Papers by Victoria Nicole Deycard
Chemical Research in Toxicology, May 25, 2022
Chemosphere, 2017
Although silver (Ag) has been listed as a priority pollutant for the aquatic environment by the E... more Although silver (Ag) has been listed as a priority pollutant for the aquatic environment by the European Union (Directive 2006/11/EC), the use of Ag-based products with antimicrobial effects is increasing in Europe, as well as North America and Asia. This study investigates personal care products (PCP) as a potential source of Ag in wastewater, as well as the dynamics and fate of Ag in the influent and effluent of a major urban wastewater treatment plant (WWTP) located on the fluvial part of the Gironde Estuary. Typical household PCPs marked as using Ag contained concentrations of up to 0.4 mg kg(-1) making them likely contributors to urban Ag released into the aquatic environment. Silver concentrations in influent wastewater generally occurred during mid-week working hours and decreased during the night and on weekends clearly indicating the dominance of urban sources. Up to 90% of the total Ag in wastewater was bound to particles and efficiently (>80%) removed by the treatment process, whereas 20% of Ag was released into the fluvial estuary. Silver concentrations in wastewater effluents clearly exceeded estuarine concentrations and may strongly amplify the local Ag concentrations and fluxes, especially during summer rainstorms in low river discharge conditions. Further work should focus on environmental effects and fate of urban Ag release due to immediate localized outfall and/or the adsorption on estuarine particles and subsequent release as dissolved Ag chloro-complexes within the estuarine salinity gradient.
Marine Chemistry, Dec 1, 2014
ABSTRACT Urban wastewater metal inputs into coastal systems are of increasing interest to both sc... more ABSTRACT Urban wastewater metal inputs into coastal systems are of increasing interest to both scientists and managers facing restrictive environmental protection policies, population increase and changing metal applications. However, their impact and contribution to metal loads in estuarine and coastal environments is widely unknown due to the lack of (i) monitoring in both artificial and natural aquatic systems and (ii) an understanding of control parameters, such as spatial and temporal variations in hydrological conditions. We investigated the daily concentrations, fluxes and dynamics of seven EU priority contaminants (potentially toxic metals Cd, Cu, Cr, Ni, Pb, Zn and the metalloid As) transported by the Garonne River (La Réole site; watershed area ~ 57,000 km2) to those released into the freshwater reaches of the Gironde Estuary (Garonne Branch) by two main wastewater treatment plants (WWTPs) of Bordeaux under low river discharge and contrasting rainfall situations. During short intense summer rainstorms, wastewater flow into the WWTPs increased by up to 150 % and 60 %, respectively, resulting in an increase of 70 % (As) to 200 % (Pb) for fluxes entering the treatment plants. Overall resulting WWTP particulate and dissolved effluent concentrations were up to 2 (Cr), 3 (Pb, Cu and Ni) and 5 (Cd and Zn) times higher than measured upstream in the Garonne River, respectively. During low-discharge, maximum outlet fluxes at the WWTPs were similar to respective watershed-derived fluxes in the Garonne River. During rain events, Pb in all fractions, total and dissolved Cu and total and particulate Zn fluxes entering the fluvial estuary were close to the respective minimum flux values at the La Réole site. Furthermore, during rain episodes, particulate Cu and dissolved Zn fluxes from the WWTPs to the fluvial estuary were greater than those transported by the Garonne River at the La Réole site. Mixing of treated wastewater with highly turbid estuarine freshwater most likely results in a re-equilibration between the dissolved and particulate phases, although biogeochemical processes in downstream estuarine turbidity and salinity gradients may partly reverse contaminant adsorption on estuarine particles. Accordingly, urban wastewater contaminant release clearly impacts estuarine water quality before being expulsed to the Bay of Biscay.
This study is a part of the third axis of the « ETIAGE » project, a four year collaboration (2010... more This study is a part of the third axis of the « ETIAGE » project, a four year collaboration (2010-2014) between the Lyonnaise des Eaux, the Communauté Urbaine de Bordeaux (CUB), AEAG, and FEDER, Aquitaine region with the University of Bordeaux, CNRS and IRSTEA. The axis 3 objectives were to document the trace metal inputs from the CUB watershed into the waters of the Garonne section of the Gironde estuary. The Gironde Estuary is one of the largest macrotidal and highly turbid estuaries in Western Europe characterized by the presence of a strong maximum turbidity zone (MTZ) with high suspended particulate matter (SPM) concentrations (>1 g.L-1 in surface water) transporting estuarine particles and potentially hazardous trace elements. This study has focused on the trace metal inputs from the two main wastewater treatment plants (WWTP) of the CUB. The objective of this research was therefore to study in detail the daily concentrations, fluxes, and dynamics of 8 EU priority contaminants Cr, Cu, Cr, Hg, Ni, Pb Zn, As, and the emerging contaminant Ag from the WWTPs in the CUB. The calculated removal rates are significant, around 80 % for the majority of metals, mainly as a result of the decantation phase. Despite this high removal efficiency, during periods of heavy rainstorms and low river discharges, the urban metal inputs via the WWTPs may still significantly increase metal concentrations and fluxes in the fluvial Gironde Estuary impacting water quality. In addition, the WWTP fluxes and concentrations of Ag exceeded common background concentrations in the Gironde fluvial estuary, making it an interesting urban tracer. The treatment within the WWTPs concentrates the trace metals in the sludge, yet, metal concentrations remained below legal norms for agricultural use. However, the analysis of WWTP sludge revealed that trace element concentrations are 15 (Ag) and 30 (Cu) times higher than natural background concentrations with high enrichment of Hg, Ag, Cr, Cu and Zn with over 70 % of Cd, Ag, Pb, Cu, and Zn being potentially bioavailable. Therefore, with increasing urban pressure on environmental quality, these results support the need for the development of efficient water quality monitoring tools.
