RESUMO
The environmental exposure to As, Se, Hg, Pb, Cr and toxaphene was assessed for 11 freshwater fish species in irrigation channels, agricultural return flow drains, a drain collecting lagoon and sections of the Colorado River at the Mexicali valley in Baja California, México, during August 2015-April 2016. Arsenic (2.90 ng ml-1) and Se (1.41 ng ml-1) in water had the highest concentrations in the return flow drains (Hardy River and Xochimilco Lagoon, respectively). However, fish axial muscle tissue had the highest concentration of Se (8.3 µg g-1) and Hg (0.36 µg g-1) in Colorado River fresh water, while As (1.7 µg g-1) in Hardy River fish was highest. Selenium concentrations in all fishes and toxaphene in Cyprinus carpio and Ameiurus natalis are above the safe levels for human consumption (0.3 µg g-1 and 180 ng g-1 respectively). Toxaphene was detected in the fish axial tissue, having the highest concentrations in Poecilia latipinna (690 ng g-1) in the Colorado River. The low proportion of the 8-Cl toxaphene congeners in fish suggests degradation of this pollutant. Tilapia. sp. cf. zillii had the most genotoxic damage with 7.4 micronucleated erythrocytes per 10,000 erythrocytes in Xochimilco Lagoon and 2 in Hardy River. The genotoxicity in all the fish species studied was significantly correlated to the concentrations of As and Se in water.
Assuntos
Peixes/fisiologia , Metais/toxicidade , Toxafeno/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Monitoramento Ambiental , Metais/metabolismo , México , Rios , Toxafeno/metabolismo , Poluentes Químicos da Água/metabolismoRESUMO
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.
Assuntos
Sedimentos Geológicos/análise , Éteres Difenil Halogenados/análise , Poluentes Químicos da Água/análise , Monitoramento Ambiental , México , Oceano Pacífico , Água do Mar/químicaRESUMO
Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were studied in sediment cores from two distinctive modern channels of the Colorado River (CR) delta. Their abundance and temporal changes are associated with flood-flows from the CR across the USA-Mexico border. The CR channel is directly exposed to river flood-flows while the Hardy River (HR) is a local channel derived mainly from agricultural runoff, geothermal effluents, and treated urban wastewater. Different headwater compositions and degrees of exposure to flood-flows appear to be the factors controlling the composition of persistent organic pollutants (POPs). Enrichment of OCPs (46 ng g(-1) dwt in HR and 4.37 ng g(-1) dwt in CR) occurred during or a few years after flooding. PCB-138 (4.2 ng g(-1)dwt) is enriched in HR suggesting its origin in dielectric oils from the geothermal power plant. PCB-28 (2.1 ng g(-1)dwt) in CR may be related with atmospheric input and/or re-deposition of upstream sediments. In surficial sediments (0-3 cm), only HR exceeds international sediment quality guidelines (4,4'-DDE=8.16 ng g(-1)dwt and ΣDDT=8.34 ng g(-1)dwt).
Assuntos
Sedimentos Geológicos/química , Praguicidas/análise , Bifenilos Policlorados/análise , Poluentes Químicos da Água/análise , Clordano/análise , DDT/análise , Diclorodifenil Dicloroetileno/análise , Endossulfano/análise , Água Doce/química , Hidrocarbonetos Clorados/análise , México , Rios , Estados Unidos , Movimentos da ÁguaRESUMO
San Ignacio and Ojo de Liebre lagoons in central Baja California, Mexico are nursery and grazing grounds for whales and turtles. Ojo de Liebre Lagoon also supports a salt mine operation. By concentrating trace metals via evaporation, this activity might harm biota. Consequently, salt mining might be incompatible with the lagoon's ecological role. Eelgrass can incorporate these elements and reroute them to other organisms. Trace metals in sediments (Cd, Co, Cu, Mn, Ni, Pb, Zn, and Fe) were measured at both lagoons. Some (Cu, Mn, Pb, and Zn) were also measured in Zostera marina patches at both lagoons. The results did not show elevated metal concentration at any lagoon, either for sediments or eelgrass. No statistically significant differences between lagoons were found. However, eelgrass at both lagoons showed larger concentration ranges than in sediments. Also, a correlation exists between sediment metal concentration and its concentration in eelgrass. Surprisingly, several sediment metal concentrations are higher than those considered as elevated for the Southern California Bight.
Assuntos
Sedimentos Geológicos/análise , Metais Pesados/análise , Poluentes Químicos da Água/análise , Zosteraceae/química , Análise de Variância , México , Oceano Pacífico , Salinidade , Espectrofotometria AtômicaRESUMO
During 2004 the spatial distribution of total Hg in sediments from Todos Santos Bay, Baja California, México was studied to evaluate the degree of environmental impact in this bay. The results showed low concentrations and no Hg enrichment at any site. These findings suggest natural levels of Hg in the water of Todos Santos Bay. The regional distribution of Hg/Fe shows lower values in the East and higher in the West of the bay. No significant correlations (p<0.05) were found between Hg and organic matter or particle size, suggesting that the distribution of Hg is not controlled by these variables.
Assuntos
Sedimentos Geológicos/química , Mercúrio/análise , Poluentes Químicos da Água/análise , Compostos Orgânicos/análise , Tamanho da PartículaRESUMO
Distribution and isomeric composition of LABs in surface marine sediments were evaluated at the southern end of the southern California Bight. LABs are used as tracers of wastewater discharges. The area studied extends from the Mexico-USA border to the Todos Santos Bay, Baja California in the south. The area was partitioned into a northern, central and a southern stratum. GC-MS was used for the analysis of LABs concentration. The average value of total LABs concentration was 17.4, 32.0 and 24.9 ng/g for the north, central and southern strata, respectively. LABs were not correlated with either sediments grain size (%<63 microm) or sediment organic carbon contents. The highest concentrations values of LABs were found in the northern and central strata near the 200 m isobath. Based on the I/E index, the estimated average percentage degradation was 21.3, 15.9, and 8.4% for the northern, central and southern strata respectively. Based on the isomeric composition of LABs, the largest degradation value was found in the northern stations. Internal isomers did not show significant enrichment, however, short-chained isomers (LAB(10), LAB(11)) showed enrichment. It was found that 67 out of the 68 stations measured had concentrations above detection limits. This suggests extensive contact of wastewater discharges with marine sediments in the area. An estimate of the amount of LABs per year based on detergent consumption per capita is provided.
Assuntos
Derivados de Benzeno/análise , Poluentes Ambientais/análise , Sedimentos Geológicos/química , Esgotos/análise , Derivados de Benzeno/química , Biodegradação Ambiental , Monitoramento Ambiental/métodos , Poluição Ambiental , Isomerismo , México , Eliminação de Resíduos Líquidos/métodosRESUMO
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.