Reviews of environmental contamination and toxicology最新文献

Glyphosate is the most used herbicide globally. It is a unique non-selective herbicide with a mode of action that is ideal for vegetation management in both agricultural and non-agricultural settings. Its use was more than doubled by the introduction of transgenic, glyphosate-resistant (GR) crops. All of its phytotoxic effects are the result of inhibition of only 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), but inhibition of this single enzyme of the shikimate pathway results in multiple phytotoxicity effects, both upstream and downstream from EPSPS, including loss of plant defenses against pathogens. Degradation of glyphosate in plants and microbes is predominantly by a glyphosate oxidoreductase to produce aminomethylphosphonic acid and glyoxylate and to a lesser extent by a C-P lyase to produce sarcosine and phosphate. Its effects on non-target plant species are generally less than that of many other herbicides, as it is not volatile and is generally sprayed in larger droplet sizes with a relatively low propensity to drift and is inactivated by tight binding to most soils. Some microbes, including fungal plant pathogens, have glyphosate-sensitive EPSPS. Thus, glyphosate can benefit GR crops by its activity on some plant pathogens. On the other hand, glyphosate can adversely affect some microbes that are beneficial to agriculture, such as Bradyrhizobium species, although GR crop yield data indicate that such an effect has been minor. Effects of glyphosate on microbes of agricultural soils are generally minor and transient, with other agricultural practices having much stronger effects.

Glyphosate-resistant (GR) crops, commercially referred to as glyphosate-tolerant (GT), started the revolution in crop biotechnology in 1996. Growers rapidly accepted GR crops whenever they became available and made them the most rapidly adopted technology in agriculture history. Adoption usually meant sole reliance on glyphosate [N-(phosphonomethyl)glycine, CAS No. 1071-83-6] for weed control. Not surprisingly, weeds eventually evolved resistance and are forcing growers to change their weed management practices. Today, the widespread dissemination of GR weeds that are also resistant to other herbicide modes-of-action (MoA) has greatly reduced the value of the GR crop weed management systems. However, growers continue to use the technology widely in six major crops throughout North and South America. Integrated chemistry and seed providers seek to sustain glyphosate efficacy by promoting glyphosate combinations with other herbicides and stacking the traits necessary to enable the use of partner herbicides. These include glufosinate {4-[hydroxy(methyl)phosphinoyl]-DL-homoalanine, CAS No. 51276-47-2}, dicamba (3,6-dichloro-2-methoxybenzoic acid, CAS No. 1918-00-9), 2,4-D [2-(2,4-dichlorophenoxy)acetic acid, CAS No. 94-75-7], 4-hydroxyphenyl pyruvate dioxygenase inhibitors, acetyl coenzyme A carboxylase (ACCase) inhibitors, and other herbicides. Unfortunately, herbicide companies have not commercialized a new MoA for over 30 years and have nearly exhausted the useful herbicide trait possibilities. Today, glyphosate-based crop systems are still mainstays of weed management, but they cannot keep up with the capacity of weeds to evolve resistance. Growers desperately need new technologies, but no technology with the impact of glyphosate and GR crops is on the horizon. Although the expansion of GR crop traits is possible into new geographic areas and crops such as wheat and sugarcane and could have high value, the Roundup Ready® revolution is over. Its future is at a nexus and dependent on a variety of issues.

Freshwater and marine water bodies receive chemical contaminants from industrial, agricultural, urban, and domestic wastes. Eco-genotoxicity assays are useful tools to assess the cumulative genotoxicity of these pollutants. Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution.In this review, we present a complete overview of the studies performed so far using the micronucleus test in peripheral erythrocytes of fish exposed to polluted water. We have listed all the species of fish used and the geographical distribution of the investigations. We have analyzed and discussed all technical aspects of using this test in fish, as well as the advantages and disadvantages of the different experimental protocols. We have reported the results of all studies. This assay has become, for years, one of the simplest, fastest, and most cost-effective for assessing genotoxic risk in aquatic environments. However, there are still several factors influencing the variability of the results. Therefore, we have given indications and suggestions to achieve a standardization of experimental procedures and ensure uniformity of future investigations.

