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The potential for phosphorus pollution remediation by calcite precipitation in UK freshwaters
C. Neal
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2001,
Abstract: This paper examines the potential for calcium carbonate to reduce phosphate pollution in freshwaters by co-precipitation, a process known as a "self cleansing mechanism". Calcium carbonate saturation levels and phosphate concentrations (SRP - soluble reactive phosphate) across the major eastern UK river basins are examined to test for solubility controls. The study shows that calcite saturation varies for each catchment as a function of flow and biological activity rather than by direct regulation by SRP. Indeed, there is no evidence, for any of the rivers studied, that calcite solubility controls hold. However, for groundwater and groundwater-fed springs in the Chalk of the Thames basin, calcite saturation is observed with associated low SRP levels. A self-cleansing mechanism may well be operative within the Chalk due to two factors. Firstly, there is a high potential for nucleation on the calcite micro-crystals in the aquifer. Secondly, there are within aquifer reactions that remove the calcite nucleating inhibitors (SRP and dissolved organic carbon, DOC) to levels lower than those occurring within the rivers do. These inhibitors enter the catchment at very high concentrations in association with agricultural pollution (fertilizer application and animal slurry) and household contamination (e.g. sewage sources from septic tanks). Under low flow conditions, when the saturation index for calcite is at its highest, so too is the concentration of the nucleation inhibitor SRP. Companion work shows that calcite precipitation can occur at the water-sediment interface of the river and this may involve SRP removal. The data, as a whole, define an apparent bound for calcite solubility control where in the presence of nucleating centres, SRP must be less than 4 mM-P l-1 and DOC must be less than 150 mM-C l-1: a condition that does not seem to pertain within most UK rivers. Keywords: calcite, calcium carbonate, phosphate, soluble reactive phosphate, dissolved organic carbon, LOIS, UK, rivers, self-cleansing mechanisms.
The composition and flux of particulate and dissolved carbohydrates from the Rh ne River into the Mediterranean Sea  [PDF]
C. Panagiotopoulos,R. Sempéré,J. Para,P. Raimbault
Biogeosciences Discussions , 2011, DOI: 10.5194/bgd-8-11165-2011
Abstract: Carbohydrates are important components of the carbon cycle and may be used as indicators of the origin and the diagenetic status of marine and terrestrial organic matter. Nevertheless, comprehensive studies of both particulate (PCHO) and dissolved (DCHO) carbohydrates in rivers are scarce, and the seasonal and interannual variability of these compounds in relationship to the bulk particulate (POM) and dissolved organic matter (DOM) is largely unknown. For the period 2007–2009, we sampled once per month POM and DOM and measured the total suspended matter (TSM), POM, DOM, PCHO, and DCHO for the Rh ne River, which flows into the Mediterranean Sea. Using these measurements, we estimated for the above parameters annual fluxes for the period 2001–2010. The estimated carbohydrate fluxes averaged 0.061±0.043×1010 moles Cy 1 for PCHO and 0.041±0.0062×1010 moles Cy 1 DCHO, representing 8% and 7% of the annual flux of POC and DOC, respectively. During flood and low-water periods, POM variations were reflected into the PCHO pool, whereas this was not observed for DOC and DCHO, indicating a decoupling between particulate and dissolved organic matter. Our results also showed that flood and low-water periods may be differentiated using the ratios PCHO/DCHO and POC/DOC, which had a significant linear relationship. Based on the carbohydrate abundances in both the PCHO and DCHO pools, we conclude that this material mainly derives from allochthonous sources (vascular plants, bacteria and soils). Moreover, during flood events, an enrichment in mannose in POM was observed, probably reflecting an angiosperm source (leaves or grasses). By expanding our results to the northwestern Mediterranean Sea (Gulf of Lions), we found that the total organic carbon (TOC) fluxes of the Rh ne River accounted for ~1% of the standing stock of seawater TOC. Considering that glucose is the most abundant carbohydrate in both particulate and dissolved organic matter pools (~33%), its annual flux in the northwestern Mediterranean Sea was estimated to 19.2×108 moles glucose-C.
