scholarly journals Modelling Water Colour Characteristics in an Optically Complex Nearshore Environment in the Baltic Sea; Quantitative Interpretation of the Forel-Ule Scale and Algorithms for the Remote Estimation of Seawater Composition

2020 ◽  
Vol 12 (17) ◽  
pp. 2852
Author(s):  
Sławomir B. Woźniak ◽  
Justyna Meler
Keyword(s):  
Organic Matter ◽  
Simple Model ◽  
Light Absorption ◽  
Pure Water ◽  
Quantitative Interpretation ◽  
Blue Band ◽  
Model Calculations ◽  
Water Colour ◽  
Practical Algorithms ◽  
Inorganic Matter

The paper presents the modelling results of selected characteristics of water-leaving light in an optically complex nearshore marine environment. The modelled quantities include the spectra of the remote-sensing reflectance Rrs(λ) and the hue angle α, which quantitatively describes the colour of water visible to the unaided human eye. Based on the latter value, it is also possible to match water-leaving light spectra to classes on the traditional Forel-Ule water colour scale. We applied a simple model that assumes that seawater is made up of chemically pure water and three types of additional optically significant components: particulate organic matter (POM) (which includes living phytoplankton), particulate inorganic matter (PIM), and chromophoric dissolved organic matter (CDOM). We also utilised the specific inherent optical properties (SIOPs) of these components, determined from measurements made at a nearshore location on the Gulf of Gdańsk. To a first approximation, the simple model assumes that the Rrs spectrum can be described by a simple function of the ratio of the light backscattering coefficient to the sum of the light absorption and backscattering coefficients (u = bb/(a + bb)). The model calculations illustrate the complexity of possible relationships between the seawater composition and the optical characteristics of an environment in which the concentrations of individual optically significant components may be mutually uncorrelated. The calculations permit a quantitative interpretation of the Forel-Ule scale. The following parameters were determined for the several classes on this scale: typical spectral shapes of the u ratio, possible ranges of the total light absorption coefficient in the blue band (a(440)), as well as upper limits for concentrations of total and organic and inorganic fractions of suspended particles (SPM, POM and PIM concentrations). The paper gives examples of practical algorithms that, based on a given Rrs spectrum or some of its features, and using lookup tables containing the modelling results, enable to estimate the approximate composition of seawater.

Photodegradation of nitrite in lake waters: role of dissolved organic matter

2009 ◽  
Vol 6 (5) ◽  
pp. 407 ◽  
Author(s):  
Davide Vione ◽  
Marco Minella ◽  
Claudio Minero ◽  
Valter Maurino ◽  
Paolo Picco ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Hydroxyl Radical ◽  
Lake Water ◽  
Pure Water ◽  
Mixing Layer ◽  
Life Time ◽  
Model Calculations ◽  
Lake Waters

Environmental context. Nitrite is an important nutrient in surface waters, a key intermediate in the interconversion of nitrate into ammonium, and a considerable photochemical source of reactive species such as the hydroxyl radical. We have found that scavengers of hydroxyl radicals such as dissolved organic matter, which are usually supposed to inhibit the photodegradation of dissolved compounds, are able on the contrary to enhance the phototransformation of nitrite. The three weeks’ lifetime of nitrite in the surface layer of lakes, derived from the results of the present work, would make photochemistry an important issue in determining the concentration of nitrite in lake water. Abstract. Here we studied the degradation rate of nitrite (NO2–), added to lake water at sub-micromolar levels, upon ultraviolet (UV) irradiation. NO2– photodegradation was considerably faster in lake water compared with ultra-pure water. A key issue was the presence in lake water of hydroxyl radical (•OH) scavengers that inhibited the reaction between NO2– and •OH. Such a reaction, while causing additional NO2– transformation, produced nitrogen dioxide (NO2•) that was subsequently involved into the regeneration of NO2– by dimerisation or the reaction with nitric oxide (NO•). The scavenging of •OH by compounds different from NO2– (mainly dissolved organic matter, DOM) prevented the regeneration reactions from taking place, and enhanced the phototransformation of NO2–. Model calculations for the direct photolysis of NO2–, applied to the lake water samples, yielded a NO2– half-life time of around three weeks in the mixing layer of the lakes because of photodegradation. Therefore, we conclude that photodegradation is a potentially important process to control the concentration of NO2– in shallow lakes, or in deeper ones under stratification conditions.

