DOI: 10.5281/zenodo.17602857
title: Pesticide residues, ecotoxicological risk quotients, soil properties and earthworm (Eisenia andrei, Perionyx excavatus and Pontoscolex corethrurus) reproduction in eighteen Brazilian soils

description: Material and Methods:

The current dataset presents the results of laboratory experiments evaluating the survival and reproduction of three earthworm species, two epigeic (Eisenia andrei and Perionyx excavatus) and one endogeic (Pontoscolex corethrurus) in bioassays using standard ecotoxicological protocols. Specimens of P. corethrurus were collected in an experimental area of Embrapa Forestry (Colombo, Paraná state), while E. andrei was obtained from a contaminant-free vermicomposter in Curitiba (Paraná state), and P. excavatus was purchased from Minhobox® in Juiz de Fora (Minas Gerais). All soils were maintained at 23 ± 2 ºC. Because of its longer life cycle, P. corethrurus was kept for 91 days, whie the other species were kept for the standard duration (56 days). Fresh biomass of adult earthworms (clitellates) ranged from 200-400 mg for E. andrei and P. excavatus, and 400-600 mg for P. corethrurus. Ten individuals were introduced into each of five test containers, after purging their guts in moistened filter paper for 24 h. Round 1L transparent plastic containers were used, allowing 6 cm soil depth. Each replicate received 500 g soil (dry weight equivalent). The lids had small holes allowing for gas exchange. Moisture (50% of the water holding capacity) was maintained by adding water weekly and food (horse manure, 8 g dry mass per container), added for earthworm growth and reproduction. Adult survival and biomass were assessed at 14 and 28 days for E. andrei and P. excavatus, and the adults removed after 28 days. For P. corethrurus, evaluations were at 14, 28, 42, 56, 84 and 91 days, and the adults removed at 91 days. Juvenile earthworms remained in the containers throughout the trial until its completion, when they were counted to evaluate reproduction. All unhatched cocoons of P. corethrurus and E. andrei were manually separated and counted; cocoons of P. excavatus were not quantified as they are too small and difficult to observe. 

Soils from 18 sites, including six under native vegetation and 12 under agricultural production were evaluated, half of them belonging to the Cerrado and the other to the Atlantic Forest biome, both considered global biodiversity hotspots. Soils were collected in December 2023 and January 2024 from four land use systems: 1) annual cropping with consolidated no-tillage system (NTS) following the conservation agriculture principles, including no soil mobilization in the last 10 years and using crop rotation and cover crops; 2) annual cropping under no-tillage (NT) not following the principles of conservation agriculture; 3) bare conventionally tilled soil (CT) recently prepared for pasture sowing; and 4) native vegetation (NV). The sites were located in six municipalities in five states: Mangueirinha and Carambeí (both in Paraná) and Panambi (Rio Grande do Sul), belonging to the Atlantic Forest biome; Lucas do Rio Verde (Mato Grosso), Conquista (Minas Gerais), and Formosa do Rio Preto (Bahia), belonging to the Cerrado biome. The soils were predominantly classified as red or red-yellow Latosols or Nitosols, according to the Brazilian Soil Classification system. Around 5 kg of soil was collected from the top 0-10 cm at three points at each site distant 50 m from each other, and combined to make a large composite sample. The soils were defaunated by three freezing cycles, and a sub-sample was removed for pesticide residue, chemical, and particle size analysis. Standardized Tropical Artificial Soil (TAS), composed of 75% fine sand (<0.05 mm), 20% kaolin, and 5% coconut shell fiber powder, was used as a control.

Soil texture and chemical analyses accompanied the determination of 48 pesticide residues. The soil was analyzed for micro and macronutrients, base saturation, Cation Exchange Capacity (CEC), available-P (Mehlich and anion exchange resin-extractable) and pH in CaCl2 following standard methods of the Instituto Agronômico de Campinas (IAC, 2001). Soil particle size distribution (sand, silt, and clay) was determined by the densimeter method, and the C and N contents determined after fractionation. Fourty-eight pesticides (active ingredients) used in grain production in Brazil were evaluated. Of these, 23 were herbicides (Alachlor, Ametryn, Atrazine, Bromacil, Carfentrazone, Clomazone, Diquat, Diuron, Fenoxaprop, Flazasulfurom, Hexazinone, Imazamox, Indaziflam, Linuron, Metribuzin, Oxadiazon, Picloram, Prometryn, Saflufenacyl, Sulfometuron methyl, Tebuthiuron, Terbuthylazine, and Glyphosate); 12 were fungicides (Azoxystrobin, Benalaxyl, Bromuconazole, Cyproconazole, Difenoconazole, Iprodione, Metalaxyl-M, Propamocarb, Pyraclostrobin, Tebuconazole, Triadimenol, and Trifloxystrobin); and 13 were insecticides (Acetamiprid, Acephate, Chlorfluazuron, Dimethoate, Fenpropathrin, Fenpyroxamate, Imidacloprid, Malathion, Methamidofos, Methidathion, Methomyl, Thiacloprid, Thiamethoxam). Additionally, the metabolite of glyphosate degradation, aminomethylphosphonic acid (AMPA) was evaluated. Pesticide extraction from soil followed a modified method briefly described in the associated paper, and which will be described in a future manuscript. 

