José Macias Zamora | Universidad Autonoma de Baja California (original) (raw)
Papers by José Macias Zamora
Estuarine, Coastal and Shelf Science, 2014
We measured dissolved methane concentrations ([CH4]) in the coastal zone of the Southern Californ... more We measured dissolved methane concentrations ([CH4]) in the coastal zone of the Southern California Bight-Mexican sector (SCBMex) during two cruises: S1 in the USA–Mexico Border Area (BA) during a short rainstorm and S2 in the entire SCBMex during a drier period a few days later. High spatial variability in surface mixed layer (ML) [CH4] was observed, ranging from 2.2 nmol L−1 to 17.8 nmol L−1. ML-[CH4] was supersaturated at all BA stations during both cruises. The highest [CH4] was 72.4 nmol L−1 (2819 % supersaturated) measured at 10 m depth during S2, about 3 km southwest of the discharge point of the South Bay Ocean Outfall (SBOO). Our results show an apparent connection between wastewater treatment discharges and [CH4]. Application of a sewer CH4 production model suggests that the SBOO may be a large source of CH4 to the BA and points to the need to consider point sources in developing coastal marine CH4 budgets for highly populated areas. Based on our data, the SCBMex appears to be a relatively strong source of CH4 to the atmosphere compared to other Pacific Basin areas. The average BA sea-to-air CH4 flux (F) during S1 was (15.5 ± 8.6) × 10−2 nmol m−2 s−1, about 1.5 times higher than F during S2, which had a flux of (9.5 ± 6.9) × 10−2 nmol m−2 s−1 mainly due to the higher wind speed during S1.
Hidrobiologica, 1996
The levels of concentration and distribution patterns of aliphatic (n-hydrocarbons) and polycycli... more The levels of concentration and distribution patterns of aliphatic (n-hydrocarbons) and polycyclic aromatic hydrocarbons (or PAH's) were determined in 16 samples of recent marine sediments of Bahia de Todos Santos, Baja California. The purpose was to stablish base line data as a future reference. We report here on our findings. The extraction was carried out by means of a solid phase extraction procedure reported by Burrows (1983) both for cleaning and separation of fractions of compounds. For identification and quantification of compounds we used capillary gas chromatography with FID detection for both fmilies of molecules. The concentrations found within the Bay were relatively small and homogeneous (from 0.1 to 2.6 mg g1). Cluster analysis suggests three significantly different zones. The indexes used for source identification of hydrocarbons are presented and discussed. Possible origins for these materials are discussed. Similarly, possible explanations are offered on the fl...
Con el objeto de establecer los niveles base actuales de compuestos aromaticos polinucleares (PAH... more Con el objeto de establecer los niveles base actuales de compuestos aromaticos polinucleares (PAH's) y alifaticos, se determino la concentracion y distribucion de tales compuestos en 16 muestras superficiales de sedimentos de ia Bahia de Todos Santos, B.C. Se reportan los niveles encontrados. Se utilizo la tecnica de extraccion en fase solida (Burrows, 1983) para limpieza y separacion por fracciones. La identificacion y cuantificacion de ambas familias de compuestos se efectuo por medio de cromatografia de gases con columna capilar y con deteccion por ionizacion en flama. Las concentraciones encontradas fueron relativamente pequenas y homogeneas dentro de la bahia (de 0.1 a 2.6 mg g-1). Se efectuo un analisis de grupos que sugiere tres zonas significativamente distintas. Se incluyen indices y se discuten posibles origenes de estos grupos de hidrocarburos, asi como los flujos que sugieren los gradientes de concentracion de estos materiales en la bahia. Se concluye que la bahia pu...
An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in... more An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in August 1998 at 37 stations along the northwest coast of Baja California (NCBC). Mercury was analyzed by cold-vapour atomic absorption spectrophotometry. The percentages of mud (<63 μm) and organic matter were also measured. Mercury concentrations showed a homogeneous spatial distribution in the study area. The mean concentration of Hg (58.2 ng g –1 ) was similar to that found in the Southern California Bight. Mercury enrichment was observed at four stations located in the northern and central zones of the study area. In general, the Hg concentrations (30.4–96.5 ng g –1 ) were relatively low and pose no environmental concerns according to North American marine sediment quality guidelines. No correlations were found between Hg and mud or organic matter, suggesting that these variables do not influence the concentration and spatial distribution of this element in sediments from NCBC.
