Hydrogen gas (H₂) has been shown as an important factor in plant tolerance to abiotic stresses, but the underlying mechanisms remain unclear. In the present study, the effects of H₂ and its interaction with nitric oxide (NO) on alleviating cadmium (Cd) stress in Brassica campestris seedlings were investigated. NO donor (SNP) or hydrogen-rich water (HRW) treatment showed a significant improvement in growth of Cd-stressed seedlings. Cd treatment upregulated both endogenous NO and H₂ (36% and 66%, respectively), and the increase of H₂ was prior to NO increase. When treated with NO scavenger (PTIO) or NO biosynthesis enzyme inhibitors (L-NAME and Gln), HRW-induced alleviation under Cd stress was prevented. Under Cd stress, HRW pretreatment significantly enhanced the NO accumulation, and together up-regulated the activity of NR (nitrate reductase) and expression of NR. HRW induced lower reactive oxygen species (ROS), higher AsA content, enhanced activity of POD (peroxidase) and SOD (superoxide dismutase) in seedling roots were inhibited by PTIO, L-NAME and Gln. Through proteomic analysis, the level of 29 proteins were changed in response to H₂ and NO-induced amelioration of Cd stress. Nearly half of them were involved in oxidation-reduction processes (about 20%) or antioxidant enzymes (approximately 20%). These results strongly indicate that in Cd-stressed seedlings, pretreatment with HRW induces the accumulation of H₂ (biosynthesized or permeated), which further stimulates the biosynthesis of NO through the NR pathway. Finally, H₂ and NO together enhance the antioxidant capabilities of seedlings in response to Cd toxicity.

Reducing the transfer of contaminants from soils to plants is a promising approach to produce safe agricultural products grown on contaminated soils. In this study, 0-400 mg/kg cetyltrimethylammonium bromide (CTMAB) and dodecylpyridinium bromide (DDPB) were separately utilized to enhance the sorption of PAHs onto soils, thereby reducing the transfer of PAHs from soil to soil solution and subsequently to plants. Concentrations of phenanthrene and pyrene in vegetables grown in contaminated soils treated with the cationic surfactants were lower than those grown in the surfactant-free control. The maximum reductions of phenanthrene and pyrene were 66% and 51% for chrysanthemum (Chrysanthemum coronarium L.), 62% and 71% for cabbage (Brassica campestris L.), and 34% and 53% for lettuce (Lactuca sativa L.), respectively. Considering the impacts of cationic surfactants on plant growth and soil microbial activity, CTMAB was more appropriate to employ, and the most effective dose was 100-200 mg/kg. Cationic surfactants could enhance the retention of PAHs in soil, and reduce PAH transfer to and accumulation in vegetables.

Tetracycline (TC) can enter the human body via the soil-vegetable-human food chain; therefore, it is necessary to understand the toxicity of TC to humans through vegetables grown on contaminated soils. The present study combined an enzyme-linked immunosorbent assay method and an HL-7702 cell model and assessed the bioavailability and toxicity of TC from pak choi (Brassica campestris L. ssp. chinensis) grown on TC-contaminated soils. The results showed that the degradation rate of TC in black soil was significantly higher than that in purplish clay, while the results for TC uptake in pak choi were opposite. The bioaccessibility of TC was found to be higher in pak choi grown on purplish clay (5.67–7.59%) than in that grown on black soil (5.22–6.77%). It is suggested that soil properties contribute to the uptake of TC by pak choi. More fertile soil contained lower TC concentrations and thus mediated lower TC toxicity to humans. It may seem comforting that TC concentrations in the edible parts of pak choi are often found to be below safe limits. However, the TC diagnosis method showed that even moderate increases in TC concentrations in pak choi may induce oxidative stress, liver injury, mitochondrial cristae and rough endoplasmic reticulum swelling, and early apoptosis in liver cells HL-7702. The pak choi grown in purplish clay showed higher TC cytotoxicity than that grown in black soil. The TC cytotoxicity of raw pak choi was found to be higher than that of cooked pak choi. These results provide direct evidence of effective ways to prevent TC toxicity in humans.

