Research on the interaction of microplastics and aquatic organisms has been mainly focused on the evaluation of various impacts on animals while aquatic vascular plants have been so far understudied. In this commentary, we summarized knowledge about interactions of microplastics with aquatic vascular plants and highlighted potential ecological implications. Based on recent research, microplastics have minimal impacts on plants. However, they are strongly attracted to plant tissues, adsorbed, and accumulated by plants. Several mechanisms drive microplastics adsorption and accumulation; the most possibly electrostatic forces, leaf morphology, and presence of periphyton belong among the most important ones. Adsorbed microplastics on plant tissues are easily ingested by herbivores. Plants can thus represent a viable pathway for microplastics to enter aquatic food webs. On the other hand, the strong interactions of microplastics with plants could be used for their phytostabilization and final removal from the environment. Aquatic vascular plants have thus an important role in the behavior and fate of microplastics in aquatic ecosystems, and therefore, they should also be included in the future microplastic research.

Halogenated flame retardants (HFRs) are ubiquitous in the environment, but little information is available about the bioaccumulation of HFRs in mangrove plants. In this study, three mangrove plant species were collected from Futian National Nature Reserve of Shenzhen City, South China to investigate the bioaccumulation of polybrominated diphenyl ethers (PBDEs) and several alternative halogenated flame retardants (AHFRs), including decabromodiphenyl ethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), hexabromobenzene (HBB), pentabromotoluene (PBT), tetrabromop-xylene (pTBX), pentabromoethylbenzene (PBEB) and dechlorane plus (DP). The mean concentrations of PBDEs, DBDPE, BTBPE, pTBX, PBT, PBEB, HBB and DP in mangrove plant species were 2010, 1870, 36.2, 18.7, 40.1, 17.8, 9.68 and 120 pg g⁻¹ dry weight, respectively. PBDEs were the dominant HFRs in mangrove plant tissues, followed by DBDPE. The relative abundance of BDE 209 in three mangrove plant tissues were much lower than those in sediments. Significant negative relationships between log root bioaccumulation factors and log Kₒw, and between log TFᵣ₋ₛ (from root to stem) and log Kₒw were observed, indicating that HFRs with low hydrophobicity were easily absorbed by mangrove roots and stems. A positive correlation between log TFₛ₋ₗ (from stem to leaf) and log Kₒw were found, suggesting that air-leaf exchange may occur in mangrove plants. This study highlights the uptake of HFRs by mangrove plants, which can be used as remediation for HFRs contamination in the environment.

Whether toxicity of silver nanoparticles (AgNPs) to organisms originates from the nanoparticles themselves or from the dissolved Ag-ions is still debated, with the majority of studies claiming that extracellular release of Ag-ions is the main cause of toxicity. The objective of this study was to determine the contributions of both particles and dissolved ions to toxic responses, and to better understand the underlying mechanisms of toxicity. In addition, the pathways of AgNPs exposure to plants might play an important role and therefore are explicitly studied as well. We systematically assessed the phytotoxicity, internalization, biodistribution, and antioxidant responses in lettuce (Lactuca sativa) following root or foliar exposure to AgNPs and ionic Ag at various concentrations. For each endpoint the relative contribution of the particle-specific versus the ionic form was quantified. The results reveal particle-specific toxicity and uptake of AgNPs in lettuce as the relative contribution of particulate Ag accounted for more than 65% to the overall toxicity and the Ag accumulation in whole plant tissues. In addition, particle toxicity is shown to originate from the accumulation of Ag in plants by blocking nutrient transport, while ion toxicity is likely due to the induction of excess ROS production. Root exposure induced higher toxicity than foliar exposure at comparable exposure levels. Ag was found to be taken up and subsequently translocated from the exposed parts of plants to other portions regardless of the exposure pathway. These findings suggest particle related toxicity, and demonstrate that the accumulation and translocation of silver nanoparticles need to be considered in assessment of environmental risks and of food safety following consumption of plants exposed to AgNPs by humans.

Selenium (Se) is an essential micronutrient for animals with a relatively narrow margin between essentiality and toxicity. To evaluate Se removal efficiency by a constructed wetland treatment system and its potential eco-risk, a floating-leaved macrophyte system was constructed, consisting of three main trophic levels. Over 21-d treatment, water Se concentration was gradually reduced by 40.40%, while 24.03% and 74.41% of the removed Se were found in the plant Nymphoides sp. and sediment, respectively. Among plant tissues, roots accumulated the highest Se level, although the greatest total Se was found in stems, followed by leaves, roots and rhizomes. X-ray absorption spectroscopy revealed that 82.65% of the absorbed selenite by the plants was biotransformed to other forms, as organo-Se species accounted for 45.38% of the Se retained in the sediment, which was primarily responsible for the entry of Se into the detritus food chain. The proportion of organo-Se compounds increased with trophic levels from sediments to fish, indicating, instead of direct uptake of selenite, the food chain transfer and biotransformation of Se may serve as a key exposure route for Se in aquatic organisms. When exposed to organo-Se compounds, i.e., SeCys and SeMet, the plants, shrimp and fish tended to accumulate more Se. However, the greater trophic transfer factor was obtained for selenate, leading to higher Se levels accumulated in fish. Overall, in addition to key mechanisms involved in Se removal, our research also provides a much better understanding of the potential eco-risk that may be posed by the floating-leaved plant system for bioremediation of Se via food chain transfer and biotransformation, paving the way for a low eco-toxic treatment system for Se remediation.

