Leticia Rosales-Hoz

Heavy metals in sediment cores from a tropical estuary affected by anthropogenic discharges: Coatzacoalcos estuary, Mexico

Large scale industrial development has taken place in the Coatzacoalcos river estuary, SE Mexico, over the last 32 years, and the area is now regarded as the most polluted coastal area of Mexico. A series of sediment cores were taken from the lower Coatzacoalcos river and the estuary, and the concentrations of trace elements (Zn, Co, Cu, Cr, Ni, Pb, V), major elements (Al, Si, Mn, Fe, Ti, Ca, Mg, Na, K, P) and organic matter determined. Heavy metal concentration seems to be largely dependant on proximity to industrial areas, with highest metal concentrations (particularly for Zn, Ni and Cu) found at Teapa, the most heavily industrialized site, and lowest values found at Jicaro, upstream of the main industrial areas. At all of the sites examined, heavy metals either show a relatively uniform distribution with depth, or subsurface maxima, which reflect changes in sediment composition. There is little evidence for significant early-diagenetic remobilization at any of the sites studied. 210Pb and 137Cs data at Teapa indicate that the sediments have accreted rapidly and may be vigorously mixed, and so these sediment cores cannot be used to reliably reconstruct temporal changes in pollutant input.

Petrography and Geochemistry of Holocene Sands in the Western Gulf of Mexico: Implications for Provenance and Tectonic Setting

ABSTRACT Petrographic and geochemical analysis of recent fluvial, beach, and dune sediments derived from the same source terrane was carried out in the western Gulf of Mexico to show the usefulness of the these three environments in determining the tectonic setting of the source. Petrographic analysis showed that dunes concentrate the less heavy minerals and quartz grains by means of the selectiveness of the wind as a transport agent. In contrast, the heavier grains, such as the rock fragments remain in the beach and fluvial environments because of the high transport energy. Beach and dune sands do not define a particular tectonic setting because of the selective wind action of the backshore of the beach and the dune environments and the less intense chemical weathering. The fluvial sands are the most representative in terms of interpretation of tectonic setting because they reflect the volcanic domain of the source rocks of the Trans-Mexican Volcanic Belt. The geochemical results of all three sedimentary environments reflect the calcalkaline character of the igneous source rocks of the Trans-Mexican Volcanic Belt. The samples fall in a continental island-arc-margin field with basaltic and andesitic source rocks. A correlation and factor analysis indicates an alkali-basalt source that contributes to the composition of the beach, dune, and fluvial sediments. The geochemical analysis of the sediments more accurately reflects the tectonic setting regardless of the depositional setting of the sediments.

Heavy metal enrichment in surface sediments from the SW Gulf of Mexico

The south west coastal zone in the Gulf of Mexico is an area with great industrial and agricultural development, which experiences intensive prospecting and extraction of hydrocarbons. After running through industrial, agricultural, and urban areas, waters from both the Jamapa River and La Antigua River arrive here. The rivers’ discharge areas of influence were estimated considering the textural and chemical composition of the supplied sediments. The main factors that determine sediment distribution were mineralogy, heavy minerals, carbonates, and anthropic contributions. The presence of metals in excess was evaluated using various pollution indicators, such as the enrichment factor, contamination factor, modified contamination factor, and geo-accumulation indexes. Data from different used contamination indexes show metal enrichments in As, Cu, Zn, Co, Cr, and V in La Antigua; As, Cu, and Cr in Jamapa; and As, Zn, and Pb in the Continental slope area. The adverse effects of metals on aquatic organisms were assessed using sediment quality guidelines that show Ni, As, Cu, and Cr may produce adverse effects on coastal areas. There was no evidence of contamination associated to the oil industry.

Geochemical study of hydrothermal core sediments and rocks from the Guaymas Basin, Gulf of California

Abstract A geochemical study of core sediments from the Guaymas Basin was undertaken by X-ray analysis and showed minerals such as barite, gypsum, wurtzite, chalcopyrite, marcasite, galena and calcite. The random relation between metal concentration and core depth apparently reflects the chages in hydrothermal activity. Mineral grains with holes and cavities were observed by SEM photomicrography. These holes are probably due to degastification of the samples, which can be related to the presence of the Guaymas Basin is due to active extensional tectonics, the associated seismic activity in the Southern Rift Valley and the high rate of sedimentation.

Distribution of Dissolved Trace Metals Around the Sacrificos Coral Reef Island, in the Southwestern Gulf of Mexico

A reef system in the southwestern Gulf of Mexico is affected by anthropogenic activities, sourced by urban, fluvial, and sewage waters. Dissolved metals have higher concentrations during the rainy season. V and Pb, were derived from an industrial source and transported to the study area by rain water. On the other hand, Jamapa River is the main source for Cu and Ni, which carries dissolved elements from adjacent volcanic rocks. Principal Component Analysis shows a common source for dissolved nitrogen, phosphates, TOC, and suspended matters probably derived from a sewage treatment plant, which is situated near to the study area.