Journal of the Mexican Chemical Society, 2018
An alternative to remove polycyclic aromatic hydrocarbons (PAHs) of the environment is using hydr... more An alternative to remove polycyclic aromatic hydrocarbons (PAHs) of the environment is using hydrocarbonoclastic bacteria. The aim of this work was to study the bacterial diversity of indigenous isolates with potential to degrade pyrene. We used MALDI-Biotyper (Bruker Daltonics) as a powerful analytical tool for identification. Bacteria were isolated from surface seawater and marine sediments samples of three sites from the coast of Rosarito Port, B.C., Mexico. Total concentration of PAHs in collected samples was quantified by GC-MS, showed values ranged 0.461-0.525 ng mL-1 and of 74 -266 ng g-1 in seawater and sediments samples, respectively. A total of 52 bacteria with capacity to grow in 25 mg L-1 pyrene as sole carbon and energy source were taxonomically identified and classified by MALDI-Biotyper system by comparing the mass spectra with library and/or to use chemometric tools as Principal Components Analysis (PCA) and Composite Correlation Index (CCI) to evaluate possible diff...
Ciencias Marinas, 1997
During September and October 1995, samples of surface sediments and water were collected to deve... more During September and October 1995, samples of surface sediments and water were collected to develop an analytical set-up to determine the concentrations of the organic compounds known as tributyltins (TBTs), including tributyl-, dibutyl- and monobutyltin. The method was then used to measure the levels of these contaminants in the port of Ensenada, Baja California. The method is based on hydride generation with atomic absorption detection. The concentrations determined were found to be relatively high (33 to 1021 ng g–1 of Sn in sediments and 66 to 469 ng L–1 in water samples), when compared to those obtained in similar works at San Diego Bay in California, USA. Comparisons are also made with other geographical locations. These results suggest that the port of Ensenada is an area that is receiving substantial amounts of these chemicals and might already be affecting the health of local biota. Two sources of these chemicals were identified: the activities associated with painting and...
Ciencias Marinas, 2007
An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in... more An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in August 1998 at 37 stations along the northwest coast of Baja California (NCBC). Mercury was analyzed by cold-vapour atomic absorption spectrophotometry. The percentages of mud ( < 63 µm) and organic matter were also measured. Mercury concentrations showed a homogeneous spatial distribution in the study area. The mean concentration of Hg (58.2 ng g–1) was similar to that found in the Southern California Bight. Mercury enrichment was observed at four stations located in the northern and central zones of the study area. In general, the Hg concentrations (30.4–96.5 ng g–1) were relatively low and pose no environmental concerns according to North American marine sediment quality guidelines. No correlations were found between Hg and mud or organic matter, suggesting that these variables do not influence the concentration and spatial distribution of this element in sediments from NCBC.
Science of The Total Environment, 2016
Polybrominated diphenyl ethers (PBDEs) are widely distributed compounds in all types of matrices.... more Polybrominated diphenyl ethers (PBDEs) are widely distributed compounds in all types of matrices. In the northern portion of the Southern California Bight (SCB), there were reports of some of the largest PBDE concentrations in marine mammals and mussels. Because of this, we decided to analyze the status of PBDEs in the southern part of the SCB. An analysis of 91 samples of marine surface sediment was carried out. All of the 91 samples contained measurable amounts of PBDEs, which is a manifestation of the widespread distribution of these chemical substances. However, the levels detected are between one and two orders of magnitude smaller than those reported in southern California. Currents appear to control the distribution of PBDEs along the coast and the sedimentation sites with largest concentrations are favored by local bathymetry. Maximum concentrations were located in the middle and deeper platforms ranging from 0.02 to 5.90 (with a median 0.71) ng·g(-1) d.w. Deca-BDE mixture is largely predominant in the sediments followed by the penta-BDE mixture. The mass balance for the latitudinal strata shows the largest concentrations in the north where the largest population centers are present and with a very clear southward gradient. The mass balance calculation values showed about 36kg of PBDEs for the north, 22kg for the center, and 10kg for the south strata. In terms of depth, the PBDEs are mainly located on the middle and deep platforms rather than near point discharges, which is different than that reported by other authors.