Cette these s’integre dans l’axe 3 du programme « ETIAGE » qui a associe pendant quatre ans (2010... more Cette these s’integre dans l’axe 3 du programme « ETIAGE » qui a associe pendant quatre ans (2010-2014) la Lyonnaise des Eaux, la Communaute Urbaine de Bordeaux (CUB), l’AEAG, et le FEDER, region Aquitaine avec l’universite de Bordeaux, le CNRS et IRSTEA. L’objectif de l’axe 3 etait de documenter les apports metalliques du bassin versant de la CUB aux eaux de la section garonnaise de l’estuaire de la Gironde. Ce vaste estuaire europeen est l’un des plus turbides au monde, avec en periode d’etiage la presence devant Bordeaux d’une zone de turbidite maximum (ZTM, >1 g.L-1 de MES en surface) qui transporte des particules estuariennes et des elements traces potentiellement toxiques. Les travaux de cette these se sont focalises sur les apports metalliques via le fonctionnement des deux principales stations d’epuration (STEP) de la CUB. De ce fait, l’objectif de cette recherche est d’analyser en detail les concentrations, les flux et la reactivite de huit contaminants metalliques defin...
Chemical Research in Toxicology
Soil Organic Carbon (SOC) is an integral part of maintaining and measuring soil sustainability. T... more Soil Organic Carbon (SOC) is an integral part of maintaining and measuring soil sustainability. This study was undertaken to document and better understand the effect of agro ecosystems on SOC. The methods used were to compare SOC content and 13C isotopes from the total soil and particulate organic matter fraction (POM) of two agro ecosystems. This research was conducted on the Texas High Plains, a semiarid region. The two systems included in the study were a continuous cotton (Gossypium hirsutum L.) monoculture system and cotton and beef cattle (Bos Taurus L.) grazing system. The cotton and beef cattle grazing system is comprised of 53.6% WW-B Dahl old world bluestem [Bothriochloa bladhii (Retz) S.T. Blake; OWB], a perennial warm-season grass and the other 46.4 % of the system is divided in two paddocks of equal size where no-till cotton is grown alternately with cereal rye (Secale cereal L.) and wheat (Triticum aestivum L.). With a livestock-crop rotation system that has varying cover crop residues from different forage species and input returns from the livestock, it becomes difficult to understand the main contributing factor to the increase or decrease of SOC sequestered within the system. Because C3 (trees, shrubs, and cool season grasses) and C4 plants (warm season grasses) have a specific isotopic ratio variation of δ13C (‰) in SOC, the δ-13C isotope ratios were used to trace the percentage of SOC to its source. An investigation was made of both the total soil organic carbon (TSOC) and the particulate organic carbon (POC). The POC is the carbon found within the sand size fraction, also known as the particulate organic matter carbon (POM) and is comprised of partially decomposed organic matter. This fraction revealed dynamics regarding the more current management system. Warm season grasses produce about twice as much biomass as cool season grasses and it was hypothesized that the cropping system that integrated warm season grasses and livestock with cotton would return higher inputs of C to the soil and would have lower carbon turnover rates than a continuous cotton monoculture, thus improving soil sustainability. The integrated livestock-crop system sequestered 30% more SOC than the continuous cotton monoculture system. The WW B-Dahl old world bluestem system component was the more significant contributor to higher carbon returns having 19.6 Mg ha-1 of SOC and sequestering 43% more soil organic carbon than the continuous cotton monoculture. The no-till cotton/ cereal rye/ wheat rotation (RCW/WFR) system component had 10 Mg ha-1 ±1 SOC and sequestered 16 ±3% more SOC than the conventionally-tilled cotton. The conventional tilled continuous cotton monoculture decreased soil sustainability and resulted in SOC loss on the surface with a vertical distribution of 1.1,1.4, and 1.5 Mg ha-1 at the 0-5, 5-10, and 10-20 cm depth, respectively, for the continuous cotton monoculture. There was an increase in POC with depth in the soil profile in the continuous cotton monoculture system. This suggests current management is effecting changes deeper in the soil plow layer for the continuous cotton monoculture than for the integrated system. Vertical distribution of POC within paddocks displayed a significant decrease in carbon 0-5 >5-10>10-20 cm for all paddocks except the conventional-till continuous cotton monoculture. POC for the 0-5, 5-10, 10-20 cm depth were 1.97, 0.53, and 0.23 Mg ha-1 cm-1 for OWB, 1.38, 0.42 and 0.27 Mg ha-1 cm-1 for RCW, 0.74, 0.33, and 0.16 Mg ha-1 cm-1 for the WFR and 0.26, 0.36, and 0.32 Mg ha-1 cm-1 for the continuous cotton monoculture. Carbon isotope signatures from soils sampled in 1997 at the initiation of the field experiment compared with soils sampled from 2007 showed that soil became less enriched with 13C in paddocks with C3 plant inputs. The 1997 δ13C values were ~-15.0‰ a result of C4 native grasses and more recent C4 plant inputs. Current soil δ13C values range from -21.1‰ to -16.1‰ and values decreased with depth for the integrated cotton-forage-livestock system and remained consistently less enriched in 13C isotopes throughout the 0-20 cm depth. The highest value (21.1 ‰) was found in the continuous cotton monoculture system demonstrating that it is having more of an effect on carbon turnover. The integrated cotton-forage-livestock system had an overall increase in SOC while retaining the carbon in the system from past land management practices and a decrease in C3/C4 carbon turnover. A system that increases SOC and also protects carbon that is already in the system may provide economic incentives for land managers if carbon credit systems are implemented. In addition, a system with slower carbon turnover rates sequesters more carbon if carbon inputs are higher than conventional monoculture systems.
