Introduction

Learning to conjugate contaminar — “to pollute, to contaminate” — opens up a whole set of sentences you will use in real Spanish. Whether you are talking about what you do every day, what happened yesterday, or what you plan to do tomorrow, contaminar is one of the verbs that carries those sentences, especially when the topic is the river. On this page you will find the full conjugation of contaminar in all thirteen tenses, notes on when to use each one, example sentences, the mistakes learners make most often, a ten-question quiz and answers to the questions students ask about this verb. contaminar is a regular -ar verb; the gerund is contaminando and the past participle is contaminado, and both appear in the tables and examples below. For example: “Yo contamino el río todos los días.” — “I pollute the river.” Read the tables first, then the notes, and finish with the quiz to check what you have learned.

Quick facts
Infinitive contaminar
English to pollute, to contaminate
Verb type Regular -ar verb
Gerund contaminando
Past participle contaminado
Auxiliary verb haber

Full conjugation tables

Gerund: contaminando · Past participle: contaminado

Present Indicative

Person Form
yo contamino
tú contaminas
él/ella/Ud. contamina
nosotros/as contaminamos
vosotros/as contamináis
ellos/ellas/Uds. contaminan

The present tense describes habits, facts and what is happening now. For contaminar, the yo form is contamino, as in “Yo contamino el río.” — “I pollute the river.”

Preterite

Person Form
yo contaminé
tú contaminaste
él/ella/Ud. contaminó
nosotros/as contaminamos
vosotros/as contaminasteis
ellos/ellas/Uds. contaminaron

The preterite describes completed actions in the past — things that started and finished. For contaminar, the yo form is contaminé, as in “Yo contaminé el río.” — “I polluted the river.”

Imperfect

Person Form
yo contaminaba
tú contaminabas
él/ella/Ud. contaminaba
nosotros/as contaminábamos
vosotros/as contaminabais
ellos/ellas/Uds. contaminaban

The imperfect describes the past as background: habits, descriptions and actions in progress. For contaminar, the yo form is contaminaba, as in “Yo contaminaba el río.” — “I used to pollute the river.”

Future

Person Form
yo contaminaré
tú contaminarás
él/ella/Ud. contaminará
nosotros/as contaminaremos
vosotros/as contaminaréis
ellos/ellas/Uds. contaminarán

The future tense states what will happen. It is also used for predictions and promises. For contaminar, the yo form is contaminaré, as in “Yo contaminaré el río.” — “I will pollute the river.”

Conditional

Person Form
yo contaminaría
tú contaminarías
él/ella/Ud. contaminaría
nosotros/as contaminaríamos
vosotros/as contaminaríais
ellos/ellas/Uds. contaminarían

The conditional expresses what would happen: wishes, polite requests and hypothetical results. For contaminar, the yo form is contaminaría, as in “Yo contaminaría el río.” — “I would pollute the river.”

Present Perfect

Person Form
yo he contaminado
tú has contaminado
él/ella/Ud. ha contaminado
nosotros/as hemos contaminado
vosotros/as habéis contaminado
ellos/ellas/Uds. han contaminado

The present perfect connects the past with the present: something that has happened, often today or recently. For contaminar, the yo form is he contaminado, as in “Yo he contaminado el río.” — “I have polluted the river.”

Pluperfect

Person Form
yo había contaminado
tú habías contaminado
él/ella/Ud. había contaminado
nosotros/as habíamos contaminado
vosotros/as habíais contaminado
ellos/ellas/Uds. habían contaminado

The pluperfect describes an event that happened before another past event. For contaminar, the yo form is había contaminado, as in “Yo había contaminado el río.” — “I had polluted the river.”

Future Perfect

Person Form
yo habré contaminado
tú habrás contaminado
él/ella/Ud. habrá contaminado
nosotros/as habremos contaminado
vosotros/as habréis contaminado
ellos/ellas/Uds. habrán contaminado

The future perfect describes something that will already be finished by a future moment. For contaminar, the yo form is habré contaminado, as in “Yo habré contaminado el río.” — “I will have polluted the river.”