The lethal concentration values (mg kg⁻¹) for 50% mortality of the earthworm Eisenia fetida (LC50), and the no-observed-effect concentration (NOEC) values of the active ingredients of 28 pesticides were taken from the Pesticide Properties Database (https://sitem.herts.ac.uk/aeru/ppdb/). The Predicted No-Effect Concentration (PNEC) was obtained by using the most sensitive endpoint for earthworm toxicity  (either NOEC, or if not available LC50), and adopting an assessment factor of 10 (used when NOEC values were available) or 100 (when only LC50 values were available). Individual Risk Quotients (RQi) were calculated for each pesticide by dividing the measured concentration of 28 pesticides in the soils at each site by the appropriate PNEC. When not detected, RQi values of 0 were used. The total risk quotient for each of the 18 soils (ΣRQsite) was calculated by summing all RQis, assuming additive effects of the pesticides encountered. Total risk of the pesticide residues at each site (ΣRQsite) was assessed by using the following categories: medium, when 0.1≤ΣRQsite<1, and high when ΣRQsite≥1. 

This data supports the accepted publication in Environmental Toxicology and Chemistry, titled: Pesticides residues and earthworm reproduction in eighteen Brazilian soils, led by the 1st author, as part of his PhD requirements at the Federal University of Paraná. 

Acknowledgements:

This work is part of the project “No-Till System – Basis for Sustainable Agriculture”, proposed by The Ministry of Agriculture, Livestock and Supply (MAPA) of Brazil, and executed and coordinated scientifically by the Brazilian Federation of No-till System (FEBRAPDP). It was also part of the PhD thesis in Soil Science of the first author at the Federal University of Paraná (UFPR), with the title: "Avaliação da função habitat do solo de sistemas de uso para as minhocas em dois biomas brasileiros". Logistical support was provided by UFPR, FEBRAPDP, and the Brazilian Corporation for Agricultural Research (Embrapa). Permits (license No. 18128) for collecting earthworms were obtained from IBAMA (to G. Brown). Financial support was provided by grants: No. 23-SB1613 of the EU Euroclima+ Fund, managed by Expertise France, AFD Group; PA4122/25 of the Agrisus Foundation; CAPES doctoral scholarship (to R. Roani); No. 312824/2022-0 from the Brazilian National Council for Scientific and Industrial Research (CNPq); No. 406747/2022-9 and SEI 01300.010795/2023-47, as an FAPT/CNPq INCT grant on Terrestrial Ecotoxicology. The authors thank all the farmers involved for allowing access to their properties and for support in many different ways, including lodging, provisions, and meals. Without their help this work would not have been possible.

Description of the dataset:

The dataset contains nine data tabs as well as a Legend and Metadata tab. These are explained as follows:

Metadata tab: This contains a brief description of the tabs and each of their contents in the dataset

Legend tab: Description of meanings of each of the variables and the abbreviations used in the datatabs

Site_description tab: General information related to each site sampled (e.g., coordinates, sampling date, etc.)

Soil_Analysis tab: Results of the chemical (pH, OM, macro and micronutrients), physical (particle size distribution) soil analyses 

Pesticide_Residues tab: Pesticide residues or metabolites measured and those actually detected in soils (mg Kg-1 of soil)

RQi tab = Risk Quotients calculated individually for each pesticide

RQi_Prop tab = Proportion of the total estimated risk (ΣRQi) for each pesticide

Fractionation tab: Fractionation of organic matter into sand, silt and clay fractions, and their C and N contents

Earthworm_reproduction tab: Number of cocoons and juveniles of each species per soil and their biomass, number of adults at the end of each bioassay

Earthworm_biomass tab: Biomass of adult earthworms in each soil and per day of observation

Earthworm_survival tab: Number of adults in each soil and per day of observation.