Ciencias Marinas, 2013
An unusual combination of features makes the Midriff Islands region of the northern Gulf of Calif... more An unusual combination of features makes the Midriff Islands region of the northern Gulf of California (NGC) a strong atmospheric methane source. Oceanographic isolation by a series of sills and islands along with upward transport of nutrient-rich water enhanced by tidal currents, upwelling, and overflows results in high productivity. The resulting high phytoplankton biomass likely stimulates biogeochemical cycling that, in turn, may stimulate biological methane production in the water column and sediments. Additionally, venting of abiogenic methane-rich hydrothermal fluids in this tectonically active area and seepage of biogenic or thermogenic methane gas from the sediments may also be important sources. We found elevated methane concentrations throughout our study area, the highest within the Ballenas Channel, which was supersaturated with respect to atmospheric methane at all depths. Our vertical methane profiles show that elevated dissolved methane concentrations in the NGC are ...
Environmental Pollution, 1999
Trace metals in sediment cores from the Gulf of Mexico, in the Campeche shelf area were studied t... more Trace metals in sediment cores from the Gulf of Mexico, in the Campeche shelf area were studied to investigate possible variations in their vertical and/or horizontal sedimentary distributions. Possible links to petroleum sources were investigated as this area contains very productive oil explotation and transportation activities. Sediments were collected undisturbed using a vegematic type box corer. The upper 10 cm. were collected and cut in sections of 2 cm each. Incomplete, open vessel sediment digestion and atomic absorption was used for trace element determination. Particular interest was placed on vanadium and nickel concentrations as they have been associated to oil. Several metals were measured and representative distributions are presented. Horizontal distributions appear to conform to predominant current circulation patterns reported and closeness to sources of sedimentary materials. Vertical distributions are discussed. The vertical distributions were strikingly constant. Correlation among metals are also presented. Fe was used as a normalizing agent and the carbonate content was acting as a diluter of total trace metal content.
Environmental Monitoring and Assessment, 2013
In many coastal countries, oil spill contingency plans include several alternatives for removal o... more In many coastal countries, oil spill contingency plans include several alternatives for removal of the spilled oil from the ocean. Frequently, these plans include dispersants. Because this process applies chemical substances that may add toxicity to oil that already contains toxic compounds, it is, at times, a controversial method to fight oil pollution. Additionally, local conditions may result in particular complications. We investigated the possible effects of the dispersant Corexit 9500© under conditions similar to those of subtropical oceans. We used fuel oil #6+ diesel as the test mixture. Under certain conditions, at least part of the dispersed oil may reach the sediment, particularly if the dispersant is applied in coastal waters. Nine experimental units were used in this experiment. Similar conditions of water temperature, salinity, air fluxes into the experimental units, and hydrocarbon concentrations in sediments were used. Two treatments and one control, each one with three replicates, were carried out. We concentrated our investigation on sediment, although measurements of water were also taken. Our results suggest that once the oil has penetrated the sediment, no significant differences exist between oil that contains dispersant and oil without dispersant. Noticeable degradation of aliphatic hydrocarbons occurred mainly in the low molecular weight aliphatic hydrocarbons and not in the others. Apparently, degradation of aromatics was easier than that of alkanes. However, some differences were noticed for the degradation of PAHs in the sediment, suggesting a faster degradation under particular conditions in aerobic environments such as under this experiment.
Zoosymposia
The aim of this study was to describe and analyze the structure, distribution, and temporal varia... more The aim of this study was to describe and analyze the structure, distribution, and temporal variation in the composition of benthic polychaeta and their relation to abiotic characteristics in marine sediments along the continental shelf of Bahia de Todos Santos, Baja California, Mexico. Benthic macrofauna and environmental variables were collected to coordinated with a long-term ocean monitoring project known as the Southern California Bight Regional Monitoring Program. A total of nineteen stations were collected in September 1998, twenty stations in November 2003, fifteen stations in December 2013 and sixteen stations in September 2018. These data were compared to assess the response of benthic polychaete assemblages to natural and human induced changes in sediment characteristics. All stations were sampled using a Van Veen grab (0.1 m2) at depths between 15 to 206 m. Sites were selected using a multiple density nested random-tessellation stratified design. Environmental parameters...