Elements for a General Organology

Derrida Today ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 72-94
Author(s):  
Bernard Stiegler
Keyword(s):  
Organic Matter ◽  
Planetary Scale ◽  
General Account ◽  
Inorganic Matter ◽  
History Of

These lectures outline the project of a general organology, which is to say an account of life when it is no longer just biological but technical, or when it involves not just organic matter but organized inorganic matter. This organology is also shown to require a modified Simondonian account of the shift from vital individuation to a three-stranded process of psychic, collective and technical individuation. Furthermore, such an approach involves extending the Derridean reading of Socrates's discussion of writing as a pharmakon, so that it becomes a more general account of the pharmacological character of retention and protention. By going back to Leroi-Gourhan, we can recognize that this also means pursuing the history of retentional modifications unfolding in the course of the history of what, with Lotka, can also be called exosomatization. It is thus a question of how exteriorization can, today, in an epoch when it becomes digital, and in an epoch that produces vast amounts of entropy at the thermodynamic, biological and noetic levels, still possibly produce new forms of interiorization, that is, new forms of thought, care and desire, amounting to so many chances to struggle against the planetary-scale pharmacological crisis with which we are currently afflicted.

scholarly journals Contributions of Organic and Mineral Matter to Vertical Accretion in Tidal Wetlands across a Chesapeake Bay Subestuary

2021 ◽  
Vol 9 (7) ◽  
pp. 751
Author(s):  
Jenny R. Allen ◽  
Jeffrey C. Cornwell ◽  
Andrew H. Baldwin
Keyword(s):  
Organic Matter ◽  
Sea Level Rise ◽  
Chesapeake Bay ◽  
Sea Level ◽  
210Pb Dating ◽  
Sediment Supply ◽  
Mineral Matter ◽  
Tidal Wetlands ◽  
Vertical Accretion ◽  
Inorganic Matter

Persistence of tidal wetlands under conditions of sea level rise depends on vertical accretion of organic and inorganic matter, which vary in their relative abundance across estuarine gradients. We examined the relative contribution of organic and inorganic matter to vertical soil accretion using lead-210 (210Pb) dating of soil cores collected in tidal wetlands spanning a tidal freshwater to brackish gradient across a Chesapeake Bay subestuary. Only 8 out of the 15 subsites had accretion rates higher than relative sea level rise for the area, with the lowest rates of accretion found in oligohaline marshes in the middle of the subestuary. The mass accumulation of organic and inorganic matter was similar and related (R2 = 0.37). However, owing to its lower density, organic matter contributed 1.5–3 times more toward vertical accretion than inorganic matter. Furthermore, water/porespace associated with organic matter accounted for 82%–94% of the total vertical accretion. These findings demonstrate the key role of organic matter in the persistence of coastal wetlands with low mineral sediment supply, particularly mid-estuary oligohaline marshes.

scholarly journals Reaction-Path Formulation of a Simple Dissolution Model for Radiocarbon Dating Groundwater

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 646-653 ◽  
Author(s):  
Songlin Cheng
Keyword(s):  
Organic Matter ◽  
Simple Model ◽  
Closed System ◽  
Redox Reactions ◽  
Radiocarbon Dating ◽  
Reaction Path ◽  
Dilution Effect ◽  
Carbonate Minerals ◽  
Dissolution Model ◽  
Hydrogeological Studies