Historical trace element accumulation in marine sediments from the Tamaulipas shelf, Gulf of Mexico: An assessment of natural vs anthropogenic inputs

The Gulf of Mexico is considered one of the worlds major marine ecosystems, supporting important fisheries and habitats such as barrier islands, mangrove forests, seagrass beds, coral reefs etc. It also hosts a range of complex offshore petroleum exploration, extraction, and refining industries, which may have chronic or acute impacts on ecosystem functioning. Previous work on the marine effects of this activity is geographically incomplete, and has tended to focus on direct hydrocarbon impacts, while impacts from other related contaminants (e.g. heavy metals, salt-rich drilling muds) which may be discharged from oil facilities have not been widely assessed. Here, we examine historical trace element accumulation in marine sediments collected from four sites in the Tamaulipas shelf, Gulf of Mexico, in the area of the Arenque oil field. Dated sediment cores were used to examine the sources, and historical and contemporary inputs, of trace metals (including those typically present in oil industry discharges) and their potential biological impact in the Tamaulipas aquatic environment over the last 100years. CaO (i.e. biogenic component) normalized data showed increasing V, Cr, Zn, Cu, Pb, Zr and Ba towards the sediment surface in three of the four cores, with Ba and V (based on an adverse effect index) possibly associated with adverse effects on organisms. Dated Ba/CaO profiles show an increase of 30-137% after opening of oil installations in the study area, and can be broadly correlated with increasing oil industry activities across the wider Gulf of Mexico. Data do not record however a clear enhancement of Ba concentration in sediment cores collected near to oil platforms over more distal cores, indicating that any Ba released from drilling platforms is incorporated quickly into the sediments around the drilling sites, and once this element has been deposited its rate of resuspension and mobility is low. CAPSULE ABSTRACT Sediment core data from the Tamaulipas shelf show the influence of oil industry activities on selected trace element concentrations, with Ba/CaO broadly correlating with increasing oil industry activities across the wider Gulf of Mexico.

Sedimentary heavy metal(loid) contamination in the Veracruz shelf, Gulf of Mexico: A baseline survey from a rapidly developing tropical coast

This study examines sediment texture, geochemistry and sediment accumulation in cores from four sites in the Veracruz shelf area of the Gulf of Mexico, to assess the inputs of heavy metal(loid)s (and their potential biological impacts) in this carbonate-dominated shelf system, and to examine the rate of sedimentation near to the mouths of the La Antigua and Jamapa Rivers. The use of different pollution indices showed enrichment with Pb in all cores studied, although based on sediment quality guidelines As was the only element that has potential to occasionally cause damage to the benthic organisms present in the area. Heavy metal(loid) and sediment input from terrestrial and coastal sources is limited compared to more proximal, near-shore areas. The sediment core data presented however give a baseline dataset for heavy metal(loid) concentrations in the Veracruz shelf, against which future anthropogenic inputs can be assessed.

Mexican Beach Sands: Composition and Vulnerability

Prior to any design in the beach environment such as urban construction in dune areas, or the creation of fixed or dynamic barriers that cause undesirable deposition or erosion in the coastal zone, it is essential to have knowledge of beach particle size, sediment transport and composition of the unconsolidated material associated with the relief of the coastal plain. Among the tools for handling beaches it is essential to know the variations that control the beach characteristics. The increasing of ocean acidification that is taking place in the last years is another factor to be considered, as it can contribute to the mortality of calcareous organisms that often are natural constituents on the beaches. The main objective of this chapter is to provide basic and applied knowledge of beaches. Traditionally the main components used to classify the composition of beach sands include quartz, feldspar and rock fragments. Other components taken into consideration are terrigenous, biogenic, autigenos, chert, mica and heavy minerals. The seventeen coastal states of Mexico covering more than 11,000 kilometers long, show a lot of variations in morphology as are beaches with semi-protected pocket waves and longshore currents as is common in the South Mexican Pacific and portions of the Sea of ​​Cortez, opposite to vast coastal rectilinear beaches receiving the onslaught waves. In contrast, the Yucatan Peninsula consists of lowland calcareous composition which includes biogenic sediments and sometimes some rocks associated with beaches that being compacted and lithified really consist of rocky coastline that cannot be called a beach, since its requirement is that is unconsolidated material. This paper presents the different beach composition found in Mexico, their classification, characteristics such as relief, lithology, coastal plain size, weather, anthropic influence, etc. It emphasizes that beach sands must not be treated for study as rocks, because in them the siliceous or carbonate in the past were quartz or calcareous detritus. Resistance to transport, waves and longshore currents are very variable. Examples of variables that affect the compositional nature of the beaches sands are: (i) the climate allows preservation of feldspars as in some beaches of the Peninsula of Baja California, (ii) the wide and smooth relief of the coastal plain produce quartz’s particles often of smaller size and (iii) beaches lithology associated with basic or intermediate rocks are not good potential producers of quartz. This chapter shows some regions of Mexico which are more variable to the rising sea level of the sea and some recommendations on field work are made.