Understanding the chemical response and characteristics of bacterial communities in soil is critical to evaluate the effects of selenium (Se) supplement on plant growth and chromium (Cr)/Se uptake in Cr contaminated soil. The rhizosphere soil characteristics of pak choi (Brassica campestris L. ssp. Chinensis Makino) were investigated in soil contaminated with different levels and forms of Cr when supplemented with Se. Although inhibition of plant growth caused by Cr stress was not completely alleviated by Se, Cr content in plant tissues decreased in Cr(VI)120Se5 treatment (Cr(VI): 120 mg kg−1 soil; Se: 5 mg kg−1 soil) and its bioavailability in soil decreased in Cr(III)200Se5 (Cr(III): 200 mg kg−1 soil; Se: 5 mg kg−1 soil) treatment. Moreover, antagonism of Cr and Se on soil enzyme activities and bacterial communities were revealed. Notably, results of Cr(VI) reduction and Se metabolism functional profiles confirmed that bacterial communities play a critical role in regulating Cr/Se bioavailability. Additionally, the increases of Se bioavailability in Cr contaminated soil were ascribed to oxidation of Cr(VI) and reduction of Se reductases proportions, as well as the enhancing of pH in soil. These findings reveal that Se has the potential capacity to sustain the stability of microdomain in Cr contaminated soil.

In order to assess as to whether treated textile effluent could be safely used to irrigate some winter vegetables, growth room experiments were conducted. Varying levels of treated and untreated textile effluents were applied to germinating seeds of some winter vegetables and their effect was evaluated on germination and early growth stage using seed germination, growth, and biochemical attributes. From the results, it was obvious that textile effluent reduced seed germination and early growth of all vegetables. However, this effect was more pronounced at the highest concentration of textile effluent. Furthermore, treated textile effluent did not show any inhibitory effect on seed germination of all vegetables. Photosynthetic pigments such as chlorophyll a and b, and protein contents were higher in the leaves of all vegetable plants irrigated with treated textile effluent than those of supplied with untreated textile effluents. It has been observed that heavy metals were lower in concentration in treated textile effluent as compared with untreated textile effluent. However, germination and growth responses of all three vegetables were different to treated or untreated textile effluents. Furthermore, the Raphanus sativus ranked as tolerant followed by Brassica campastris and Brassica napus based on germination and growth responses. In conclusion, in view of shortage of water, textile effluent could safely be used for irrigation to vegetables after proper processing.

Researchers globally identify pesticides as one of the main reasons for pollinator decline. In the European Union (EU), extensive legislation is implemented to protect pollinators from harmful pesticide exposure. The aim of our study was to discover whether the pesticide residue levels in honeybee matrices, such as nectar and pollen, exceeded the chronic or acute toxicity levels when beehives were located next to fields treated with specific insecticides. The insecticides were used according to the EU legislation and its national implementation. The experiments were conducted in turnip rape, oilseed rape, and caraway fields in southern Finland during the years 2019 and 2020. The pesticides used in the experiments contained the active substances lambda-cyhalothrin (2019), esfenvalerate (2020), and tau-fluvalinate (2020). However, the honeybee-collected pollen and nectar were analyzed for residues of more than 100 active substances. The results showed that the pesticide residue levels clearly remained under the oral acute toxicity for honeybees, although we found high levels of thiacloprid residues in the pollen collected in 2019. The pesticide residues in nectar were below LOQ values, which was most likely due to the rainy weather conditions together with the chosen sampling method. No statistically significant differences were observed between the insecticide-treated and untreated fields. In light of our research, the EU legislation protected honeybees from oral acute toxicity during the years 2019 and 2020. However, potential sublethal effects of thiacloprid and other pesticide compounds found in the collected pollen cannot be ruled out. In the future, constant monitoring of pesticide exposure of honeybees and wild pollinators should be established to ensure that pesticide legislation, and its implementation across the EU successfully protects pollinators and their services in agricultural environments.

Natural resources, especially agrarian soils, have been much contaminated with various pollutants including heavy metals since industrial revolution, so it is pertinent to utilize green technology, the so-called phytoremediation technology for reclamation of heavy metal-contaminated soils. A pot experiment was conducted to screen four different species (Brassica juncea, Brassica napus, Brassica rapa, Brassica campestris) of Brassicaceae family for the remediation of HMs contaminated soil of Lakki Marwat city, Pakistan, irrigated with municipal wastewater. Plants were analyzed for various morpho-physiological, biochemical, and phytoextraction factors like bioaccumulation (BAF) and translocation factor (TF). Results showed maximum morpho-physiological responses including seed germination, chlorophyll content, root fresh and dry weights, and shoot fresh and dry weights in B. juncea followed by B. napus, B. campestris, and B. rapa. Plant biochemical analyses of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) also exhibited maximum activity in B. juncea followed by B. napus, B. campestris, and B. rapa, respectively, in both control and contaminated soils. Conversely, plant oxidative stress markers including malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) showed maximum contents in B. rapa followed by B. campestris, B. napus, and B. juncea in both soils. Plant bioconcentration factors i.e. BAF and TF measured for all species in both soils confirmed that B. juncea accumulated maximum heavy metals. Similarly, enhanced phytoextraction capacity was noticed for all Brassica species in decreasing order i.e. B. napus > B. campestris > B. rapa. Hence, all the results confirmed that B. juncea excelled and can be recommended for phytoremediation purpose in soils of study area.