Crude oil and its constituents can have adverse effects on ecological and human health when released into the environment. The Canadian Council of Ministers of the Environment (CCME) has developed remedial guidelines and a risk assessment framework for both ecological and human exposure to PHC. One of the assumptions used in the derivation of these guidelines is that plants are unable to take up PHC from contaminated soil and therefore subsequent exposure at higher trophic levels is not a concern. However, various studies suggest that plants are indeed able to take up PHC into their tissues. Consumption of plants is a potential exposure pathway in both ecological (e.g., herbivorous and omnivorous birds, and mammals) and human health risk assessments. If plants can uptake PHC, then the current approach for risk assessment of PHC may underestimate exposures to ecological and human receptors. The present review aims to assess whether or not plants are capable of PHC uptake and accumulation. Twenty-one articles were deemed relevant to the study objective and form the basis of this review. Of the 21 primary research articles, 19 reported detectable PHC and/or its constituents in plant tissues. All but five of the 21 articles were published after the publication of the CCME Canada-Wide Standards. Overall, the present literature review provides some evidence of uptake of PHC and its constituents into plant tissues. Various plant species, including some edible plants, were shown to take up PHC from contaminated soil and aqueous media in both laboratory and field studies. Based on the findings of this review, it is recommended that the soil-plant-wildlife/human pathway should be considered in risk assessments to avoid underestimating exposure and subsequent toxicological risks to humans and wildlife.

Antibiotics are introduced into agricultural fields by the application of manure or biosolids, or via irrigation using reclaimed wastewater. Antibiotics can enter the terrestrial food chains through plant uptake, which forms an alternative pathway for human exposure to antibiotics. However, previous studies mainly focused on detecting residues of the parent antibiotics, while ignoring the identification of antibiotics transformation products in plants. Here, we evaluated the uptake and metabolism of clarithromycin (CLA) and sulfadiazine (SDZ) in lettuce under controlled hydroponic conditions. The antibiotics and their metabolites were identified by ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-QToF-MS/MS) and ultra-performance liquid chromatograph Micromass triple quadrupole mass spectrometry (UPLC−QqQ−MS/MS). The structure of CLA, SDZ and N-acetylated SDZ were confirmed with synthesized standards, verifying the reliability of the identification method. Eight metabolites of CLA and two metabolites of SDZ were detected in both the leaves and roots of lettuce. The metabolites of CLA included phases I and II transformation products, while only phase II metabolites of SDZ were observed in lettuce. The proportion of CLA metabolites was estimated to be greater than 70%, indicating that most of the CLA was metabolized in plant tissues. The proportion of SDZ metabolites was lower than 12% in the leaves and 10% in the roots. Some metabolites might have the ability to increase or acquire antibacterial activity. Therefore, in addition to the parent compounds, metabolites of antibiotics in edible vegetables are also worthy of study for risk assessment and to determine the consequences of long-term exposure.

Phytostabilization of sulfidic PbZn tailing landscapes may be one of interim options of tailings management, but which is limited by acute phytotoxicity of heavy metals in the tailings. The present study aimed to investigate the effectiveness of soluble phosphate (i.e., K2HPO4) in immobilizing soluble Pb, Cd and Zn and lowering their acute phytotoxicity. The addition of soluble phosphate improved the growth of native plants Acacia chisholmii and survival rate of A. ligulata, where the latter exhibited 100% survival rate. This was in contrast to effects of conventional organic amendment in the tailings on metal solubility (e.g., elevated metal levels in porewater) and plant survival (e.g., only 42%). Organic amendment with mulch did not lower the levels of water-soluble Cd, Pb and Zn and their concentrations in plant tissues after 56 days of plant growth in the treatment. In contrast, the tailings amended with K2HPO4 significantly decreased metal concentrations in the porewater and plant tissues by about 80–92% and 56–88%, respectively. The metal immobilization by phosphate was due to the formation of insoluble or sparingly soluble metal (Pb, Cd and Zn)-phosphate minerals in the tailings with circumneutral pH conditions, as revealed by using X-ray diffraction and scanning electron microanalyses. The reduced metal concentrations in roots and shoots of Acacia species after direct root contact with the K2HPO4 amended tailings suggested that metals (i.e., Pb, Cd and Zn) were effectively immobilized by the phosphate treatment of the tailings. These findings indicate that addition of high dosage of soluble phosphate may provide a low cost option to treat sulfidic PbZn tailings for rapid phytostabilization of the tailings surface, as an interim option to manage environmental risks of sulfidic PbZn tailings.

