El medio ambiente en la minería

El MEDIO AMBIENTE EN LA MINERIA 118 Figure 6 shows that the arsenic conten! oC a bottom..<Jwelling mollusc is approaching the background leve1. This is highly encouraging and indicates that the upper sedimentary layer is gradually bécoming cIeaner. ARSENIC CONTENT (mg/kg dry W4i>ighU 80 60 40 o~------~----------------~----------------~ 19[«) 1995 19ge *CAU8HT AT A DISTANCE cw: 2.5 KI1 1M AH EASTE:.RL'r' DIRECTlOO Figure 6: Arsenic content in molluscs (Lymnaea)* Figure 7 depiets the results of arsenic-content fmdings in animal plankton in the Gulf of Bothnia. An investigation in the late 1970s indicated elevated contents in the greater part of this ocean basin, while a corresponding inves– tigatíon in 1987 indicated that tbis ¡nereasehad been reduced and affected on1y a smaller part of the ocean basin. at the same time as the highest contaIninant contents had been reduced.