Removal of both dissolved and particulate iron from groundwater  [PDF]
K. Teunissen,A. Abrahamse,H. Leijssen,L. Rietveld
Drinking Water Engineering and Science Discussions , 2008,
Abstract: Iron is the primary source for discolouration problems in the drinking water distribution system. The removal of iron from groundwater is a common treatment step in the production of drinking water. Even when clear water meets the drinking water standards, the water quality in the distribution system can deteriorate due to settling of iron (hydroxide) particles or post-treatment flocculation of dissolved iron. Therefore it is important to remove dissolved and particulate iron to a large extent. This paper describes the study towards the current iron removal processes and experimental work towards improving removal of dissolved and particulate iron. The study was carried out at groundwater treatment plant Harderbroek, consisting of aeration, rapid sand filtration and tower aeration. The research contains two parts: 1) a particle fingerprint of the treatment, resulting in a quantification of particles breaking through the rapid sand filtration. 2) Small column experiments on the oxidation and filterability of iron. The fingerprint showed that operational events such as switching on/off of filters and backwashing have a significant impact on the volume concentration of particles breaking through the filter. A frequency plot of the different size ranges of particles indicates that mainly the filterability of the middle size ranges (2–7 μm) of particles was influenced by switching a filter on/off. A backwash event mainly affects the bigger particle size ranges. The column experiments showed that in the cascade effluent the majority of the iron is dissolved iron(II), indicating that the oxidation of iron(II) to iron(III) is the rate determining step at Harderbroek, which is limited by pH. Dosing caustic soda resulted in a significant increase of the oxidation rate and improved the removal of iron(II) in the column. Crushed limestone filtration gave promising results, but the contact time applied was too short to completely oxidize iron(II).
Dissolved and particulate reactive nitrogen in the Elbe River/NW Europe: a 2-yr N-isotope study
T. Schlarbaum, K. D hnke,K. Emeis
Biogeosciences (BG) & Discussions (BGD) , 2011,
Abstract: Rivers collect and transport reactive nitrogen to coastal seas as nitrate, ammonium, dissolved organic nitrogen (DON), or particulate nitrogen. DON is an important component of reactive nitrogen in rivers and is suspected to contribute to coastal eutrophication, but little is known about seasonality of DON loads and turnover within rivers. We measured the concentrations and the isotope ratios 15N/14N of combined DON + NH4+ (δ15DON + NH4+), nitrate (δ15N NO3 ) and particulate nitrogen (δ15PN) in the non-tidal Elbe River (SE North Sea, NW Europe) over a period of 2 yr (June 2005 to December 2007) at monthly resolution. Combined DON + NH4+ concentrations ranged from 22 to 75 μM and comprised nearly 23% of total dissolved nitrogen in the Elbe River in annual mean; PN and nitrate concentrations ranged from 11 to 127 μM, and 33 to 422 μM, respectively. Combined PN and DON + NH4+ concentrations were, to a first approximation, inversely correlated to nitrate concentrations. δ15DON + NH4+, which varied between from 0.8‰ to 11.5‰, changed in parallel to δ15PN (range 6 to 10‰), and both were anti-correlated to δ15N NO3 (range 6 to 23‰). Seasonal patterns of DON + NH4+ concentrations and δ15DON + NH4+ diverge from those expected from biological DON + NH4+ production in the river alone and suggest that the elution of organic fertilisers significantly affects the DON + NH4+ pool in the Elbe River.
