Are there any references to the word 'purushartha' in vedas?
The Suryopanishad is a minor Upanishad allied to the Atharva Veda.It has the word Purushartha in it.
aum atha sūryātharvāṅgirasam vyā̎khyāsyā̱maḥ | brahmā ṟṣih | gāya̍trī chha̱ndaḥ | ādi̍tyo de̱vatā | haṁsa̍ḥ so̱’ham agni nārāyana yu̍ktam bī̱jam | hrille̍khā śa̱ktiḥ | viyadādi sarga saṁyu̍ktaṁ kī̱lakam | catur-vidha puruṣārtha siddhyarthe jape vi̍niyo̱gaḥ ||
Now we shall expound mantras of Atharva Veda in relation to the Sun: The seer of this Atharva Aṅgirasa
mantra is Brahma, metre Gayatri, Aditya the deity, ‘Hamsas so’ham with Agni and Narayana is the seed,
the power is hrillekha or hrim, the pin is the power in the process of unfolding the sky etc., the application is its use in repetition for winning the four human goals (viz. Dharma, Artha, Kama and Mokṣa).
You can also read the Suryopanishad from here.
Note for Suresh-I have assumed that you wanted the references from any Sruti texts(Vedas,Upanishads ).But,if you want specifically from the Vedas only then i need to delete my answer.Hence,waiting for your response.
An update-We also find mention of the Chaturvida Purusharthas (viz Dharma,artha,kama & moksha) in another minor Upanishad text called the Ganapty Atharvashrisha Upanishad
सायमधीयानो दिवसकृतं पापं नाशयति । प्रातरधीयानो रात्रिकृतं पापं नाशयति । सायं प्रातः प्रयुञ्जानो पापोऽपापो भवति । सर्वत्राधीयानोऽपविघ्नो भवति । धर्मार्थकाममोक्षं च विन्दति ॥१३॥
This is verse no. 13 with meanings as given below:
13.5: Studying this in the Evening will destroy the Sins committed during the Day (including the tendency to commit Sins), 13.6: Studying this in the Morning will destroy the Sins committed during the Night (including the tendency to commit Sins), 13.7: Joining (the Study and Deep Contemplation) both in the Evening and Morning, will make a Sinful person Sinless (by gradually revealing the deeper consciousness and thereby removing the tendencies to commit Sins), 13.8: Studying everywhere (i.e. in all situations) will remove the Obstacles, ... 13.9: ... (And) the Devotee will obtain Dharma, Artha (Prosperity), Kama (Right Desires fulfilled) and (finally) Moksha (Liberation by discovering the deeper consciousness),