Pesticides can enter aquatic environments via direct application, via overspray or drift during application, or by runoff or leaching from fields during rain events, where they can have unintended effects on non-target aquatic biota. As such, Fisheries and Oceans Canada identified a need to prioritize current-use pesticides based on potential risks towards fish, their prey species, and habitats in Canada. A literature review was conducted to: (1) Identify current-use pesticides of concern for Canadian marine and freshwater environments based on use and environmental presence in Canada, (2) Outline current knowledge on the biological effects of the pesticides of concern, and (3) Identify general data gaps specific to biological effects of pesticides on aquatic species. Prioritization was based upon recent sales data, measured concentrations in Canadian aquatic environments between 2000 and 2020, and inherent toxicity as represented by aquatic guideline values. Prioritization identified 55 pesticides for further research nationally. Based on rank, a sub-group of seven were chosen as the top-priority pesticides, including three herbicides (atrazine, diquat, and S-metolachlor), three insecticides (chlorpyrifos, clothianidin, and permethrin), and one fungicide (chlorothalonil). A number of knowledge gaps became apparent through this process, including gaps in our understanding of sub-lethal toxicity, environmental fate, species sensitivity distributions, and/or surface water concentrations for each of the active ingredients reviewed. More generally, we identified a need for more baseline fish and fish habitat data, ongoing environmental monitoring, development of marine and sediment-toxicity benchmarks, improved study design including sufficiently low method detection limits, and collaboration around accessible data reporting and management.

Dissolved organic matter (DOM), a type of mixture containing complex structures and interactions, has important effects on environmental processes such as the complexation and interface reactions of soil heavy metals. Furthermore, microbial dissimilatory iron reduction (DIR), a key process of soil biogeochemical cycle, is closely related to the migration and transformation of heavy metals and causes the release of DOM by carbon-ferrihydrite associations. This chapter considers the structural properties and characterization techniques of DOM and its interaction with microbial dissimilated iron. The effect of DOM on microbial DIR is specifically manifested as driving force properties, coprecipitation, complexation, and electronic shuttle properties. The study, in addition, further explored the influence of pH, microorganisms, salinity, and light conditions, mechanism of DOM and microbial DIR on the toxicity and bioavailability of different heavy metals. The action mechanism of these factors on heavy metals can be summarized as adsorption coprecipitation, methylation, and redox. Based on the findings of the review, future research is expected to focus on: (1) The combination of DOM functional group structure analysis with high-resolution mass spectrometry technology and electrochemical methods to determine the electron supply in the mechanism of DOM action on DIR; (2) Impact of DOM on differences in structure and functions of plant rhizosphere in heavy metal contaminated soil; and (3) Bioavailability of DOM-dissociative iron-reducing bacteria-heavy metal ternary binding on rhizosphere heavy metals under dynamic changes of water level from the perspective of the differences in DOM properties, such as polarity, molecular weight, and functional group.

Widespread adoption of glyphosate-resistant crops and concomitant reliance on glyphosate for weed control set an unprecedented stage for the evolution of herbicide-resistant weeds. There are now 48 weed species that have evolved glyphosate resistance. Diverse glyphosate-resistance mechanisms have evolved, including single, double, and triple amino acid substitutions in the target-site gene, duplication of the gene encoding the target site, and others that are rare or nonexistent for evolved resistance to other herbicides. This review summarizes these resistance mechanisms, discusses what is known about their evolution, and concludes with some of the impacts glyphosate-resistant weeds have had on weed management.