ABSTRACT Urban wastewater metal inputs into coastal systems are of increasing interest to both sc... more ABSTRACT Urban wastewater metal inputs into coastal systems are of increasing interest to both scientists and managers facing restrictive environmental protection policies, population increase and changing metal applications. However, their impact and contribution to metal loads in estuarine and coastal environments is widely unknown due to the lack of (i) monitoring in both artificial and natural aquatic systems and (ii) an understanding of control parameters, such as spatial and temporal variations in hydrological conditions. We investigated the daily concentrations, fluxes and dynamics of seven EU priority contaminants (potentially toxic metals Cd, Cu, Cr, Ni, Pb, Zn and the metalloid As) transported by the Garonne River (La Réole site; watershed area ~ 57,000 km2) to those released into the freshwater reaches of the Gironde Estuary (Garonne Branch) by two main wastewater treatment plants (WWTPs) of Bordeaux under low river discharge and contrasting rainfall situations. During short intense summer rainstorms, wastewater flow into the WWTPs increased by up to 150 % and 60 %, respectively, resulting in an increase of 70 % (As) to 200 % (Pb) for fluxes entering the treatment plants. Overall resulting WWTP particulate and dissolved effluent concentrations were up to 2 (Cr), 3 (Pb, Cu and Ni) and 5 (Cd and Zn) times higher than measured upstream in the Garonne River, respectively. During low-discharge, maximum outlet fluxes at the WWTPs were similar to respective watershed-derived fluxes in the Garonne River. During rain events, Pb in all fractions, total and dissolved Cu and total and particulate Zn fluxes entering the fluvial estuary were close to the respective minimum flux values at the La Réole site. Furthermore, during rain episodes, particulate Cu and dissolved Zn fluxes from the WWTPs to the fluvial estuary were greater than those transported by the Garonne River at the La Réole site. Mixing of treated wastewater with highly turbid estuarine freshwater most likely results in a re-equilibration between the dissolved and particulate phases, although biogeochemical processes in downstream estuarine turbidity and salinity gradients may partly reverse contaminant adsorption on estuarine particles. Accordingly, urban wastewater contaminant release clearly impacts estuarine water quality before being expulsed to the Bay of Biscay.
Chemical Geology, 2013
High precision MC-ICP-MS Cu isotope measurements were performed on suspended particulate matter (... more High precision MC-ICP-MS Cu isotope measurements were performed on suspended particulate matter (SPM) and filtered water sampled along the turbidity gradient of the fluvial Gironde Estuary (Garonne Branch), following a summer lasting period of low freshwater discharge. High Cu concentrations (up to~200 μg/g) in particulate organic carbon (POC)-rich (up to~14%) particles upstream from the Maximum Turbidity Zone (MTZ) coincide with the most negative δ 65 Cu values (down to −0.39‰). This suggests the preferential uptake of light Cu isotopes by phytoplankton or anthropogenic contamination from CuSO 4 fungicides related to intensive wine farming in the area (δ 65 Cu = −0.37‰ for vineyard soils). Suspended particulate matter samples in the MTZ exhibit lower Cu concentrations (~35 μg/g) and heavier isotopic compositions (δ 65 Cu = −0.20‰ in average), as recorded by other samples from the Gironde Watershed. Along the fluvial estuary, dissolved Cu is mostly enriched in heavy isotopes (up to δ 65 Cu = + 0.21‰), but negative signatures down to δ 65 Cu = − 0.66‰ occur near the city of Bordeaux. Release of dissolved Cu was attributed to the mineralization of organic matter with a total addition of~600 ng/L in the fluvial estuary. Continuously decreasing amounts of dissolved Cu added with distance suggest that the observed Cu release evolved towards completion in the MTZ and contributed to negative values for dissolved Cu isotopes, as modeled by a Rayleigh process. Urban wastewater effluents probably also contribute to both (i) the dissolved Cu addition (10-20%) in the MTZ and (ii) negative Cu isotope signatures. Further work is necessary to assess the respective roles of anthropogenic sources and biogeochemical fractionation processes. Accordingly, the present study provides new insights into the potential of Cu isotopes for fingerprinting sources and mechanisms involved in the biogeochemical cycle of Cu in temperate aquatic environments impacted by anthropogenic activities.
