José Vinicio Macías-Zamora

PAHs composition of surface marine sediments: a comparison to potential local sources in Todos Santos Bay, B.C., Mexico

The analysis of the 16 polyaromatic hydrocarbons (PAHs) listed as priority pollutants by EPA, was carried out on surface sediments at 32 stations at Todos Santos Bay, Baja California, Mexico. The purpose was to investigate concentration levels, distribution patterns and relate them to three suspected local sources. The PAHs composition of car exhaust, grass and shrubs combustion, and asphalt and tire dust, were all compared to the relative abundance of PAHs signature found on marine sediments of the bay. We used GC-MS analysis in selected ion monitoring (SIM) mode. The total concentration found was low (from 7.6 to 813 ng/g of dry sediment. The average concentration was 96 ng/g). PAHs concentration was somewhat correlated (r = 0.612; P < 0.05) with organic matter content. Surface distributions suggest depositional patterns conforming to the reported water circulation in the bay. The maximum concentration was found near Todos Santos Canyon. The largest concentrations found were those of fluoranthene (120.6 ng/g), Indene(1,2,3-c,d)pyrene (115.6 ng/g) and pyrene (109.9 ng/g). Percentagewise, the main components were PAHs with three and four rings. Several indexes were used to investigate origins including simple PAH ratios and ternary plots. These indexes and plots suggest the main origin as a combination of urban air and wood and brush fires with little influence of oil.

Cadmium enrichment in the Gulf of California

Abstract We are reporting on the first dissolved cadmium (Cd) distributions for the upper 1000-m water column in the Gulf of California for the summer of 1996. The highest surface Cd concentrations were found at the midriff island region (0.21–0.35 nmol l −1 ), while the lowest were detected at the mouth (0.08–0.16 nmol l −1 ). The Gulfs surface waters were enriched with Cd compared to the adjacent open North Pacific Ocean (0.002–0.003 nmol l −1 ). Temperature, salinity, phosphate and Cd distributions showed intense vertical mixing at the midriff island region. In particular, the archipelago region is a source of Cd and nutrients. The enhanced vertical mixing near the island produces a less pronounced vertical Cd profiles than those for the Pacific Ocean, but are otherwise comparable to those of the California upwelling areas. Cd distribution at the island region can be partially explained by the mixing of Cd-enriched Pacific Intermediate Water, Subtropical Subsurface Water and Gulf of California Water mass. Vertical mixing near the islands provides with a mechanism for out-cropping of deep water, and a route for nutrient and Cd-enrichment to the surface water in the Gulf. The Cd-salinity analysis also revealed that some surface samples were cadmium-depleted. When Gulf of California Water is advected southward, Cd is removed from the dissolved phase and incorporated into particulate organic tissue, suggesting a relatively larger influence of biologically mediated processes. Between 500 and 1000 m depth, Cd concentration in the Gulf falls within a narrow range of 0.93–1.15 nmol l −1 with an average concentration of 1.04±0. 08 nmol l −1 . The deep Cd profiles in the Gulf are not different from the same water mass in the North Pacific Ocean. This indicates that deeper water masses flowing into the Gulf are not significantly changed in its Cd content. It also suggests that most organic matter remineralization mainly occurs above the 750 m of the Gulf of California. Thus, the dissolved Cd distribution in the Gulf of California is being controlled by a combination of biological cycling, thermohaline circulation, and the mixing processes at the midriff region.

Trace metals in sediment cores from the Campeche shelf, Gulf of Mexico

Abstract 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.

Use of δ13C, δ15N, and carbon to nitrogen ratios to evaluate the impact of sewage‐derived particulate organic matter on the benthic communities of the Southern California Bight

We measured stable isotope ratios (δ13Cand δ15N) of particulate organic matter (POM) sources and benthic organic matter compartments as well as sediment C to N ratios from the coastal area of the southern end of the Southern California Bight (SCB). We used the isotopic values to evaluate the relative importance of the major POM sources to the sediment and two benthic macroinvertebrates. Application of a simple model to sediment δ13C values suggested that sewage-derived POM (SDPOM) supplies an average of 48% of the organic C to study area sediments. Application of a similar model to Spiophanes duplex δ13C values suggested that SDPOM from wastewater treatment plants discharging into the SCB could supply up to 57% of the C assimilated by this important benthic macroinvertebrate in areas as far away as 26 km from SDPOM inputs. The stable isotope data for Amphiodia urtica were more difficult to interpret because of the complex feeding habits of this organism.

