394 Influence of Mines upon Land and Livestock 



General Conclusions. 



1 . There is an area of about 3000 acres within the sphere of influence 

 of mine refuse in North Cardiganshire. 



2. The unproductiveness of the affected land is due to the simul- 

 taneous influences of a number of circumstances, e.g. 



(a) The presence in the soil of toxic substances, mainly lead and 

 zinc, but in some cases small quantities of copper also. In the neighbour- 

 hood of a few mines contamination by iron pyrites and marcasite may 

 be contributory causes. 



(6) Unfavourable changes in the mechanical composition of the 

 soil leading to deterioration of its physical properties, e.g. capacity to 

 retain water. 



3. The deleterious effects are much more pronounced upon some 

 crops than others. Leguminous plants appear to be the most susceptible 

 to the injurious effects. 



4. Lead and zinc are carried on to the soil in the form of galena and 

 blende respectively. These sulphides are soon acted upon in the soil and 

 converted into other compounds of lead and zinc. It appears probable 

 that the lead is, in some measure, retained by the huniic orx)ther colloidal 

 substances of the soil. 



5. Lead is absorbed by and enters into the composition of the plant, 

 but only in very minute quantities. The poisoning of animals is due 

 more to the lead deposited on the exterior than to that contained 

 within the plant. 



6. The application of sodium silicate to the soil tends to mitigate 

 the undesirable influences of mine refuse upon plant growth. But the 

 most effective remedial measure is the apphcation of a heavy dressing 

 of lime. The amount of lime applied should be considerably greater 

 than the "lime requirement" as determined by the absorption of lime 

 from calcium bicarbonate solution. 



7. Ajiart from liming, it is by preventive rather than remedial 

 measures that the farmer's losses with both land and livestock may best 

 be minimised. These measures should involve 



(«) careful management at active mines to reduce as far as po.ssibie 

 the amount of injurious ingredients allowed to flow into rivers; 



(b) guarding against pollution from disused levels; 



(c) protection of mine slime and sand heaps at both active and dis- 

 used mines so as to prevent the material from being washed into the 

 water courses; 



