Ecotoxicological characterization of a tropical soil after diazinon spraying

Toxicity of representative organophosphate, organochlorine, phenylurea, dinitroaniline, carbamate, and viologen pesticides to the growth and survival of H. vulgaris, L. minor, and C. elegans

Pesticides are commonly found in the environment and pose a risk to target and non-target species; therefore, employing a set of bioassays to rapidly assess the toxicity of these chemicals to diverse species is crucial. The toxicity of nine individual pesticides from organophosphate, organochlorine, phenylurea, dinitroaniline, carbamate, and viologen chemical classes and a mixture of all the compounds were tested in three bioassays (Hydra vulgaris, Lemna minor, and Caenorhabditis elegans) that represent plant, aquatic, and soil-dwelling species, respectively. Multiple endpoints related to growth and survival were measured for each model, and EC10 and EC50 values were derived for each endpoint to identify sensitivity patterns according to chemical classes and target organisms. L. minor had the lowest EC10 and EC50 values for seven and five of the individual pesticides, respectively. L. minor was also one to two orders of magnitude more sensitive to the mixture compared to H. vulgaris and C. elegans, where EC50 values were calculated to be 0.00042, 0.0014, and 0.038 mM, respectively. H. vulgaris was the most sensitive species to the remaining individual pesticides, and C. elegans consistently ranked the least sensitive to all tested compounds. When comparing the EC50 values across all pesticides, the endpoints of L. minor were correlated with each other while the endpoints measured in H. vulgaris and C. elegans were clustered together. While there was no apparent relationship between the chemical class of pesticide and toxicity, the compounds were more closely clustered based on target organisms (herbicide vs insecticide). The results of this study demonstrate that the combination of these plant, soil, and aquatic specie can serve as representative indicators of pesticide pollution in environmental samples.

Widespread use of toxic agrochemicals and pesticides for agricultural products storage in Africa and developing countries: Possible panacea for ecotoxicology and health implications

Chemicals used for storage majorly possess insecticidal activities - deterring destructive insect pests and microorganisms from stored agricultural produce. Despite the controversy about their safety, local farmers and agro-wholesalers still predominantly use these chemicals in developing countries, especially Africa, to ensure an all-year supply of agriproducts. These chemicals could have short- or long-term effects. Despite the state-of-the-art knowledge, factors such as poor education and awareness, limited agricultural subventions, quests for cheap chemicals, over-dosage, and many more are the possible reasons for these toxic chemicals' setback and persistent use in developing countries. This paper provides an up-to-date review of the environmental and ecological effects, as well as the health impacts arising from the indiscriminate use of toxic chemicals in agriproducts. Existing data link pesticides to endocrine disruption, genetic mutations, neurological dysfunction, and other metabolic disorders, apart from the myriad of acute effects. Finally, this study recommended several naturally sourced preservatives as viable alternatives to chemical counterparts and emphasized the invaluable role of education and awareness programs in mitigating the use in developing nations for a sustainable society.

Temporal Dynamics of Soil Invertebrate Communities in a Vineyard Under Treatment with Pesticides

Phytosanitary treatments with pesticides are widely used to control pests and diseases in vineyards. An important part of the dispersed pesticide reaches the soil, affecting the fauna, producing quantitative and qualitative changes in the edaphic population’s structure and physiological activities. This study aims to evaluate the temporal dynamics of the soil macro and mesofauna through different pesticide treatment periods, where fungicides are the dominant pest control agent. A field experiment was carried out in Boumerdes, a specific viticultural region in Algeria. Soil samples were taken during three periods, before, during, and after treatment with pesticides, using the quadrat method at three soil depths. During these three periods, the soil macro and mesofauna were observed and compared. The results showed significant differences in the composition of invertebrate communities that tended to disappear during pesticide application. The structure and diversity of 11 invertebrate classes, including Collembola, changed along the treatment gradient. The effects of sampling periods on occurrence, abundance, and taxon richness were consistently negative. These indices were significantly lower after pesticide application. Therefore, we can suppose that climatic factors and pesticide treatements are the main factors affecting the activity and density of all classes of invertebrates, but these effects vary between the functional groups of soil biota.

Are there any risks of the disposal of pesticide effluents in soils? Biobed system meets ecotoxicology ensuring safety to soil fauna

The biobed is a purification system, which reduces soil pollution for receiving pesticide residues from handling and washing machinery in agricultural areas. The aims of this study were (1) to assess ecotoxicity effects over time to soil fauna, posed by Lorsban^® 480 BR (Chlorpyrifos) and Dithane^® NT (Mancozeb) residues when disposed of in a biobed system compared with two subtropical soils, and (2) to assess ecotoxicity effects over time to soil fauna simulating an accidental spillage with Lorsban^® 480 BR at the biobed. A semi-field experiment was conducted for 420 days in southern Brazil, testing continuous disposal of washing pulverization tanks in biobeds, Typic Haploperox or Typic Hapludults. In addition, different biobeds received a single dose (1 L) of Lorsban^® 480 BR to simulate an accidental spillage. Chronic ecotoxicity tests were performed using Folsomia candida, Eisenia andrei, and Enchytraeus crypticus in different sampling times for both experiments. F. candida was the most sensitive species. The biobed system was able to eliminate effects from residues of both pesticides over time in all species, which did not happen in both natural soils. In accidental spillage simulation, even 420 days after contamination, F. candida did not show reproduction. The biobeds can be a feasible alternative for the disposal and treatment residues of pesticides, also for handling and washing pesticides activities. The system was efficient in promoting degradation and reducing ecotoxicity effects posed by Lorsban^® 480 BR and Dithane^® NT for soil fauna. It is a safe alternative to avoid soil contamination.