Since the pioneer publication of K. O. Münnich (1957), 14C systematics have been used in many hydrogeological studies. Because of the complexity of carbon geochemistry, numerous models have been proposed to correct the dilution effect of “dead” carbon in groundwater. All the 14C correction models for dating groundwater are based on either open- or closed-system conditions. I present here a simple model that accounts for the effects of both open- and closed-system dissolution of carbonate and aluminosilicate minerals. For systems involving precipitation of carbonate minerals and redox reactions of organic matter, reaction-path simulations are essential for reliable 14C dating of groundwater.

scholarly journals The Paths of the Suspended Particulate Inorganic and Organic Matter in a Small Urban Estuary: The Aarhus Harbour Estuary

1986 ◽  
Vol 17 (1) ◽  
pp. 31-46 ◽  
Author(s):  
K. B. Kronvang ◽  
C. Christiansen
Keyword(s):  
Organic Matter ◽  
Particulate Matter ◽  
Organic Content ◽  
Temporal And Spatial Distribution ◽  
Urban Estuary ◽  
Inorganic Matter ◽  
Organic Sediment ◽  
Suspended Particulate ◽  
Good Agreement ◽  
Inorganic And Organic

The nverine supply of suspended inorganic and organic sediment, its temporal and spatial distribution and its exchange with the bay, were estimated for an urban estuary (Aarhus Harbour Estuary, Denmark) during 1983-84. The river supplies high levels of particulate matter to the estuary. Export from the estuary averages one fifth of the river introduced particulate matter resulting in the accumulation of terrigenous material in the estuary. River discharge determines whether the high depletion of particulate matter in the upper estuary follows an exponential(flocculation) or a lineary curve (dilution). Preferential deposition of organic as opposed to inorganic matter in the upper estuary depletes the particulate matter of organic matter and associated pollutants. The estuary is divided into three depositional zones identified on the basis of sediment activity, grain-size and organic content. A sediment budget is precented for the estuary. Good agreement is shown between the actually dredged sediment quantity and the mass to sedimentation from the budget.

scholarly journals Dye-sensitised Photocatalyst for Photocatalytic Whole Water Splitting to Produce Hydrogen in a Twin Photoreactor

2021 ◽  
Vol 17 (2) ◽  
pp. 47-72
Author(s):  
Yi-Shan Huang ◽  
◽  
Chao-Wei Huang ◽  
Van-Huy Nguyen ◽  
Yen-Han Wang ◽  
...  
Keyword(s):  
Water Splitting ◽  
Light Absorption ◽  
Physical Adsorption ◽  
Pure Water ◽  
Absorption Capacity ◽  
Organic Dye ◽  
Coupling Agents ◽  
Silane Coupling Agents ◽  
Silane Coupling ◽  
Electron Mediators

Organic dye-sensitised SrTiO3:Rh and WO3 were served as H2 catalysts and O2 catalysts in a Z-scheme system to conduct photocatalytic pure water splitting. To enhance the light absorption capacity, the composites of organic dye (N3, N719, Z907, black dye, C101, and K19) and SrTiO3:Rh were synthesised via physical adsorption and then verified by the performance of photocatalytic hydrogen evolution. Among these dyes, N3-SrTiO3:Rh revealed visible light absorption and exhibited the best photocatalytic activity. Therefore, N3 dye was adopted, and silane coupling agents were used to form chemical bonding with SrTiO3:Rh. Furthermore, the photocatalytic pure water splitting of N3-SrTiO3:Rh was investigated in a single reactor, and a twin photoreactor with Fe2+ and Fe3+ ions served as the electron mediators, respectively. The highest quantum efficiency can reach 0.0259% in a twin reactor when compared with the single reactor (0.0052%) because of the improvement in the light absorption from N3 and inhibition of the backward reaction of water splitting. Consequently, organic dye-sensitised photocatalysts are highly effective and eco-friendly in conducting photocatalytic pure water splitting.

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