biodisponibility of heavy metals depend on metal form and content in water, plant species and developmental stage of plant.

I assume that the heavy metals are not intruduced by the irrigation water but through other sources such as fertliser, manure etc?

If this is the case then the movement of the heavy metals out of the root zone should theoretically increase with an increase in the leaching fraction. It is not the water application method but the total amount of water that it is applied (from irrigation and rainfall) that is important.

However you need to realise that most heavy metals have low solubility

thank you so much indeed.

I mean that maybe the low water rate in drip irrigation let the heavy metal settle at the bottom of tube  (sedimentation) and not transfer to soil system, however, in furrow the direction concetion of heavy metal in irrigtaion water causes more transport to deeper depth or more uptake by plants?

Accumulation of any material in the dripper tube is a problem and will lead to clogging of the system.    

The important question to ask is if the heavy metals are disolved in the irrigation water or are they instead in the form of suspended solids that would be removed by appropriate filtering before entering the drip tube.

Drip irrigation is the minor irrigation system . consist pipe and tube. tubes can not be hold heavy material due to that might be blocking problems. containment water might be created choked drips and water released stoped.