Reply to comments by Henry N. Pollack and David S. Chapman on “Spherical harmonic analysis of Earth’s conductive heat flow”     

V. M. Hamza  R. R. Cardoso  C. F. Ponte Neto 《International Journal of Earth Sciences》2008,97(2):233-239

Pollack and Chapman, hereafter referred to as P&C, argue that: (1) errors arising from lack of quality control in the IHFC database are not important and not properly documented, (2) resolution of spatial patterns in global heat flux distribution should not be represented by spherical harmonics and (3) heat flow in young oceanic crust and global heat loss are better represented by a contested 1-D cooling model than by the data. We disagree and provide additional information that may help clear up such misunderstandings. We also mention briefly the results of a new improved thermal model of the lithosphere that satisfactorily reproduces the main features identified in observational data sets of heat flow and ocean floor bathymetry. Thus, there is no reason to invoke the ad hoc hypothesis of large-scale hydrothermal circulation in the ocean crust.  相似文献   

Experimental assessment of a possible microbial priming effect in a humic boreal lake     

Irene Dorado-García  Jari Syväranta  Shawn P. Devlin  Juan Manuel Medina-Sánchez  Roger I. Jones 《Aquatic Sciences - Research Across Boundaries》2016,78(1):191-202

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Biomonitoring of Heavy Metals Using the Bivalve Molluscs in Sunderban Mangrove Wetland,Northeast Coast of Bay of Bengal (India): Possible Risks to Human Health   总被引：2，自引：0，他引：2  

Santosh Kumar Sarkar  Henrique Cabral  Mousumi Chatterjee  Ines Cardoso  Asok Kumar Bhattacharya  Kamala Kanta Satpathy  Mohammad Aftab Alam 《洁净——土壤、空气、水》2008,36(2):187-194

The suitability of using four bivalve molluscs (Sanguinolaria acuminata, Anadara granosa, Meretrix meretrix, and Pelecyora trigona) in biomonitoring of heavy metals (Cu, Pb, Cd, Zn, and Hg) collected from intertidal regions of the Sunderban mangrove wetland, northeastern part of the Bay of Bengal, were evaluated. Both speciesdependent variability and temporal variations were pronounced. A high degree of organ specificity was evident in the bivalves where gill and mantle exhibited higher metal accumulation due to ion exchange property of the mucous layer covering these organs while shells represent very poor accumulation. Elevated values of Zn and Cu reflect high potential for biomagnification through marine food chain. Metal concentrations in different body size groups of the bivalves do not follow uniform trend. Correlation coefficient between different metal couplings as tested statistically revealed significant coupling for Pb–Zn, Pb–Cu, Zn–Cu, and Hg–Cu. Concentrations of all the metals in specific organs (visceral mass, mantle and gill) of the bivalves exceeded the safe levels according to the international standards for metals compiled by Food and Agricultural Organization of the United Nations and would be of great risk for human consumption. It is concluded that the mussel and clam are suitable biomonitors to employ in programs designed to assess changes in metal pollution in the Sunderban mangrove wetland.  相似文献   

Principal component analysis (PCA) and mineral associations of litoraneous facies of continental shelf carbonates from northeastern Brazil     

Wanessa Sousa Marques  Alcides Nobrega Sial  Eldemar de Albuquerque Menor  Valderez Pinto Ferreira  George Satander Sá Freire  Enjolras de Albuquerque Medeiros Lima  Valdir do Amaral Vaz Manso 《Continental Shelf Research》2008

The distribution of mineral phases according to the provenance of carbonate and terrigenous facies of carbonate sediments from a large area of the continental shelf of northeast Brazil was investigated using a major element multivariate analysis approach. Heavy minerals such as ilmenite are restricted to the litoraneous facies of the continental shelf of the states of Paraíba and Pernambuco, and clay minerals are found in distal facies of the continental shelf of the State of Ceará. In the carbonate fraction, composed essentially by Mg-calcite and aragonite, there is co-variation between CaO/MgO and bathimetry in part of the studied continental shelf from depths between 15 and 20 m, apparently due to influence of the seawater temperature, degree of oxygenation and luminosity. The terrigenous facies are mainly composed of quartz, clay minerals, K-feldspars and micro-micaceous minerals, having Fe and Ti oxide and hydroxide minerals as major accessory phases. Major element behavior attests to the presence of arenaceous quartz-rich relict sediments in the 35, 60 and 80 m isobaths of the continental shelf of the state of Ceará which is here interpreted as a proxy of ancient coast lines during the Flandrian transgression.  相似文献   

Social networks and undocumented Mozambican migration to South Africa     

Ramos Cardoso Muanamoha  Brij Maharaj  Eleanor Preston-Whyte 《Geoforum》2010,41(6):885-896

This paper analyses the social networks which facilitate and sustain undocumented migration from Mozambique to South Africa. A key contention is that the migrant social networks are not limited to a spatially bounded area; transcend geography, location and territory; can be considered as spatial conveyors of social capital; and operate transnationally at three different locations: in the sending communities, on borders and in the destination areas. In the sending communities, interpersonal relationships are based on bonds of kinship, and friendship through which the migrants get moral and material support for the movement. At the borders migrants establish connections with border agents, guides, and conveyors who support them in entering South Africa and provide transportation to their preferred destinations. At the destination areas the newcomers have also counted on the bonds of kinship and friendship among former immigrants, who assist them on their arrival with accommodation and food as well as in the process of getting jobs and documentation. In South Africa undocumented migrants were subjected to high levels of xenophobia, exploitation and deportation, structural, sociopolitical forces against which social networks are largely ineffective. However, through the social networks the undocumented Mozambican labour migration to South Africa has become a self-sustained circular process that is difficult to control.  相似文献