Four genotypes of snap bean (Phaseolus vulgaris L.) were selected to study the effects of ambient ozone concentration at a cropland area around Beijing by using 450 ppm of ethylenediurea (EDU) as a chemical protectant. During the growing season, the 8h (9:00–17:00) average ozone concentration was very high, approximately 71.3 ppb, and AOT40 was 29.0 ppm.h. All genotypes showed foliar injury, but ozone-sensitive genotypes exhibited much more injury than ozone-tolerant ones. Compared with control, EDU significantly alleviated foliar injury, increased photosynthesis rate and chlorophyll a fluorescence, Vcmax and Jmax, and seed and pod weights in ozone-sensitive genotypes but not in ozone-tolerant genotypes. EDU did not significantly affect antioxidant contents in any of the genotypes. Therefore, EDU effectively protected sensitive genotypes from ambient ozone damage, while protection on ozone-tolerant genotypes was limited. EDU can be regarded as a useful tool in risk assessment of ambient ozone on food security.

Ozone-sensitive (S156) and -tolerant (R123 and R331) genotypes of snap bean (Phaseolus vulgaris L.) were tested as a plant bioindicator system for detecting O₃ effects at current and projected future levels of tropospheric O₃ and atmospheric CO₂ under field conditions. Plants were treated with ambient air, 1.4× ambient O₃ and 550 ppm CO₂ separately and in combination using Free Air Concentration Enrichment technology. Under ambient O₃ concentrations pod yields were not significantly different among genotypes. Elevated O₃ reduced pod yield for S156 (63%) but did not significantly affect yields for R123 and R331. Elevated CO₂ at 550 ppm alone did not have a significant impact on yield for any genotype. Amelioration of the O₃ effect occurred in the O₃ + CO₂ treatment. Ratios of sensitive to tolerant genotype pod yields were identified as a useful measurement for assessing O₃ impacts with potential applications in diverse settings including agricultural fields.

Ethylenediurea (EDU) is the most common chemical used to prevent ozone (O3) injury on vegetation. Despite considerable research, its mode of action remains elusive and gene expression has not been studied. Transcripts of major antioxidant enzymes (catalase, glutathione reductase, glutathione peroxidase) were measured for the first time in a model plant (Phaseolus vulgaris cv S156) after short-term O3 exposure (0 or 90 ppb, 5 h/d, 4 days) and a single spray with EDU (0 or 300 ppm). Visible, physiological and biochemical parameters were assessed as indices of O3-induced stress. In O3-exposed EDU-protected plants, levels of transcript, enzyme activity, H2O2 accumulation, gas exchange and foliar visible injury were similar to those in control plants. These results suggest that EDU may halt the O3-induced ROS generation within 24 h from the exposure, and thus the downstream cascade mechanisms leading to increased H2O2 production, impaired gas exchange, and occurrence of leaf lesions.

Bush bean (Phaseolus vulgaris) was exposed to atmospheric deposition of As, Cd and Pb in a polluted and a reference area. The atmospheric deposition of these elements was significantly related to the concentrations in leaves, stems and pods at green harvest. Surprisingly there was also a clear relation for As and Pb in the seeds at dry harvest, even though these seeds were covered by the husks. Root uptake of accumulated atmospheric deposits was not likely in such a short term experiment, as confirmed by the fact that soil pore water analysis did not reveal significant differences in trace element concentrations in the different exposure areas. For biomonitoring purposes, the leaves of bush bean are the most suitable, but also washed or unwashed pods can be used. This means that the obtained relationships are suitable to estimate the transfer of airborne trace elements in the food chain via bush bean.