Ciencias …, 2003
En enero de 1998, se colectaron 4 núcleos de sedimentos para reconstruir la historia de la contam... more En enero de 1998, se colectaron 4 núcleos de sedimentos para reconstruir la historia de la contaminación por compuestos orgánicos persistentes (COPs) en la región sur de la Cuenca de las Californias. Se determinaron 2 grupos de compuestos por métodos cromatográficos, los hidrocarburos del petróleo (hidrocarburos alifáticos e hidrocarburos aromáticos polinucleares) y los hidrocarburos clorados (pesticidas y bifenilos policlorados). Los hidrocarburos alifáticos (HA's) presentaron bajas concentraciones de 0.30 a 3.38 µg g-1 y mostraron un origen alóctono biogénico. Las concentraciones de hidrocarburos aromáticos polinucleares (HAP's) fluctuaron entre 0.99 y 673 ng g-1. La distribución de los homólogos de alquilo y los índices compuestos mostraron una clara dominancia de HAP's de origen petrogénico. Los hidrocarburos clorados presentaron un máximo superficial y un decremento con la profundidad hasta niveles no detectables. Las concentraciones de bifenilos policlorados (BPC's) estuvieron comprendidas entre 0.18 y 7.15 ng g-1 y para pesticidas entre 0.09 y 19.71 ng g-1. Los pesticidas más frecuentemente encontrados fueron el p,p'-DDT y sus metabolitos (p,p'-DDE y p,p'-DDD). Otros pesticidas detectados fueron el γ-clordano e isómeros del BHC (α y γ). La estratigrafía de los núcleos fue realizada por marcadores moleculares (hidrocarburos clorados), y a partir de éstos se calculó una tasa de sedimentación entre 0.17 y 0.55 cm año-1 .
Archives of Environmental Contamination and Toxicology, 2008
Estuarine, Coastal and Shelf Science, 2014
We measured dissolved methane concentrations ([CH4]) in the coastal zone of the Southern Californ... more We measured dissolved methane concentrations ([CH4]) in the coastal zone of the Southern California Bight-Mexican sector (SCBMex) during two cruises: S1 in the USA–Mexico Border Area (BA) during a short rainstorm and S2 in the entire SCBMex during a drier period a few days later. High spatial variability in surface mixed layer (ML) [CH4] was observed, ranging from 2.2 nmol L−1 to 17.8 nmol L−1. ML-[CH4] was supersaturated at all BA stations during both cruises. The highest [CH4] was 72.4 nmol L−1 (2819 % supersaturated) measured at 10 m depth during S2, about 3 km southwest of the discharge point of the South Bay Ocean Outfall (SBOO). Our results show an apparent connection between wastewater treatment discharges and [CH4]. Application of a sewer CH4 production model suggests that the SBOO may be a large source of CH4 to the BA and points to the need to consider point sources in developing coastal marine CH4 budgets for highly populated areas. Based on our data, the SCBMex appears to be a relatively strong source of CH4 to the atmosphere compared to other Pacific Basin areas. The average BA sea-to-air CH4 flux (F) during S1 was (15.5 ± 8.6) × 10−2 nmol m−2 s−1, about 1.5 times higher than F during S2, which had a flux of (9.5 ± 6.9) × 10−2 nmol m−2 s−1 mainly due to the higher wind speed during S1.
Hidrobiologica, 1996
The levels of concentration and distribution patterns of aliphatic (n-hydrocarbons) and polycycli... more The levels of concentration and distribution patterns of aliphatic (n-hydrocarbons) and polycyclic aromatic hydrocarbons (or PAH's) were determined in 16 samples of recent marine sediments of Bahia de Todos Santos, Baja California. The purpose was to stablish base line data as a future reference. We report here on our findings. The extraction was carried out by means of a solid phase extraction procedure reported by Burrows (1983) both for cleaning and separation of fractions of compounds. For identification and quantification of compounds we used capillary gas chromatography with FID detection for both fmilies of molecules. The concentrations found within the Bay were relatively small and homogeneous (from 0.1 to 2.6 mg g1). Cluster analysis suggests three significantly different zones. The indexes used for source identification of hydrocarbons are presented and discussed. Possible origins for these materials are discussed. Similarly, possible explanations are offered on the fl...
