Abstract
Concentrations of copper, arsenic and cadmium in sediments and soils deposited on the flood plain of the upper Clark Fork River drainage were determined to be one to two orders of magnitude greater than in soils from typical noncontaminated systems. Aerial deposition of metal particulates during the period of smelting activities (1884-1980) has contributed approximately 2% of the excess copper, 9% of the excess arsenic, and 30% of the excess cadmium in the riparian zone of a ranch on the flood plain at Deer Lodge; the remaining 98% excess copper, 91% excess arsenic and 70% excess cadmium in the riparian zone was deposited by the river transporting contaminated sediments originating from upstream mining and smelting activities. Metal concentrations in contaminated sediments did not decrease with distance downstream from the source areas at Anaconda and Butte.
Toxic metal concentrations of soil were highest (x: 1630 ug Cu/g; 176 ug As/g, 5 ug Cd/g) in the riparian shrub/grass zone immediately adjacent to the river channel where flooding occurs most frequently. The riparian zone also contains contaminated sediment deposits termed "slickens" where available metals were suspected to be preventing reestablishment of vegetative cover. Soil microbial activity was depressed 82% in these slickens in contrast to adjacent soils. These nonvegetated slickens comprised 0.6% of the acreage of the ranch studied. Metal concentrations (x: 184 ug Cu/g, 49 ug As/g, 2.2 ug Cd/g) in the meadow zone which was elevated several feet above the riparian zone and subject to less frequent flooding, were less than those of the riparian zone but still greater than in soils of the bench zone located above the flood plain.
Metal concentrations in forage grass (Agrostis alba L.) from the flood plain were 2X to more than lOX the expected value for uncontaminated areas. However, only Cu (10.4 ug/g) in grass from the riparian zone was significantly higher than the concentration (7.2 ug/g) measured in grass from a check plot subjected to just aerial deposition.
Schematic maps of slickens and metal concentrations in soil and grass were prepared. Cu content of soil could be used to estimate as and Cd concentrations of soil.
Start Date
19-4-1985 12:00 AM
End Date
19-4-1985 12:00 AM
Document Type
Presentation
Heavy Metals in the Flood Plain Deposits Along the Upper Clark Fork River
Concentrations of copper, arsenic and cadmium in sediments and soils deposited on the flood plain of the upper Clark Fork River drainage were determined to be one to two orders of magnitude greater than in soils from typical noncontaminated systems. Aerial deposition of metal particulates during the period of smelting activities (1884-1980) has contributed approximately 2% of the excess copper, 9% of the excess arsenic, and 30% of the excess cadmium in the riparian zone of a ranch on the flood plain at Deer Lodge; the remaining 98% excess copper, 91% excess arsenic and 70% excess cadmium in the riparian zone was deposited by the river transporting contaminated sediments originating from upstream mining and smelting activities. Metal concentrations in contaminated sediments did not decrease with distance downstream from the source areas at Anaconda and Butte.
Toxic metal concentrations of soil were highest (x: 1630 ug Cu/g; 176 ug As/g, 5 ug Cd/g) in the riparian shrub/grass zone immediately adjacent to the river channel where flooding occurs most frequently. The riparian zone also contains contaminated sediment deposits termed "slickens" where available metals were suspected to be preventing reestablishment of vegetative cover. Soil microbial activity was depressed 82% in these slickens in contrast to adjacent soils. These nonvegetated slickens comprised 0.6% of the acreage of the ranch studied. Metal concentrations (x: 184 ug Cu/g, 49 ug As/g, 2.2 ug Cd/g) in the meadow zone which was elevated several feet above the riparian zone and subject to less frequent flooding, were less than those of the riparian zone but still greater than in soils of the bench zone located above the flood plain.
Metal concentrations in forage grass (Agrostis alba L.) from the flood plain were 2X to more than lOX the expected value for uncontaminated areas. However, only Cu (10.4 ug/g) in grass from the riparian zone was significantly higher than the concentration (7.2 ug/g) measured in grass from a check plot subjected to just aerial deposition.
Schematic maps of slickens and metal concentrations in soil and grass were prepared. Cu content of soil could be used to estimate as and Cd concentrations of soil.