Effects of acid mine drainage on dissolved inorganic carbon and stable carbon isotopes in receiving streams

@article{citeulike:2735321, abstract = {Dissolved inorganic carbon (DIC) constitutes a significant fraction of a stream's carbon budget, yet the role of acid mine drainage (AMD) in DIC dynamics in receiving streams remains poorly understood. The objective of this study was to evaluate spatial and temporal effects of AMD and its chemical evolution on DIC and stable isotope ratio of DIC ([delta]13CDIC) in receiving streams. We examined spatial and seasonal variations in physical and chemical parameters, DIC, and [delta]13CDIC in a stream receiving AMD. In addition, we mixed different proportions of AMD and tap water in a laboratory experiment to investigate AMD dilution and variable bicarbonate concentrations to simulate downstream and seasonal hydrologic conditions in the stream. Field and laboratory samples showed variable pH, overall decreases in Fe2+, alkalinity, and DIC, and variable increase in [delta]13CDIC. We attribute the decrease in alkalinity, DIC loss, and enrichment of 13C of DIC in stream water to protons produced from oxidation of Fe2+ followed by Fe3+ hydrolysis and precipitation of Fe(OH)3(s). The extent of DIC decrease and 13C enrichment of DIC was related to the amount of dehydrated by protons. The laboratory experiment showed that lower 13C enrichment occurred in unmixed AMD (2.7[per mille sign]) when the amount of protons produced was in excess of or in tap water (3.2[per mille sign]) where no protons were produced from Fe3+ hydrolysis for dehydration. The 13C enrichment increased and was highest for AMD-tap water mixture (8.0[per mille sign]) where Fe2+ was proportional to concentration. Thus, the variable downstream and seasonal 13C enrichment in stream water was due in part to: (1) variations in the volume of stream water initially mixed with AMD and (2) to input from groundwater and seepage in the downstream direction. Protons produced during the chemical evolution of AMD caused seasonal losses of 50 to >98\% of stream water DIC. This loss of DIC in AMD impacted streams may have implications for CO2 transfer to the atmosphere and watershed DIC export.}, author = {Fonyuy, Ernest W. and Atekwana, Eliot A. }, citeulike-article-id = {2735321}, doi = {http://dx.doi.org/10.1016/j.apgeochem.2007.12.003}, journal = {Applied Geochemistry}, keywords = {13c, acid\_mine\_drainage, alkalinity, anthropogenic, carbon, co2, dic, dic13, longitudinal, streams}, month = {April}, number = {4}, pages = {743--764}, posted-at = {2008-04-29 21:02:44}, priority = {2}, title = {Effects of acid mine drainage on dissolved inorganic carbon and stable carbon isotopes in receiving streams}, url = {http://dx.doi.org/10.1016/j.apgeochem.2007.12.003}, volume = {23}, year = {2008} }

TY - JOUR ID - citeulike:2735321 L3 - citeulike-article-id:2735321 TI - Effects of acid mine drainage on dissolved inorganic carbon and stable carbon isotopes in receiving streams JF - Applied Geochemistry VL - 23 IS - 4 SP - 743 EP - 764 N2 - Dissolved inorganic carbon (DIC) constitutes a significant fraction of a stream's carbon budget, yet the role of acid mine drainage (AMD) in DIC dynamics in receiving streams remains poorly understood. The objective of this study was to evaluate spatial and temporal effects of AMD and its chemical evolution on DIC and stable isotope ratio of DIC ([delta]13CDIC) in receiving streams. We examined spatial and seasonal variations in physical and chemical parameters, DIC, and [delta]13CDIC in a stream receiving AMD. In addition, we mixed different proportions of AMD and tap water in a laboratory experiment to investigate AMD dilution and variable bicarbonate concentrations to simulate downstream and seasonal hydrologic conditions in the stream. Field and laboratory samples showed variable pH, overall decreases in Fe2+, alkalinity, and DIC, and variable increase in [delta]13CDIC. We attribute the decrease in alkalinity, DIC loss, and enrichment of 13C of DIC in stream water to protons produced from oxidation of Fe2+ followed by Fe3+ hydrolysis and precipitation of Fe(OH)3(s). The extent of DIC decrease and 13C enrichment of DIC was related to the amount of dehydrated by protons. The laboratory experiment showed that lower 13C enrichment occurred in unmixed AMD (2.7[per mille sign]) when the amount of protons produced was in excess of or in tap water (3.2[per mille sign]) where no protons were produced from Fe3+ hydrolysis for dehydration. The 13C enrichment increased and was highest for AMD-tap water mixture (8.0[per mille sign]) where Fe2+ was proportional to concentration. Thus, the variable downstream and seasonal 13C enrichment in stream water was due in part to: (1) variations in the volume of stream water initially mixed with AMD and (2) to input from groundwater and seepage in the downstream direction. Protons produced during the chemical evolution of AMD caused seasonal losses of 50 to >98% of stream water DIC. This loss of DIC in AMD impacted streams may have implications for CO2 transfer to the atmosphere and watershed DIC export. KW - 13c KW - acid_mine_drainage KW - alkalinity KW - anthropogenic KW - carbon KW - co2 KW - dic KW - dic13 KW - longitudinal KW - streams AU - Fonyuy, Ernest AU - Atekwana, Eliot PY - 2008/04// UR - http://dx.doi.org/10.1016/j.apgeochem.2007.12.003 ER -