Chemosphere, 2017
Although silver (Ag) has been listed as a priority pollutant for the aquatic environment by the E... more Although silver (Ag) has been listed as a priority pollutant for the aquatic environment by the European Union (Directive 2006/11/EC), the use of Ag-based products with antimicrobial effects is increasing in Europe, as well as North America and Asia. This study investigates personal care products (PCP) as a potential source of Ag in wastewater, as well as the dynamics and fate of Ag in the influent and effluent of a major urban wastewater treatment plant (WWTP) located on the fluvial part of the Gironde Estuary. Typical household PCPs marked as using Ag contained concentrations of up to 0.4 mg kg(-1) making them likely contributors to urban Ag released into the aquatic environment. Silver concentrations in influent wastewater generally occurred during mid-week working hours and decreased during the night and on weekends clearly indicating the dominance of urban sources. Up to 90% of the total Ag in wastewater was bound to particles and efficiently (>80%) removed by the treatment ...
Monomethylmercury (CH3Hg) and inorganic Mercury (HgII) concentrations were measured in the fluvia... more Monomethylmercury (CH3Hg) and inorganic Mercury (HgII) concentrations were measured in the fluvial part (Garonne Branch, March 2008-May 2009) and along the salinity gradient of the macrotidal and highly turbid Gironde Estuary, southwest France (6 cruises, Nov. 2005-Nov. 2007). Additional water samples were collected hourly at the entry and the exit of a major Wastewater Treatment Plant (WWTP) treating ~35% of the wastewater of Bordeaux (1 million inhabitants) during one day and on-board a vessel anchored at a fixed station on the Garonne Branch, close to the WWTP. Results showed an influence of the maximum turbidity zone and associated highsuspended particulate matter concentrations on CH3Hg concentrations. Dissolved CH3Hg concentrations in WWTP effluent showed an increase in CH3Hg/HgII ratios from 6% to 22% suggesting CH3Hg production during the treatment process. Assuming constant CH3Hg concentrations in WWTP effluent, wastewater CH3Hg fluxes into the Garonne Branch are up to 5% o...
Variations in soil texture have a direct effect on physical and chemical processes that take plac... more Variations in soil texture have a direct effect on physical and chemical processes that take place within soil. If there is a significant amount of variability, the classification of textural differences in the field needs to be made so that soil sampling and agricultural applications can take these inherent differences into account for improved effiency. The objective of this study was to produce an Electromagnetic induction (EMI) survey map of an integrated livestock-forage-cotton system and a continuous cotton monoculture system to determine field textural variations with relation to soil texture. The EMI survey gave an accurate and thorough description of field variability. Results were compared to randomly collected soil samples of each system. It was concluded that although there were slight variations in EMI data recorded in the field, it was not a result of textural differences.
This study is a part of the third axis of the « ETIAGE » project, a four year collaborat... more This study is a part of the third axis of the « ETIAGE » project, a four year collaboration (2010-2014) between the Lyonnaise des Eaux, the Communauté Urbaine de Bordeaux (CUB), AEAG, and FEDER, Aquitaine region with the University of Bordeaux, CNRS and IRSTEA. The axis 3 objectives were to document the trace metal inputs from the CUB watershed into the waters of the Garonne section of the Gironde estuary. The Gironde Estuary is one of the largest macrotidal and highly turbid estuaries in Western Europe characterized by the presence of a strong maximum turbidity zone (MTZ) with high suspended particulate matter (SPM) concentrations (>1 g.L-1 in surface water) transporting estuarine particles and potentially hazardous trace elements. This study has focused on the trace metal inputs from the two main wastewater treatment plants (WWTP) of the CUB. The objective of this research was therefore to study in detail the daily concentrations, fluxes, and dynamics of 8 EU priority contaminants Cr, Cu, Cr, Hg, Ni, Pb Zn, As, and the emerging contaminant Ag from the WWTPs in the CUB. The calculated removal rates are significant, around 80 % for the majority of metals, mainly as a result of the decantation phase. Despite this high removal efficiency, during periods of heavy rainstorms and low river discharges, the urban metal inputs via the WWTPs may still significantly increase metal concentrations and fluxes in the fluvial Gironde Estuary impacting water quality. In addition, the WWTP fluxes and concentrations of Ag exceeded common background concentrations in the Gironde fluvial estuary, making it an interesting urban tracer. The treatment within the WWTPs concentrates the trace metals in the sludge, yet, metal concentrations remained below legal norms for agricultural use. However, the analysis of WWTP sludge revealed that trace element concentrations are 15 (Ag) and 30 (Cu) times higher than natural background concentrations with high enrichment of Hg, Ag, Cr, Cu and Zn with over 70 % of Cd, Ag, Pb, Cu, and Zn being potentially bioavailable. Therefore, with increasing urban pressure on environmental quality, these results support the need for the development of efficient water quality monitoring tools.
