Chlordane transport in a sandy soil: effects of suspended soil material and pig slurry

In experiments in lysimeters of sandy soil chlordane was transported in water flows only when sorbed on suspended soil material. A chlordane 'concentration' was calculated by dividing this sorbed chlordane by the volume of the water sample in which the suspended matter was carried. In all but one lysimeter the first peak in this 'concentration' appeared in the drainage well ahead of the first peak in the concentration of bromide applied at the same time as the chlordane. Chlordane also persisted in the drainage for less time than bromide. The transport of chlordane was most closely associated with that of the largest category of suspended soil material (> 1.2 mu m), possibly because that category contained the most organic matter. It was not associated with the transport of colloidal matter for either of the two possible size limits applied to the latter (<0.22 mu m or <0.45 mu m). In the lysimeters to which pig slurry was applied the evidence that it enhanced the transport of chlordane was limited and equivocal; the chlordane was probably sorbed strongly by the soil's organic matter before the slurry was applied. The application of chlordane was 100 times greater than in normal agricultural practice and it was followed by a substantial volume of water. Nevertheless, only 0.00002% of it was transported from the lysimeters, and its 'concentration', calculated as above, never exceeded the EU limit of 0.1 mu gl(-1) for any one pesticide.