Dissolved and particulate reactive nitrogen in the Elbe River/NW Europe: a 2-year N-isotope study  [PDF]
T. Schlarbaum,K. D?hnke,K. Emeis
Biogeosciences Discussions , 2010, DOI: 10.5194/bgd-7-7543-2010
Abstract: Rivers collect and transport reactive nitrogen to coastal seas as nitrate, ammonium, dissolved organic nitrogen (DON), or particulate nitrogen. DON is an important component of reactive nitrogen in rivers and is suspected to contribute to coastal eutrophication, but little is known about seasonality of DON loads and turnover within rivers. We measured the concentrations and the isotope ratios 15N/14N of combined DON+NH4+ (δ15DON+NH4+), nitrate (δ15N NO3 ) and particulate nitrogen (δ15PN) in the non-tidal Elbe River (SE North Sea, NW Europe) over a period of 2 years (June 2005 to December 2007) at monthly resolution. Combined DON+NH4+ concentrations ranged from 22 to 75 μM and comprised nearly 23% of total dissolved nitrogen in the Elbe River in annual mean; PN and nitrate concentrations ranged from 11 to 127 μM, and 33 to 422 μM, respectively. Combined PN and DON+NH4+ concentrations were, to a first approximation, inversely correlated to nitrate concentrations. δ15DON+NH4+, which varied between from 0.8‰ to 11.5‰, changed in parallel to δ15PN (range 6 to 10‰), and both were anti-correlated to δ15N NO3 (range 6 to 23‰). Seasonal patterns of DON+NH4+ concentrations and δ15DON+NH4+ diverge from those expected from biological DON+NH4+ production in the river alone and suggest that the elution of organic fertilisers significantly affects the DON+NH4+ pool in the Elbe River.
Quantification of Dissolved and Particulate Polyunsaturated Aldehydes in the Adriatic Sea  [PDF]
Charles Vidoudez,Raffaella Casotti,Mauro Bastianini,Georg Pohnert
Marine Drugs , 2011, DOI: 10.3390/md9040500
Abstract: Polyunsaturated aldehydes (PUA) are supposed to play critical roles in chemically-mediated plankton interactions. Laboratory studies suggest that they act as mediators of chemical defense and chemical communication. PUA are oxylipins containing an α,β,γ,δ-unsaturated aldehyde structure element and are mainly found in diatoms. We present here a detailed surface mapping of PUA during a spring bloom of the diatom Skeletonema marinoi in the Adriatic Sea. We monitored dissolved PUA, as well as particulate PUA, which are produced by phytoplankton after cell disintegration. Our survey revealed a patchy distribution of PUA and shows that at most stations S. marinoi is the major contributor to the overall PUA. Our data also suggest that lysis of a diatom bloom can contribute significantly to the dissolved PUA concentrations and that other producers, which are smaller in cell size compared to diatoms, have to be taken into account as well if the total PUA content of marine samples is considered. The analyses of samples collected in deeper water suggests that diatom contribution to PUA decreases with depth, while smaller-sized unidentified organisms take place as dominant contributors to the PUA concentrations.
Dissolved and Particulate Dimethylsulfoxide in the South China Sea During Winter Dissolved and Particulate Dimethylsulfoxide in the South China Sea During Winter  [PDF]
YANG Jie,YANG Guipeng
- , 2018,
Abstract: The distributions of particulate and dissolved dimethylsulfoxide(DMSOp, DMSOd) were studied for the first time in the surface water of the South China Sea(SCS) in January 2010. The concentrations of DMSOp ranged from 2.6 to 56.8 nmol L~(-1) with an average of 11.1 ± 2.2 nmol L~(-1), and those of DMSOd ranged from 11.8 to 335.1 nmol L~(-1) with an average of 50.0 ± 16.5 nmol L~(-1). DMSOd dominated over both dimethylsulfide(DMS) and dissolved dimethylsulfoniopropionate(DMSPd) by 1–3 orders of magnitude and represented the major dissolved dimethyl sulfur pool. In addition, DMSOp/chlorophyll-a ratios varied from 2.7 to 180.7 mmol g~(-1) with an average of 30.5 ± 9.6 mmol g~(-1). DMSOd concentrations displayed a significant negative relationship with sea surface temperature(SST) and sea surfaces salinity(SSS) in the whole study area. The distribution of DMSOd in the coastal waters was obviously influenced by the Pearl River discharge, with high concentrations appearing around the river mouth. In the offshore waters, a significant correlation was observed between the DMSOp and DMSOd concentrations, suggesting that DMSOd was mainly from the diffusion of intracellular DMSO rather than from the photochemical and biological oxidation of DMS
THE INFLUENCE OF PONDS ON DISSOLVED OXYGEN IN SMALL RIVERS OF BERRY (FRANCE)
Laurent TOUCHART,Pascal BARTOUT,Abdelhamid AZAROUAL
Aerul ?i Apa : Componente ale Mediului , 2012,
Abstract: The influence of ponds on dissolved oxygen in small rivers of Berry (France). Water temperature and oxygen saturation are two major indicators of water quality in surface hydrology. Geographical and cartographic studies about ponds of Central France did no exist until now. During two years, we measured dissolved oxygen using a hand oximeter upstream and downstream of three ponds in the headwaters of the Loire basin. Our results show that oxygen saturation depends on equipments located before and behind the dam, and upstream and downstream: spillways, outlets with a monk, diversion channel, artificial reoxygenation weirs and so on. In some cases (low water quality upstream, existence of weir), relative and absolute saturation of dissolved oxygen increases downstream of ponds.
