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The sources of dissolved manganese to Calico Creek, North Carolina: A reply
Estuarine and Coastal Marine Science (1978) 7, 579-580
The Sources of Dissolved Manganese to Calico Creek, North Carolina: A Reply
James G. Sanders Sk&&away Institute of Oceanography, P.O. Box 13687, Savannah, Georgia 31406, U.S.A. Received27 June 1978
Lyons & Gaudette (1978) suggest that the pore water manganese concentrations presented in Sanders (1978) are too low, since other studies report concentrations 2.3 to 50 times higher than those reported for Calico Creek (Calvert & Price, 1972; Holdren et al., 1975; Matisoff et al., 1975; Trefry, 1977). The cause for the lowered pore water concentrations, in their opinion, is improper sample handling. Although not fully outlined due to space restrictions, the samples discussed were handled as carefully as possible. Preliminary pore water samples were processed under N, atmosphere until acidified. However, experiments performed to assessthe rapidity of Mns+ oxidation in pore waters, and simultaneous processing of samples under both Ns and air showed that negligible Mns + is oxidized during the short air exposure. Samples processed under N, atmosphere had a maximum Mn a+ concentration of 280 pg 1-l in contrast to 290 pg 1-l in samples processed in air. Trefry (personal communication) has performed similar studies during his investigations in the Gulf of Mexico, and his findings are in agreement. It appears that even under conditions favorable to Mn2+ oxidation (the presence of O,, numerous particle surfaces, high pH), the oxidation progresses rather slowly. Graham et al. (1976) found similar oxidation rates, and suggested that the oxidation half-life was approximately 2 days. The low pore water manganese concentrations in Calico Creek sediments are not unusual since Calico Creek also has a low total manganese concentration. The concentration of dissolved manganese in sediments is directly proportional to the total manganese concentration. Areas with high total manganese concentrations can support higher dissolved manganese concentrations. Total manganese concentrations in Calico Creek average 64 pg g-1 (R. T. Barber, personal communication), values reported in the literature range between 3 and 30 times the Calico Creek average (Li et al., 1969; Holdren et al., 1975 ; Thomson et al., 1975; Windom, 1975; Serne, 1977; Trefry, 1977). A very rough calculation of the distribution of manganese in pore waters shows that from 0.2 to 3% of the total manganese is found in the dissolved form (Li et al., 1969; Calvert & Price, 1972; Holdren et al., 1975; Serne, 1977; Trefry, 1977); in Calico Creek, approximately 0*50/Ois dissolved manganese. The lower pore water concentrations in Calico Creek may also be due to intensive reworking of the sediment by physical or biological processes caused by the extreme shallowness (less than I m) of the creek. In conclusion, Calico Creek has lower dissolved manganese concentrations in the sediment pore waters than other estuarine and deep-sea sites due largely to low total manganese 579
580
J. G. Sanders
concentrations and not to improper sample handling. The proper handling of samples for trace analysis is extremely important, and I join with Lyons & Gaudette in suggesting that intercalibration studies involving trace species in pore waters would be valuable.
References Calvert, S. E. & Price, N. B. 1972 Diffusion and reaction profiles of dissolved manganese in the pore waters of marine sediments. Earth and Planetary Science Letters 16,245~249. Graham, W. F., Bender, M. L. & Klinkhammer, G. P. 1976 Manganese in Narragansett Bay. Limnology
and Oceanography II, 665-673. Holdren, G. R., Bricker, 0. P. & Matisoff, G. 1975 A model for the control of dissolved manganese in the interstitial waters of Chesapeake Bay. In Marine Chemiktry in the Coastal Environment (Church, T. M., ed.). American Chemical Society. pp. 364-381. Li, Y., Bischoff, J. & Mathieu, G. 1969 The migration of manganese in the Arctic Basin sediment.
Earth and Planetary Science Letters 7, 265-270. Lyons, W, B. & Gaudette, H. E. 1978 Comment. Estuarine and Coastal Marine Science 7, 577-578. Matisoff, G., Bricker, 0. P., Holdren, G. R. & Kaerk, P. 1975 Spatial and temporal variations in the interstitial water chemistry of Chesapeake Bay sediments. In Marine Chemistv in the Coastal Enuironment (Church, T. M., ed.). American Chemical Society. pp. 343-363. Sanders, J. G. 1978 The sources of dissolved manganese to Calico Creek, North Carolina. Estuarine
and Coastal Marine Science 6,23x-238. Seme, R. J. 1977 Geochemical distribution of selected trace metals in San Francisco Bay sediments. In Biological Implications of Metals in the Environment (Drucker, H. & Wildung, R. E., eds). Technical Information Center, Energy Research and Development Administration CONF-730929. pp. 280-296. Thomson, J., Tumkian, K. K. & McCat%ey, R. J. 1975 The accumulation of metals in and release from sediments of Long Island Sound. In Estwrine Research, Vol. I (Cronin, L. E., ed.). Academic Press, New York. pp. 28-44. Trefry, J. H. 1977 The transport of heavy metals by the Mississippi River and their fate in the Gulf of Mexico. PhD thesis, Texas A & M University. Windom, H. L. 1975 Heavy metal fluxes through salt-marsh estuaries. In Estuorine Research, Vol. I (Cronin, L. E., ed.). Academic Press, New York. pp. 137-152.
