Marcos Eduardo Rosas-Ramírez

Native plant species show significant promise for the remediation and rehabilitation of mine tailings contaminated with heavy metals (HM). Nonetheless, the harmful impact of HM can decrease plant survival, growth and reproduction, thereby diminishing the effectiveness of phytoremediation. Consequently, incorporating organic amendments into mine tailings, like biochar, can promote plant growth, decreasing the bioavailability of HM and their eventual potential to alter the food chain. This study aims to evaluate the capability of coconut fiber biochar in combination with Sanvitalia procumbens to phytostabilize HM in mine tailings by analyzing the effect of coconut fiber biochar on HM bioaccumulation levels (roots and leaves), as well as on morphological, physiological, and genotoxic parameters of S. procumbens grown in mine tailing substrate and mine tailing/biochar. Also, a physicochemical analysis of coconut fiber biochar was conducted. This research was conducted over 100 days on plants grown in greenhouse settings using two different substrates (mine tailing and agrolite [75/25 v/v] and mine tailing and coconut fiber biochar [75/25 v/v]). Every 25 days, 12 plants were selected per treatment for analysis. The bioaccumulation pattern exhibited by S. procumbens was Zn > Pb > Cu > Cd, in root and leaf tissues for both treatments. S. procumbes grown in mine tailing/biochar substrate showed the lowest HM bioaccumulation levels in both tissues in comparison to mine tailing substrate: Zn from 2.95 to 2.50 times lower; Pb 3.04 to 2.82; Cu 3.10 to 2.12; and Zn 2.12 to 3.00 in roots and leaves, respectively. The coconut fiber biochar was rich in functional groups, such as carboxyl and hydroxyl groups, which could favor HM adsorption. Immobilization percentage of HM by coconut fiber biochar showed the following pattern: Pb (66.33%) > Zn (64.50%) > Cu (62.82%) > Cd (55.39%). Incorporating coconut fiber biochar as an amendment improves HM phytostabilization efficiency by reducing their bioaccumulation, increasing biomass production and chlorophyll concentration, and reducing genetic damage levels. This strategy represents a sustainable approach towards reducing the ecological risk of HM biomagnification, alleviating the adverse effects of HM exposure on ecosystem health.

Water pollution by metals is a global environmental problem. In riparian ecosystems, metal pollution generates adverse effects on organisms and reduces water quality. The Cuautla River is of great ecological relevance and an important water supplier. However, it is polluted by multiple wastewater discharges from different origins, with toxic metals being the main pollutants. Therefore, environmental monitoring strategies based on bioindicator species are necessary to evaluate the ecosystem health of riparian ecosystems. Pithecellobium dulce (Roxb.) Benth is a tree species native to Mexico, widely distributed including in riparian ecosystems, and it is also established in contaminated sites. In this study, Cd, Cu, Pb, and Zn concentrations in water and sediment and in leaf and bark of adult P. dulce trees established in six sampling sites along the Cuautla’s riverbed were determined. Likewise, the genotoxic damage derived from metal exposure to leaves was evaluated. The results evidenced the presence of Cd and Pb in water and Cd, Cu, Pb, and Zn in sediment. P. dulce registered high levels of Cu, Pb, and Zn in both leaf and bark, showing higher concentrations in leaf than in bark. In addition, the greater the concentration of Pb in leaves, the greater the genotoxic damage observed, while the concentration of Cu and Zn did not show a relationship with the genotoxic damage in leaves. Overall, Cu and Pb concentrations in leaves enabled us to detect pollution gradients for these metals in water and sediment from the sampling sites. Due to its wide geographic distribution, establishment in polluted sites, and metal absorption capacity, P. dulce can be considered a bioindicator species for environmental health studies in riparian ecosystems contaminated with metals.

The increasing demand for mineral resources has generated mine tailings with heavy metals (HM) that negatively impact human and ecosystem health. Therefore, it is necessary to implement strategies that promote the immobilization or elimination of HM, like phytoremediation. However, the toxic effect of metals may affect plant establishment, growth, and fitness, reducing phytoremediation efficiency. Therefore, adding organic amendments to mine tailings, such as biochar, can favor the establishment of plants, reducing the bioavailability of HM and its subsequent incorporation into the food chain. Here, we evaluated HM bioaccumulation, biomass, morphological characters, chlorophyll content, and genotoxic damage in the herbaceous Crotalaria pumila to assess its potential for phytostabilization of HM in mine tailings. The study was carried out for 100 days on plants developed under greenhouse conditions under two treatments (tailing substrate and 75% tailing/25% coconut fiber biochar substrate); every 25 days, 12 plants were selected per treatment. C. pumila registered the following bioaccumulation patterns: Pb > Zn > Cu > Cd in root and in leaf tissues. Furthermore, the results showed that individuals that grew on mine tailing substrate bioaccumulated many times more metals (Zn: 2.1, Cu: 1.8, Cd: 5.0, Pb: 3.0) and showed higher genetic damage levels (1.5 times higher) compared to individuals grown on mine tailing substrate with biochar. In contrast, individuals grown on mine tailing substrate with biochar documented higher chlorophyll a and b content (1.1 times more, for both), as well as higher biomass (1.5 times more). Therefore, adding coconut fiber biochar to mine tailing has a positive effect on the establishment and development of C. pumila individuals with the potential to phytoextract and phytostabilize HM from polluted soils. Our results suggest that the binomial hyperaccumulator plant in combination with this particular biochar is an excellent system to phytostabilize soils contaminated with HM.

Glyphosate is a broad-spectrum herbicide extensively used worldwide to eliminate weeds in agricultural areas. Since its market introduction in the 70’s, the levels of glyphosate agricultural use have increased, mainly due to the introduction of glyphosate-resistant transgenic crops in the 90’s. Glyphosate presence in the environment causes pollution, and recent findings have proposed that glyphosate exposure causes adverse effects in different organisms, including humans. In 2015, glyphosate was classified as a probable carcinogen chemical, and several other human health effects have been documented since. Environmental pollution and human health threats derived from glyphosate intensive use require the development of alternatives for its elimination and proper treatment. Bioremediation has been proposed as a suitable alternative for the treatment of glyphosate-related pollution, and several microorganisms have great potential for the biodegradation of this herbicide. The present review highlights the environmental and human health impacts related to glyphosate pollution, the proposed alternatives for its elimination through physicochemical and biological approaches, and recent studies related to glyphosate biodegradation by bacteria and fungi are also reviewed. Microbial remediation strategies have great potential for glyphosate elimination, however, additional studies are needed to characterize the mechanisms employed by the microorganisms to counteract the adverse effects generated by the glyphosate exposure.