Spatial and temporal variations in dissolved and particulate organic nitrogen in the equatorial Pacific: biological and physical influences
X. J. Wang, R. Le Borgne, R. Murtugudde, A. J. Busalacchi,M. Behrenfeld
Biogeosciences (BG) & Discussions (BGD) , 2008,
Abstract: To quote Libby and Wheeler (1997), "we have only a cursory knowledge of the distributions of dissolved and particulate organic nitrogen" in the equatorial Pacific. A decade later, we are still in need of spatial and temporal analyses of these organic nitrogen pools. To address this issue, we employ a basin scale physical-biogeochemical model to study the spatial and temporal variations of dissolved organic nitrogen (DON) and particulate organic nitrogen (PON). The model is able to reproduce many observed features of nitrate, ammonium, DON and PON in the central and eastern equatorial Pacific, including the asymmetries of nitrate and ammonium, and the meridional distributions of DON and PON. Modeled DON (5–8 mmol m 3) shows small zonal and meridional variations in the mixed layer whereas modeled PON (0.4–1.5 mmol m 3) shows considerable spatial variability. While there is a moderate seasonality in both DON and PON in the mixed layer, there is a much weaker interannual variability in DON than in PON. The interannual variability in PON is largely associated with the El Ni o/Southern Oscillation (ENSO) phenomenon, showing high values during cold ENSO phase but low values during warm ENSO phase. Overall, DON and PON have significant positive correlations with phytoplankton and zooplankton in the mixed layer, indicting the biological regulation on distribution of organic nitrogen. However, the relationships with phytoplankton and zooplankton are much weaker for DON (r=0.18–0.71) than for PON (r=0.25–0.97). Such a difference is ascribed to a relatively larger degree of physical control (e.g., upwelling of low-organic-N deep waters into the surface) on DON than PON.
Spatial and temporal variations in dissolved and particulate organic nitrogen in the equatorial Pacific: biological regulations and physical influences  [PDF]
X. J. Wang,R. Le Borgne,R. Murtugudde,A. J. Busalacchi
Biogeosciences Discussions , 2008,
Abstract: To quote Libby and Wheeler (1997), "we have only a cursory knowledge of the distributions of dissolved and particulate organic nitrogen" in the equatorial Pacific. A decade later, we are still in need of spatial and temporal analyses of these organic nitrogen pools. To address this issue, we employ a basin scale physical-biogeochemical model to study the spatial and temporal variations of dissolved organic nitrogen (DON) and particulate organic nitrogen (PON). The model is able to reproduce many observed features of nitrate, ammonium, DON and PON in the central and eastern equatorial Pacific, including the asymmetries of nitrate and ammonium, and the meridional distributions of DON and PON. Modeled DON (5–8 mmol m 3) shows small zonal and meridional variations in the mixed layer whereas modeled PON (0.4–1.5 mmol m 3) shows considerable spatial variability. While there is a moderate seasonality in both DON and PON in the mixed layer, there is a much weaker interannual variability in DON than in PON. The interannual variability in PON is largely associated with the El Ni o/Southern Oscillation (ENSO) phenomenon, showing high values during cold ENSO phase but low values during warm ENSO phase. Overall, DON and PON have significant positive correlations with phytoplankton and zooplankton in the mixed layer. However, the relationships with phytoplankton and zooplankton are much weaker for DON (r=0.18–0.71) than for PON (r=0.25–0.97). Such a difference is ascribed to a larger degree of physical control (e.g., upwelling of low-organic-N deep waters into the surface) on DON than PON. On the whole, distribution of organic nitrogen appears to be controlled by biological influences in the equatorial Pacific.
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