You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Utilizing Eisenia andrei to assess the ecotoxicity of platinum mine tailings disposal facilities. South Africa is an important platinum mining country which results in environmental impacts due to the construction of tailing disposal facilities (TDFs). It is unclear what the effects of ageing are on the ecotoxicity of TDFs and whether it increases or decreases over time. The aim of this study was to determine the ecotoxicity of differently aged TDFs by investigating earthworm (Eisenia andrei) responses viz. growth, reproduction, neutral red retention times (NRRT) and tissue metal concentrations. Further, to evaluate the status of these in terms of a geoaccumulation index (I(geo)), pollution index and integrated pollution index. Results indicated that earthworms showed reduced reproductive success (hatchlings per cocoon) and decreased NRRT in all the sites. Juveniles per cocoon between all of the different treatment groups were; control (2.83 ± 0.54) > site 2 (20 years old; 1.83 ± 0.27) > sites 1 and 3 (40 years old; 1.06 ± 0.15 and 6 years old; 0.88 ± 0.39). This might be ascribed to the elevated levels of Cr (±200 to 1,166 μg g(-1)) and Ni (±100 to 316 μg g(-1)) in all of the sites. Earthworms did not bioaccumulate metals with bioconcentration factors for all the different treatments <0.01. Studies like these could be useful when establishing a ranking of TDFs in the future to provide legislative institutions with an indication of the environmental liabilities of platinum mines.
{"Chemical": ["platinum", "Cr", "Ni"]}