scholarly journals Dissolved organic carbon and nitrate flows in two micro-watersheds with different land uses

2021 ◽  
Vol 42 (2) ◽  
pp. 553-564
Author(s):  
Tulio Gonçalves dos Santos ◽  
◽  
Ricardo Santos Silva Amorim ◽  
Edwaldo Dias Bocuti ◽  
Oscarlina Lúcia dos Santos Weber ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Waters ◽  
Water Samples ◽  
Agricultural Watershed ◽  
Land Uses ◽  
Cerrado Vegetation ◽  
Hydraulic Load ◽  
Agricultural Site ◽  
Rainy Days

he impacts of human activities on watersheds can change the quality and possible uses of water resources. In this context, we evaluated the flows of dissolved organic carbon (DOC) and nitrate (NO3) in the surface waters of two micro-watersheds with different anthropic impacts. Water samples were collected from two micro-watersheds with different land uses (regenerated savanna and an agricultural site) from January 2014 to April 2015. In the rainy season, the samples were collected every 15 days, while in the dry season, samples were collected every 30 days. An automatic sampler in the stream collected the composed samples. Water flow was monitored with a sensor that measured the hydraulic load on the sill of the triangular spillway installed in each micro-watershed. The DOC and NO3 contents were analyze via UV-Vis spectrophotometry. The flow was estimated based on the DOC and NO3 flows and concentrations. The DOC concentrations were higher in the Cerrado micro-watershed; however, there was no difference in NO3 concentrations. In both watersheds, there was a significant increase in the concentrations of DOC and NO3 on rainy days, with was more pronounced in the agricultural watershed. The DOC and NO3 flows were higher in the micro-watershed with Cerrado vegetation on days with rain; while on days without rain, there was no difference.

Minimization of the Disinfection by-Product Precursors in Treated Waters Exposed to Ozone and Chlorine

2014 ◽  
Vol 884-885 ◽  
pp. 91-95
Author(s):  
Shang Chao Yue ◽  
Le Jun Zhao ◽  
Xiu Duo Wang ◽  
Qi Shan Wang ◽  
Feng Hua He
Keyword(s):  
Drinking Water ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Supply ◽  
River Water ◽  
Water Samples ◽  
Full Scale ◽  
Ultraviolet Absorbance ◽  
Treatment Processes ◽  
Removal Efficiencies

The objectives of this study were to investigate impact of preoxidation on disinfection by-product (DBP) precursors in drinking water via two different preoxidation methods. The full-scale study was conducted on surface river water in a water supply plant in Tianjin, China. Two treatment trains were performed, with prechlorination and preozonation as preoxidation methods, respectively. The water samples were collected on different stages along the treatment processes and analyzed by following organic parameters: dissolved organic carbon (DOC), UV254 and specific ultraviolet absorbance (SUVA). The results indicated that Train 2 with preozonation was more effective to reduce DBP precursors. Preozonation possessed an excellent ability in the removal of UV254 and SUVA, the removal efficiencies were 25.14% and 18.77%, respectively, comparing to the removal rates of 6.66% and 5.64% during prechlorination, separately.

scholarly journals Distribution and bacterial availability of dissolved neutral sugars in the South East Pacific

2008 ◽  
Vol 5 (4) ◽  
pp. 1165-1173 ◽  
Author(s):  
R. Sempéré ◽  
M. Tedetti ◽  
C. Panagiotopoulos ◽  
B. Charrière ◽  
F. Van Wambeke
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Waters ◽  
Detectable Effect ◽  
Neutral Sugar ◽  
The South ◽  
East Pacific ◽  
Significant Stimulation ◽  
Order Of Magnitude ◽  
Neutral Sugars

