Phytoremediation and natural attenuation of sulfentrazone: mineralogy influence of three highly weathered soils

Canavalia ensiformis enhances the phytoremediation of remineralized and sulfentrazone-contaminated tropical soils

The objective of the study was to assess the phytoremediation potential in two remineralized soils contaminated with sulfentrazone. Two soil types were evaluated: Oxisol (clayey) and Inceptisol (sandy loam), in pots, with and without the incorporation of the rock powder, at rates of 0, 4, and 8 t ha-1. Following this, sulfentrazone was applied at rates of 200, 400, 600, and 800 g a. i. ha-1, in addition to the control treatment without herbicide application, followed by the sowing of Canavalia ensiformis (jack bean). Injury level (IL) was assessed at 42 days after emergence (DAE), and biometric evaluations of the phytoremediating species were conducted at 70 and 120 DAE in the Oxisol and Inceptisol, respectively, for the following variables: height (HT), diameter (DM), trifoliate leaf number (TN), leaf area (LA), above-ground dry biomass (DB), and root dry biomass (RDB). At the end of the phytoremediation experiment, the soils were analyzed using High-Performance Liquid Chromatography (HPLC) and with Sorghum bicolor (sorghum) as a bioindicator to verify the residue of sulfentrazone. IL and DB assessments of the bioindicator species were conducted at 21 DAE. In both soils, higher herbicide rates (600 and 800 g a. i. ha-1) resulted in greater IL and reduced HT, LA, DB, and RDB of the phytoremediating species. C. ensiformis reduced the sulfentrazone residues in the soils. Although it did not directly influence phytoremediation, the rock powder improved soil fertility. In conclusion, C. ensiformis has the potential for effective phytoremediation of soils contaminated with sulfentrazone, providing safety for cultivating sensitive crops and benefiting the environment.

Investigation of the Persistence, Toxicological Effects, and Ecological Issues of S-Triazine Herbicides and Their Biodegradation Using Emerging Technologies: A Review

S-triazines are a group of herbicides that are extensively applied to control broadleaf weeds and grasses in agricultural production. They are mainly taken up through plant roots and are transformed by xylem tissues throughout the plant system. They are highly persistent and have a long half-life in the environment. Due to imprudent use, their toxic residues have enormously increased in the last few years and are frequently detected in food commodities, which causes chronic diseases in humans and mammals. However, for the safety of the environment and the diversity of living organisms, the removal of s-triazine herbicides has received widespread attention. In this review, the degradation of s-triazine herbicides and their intermediates by indigenous microbial species, genes, enzymes, plants, and nanoparticles are systematically investigated. The hydrolytic degradation of substituents on the s-triazine ring is catalyzed by enzymes from the amidohydrolase superfamily and yields cyanuric acid as an intermediate. Cyanuric acid is further metabolized into ammonia and carbon dioxide. Microbial-free cells efficiently degrade s-triazine herbicides in laboratory as well as field trials. Additionally, the combinatorial approach of nanomaterials with indigenous microbes has vast potential and considered sustainable for removing toxic residues in the agroecosystem. Due to their smaller size and unique properties, they are equally distributed in sediments, soil, water bodies, and even small crevices. Finally, this paper highlights the implementation of bioinformatics and molecular tools, which provide a myriad of new methods to monitor the biodegradation of s-triazine herbicides and help to identify the diverse number of microbial communities that actively participate in the biodegradation process.

Phytoremediation: A green and low-cost technology to remediate herbicides in the environment

Pesticide dependence is one of the main disadvantages of agriculture. Despite the advances in biological control and integrated management of plant pests and diseases in recent years, herbicides are still essential for weed control and constitute the main class of pesticides worldwide. Herbicide residues in water, soil, air, and non-target organisms are among the biggest agricultural and environmental sustainability obstacles. Therefore, we suggest an environmentally viable alternative to reduce the harmful effects of herbicide residues, a technology called phytoremediation. Remediating plants were grouped into herbaceous, arboreal, and aquatic macrophytes. Phytoremediation can reduce the loss of at least 50% of all herbicide residues to the environment. Among the herbaceous species reported as phytoremediators of herbicides, the Fabaceae family was mentioned in more than 50% of reports. This family is also among the main species of trees reported. Regarding the most reported groups of herbicides, it is observed that most of them, regardless of the group of plants, are triazines. Processes such as extraction or accumulation are the best known and reported for most herbicides. The phytoremediation may be effective against chronic or unknown herbicide toxicity. This tool can be included in proposals for management plans and specific legislation in countries, guaranteeing public policies to maintain environmental quality.