Tropospheric ozone (O₃) is the air pollutant of most concern to vegetation at present. Ozone impacts on stomata are still controversial, as both decreased stomatal conductance and slow stomatal responses to environmental stimuli (namely, stomatal sluggishness) have been shown. We postulated that the light environment affects stomatal sluggishness. To concurrently manipulate O₃ and light conditions and measure gas exchange at leaf level, we developed an innovative O₃ exposure system by modifying a commercially available gas exchange system. We exposed the first trifoliate leaf of the O₃-sensitive genotype S156 of snapbean (Phaseolus vulgaris) to a 1-h O₃ exposure (150 ppb) under 1000 μmol m⁻² s⁻¹ photosynthetic photon flux density, so that stomata were fully open and O₃ uptake was maximized. Then, leaves were subjected to different light intensities (200, 1000, or 1500 μmol m⁻² s⁻¹) until a steady state was reached. As a metric of sluggishness, we quantified the stomatal responses to a sharp water stress generated by cutting the petiole at steady state. The results showed that O₃ exposure induced stomatal sluggishness only under high light (stomata needed 53 % more time to half stomatal conductance relative to steady state) and did not when the plants were under lower light intensities. We conclude that O₃-induced stomatal sluggishness may occur only in fully irradiated leaves, and suggest it is a minor response when entire crowns and canopies are assessed and a major reason of the higher O₃ sensitivity of sun leaves than of shade leaves.

Cadmium (Cd) is a toxic and nonessential element. Because of its toxicity, Cd soil contamination is a major environmental risk to living organisms. Several studies have reported on the successful use of biochar to immobilize Cd in soil as it reduces Cd accumulation in plant parts. This research reports on the contrasting effect of biochar on enhancing Cd uptake by plants. A cassava stem biochar produced through low-temperature pyrolysis was applied to natural Cd-contaminated soil that also had a high zinc (Zn) concentration. Vigna radiata L. (a green bean) was grown in treatments receiving three biochar rates, i.e., 5, 10, and 15 %, respectively. The results showed that the 10 % biochar-amended soil had a positive effect on promoting plant growth and seed yield. Unfortunately, 15 % biochar-amended soil caused an adverse effect to plant growth. Cadmium uptake by plants increased with increasing biochar application rate. Zinc uptake by plants tended to decrease with biochar application. Cadmium and Zn bioavailability in soil was significantly reduced with an increasing biochar application rate. The results also showed that the biochar-amended soil could be an alternative and cost-effective method to promote plant growth and decrease Cd mobility in soil. The ratio of Cd concentration in plant root to soil was higher than 1, while the translocation factor from root to shoot was less than 1. These results indicate that the cultivation of V. radiata L. coupled with biochar application is an appropriate method to enhance Cd phytostabilization efficiency of V. radiata L. in Cd-polluted sites.

Petroleum hydrocarbons are applied in various energy activities. If accidents happen, they may result in environmental contamination, especially in soil. Petroleum hydrocarbons have low evaporation rates and are adsorbed on the soil surface, making it necessary to treat contaminated soil before the pollutants spread to other areas. Soil washing with surfactant solution is a method used to treat petroleum hydrocarbon contamination. The process relies on surfactant properties which reduce surface tension and desorb diesel from soil particles prior to flushing out with water. The relationship between efficiency of diesel extraction from contaminated soil and factors of both single surfactants (Span20, Tween20, Tween80, Dehydol LS9) and mixed surfactants (Span20+Tween20, Span20+Tween80, Span20+Dehydol LS9) were investigated including hydrophile-lipophile balance (HLB) and interfacial tension (IFT) to select a suitable surfactant. Diesel was analyzed by GC-FID. Findings revealed that extraction efficiency significantly increased when the HLB of the surfactant increased in every solution pair (p = 0.05). Span20+Dehydol LS9 solution with HLB 12 showed the lowest IFT (17.767 ± 0.013 mN/m) and the highest diesel extraction efficiency (66.2%). The water washing process, repeated twice after washing with 1% (w/v) Span20+Dedydol LS9, resulted in less toxicity on germination and growth of tomato, rice, and green bean compared with diesel washing solution and fresh washing solution. Diesel-contaminated soil washing with mixed surfactant is an interesting alternative as an environmentally friendly soil treatment. Graphical Abstract