Abstract. The distribution and bacterial availability of dissolved neutral sugars were studied in the South East Pacific from October to December 2004 during the BIOSOPE cruise. Four contrasting stations were investigated: Marquesas Islands (MAR), the hyper-oligotrophic South Pacific Gyre (GYR), the eastern part of the Gyre (EGY), and the coastal waters associated to the upwelling area off Chile (UPW). Total (free and combined) dissolved neutral sugar (TDNS) concentrations were in the same order of magnitude at MAR (387±293 nM), GYR (206±107 nM), EGY (269±175 nM), and UPW (231±73 nM), with the highest and lowest concentrations found at MAR (30 m, 890 nM) and EGY (250 m, 58 nM), respectively. Their contribution to dissolved organic carbon (TDNS-C×DOC−1%) was generally low for all sites varying from 0.4% to 6.7% indicating that South East Pacific surface waters were relatively poor in neutral sugars. Free dissolved neutral sugar (FDNS; e.g. sugars analyzed without hydrolysis) concentrations were very low within the detection limit of our method (5–10 nM) accounting for <5% of the TDNS. In general, the predominant sugars within the TDNS pool were glucose, xylose, arabinose, and galactose, while in the FDNS pool only glucose was present. TDNS stock to bacterial production ratios (integrated values from the surface to the deep chlorophyll maximum) were high at GYR with respect to the low primary production, whereas the opposite trend was observed in the highly productive area of UPW. Intermediate situations were observed for MAR and EGY. Bioavailability of dissolved organic matter (DOM) exposed to natural solar radiation was also experimentally studied and compared to dark treatments. Our results showed no or little detectable effect of sunlight on DOM bacterial assimilation in surface waters of UPW and GYR, while a significant stimulation was found in MAR and EGY. The overall results clearly suggest that DOM is less labile at GYR compared to UPW, which is consistent with the observed accumulation of dissolved organic carbon and the elevated C/N ratios reported by Raimbault et al. (2008).

scholarly journals Storm Dissolved Organic Carbon Dynamics in an Artificially Drained Watershed of the US Midwest

2012 ◽  
Vol 5 ◽  
pp. ASWR.S9973 ◽  
Author(s):  
Philippe G. Vidon ◽  
Hilary A Hubbard ◽  
Pilar E. Cuadra ◽  
Matthew L. Hennessy
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Overland Flow ◽  
Agricultural Watershed ◽  
Antecedent Moisture ◽  
Tile Drains ◽  
The Us ◽  
Moisture Conditions ◽  
Subsurface Drains ◽  
Antecedent Moisture Conditions

This study investigates changes in the nature, concentrations, and fluxes of dissolved organic carbon (DOC) in tile drains (aka subsurface drains), overland flow, and stream flow for 6 spring storms in an artificially drained agricultural watershed. For moderate size storms, DOC concentrations are primarily affected by variations in antecedent moisture conditions. Generally, DOC concentrations and aromaticity increase with flow, especially for storms associated with high antecedent moisture conditions. A shift in the source of DOC to the stream and tile drains from low aromaticity DOC at baseflow, to more aromatic DOC during storms was observed. Data indicates that increases in the frequency and intensity of large precipitation events as well as wetter conditions in spring would likely lead not only to an increase in DOC fluxes (simply because of higher discharge) but also to an increase in the amount of DOC exported for every unit of flow.

scholarly journals Physical fractionation of organic carbon in areas under different land uses in the Cerrado

2020 ◽  
Vol 24 (8) ◽  
pp. 534-540
Author(s):  
Adilson A. Costa ◽  
Bruno de O. Dias ◽  
Vânia da S. Fraga ◽  
Charles C. Santana ◽  
Thalita F. Sampaio ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Agricultural Production ◽  
Conventional Tillage ◽  
Land Uses ◽  
Eucalyptus Plantation ◽  
Cerrado Vegetation ◽  
Physical Fractionation ◽  
C Stocks ◽  
Positive Effect

ABSTRACT With the expansion of agricultural production, native Cerrado areas are replaced with other forms of land use. Thus, the objective of this study was to evaluate changes in the physical fractionation of organic carbon (C) in areas under different forms of land use in the Cerrado. The treatments, with five repetitions, corresponded to the following forms of use: area under conventional tillage, area under pasture plantation, area under eucalyptus plantation and area under native Cerrado vegetation, at the depths of 0-5, 5-10, 10-15 and 15-20 cm in the municipality of Luis Eduardo Magalhães, BA, Brazil. The highest C contents and stocks were found in the eucalyptus area, which were equal to those of the area under native Cerrado vegetation, while particulate C stocks were higher in the area under pasture at the depth up to 10 cm, not differing from the area under native Cerrado. Pasture and eucalyptus had positive effect on C management index, regardless of depth.

