scholarly journals Anthropogenic Influences on Dissolved Organic Matter in Three Coastal Bays, North China

2021 ◽  
Vol 9 ◽  
Author(s):  
Penghui Li ◽  
Chen Zhao ◽  
Ke Liu ◽  
Xiaotong Xiao ◽  
Yujue Wang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Dissolved Organic Matter ◽  
Bottom Water ◽  
North China ◽  
Jiaozhou Bay ◽  
Stable Carbon Isotope ◽  
River Mouth ◽  
Biological Production ◽  
Coastal Bays

Coastal bays bear anthropogenic influence strongly, and thus dissolved organic matter (DOM) in coastal bays, which is an important component of global carbon cycling, could be heavily affected by anthropogenic inputs. Utilizing absorbance, fluorescence spectroscopy, and stable carbon isotope (δ13C), this study analyzed the characteristics and distribution of DOM in three coastal bays (Jiaozhou Bay, Sishili Bay, and Taozi Bay), located in North China. The results showed that there was always a high concentration of DOM near the river mouth in all three bays and the DOM concentration decreased along the salinity gradient in Jiaozhou Bay, indicating the riverine inputs are the main factor that causes the variation of DOM in these coastal bays. The effects of inflowing rivers on DOM in coastal bays differed with their watershed characteristics (i.e., agricultural/urban). In addition, humic-like DOM components were found to be positively correlated with the apparent oxygen utilization, suggesting microbial activities could contribute to the DOM in this region. There was generally a higher averaged concentration of fluorescent DOM in surface water than that in bottom water in Jiaozhou Bay. In contrast, higher humic-like DOM was found in bottom water than that in surface water in Sishili Bay and Taozi Bay, which could be attributed to aquaculture activities and biological production. Moreover, photodegradation/photobleaching, dumping, and sewage discharge had their effects on DOM in coastal bays. This study demonstrates that DOM in coastal bays is regulated by multiple sources (rivers, aquaculture, dumping, and sewage) and processes (biological production and photodegradation), and anthropogenic activities have their influences on optical and isotopic characteristics of DOM in coastal bays.

scholarly journals Factors regulating the compositions and distributions of dissolved organic matter in the estuaries of Jiaozhou Bay in North China

Oceanologia ◽  
2020 ◽  
Vol 62 (1) ◽  
pp. 101-110
Author(s):  
Jiaojie Hu ◽  
Li Zou ◽  
Jian Wang ◽  
Qianqian Ren ◽  
Bin Xia ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
North China ◽  
Jiaozhou Bay

Removal of the Neutral Dissolved Organic Matter (NDOM) from Surface Water by Coagulation/Flocculation and Nanofiltration

2021 ◽  
pp. 1-14
Author(s):  
Sami Khettaf ◽  
Roumaissa Boumaraf ◽  
Fatiha Benmahdi ◽  
Kamel-Eddine Bouhidel ◽  
Mohammed Bouhelassa
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Dissolved Organic Matter

scholarly journals Colored dissolved organic matter in shallow estuaries: relationships between carbon sources and light attenuation

2016 ◽  
Vol 13 (2) ◽  
pp. 583-595 ◽  
Author(s):  
W. K. Oestreich ◽  
N. K. Ganju ◽  
J. W. Pohlman ◽  
S. E. Suttles
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Carbon Isotope ◽  
Light Attenuation ◽  
Stable Carbon Isotope ◽  
Colored Dissolved Organic Matter ◽  
Barnegat Bay ◽  
Absorption Ratio ◽  
Chincoteague Bay ◽  
Shallow Estuaries

Abstract. Light availability is of primary importance to the ecological function of shallow estuaries. For example, benthic primary production by submerged aquatic vegetation is contingent upon light penetration to the seabed. A major component that attenuates light in estuaries is colored dissolved organic matter (CDOM). CDOM is often measured via a proxy, fluorescing dissolved organic matter (fDOM), due to the ease of in situ fDOM sensor measurements. Fluorescence must be converted to CDOM absorbance for use in light attenuation calculations. However, this CDOM–fDOM relationship varies among and within estuaries. We quantified the variability in this relationship within three estuaries along the mid-Atlantic margin of the eastern United States: West Falmouth Harbor (MA), Barnegat Bay (NJ), and Chincoteague Bay (MD/VA). Land use surrounding these estuaries ranges from urban to developed, with varying sources of nutrients and organic matter. Measurements of fDOM (excitation and emission wavelengths of 365 nm (±5 nm) and 460 nm (±40 nm), respectively) and CDOM absorbance were taken along a terrestrial-to-marine gradient in all three estuaries. The ratio of the absorption coefficient at 340 nm (m−1) to fDOM (QSU) was higher in West Falmouth Harbor (1.22) than in Barnegat Bay (0.22) and Chincoteague Bay (0.17). The CDOM : fDOM absorption ratio was variable between sites within West Falmouth Harbor and Barnegat Bay, but consistent between sites within Chincoteague Bay. Stable carbon isotope analysis for constraining the source of dissolved organic matter (DOM) in West Falmouth Harbor and Barnegat Bay yielded δ13C values ranging from −19.7 to −26.1 ‰ and −20.8 to −26.7 ‰, respectively. Concentration and stable carbon isotope mixing models of DOC (dissolved organic carbon) indicate a contribution of 13C-enriched DOC in the estuaries. The most likely source of 13C-enriched DOC for the systems we investigated is Spartina cordgrass. Comparison of DOC source to CDOM : fDOM absorption ratios at each site demonstrates the relationship between source and optical properties. Samples with 13C-enriched carbon isotope values, indicating a greater contribution from marsh organic material, had higher CDOM : fDOM absorption ratios than samples with greater contribution from terrestrial organic material. Applying a uniform CDOM : fDOM absorption ratio and spectral slope within a given estuary yields errors in modeled light attenuation ranging from 11 to 33 % depending on estuary. The application of a uniform absorption ratio across all estuaries doubles this error. This study demonstrates that light attenuation coefficients for CDOM based on continuous fDOM records are highly dependent on the source of DOM present in the estuary. Thus, light attenuation models for estuaries would be improved by quantification of CDOM absorption and DOM source identification.

