@article{fdi:010053070, title = {{M}ethylmercury in tailings ponds of {A}mazonian gold mines ({F}rench {G}uiana) : field observations and an experimental flocculation method for in situ remediation}, author = {{G}u{\'e}dron, {S}t{\'e}phane and {C}ossa, {D}. and {G}rimaldi, {M}ichel and {C}harlet, {L}.}, editor = {}, language = {{ENG}}, abstract = {{S}ites of monomethylmercury ({MMH}g) production in {A}mazonian regions have been identified in hydraulic reservoirs, lake sediments and wetlands, but tailings ponds have not yet received sufficient attention for this purpose. {T}his work evidenced high {MMH}g production within the water column and the interstitial water of two tailings ponds of {F}rench {G}uiana {A}u mines located; (i) in a small scale exploitation ({C}ombat) where {H}g was used for {A}u amalgamation, and (ii) in an industrial on-going {A}u mine ({Y}aoni) processing without {H}g. {T}he ({MMH}g)({D}) maximum (2.5 ng {L}-1) occurred in the oxic water column above the sediment-water interface ({SWI}) of the most recent tailings pond ({C}ombat), where the substrate was fresh, the redox transition was sharp and the pool of total {H}g was large. {I}n the {Y}aoni pond, the ({MMH}g)({D}) maximum concentration (1.4 ng {L}-1) was located at the {SWI} where suboxic conditions prevailed. {U}sing the ({MMH}g)({D}) concentration as a proxy for {H}g methylation rates, the present results show that {H}g methylation may occur in various redox conditions in tailings ponds, and are favored in areas where the organic matter regeneration is more active. {A} 3-month long laboratory experiment was performed in oxic and anoxic boxes filled with high turbidity waters from the {C}ombat {A}u mine to simulate tailings ponds. {S}laked lime was added in an experimental set (2 mg {L}-1)and appeared to be very efficient for the reduction of suspended particulate matter ({SPM}) to environmentally acceptable concentrations. {H}owever, at the end of the experiment, large ({MMH}g)({D}) concentrations were monitored under treated anoxic conditions with the ({MMH}g)({D}) maximum located at the {SWI} above the {F}e-reducing zones. {N}o ({MMH}g)({D}) was detected in oxic experiments. {T}he use of slaked lime for {SPM} decantation appears to be an efficient and non-onerous process for {A}u miners to avoid {H}g methylation in tailings ponds when it is combined with rapid drainage of the mine waters. {A} subsequent human intervention is however necessary for the recovery of soil structure through the cover of dried ponds with organic rich materials and reforestation to avoid the stagnation of rain waters and the occurrence of anoxia.}, keywords = {{GUYANE} {FRANCAISE} ; {AMAZONIE}}, booktitle = {}, journal = {{A}pplied {G}eochemistry}, volume = {26}, numero = {2}, pages = {222--229}, ISSN = {0883-2927}, year = {2011}, DOI = {10.1016/j.apgeochem.2010.11.022}, URL = {https://www.documentation.ird.fr/hor/fdi:010053070}, }