Baseline for plastic and hydrocarbon pollution of rivers, reefs, and sediment on beaches in Veracruz State, México, and a proposal for bioremediation.

Plastic and hydrocarbon pollution in aquatic ecosystems is a worldwide reality and serious concern today. Plastic debris presents a threat to ecosystems and organisms. Hydrocarbons are also considered priority pollutants. The hydrophobicity of the polymer in combination with the high surface area causes plastics to act as a vector for organic contaminants such as hydrocarbons. The first aim of this work was to evaluate the presence of plastic and hydrocarbon pollution in water from two reefs and two rivers and to identify plastic in six sediment beaches in Veracruz State, Mexico. In addition, the second aim was to analyse the ability of a bacterial consortium to biodegrade hydrocarbons in an airlift bioreactor and to identify degrading bacterial strains of polyethylene terephthalate (PET). Microplastics (100 nm-5 mm) were found in four water samples. Fragments of plastic collected from the reefs ranged in size from 0.716 to 32 µm and in rivers from 0.833 to 784 µm. On the sediment beaches, macroplastics of sizes 2-10 cm were detected. A number of hydrocarbons were also detected in the water samples of both reefs and one river, including n-octane, n-nonane, phenanthrene, n-eicosane, n-dotriacontane, n-hexatriacontane, n-triacontane, and n-tetratriacontane. As a biotechnological alternative for remediation of hydrocarbons and plastics, we attempted to produce a collection of native microorganisms able to degrade them. This work shows results from the bioprospection of a bacterial consortium (Xanthomonas, Acinetobacter bouvetii, Shewanella, and Aquamicrobium lusatiense) for hydrocarbon biodegradation in an airlift bioreactor. The tested consortium was able to successfully degrade the maximum diesel concentration (20 g L-1) tested for 10 days. Also, the first visual evidence of PET degradation by an isolated forest-native bacterial strain showed that Bacillus muralis is the most efficient degrader.

Enhancement of the biogas and biofertilizer production from Opuntia heliabravoana Scheinvar.

Waste Opuntia is an abundant source of biomass to produce biogas and biofertilizer in a small and commercial scale. This crop has a high biomass yield, wide adaptation to diverse climatic zones, rapid growth, and low input requirements. This study aimed to evaluate the combined effect of adjusting C/N ratio and an alkaline pretreatment (AP) of waste Opuntia heliabravoana Scheinvar in the production of biogas and biofertilizer in anaerobic reactors. AP bioreactors produced more biogas than the control (C, without the combined effect of AP); besides, in this process, it was not necessary to use additional water due to the high content of water that is present in the tissue of this crop. On the other hand, both biofertilizers (C and AP) had enssential microbial groups that help to enhance plant nutrition as S-reducers, S-oxidizers, amylolytic, cellulolytic bacteria, anaerobic S-mineralizers, cellulolytic fungi, and P-solubilizers. Also, the AP treatment to help to increase 1.5:1 total nitrogen (TN) concentration decreased the pathogenic microorganisms in the biofertilizer compared to the C treatment. For this reason, Opuntia spp. is a good substrate for production of biogas and biofertilizer with essential nutrients for many crops in area with water scarcity.

Cadmium Removal from Aqueous Systems Using Opuntia albicarpa L. Scheinvar as Biosorbent.

The aim of this research was to investigate the use of a natural adsorbent like nopal (Opuntia albicarpa L. Scheinvar) for removing cadmium from aqueous solutions with low concentrations of this metal. Two treatments were applied to the cladodes: a dehydration to get dehydrated nopal (DHN) and heating up to 90°C to obtain a thermally treated nopal (TN). After examining the effect of various pH values (2-7), the capacity of each biosorbent was examined in batch sorption tests at different dosages (0, 500, 1000, 1500, 2000, and 3000 mg L(-1)). The results indicated that adsorption of cadmium to biomass of DHN and TN was highly dependent on pH and biosorbent dosage. The best removal of cadmium (53.3%, corresponding to q e of 0.155 mg g(-1)) was obtained at pH 4.0 by using the TN sorbent. Infrared and Raman spectra confirmed that cadmium removal occurred via adsorption to -OH functional groups.

Manganese accumulation in plants of the mining zone of Hidalgo, Mexico.

Soil, sediments, water and plant samples from the mining zone of Molango were collected and analyzed and Mn-tolerant and Mn-accumulator plants were identified. Soil and sediments presented moderately alkaline and reducing conditions, a normal electrical conductivity, a sandy texture and medium-to-high cation exchange capacities. These properties favored the presence of Mn(2+), which is the form most easily assimilated by plants, and the total Mn concentration (11,637-106,104 mg kg(-1) dried weight, DW) was at phytotoxic level. Water was also an important Mn source. Equisetum hyemale and Telypteris kunthii survived in the presence of such Mn concentrations using an exclusion strategy, while Cnidoscolus multilobus, Platanus mexicana, Solanum diversifolium, Asclepius curassavica L. and Pluchea sympitifolia employed an accumulation strategy. These plants could be useful to re-vegetate and stabilize Mn tailings in order to decrease the erosion effects.

A method for measuring the anoxic biodegradability under denitrifying conditions.

A test for assessing the anoxic biodegradability of organic compounds under denitrifying conditions is proposed. The method is based on the recovery and quantification of the CO2 produced, which is evidence of complete biodegradation of the test compound (added as the sole carbon source). The tests were carried out in a mineral medium, with nitrate as electron acceptor. Whole lake sediments, sediment extracts and a commercial inoculum were assayed as a possible inoculum source by means of glucose biodegradability tests. It was found that the sediment extracts constitute a suitable and environmentally-relevant inoculum source, since they add non-significant amounts of carbon to the tests. Two xenobiotic compounds, namely, aniline and phenol, were tested in the aforementioned conditions as well as in a standard aerobic biodegradability test. Both aniline and phenol attained a biodegradation level higher than 60% in a short time period (<28 days) and thus can be considered as readily biodegradable in denitrifying environments. Nevertheless, the kinetics obtained in the anoxic test were slower than in aerobic conditions, and even suggested the accumulation of intermediate metabolites in the case of phenol. The results of this study indicate that the fate of xenobiotic compounds under anoxic conditions differs from that observed in an oxic environment, and therefore it should be considered by standard biodegradability testing procedures.