Monitoring of river water for free cyanide pollution from mining activity in Papua New Guinea and attenuation of cyanide by biochar Ian Sawaraba & B. K. Rajashekhar Rao Received: 18 May 2014 /Accepted: 19 November 2014 /Published online: 3 December 2014 # Springer International Publishing Switzerland 2014 Abstract Cyanide (CN) pollution was reported in the downstream areas of Watut and Markham Rivers due to effluent discharges from gold mining and processing activities of Hidden Valley mines in Morobe province of Papua New Guinea. We moni- tored free cyanide levels in Watut and Markham River waters randomly three times in years for 2 years (2012 and 2013). Besides, a short-term static laboratory study was conducted to evaluate the po- tential of river sediment to attenuate externally added cyanide, with and without the presence of biochar material. Results indicated that the free cyanide con- tent ranged between 0.17 and 1.32 μgL -1 in the river waters. The free cyanide content were found to be significantly ( p <0.05) greater in June (0.87 μgL -1 ) and May (0.77 μgL -1 ) months of 2012 and 2013, respectively, than the rest of the months. However, free cyanide levels in all four monitoring sites across three sampling intervals were lower than 0.20 mg L -1 which is the maximum contaminant level (MCL) permitted according to US Environmental Protection Agency. Under labora- tory conditions, the biochar-impregnated sediment showed ∼3 times more attenuation capacity for cya- nide than non-amended sediment, thus indicating possibility of using biochar to cleanse cyanide from spills or other sources of pollution. Keywords Biochar . Free cyanide . Monitoring . Mining . Pollution Introduction Cyanide as sodium cyanide is used in mining industries to extract gold and silver from ores, particularly in low- grade ores or ores that cannot be readily treated through simple physical processes such as gravity seperation. In a typical metal mining operation, tailings consist of crushed rock and ore, after most of the target metals have been removed, and the tailings are treated before discharged into water bodies (Bell and Donelly 2006). Mine tailings which are cyanide-laced are toxic and, if not contained and properly treated, are harmful to the environment. Furthermore, problems originate from the transportation, handling, usage, and disposal of cyanide chemical. Cyanide is toxic to humans and to animal species because it binds to key iron containing enzymes required for cells to use oxygen (Hill and Henry 1996). Besides being a fast-acting acute poison, cyanide causes chronic poisoning in humans and animal species. Other problems with cyanide include loss of potable water, extinction of some fish species in the contaminated rivers, water birds and carnivorous animals dying after eating contaminated fish, surface and groundwater re- sources of communities along rivers becoming contam- inated with cyanide, and socioeconomic problems for communities along rivers due to temporary or longer- term loss of livelihood (Eisler and Weimeyer 2004). Negative impacts of tailing disposal on the environment Environ Monit Assess (2015) 187:4181 DOI 10.1007/s10661-014-4181-z I. Sawaraba : B. K. R. Rao (*) Department of Agriculture, PNG University of Technology, Private Mail Bag, Lae 411 Morobe, Papua New Guinea e-mail: rsraobk@rediffmail.com