Influence of catchment topography on water chemistry in southeastern Québec Shield lakes

1997 ◽  
Vol 54 (10) ◽  
pp. 2215-2227 ◽  
Author(s):  
Pierre D'Arcy ◽  
Richard Carignan
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Water Chemistry ◽  
Surface Waters ◽  
Overland Flow ◽  
Canadian Shield ◽  
Chl A ◽  
Lake Water Chemistry ◽  
High Runoff ◽  
Shield Lakes

For 30 Canadian Shield lakes of southeastern Quebec, catchment slope and lake morphometry account for 50-70% of the variability of chlorophyll a (Chl a), dissolved organic carbon (DOC), total phosphorus (TP), NO3- , and NH4+ . Dissolved organic carbon, TP, Chl a, Ca, and Mg are negatively related to catchment slope, whereas NO3- and NH4+ increase with increasing slope. Concentrations of more conservative constituents (SO42-, Na, K) increase with decreasing elevation as a result of higher evapotranspiration and lower precipitation at low elevations. Catchment variables (slope, drainage area, percent wetlands) are as good predictors of Chl a (r2 = 0.7) as are water chemistry variables (TP, Ca, Mg, and pH). Dominant vegetation (deciduous vs. coniferous) has little or no influence on lake water chemistry. Hydrogeological data for the Canadian Shield suggest that, during periods of high runoff, the development of waterlogged areas and the importance of overland flow on saturated soils are inversely proportional to catchment slope. We propose that the strong influence of catchment slope on water quality is due to slope-dependent seasonal waterlogging, which determines the fate (retention or export to surface waters) of dissolved substances produced within and moving through the forest floor.

scholarly journals Modelling the effects of climate on long-term patterns of dissolved organic carbon concentrations in the surface waters of a boreal catchment

2008 ◽  
Vol 12 (2) ◽  
pp. 437-447 ◽  
Author(s):  
M. N. Futter ◽  
M. Starr ◽  
M. Forsius ◽  
M. Holmberg
Keyword(s):  
Surface Water ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Waters ◽  
Organic Soils ◽  
Catchment Scale ◽  
Changing Climate ◽  
Recovery From Acidification ◽  
Carbon Concentrations ◽  
Process Based Models

Abstract. Dissolved organic carbon concentrations ([DOC]) in surface waters are increasing in many regions of Europe and North America. These increases are likely driven by a combination of changing climate, recovery from acidification and change in severity of winter storms in coastal areas. INCA-C, a process-based model of climate effects on surface water [DOC], was used to explore the mechanisms by which changing climate controls seasonal to inter-annual patterns of [DOC] in the lake and outflow stream of a small Finnish catchment between 1990 and 2003. Both production in the catchment and mineralization in the lake controlled [DOC] in the lake. Concentrations in the catchment outflow were controlled by rates of DOC production in the surrounding organic soils. The INCA-C simulation results were compared to those obtained using artificial neural networks (ANN). In general, "black box" ANN models provide better fits to observed data but process-based models can identify the mechanism responsible for the observed pattern. A statistically significant increase was observed in both INCA-C modelled and measured annual average [DOC] in the lake. This suggests that some of the observed increase in surface water [DOC] is caused by climate-related processes operating in the lake and catchment. However, a full understanding of surface water [DOC] dynamics can only come from catchment-scale process-based models linking the effects of changing climate and deposition on aquatic and terrestrial environments.

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