Metal/metalloid and phosphorus characteristics in porewater associated with manganese geochemistry: A case study in the Jiulong River Estuary, China.

Sediment porewater can be an important source of contaminants in the overlying water, but the mechanisms of metal(loid) and phosphorus (P) remobilization remain to be investigated. In this study, high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) samplers were used to determine the porewater dissolved iron (Fe), manganese (Mn), cobalt (Co), chromium (Cr), vanadium (V), selenium (Se), arsenic (As), P and DGT-Labile S in coastal sediments in the Jiulong River Estuary (JRE), China. The results showed that high concentrations of dissolved Mn, Se and P were present in the overlying water, indicating potential water pollution with excessive amounts of Mn, Se and P. The dissolved Mn concentrations in the porewater were higher than the dissolved Fe concentrations, especially at submerged sites, demonstrating that Mn(III/IV) reduction is the dominant diagenetic pathway for organic carbon (OC) degradation, which directly affects Fe cycling by the competitive inhibition of Fe(III) reduction and Fe(II) reoxidation. Dissolved Co, Cr, V, Se, As and P show significant positive correlations with Mn but nearly no correlations with Fe, suggesting that the mobility of these metal(loid)s and P is associated with Mn but not Fe cycling in this region. In addition, the coelevated concentrations of the metal(loid)s, P and Mn at the submerged sites are attributed to the strengthened Mn reduction coupled with OC degradation fueled by hypoxia. The higher positive diffusion fluxes of Mn, Se and P were consistent with the excess Mn, Se and P concentrations in the overlying water, together with the approximately positive fluxes of the other metal(loid)s, indicating that sediment Mn(III/IV) reduction and concomitant metal(loid) and P remobilization might be vital pathways for metal(loid) and P migration to the overlying water

Metal/metalloid and phosphorus characteristics in porewater associated with manganese geochemistry: A case study in the Jiulong River Estuary, China

Abstract(#br)Sediment porewater can be an important source of contaminants in the overlying water, but the mechanisms of metal(loid) and phosphorus (P) remobilization remain to be investigated. In this study, high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) samplers were used to determine the porewater dissolved iron (Fe), manganese (Mn), cobalt (Co), chromium (Cr), vanadium (V), selenium (Se), arsenic (As), P and DGT-Labile S in coastal sediments in the Jiulong River Estuary (JRE), China. The results showed that high concentrations of dissolved Mn, Se and P were present in the overlying water, indicating potential water pollution with excessive amounts of Mn, Se and P. The dissolved Mn concentrations in the porewater were higher than the dissolved Fe concentrations, especially at submerged sites, demonstrating that Mn(III/IV) reduction is the dominant diagenetic pathway for organic carbon (OC) degradation, which directly affects Fe cycling by the competitive inhibition of Fe(III) reduction and Fe(II) reoxidation. Dissolved Co, Cr, V, Se, As and P show significant positive correlations with Mn but nearly no correlations with Fe, suggesting that the mobility of these metal(loid)s and P is associated with Mn but not Fe cycling in this region. In addition, the coelevated concentrations of the metal(loid)s, P and Mn at the submerged sites are attributed to the strengthened Mn reduction coupled with OC degradation fueled by hypoxia. The higher positive diffusion fluxes of Mn, Se and P were consistent with the excess Mn, Se and P concentrations in the overlying water, together with the approximately positive fluxes of the other metal(loid)s, indicating that sediment Mn(III/IV) reduction and concomitant metal(loid) and P remobilization might be vital pathways for metal(loid) and P migration to the overlying water

Sustainable Land Urbanization and Ecological Carrying Capacity: A Spatially Explicit Perspective