Cadmium (Cd) metal extraction through efficient plant roots has attracted much attention as this methodology is environment-friendly and cost-effective. Brassica species are well known for their tolerance towards high Cd concentration in contaminated soils. The tolerance ability may vary among species; hence the assessment of this variability is mandatory for selecting Brassica species. For this purpose, a greenhouse pot experiment was carried out using three Brassica species (Brassica juncea L., Brassica campestris L., and Brassica napus L.). To evaluate the effect of chelating agent ethylenediamine tetraacetic acid (EDTA) on Cd uptake, EDTA (0, 1, and 2 g kg⁻¹ soil) was supplemented along with Cd (0, 5, 10, 20, 40, and 80 mg kg⁻¹ soil). Among different species, B. juncea possessed the highest root dry biomass and lowest root Cd concentration in untreated soil. Overall root dry biomass of all tested Brassica species reduced on increasing Cd and EDTA levels. The trend was appeared to be related to an increase in root Cd concentration on the supplementation of EDTA that formed a complex with the target metal contaminate and resulted in vacuolar sequestration. Roots of B. juncea showed maximum Cd accumulation and highest values at Cd and EDTA levels up to 20 mg kg⁻¹ and 1 g kg⁻¹ soil due to the combined effect of root biomass and Cd concentration in roots. Thus, present findings inferred that Cd and EDTA supplementation might prove as a feasible strategy to improve remediation of Cd-polluted soil using B. juncea as an efficient Cd accumulator.

The instant endeavor was undertaken for determination of lead (Pb) in water, soil, forage, and cow’s blood domesticated in contaminated area of heavy automobiles’ exhaust in Sahiwal town of District Sargodha, Pakistan. Water samples showed that the concentration of Pb ranged from 1.14 to 0.44 mg kg⁻¹ at all sites. It was maximum at site 5 and minimum at site 2. Soil samples showed the concentration of Pb at all sites ranged from 1.58 to 0.279 mg kg⁻¹. It was maximum in soil where Avena sativa was grown at site 5 and was found minimum in soil where Zea mays was grown at site 2. While among samples of forage, the concentration of Pb ranges from 0.048 to 2.002 mg kg⁻¹. The highest Pb amount was found in Brassica campestris at site 1 and the minimum was recorded in Trifolium alexandrinum at site 2. Finally, the blood samples of cow depicted that concentration of Pb ranged from 4.468 to 0.217 mg kg⁻¹. It was the maximum at site 1 and the minimum at site 3. It is recommended that such study should be conducted in other districts for public awareness.

Rhizosphere organic chemicals response and its role on Cr/Se adsorption are of great importance to understand Cr/Se bioavailability in Cr-contaminated soil with the application of Se. In the current work, the processes were carried out using rhizobox experiment (Brassica campestris L. ssp. chinensis Makino). The results showed that in soil contaminated by 200 mg kg⁻¹ Cr(III), Se(IV) complexed with Cr(III) and carboxylic acid (cis-9,10-Epoxystearic acid, hexadecanedioic acid) reduced Cr(VI) to Cr(III), thus increasing of Cr adsorption, furtherly decreasing Cr bioavailability. While in soil contaminated by 120 mg kg⁻¹ Cr(VI), Se(VI) competed for adsorption sites with Cr(VI) and salicylic acid activated insoluble Cr(III), thus decreasing Cr adsorption, finally increasing Cr bioavailability. Moreover, with Cr contamination, Se bioavailability in soil was enhanced by the secretion of carboxylic acid, which can reduce Se to lower valent state and compete the adsorption sites and complex with Se oxyanion. These results yielded a better understanding of rhizosphere dynamics regulating by Se application in Cr-contaminated soil. Moreover, the current study supplemented the theoretical basis for beneficial elements application as an environment-friendly resource to facilitate cleaner production in heavy metal contaminated soil.