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Pesticides
The Pesticides family includes thirty-eight molecules in the IsoFind catalog, making it the most extensive category. It covers the major classes still detected today in European groundwater and soil, including banned but persistent molecules (atrazine, DDT, lindane) and authorized molecules subject to regulatory monitoring (glyphosate, neonicotinoids, triazoles). This page presents the family structure, applicable regulatory thresholds, tabulated degradation pathways, and available CSIA data.
The Sixteen Sub-families
Pesticides are grouped into sixteen sub-families reflecting standard chemical classification. The most numerous correspond to legacy classes (triazines, organophosphates) and recent classes under increased surveillance (neonicotinoids, chloroacetamides).
| Sub-family | Count | Representative Examples |
|---|---|---|
| Triazines | 6 | Atrazine, simazine, terbutylazine, DEA, DEIA |
| Organophosphates | 5 | Chlorpyrifos, diazinon, malathion, fenitrothion |
| Neonicotinoids | 5 | Imidacloprid, clothianidin, thiamethoxam, acetamiprid, thiacloprid |
| Chloroacetamides | 4 | Metolachlor, S-metolachlor, acetochlor, metazachlor |
| Phenylureas | 3 | Diuron, isoproturon, linuron |
| Organochlorines (incl. HCH & DDT) | 4 | Dieldrin, endosulfan, DDT, lindane |
| Phosphonates | 2 | Glyphosate, AMPA |
| Triazoles and Fungicides | 3 | Tebuconazole, propiconazole, tetraconazole |
| Pyrethroids | 2 | Cypermethrin, deltamethrin |
| Others | 4 | Carbendazim, spinosad, trifluralin, metribuzin |
Regulatory Thresholds
Nearly all pesticides in the catalog are governed by two European regulatory frameworks: Directive 98/83/EC (drinking water, individual threshold of 0.10 µg/L) and the Water Framework Directive 2013/39/EU and its updates (AA-EQS environmental quality standards for surface water). The actual threshold applied depends on the specific molecule and the target matrix.
| Threshold Category | Typical Value | Affected Pesticides (Examples) |
|---|---|---|
| Dir. 98/83/EC Drinking Water | 0.10 µg/L (individual) | Atrazine, simazine, diuron, glyphosate, AMPA, terbutylazine |
| WFD Standard AA-EQS | 0.10 to 0.30 µg/L | Atrazine (0.60), isoproturon (0.30), diuron (0.20), metolachlor (0.10) |
| WFD Priority Hazardous AA-EQS | 0.005 to 0.030 µg/L | Endosulfan (0.005), dieldrin (0.010), DDT (0.025), chlorpyrifos (0.030) |
| WFD 2022/1441 Neonicotinoids | 0.013 µg/L | Imidacloprid, clothianidin, thiamethoxam |
| WFD AA-EQS Pyrethroids | 0.0002 µg/L | Cypermethrin, deltamethrin |
Thresholds vary by several orders of magnitude between a standard pesticide (0.10 µg/L) and a pyrethroid (0.0002 µg/L). Reporting measurements in ng/L rather than µg/L is crucial for the latter: apparent compliance in µg/L can mask an exceedance by a factor of 500 for a pyrethroid. IsoFind normalizes this automatically, but vigilance during data entry remains necessary.
Parent-Metabolite Pairs
Several pesticides in the catalog are accompanied by their metabolites within the same family, allowing for chain-reaction processing. Directive 98/83/EC treats metabolites with the same 0.10 µg/L individual threshold, which simplifies regulatory interpretation.
| Parent | Metabolites in Catalog |
|---|---|
| Atrazine | Desethyl-atrazine (DEA), desethyl-deisopropyl-atrazine (DEIA) |
| Terbutylazine | Desethyl-terbutylazine |
| Glyphosate | AMPA |
Tabulated Degradation Pathways
Ten degradation pathways are tabulated for the pesticide family in the molecule_degradation_pathways database. Each pathway includes its favorable conditions, typical half-life, primary metabolite, and bibliographic reference.