Con el objeto de establecer los niveles base actuales de compuestos aromaticos polinucleares (PAH... more Con el objeto de establecer los niveles base actuales de compuestos aromaticos polinucleares (PAH's) y alifaticos, se determino la concentracion y distribucion de tales compuestos en 16 muestras superficiales de sedimentos de ia Bahia de Todos Santos, B.C. Se reportan los niveles encontrados. Se utilizo la tecnica de extraccion en fase solida (Burrows, 1983) para limpieza y separacion por fracciones. La identificacion y cuantificacion de ambas familias de compuestos se efectuo por medio de cromatografia de gases con columna capilar y con deteccion por ionizacion en flama. Las concentraciones encontradas fueron relativamente pequenas y homogeneas dentro de la bahia (de 0.1 a 2.6 mg g-1). Se efectuo un analisis de grupos que sugiere tres zonas significativamente distintas. Se incluyen indices y se discuten posibles origenes de estos grupos de hidrocarburos, asi como los flujos que sugieren los gradientes de concentracion de estos materiales en la bahia. Se concluye que la bahia pu...
An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in... more An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in August 1998 at 37 stations along the northwest coast of Baja California (NCBC). Mercury was analyzed by cold-vapour atomic absorption spectrophotometry. The percentages of mud (<63 μm) and organic matter were also measured. Mercury concentrations showed a homogeneous spatial distribution in the study area. The mean concentration of Hg (58.2 ng g –1 ) was similar to that found in the Southern California Bight. Mercury enrichment was observed at four stations located in the northern and central zones of the study area. In general, the Hg concentrations (30.4–96.5 ng g –1 ) were relatively low and pose no environmental concerns according to North American marine sediment quality guidelines. No correlations were found between Hg and mud or organic matter, suggesting that these variables do not influence the concentration and spatial distribution of this element in sediments from NCBC.
Journal of the Mexican Chemical Society, 2018
An alternative to remove polycyclic aromatic hydrocarbons (PAHs) of the environment is using hydr... more An alternative to remove polycyclic aromatic hydrocarbons (PAHs) of the environment is using hydrocarbonoclastic bacteria. The aim of this work was to study the bacterial diversity of indigenous isolates with potential to degrade pyrene. We used MALDI-Biotyper (Bruker Daltonics) as a powerful analytical tool for identification. Bacteria were isolated from surface seawater and marine sediments samples of three sites from the coast of Rosarito Port, B.C., Mexico. Total concentration of PAHs in collected samples was quantified by GC-MS, showed values ranged 0.461-0.525 ng mL-1 and of 74 -266 ng g-1 in seawater and sediments samples, respectively. A total of 52 bacteria with capacity to grow in 25 mg L-1 pyrene as sole carbon and energy source were taxonomically identified and classified by MALDI-Biotyper system by comparing the mass spectra with library and/or to use chemometric tools as Principal Components Analysis (PCA) and Composite Correlation Index (CCI) to evaluate possible diff...
Ciencias Marinas, 1997
During September and October 1995, samples of surface sediments and water were collected to deve... more During September and October 1995, samples of surface sediments and water were collected to develop an analytical set-up to determine the concentrations of the organic compounds known as tributyltins (TBTs), including tributyl-, dibutyl- and monobutyltin. The method was then used to measure the levels of these contaminants in the port of Ensenada, Baja California. The method is based on hydride generation with atomic absorption detection. The concentrations determined were found to be relatively high (33 to 1021 ng g–1 of Sn in sediments and 66 to 469 ng L–1 in water samples), when compared to those obtained in similar works at San Diego Bay in California, USA. Comparisons are also made with other geographical locations. These results suggest that the port of Ensenada is an area that is receiving substantial amounts of these chemicals and might already be affecting the health of local biota. Two sources of these chemicals were identified: the activities associated with painting and...