Conditional Perfect

Person Form
yo habría contaminado
tú habrías contaminado
él/ella/Ud. habría contaminado
nosotros/as habríamos contaminado
vosotros/as habríais contaminado
ellos/ellas/Uds. habrían contaminado

The conditional perfect describes what would have happened under different conditions. For contaminar, the yo form is habría contaminado, as in “Yo habría contaminado el río.” — “I would have polluted the river.”

Present Subjunctive

Person Form
yo contamine
tú contamines
él/ella/Ud. contamine
nosotros/as contaminemos
vosotros/as contaminéis
ellos/ellas/Uds. contaminen

The present subjunctive is used after expressions of wish, doubt, emotion and influence. For contaminar, the yo form is contamine, as in “Espero que yo contamine el río.” — “I hope that I pollute the river.”

Imperfect Subjunctive (-ra)

Person Form
yo contaminara
tú contaminaras
él/ella/Ud. contaminara
nosotros/as contamináramos
vosotros/as contaminarais
ellos/ellas/Uds. contaminaran

The imperfect subjunctive is used in the past versions of subjunctive clauses, and after "si" in hypothetical sentences. For contaminar, the yo form is contaminara, as in “Si yo contaminara el río, ...” — “If I polluted the river, ...”

The -se variant of this tense follows the same pattern with -se instead of -ra: contaminara becomes contaminase, and the same change applies to every person. Both variants mean the same thing; -ra is more common in everyday speech.

Imperative (affirmative)

Person Form
tú contamina
Ud. contamine
nosotros/as contaminemos
vosotros/as contaminad
Uds. contaminen

Imperative (negative)

Person Form
tú contamines
Ud. contamine
nosotros/as contaminemos
vosotros/as contaminéis
Uds. contaminen

The imperative is for orders, requests and advice. The affirmative tú form is contamina, as in “¡Contamina el río” — “Pollute the river” For the negative imperative, Spanish uses the subjunctive forms: no contamines. Note that the affirmative and negative forms differ, so check the table above before you give an order with contaminar.

Example sentences

Here are ten sentences with contaminar, covering different tenses and persons. Read each one out loud, then read the translation, and notice how the verb form changes while the meaning stays the same.

  1. “Yo contamino el río cada día.” — “I pollute the river.”
  2. “Él contamina el río todos los días.” — “He pollutes the river.”
  3. “Yo contaminé el río ayer.” — “I polluted the river.”
  4. “Él contaminó el río ayer.” — “He polluted the river.”
  5. “Yo contaminaba el río cuando era joven.” — “I used to pollute the river.”
  6. “Nosotros contaminaremos el río mañana.” — “We will pollute the river.”
  7. “Si pudiera, yo contaminaría el río.” — “If I could, i would pollute the river.”
  8. “Yo he contaminado el río hoy.” — “I have polluted the river.”
  9. “Espero que yo contamine el río.” — “I hope that I pollute the river.”
  10. “estoy contaminando el río ahora mismo.” — “I am polluting the river.”

Common mistakes

Forgetting the accent in the preterite

The yo preterite form is contaminé, with an accent on the stressed vowel. Writing it without the accent — contamine — is a spelling error, and in speech the stress lands in the wrong place. Preterite yo forms that end in a vowel carry that accent, so check it every time you write the preterite of contaminar.

Mixing up present and preterite nosotros

For contaminar, the nosotros form is the same in the present and the preterite: contaminamos. Only the context tells you which tense is meant, so pay attention to the time words around it — cada día points to the present, ayer points to the preterite. Do not invent a different form for one of the tenses.

Using ser instead of haber in perfect tenses

Spanish perfect tenses always use haber, never ser: yo he contaminado el río. English speakers sometimes reach for soy because English uses to be in some passives, but soy contaminado is not the present perfect of contaminar — it is a passive construction with a different meaning.

Confusing contaminar with conservar

contaminar and conservar look similar, and learners mix them up. They are different verbs with different meanings, so check which one the sentence needs before you conjugate. If you can substitute the English meaning of contaminar — pollute — the sentence needs contaminar; if it needs the meaning of conservar, use that verb instead.

