Heavy metal extraction from soils is one of the functions of plants which is widely studied and applied worldwide. However, little is known to what extent medicinal plants can accumulate these metals and cause problems to human health. This study aimed to evaluate the accumulation of heavy metal/loid in plant tissues, nutritional imbalance, and the effect of heavy metal concentrations in soil on the medicinal plants. The experiment was conducted in a factorial scheme with three contaminated soil samples and a soil sample from an uncontaminated field and three medicinal species: Cynara scolymus, Ocimum basilicum, and Rosmarinus officinalis. The heavy metal content in the biomass increased with increasing soil samples concentration. Biomass production, nutritional imbalance by nutrients did not show consistent results according to soil contamination criteria and are not good indicators of heavy metals presence in plant tissues, since they did not allow predicting the presence of metal in the plants, due to the different behavior of elements and plant species. There was a high concentration of Cd, Cr, Pb, and As and micronutrients Fe, Zn, and Cu in the plant tissues, above the limits recommended by the World Health Organization. Therefore, as the components of C. scolymus, O. basilicum, and R. officinaliss are used to prepare teas, condiments, or consumed raw, coupled with the ability of such species to concentrate toxic metals, the continued use of these plant products containing these metals can pose a potential health concern.

By using the activated carbon obtained from Citrullus lanatus rind by zinc chloride activation, methylene blue (MB) removal from aqueous solutions was studied, and the adsorption mechanism was solved through Weber-Morris intraparticle diffusion model, Bangham model, Boyd model, Fourier transform infrared spectra, and scanning electron microscopy. The effects of adsorption parameters (adsorbent concentration, temperature, initial dye concentration, and pH) were investigated. The equilibrium data of MB adsorption were described by applying the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The obtained results from adsorption isotherms indicated that Langmuir model is the best-fitted model with the maximum adsorption capacities of 231.48, 243.90, 244.50, and 259.74 mg/g at 25, 35, 45, and 55 °C, respectively. The analysis of the kinetic data by pseudo-first-order, pseudo-second-order, and Elovich models displayed that MB adsorption followed pseudo-second-order model. Also, the date obtained from intraparticle diffusion model, Bangham model, and Boyd model presented that intraparticle diffusion, pore diffusion, and film diffusion played significant role in MB adsorption. The thermodynamic studies demonstrated that MB adsorption onto the activated carbon obtained from C. lanatus rind was physical, spontaneous, feasible, and endothermic. Thus, the activated carbon prepared from C. lanatus rind has been an efficient adsorbent for MB removal from an aqueous solution. Graphical Abstract ᅟ

The changes of soil bacterial biomass and community composition were monitored in a simulated nitrogen (N) deposition experiment during 4 years of Cunninghamia lanceolata growth in a plantation site in southern China. The experimental design included two N forms (NH₄Cl and KNO₃) and five levels of N deposition (0, 20, 40, 60, 80 kg N ha⁻¹) for 2 years. Research into the bacterial population was conducted using plate count, phospholipid fatty acid (PLFA) composition, and 16Sr DNA gene-based high-throughput pyrosequencing methods. The results of plate count and PLFA analysis indicated that ammonium (NH₄⁺) addition increased bacterial number and biomass, whereas nitrate (NO₃⁻) addition decreased these values. The high-throughput sequencing showed that N deposition of the two N forms inhibited the growth of bacteria compared with control plots, and the changing trend was related to the NH₄⁺-N/NO₃⁻-N ratio of soil. When the N deposition dose exceeded 20 kg N ha⁻¹, there was a significant effect on cultured bacteria counts and bacterial biomass. When examining the bacterial community, we observed 22 bacterial phyla of which Proteobacteria, Acidobacteria, and Actinobacteria were dominant. Acidobacteria abundance was higher in NH₄⁺ treatments than NO₃⁻ treatments. When the rates of NH₄⁺ deposition increased, Acidobacteria abundance decreased; however, it showed a positive correlation in NO₃⁻ treatments. The bacterial cluster structures were significantly different between different N addition rates in the NO₃⁻-treated plots. This research will provide data support to addressing the negative influences of nitrogen deposition and provide reference for soil management.

China's Sloping Land Conversion Program (SLCP) was designed to restore perennial plant cover on sloping land in western China, in part to protect the Three Gorges Reservoir (TGR). In this study, we examined use of white mulberry (Morus alba L.) in the SLCP to protect water quality and conserve soil. We established nine runoff monitoring plots divided among three categories (vegetable farming, fallow control, and mulberry plantation) on a bank of the Liangtan River situated at the western margin of the TGR. The land had been used previously by farmers for growing vegetables. We found that soil loss and surface water runoff were lowest in the mulberry plots and highest in the vegetable plots. We used inductively coupled plasma atomic emission spectroscopy (ICP-AES) to assess the concentration of selected heavy metal pollution indicators (Zn, Hg, As, Ni, Pb, Cr, Cd, and Cu) in the monitoring plot soils at the beginning of the experiment in May 2009. The heavy metals were assessed again at the end of the experiment in October 2012, and we found that the concentrations of these pollutants had been reduced in all fallow and mulberry plots, and to the greatest extent in the mulberry plots. We found that levels of Hg, Pb, and Cu increased in the vegetable plots. For these reasons, we conclude that riparian mulberry plantations are useful for reducing rapid runoff of storm water, conserving soil, and sequestering heavy metal pollutants in the TGR region.

