Remediation of heavy metal contaminated groundwater originated from abandoned mine using lime and calcium carbonate.

Column and pilot scale experiments for a chemical treatment involving the use of coagulants to remediate heavy metal contaminated groundwater were performed. Granulated lime (Ca(OH)(2)) and calcium carbonate (CaCO(3)) were used as coagulants and contaminated groundwater obtained at an abandoned Fe-mine in Korea was used for the experiments. The main removal mechanism of heavy metals in the experiments was "sweep precipitation" by coagulation. Using granulated lime as a coagulant in the column experiment, more than 98% of As and Ni were removed from artificially contaminated water. When granulated calcium carbonate was used in the artificially contaminated water, the removal efficiencies of Ni and Zn were more than 97%, but As removal efficiency was lower than 50%. For the continuous column experiment with mixed lime and calcium carbonate at a 1:1 (v/v) ratio, almost all As was removed and more than 98 % of Ni was removed. For pilot scale experiments (acryl tank: 34 cm in length and 24 cm in diameter), the removal efficiencies of As and Cd were above 96% for 150l groundwater treatment and their accumulated removal capacities linearly maintained. This suggests that coagulants could treat more than 22 times greater groundwater volume compared with the volume of coagulants used.

A large and distinct skin impression on the cast of a sauropod dinosaur footprint from Early Cretaceous floodplain deposits, Korea.

The occurrence and features of skin impressions in a sauropod footprint, the largest (>50 cm in diameter) reported to date for this taxon, from the Lower Cretaceous Haman Formation (Albian) in Korea are described, and its preservation and paleoenvironmental implications are interpreted. The skin impression-bearing deposits are floodplain sediments formed by sheetflood processes. The large impression is preserved in silty mudstone with microbial lenses and wisps overlying a planar- to cross-laminated and fine-grained sandstone to siltstone bed. The paleoenvironment of the skin impression-bearing deposits is interpreted as a saline sandflat to mudflat where microbial mats can form around lakes or ponds under semi-arid paleoclimatic conditions with alternating wetting and drying intervals. These paleoenvironmental conditions would have permitted the distinct preservation of skin impressions in a dinosaur footprint. The observations here suggest that some sauropod dinosaurs in the Cretaceous had a well-developed polygonal skin texture covering nearly the whole of their foot pads, as seen in modern elephants, which would increase stability when walking on muddy and wet ground.

Soil washing of As-contaminated stream sediments in the vicinity of an abandoned mine in Korea.

A soil washing process was applied to remediate arsenic (As)-contaminated stream sediments around an abandoned mine in Goro, Korea. Laboratory scale soil washing experiments for As-contaminated stream sediments were performed under various washing conditions in order to maximize As removal efficiency. Stream sediments were taken from two sites (S1 and S5) along the main stream connected to an abandoned mine. Stream sediments at the two sites were divided into two groups (>or=0.35 and <0.35 mm in diameter), giving four types of sediments, which were thereupon used for soil washing experiments. The results of soil washing experiments involving various pH conditions suggested that As removal efficiency is very high in both strongly acidic and basic solutions (pH 1 and 13), regardless of sediment type. Removal efficiencies for fine sediments from S1 and S5 were >95% after 1 h of washing with 0.2 M citric acid (C(6)H(8)O(7)). When using 0.2 M citric acid mixed with 0.1 M potassium phosphate (KH(2)PO(4)), the As removal efficiency increased to 100%. When recycled washing solution was applied, As removal efficiency was maintained at a level greater than 70%, even after eight recycling events. This suggests that the recycling of washing solution could be successfully applied as a means of decreasing the cost of the washing process. Results from the experiments suggest that soil washing is a potentially useful process for the remediation of As-contaminated stream sediments around abandoned mines.