Heavy metal accumulation in the surficial sediments along southwest coast of India     

P. Udayakumar  J. Jean Jose  K. Anoop Krishnan  C. S. Ratheesh Kumar  M. N. Manju  P. M. Salas 《Environmental Earth Sciences》2014,72(6):1887-1900

Concentration and distribution of heavy metals (Cd, Cr, Cu, Hg, Ni, Pb and Zn) in surface sediments collected from five stations located along the southwest coast of India were investigated seasonally to assess whether there is insidious buildup of heavy metals. Spatial variation was in accordance with textural characteristics and organic matter content. The concentration of the metals in sediments of the study area followed the order: Zn > Cr > Ni > Cu > Pb > Cd > Hg. The use of geochemical tools and sediment quality guidelines to account for the magnitude of heavy metal contamination revealed high contamination in monsoon and impoverishment during post-monsoon. Estimated total metal concentrations in the present investigation were comparable with other studies; however, concentrations of Ni and Zn were higher than that of other coastal regions. Concentrations of metals in sediment largely exceed NOAA effects range:low (e.g., Cu, Cr, Hg) or effects range:median (e.g., Ni) values. This means that adverse effects for benthic organisms are highly probable.  相似文献   

Analysis of the Tsunami of December 26, 2004, on the Kerala Coast of India—Part III: Inundation and Initial Withdrawal     

N. P. Kurian  K. Rajith  B. T. Murali Krishnan  N. Nirupama  T. S. Murty 《Marine Geodesy》2013,36(4):277-281

During the Indian Ocean tsunami of December 26, 2004, specific observations were made by our survey team about the arrival times of several tsunami waves, their amplitudes, maximum extent of horizontal inundation on land and initial withdrawal of the ocean. Here the observations on the horizontal inundation and initial withdrawal are presented and briefly discussed.  相似文献   

Organic carbon and iron modulate nitrification rates in mangrove swamps of Goa, south west coast of India     

K.P. Krishnan  P.A. Loka Bharathi   《Estuarine, Coastal and Shelf Science》2009,84(3):419

Nitrification, fuelled by ammonium is the pivotal oxidative pathway to nitrogen cycling. In spite of its ecological significance, the factors regulating nitrification rates in the benthic realm remain poorly understood. The present study therefore examines some of the factors like ammonium, nitrite, nitrate, organic carbon, iron and manganese on down-core variability in benthic nitrification rates in two different mangrove ecosystems, one under the influence of ferromanganese ore mining (experiment) and the other relatively undisturbed (control). We hypothesize that besides organic carbon, iron could also influence the rate of nitrification. The study also contrasts the distributive pattern of autotrophic and heterotrophic nitrifiers in the two regions. The concentration of iron at the control site ranged from 1.1% to 15.1% while at the experimental site it ranged from 2.9% to 46%. The levels of organic carbon at control and experimental sites ranged from 0.02% to 6.9% and 0.1% to 6.5%, respectively. The nitrification rates at the control and experimental sites are comparable and ranged from 3.2 ± 1.2 to 18.4 ± 1.9 ng at-N g(sediment)⁻¹ h⁻¹ and 2.7 ± 1.5 to 18.2 ± 0.6 ng at-N g(sediment)⁻¹ h⁻¹, respectively. While the abundance of heterotrophic nitrifiers at both the sites ranged from 10^2–3 cells g⁻¹ sediment, the autotrophic nitrifiers at the experimental site was higher by an order at 10³ cells g⁻¹ sediment reflecting the relatively higher refractile nature of organic carbon at the experimental site (Straus and Lamberti, 2000). Though organic carbon and nitrification rates are similar in both the sites, the underlying mechanisms governing the processes could be different. Our studies suggest that at the control site, heterotrophic nitrifiers govern nitrification rates (r = 0.28, p < 0.05, n = 64) using organic carbon (r = 0.32, p < 0.01, n = 64). At the experimental site, nitrification was governed more by autotrophic nitrifiers (r = 0.43, p < 0.001, n = 64) at the expense of iron (r = 0.47, p < 0.001, n = 64). Therefore at the experimental site with higher load of iron, autotrophic nitrification could be more important. It is therefore inferred that both the quality of organic carbon and quantity of iron govern nitrification rates in these mangrove swamps.  相似文献