Beneficial Interactive Effects Provided by an Arbuscular Mycorrhizal Fungi and Yeast on the Growth of Oenothera picensis Established on Cu Mine Tailings.

Phytoremediation, an environmentally friendly and sustainable approach for addressing Cu-contaminated environments, remains underutilized in mine tailings. Arbuscular mycorrhizal fungi (AMF) play a vital role in reducing Cu levels in plants through various mechanisms, including glomalin stabilization, immobilization within fungal structures, and enhancing plant tolerance to oxidative stress. Yeasts also contribute to plant growth and metal tolerance by producing phytohormones, solubilizing phosphates, generating exopolysaccharides, and facilitating AMF colonization. This study aimed to assess the impact of AMF and yeast inoculation on the growth and antioxidant response of Oenothera picensis plants growing in Cu mine tailings amended with compost. Plants were either non-inoculated (NY) or inoculated with Meyerozyma guilliermondii (MG), Rhodotorula mucilaginosa (RM), or a combination of both (MIX). Plants were also inoculated with Claroideoglomus claroideum (CC), while others remained non-AMF inoculated (NM). The results indicated significantly higher shoot biomass in the MG-NM treatment, showing a 3.4-fold increase compared to the NY-NM treatment. The MG-CC treatment exhibited the most substantial increase in root biomass, reaching 5-fold that in the NY-NM treatment. Co-inoculation of AMF and yeast influenced antioxidant activity, particularly catalase and ascorbate peroxidase. Furthermore, AMF and yeast inoculation individually led to a 2-fold decrease in total phenols in the roots. Yeast inoculation notably reduced non-enzymatic antioxidant activity in the ABTS and CUPRAC assays. Both AMF and yeast inoculation promoted the production of photosynthetic pigments, further emphasizing their importance in phytoremediation programs for mine tailings.

Phytostabilization of trace elements and 13C isotope composition of Atriplex atacamensis Phil. cultivated in mine tailings treated with organic amendments.

Mining generates large quantities of mineral processing wastes that are typically stored in mine tailings (MT) ponds. Long-term exposure of the surrounding areas to the material from the tailings ponds has been reported to have adverse effects on both human health and the environment. The purpose of this study was to evaluate the ability of Atriplex atacamensis Phil. to phytostabilize metals (Cu, Fe, Mn, and Zn) and sulfur (S) when grown directly on mine tailings with and without compost (C) and humic substance (HS). The stress status of A. atacamensis Phil. was also evaluated through the 13C isotopic composition of bulk leaves. A 120-day greenhouse experiment was conducted and three treatments were evaluated: (i) MT without any amendments (control), (ii) MT + C (dose: 89 ton ha-1), and (iii) MT + HS (0.72 ton ha-1). Mine tailings material exhibited low salinity, alkaline pH, high extractable S-SO4 concentrations, and low fertility; total Fe, Mn, and Zn concentrations were within the reference range for mine tailings, but total Cu concentrations were high at 1860 ± 236 mg kg-1. The HS had higher pH, EC, CEC, and available concentrations of N, P, and K than compost, while S-SO4 concentrations were similar in both amendments. 13C NMR analysis showed that the HS contained more alkyl, aromatic, and phenolic groups, while the compost was dominated by O-alkyl and carboxyl groups. At the end of the experiment, the MT + C treatment achieved a significant decrease in Cu, Fe, and Mn concentrations in the roots and aboveground parts of A. atacamensis Phil. and an increase in Zn values in both tissues. Both amendments increased the sulfur content in the aboveground parts, while metal concentrations under the HS treatment proved similar to control. Furthermore, the δ13CV-PDB values obtained in this study indicate that the organic amendments did not cause additional physiological stress to the plants compared to the MT treatment. Overall, A. atacamensis Phil. was shown to have the ability to phytostabilize metals and sulfur, making it a potential candidate species for in situ evaluation of the phytostabilization process on mine tailings.

Interactive effect of compost application and inoculation with the fungus Claroideoglomus claroideum in Oenothera picensis plants growing in mine tailings.

Different techniques have been developed for the remediation of Cu contaminated soils, being the phytoremediation a sustainable and environmentally friendly strategy, but its use in mine tailings is scarce. Arbuscular mycorrhizal fungi (AMF) can decrease the Cu concentration in plants by favouring the stabilization of this metal through different mechanisms such as the production of glomalin, immobilization in the fungal wall of hyphae and spores, and the storage of Cu in vacuoles. Additionally, the use of organic amendments promotes the beneficial effects produced by AMF and improves plant growth. Based on the above, the aim of this study was to determine the effect of AMF inoculation and compost application at different doses on the growth of Oenothera picensis in a Cu mine tailing. One group of plants were inoculated with Claroideoglomus claroideum (CC) and other was non-inoculated (NM). Both CC and NM were grown for two month under greenhouse conditions in pots with the Cu mine tailing, which also had increasing compost doses (0%, 2.5%, 5%, and 10%). Results showed greater biomass production of O. picensis by CC up to 2-fold compared with NM. This effect was improved by the compost addition, especially at doses of 5% and 10%. Therefore, the increase of mycorrhizal and nutritional parameters in O. picensis, and the decreasing of Cu availability in the mine tailing, promoted the production of photosynthetic pigments together with the plant growth, which is of importance to accomplish phytoremediation programs in Cu mine tailings.