scholarly journals Photomineralization and photomethanification of dissolved organic matter in Saguenay River surface water

2015 ◽  
Vol 12 (22) ◽  
pp. 6823-6836 ◽  
Author(s):  
Y. Zhang ◽  
H. Xie
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Dissolved Organic Matter ◽  
Dimethyl Sulfide ◽  
Ultraviolet B ◽  
Global Ocean ◽  
Quantum Yields ◽  
Methyl Radical ◽  
Ch4 Production ◽  
Saguenay River

Abstract. Rates and apparent quantum yields of photomineralization (AQYDOC) and photomethanification (AQYCH4) of chromophoric dissolved organic matter (CDOM) in Saguenay River surface water were determined at three widely differing dissolved oxygen concentrations ([O2]) (suboxic, air saturation, and oxygenated) using simulated-solar radiation. Photomineralization increased linearly with CDOM absorbance photobleaching for all three O2 treatments. Whereas the rate of photochemical dissolved organic carbon (DOC) loss increased with increasing [O2], the ratio of fractional DOC loss to fractional absorbance loss showed an inverse trend. CDOM photodegradation led to a higher degree of mineralization under suboxic conditions than under oxic conditions. AQYDOC determined under oxygenated, suboxic, and air-saturated conditions increased, decreased, and remained largely constant with photobleaching, respectively; AQYDOC obtained under air saturation with short-term irradiations could thus be applied to longer exposures. AQYDOC decreased successively from ultraviolet B (UVB) to ultraviolet A (UVA) to visible (VIS), which, alongside the solar irradiance spectrum, points to VIS and UVA being the primary drivers for photomineralization in the water column. The photomineralization rate in the Saguenay River was estimated to be 2.31 × 108 mol C yr−1, accounting for only 1 % of the annual DOC input into this system. Photoproduction of CH4 occurred under both suboxic and oxic conditions and increased with decreasing [O2], with the rate under suboxic conditions ~ 7–8 times that under oxic conditions. Photoproduction of CH4 under oxic conditions increased linearly with photomineralization and photobleaching. Under air saturation, 0.00057 % of the photochemical DOC loss was diverted to CH4, giving a photochemical CH4 production rate of 4.36 × 10−6 mol m−2 yr−1 in the Saguenay River and, by extrapolation, of (1.9–8.1) × 108 mol yr−1 in the global ocean. AQYCH4 changed little with photobleaching under air saturation but increased exponentially under suboxic conditions. Spectrally, AQYCH4 decreased sequentially from UVB to UVA to VIS, with UVB being more efficient under suboxic conditions than under oxic conditions. On a depth-integrated basis, VIS prevailed over UVB in controlling CH4 photoproduction under air saturation while the opposite held true under O2-deficiency. An addition of micromolar levels of dissolved dimethyl sulfide (DMS) substantially increased CH4 photoproduction, particularly under O2-deficiency; DMS at nanomolar ambient concentrations in surface oceans is, however, unlikely a significant CH4 precursor. Results from this study suggest that CDOM-based CH4 photoproduction only marginally contributes to the CH4 supersaturation in modern surface oceans and to both the modern and Archean atmospheric CH4 budgets, but that the photochemical term can be comparable to microbial CH4 oxidation in modern oxic oceans. Our results also suggest that anoxic microniches in particulate organic matter and phytoplankton cells containing elevated concentrations of precursors of the methyl radical such as DMS may provide potential hotspots for CH4 photoproduction.

scholarly journals Surface water treatment by UV/H2O2 with subsequent soil aquifer treatment: impact on micropollutants, dissolved organic matter and biological activity

2019 ◽  
Vol 5 (10) ◽  
pp. 1709-1722 ◽  
Author(s):  
Robin Wünsch ◽  
Julia Plattner ◽  
David Cayon ◽  
Fabienne Eugster ◽  
Jens Gebhardt ◽  
...  
Keyword(s):  
Organic Matter ◽  
Biological Activity ◽  
Water Treatment ◽  
Surface Water ◽  
Dissolved Organic Matter ◽  
Microbial Activity ◽  
Soil Aquifer Treatment ◽  
Organic Micropollutants ◽  
Total Removal ◽  
Surface Water Treatment

UV/H2O2 treatment of sand-filtered surface water before soil aquifer treatment increases the total removal of organic micropollutants and has an impact on microbial activity without pronounced effects on dissolved organic matter removal.

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