Environmental risk assessment of pesticides in tropical terrestrial ecosystems: Test procedures, current status and future perspectives

Despite the increasing use of pesticides in tropical countries, research and legislative efforts have focused on their temperate counterparts. This paper presents a review of the literature on environmental risk assessment of pesticides for tropical terrestrial agroecosystems. It aims at evaluating potential differences in pesticide risk between temperate and tropical regions as well as to highlight research needs in the latter. Peculiarities of pesticide risks in tropical terrestrial agroecosystems are discussed in subsections 1) agricultural practices; 2) research efforts; 3) fate and exposure; 4) toxicity testing methods; and 5) sensitivity. The intensive and often inadequate pesticide application practices in tropical areas are likely to result in a relatively greater pesticide exposure in edge-of-field water bodies. Since pesticide fate may be different under tropical conditions, tropical scenarios for models estimating predicted environmental pesticide concentrations should be developed. Sensitivity comparisons do not indicate a consistent similar, greater or lower relative sensitivity of tropical soil organisms as compared to temperate organisms. However, several methods and procedures for application in the tropics need to be developed, which include: 1) identifying and collecting natural soils to be used as reference test substrates in tests; 2) identifying and discerning the range of sensitivity of native test species to soil contaminants; 3) developing test guidelines applicable to tropical/subtropical conditions; and 4) developing methods and procedures for higher tier testing for full development and implementation of environmental risk assessment schemes.

Soil ecotoxicology in Latin America: Current research and perspectives

Soils from some Latin American countries support the highest biodiversity levels on the planet and simultaneously have some of the most serious environmental impacts attributed to both historical and current agricultural practices and industrial activities. Soil contamination has resulted from intensive use of pesticides, extensive mining and other industrial activities, and uncontrolled management of waste within inappropriate regulatory frameworks. The present study presents an overview of the scientific research on soil ecotoxicology conducted in Latin America, summarizing the recent advances and highlighting the needs for further refinements in this research field. Most of the contributions to the scientific literature have been from Brazil. The most investigated issue is the ecotoxicity of pesticides and earthworms, which were the organisms most frequently used as test species. Needs identified by Latin American researchers include methods and procedures for: 1) identifying and collecting natural soils to be used as reference test-substrates in tests, 2) identifying and discerning the range of sensitivities of native test species to soil contaminants, 3) developing environmental guidelines applicable to tropical/subtropical conditions, and 4) developing methods and procedures for higher tier testing for full development and implementation of environmental risk assessment schemes. The protection of Latin American soils, including provision of goods and services, is currently framed in legislation and other regulations, but implementation requires significant improvement and additional training programs. Environ Toxicol Chem 2017;36:1795-1810. © 2017 SETAC.

Ecotoxicological risks of the abandoned F-Ba-Pb-Zn mining area of Osor (Spain)

Due to its potential toxic properties, metal mobilization is of major concern in areas surrounding Pb-Zn mines. In the present study, metal contents and toxicity of soils, aqueous extracts from soils and mine drainage waters from an abandoned F-Ba-Pb-Zn mining area in Osor (Girona, NE Spain) were evaluated through chemical extractions and ecotoxicity bioassays. Toxicity assessment in the terrestrial compartment included lethal and sublethal endpoints on earthworms Eisenia fetida, arthropods Folsomia candida and several plant species, whereas aquatic tests involved bacteria Vibrio fischeri, microalgae Raphidocelis subcapitata and crustaceans Daphnia magna. Total concentrations of Ba (250-5110 mg kg^-1), Pb (940 to >5000 mg kg^-1) and Zn (2370-11,300 mg kg^-1) in soils exceeded intervention values to protect human health. Risks for the aquatic compartment were identified in the release of drainage waters and in the potential leaching and runoff of metals from contaminated soils, with Cd (1.98-9.15 µg L^-1), Pb (2.11-326 µg L^-1) and Zn (280-2900 µg L^-1) concentrations in filtered water samples surpassing US EPA Water Quality Criteria (2016a, b). Terrestrial ecotoxicity tests were in accordance with metal quantifications and identified the most polluted soil as the most toxic. Avoidance and reproduction tests with earthworms showed the highest sensitivity to metal contamination. Aquatic bioassays performed in aqueous extracts from soils confirmed the results from terrestrial tests and also detected toxic effects caused by the mine drainage waters. Algal growth inhibition was the most sensitive aquatic endpoint. In view of the results, the application of a containment or remediative procedure in the area is encouraged.