Ciencias Marinas, 2007
An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in... more An evaluation was made of the distribution and enrichment of Hg in surface sediments collected in August 1998 at 37 stations along the northwest coast of Baja California (NCBC). Mercury was analyzed by cold-vapour atomic absorption spectrophotometry. The percentages of mud ( < 63 µm) and organic matter were also measured. Mercury concentrations showed a homogeneous spatial distribution in the study area. The mean concentration of Hg (58.2 ng g–1) was similar to that found in the Southern California Bight. Mercury enrichment was observed at four stations located in the northern and central zones of the study area. In general, the Hg concentrations (30.4–96.5 ng g–1) were relatively low and pose no environmental concerns according to North American marine sediment quality guidelines. No correlations were found between Hg and mud or organic matter, suggesting that these variables do not influence the concentration and spatial distribution of this element in sediments from NCBC.
Science of The Total Environment, 2016
Polybrominated diphenyl ethers (PBDEs) are widely distributed compounds in all types of matrices.... more Polybrominated diphenyl ethers (PBDEs) are widely distributed compounds in all types of matrices. In the northern portion of the Southern California Bight (SCB), there were reports of some of the largest PBDE concentrations in marine mammals and mussels. Because of this, we decided to analyze the status of PBDEs in the southern part of the SCB. An analysis of 91 samples of marine surface sediment was carried out. All of the 91 samples contained measurable amounts of PBDEs, which is a manifestation of the widespread distribution of these chemical substances. However, the levels detected are between one and two orders of magnitude smaller than those reported in southern California. Currents appear to control the distribution of PBDEs along the coast and the sedimentation sites with largest concentrations are favored by local bathymetry. Maximum concentrations were located in the middle and deeper platforms ranging from 0.02 to 5.90 (with a median 0.71) ng·g(-1) d.w. Deca-BDE mixture is largely predominant in the sediments followed by the penta-BDE mixture. The mass balance for the latitudinal strata shows the largest concentrations in the north where the largest population centers are present and with a very clear southward gradient. The mass balance calculation values showed about 36kg of PBDEs for the north, 22kg for the center, and 10kg for the south strata. In terms of depth, the PBDEs are mainly located on the middle and deep platforms rather than near point discharges, which is different than that reported by other authors.
Ciencias Marinas, 2013
An unusual combination of features makes the Midriff Islands region of the northern Gulf of Calif... more An unusual combination of features makes the Midriff Islands region of the northern Gulf of California (NGC) a strong atmospheric methane source. Oceanographic isolation by a series of sills and islands along with upward transport of nutrient-rich water enhanced by tidal currents, upwelling, and overflows results in high productivity. The resulting high phytoplankton biomass likely stimulates biogeochemical cycling that, in turn, may stimulate biological methane production in the water column and sediments. Additionally, venting of abiogenic methane-rich hydrothermal fluids in this tectonically active area and seepage of biogenic or thermogenic methane gas from the sediments may also be important sources. We found elevated methane concentrations throughout our study area, the highest within the Ballenas Channel, which was supersaturated with respect to atmospheric methane at all depths. Our vertical methane profiles show that elevated dissolved methane concentrations in the NGC are ...
Environmental Pollution, 1999
Trace metals in sediment cores from the Gulf of Mexico, in the Campeche shelf area were studied t... more Trace metals in sediment cores from the Gulf of Mexico, in the Campeche shelf area were studied to investigate possible variations in their vertical and/or horizontal sedimentary distributions. Possible links to petroleum sources were investigated as this area contains very productive oil explotation and transportation activities. Sediments were collected undisturbed using a vegematic type box corer. The upper 10 cm. were collected and cut in sections of 2 cm each. Incomplete, open vessel sediment digestion and atomic absorption was used for trace element determination. Particular interest was placed on vanadium and nickel concentrations as they have been associated to oil. Several metals were measured and representative distributions are presented. Horizontal distributions appear to conform to predominant current circulation patterns reported and closeness to sources of sedimentary materials. Vertical distributions are discussed. The vertical distributions were strikingly constant. Correlation among metals are also presented. Fe was used as a normalizing agent and the carbonate content was acting as a diluter of total trace metal content.