On the sources of PBDEs in coastal marine sediments off Baja California, Mexico

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.

On the effects of the dispersant Corexit 9500© during the degradation process of n-alkanes and PAHs in marine sediments

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.

Spatio-temporal analysis of benthic polychaete community structure in the north-western coast of Baja California, Mexico

A temporal analysis of the benthic polychaete community and its relationship with environmental variables was conducted by comparing coastal sediment samples collected in three separate sampling events between 1998 and 2013 from the southern end of the Southern California Bight (SCB). Environmental variables indicated a spatio-temporal increase of the sand fraction in sediment composition. Station stratification by depth from shallow to deep, and a reduction of trace metal enrichment (Co, Cr, Cu, Mn, Ni, Pb and Zn) was also found. There was a notable change in polychaete family composition due to high abundances and frequency of Spionidae, Chaetopteridae and Phyllodocidae in 2013, especially close to the Binational wastewater treatment plant discharge. An increase in polychaete abundance, richness and diversity was indicative of a probable relationship with regional weather conditions (El Nino-Southern Oscillation and recent drought events during sampling) along with local anthropogenic discharges of wastewater treatment plants in the area.

Treated wastewater effluent as a source of pyrethroids and fipronil at Todos Santos Bay, Mexico: Its impact on sediments and organisms

Pyrethroids are insecticides widely used to control pests and disease vectors in residential areas and agricultural lands. Pyrethroids are emerging pollutants, and their use is a growing concern because of their toxicity potential to aquatic organisms. Todos Santos Bay and the Punta Banda estuary, 2 coastal bodies located to the south of the Southern California Bight, were studied to establish a baseline of the current conditions of pollution by pyrethroids and fipronil. Eight pyrethroids, along with fipronil and its 2 metabolites, were determined in effluents from wastewater-treatment plants (n = 3), surface sediments (n = 32), and 3 locations with mussels (Mytilus californianus, n = 9). Bifenthrin, permethrin, and cypermethrin were the most common pyrethroids found in the study areas and were widespread in sediments, mussels, and wastewater-treated effluents. Fipronil and its metabolites were detected in mussels and wastewater-treated effluents only. Total pyrethroid concentrations in sediments ranged from 0.04 to 1.95 ng/g dry weight in the Punta Banda estuary (n = 13) and from 0.07 to 6.62 ng/g dry weight in Todos Santos Bay (n = 19). Moreover, total pyrethroids in mussels ranged from 1.19 to 6.15 ng/g wet weight. Based on the toxic unit data calculated for pyrethroids and fipronil for Eohaustorius estuarius and Hyalella azteca, little to no impact is expected to the benthic population structure. Environ Toxicol Chem 2017;36:3057-3064.

Influence of method of surfactant supplementation on characteristics of digestion and feeding value of fat in Holstein steers fed a high-energy finishing diet

Four Holstein steers (271 ± 11 kg) with cannulae in the rumen and proximal duodenum were used to study the influence of method of surfactant (Tween 80) supplementation on characteristics of digestion and feeding value of fat. Treatments consisted of a steam-flaked corn-based finishing diet supplemented with: (1) no supplemental fat, no surfactant; (2) 6% supplemental fat (yellow grease, no surfactant; (3) 5.75% supplemental fat plus 0.25% Tween 80 (TW) added to the diet as part of the premix (TW was mixed with premix before incorporation with grain in the mixer, as second step in diet preparation) and (4) 5.75% supplemental fat plus 0.25% TW combined directly with the supplemental fat (TW was mixed with supplemental fat before incorporation into the feed mix as penultimate step in diet preparation). There was no surfactant by supplemental fat interactions (p > 0.05). Surfactant did not affect (p > 0.05) site and extent of organic matter (OM), starch, N, acid detergent fiber (ADF) and fatty acid (FA) digestion, or digestible energy (DE) value of diet. Supplemental fat decreased (p < 0.05) ruminal and total tract digestion of OM and ADF and increased (p <0.05) the DE value of diet. The decrease in postruminal FA digestion was mainly due to decreased (p <0.05) digestion of C18:0. Digestible energy of supplemental fat averaged 6.87 Mcal/kg. It is concluded, that independent of method of addition, supplementing high-fat diets with 0.22% of Tween 80 does not influence site and extent of digestion or the feeding value of supplemental fat.