The concept of Ecotoxicological Species Sensitivity Distributions, as used in EU and US, to derive environmental standards for contaminants, starts from the assumption that by protecting the majority of species (95% confidence interval) all species will be protected. Nevertheless, 5% of the species outside the confidence interval might become harmed; half of it being the most sensitive for the particular compound tested. With respect to protection of rare endemic species it is not clear, however, if contamination is a driving factor for endemicity. The aim of this paper is to explore whether endemic and rare species deserve extra protection from adverse environmental conditions. To this end, a brief overview of the various forms of endemism, their relation to environmental stress factors and the distribution of endemic species is discussed. Further, the sensitivities of these species towards environmental stress factors are analysed, in order to conclude if and how endemic species could be better protected against environmental stress factors. This was achieved by specifically focusing on the potential impacts of metalliferous soils, mining, the treatment of mined soil and the storage of treated mine waste. It is concluded that at present there are some signals about specific sensitivities, but the database is much too small for a definite conclusion about adverse environmental factors as a threat to endemic species. The data gap has to be filled in with experimental tests with endemic species. This is hampered by the protection status of these endemic, rare species. Recommendations and derived activities are proposed to address this.

Increasing production and utilization of cerium oxide nanoparticles (CNPs) in recent years have raised wide concerns about their toxicity. Numerous studies have been conducted to reveal the toxicity of CNPs, but the results are sometimes contradictory. In this review, the most important factors in mediating CNPs toxicity are discussed, including (1) the roles of physicochemical properties (size, morphology, agglomeration condition, surface charge, coating and surface valence state) on CNPs toxicity; (2) the phase transfer and transformation process of CNPs in various aqueous, terrestrial, and airborne environments; and (3) reductive dissolution of CNPs core and their chemical reactions with phosphate, sulfate/S^2-, and ferrous ions. The physicochemical properties play key roles in the interactions of CNPs with organisms and consequently their environmental transformations, reactivity and toxicity assessment. Also, the speciation transformations of CNPs caused by reactions with (in)organic ligands in both environmental and biological systems would further alter their fate, transport, and toxicity potential. Thus, the toxicity mechanisms are proposed based on the physical damage of direct adsorption of CNPs onto the cell membrane and chemical inhibition (including oxidative stress and interaction of CNPs with biomacromolecules). Finally, the current knowledge gaps and further research needs in identifying the toxicological risk factors of CNPs under realistic environmental conditions are highlighted, which might improve predictions about their potential environmental influences. This review aims to provide new insights into cost-effectiveness of control options and management practices to prevent environmental risks from CNPs exposure.

Heavy metal (HM) contamination is a serious global environmental crisis. Over the past decade, industrial effluents, modern agricultural practices, and other anthropogenic activities have significantly depleted the soil environment. In plants, metal toxicity leads to compromised growth, development, productivity, and yield. Also, HMs negatively affect human health due to food chain contamination. Thus, it is imperative to reduce metal accumulation and toxicity. In nature, certain plant species exhibit an inherent capacity of amassing large amounts of HMs with remarkable tolerance. These plants with unique characteristics can be employed for the remediation of contaminated soil and water. Among different plant species, Sorghum bicolor has the potential of accumulating huge amounts of HMs, thus could be regarded as a hyperaccumulator. This means that it is a metal tolerant, high biomass producing energy crop, and thus can be utilized for phytoremediation. However, high concentrations of HMs hamper plant height, root hair density, shoot biomass, number of leaves, chlorophyll, carotenoid, and carbohydrate content. Thus, understanding the response of Sorghum towards different HMs holds considerable importance. Considering this, we have uncovered the basic information about the metal uptake, translocation, and accumulation in Sorghum. Plants respond to different HMs via sensing, signaling, and modulations in physico-chemical processes. Therefore, in this review, a glimpse of HM toxicity and the response of Sorghum at the morphological, physiological, biochemical, and molecular levels has been provided. The review highlights the future research needs and emphasizes the extensive molecular dissection of Sorghum to explore its genetic adaptability towards different abiotic stresses that can be exploited to develop resilient crop varieties.