Keywords : Coastal pollution, estuary metal contamination, urban trace elements, fluxes, wastewater, Gironde Estuary
Urban wastewater metal inputs into coastal systems are of increasing interest to both scientists ... more Urban wastewater metal inputs into coastal systems are of increasing interest to both scientists and managers
facing restrictive environmental protection policies, population increase and changing metal applications.
However, their impact and contribution to metal loads in estuarine and coastal environments iswidely unknown
due to the lack of (i)monitoring in both artificial and natural aquatic systems and (ii) an understanding of control
parameters, such as spatial and temporal variations in hydrological conditions.Weinvestigated the daily concentrations,
fluxes and dynamics of seven EU priority contaminants (potentially toxicmetals Cd, Cu, Cr,Ni, Pb, Zn and
the metalloid As) transported by the Garonne River (La Réole site; watershed area ~57,000 km2) to those
released into the freshwater reaches of the Gironde Estuary (Garonne Branch) by two main wastewater treatment
plants (WWTPs) of Bordeaux under lowriver discharge and contrasting rainfall situations. During short intense
summer rainstorms, wastewater flow into the WWTPs increased by up to 150% and 60%, respectively,
resulting in an increase of 70% (As) to 200% (Pb) for fluxes entering the treatment plants. Overall resulting
WWTP particulate and dissolved effluent concentrations were up to 2 (Cr), 3 (Pb, Cu and Ni) and 5 (Cd and
Zn) times higher than measured upstream in the Garonne River, respectively. During low-discharge, maximum
outlet fluxes at the WWTPs were similar to respective watershed-derived fluxes in the Garonne River. During
rain events, Pb in all fractions, total and dissolved Cu and total and particulate Zn fluxes entering the fluvial
estuarywere close to the respectiveminimumflux values at the La Réole site. Furthermore, during rain episodes,
particulate Cu and dissolved Zn fluxes fromtheWWTPs to the fluvial estuarywere greater than those transported
by the Garonne River at the La Réole site. Mixing of treated wastewater with highly turbid estuarine freshwater
most likely results in a re-equilibration between the dissolved and particulate phases, although biogeochemical
processes in downstream estuarine turbidity and salinity gradients may partly reverse contaminant adsorption
on estuarine particles. Accordingly, urban wastewater contaminant release clearly impacts estuarine water
quality before being expulsed to the Bay of Biscay.
High precision MC-ICP-MS Cu isotope measurements were performed on suspended particulate matter (... more High precision MC-ICP-MS Cu isotope measurements were performed on suspended particulate matter (SPM) and filtered water sampled along the turbidity gradient of the fluvial Gironde Estuary (Garonne Branch), following a summer lasting period of low freshwater discharge. High Cu concentrations (up to~200 μg/g) in particulate organic carbon (POC)-rich (up to~14%) particles upstream from the Maximum Turbidity Zone (MTZ) coincide with the most negative δ 65 Cu values (down to −0.39‰). This suggests the preferential uptake of light Cu isotopes by phytoplankton or anthropogenic contamination from CuSO 4 fungicides related to intensive wine farming in the area (δ 65 Cu = −0.37‰ for vineyard soils). Suspended particulate matter samples in the MTZ exhibit lower Cu concentrations (~35 μg/g) and heavier isotopic compositions (δ 65 Cu = −0.20‰ in average), as recorded by other samples from the Gironde Watershed. Along the fluvial estuary, dissolved Cu is mostly enriched in heavy isotopes (up to δ 65 Cu = + 0.21‰), but negative signatures down to δ 65 Cu = − 0.66‰ occur near the city of Bordeaux. Release of dissolved Cu was attributed to the mineralization of organic matter with a total addition of~600 ng/L in the fluvial estuary. Continuously decreasing amounts of dissolved Cu added with distance suggest that the observed Cu release evolved towards completion in the MTZ and contributed to negative values for dissolved Cu isotopes, as modeled by a Rayleigh process. Urban wastewater effluents probably also contribute to both (i) the dissolved Cu addition (10-20%) in the MTZ and (ii) negative Cu isotope signatures. Further work is necessary to assess the respective roles of anthropogenic sources and biogeochemical fractionation processes. Accordingly, the present study provides new insights into the potential of Cu isotopes for fingerprinting sources and mechanisms involved in the biogeochemical cycle of Cu in temperate aquatic environments impacted by anthropogenic activities.
