Browsing by Author "Neaman, Alexander"

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    An Assessment of the Feasibility of Phytoextraction for the Stripping of Bioavailable Metals from Contaminated Soils
    (2022-12-29) Santa‐Cruz, Javier; Robinson, Brett; Krutyakov, Yurii A.; Shapoval, Olga A.; Peñaloza, Patricia; Yáñez, Carolina; Neaman, Alexander
    Phytoextraction has been proposed in many papers as a low-cost method for remediating contaminated soil. However, if national regulation is based on total metal(loid) concentrations in soil, phytoextraction is generally infeasible because of the long time required for remediation. Assessing phytoextraction requires determination of the dynamic rate of metal removal from soil. Phytoextraction may be feasible if the main goal is to reduce the soluble fraction of the metal(loid) with the goal of reducing bioavailability. However, it has been reported that there is a large mass balance mismatch between the reduction of the soluble metal fraction in contaminated soil and metal uptake by plants. Several studies report that the decrease of soluble fraction of metals in soil is higher than can be accounted for by plant uptake. In other words, studies generally overestimate the feasibility of bioavailable contaminant stripping. Therefore, a more rigorous approach is advisable to ensure that papers on bioavailable contaminant stripping include relevant information on mass balances. Furthermore, to implement the concept of bioavailable contaminant stripping, regulations must distinguish between the bioavailable fraction and the total metal concentration in soil.
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    Chilean regulations on metal-polluted soils: The need to advance fromadapting foreign laws towards developing sovereign legislation
    (Environmental Research, 2020) Neaman, Alexander; Valenzuela, Patricio; Tapia-Gatica, Jaime; Selles, Iván; Novoselov, Alexey A.; Elvira A. Dovletyarova; Yáñez, Carolina; Krutyakov, Yurii A.; Stuckey, Jason W.
    Chile as a major international Cu producer faces serious soil contamination issues in mining areas. CurrentlyChile does not have any specific law governing the maximum permissible concentrations of metals in soils toprotect ecosystems and human health. Chile heavily relies on the use of environmental laws of 14 foreigncountries; the choice of the country depends on the similarity of its environmental conditions with those in Chile.In this study, we used an online database to compare the similarity of Chilean rocks to those in foreign countries.Likewise, we performed soil sampling and determined the background concentrations of Cu, As, Pb, and Zn insoils of the Aconcagua basin, the largest river basin in the Valparaiso Region of central Chile. The results showedthat geochemical patterns in Chile have the greatest resemblance to New Zealand, Mexico, and Italy. Thebackground Cu concentration in the Aconcagua basin (134 mg kg−1) exceeded the legislated limits of NewZealand (100 mg kg−1) and Italy (120 mg kg−1), whereas the background Zn concentration (200 mg kg−1)exceeded the legislated limit of Italy (150 mg kg−1). Due to the elevated natural abundance of Cu and Zn inChile, international laws should not be applied in Chile for the assessment of soil contamination. In addition, weassessed ecological risk using the results of our previous studies obtained by analyzing nativefield-contaminatedsoils of the Valparaiso region. In the Aconcagua basin, Cu posed high risk for plants in 11% of the samples,whereas As posed high risk for earthworms in 48% of the samples. We suggest that future studies are required tosearch for other organisms that can serve as biomarkers of metal toxicity because our previous studies werelimited to plants and earthworms. Importantly, As posed high risk to human health in 25% of the samples in ourstudy. There is a need for future studies to demonstrate empirically an association between soil As and children'sblood As in order to establish the national threshold values of soil As to protect human health. We conclude thatthere is an urgent need in Chile to advance from the current approach of adapting foreign laws to developingChilean sovereign environmental legislation.
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    Impact of Mother Plant Saline Stress on the Agronomical Qualityof Pepper Seeds
    (Journal of Soil Science and Plant Nutrition, 2020) Pezo, Carolina; Valdebenito, Samuel; Flores, Fernanda; Oyanedel, Eduardo; Vidal, Kooichi; Neaman, Alexander; Peñaloza, Patricia
    Seed quality has been an important factor in achieving high germination and uniform growth rates in agricultural crops.Meanwhile, pepper plants are moderately sensitive to salt stress at electrical conductivity (EC) in the nutrient solution in therange of 1.2–3.0 dS m−1. We are unaware of any studies regarding the effects of mother plant saline stress on the agronomicalquality of pepper seeds. We assessed the effects of three levels of electrical conductivity of the nutrient solution used for motherplant fertigation (2.2, 3.5, and 4.5 dS m−1) on the agronomical quality of pepper seeds (Capsicum annuumL. var. CaliforniaWonder). We have analyzed the following seed quality traits: (1) size and weight of seeds and number of seeds per fruit, (2) seedgermination and vigor, and (3) chemical composition and histological features of mature seeds. The electrical conductivitytreatment of 3.5 dS m−1caused a statistically significant reduction in the seed size and vigor, as well as partial histologicaldamage to seed endosperm. Moreover, the electrical conductivity treatment of 4.5 dS m−1caused further reduction in the seedagronomical quality and generalized histological damage to seed endosperm. The electrical conductivity of the nutrient solutionused for the fertigation of mother pepper plants should be below 3.5 dS m−1. Future studies should be performed to better gaugethe effect of nutrient solutions with electrical conductivity in the range of 2.2–3.5 dS m−1on the seed quality traits.
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    Thresholds of Metal and Metalloid Toxicity In Field-Collected Anthropogenically Contaminated Soils: A Review
    (2021-07-01) Santa Cruz, Javier; Peñaloza, Patricia; Korneykova, Maria V.; Neaman, Alexander
    Ecotoxicological studies of soil metal toxicity conventionally rely on the use of uncontaminated soils gradually enriched with metals in the form of soluble salts. Although this method is very useful in many ways, it is continually complicated by the difficulty of extrapolating laboratory results to actual field-collected soils exposed to decades of contamination. Although many studies emphasize the importance of using field-contaminated soils for toxicity bioassays, the number of studies actually conducted based on this premise is relatively small. This review provides an in-depth recompilation of data on metal toxicity thresholds in field-contaminated soils. We have summarized the EC10, EC25, and EC50 values for metals, i.e., values of metal concentrations that reduce the response of specific organisms by 10%, 25%, and 50% of the value in uncontaminated soils. In our summary, most studies show that total metal content can predict organismal responses as well as bioavailable fractions. These results are consistent with the intensity/capacity/quantity concept proposed for plant nutrient uptake. In addition, microorganisms are thought to be more sensitive to metals than plants and invertebrates. However, our analysis shows that there is no statistically significant difference between the sensitivity of microorganisms and other organisms (plants and invertebrates) to any metal or metal pool. We expect that this information will be useful for environmental assessment and soil quality decisions. Finally, we encourage future studies to analyze dose-effect relationships in native field-collected soils with varying degrees of metal contamination from long-term anthropogenic pollution.