We evaluated the biogeochemical processes occurring in the rhizosphere of different native plants growing spontaneously in a copper-contaminated soil in an abandoned mine site in NE Brazil. We also assessed the effects that these processes have on copper mobility and toxicity and discuss the potential use of the plants as pioneer species in restoration programs. For these purposes, we determined chemical (pH, macronutrients, % TOC, and % TIC) and mineralogical (XRD) properties in both rhizosphere and nonrhizosphere soils (bulk soil), and we used the sequential extraction method (SEM) to extract copper from both soils. The study findings show that the plants have greatly altered the physicochemical characteristics of the soil that is directly influenced by their roots. Different plant species appear to act through different processes, thus altering various soil components and affecting the biogeodynamic cycling of essential nutrients and copper. The changes in the physical-chemical characteristics of the rhizosphere affected copper dynamics, mainly manifested as significantly lower concentrations of potentially bioavailable copper, i.e., exchangeable and carbonate-associated copper, in this soil fraction. The concentration of copper associated with noncrystalline Fe oxides was also higher in the rhizosphere, thus enhancing the immobilization and probably minimizing the risks of copper toxicity and mobility. The biogeochemical processes observed in the rhizosphere of the species under study seem to indicate that the plants promote phytostabilization of copper in their rhizosphere zone, and they thus show desirable characteristics for use in phytoremediation programs.

Maize (Zea mays) has low Cd accumulation in grains and a high biomass compared to other crops. The capacities for Cd accumulation in different maize cultivars are, however, not fully understood. To reduce human health risk from maize grown in Cd-contaminated soil and to provide promising maize cultivars for the phytoremediation of Cd-polluted soil, a field experiment was conducted to screen low-Cd- and high-Cd-accumulation maize cultivars by evaluating the yield, Cd uptake, translocation, and accumulation differences among 19 maize cultivars. There were differences in straw dry weight (DW), root DW, and yield among the 19 cultivars. The cultivars Yudan19, Zhengda999, and Xianyu508 had a higher production compared to that of the other cultivars. The Cd concentrations in the roots were much higher than those in the straws and grains in all cultivars. The Cd accumulation factors (AFS) decreased in the order of accumulation factors in root (AFᵣₛ) > accumulation factors in straw (AFₛₛ) > accumulation factors in grain (AFgₛ). The Cd translocation factors (TFs) from root to straw (TFᵣₛ) were significantly (p < 0.05) larger than those from straw to grain (TFₛg) among all of the cultivars. The TFₛ for all of the cultivars was less than 1, and the lowest TFₛg (0.23) was found in cultivar Xiangyongdan3. The correlation analysis indicated that Cd concentrations in straws showed a significant (p < 0.01) as well as positive correlation with TFᵣₛ while a negative correlation with TFₛg (p < 0.01). Moreover, Cd accumulation in different tissues decreased in the order straw > grain > root. Among the 19 maize cultivars, Jixiang2118 and Kangnong18 accumulated the highest Cd amount in the aboveground tissues, and the corresponding values were 7,206.51 and 6,598.68 mg hm⁻², respectively. A hierarchical cluster analysis based on the Cd concentrations in grains and straws classified the 19 maize cultivars into four and two groups for a 0.4 minimum distance between clusters, respectively. Yudan19, Zhengda999, and Xianyu508 can be classified into one group in which low Cd in grains meeting the Cd tolerance limit in foods set by China National Standard, suggesting that those cultivars are safety for food and human health. However, Jixiang2118 and Kangnong18 can be classified as another group with potential application for phytoremediation in slightly or moderately Cd-polluted soil because of the high Cd accumulation in the aboveground tissues.

The accidental release of organic contaminants in the form of non-aqueous phase liquids (NAPLs) into the subsurface is a widespread and challenging environmental problem. Successful remediation of sites contaminated with NAPLs is essential for the protection of human health and the environment. One technology that has received significant attention is the injection of chemical additives (such as cosolvents) upgradient of the NAPL zone for the enhanced dissolution and mobilization of the NAPL mass. A key process influencing the effectiveness of NAPL mass recovery is the interphase mass transfer which is the transfer of components across the interface separating the different phases. In this work, we examine the impact of cosolvent content, flushing solution velocity, and injection pattern (continuous versus intermittent) on the interphase mass transfer rate. A series of flushing experiments were conducted using an intermediate-scale tank which allows for the impact of density variations on DNAPL mobility. The target DNAPL selected in this study was trichloroethylene while the flushing solutions consisted of ethanol–water mixtures with ethanol contents ranging from 0 to 50% by volume. The experimental results were also modeled using the UTCHEM multiphase flow simulator that was modified to model cosolvent flushing. Results show that the observed interphase mass transfer coefficient, expressed as a modified Sherwood number, was much lower than predicted based on published correlations developed under idealized conditions. Moreover, interphase mass transfer rate decreased with time, indicating that a single interphase mass transfer coefficient cannot accurately model the entire flushing solution. The data also suggest that the interphase mass transfer coefficient is dependent on cosolvent content.