Soil Organic Carbon (SOC) is an integral part of maintaining and measuring soil sustainabil... more Soil Organic Carbon (SOC) is an integral part of maintaining and measuring soil sustainability. This study was undertaken to document and better understand the effect of agro ecosystems on SOC. The methods used were to compare SOC content and 13C isotopes from the total soil and particulate organic matter fraction (POM) of two agro ecosystems. This research was conducted on the Texas High Plains, a semiarid region. The two systems included in the study were a continuous cotton (Gossypium hirsutum L.) monoculture system and cotton and beef cattle (Bos Taurus L.) grazing system. The cotton and beef cattle grazing system is comprised of 53.6% WW-B Dahl old world bluestem [Bothriochloa bladhii (Retz) S.T. Blake; OWB], a perennial warm-season grass and the other 46.4 % of the system is divided in two paddocks of equal size where no-till cotton is grown alternately with cereal rye (Secale cereal L.) and wheat (Triticum aestivum L.). With a livestock-crop rotation system that has varying cover crop residues from different forage species and input returns from the livestock, it becomes difficult to understand the main contributing factor to the increase or decrease of SOC sequestered within the system. Because C3 (trees, shrubs, and cool season grasses) and C4 plants (warm season grasses) have a specific isotopic ratio variation of δ13C (‰) in SOC, the δ-13C isotope ratios were used to trace the percentage of SOC to its source.
An investigation was made of both the total soil organic carbon (TSOC) and the particulate organic carbon (POC). The POC is the carbon found within the sand size fraction, also known as the particulate organic matter carbon (POM) and is comprised of partially decomposed organic matter. This fraction revealed dynamics regarding the more current management system. Warm season grasses produce about twice as much biomass as cool season grasses and it was hypothesized that the cropping system that integrated warm season grasses and livestock with cotton would return higher inputs of C to the soil and would have lower carbon turnover rates than a continuous cotton monoculture, thus improving soil sustainability.
The integrated livestock-crop system sequestered 30% more SOC than the continuous cotton monoculture system. The WW B-Dahl old world bluestem system component was the more significant contributor to higher carbon returns having 19.6 Mg ha-1 of SOC and sequestering 43% more soil organic carbon than the continuous cotton monoculture. The no-till cotton/ cereal rye/ wheat rotation (RCW/WFR) system component had 10 Mg ha-1 ±1 SOC and sequestered 16 ±3% more SOC than the conventionally-tilled cotton. The conventional tilled continuous cotton monoculture decreased soil sustainability and resulted in SOC loss on the surface with a vertical distribution of 1.1,1.4, and 1.5 Mg ha-1 at the 0-5, 5-10, and 10-20 cm depth, respectively, for the continuous cotton monoculture. There was an increase in POC with depth in the soil profile in the continuous cotton monoculture system. This suggests current management is effecting changes deeper in the soil plow layer for the continuous cotton monoculture than for the integrated system. Vertical distribution of POC within paddocks displayed a significant decrease in carbon 0-5 >5-10>10-20 cm for all paddocks except the conventional-till continuous cotton monoculture. POC for the 0-5, 5-10, 10-20 cm depth were 1.97, 0.53, and 0.23 Mg ha-1 cm-1 for OWB, 1.38, 0.42 and 0.27 Mg ha-1 cm-1 for RCW, 0.74, 0.33, and 0.16 Mg ha-1 cm-1 for the WFR and 0.26, 0.36, and 0.32 Mg ha-1 cm-1 for the continuous cotton monoculture. Carbon isotope signatures from soils sampled in 1997 at the initiation of the field experiment compared with soils sampled from 2007 showed that soil became less enriched with 13C in paddocks with C3 plant inputs. The 1997 δ13C values were ~-15.0‰ a result of C4 native grasses and more recent C4 plant inputs. Current soil δ13C values range from -21.1‰ to -16.1‰ and values decreased with depth for the integrated cotton-forage-livestock system and remained consistently less enriched in 13C isotopes throughout the 0-20 cm depth. The highest value (21.1 ‰) was found in the continuous cotton monoculture system demonstrating that it is having more of an effect on carbon turnover. The integrated cotton-forage-livestock system had an overall increase in SOC while retaining the carbon in the system from past land management practices and a decrease in C3/C4 carbon turnover. A system that increases SOC and also protects carbon that is already in the system may provide economic incentives for land managers if carbon credit systems are implemented. In addition, a system with slower carbon turnover rates sequesters more carbon if carbon inputs are higher than conventional monoculture systems.
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Papers by Victoria Nicole Deycard
Keywords : Coastal pollution, estuary metal contamination, urban trace elements, fluxes, wastewater, Gironde Estuary
facing restrictive environmental protection policies, population increase and changing metal applications.
