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This study investigated the influence of geochemical and environmental factors on seasonal variation in metals in Yucatan's Chelem lagoon. Anthropogenic activities discharge non-treated wastewater directly into it with detrimental environmental consequences. Accordingly, this study established the spatial and temporal patterns of fine grain sediments and concentrations of heavy metals. Multivariate analyses showed fine grain facies deposition, transition sites dominated by fine grain transport, and fine grain erosion sites. Spatial and temporal variations of heavy metals concentration were significant for Cd, Cu, Cr, and Pb. As, Cd, and Sn were as much as 12 times higher than SQuiRTs standards (Buchman ). The results indicate that aquifer water is bringing metals from relatively far inland and releasing them into the lagoon. Thus, it appears that the contamination of this lagoon is highly complex and must take into account systemic connections with inland anthropogenic activates and pollution, as well as local factors. [ABSTRACT FROM AUTHOR]

In this study, a blast furnace slag (BFS) and fly ash (FA) based adsorbent geopolymer to be used for removing Pb2+ from aqueous solutions were synthesized using the hydrothermal method at 60 °C for 24 h, and then cured at 25 °C for another six days. The alkali activator applied in this work was a combination of sodium hydroxide and sodium silicate solutions at a mass ratio of 2. The geopolymer slurry was adjusted to a Si/Al molar ratio of 3. A BFS-based geopolymer (GS) having a specific area of 23.56 m2/g and pore size and volume of 7.8 nm and 73 cm3/kg, respectively, surpassed the raw material surface by approximately 13-fold. An FA-based geopolymer (GA) having a specific area of 35.97 m2/g and a size and porous volume of 9 nm and 124 nm, respectively, surpassed the raw material surface by approximately 23-fold. In addition, GS and GA showed a cation exchange capacity (CEC) of 241.30 and 286.96 Meq/100 g, respectively. X-ray diffraction (XRD) determined sample crystallinity and it was proven by scanning electron microscopy (SEM), showing that both geopolymers were constituted of unreacted particles surrounded by amorphous and semi-amorphous products. Through Fourier transform infrared spectroscopy (FTIR), a band that was assigned to the asymmetric stretching vibration of Si-O-M (M = Na+ and/or Ca2+) non-bridging oxygen type was observed, which suggested that Na and Ca could serve as exchangeable ions in the ionic exchange process. Adsorption test data indicated that good adsorption was obtained when a neutral pH was used at room temperature, and the adsorption isotherm showed that GA had more adsorption sites than GS, which meant greater maximum adsorption capacity. [ABSTRACT FROM AUTHOR]

Riparian areas are highly dynamic systems where the control of soil pollution might be particularly challenging. Limited accessibility to river banks and bed sediments makes reclamation operations particularly difficult in these topographical positions, in comparison to floodplains. This usually leads to the large-scale spread of pollutants following pollution episodes in riparian areas. Here, we aimed to evaluate the persistence of trace-element pollution in the soils of Guadiamar River Valley (SW Spain), a large-scale remediation after a mine-spill. We monitored topsoil along the river basin, and in different topographical positions across the river section (river channel, river banks and floodplain), 16 years after a pollution episode and subsequent remediation program. River channels and banks were identified as hotspots of soil pollution, where soluble concentrations of As, Cd and Zn were significantly higher than in floodplains. Along the basin, soil pH and carbonate content was highly variable as a result of contrasted geological background, differential loads of sulfide deposition after the accident and irregular effectiveness of the applied amendments. Cadmium and Zn showed the highest levels of long-term re-distribution from the pollution source. The results suggests that the stabilization and remediation of soil pollution in river banks and channels, often overlooked when achieving remediation works, should be a priority for land managers. [ABSTRACT FROM AUTHOR]

Abstract: The collapse of a pyrite-mining, tailing dam on 1998 contaminated an area of 4286ha along the Agrio and Guadiamar river valleys in southern Spain. Over 2700ha of the Doñana marshes, an important wintering area for wetland European birds, were contaminated. This study reports analyses of the tubers of Scirpus maritimus (an important food for greylag geese, Anser anser) collected in 2000 in the “Entremuros” (spill-affected area) and in nearby unaffected Doñana marshes (control areas). In the spill-affected area mean tuber tissue concentrations of Cd (0.25mgkg−1) and Zn (61mgkg−1) were greater than in those tubers from the control area (0.02 mg kg−1 for Cd, and 22mgkg−1 for Zn); values of Cd and Zn in “Entremuros” (samples collected two years after the mine spill) were much smaller than those reported only a few months after the accident. Trace elements (As, Fe, Mn and Tl, and to a lesser extent Cd and Pb) showed a preferential accumulation in the outer skin of tubers. Surprisingly, concentrations of As and Fe were greater in tubers from some marsh sites not affected by the mine-spill than in tubers from the “Entremuros”. We suggest that relic river channels within the Doñana marshes may be contaminated by trace elements from historic mining activities. An exhaustive study of macrophytes and other plant species in this area is recommended to identify potential risks to wildlife. [Copyright &y& Elsevier]

The failure of a tailing pond dam at the Aznalco´llar pyrite mine (SW Spain) in April 1998 released a toxic spill affecting approximately 4300 ha along the Agrio and Guadiamar valleys. Two years later, we have studied yield and concentration of mineral nutrients and trace elements in sunflower plants grown in the spill-affected soil, and in an adjacent unaffected soil as comparison. The study has been carried out in plants at seedling (V4) and mature (R8) stages. Shoot and root biomass of sunflower seedlings was significantly smaller in the affected soil than in the unaffected soil, but there was no significant difference at the mature stage. Oil production was greater in the spill-affected plants. We have not detected any ‘fertilising’ effect caused by the acid waters of the spill on the main nutrient (N, P and Ca) acquisition, as documented in 1998 for sunflower plants flooded by the spill. Sunflower plants growing in the spill-affected soil reached adequate levels of nutrients. None of the trace elements measured—As, Cd, Cu, Pb and Tl—reached levels either phytotoxic or toxic for humans or animals in seeds and the above-ground part of the spill-affected plants. We evaluate the potential use of sunflower plants for phytoremediation. The potential for phytoextraction is very low; however, it may be used for soil conservation. The production of oil (usable for industrial purposes) may add some value to this crop. [Copyright &y& Elsevier]

The collapse of the tailing dam in the Aznalco´llar pyrite mine (SW Spain) occurred in April 1998 and affected approximately 4300 ha along the Agrio and Guadiamar valleys. An urgent soil cleaning up and remediation programme was started just after the accident. Eighteen months later, mineral nutrients and trace elements concentration in soil and two wild grasses — Cynodon dactylon and Sorghum halepense — have been studied. Three types of conditions are distinguished: (a) unaffected soils (control); (b) cleaned up and remediated soils (remediated); and (c) sludge-covered soils left in a fenced plot (non-remediated). As, Cd, Cu and Pb in grasses reached toxic levels for the food web in the non-remediated plot, while on remediated soils only Cd reached a toxic level in grass tissues. However, Pb and, to a lesser extent As and Fe, reached also toxic levels in unwashed plants (as they would be ingested by animals) in remediated soils. Both native grasses seem tolerant of trace elements pollution and suitable for stabilisation of spill-affected soils. [Copyright &y& Elsevier]