In the Mediterranean ecosystem, wildfires are very frequent and the predicted future with a probable increase of fires could drastically modify the vegetation scenarios. Vegetation fires are an important source of gases and primary emissions of fine carbonaceous particles in the atmosphere. In this paper, we present gaseous and particulate emissions data from the combustion of different plant tissues (needles/leaves, branches and needle/leaf litter), obtained from one conifer (Pinus halepensis) and one deciduous broadleaf tree (Quercus pubescens). Both species are commonly found throughout the Mediterranean area, often subject to wildfires. Experiments were carried out in a combustion chamber continuously sampling emissions throughout the different phases of a fire (pre-ignition, flaming and smoldering). We identified and quantified 83 volatile organic compounds including important carcinogens that can affect human health. CO and CO₂ were the main gaseous species emitted, benzene and toluene were the dominant aromatic hydrocarbons, methyl-vinyl-ketone and methyl-ethyl-ketone were the most abundant measured oxygenated volatile organic compounds. CO₂ and methane emissions peaked during the flaming phase, while the peak of CO emissions occurred during the smoldering phase. Overall, needle/leaf combustion released a greater amount of volatile organic compounds into the atmosphere than the combustion of branches and litter. There were few differences between emissions from the combustion of the two tree species, except for some compounds. The combustion of P. halepensis released a great amount of monoterpenes as α-pinene, β-pinene, p-cymene, sabinene, 3-carene, terpinolene and camphene that are not emitted from the combustion of Q. pubescens. The combustion of branches showed the longest duration of flaming and peak of temperature. Data presented appear crucial for modeling with the intent of understanding the loss of C during different phases of fire and how different typologies of biomass can affect wildfires and their speciation emissions profile.

Antimony (Sb) is a contaminant of increased prevalence in the environment, but there is little knowledge about the mechanisms of its uptake and translocation within plants. Here, we applied for the synchrotron based X-ray absorption near-edge structure (XANES) spectroscopy to analyze the speciation of Sb in roots and shoots of rye grass (Lolium perenne L. Calibra). Seedlings were grown in nutrient solutions to which either antimonite (Sb(III)), antimonate (Sb(V)) or trimethyl-Sb(V) (TMSb) were added. While exposure to Sb(III) led to around 100 times higher Sb accumulation in the roots than the other two treatments, there was no difference in total Sb in the shoots. Antimony taken up in the Sb(III) treatment was mainly found as Sb-thiol complexes (roots: >76% and shoots: 60%), suggesting detoxification reactions with compounds such as glutathione and phytochelatins. No reduction of accumulated Sb(V) was found in the roots, but half of the translocated Sb was reduced to Sb(III) in the Sb(V) treatment. Antimony accumulated in the TMSb treatment remained in the methylated form in the roots. By synchrotron based XANES spectroscopy, we were able to distinguish the major Sb compounds in plant tissue under different Sb treatments. The results help to understand the translocation and transformation of different Sb species in plants after uptake and provide information for risk assessment of plant growth in Sb contaminated soils.

Wheat is one of several cereals that is capable of accumulating higher amounts of Cd in plant tissues. It is important to understand the Cd²⁺ transport processes in roots that result in excess Cd accumulation. Traditional destructive technologies have limited capabilities in analyzing root samples due to methodological limitations, and sometimes may result in false conclusions. The mechanisms of Cd²⁺ uptake into the roots of wheat seedlings (Triticum aestivum L.) were investigated by assessing the impact of various inhibitors and channel blockers on Cd accumulation as well as the real-time net Cd²⁺ flux at roots with the non-destructive scanning ion-selective electrode technique. The P-type ATPase inhibitor Na3VO4 (500 μM) had little effect on Cd uptake (p < 0.05) and the kinetics of transport in the root of wheat, suggesting that Cd²⁺ uptake into wheat root cells is not directly dependent on H⁺ gradients. While, the uncoupler 2,4-dinitrophenol significantly limited Cd²⁺ uptake (p < 0.05) and transport kinetics in the root of wheat, suggesting the existence of metabolic mediation in the Cd²⁺ uptake process by wheat. The Cd content at the whole-plant level in wheat was significantly (p < 0.05) decreased upon pretreatment with the Ca²⁺ channel blockers La³⁺ or Gd³⁺ and Verapamil, but not in case of pretreatment with the K⁺ channel blocker tetraethylammonium (TEA). In addition, the inhibitors of the Ca²⁺ channel, as well as high concentrations of Ca²⁺, reduced the real-time net Cd²⁺ fluxes at the root surface in SIET experiments. These results indicate that Cd²⁺ moves across the plasma lemma of the wheat root via Ca²⁺ channels. In addition, our results suggested a role for protein synthesis in mediating Cd²⁺ uptake and transport by wheat.