The Sources of Dissolved Manganese to Calico Creek, North Carolina: A Reply
James G. Sanders Sk&&away Institute of Oceanography, P.O. Box 13687, Savannah, Georgia 31406, U.S.A. Received27 June 1978
Lyons & Gaudette (1978) suggest that the pore water manganese concentrations presented in Sanders (1978) are too low, since other studies report concentrations 2.3 to 50 times higher than those reported for Calico Creek (Calvert & Price, 1972; Holdren et al., 1975; Matisoff et al., 1975; Trefry, 1977). The cause for the lowered pore water concentrations, in their opinion, is improper sample handling. Although not fully outlined due to space restrictions, the samples discussed were handled as carefully as possible. Preliminary pore water samples were processed under N, atmosphere until acidified. However, experiments performed to assessthe rapidity of Mns+ oxidation in pore waters, and simultaneous processing of samples under both Ns and air showed that negligible Mns + is oxidized during the short air exposure. Samples processed under N, atmosphere had a maximum Mn a+ concentration of 280 pg 1-l in contrast to 290 pg 1-l in samples processed in air. Trefry (personal communication) has performed similar studies during his investigations in the Gulf of Mexico, and his findings are in agreement. It appears that even under conditions favorable to Mn2+ oxidation (the presence of O,, numerous particle surfaces, high pH), the oxidation progresses rather slowly. Graham et al. (1976) found similar oxidation rates, and suggested that the oxidation half-life was approximately 2 days. The low pore water manganese concentrations in Calico Creek sediments are not unusual since Calico Creek also has a low total manganese concentration. The concentration of dissolved manganese in sediments is directly proportional to the total manganese concentration. Areas with high total manganese concentrations can support higher dissolved manganese concentrations. Total manganese concentrations in Calico Creek average 64 pg g-1 (R. T. Barber, personal communication), values reported in the literature range between 3 and 30 times the Calico Creek average (Li et al., 1969; Holdren et al., 1975 ; Thomson et al., 1975; Windom, 1975; Serne, 1977; Trefry, 1977). A very rough calculation of the distribution of manganese in pore waters shows that from 0.2 to 3% of the total manganese is found in the dissolved form (Li et al., 1969; Calvert & Price, 1972; Holdren et al., 1975; Serne, 1977; Trefry, 1977); in Calico Creek, approximately 0*50/Ois dissolved manganese. The lower pore water concentrations in Calico Creek may also be due to intensive reworking of the sediment by physical or biological processes caused by the extreme shallowness (less than I m) of the creek. In conclusion, Calico Creek has lower dissolved manganese concentrations in the sediment pore waters than other estuarine and deep-sea sites due largely to low total manganese 579
580
J. G. Sanders
concentrations and not to improper sample handling. The proper handling of samples for trace analysis is extremely important, and I join with Lyons & Gaudette in suggesting that intercalibration studies involving trace species in pore waters would be valuable.
References Calvert, S. E. & Price, N. B. 1972 Diffusion and reaction profiles of dissolved manganese in the pore waters of marine sediments. Earth and Planetary Science Letters 16,245~249. Graham, W. F., Bender, M. L. & Klinkhammer, G. P. 1976 Manganese in Narragansett Bay. Limnology
and Oceanography II, 665-673. Holdren, G. R., Bricker, 0. P. & Matisoff, G. 1975 A model for the control of dissolved manganese in the interstitial waters of Chesapeake Bay. In Marine Chemiktry in the Coastal Environment (Church, T. M., ed.). American Chemical Society. pp. 364-381. Li, Y., Bischoff, J. & Mathieu, G. 1969 The migration of manganese in the Arctic Basin sediment.
Earth and Planetary Science Letters 7, 265-270. Lyons, W, B. & Gaudette, H. E. 1978 Comment. Estuarine and Coastal Marine Science 7, 577-578. Matisoff, G., Bricker, 0. P., Holdren, G. R. & Kaerk, P. 1975 Spatial and temporal variations in the interstitial water chemistry of Chesapeake Bay sediments. In Marine Chemistv in the Coastal Enuironment (Church, T. M., ed.). American Chemical Society. pp. 343-363. Sanders, J. G. 1978 The sources of dissolved manganese to Calico Creek, North Carolina. Estuarine
and Coastal Marine Science 6,23x-238. Seme, R. J. 1977 Geochemical distribution of selected trace metals in San Francisco Bay sediments. In Biological Implications of Metals in the Environment (Drucker, H. & Wildung, R. E., eds). Technical Information Center, Energy Research and Development Administration CONF-730929. pp. 280-296. Thomson, J., Tumkian, K. K. & McCat%ey, R. J. 1975 The accumulation of metals in and release from sediments of Long Island Sound. In Estwrine Research, Vol. I (Cronin, L. E., ed.). Academic Press, New York. pp. 28-44. Trefry, J. H. 1977 The transport of heavy metals by the Mississippi River and their fate in the Gulf of Mexico. PhD thesis, Texas A & M University. Windom, H. L. 1975 Heavy metal fluxes through salt-marsh estuaries. In Estuorine Research, Vol. I (Cronin, L. E., ed.). Academic Press, New York. pp. 137-152.