Two plants that are potentially effective for mixing their juices together to remove toxic substances in the environment are:

1. Aloe vera: Aloe vera is known for its detoxifying properties and ability to remove toxins from the body. Mixing aloe vera juice with watercress juice can create a powerful detox solution that can help in removing harmful substances from the environment.

2. Lemon: Lemon juice is a natural disinfectant and is often used for cleaning purposes. Mixing lemon juice with watercress juice can create a potent cleansing solution that can help in removing toxins and impurities from the environment.

How it can be done

1. Harvest fresh aloe vera and watercress leaves.

2. Extract the juice from the aloe vera leaves by cutting them open and scooping out the gel.
3. Extract the juice from the watercress leaves by blending them with a little water and then straining the mixture through a cheesecloth to separate the juice.
4. Mix the aloe vera juice and watercress juice together in a container.
5. Use a spray bottle to apply the mixture to contaminated areas in the environment, such as soil or water sources.
6. Allow the mixture to sit for some time before rinsing it off or wiping it clean.
7. Repeat the process as needed until the desired results are achieved.

Remember to wear gloves and protective gear when handling potentially toxic substances and to always follow safety guidelines when cleaning up contaminated areas.