Alteration of enzyme activities and functional diversity of a soil contaminated with copper and arsenic.

Copper (Cu) mining has to address a critical environmental issue related to the disposal of heavy metals and metalloids (HMs). Due to their deleterious effects on living organisms, Cu and arsenic (As) have gained global attention, and thus their monitoring in the environment is an important task. The aims of this study were: 1) to evaluate the alteration of soil enzyme activities (EAs) and soil microbial functional diversity with Cu/As contamination, and 2) to select the most reliable biochemical indicators of Cu/As contamination. A twelve-week soil experiment was performed with four increasing levels of Cu, As, and Cu/As from 150/15 to 1000/100 mg Cu/As kg-1. Soil enzyme activities and soil community-level physiological profile (CLPP) using MicroResp™ were measured during the experiment. Results showed reduced EAs over time with increasing Cu and Cu/As levels. The most Cu-sensitive EAs were dehydrogenase, acid phosphatase, and arylsulfatase, while arginine ammonification might be related to the resilience of soil microbial communities due to its increased activity in the last experimental times. There was no consistent response to As contamination with reduced individual EAs at specific sampling times, being urease the only EA negatively affected by As. MicroResp™ showed reduced carbon (C) substrate utilization with increasing Cu levels indicating a community shift in C acquisition. These results support the use of specific EAs to assess the environmental impact of specific HMs, being also the first assessment of EAs and the use of CLPP (MicroResp™) to study the environmental impact in Cu/As contaminated soils.

Effects of maize cultivation on nitrogen and phosphorus loadings to drainage channels in Central Chile.

There are concerns about the impact of maize cultivation with high applications of nitrogen (N) and phosphorus (P) on water quality in surface waters in Mediterranean Central Chile. This study estimated the contribution of N and P from maize fields to nearby drainage channels and evaluated the effects in water quality. An N and P budget was drawn up for three fields managed with a maize-fallow system, El Maitén (20.7 ha), El Naranjal (14.9 ha) and El Caleuche (4.2 ha), and water quality variables (pH, EC, dissolved oxygen, total solids, turbidity, NO3-N, NH4-N, PO4(3-), COD, total N, total P and sulphate) were monitored in nearby drainage channels. The N and P balances for the three fields indicated a high risk of N and P non-point source pollution, with fertiliser management, soil texture and climate factors determining the temporal variations in water quality parameters. Elevated levels of NH4-N and PO4(3-) in the drainage channels were usually observed during the winter period, while NO3- concentrations did not show a clear tendency. The results suggest that excessive slurry application during winter represents a very high risk of N and P runoff to drainage channels. Overall, great emphasis must be placed on good agronomic management of fields neighbouring drainage channels, including accurately calculating N and P fertiliser rates and establishing mitigation measures.

Estimation of arsenic intake from drinking water and food (raw and cooked) in a rural village of northern Chile. Urine as a biomarker of recent exposure.

The aim of this study was to estimate both the contribution of drinking water and food (raw and cooked) to the total (t-As) and inorganic (i-As) arsenic intake and the exposure of inhabitants of Socaire, a rural village in Chile´s Antofagasta Region, by using urine as biomarker. The i-As intake from food and water was estimated using samples collected between November 2008 and September 2009. A 24-hour dietary recall questionnaire was given to 20 participants. Drinking water, food (raw and cooked) and urine samples were collected directly from the homes where the interviewees lived. The percentage of i-As/t-As in the drinking water that contributed to the total intake was variable (26.8-92.9). Cereals and vegetables are the food groups that contain higher concentrations of i-As. All of the participants interviewed exceeded the reference intake FAO/OMS (149.8 µg∙i-As·day⁻¹) by approximately nine times. The concentration of t-As in urine in each individual ranged from 78 to 459 ng·mL⁻¹. Estimated As intake from drinking water and food was not associated with total urinary As concentration. The results show that both drinking water and food substantially contribute to i-As intake and an increased exposure risk to adult residents in contaminated areas.

Total and inorganic arsenic concentrations in different species of economically important algae harvested from coastal zones of Chile.

Chile is one of the major producers of phytocolloids extracted from seaweed. Multicellular algae are considered to be primary accumulators of arsenic. We analyzed 14 species of algae belonging to the groups Rhodophyceae (10), Phaeophyceae (3) and Chlorophyceae (1) from different coastal zones of Chile in 2003-2004. Dry ashing mineralization (for total As) and acid digestion (for inorganic As) together with quantification by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) were employed. In general, total arsenic concentrations varied between 3.0 and 68 mg kg(-1), whereas inorganic arsenic concentrations ranged between 0.15 and 1.06 mg kg(-1). The algal species Durvillaea antarctica and Porphyra columbina, used for direct human consumption, did not have inorganic arsenic levels that represent a health risk to consumers. Among species used for phytocolloids production, such as Macrocystis piryfera, Gracilaria chilensis and Gigartina skottsbergii, observed levels of inorganic arsenic were greater than 1 mg kg(-1), the limit value established by the regulations of some countries. Among the 14 species of algae tested, inorganic arsenic levels were between 0.8% and 13% of the total arsenic concentrations; that is, arsenic present in these algae was found primarily as organic arsenic.