Crotalaria juncea L. enhances the bioremediation of sulfentrazone-contaminated soil and promotes changes in the soil bacterial community

Sulfentrazone (STZ) is an efficient tool for the pre- and post-emergence control of monocotyledonous and dicotyledonous weeds in fields of crops such as pineapple, coffee, sugarcane, citrus, eucalyptus, tobacco, and soybean. However, this herbicide persists in the soil, causing phytotoxicity in the subsequent crop. Therefore, it is important to use efficient strategies for the remediation of STZ-contaminated areas. The aim of this study was to evaluate the effects of Crotalaria juncea L. on the remediation of STZ-contaminated soil and on the microbial activity and bacterial community structure therein. The study was conducted in three stages: (i) cultivation of C. juncea in soil contaminated with 200, 400, and 800 g ha-1 STZ; (ii) determination of the soil microbial activity (basal respiration, microbial biomass carbon, and bacterial community structure); and (iii) cultivation of a bioindicator species and determination of the residual fraction of STZ. The soil microbial activity was impacted by the soil type and STZ dose. Soil previously cultivated with C. juncea (rhizospheric soil) displayed higher CO2 and lower qCO2 values than non-rhizospheric soil (no previous C. juncea cultivation). Increasing doses of STZ reduced the activity and lowered the diversity indices of the soil microorganisms. The bacterial community structure was segregated between the rhizospheric and non-rhizospheric soils. Regardless of soil type, the bioindicator of remediation (Pennisetum glaucum R.Br.) grew only at the STZ dose of 200 g ha-1, and the plant intoxication level was also lower in rhizospheric soil treated with this herbicide dose. All P. glaucum plants died in the soils treated with 400 and 800 g ha-1 STZ. Previous cultivation of C. juncea in soils contaminated with 200, 400, and 800 g ha-1 STZ reduced the residual fraction of the herbicide by 4.8%, 12.5%, and 17.4%, respectively, compared with that in the non-rhizospheric soils. In conclusion, previous cultivation with C. juncea promoted increases in the soil bacterial activity and diversity indices, mitigated the deleterious effects of STZ on the bioindicator crop, and reduced the residual fraction of the herbicide in the soil.

Bacterial ACC deaminase: Insights into enzymology, biochemistry, genetics, and potential role in amelioration of environmental stress in crop plants

Growth and productivity of crop plants worldwide are often adversely affected by anthropogenic and natural stresses. Both biotic and abiotic stresses may impact future food security and sustainability; global climate change will only exacerbate the threat. Nearly all stresses induce ethylene production in plants, which is detrimental to their growth and survival when present at higher concentrations. Consequently, management of ethylene production in plants is becoming an attractive option for countering the stress hormone and its effect on crop yield and productivity. In plants, ACC (1-aminocyclopropane-1-carboxylate) serves as a precursor for ethylene production. Soil microorganisms and root-associated plant growth promoting rhizobacteria (PGPR) that possess ACC deaminase activity regulate growth and development of plants under harsh environmental conditions by limiting ethylene levels in plants; this enzyme is, therefore, often designated as a "stress modulator." TheACC deaminase enzyme, encoded by the AcdS gene, is tightly controlled and regulated depending upon environmental conditions. Gene regulatory components of AcdS are made up of the LRP protein-coding regulatory gene and other regulatory components that are activated via distinct mechanisms under aerobic and anaerobic conditions. ACC deaminase-positive PGPR strains can intensively promote growth and development of crops being cultivated under abiotic stresses including salt stress, water deficit, waterlogging, temperature extremes, and presence of heavy metals, pesticides and other organic contaminants. Strategies for combating environmental stresses in plants, and improving growth by introducing the acdS gene into crop plants via bacteria, have been investigated. In the recent past, some rapid methods and cutting-edge technologies based on molecular biotechnology and omics approaches involving proteomics, transcriptomics, metagenomics, and next generation sequencing (NGS) have been proposed to reveal the variety and potential of ACC deaminase-producing PGPR that thrive under external stresses. Multiple stress-tolerant ACC deaminase-producing PGPR strains have demonstrated great promise in providing plant resistance/tolerance to various stressors and, therefore, it could be advantageous over other soil/plant microbiome that can flourish under stressed environments.

Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

Trees occurring on the margins of agricultural areas can mitigate damage from residual herbicides. Rhizospheric microbial activity associated with trees is one of the main remedial capacity indicators. The objective of this study was to evaluate the rhizospheric microbiological activity in tree species subjected to the herbicides atrazine and sulfentrazone via the rhizosphere. The experiment was designed in four blocks and a 6 × 3 factorial scheme. The first factor consisted of six tree species from Brazil and the second of atrazine, sulfentrazone, and water solutions. Four herbicide applications were performed via irrigation. The total dry mass of the plants, mycorrhizal colonization, number of spores, basal respiration of the rhizospheric soil, and survival rate of bioindicator plants after phytoremediation were determined. Trichilia hirta had higher biomass when treated with atrazine and sulfentrazone. Herbicides decreased the microbial activity in Triplaris americana and did not affect the microbiological indicators of Myrsine gardneriana, Schizolobium parahyba, and Toona ciliata. Fewer bioindicator plants survived in soil with Triplaris americana and sulfentrazone. Microbiological indicators were influenced in different ways between species by the presence of herbicides in the rhizosphere.

Phytoremediation and Bioremediation of Pesticide-Contaminated Soil

Management and destruction of obsolete pesticides and the remediation of pesticide-contaminated soil are significant global issues with importance in agriculture, environmental health and quality of life. Pesticide use and management have a history of problems because of insufficient knowledge of proper planning, storage, and use. This manuscript reviews recent literature with an emphasis on the management of obsolete pesticides and remediation of pesticide-contaminated soil. The rhizosphere of plants is a zone of active remediation. Plants also take up contaminated water and remove pesticides from soil. The beneficial effects of growing plants in pesticide-contaminated soil include pesticide transformation by both plant and microbial enzymes. This review addresses recent advances in the remediation of pesticide-contaminated soil with an emphasis on processes that are simple and can be applied widely in any country.