Using the indicative after "espero que"

After espero que (I hope that), Spanish needs the subjunctive: Espero que yo contamine el río. Using the indicative — Espero que yo contamino — is one of the most frequent learner errors with contaminar. Whenever the main clause expresses a wish, doubt or emotion, switch to the subjunctive.

Quiz

Test yourself on the forms above. Choose the best answer, then check the key below.

1. What is the yo form of contaminar in the present?

  • A. contaminas
  • B. contamina
  • C. contaminamos
  • D. contamino

2. What is the tu form of contaminar in the preterite?

  • A. contaminamos
  • B. contaminaste
  • C. contaminé
  • D. contaminó

3. What is the el form of contaminar in the imperfect?

  • A. contaminabas
  • B. contaminábamos
  • C. contaminabais
  • D. contaminaba

4. What is the nosotros form of contaminar in the future?

  • A. contaminará
  • B. contaminaremos
  • C. contaminaré
  • D. contaminarás

5. What is the vosotros form of contaminar in the present perfect?

  • A. he contaminado
  • B. has contaminado
  • C. ha contaminado
  • D. habéis contaminado

6. What is the ellos form of contaminar in the present subjunctive?

  • A. contamine
  • B. contaminen
  • C. contamine
  • D. contamines

7. What is the yo form of contaminar in the preterite?

  • A. contaminaste
  • B. contaminó
  • C. contaminamos
  • D. contaminé

8. What is the tu form of contaminar in the imperfect?

  • A. contaminábamos
  • B. contaminabas
  • C. contaminaba
  • D. contaminaba

9. What is the el form of contaminar in the future?

  • A. contaminaré
  • B. contaminarás
  • C. contaminaremos
  • D. contaminará

10. What is the nosotros form of contaminar in the conditional?

  • A. contaminaría
  • B. contaminaríamos
  • C. contaminaría
  • D. contaminarías

Answer key

  1. contamino — The present table gives yo = contamino.
  2. contaminaste — The preterite table gives tu = contaminaste.
  3. contaminaba — The imperfect table gives el = contaminaba.
  4. contaminaremos — The future table gives nosotros = contaminaremos.
  5. habéis contaminado — The present perfect table gives vosotros = habéis contaminado.
  6. contaminen — The present subjunctive table gives ellos = contaminen.
  7. contaminé — The preterite table gives yo = contaminé.
  8. contaminabas — The imperfect table gives tu = contaminabas.
  9. contaminará — The future table gives el = contaminará.
  10. contaminaríamos — The conditional table gives nosotros = contaminaríamos.

Frequently asked questions

Is contaminar regular or irregular?

contaminar is a regular -ar verb. It follows the regular patterns for its ending in every tense. The tables on this page show the correct form for every person, so use them rather than guessing.

What is the past participle of contaminar?

The past participle of contaminar is contaminado. You use it with haber in the perfect tenses — he contaminado, había contaminado, habré contaminado — and after estar in passive-style descriptions. It is the regular participle for its verb class. Learn it together with the gerund contaminando and you have the two non-finite forms covered.

What is the gerund of contaminar?

The gerund of contaminar is contaminando. You use it with estar to describe an action in progress, as in estoy contaminando, and after verbs such as seguir and ir. Keep it distinct from the past participle contaminado, which belongs with haber, not with estar.

What is the yo form of contaminar in the present?

The yo form is contamino — “Yo contamino el río.” means “I pollute the river.” That is the form you will use most often when you talk about yourself. For other persons, use the present table above: tú contaminas, él contamina, nosotros contaminamos, ellos contaminan.

What is the difference between contaminar and conservar?

contaminar means “to pollute, to contaminate”, while conservar means “to preserve, to keep”. They share letters and sometimes a root, but they are different verbs. If your sentence means “to pollute, to contaminate”, use contaminar; if it is about the meaning of conservar, use conservar instead. Checking the English meaning first prevents most mix-ups.

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