Abstract
Hyperspectral imaging (HSI) in situ core scanning has emerged as a valuable and novel tool for rapid and non-destructive biogeochemical analysis of lake sediment cores. Variations in sediment composition can be assessed directly from fresh sediment surfaces at ultra-high-resolution (40–300 μm measurement resolution) based on spectral profiles of light reflected from sediments in visible, near infrared, and short-wave infrared wavelengths (400–2500 nm). Here, we review recent methodological developments in this new and growing field of research, as well as applications of this technique for paleoclimate and paleoenvironmental studies. Hyperspectral imaging of sediment cores has been demonstrated to effectively track variations in sedimentary pigments, organic matter, grain size, minerogenic components, and other sedimentary features. These biogeochemical variables record information about past climatic conditions, paleoproductivity, past hypolimnetic anoxia, aeolian input, volcanic eruptions, earthquake and flood frequencies, and other variables of environmental relevance. HSI has been applied to study seasonal and inter-annual environmental variability as recorded in individual varves (annually laminated sediments) or to study sedimentary records covering long glacial–interglacial time-scales (>10,000 years).
Highlights
The scientific investigation of sediment deposited in lakes can provide important and diverse information about past changes in environmental conditions, as well as human impacts to the natural environment, over timescales ranging from the recent past to over 100,000 years [1,2]
We present the development of the technique from visible and near infrared (VNIR) reflectance spectroscopy to Hyperspectral imaging (HSI) core-scanning
In a case study from a lake in central Chile, von Gunten et al [10] calibrated the visible reflectance spectroscopy (VIS-RS) index RABD660;670 directly to meteorological data and found that, in this particular lake, sedimentary chlorophyll was an excellent predictor for warm season temperature with a remarkably small mean prediction error (RMSEP) of 0.24–0.34 °C
Summary
The scientific investigation of sediment deposited in lakes can provide important and diverse information about past changes in environmental conditions, as well as human impacts to the natural environment, over timescales ranging from the recent past to over 100,000 years [1,2]. Hyperspectral imaging (HSI) core scanning is a recently developed technique in which a hyperspectral camera records light spectra reflected directly from the surface of a sediment core. Each pixel within the hyperspectral image contains a spectral reflectance profile that can be used to gain information about the characteristics of the sediment within that pixel [6] Using this approach, physical, mineralogical, and biogeochemical data can be acquired at submillimeter spatial resolution (40–300 μm). An additional advantage of HSI in this field is that spatial information about sediment properties can be obtained This is not possible with other point-based spectroscopy techniques [9,10], and this spatial information is useful for paleoclimate and paleoenvironmental interpretations. We assess the peer-reviewed literature on HSI core scanning of lake sediments and present several key research themes where the application of HSI has led to important insights relevant for paleoenvironmental research
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