Fate of Pesticides in Surface Waters, Laboraty and Field Experiments

Fate of Pesticides in Surface Waters, Laboraty and Field Experiments

Appendix A. Preparation of pesticide solutions

For each pesticide concentration to be investigated, a pesticide solution of suitable concentration was made. In this way, the same volume of pesticide solution could be added to all flasks. In order to improve sedimentation during centrifugation (OECD 106), a solution of CaCl2 was used as the aqueous phase in the test tubes and thus also in the fabrication of pesticide solutions.

The following terms are used in the description of the preparation of pesticide solutions.

Original solution: The solution provided by supplier
Basic solution: A solution made by increasing the volume of the original solution with solvent or a solution made by dissolving solid pesticide with solvent
Stock solution: The solution from which the working solutions typically were made.
Working solutions: The solutions of different concentrations added to test tubes

The concentrations of the pesticide working solutions were determined by liquid scintillation counting (LSC) before use.

Pendimethalin

Stock solution

A stock solution was prepared by adding acetone to 0.1 mL of the original solution (C = 121 µCi/mL) in a 10-mL measuring flask, resulting in a concentration of 1.21 µCi/mL or 21.8 mg/L. Three 10-µL samples were analysed and the average concentration was 2682700 ± 48900 dpm/mL or 1.21 µCi/mL

Kinetic experiments with pond sediment

A low concentration working solution was prepared by adding 1 mL of the stock solution (C = 1.21 µCi/mL) to a-200 mL measuring flask and adjusting volume to 200 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.00606 µCi/mL or 0.109 mg/L. Three samples of this solution were analysed (counted) and the concentration was 11772 ± 367 dpm/mL, which equals 0.00530 µCi/mL or 0.0960 mg/L (S.D. 1.56%).

A high concentration working solution was prepared by adding 2 mL of the stock solution (C = 1.2127 µCi/mL) to a 200-mL measuring flask and adjusting volume to 200 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.0121 µCi/mL or 0.219 mg/L. Three samples of this solution were analysed (counted) and the concentration was 24285 ± 1354 dpm/mL, which equals 0.0109 µCi/mL or 0.197 mg/L (S.D. 2.79%).

Kinetic and equilibrium experiments with stream sediment

A high concentration working solution was prepared by adding 2 mL of the stock solution (C = 1.21 mCi/mL) to a 250-mL measuring flask and adjusting volume to 250 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.00970 µCi/mL or 0.175 mg/L. Three samples of this solution were analysed (counted) and the concentration was 14636 ± 273 dpm/mL, which equals 0.00659 µCi/mL or 0.119 mg/L (S.D. 0.93%).

A medium concentration working solution was prepared by adding 0.5 mL of the stock solution (C = 1.21 mCi/mL) to a 100-mL measuring flask and adjusting volume to 100 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.00606 µCi/mL or 0.109 mg/L. Three samples of this solution were analysed (counted) and the concentration was 11485 ± 468 dpm/mL, which equals 0.00517 µCi/mL or 0.0933 mg/L (S.D. 1.0%).

A low concentration working solution was prepared by adding 25 mL of the medium concentration solution (C = 0.00606 mCi/mL) to a 50-mL measuring flask and adjusting volume to 50 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.00303 µCi/mL or 0.0547 mg/L. Two samples of this solution were analysed (counted) and the concentration was 4429 ± 9.19 dpm/mL, which equals 0.00200 µCi/mL or 0.0361 mg/L (S.D. 0.4%).

Kinetic experiments with Lake Vaparanta sediment

The above stock solution was used.

Experiments with temperature variation, lake sediments

A high concentration working solution was prepared by adding 2 mL of the stock solution (C = 1.21 mCi/mL) to a 250-mL measuring flask and adjusting volume to 250 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.00970 µCi/mL or 0.175 mg/L. Three samples of this solution were analysed (counted) just before use and the concentration was 15904 ± 930 dpm/mL, which equals 0.0072 µCi/mL or 0.129 mg/L (S.D. 5.8%).

Desorption experiments

A low concentration working solution was prepared by adding 1 mL of the stock solution (C = 1.2127 µCi/mL) to a 200-mL measuring flask and adjusting volume to 200 mL with a 0.01-M CaCl2 millipore water solution. This made a nominal concentration of 0.00606 µCi/mL or 0.109 mg/L. Three samples of this solution were analysed (counted) and the concentration was 11255 ± 68 dpm/mL, which equals 0.0051 µCi/mL or 0.092 mg/L (S.D. 0.60%).

A high concentration working solution was prepared by adding 2 mL of the stock solution (C = 1.2127 mCi/mL) to a 200-mL measuring flask and adjusting volume to 200 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.0121 µCi/mL or 0.219 mg/L. Three samples of this solution were analysed (counted) and the concentration was 23276 ± 457 dpm/mL, which equals 0.0105 µCi/mL or 0.189 mg/L (S.D. 1.97%).

Degradation experiments

The above stock solution was used.