Agricultural practices are usually supported by several chemical substances, such as herbicides. Linuron and chlorbromuron are phenylurea herbicides largely used to protect crops from weeds, blocking photosynthesis by inhibition of the photosystem II complex. The former, also commercially known as lorox or afalon, is selectively used to protect bean and French bean plants, fennels, and celeriacs; the second, commercially known as maloran, is selectively used for carrots, peas, potatoes, soy sprouts, and sunflowers. Considering the widespread use of herbicides and, more generally, pesticides, it is important to clarify their involvement on human health, one of them concerning the possible direct or indirect effect on the genome of exposed populations. Here, we show that these herbicides are endowed by mutagenic properties, as demonstrated by an increased number of chromosomal aberrations (CAs) in two exposed Chinese hamster cell lines derived from ovary and epithelial liver, respectively. This was also confirmed by sister chromatid exchange (SCE) and micronucleus (MN) assays. Our present and previously obtained data clearly indicate that phenylurea herbicides must be used with great caution, especially for agricultural workers who use large amounts of herbicides during their work, and particular attention should be given to residues of these herbicides and their involvement in environmental pollution.

Dredged river sediments and biosolids used as amendments for agricultural purposes can provide a suitable plant growth medium, a topsoil substitute. Nevertheless, trace metal bioaccumulation and risk of plant toxicity remains a concern. We conducted a greenhouse experiment to evaluate the plant growth and trace metal bioaccumulation on sediments and biosolid mixtures. These included dredged sediment from the Peoria Lakes portion of the Illinois River and class A biosolids from the Metropolitan Water Reclamation District of Greater Chicago. Six different mixtures were produced in addition to a standard greenhouse mix serving as a control. Barley (Hordeum vulgare) and snap bean (Phaseolus vulgaris) were grown on the mixtures in the greenhouse. Plants grew in all treatments, except for snap beans that were stunted likely by high salt content in unleached biosolid mixtures. The highest overall biomass production for barley was obtained in the treatment composed of 50% sediment and 50% biosolids. For snap bean, the highest biomass productions were obtained in treatments composed of ≤50% biosolids in the mixture. Trace metals in plant tissue were within ranges considered normal, except for Mo in snap bean, which was at a level considered excessive. However, addition of biosolids to sediments decreased Mo plant uptake. Based on our results, sediments mixed with biosolids make a fertile topsoil and have no inherent chemical or physical properties that would preclude its use as a plant growth medium. Adding sediments to unleached fresh biosolids improved plant growth and diminished trace metal uptake. The suggested optimal ratio of sediments to biosolids would be 80:20 to 70:30 by volume in most situations.

The air pollutant ozone (O₃) is a phytotoxic oxidative stressor, leading to visible foliar injury and plant growth decline. Plant growth-promoting bacteria (PGPB) are emerging as an eco-friendly tool for improving plant growth under stress. In order to test PGPB as a tool for alleviating O₃ stress in plants, an O₃ sensitive genotype (Phaseolus vulgaris L. cv S156) was inoculated with native (rhizobacterial; B1 and B2) and non-native PGPB (Bacillus megaterium and B. amylolequefaciens) and exposed to realistic O₃ exposure (ambient, AA with AOT40 = 0.53 ppm per hour, and twice ambient ozone concentration, 2XAA, AOT40 = 1.84 ppm per hour). The promoting effect was assessed by quantifying visible foliar O₃ injury (PII), chlorophyll a fluorescence (Fv/Fm), contents of hydrogen peroxide (H₂O₂), malondialdehyde (MDA) and nitric oxide (NO), ethylene emission, 1-aminocyclo-propane-1-carboxylate (ACC) deaminase enzyme activity, above- and below-ground biomass. BM, BA and B1 showed higher ACC deaminase enzyme activity and Fv/Fm, while ethylene emission, PII, H₂O₂, MDA and NO contents were lower in the BM, BA and B1 plants than in the B2 and non-inoculated plants under 2XAA. Only BA increased above- and below-ground biomass under AA and 2XAA. We conclude that PGPB are able to ameliorate O₃ stress through induction of systemic resistance; the level of bacterial ACC deaminase is one of the good markers for identifying effective strains and may be tested as an agricultural practice for improving crop yield under O₃ pollution.