAASH (Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes), 6SV (a version of Second Simulation of the Satellite Signal in the Solar Spectrum), and QUAC (Quick Atmospheric Correction)) were assessed using Landsat-8 OLI data and concurrent in situ data. The results showed that the EXP (and DSF) together with 6SV algorithms provided the best estimates of the remote sensing reflectance (Rrs) and band ratios in water-AC algorithms and land-AC algorithms, respectively. AC algorithms showed a discriminating accuracy for different water types (turbid waters, in-water algae waters, and floating bloom waters). For turbid waters, EXP gave the best Rrs in visible bands. For the in-water algae and floating bloom waters, however, all water-algorithms failed due to an inappropriate aerosol model and non-zero reflectance at 1609 nm. The results of the study show the improvements that can be achieved considering SWIR bands and using band ratios, and the need for further development of AC algorithms for complex aquatic and atmospheric conditions, typical of inland waters
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