Temporal variation of persistent organic pollutant (POP) residue concentrations in sediments from the bay of Chetumal, Mexico

Organochlorine contaminants in sediments and factors influencing their distribution in the natural marine protected area in the gulf of Mexico

The aim of this study was to determine the concentration of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in marine sediments of a natural marine protected area (NMPA), Veracruz Reef System (VRS), in the Gulf of Mexico (GoM). This NMPA represents one of the first coastal sites with port activity in Mexico, which causes a range of human activities that require adequate planning so as not to impact and destroy this marine protected area; In this sense, this work represents the first effort aimed at diagnosing the presence of organochlorine contaminants in reef sediments from the mainland, both from the adjacent port area and from more distant regions with dominant agricultural activities that ultimately affect this NMPA. Content of organic matter (OM), carbonates and grain-size composition were determined to investigate their influence on compounds distribution in the sediment through multivariate analysis. The potential risk represented by organochlorines concentrations was evaluated taking as reference Sediment Quality Guidelines (SQGs). Levels of ∑PCBs, ∑DDTs, ∑HCHs and ∑Cyclodienes ranged from 11.59 to 29.79, < 0.01 to 34.11, 22.10 to 102.80, and 17.21-104.45 ng g-1 dry weight (DW), respectively. The statistical analysis revealed that the content of mud and organic matter were the parameters that might influence PCBs distribution in the sediment while OCPs could be influenced by sand and carbonate. The theoretical risk assessment estimated with the results obtained showed that concentrations of lindane, endrin, dieldrin and p,p'-DDT could have an adverse effect on the reef benthic community and continued monitoring is required. The data obtained on the organochlorine contaminants (OCs) considered in this work will contribute to support the strategies proposed by the Mexican federal government entity to continue with the conservation and surveillance of this NMPA and thereby guarantee the least impact derived mainly from port and related agricultural activities.

Recent history of persistent organic pollutants (PAHs, PCBs, PBDEs) in sediments from a large tropical lake

²¹⁰Pb-dated sediment cores and surface sediments from Lake Chapala (LC), Mexico, were analyzed to assess the temporal trends in concentrations and fluxes of persistent organic pollutants (POPs: PAHs, PCBs and PBDEs). Total sediment concentrations of PAHs (95-1,482 ng g^-1), PCBs (9-27 ng g^-1) and PBDEs (0.2-2.5 ng g^-1) were indicative of moderate to intense contamination. The POP concentrations have progressively increased since the 1990s. The light molecular weight PAHs, and the prevalence of PCB congeners with low-chlorination levels (e.g., di- to tri-CB) and low-to medium-brominated (tri- to penta-BDE) PBDEs in most sections of the sediment profiles, suggested that these POPs have most likely reached these sediments by long-range atmospheric transport from distant sources; although the significant presence of heavier PAH, PCB and PBDE congeners in the topmost sediments, indicate that other nearby and local sources (soil erosion from the catchment, urban and industrial wastewaters discharges, as well as navigation) might have also contributed to the recent input of POPs to LC. Taking into account the relevance of LC as regional freshwater supply and commercial fishing ground, the potential risk posed by the organic contaminated sediments to the biota and human population should not be underestimated.

Organochlorine pesticides in residential soils and sediments within two main agricultural areas of northwest Mexico: Concentrations, enantiomer compositions and potential sources

The agricultural Mexicali and Yaqui valleys (MV, YV) in northwest Mexico were heavily treated with organochlorine pesticides in the past. Residential soils and agricultural drain sediments were sampled in 2008-2009 and analyzed for DDTs (o,p'- and p,p'- isomers of DDE, DDD and DDT); hexachlorocyclohexanes (α-, β-, γ- and δ-HCH) and chlordanes (trans-chlordane, cis-chlordane, heptachlor and heptachlor exo-epoxide). Geometric means (GMs) (ng g^-1 dry weight) were: MV soils (n = 27) ΣDDT 22, ΣHCH 0.80, ΣCHL 0.88; YV soils (n = 25) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.67; MV sediments (n = 3) ΣDDT 5.0, ΣHCH 0.23, ΣCHL 0.53; YV sediments (n = 8) ΣDDT 2.6, ΣHCH 0.12, ΣCHL 0.090. GMs were significantly higher (p < 0.05) in MV than YV soils for ΣDDT and ΣHCH, but not for ΣCHL. Comparison to worldwide regulatory guideline values (RGVs) for residential soils showed all compounds below mean or GM RGVs, but above the lowest RGV in some cases. Low p,p'-DDT/(p,p'-DDT + p,p'-DDE) in most soils indicated aged residues. Lack of p,p'-DDT metabolism might account for its dominance in a few soils. HCH isomer profiles suggested aged technical HCH in the YV, and technical HCH + lindane in the MV. Heptachlor dominated the ΣCHL, probably from application of technical heptachlor as well as chlordane. Chiral compounds were nonracemic in soils and sediments and indicated enantioselective microbial degradation of (+)α-HCH, (-)trans-chlordane, (-)cis-chlordane and (+)o,p'-DDT. Depletion of (+)o,p'-DDT in soils may account for similar enantiomer signatures previously reported in air of northwest Mexico.