| Molecule | Pathway | Environment | t½ (days) | Primary Metabolite |
|---|---|---|---|---|
| Atrazine | Biotic Dealkylation | Aerobic | 75 | DEA |
| Atrazine | Chemical Hydrolysis | Water-Soil | 300 | Hydroxyatrazine (HYA) |
| Atrazine | Complete Mineralization (Pseudomonas ADP) | Aerobic | 15 | Cyanuric acid → CO₂ + NH₃ |
| Simazine | Biotic Dealkylation | Aerobic | 90 | DEA-simazine |
| Diuron | Biotic N-demethylation | Aerobic | 90 | DCPMU |
| Diuron | Hydrolysis | Water | 1000 | 3,4-DCA |
| Glyphosate | Biotic Degradation via AMPA | Aerobic | 20 | AMPA |
| Glyphosate | Degradation via Sarcosine (rare) | Aerobic | 80 | Sarcosine |
| S-Metolachlor | Aerobic Biodegradation | Aerobic | 50 | Metolachlor-ESA |
| S-Metolachlor | Anaerobic Degradation | Anaerobic | 150 | Dechloro-metolachlor |
The coexistence of multiple pathways for a single molecule is the rule rather than the exception. Atrazine can degrade through three different pathways with half-lives ranging from 15 to 300 days and distinct metabolites. The dominant pathway depends on local conditions, which the Nexus engine and CSIA bridge handle automatically.
CSIA Data for Pesticides
The catalog contains isotopic fractionation data for six pesticides covering two main elements (carbon and nitrogen) and occasionally chlorine. This data enables CSIA isotopic diagnosis and coupling with the simulation engine.
| Molecule | Element | ε (‰) | Range | Λ (Coupling) | Reference |
|---|---|---|---|---|---|
| Atrazine | C | -5.4 | [-6.2 ; -4.5] | - | Meyer et al., 2009 |
| Atrazine | N | -2.4 | [-3.0 ; -1.8] | 0.44 | Meyer et al., 2009; Schürner et al. |
| Simazine | C | -5.0 | [-6.0 ; -4.0] | - | Meyer et al., 2009 |
| Diuron | C | -1.8 | [-2.5 ; -1.2] | - | Maier et al., 2013 |
| Diuron | N | -1.2 | [-2.0 ; -0.6] | 0.67 | Maier et al., 2013 |
| Glyphosate | C | -2.1 | [-2.8 ; -1.5] | - | Sandy et al., 2020; Adams et al., 2022 |
| Glyphosate | N | -3.8 | [-5.5 ; -2.5] | 1.8 | Adams et al., 2022 |
| S-Metolachlor | C (aerobic) | -1.5 | [-2.1 ; -0.8] | - | Alvarez-Zaldivar et al., 2018 |
| S-Metolachlor | C (anaerobic) | -3.0 | [-4.5 ; -2.0] | - | Droz et al., 2021 |
| S-Metolachlor | Cl | -5.5 | [-7.0 ; -4.0] | 0.55 | Droz et al., 2021 |
The coupling coefficient Λ (lambda) represents the expected slope in a dual isotope plot (Δδ element 2 vs. Δδ element 1). It is a powerful mechanistic discriminant: a Λ near 1 suggests control by a bond cleavage involving both elements, while a significantly different Λ suggests a pathway specific to only one of the two elements.
Case Study: Atrazine
Atrazine is the most comprehensive case in the pesticide catalog, with three tabulated degradation pathways, two CSIA elements (C and N), two explicitly recorded metabolites (DEA, DEIA), and extensive regulatory coverage. This richness makes it the reference case for illustrating the possibilities of IsoFind coupling within this family.
| Indicator | Interpretation |
|---|---|
| High Atrazine / DEA ratio (>1) | Recent input, low degradation or very recent degradation |
| Atrazine / DEA ratio < 1 | Active and advanced degradation, legacy input |
| Enriched δ¹³C (more positive than source) | Confirmed degradation |
| Dual δ¹³C / δ¹⁵N within Λ≈0.44 | Dominant biotic dealkylation |
| Dual δ¹³C / δ¹⁵N within Λ≈1.13 | Dominant abiotic hydrolysis |
API Access
Pesticide data is accessible via the molecule module endpoints by filtering for the family. The most useful endpoints for this family are listed below.
| Endpoint | Usage |
|---|---|
| GET /api/molecules/reference/catalogue?family=Pesticides | List of the 38 reference pesticides |
| POST /api/molecules/catalogue/seed/Pesticides | Pre-fills the project with the pesticides family |
| GET /api/molecules/csia/Atrazine/pathways | Lists tabulated degradation pathways for atrazine |
| POST /api/molecules/csia/resolve | Complete CSIA resolution for a molecule and specific conditions |
| POST /api/molecules/csia/dual | Dual isotope calculation with Λ for mechanistic diagnosis |
Learn More
- CSIA Isotopy: General principles of residual enrichment.
- Degradation Pathways: Full set of 50 tabulated pathways.
- Case Study: Pesticide Degradation: Atrazine simulation with CSIA coupling.
- Reference Database: Detailed structure of the molecular catalog.