The influence of the presence of the so-called seed particles on the emission rate of Tris (1-chloroisopropyl) phosphate (TCIPP) from polyisocyanurate (PIR) insulation boards was investigated in this study. Two Field and Laboratory Emission Test cells (FLEC) were placed on the surface of the same PIR board and respectively supplied with clean air (reference FLEC) and air containing laboratory-generated soot particles (test FLEC). The behavior of the area-specific emission rates (SER A) over a time period of 10 days was studied by measuring the total (gas + particles) concentrations of TCIPP at the exhaust of each FLEC. The estimated SER A of TCIPP from the PIR board at the quasi-static equilibrium were found to be 0.82 μg m⁻² h⁻¹ in the absence of seed particles, while the addition of soot particles led to SER A of 2.16 μg m⁻² h⁻¹. This indicates an increase of the SER A of TCIPP from the PIR board with a factor of 3 in the presence of soot particles. The TCIPP partition coefficient to soot particles at the quasi-static equilibrium was 0.022 ± 0.012 m³ μg⁻¹. In the next step, the influence of real-life particles on TCIPP emission rates was investigated by supplying the test FLEC with air from a professional kitchen where mainly frying and baking activities took place. Similar to the reference FLEC outcomes, SER A was also found to increase in this real-life experiment over a time period of 20 days by a factor 3 in the presence of particles generated during cooking activities. The median value of estimated particle–gas coefficient for this test was 0.062 ± 0.037 m³ μg⁻¹.

Ore mining and processing have greatly altered ecosystems, often limiting their capacity to provide ecosystem services critical to our survival. The soil environments of two abandoned uranium mines were chosen to analyze the effects of long-term uranium and heavy metal contamination on soil microbial communities using dehydrogenase and phosphatase activities as indicators of metal stress. The levels of soil contamination were low, ranging from ‘precaution’ to ‘moderate’, calculated as Nemerow index. Multivariate analyses of enzyme activities revealed the following: (i) spatial pattern of microbial endpoints where the more contaminated soils had higher dehydrogenase and phosphatase activities, (ii) biological grouping of soils depended on both the level of soil contamination and management practice, (iii) significant correlations between both dehydrogenase and alkaline phosphatase activities and soil organic matter and metals (Cd, Co, Cr, and Zn, but not U), and (iv) multiple relationships between the alkaline than the acid phosphatase and the environmental factors. The results showed an evidence of microbial tolerance and adaptation to the soil contamination established during the long-term metal exposure and the key role of soil organic matter in maintaining high microbial enzyme activities and mitigating the metal toxicity. Additionally, the results suggested that the soil microbial communities are able to reduce the metal stress by intensive phosphatase synthesis, benefiting a passive environmental remediation and provision of vital ecosystem services.

The increasing use of herbicides in sugarcane production has increased environmental concern regarding the fate of these compounds, especially when they are used in mixtures. Among the various processes that determine the behavior of molecules in the environment, leaching stands out. In this context, the aim of this study was to evaluate the leaching of a mixture of hexazinone, sulfometuron-methyl, and diuron in soils with contrasting textures. A completely randomized experimental design containing three replications in a 2 × 6 factorial arrangement was used, with two soils (alfisol–Paleudult, sandy clay texture and ultisol–typic Hapludalf, sandy loam texture) and six depths (0–0.05, 0.05–0.10, 0.10–0.15, 0.15–0.20, 0.20–0.25, and 0.25–0.30 m). Three glass columns of 50 cm were used for each soil. The dose used was 391.0 + 33.35 + 1386.9 g a.i. ha⁻¹ of hexazinone, sulfometuron-methyl and diuron, respectively. After applying the mixture to the top of each column, rainfall simulation with 200 mm of 0.01 mol L⁻¹ CaCl₂ solution was applied for 48 h. The leachates were collected at 6, 12, 24, 36, and 48 h. The chromatographic determinations of the herbicides were performed by high-performance liquid chromatography (HPLC) with a UV-Vis detector. For hexazinone, the highest percentage recovery in the soil with a sandy clay texture occurred at a depth of 0.10–0.15 m, with 40 % recovered, while in the soil with a sandy loam texture, the most part was recovered at a depth of 0.25–0.30 m. Diuron demonstrated little mobility in the soil and was detected in most cases only in the surface layer (up to 0.10 m) in both soils. Sulfometuron-methyl, in soil with a sandy clay texture, was detected to a depth of 0.15–0.20 m with the highest concentration found at a depth of 0–0.05 m, while in sandy loam soil, a higher concentration was found at a depth of 0.10–0.15 m; this herbicide was detected down to 0.25–0.30 m. These results show that the soil texture directly influences the leaching of hexazinone, sulfometuron-methyl, and diuron.