Effects of oil spill related chemical pollution on helminth parasites in Mexican flounder Cyclopsetta chittendeni from the Campeche Sound, Gulf of Mexico

During an environmental impact study of an accidental oil spill in the Campeche Sound in October 2007, we examined the helminth parasites of the benthic flatfish Cyclopsetta chittendeni as well as the concentrations of hydrocarbons and heavy metals in the sediment. The aim of this study was to determine the potential effects of these contaminants on the helminth communities of the flatfish. A total of 427 hosts were examined, and 16,895 helminths, representing 17 species, were obtained from two surveys (March and July, 2008). Statistically significant negative associations were observed between the hydrocarbons and helminth parasite abundances using multivariate methods. The results suggest that in October 2007, the oil spill had a strong negative effect on these helminth communities. However, after five months, the impacted stations were re-populated by both the flatfish and helminths. The most likely explanation for this rapid recovery is the rescue effect from non-impacted habitats to impacted stations.

Assessment of persistent organic pollutants levels in blood samples from Quintana Roo, Mexico

The Stockholm Convention on persistent organic pollutants (POPs) sought to determine baseline exposures to POPs in the general population; however, in developing countries, exposure to these chemicals in hot spots may be an issue of public health considering its magnitude. Therefore, the aim of this study was to assess the levels of POPs in the blood of children living in three communities in the Southeastern Region of Mexico. During 2007, we studied a total of 96 healthy children (aged 6-12 years). Quantitative analyses were performed using gas chromatography coupled with mass spectrometry. High levels of p,p'-DDT and its principal metabolite, p,p'-DDE, were found in the blood of children living in the three communities studied, the levels ranged from 463.5 to 9046.3 ng/g lipid and from 490.8 to 57,712.4 ng/g lipid for DDT and DDE, respectively. In addition, high levels of lindane (γ-HCH) were found, with mean levels ranging between 575.4 and 6580.6 ng/g lipid. Moreover, children living in the study region were also exposed to polychlorinated biphenyls (PCBs), and the levels of these compounds in the blood of children were very similar between the communities with mean levels of around 3000 ng/g lipid (total PCBs). In conclusion, we demonstrated that children living in the studied communities were exposed to complex chemical mixtures (DDT, DDE, lindane and PCBs) rather than to individual compounds. Therefore, in future studies it is important to understand the potential interactions between the components of these mixtures.

Passive air sampling of organochlorine pesticides in Mexico

The spatial and temporal variation of organochlorine pesticides (OCs) in air across Mexico was investigated by deploying passive samplers at eleven stations across the country during 2005-2006. Integrated samples were taken over three-month periods and quantified for DDT compounds, endosulfans, toxaphenes, components of technical chlordane, hexachlorocyclohexanes (HCHs), and dieldrin. Enantiomers of chiral chlordanes and o,p'-DDT were determined on chiral stationary phase columns as an indicator of source and age. Results are discussed in combination with pumped air samples taken at four other stations in southern Mexico during 2002-2004. DDT and its metabolites, endosulfan and toxaphene were the most abundant OCs detected in all sampling sites. Atmospheric concentrations of SigmaDDT (p,p'-DDT + o,p'-DDT + p,p'-DDE + o,p'-DDE + p,p'-DDD + o,p'-DDD) ranged from 15 to 2360 pg m(-3) with the highest concentrations found in southern Mexico and the lowest found in northern and central Mexico. A fresher DDT residue was observed at sites with greater DDT use and in the southern part of the country, as shown from the higher FDDTe = p,p'-DDT/(p,p'-DDT + p,p'-DDE) and nearly racemic o,p'-DDT. This agrees with the former heavy use of DDT in the endemic malarious area of the country. A local hotspot of endosulfan was identified at an agricultural area in Mazatlan, Sinaloa, with a annual mean concentration of SigmaENDO (endosulfans I + II + endosulfan sulfate) = 26,800 pg m(-3). At this site, higher concentrations of SigmaENDO were recorded during the winter (November to February) and spring (February to May) periods. From back trajectory analysis, this coincides with a shift in the air mass coming from the Pacific Ocean (May to November) to the inland agricultural area (November to May). The elevated SigmaENDO observed is likely due to the local agricultural usage. HCHs, chlordanes, transnonachlors, and dieldrin were more evenly distributed across the country likely due to them being aged residues and more diffuse in the environment. In contrast, hotspots of endosulfans, DDTs, and toxaphenes were observed as they were heavily used in localized agricultural or malarious regions of Mexico.

Geographical information system (GIS) mapping of spatio-temporal pollution status of rivers in Ibadan, Nigeria

More accurate spatio-temporal predictions of urban environment are needed as a basis for assessing exposures as a part of environmental studies and to inform urban protection policy and management. In this study, an information system was developed to manage the physico-chemical pollution information of Ibadan river system, Oyo State, Southwest Nigeria. The study took into account the seasonal influences of point and non-point discharges on the levels of physico-chemical parameters. The overall sensitivity of the watershed to physicochemical environmental pollution revealed that during dry season, of the 22 (100%) sample points, only 3 (13.6%) were unpolluted; 6 (27.3%) were slightly polluted; 10(45.4%) were moderately polluted; 2 (9.1%) were seriously polluted and 1 (4.5%) was exceptionally polluted. During rainy season, 3 (13.6%) were unpolluted; 7 (31.8%) were slightly polluted; 9 (40.9%) were moderately polluted; 2 (9.1%) were seriously polluted and 1 (4.5%) was exceptionally polluted. There is a considerable environmental risk associated with the present level of pollution of the Ibadan river water body on fish health and biodiversity. This research provides a basis for aquatic management and assist in policy making at national and international levels. Appropriate strategies for the control of point and non-point pollution sources, amendments and enforcement of legislation should be developed.