Rapid urbanization has become a common occurrence all over the world, particularly in developing countries, and has thus resulted in various eco-environmental problems. In China, urban land has expanded at an unprecedented rate in the past several decades, and sustainable land urbanization has become an important issue in promoting sustainable development. Hence, scholars have proposed ecological carrying capacity (ECC) as a solution to balance socio-economic development and the ecosystems for achieving sustainable development. In the current work, we explored the spatial influence of ECC on land urbanization and its driving mechanism, using the Wuhan agglomeration as a case study. In the first step, we calculated the ECC at the county level using the ecological footprint method. Then, we applied a combination of kernel density and the “densi-graph method” on the basis of points of interest, in order to identify urbanized areas and to measure land urbanization rates. Finally, we devised spatial models with ECC-based spatial weight matrices to examine the potential spatial interactions or constraints and the influencing factors. Results indicate the following. (1) Land urbanization rates in most counties increased, whereas the average ECC per capita in the Wuhan urban agglomeration decreased from 2010 to 2015; (2) China’s land urbanization is primarily driven by socio-economic development, in which fixed asset investments and urban income present positive influences and agricultural outputs show a negative influence; (3) Spatial interaction was formulated through ECC during the land urbanization process. However, this effect was attenuated in 2010–2015. The findings are beneficial for understanding the regional spatial influence of ECC on urban land urbanization. They should also facilitate the formulation of relevant policies for protecting, restoring, and promoting the sustainable use of terrestrial ecosystems to ultimately achieve coordinated and balanced regional development

Upregulation of carbonic anhydrase 1 beneficial for depressive disorder

Abstract Carbonic Anhydrase 1 (CAR1) is a zinc-metalloenzyme that catalyzes the hydration of carbon dioxide, and the alteration of CAR1 has been implicated in neuropsychiatric disorders. However, the mechanism underlying the role of CAR1 in major depressive disorder (MDD) remains largely unknown. In this study, we report the decreased level of CAR1 in MDD patients and depression-like model rodents. We found that CAR1 is expressed in hippocampal astrocytes and CAR1 regulates extracellular bicarbonate concentration and pH value in the partial hilus. Ablation of the CAR1 gene increased the activity of granule cells via decreasing their miniature inhibitory postsynaptic currents (mIPSC), and caused depression-like behaviors in CAR1-knockout mice. Astrocytic CAR1 expression rescued the deficits in mIPSCs of granule cells and reduced depression-like behaviors in CAR1 deficient mice. Furthermore, pharmacological activation of CAR1 and overexpression of CAR1 in the ventral hippocampus of mice improved depressive behaviors. These findings uncover a critical role of CAR1 in the MDD pathogenesis and its therapeutic potential

Clonally related visual cortical neurons show similar stimulus feature selectivity

A fundamental feature of the mammalian neocortex is its columnar organization(1). In the visual cortex, functional columns consisting of neurons with similar orientation preference have been characterized extensively(2-4), but how these columns are constructed during development remains unclear(5). The ‘radial unit hypothesis’(6) posits that the ontogenetic columns formed by clonally related neurons migrating along the same radial glial fiber during corticogenesis(7) provide the basis for functional columns in adult neocortex(1). However, direct correspondence between the ontogenetic and functional columns has not been demonstrated(8). Here we show that, despite the lack of discernible orientation map in mouse visual cortex(4,9,10), sister neurons in the same radial clone exhibit similar orientation preference. Using a retroviral vector encoding green fluorescent protein (GFP) to label radial clones of excitatory neurons and in vivo two-photon calcium imaging to measure the neuronal response properties, we found that sister neurons preferred similar orientations, while nearby non-sisters showed no such relationship. Interestingly, disruption of gap junction coupling by viral expression of a dominant-negative mutant of Cx26 or by daily administration of a gap junction blocker carbenoxolone (CBX) during the first postnatal week greatly diminished the functional similarity between sister neurons, suggesting that the maturation of ontogenetic into functional columns requires intercellular communication through gap junctions. Together with the recent finding of preferential excitatory connections among sister neurons(11), our results support the radial unit hypothesis and unify the ontogenetic and functional columns in the visual cortex