Optical trapping is a new tool for the manipulation and deposition of single wall carbon nanotube (SWNT) bundles. We present a study on optical trapping and manipulation of SWNT bundles in different environments, aimed at understanding the trapping mechanism. SWNTs are dispersed in water or organic solvents, and a wide range of both ionic and non-ionic surfactants, with different chain lengths, is used. We demonstrate that the surfactant plays a key role in optical trapping, strongly affecting the trapping force. Finally we discuss the calculation of radiation force for quasi-one-dimensional (1D) nanoparticles by means of field expansion in the framework of the T-matrix approach.