The key role of biogenic arsenic sulfides in the removal of soluble arsenic and propagation of arsenic mineralizing communities.

Biogeochemical processes govern the transport and availability of arsenic in sediments. However, little is known about the transition from indigenous communities to cultivable consortia when exposed to high arsenic concentrations. Such cultivable communities could be exploited for arsenic bioremediation of waste streams and polluted sites.

Presence of Arsenic in Potential Sources of Drinking Water Supply Located in a Mineralized and Mined Area of the Sierra Madre Oriental in Mexico.

Mine wastes from the La Aurora mine in the state of Guanajuato were generated by the flotation process and placed in four tailing dumps on the local stream while the plant operated. Given that these wastes contain toxic elements, it is important to establish their impact on the quality of several surrounding natural sources of water that are considered potential drinking water supplies. This study identified four water source types, in which the contents of arsenic (As), mercury (Hg), and thallium (Tl) were exceeded, according to international guideline values for drinking water quality.

Effect of heavy metals on seed germination and seedling development of aff. collected on the slope of a mine tailing dump.

aff. plants grow on mining waste abandoned 100 years ago, exposed to high concentrations of heavy metals. Accumulation of heavy metals in plant biomass has been related to the phyto-accessible fractions of these, so we assessed the effect of those heavy metals in different concentrations on the germination and development of seedlings.

Dissolution and final fate of arsenic associated with gypsum, calcite, and ferrihydrite: Influence of microbial reduction of As(V), sulfate, and Fe(III).

Several studies have demonstrated that gypsum (CaSO·2HO) and calcite (CaCO) can be important hosts of arsenic in contaminated hydrogeological systems. However, the extent to which microbial reducing processes contribute to the dissolution and transformation of carbonate and sulfate minerals and, thereby, to arsenic mobilization is poorly understood. These processes are likely to have a strong impact on arsenic mobility in iron-poor environments and in reducing aquifers where iron oxyhydroxides become unstable.

Role of indigenous microbiota from heavily contaminated sediments in the bioprecipitation of arsenic.

High arsenic concentrations have been detected in alluvial aquifers of arid and semi-arid zones in Mexico. This work describes the potential of microbial arsenate reduction of the indigenous community present in sediments from an arsenic contaminated aquifer. Microcosms assays were conducted to evaluate arsenate and sulfate-reducing activities of the native microbiota.

Optimal conditions for chlorothalonil and dissolved organic carbon in horizontal subsurface flow constructed wetlands.

The most efficient system of horizontal subsurface flow constructed wetlands (HSSFCW) for removing dissolved organic carbon (DOC) in the presence of chlorothalonil pesticide (CLT) present in synthetic domestic wastewater was determined using the macrophyte Phragmites australis. Two concentrations of CLT (85 and 385 μg L) and one concentration of glucose (20 mg L) were evaluated in four pilot scale horizontal surface flow constructed wetlands coupled with two sizes of silica gravel, igneous gravel, fine chalky gravel (3.18-6.

Arsenic mobility controlled by solid calcium arsenates: a case study in Mexico showcasing a potentially widespread environmental problem.

An As-contaminated perched aquifer under an urban area affected by mining was studied over a year to determine the contamination source species and the mechanism of As mobilization. Results show that the dissolution of calcium arsenates in residues disposed on an inactive smelter has caused high levels of As pollution in the adjoining downgradient 6-km perched aquifer, reaching up to 158 mg/L of dissolved As, and releasing a total of ca. 7.

Inhibition of sulfate reduction by iron, cadmium and sulfide in granular sludge.

This study investigated the inhibition effect of iron, cadmium and sulfide on the substrate utilization rate of sulfate reducing granular sludge. A series of batch experiments in a UASB reactor were conducted with different concentrations of iron (Fe2+, 4.0-8.

Phytochelatin-cadmium-sulfide high-molecular-mass complexes of Euglena gracilis.

High-molecular-mass PC complexes (PC-HMWCs) constituted by phytochelatins (PCs), cadmium and sulfide are synthesized by several organisms after exposure to cadmium. In this study, PC-HMWCs were isolated from photoheterotrophic Euglena gracilis and purified to homogeneity, resulting in compounds of molecular mass 50-380 kDa depending on the CdCl2 and sulfate concentrations in the culture medium. In contrast with plants and some yeasts, PC-HMWCs from E.