However, their impact and contribution to metal loads in estuarine and coastal environments iswidely unknown
due to the lack of (i)monitoring in both artificial and natural aquatic systems and (ii) an understanding of control
parameters, such as spatial and temporal variations in hydrological conditions.Weinvestigated the daily concentrations,
fluxes and dynamics of seven EU priority contaminants (potentially toxicmetals Cd, Cu, Cr,Ni, Pb, Zn and
the metalloid As) transported by the Garonne River (La Réole site; watershed area ~57,000 km2) to those
released into the freshwater reaches of the Gironde Estuary (Garonne Branch) by two main wastewater treatment
plants (WWTPs) of Bordeaux under lowriver discharge and contrasting rainfall situations. During short intense
summer rainstorms, wastewater flow into the WWTPs increased by up to 150% and 60%, respectively,
resulting in an increase of 70% (As) to 200% (Pb) for fluxes entering the treatment plants. Overall resulting
WWTP particulate and dissolved effluent concentrations were up to 2 (Cr), 3 (Pb, Cu and Ni) and 5 (Cd and
Zn) times higher than measured upstream in the Garonne River, respectively. During low-discharge, maximum
outlet fluxes at the WWTPs were similar to respective watershed-derived fluxes in the Garonne River. During
rain events, Pb in all fractions, total and dissolved Cu and total and particulate Zn fluxes entering the fluvial
estuarywere close to the respectiveminimumflux values at the La Réole site. Furthermore, during rain episodes,
particulate Cu and dissolved Zn fluxes fromtheWWTPs to the fluvial estuarywere greater than those transported
by the Garonne River at the La Réole site. Mixing of treated wastewater with highly turbid estuarine freshwater
most likely results in a re-equilibration between the dissolved and particulate phases, although biogeochemical
processes in downstream estuarine turbidity and salinity gradients may partly reverse contaminant adsorption
on estuarine particles. Accordingly, urban wastewater contaminant release clearly impacts estuarine water
quality before being expulsed to the Bay of Biscay.
An investigation was made of both the total soil organic carbon (TSOC) and the particulate organic carbon (POC). The POC is the carbon found within the sand size fraction, also known as the particulate organic matter carbon (POM) and is comprised of partially decomposed organic matter. This fraction revealed dynamics regarding the more current management system. Warm season grasses produce about twice as much biomass as cool season grasses and it was hypothesized that the cropping system that integrated warm season grasses and livestock with cotton would return higher inputs of C to the soil and would have lower carbon turnover rates than a continuous cotton monoculture, thus improving soil sustainability.
The integrated livestock-crop system sequestered 30% more SOC than the continuous cotton monoculture system. The WW B-Dahl old world bluestem system component was the more significant contributor to higher carbon returns having 19.6 Mg ha-1 of SOC and sequestering 43% more soil organic carbon than the continuous cotton monoculture. The no-till cotton/ cereal rye/ wheat rotation (RCW/WFR) system component had 10 Mg ha-1 ±1 SOC and sequestered 16 ±3% more SOC than the conventionally-tilled cotton. The conventional tilled continuous cotton monoculture decreased soil sustainability and resulted in SOC loss on the surface with a vertical distribution of 1.1,1.4, and 1.5 Mg ha-1 at the 0-5, 5-10, and 10-20 cm depth, respectively, for the continuous cotton monoculture. There was an increase in POC with depth in the soil profile in the continuous cotton monoculture system. This suggests current management is effecting changes deeper in the soil plow layer for the continuous cotton monoculture than for the integrated system. Vertical distribution of POC within paddocks displayed a significant decrease in carbon 0-5 >5-10>10-20 cm for all paddocks except the conventional-till continuous cotton monoculture. POC for the 0-5, 5-10, 10-20 cm depth were 1.97, 0.53, and 0.23 Mg ha-1 cm-1 for OWB, 1.38, 0.42 and 0.27 Mg ha-1 cm-1 for RCW, 0.74, 0.33, and 0.16 Mg ha-1 cm-1 for the WFR and 0.26, 0.36, and 0.32 Mg ha-1 cm-1 for the continuous cotton monoculture. Carbon isotope signatures from soils sampled in 1997 at the initiation of the field experiment compared with soils sampled from 2007 showed that soil became less enriched with 13C in paddocks with C3 plant inputs. The 1997 δ13C values were ~-15.0‰ a result of C4 native grasses and more recent C4 plant inputs. Current soil δ13C values range from -21.1‰ to -16.1‰ and values decreased with depth for the integrated cotton-forage-livestock system and remained consistently less enriched in 13C isotopes throughout the 0-20 cm depth. The highest value (21.1 ‰) was found in the continuous cotton monoculture system demonstrating that it is having more of an effect on carbon turnover. The integrated cotton-forage-livestock system had an overall increase in SOC while retaining the carbon in the system from past land management practices and a decrease in C3/C4 carbon turnover. A system that increases SOC and also protects carbon that is already in the system may provide economic incentives for land managers if carbon credit systems are implemented. In addition, a system with slower carbon turnover rates sequesters more carbon if carbon inputs are higher than conventional monoculture systems.
Keywords : Coastal pollution, estuary metal contamination, urban trace elements, fluxes, wastewater, Gironde Estuary
facing restrictive environmental protection policies, population increase and changing metal applications.