Environmental Monitoring and Assessment, 2013
In many coastal countries, oil spill contingency plans include several alternatives for removal o... more In many coastal countries, oil spill contingency plans include several alternatives for removal of the spilled oil from the ocean. Frequently, these plans include dispersants. Because this process applies chemical substances that may add toxicity to oil that already contains toxic compounds, it is, at times, a controversial method to fight oil pollution. Additionally, local conditions may result in particular complications. We investigated the possible effects of the dispersant Corexit 9500© under conditions similar to those of subtropical oceans. We used fuel oil #6+ diesel as the test mixture. Under certain conditions, at least part of the dispersed oil may reach the sediment, particularly if the dispersant is applied in coastal waters. Nine experimental units were used in this experiment. Similar conditions of water temperature, salinity, air fluxes into the experimental units, and hydrocarbon concentrations in sediments were used. Two treatments and one control, each one with three replicates, were carried out. We concentrated our investigation on sediment, although measurements of water were also taken. Our results suggest that once the oil has penetrated the sediment, no significant differences exist between oil that contains dispersant and oil without dispersant. Noticeable degradation of aliphatic hydrocarbons occurred mainly in the low molecular weight aliphatic hydrocarbons and not in the others. Apparently, degradation of aromatics was easier than that of alkanes. However, some differences were noticed for the degradation of PAHs in the sediment, suggesting a faster degradation under particular conditions in aerobic environments such as under this experiment.
Zoosymposia
The aim of this study was to describe and analyze the structure, distribution, and temporal varia... more The aim of this study was to describe and analyze the structure, distribution, and temporal variation in the composition of benthic polychaeta and their relation to abiotic characteristics in marine sediments along the continental shelf of Bahia de Todos Santos, Baja California, Mexico. Benthic macrofauna and environmental variables were collected to coordinated with a long-term ocean monitoring project known as the Southern California Bight Regional Monitoring Program. A total of nineteen stations were collected in September 1998, twenty stations in November 2003, fifteen stations in December 2013 and sixteen stations in September 2018. These data were compared to assess the response of benthic polychaete assemblages to natural and human induced changes in sediment characteristics. All stations were sampled using a Van Veen grab (0.1 m2) at depths between 15 to 206 m. Sites were selected using a multiple density nested random-tessellation stratified design. Environmental parameters...
Ciencias …, 2003
En enero de 1998, se colectaron 4 núcleos de sedimentos para reconstruir la historia de la contam... more En enero de 1998, se colectaron 4 núcleos de sedimentos para reconstruir la historia de la contaminación por compuestos orgánicos persistentes (COPs) en la región sur de la Cuenca de las Californias. Se determinaron 2 grupos de compuestos por métodos cromatográficos, los hidrocarburos del petróleo (hidrocarburos alifáticos e hidrocarburos aromáticos polinucleares) y los hidrocarburos clorados (pesticidas y bifenilos policlorados). Los hidrocarburos alifáticos (HA's) presentaron bajas concentraciones de 0.30 a 3.38 µg g-1 y mostraron un origen alóctono biogénico. Las concentraciones de hidrocarburos aromáticos polinucleares (HAP's) fluctuaron entre 0.99 y 673 ng g-1. La distribución de los homólogos de alquilo y los índices compuestos mostraron una clara dominancia de HAP's de origen petrogénico. Los hidrocarburos clorados presentaron un máximo superficial y un decremento con la profundidad hasta niveles no detectables. Las concentraciones de bifenilos policlorados (BPC's) estuvieron comprendidas entre 0.18 y 7.15 ng g-1 y para pesticidas entre 0.09 y 19.71 ng g-1. Los pesticidas más frecuentemente encontrados fueron el p,p'-DDT y sus metabolitos (p,p'-DDE y p,p'-DDD). Otros pesticidas detectados fueron el γ-clordano e isómeros del BHC (α y γ). La estratigrafía de los núcleos fue realizada por marcadores moleculares (hidrocarburos clorados), y a partir de éstos se calculó una tasa de sedimentación entre 0.17 y 0.55 cm año-1 .
Archives of Environmental Contamination and Toxicology, 2008