Geochemistry and environmental threats of soils surrounding an abandoned mercury mine

The closure of mercury mining areas is generally associated with a release of Hg and other metals into the environment due to the abandonment of mining wastes. Because of their potential toxic properties, the mobilization of particulate and soluble metal species is of major concern. In the present study, the environmental risks posed by soils surrounding an abandoned mercury mining area in Valle del Azogue (Almeria, Spain) are assessed through the determination of physical-chemical parameters, the quantification of metal concentrations, and the application of aquatic and terrestrial ecotoxicity bioassays. Chemical analysis of soil samples revealed concentrations of Hg, As, Ba, Pb, Sb, and Zn above international intervention values. Results from terrestrial tests showed detrimental effects in all studied organisms (Eisenia foetida, Folsomia candida, and different plant species) and revealed the avoidance response of earthworms as the most sensitive endpoint. Surprisingly, the most toxic samples were not the ones with higher metal contents but the ones presenting higher electrical conductivity. Aquatic ecotoxicity tests with Vibrio fischeri, Raphidocelis subcapitata, Daphnia magna, and Danio rerio were in accordance with terrestrial tests, confirming the need to couple environmental chemistry with ecotoxicological tools for the proper assessment of metal-contaminated sites. In view of the results, a remediative intervention of the studied area is recommended.

Ecological Risk Assessment of a Metal-Contaminated Area in the Tropics. Tier II: Detailed Assessment

This study presents data on the detailed evaluation (tier 2) of a site-specific ecological risk assessment (ssERA) in a former smelter area contaminated with metals (Santo Amaro, Bahia, Brazil). Combining information from three lines of evidence (LoE), chemical (ChemLoE), ecotoxicological (EcotoxLoE) and ecological (EcoLoE), in the Triad approach, integrated risk values were calculated to rank sites and confirm the potential risk disclosed with tier 1. Risk values were calculated for the habitat and for the retention functions in each sampling point. Habitat function included the ChemLoE calculated from total metal concentrations. The EcotoxLoE was based on reproduction tests with terrestrial invertebrates (Folsomia candida, Enchytraeus crypticus, Eisenia andrei), shoot length and plant biomass (Avena sativa, Brassica rapa). For the EcoLoE, ecological parameters (microbial parameters, soil invertebrate community, litter breakdown) were used to derive risk values. Retention function included the ChemLoE, calculated from extractable metal concentrations, and the EcotoxLoE based on eluate tests with aquatic organisms (Daphnia magna reproduction and Pseudokirchneriella subcapitata growth). Results related to the habitat function indicated that the metal residues are sufficient to cause risk to biota, while the low metal levels in extracts and the general lack of toxicity in aquatic tests indicated a high soil retention capacity in most sampling points. Integrated risk of tier 2 showed the same trend of tier 1, suggesting the need to proceed with remediation actions. The high risk levels were related to direct toxicity to organisms and indirect effects, such as failure in the establishment of vegetation and the consequent loss of habitat quality for microorganisms and soil fauna. This study shed some light on the selection of tools for the tier 2 of an ssERA in tropical metal-contaminated sites, focusing on ecological receptors at risk and using available chemical methods, ecological surveys and ecotoxicity tests.

Ecotoxicological characterization of sugarcane vinasses when applied to tropical soils

The impact of sugarcane vinasse on soil invertebrates was assessed through ecotoxicological assays. Increasing concentrations of two vinasses from different distillery plants (VA and VB), and a vinasse from a laboratory production (VC), were amended on two natural tropical Oxisols (LV and LVA) and a tropical artificial soil (TAS) to characterize the effects of the vinasses on earthworms (Eisenia andrei), enchytraeids (Enchytraeus crypticus), mites (Hypoaspis aculeifer) and collembolans (Folsomia candida). The highest concentrations of VA and VB were avoided by earthworms in all soils and by collembolans especially in the natural soils. The presence of VC in all of the tested soils did not cause avoidance behavior in these species. The reproduction of earthworms, enchytraeids and collembolans was decreased in the highest concentrations of VA and VB in the natural soils. In TAS, VB reduced the reproduction of all test species, whereas VA was toxic exclusively to E. andrei and E. crypticus. The vinasse VC only reduced the number of earthworms in TAS and enchytraeids in LVA. The reproduction of mites was reduced by VB in TAS. Vinasses from distillery plants were more toxic than the vinasse produced in laboratory. The vinasse toxicities were influenced by soil type, although this result was most likely because of the way the organisms are exposed to the contaminants in the soils. Toxicity was attributed to the vinasses' high salt content and especially the high potassium concentrations. Data obtained in this study highlights the potential risk of vinasse disposal on tropical soils to soil biota. The toxic values estimated are even more relevant when considering the usual continuous use of vinasses in crop productions.