However, their impact and contribution to metal loads in estuarine and coastal environments iswidely unknown
due to the lack of (i)monitoring in both artificial and natural aquatic systems and (ii) an understanding of control
parameters, such as spatial and temporal variations in hydrological conditions.Weinvestigated the daily concentrations,
fluxes and dynamics of seven EU priority contaminants (potentially toxicmetals Cd, Cu, Cr,Ni, Pb, Zn and
the metalloid As) transported by the Garonne River (La Réole site; watershed area ~57,000 km2) to those
released into the freshwater reaches of the Gironde Estuary (Garonne Branch) by two main wastewater treatment
plants (WWTPs) of Bordeaux under lowriver discharge and contrasting rainfall situations. During short intense
summer rainstorms, wastewater flow into the WWTPs increased by up to 150% and 60%, respectively,
resulting in an increase of 70% (As) to 200% (Pb) for fluxes entering the treatment plants. Overall resulting
WWTP particulate and dissolved effluent concentrations were up to 2 (Cr), 3 (Pb, Cu and Ni) and 5 (Cd and
Zn) times higher than measured upstream in the Garonne River, respectively. During low-discharge, maximum
outlet fluxes at the WWTPs were similar to respective watershed-derived fluxes in the Garonne River. During
rain events, Pb in all fractions, total and dissolved Cu and total and particulate Zn fluxes entering the fluvial
estuarywere close to the respectiveminimumflux values at the La Réole site. Furthermore, during rain episodes,
particulate Cu and dissolved Zn fluxes fromtheWWTPs to the fluvial estuarywere greater than those transported
by the Garonne River at the La Réole site. Mixing of treated wastewater with highly turbid estuarine freshwater
most likely results in a re-equilibration between the dissolved and particulate phases, although biogeochemical
processes in downstream estuarine turbidity and salinity gradients may partly reverse contaminant adsorption
on estuarine particles. Accordingly, urban wastewater contaminant release clearly impacts estuarine water
quality before being expulsed to the Bay of Biscay.
An investigation was made of both the total soil organic carbon (TSOC) and the particulate organic carbon (POC). The POC is the carbon found within the sand size fraction, also known as the particulate organic matter carbon (POM) and is comprised of partially decomposed organic matter. This fraction revealed dynamics regarding the more current management system. Warm season grasses produce about twice as much biomass as cool season grasses and it was hypothesized that the cropping system that integrated warm season grasses and livestock with cotton would return higher inputs of C to the soil and would have lower carbon turnover rates than a continuous cotton monoculture, thus improving soil sustainability.
The integrated livestock-crop system sequestered 30% more SOC than the continuous cotton monoculture system. The WW B-Dahl old world bluestem system component was the more significant contributor to higher carbon returns having 19.6 Mg ha-1 of SOC and sequestering 43% more soil organic carbon than the continuous cotton monoculture. The no-till cotton/ cereal rye/ wheat rotation (RCW/WFR) system component had 10 Mg ha-1 ±1 SOC and sequestered 16 ±3% more SOC than the conventionally-tilled cotton. The conventional tilled continuous cotton monoculture decreased soil sustainability and resulted in SOC loss on the surface with a vertical distribution of 1.1,1.4, and 1.5 Mg ha-1 at the 0-5, 5-10, and 10-20 cm depth, respectively, for the continuous cotton monoculture. There was an increase in POC with depth in the soil profile in the continuous cotton monoculture system. This suggests current management is effecting changes deeper in the soil plow layer for the continuous cotton monoculture than for the integrated system. Vertical distribution of POC within paddocks displayed a significant decrease in carbon 0-5 >5-10>10-20 cm for all paddocks except the conventional-till continuous cotton monoculture. POC for the 0-5, 5-10, 10-20 cm depth were 1.97, 0.53, and 0.23 Mg ha-1 cm-1 for OWB, 1.38, 0.42 and 0.27 Mg ha-1 cm-1 for RCW, 0.74, 0.33, and 0.16 Mg ha-1 cm-1 for the WFR and 0.26, 0.36, and 0.32 Mg ha-1 cm-1 for the continuous cotton monoculture. Carbon isotope signatures from soils sampled in 1997 at the initiation of the field experiment compared with soils sampled from 2007 showed that soil became less enriched with 13C in paddocks with C3 plant inputs. The 1997 δ13C values were ~-15.0‰ a result of C4 native grasses and more recent C4 plant inputs. Current soil δ13C values range from -21.1‰ to -16.1‰ and values decreased with depth for the integrated cotton-forage-livestock system and remained consistently less enriched in 13C isotopes throughout the 0-20 cm depth. The highest value (21.1 ‰) was found in the continuous cotton monoculture system demonstrating that it is having more of an effect on carbon turnover. The integrated cotton-forage-livestock system had an overall increase in SOC while retaining the carbon in the system from past land management practices and a decrease in C3/C4 carbon turnover. A system that increases SOC and also protects carbon that is already in the system may provide economic incentives for land managers if carbon credit systems are implemented. In addition, a system with slower carbon turnover rates sequesters more carbon if carbon inputs are higher than conventional monoculture systems.