Passive scalars in turbulent flows

Passive scalar behavior is important in turbulent mixing, combustion, and p ollution and provides impetus for the study of turbulence itself. The conce ptual framework of the subject, strongly influenced by the Kolmogorov casca de phenomenology, is undergoing a drastic reinterpretation as empirical evi dence shows that local isotropy, both at the inertial and dissipation scale s, is violated. New results of the complex morphology of the scalar field a re reviewed, and they are related to the intermittency problem. Recent work on other aspects of passive scalar behavior--its spectrum, probability den sity function, flux, and variance--is also addressed.