Chronic toxicity of PFAS-free AFFF alternatives in terrestrial plant Brassica rapa

Fluorine (F)-free firefighting foams will be replacing per- and polyfluoroalkyl substances (PFAS)-containing aqueous film-forming foams (AFFFs) at U.S. military installations imminently, yet the environmental impacts of F-free foams are largely unknown. Ecotoxicity assessment of F-free foams is urgently needed to avoid replacement regret. In this study, we comparatively assessed phytotoxicity of six F-free formulations and one current short-chain fluorinated AFFF in terrestrial plant Brassica rapa. Five of six F-free formulations exerted higher toxicity than the short-chain AFFF to the growth and reproduction of B. rapa, with 8-51 times and > 10 times lower EC₅₀ values, respectively. Nontargeted analysis indicated the occurrence of transformation products of the test formulations in the above-ground plant tissues. In agreement with their phytotoxicity, the five highly toxic F-free formulations generated more transformation products with higher peak intensities in plant tissues than the two weakly toxic formulations. The most abundant transformation products detected in plant extracts were suspect transformation products derived from diethylene glycol monobutyl ether, a common ingredient of the five toxic formulations. This study provides ecotoxicological data that, combined with data from all related ongoing research, should be used in decision making regarding recommendations for manufacturing and use of candidate F-free foams.

Potential of ornamental monocot plants for rhizofiltration of cadmium and zinc in hydroponic systems

Cadmium (Cd) and zinc (Zn) accumulation and uptake ability have been investigated in three ornamental monocot plants (Heliconia psittacorum x H. spathocircinata, Echinodorus cordifolius, and Pontederia cordata) grown in hydroponic systems. All study plants in the highest heavy metal treatments were found to be excluders for Cd and Zn with translocation factor values < 1 and bioconcentration factor (BCF) values > 100. The highest Cd and Zn accumulations were found in roots of E. cordifolius (4766.6 mg Zn kg^-1 and 6141.6 mg Cd kg^-1), followed by H. psittacorum x H. spathocircinata (4313.5 mg Zn kg^-1) and P. cordata (3673.3 mg Cd kg^-1), respectively, whereas shoots had lower performances. However, P. cordata had the lowest dry biomass production compared to the other two plant species in this study. As a result of dilution effects, heavy metal accumulation for all study plants was lower in the combined heavy metal treatments than in solely Cd and Zn only treatments. At the end of experiments, the highest uptakes of Cd and Zn were found in H. psittacorum x H. spathocircinata (62.1% Zn²⁺ from 10 mg Zn L^-1 solution) and E. cordifolius (27.3% Cd²⁺ from 2 mg Cd L^-1 solution). Low percentage metal uptakes were found in P. cordata; therefore, E. cordifolius and H. psittacorum x H. spathocircinata are clearly better suited for removing Cd and/or Zn from contaminated waters and hydroponic systems.

Potential of ornamental monocot plants for rhizofiltration of cadmium and zinc in hydroponic systems

Cadmium (Cd) and zinc (Zn) accumulation and uptake ability have been investigated in three ornamental monocot plants (Heliconia psittacorum x H. spathocircinata, Echinodorus cordifolius, and Pontederia cordata) grown in hydroponic systems. All study plants in the highest heavy metal treatments were found to be excluders for Cd and Zn with translocation factor values < 1 and bioconcentration factor (BCF) values > 100. The highest Cd and Zn accumulations were found in roots of E. cordifolius (4766.6 mg Zn kg^-1 and 6141.6 mg Cd kg^-1), followed by H. psittacorum x H. spathocircinata (4313.5 mg Zn kg^-1) and P. cordata (3673.3 mg Cd kg^-1), respectively, whereas shoots had lower performances. However, P. cordata had the lowest dry biomass production compared to the other two plant species in this study. As a result of dilution effects, heavy metal accumulation for all study plants was lower in the combined heavy metal treatments than in solely Cd and Zn only treatments. At the end of experiments, the highest uptakes of Cd and Zn were found in H. psittacorum x H. spathocircinata (62.1% Zn²⁺ from 10 mg Zn L^-1 solution) and E. cordifolius (27.3% Cd²⁺ from 2 mg Cd L^-1 solution). Low percentage metal uptakes were found in P. cordata; therefore, E. cordifolius and H. psittacorum x H. spathocircinata are clearly better suited for removing Cd and/or Zn from contaminated waters and hydroponic systems.

Terrestrial plants as a potential temporary sink of atmospheric microplastics during transport

Atmospheric transport is an important pathway by which terrestrial microplastics (MPs, with sizes less than 5 mm) can move long distances to remote areas. However, little is known about the environmental behaviors of atmospheric MPs during movement. To address this issue, deposits of MPs on the leaves of plants were studied in two regions, with abundance ranging from 0.07 n/cm² (pieces per area of leaves) to 0.19 n/cm². The attached substances were mainly natural materials, but 28% of the total substances were plastics. There was a similar physical-chemical composition of the attached MPs in the two regions suggesting a similar origin. Leaves, regardless of plant species, can indiscriminately retain atmospheric MPs. About 0.13 trillion pieces of MPs are estimated to be attached to leaf surfaces in the top 11 green countries. Leaves of terrestrial plants could be a temporal sink and a source of MPs pollution to remote areas. This is not fully recognized and merits further study.

Sample preparation for arsenic speciation in terrestrial plants--a review

Arsenic is an element widely present in nature. Additionally, it may be found as different species in several matrices and therefore it is one of the target elements in chemical speciation. Although the number of studies in terrestrial plants is low, compared to matrices such as fish or urine, this number is raising due to the fact that this type of matrix are closely related to the human food chain. In speciation analysis, sample preparation is a critical step and several extraction procedures present drawbacks. In this review, papers dealing with extraction procedures, analytical methods, and studies of species conservation in plants cultivated in terrestrial environment are critically discussed. Analytical procedures based on extractions using water or diluted acid solutions associated with HPLC-ICP-MS are good alternatives, owing to their versatility and sensitivity, even though less expensive strategies are shown as feasible choices.