Ioxynil

Basic solution

A basic solution was prepared by dissolving 3.8 mg of ioxynil/0.28 mCi in 100 mL of acetone making a concentration of 2.8µCi/mL or 38 mg/L.

Stock solution

From the basic solution, a stock solution prepared made by adding 5 mL of the basic solution to a 25-mL measuring flask and adjusting to 25 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.56 µCi/mL or 7.6 mg/L.

Kinetic and equilibrium sorption experiments

A high concentration working solution was prepared by adding 5 mL of the stock solution to a 100-mL measuring flask and adjusting to 100 mL with a 0.01-M CaCl₂ millipore water solution. This made a nominal concentration of 0.028

µCi/mL or 0.38 mg/L. Three samples of this solution were counted and the concentration was 68558 ± 846 dpm/mL, which equals 0.031 µCi/mL or 0.43 mg/L (S.D. 0.3%).

A low concentration working solution was prepared by adding 5 mL of the high concentration solution to a 50-mL measuring flask and adjusting to 50 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.0028

µCi/mL or 0.038 mg/L. Two samples of this solution were counted and the concentration was 6137 ± 12.7 dpm/mL, which equals 0.0028 µCi/mL or 0.038 mg/L (S.D. 0.4%).

A medium concentration ioxynil working solution was prepared by adding 2 mL of the basic solution to a 250-mL measuring flask and adjusting to 250 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.022

µCi/mL or 0.30 mg/L. Three samples of this solution were counted and the concentration was 50563 ± 1814 dpm/mL, which equals 0.023 µCi/mL or 0.31 mg/L (S.D. 1.8%).

Experiments with temperature variation, lake sediments

Solution of radiolabelled ioxynil

µCi/mL or 0.30 mg/L. Three samples of this solution were counted just before use and the concentration was 50097 ± 1179 dpm/mL, which equals 0.023

µ Ci/mL or 0.31 mg/L (S.D. 2.3%).

Degradation experiments

Stock solution in acetone

From the basic solution a stock solution (nominal 0.56 µCi/mL or 7.6 mg/L) was prepared by adding 10 mL of the basic solution to 40 mL acetone in a measuring flask. Three 10-µL samples were analysed and the average concentration was 1409600 ± 37700 dpm/mL or 0.63 µCi/mL.

Bentazone

Basic solution

The original solution (2 mL) was added to a 100-mL measuring flask and the volume was adjusted to 100 mL with acetone resulting in a basic solution with a nominal concentration of 2.5 µCi/mL or 7500 mg/L

Stock solution

A stock solution was prepared by adding 5 mL of the basic solution to a 25-mL measuring flask and adjusting to 25 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.50 µCi/mL or 1500 mg/L.

Equilibrium sorption experiments

A high concentration working solution was prepared by adding 2 mL of the stock solution to a 100-mL measuring flask and adjusting to 100 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.010 µCi/mL or 30 mg/L. Three samples of this solution were counted and the concentration was 31075 ± 601 dpm/mL, which equals 0.014 µCi/mL or 42.0 mg/L (S.D. 0.48%).

A medium concentration working solution was prepared by adding 5 mL of the high concentration solution to a 50-mL measuring flask and adjusting to 50 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.001 µCi/mL or 3.0 mg/L. One sample of this solution was counted and the concentration was 2906 dpm/mL, which equals 0.0013 µCi/mL or 3.9 mg/L.

A low concentration working solution was prepared by adding 1 mL of the high concentration solution to a 50-mL measuring flask and adjusting to 50 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.00020 µCi/mL or 0.60 mg/L. Two samples of this solution were counted and the concentration was 509 ± 45.2 dpm/mL, which equals 0.00023 µCi/mL or 0.69 mg/L.

Experiments with temperature variation, lake sediments

A medium concentration working solution was prepared by adding 0.5 mL of the stock solution to a 200-mL measuring flask and adjusting to 200 mL with a 0.01-M CaCl2 millipore water solution making a nominal concentration of 0.0013

µCi/mL or 3.75 mg/L. Three samples of this solution were counted and the concentration was 4028 ± 56 dpm/mL, which equals 0.0018 µCi/mL or 5.4 mg/L.

Degradation experiments

Stock solution in acetone

From the basic solution, a stock solution (nominal 0.50 µCi/mL or 1500 mg/L) was prepared by adding 10 mL of the basic solution to 40 mL of acetone in a measuring flask. Three samples of 10 µL were analysed and the concentration was 1656400 ± 22000 dpm/mL or 0.75 µCi/mL.

Preparation of other solutions

A 30-mmol/L NaN3 solution was prepared from a 1-M stock solution by adding 6 mL of stock solution to a 200-mL measuring flask and adding millipore water. CaCl2

H2O was added to a concentration of 0.01 M CaCl2.

0.01-M CaCl2 solutions were prepared by adding 1.47 g CaCl2

2H2O to a 1000-mL measuring flask and adjusting the volume to 1000 mL with millipore water.