Soil metabolic pulses: water, substrate, and biological regulation

Pulses of metabolic activity are a common ecological response to intermittently available resources, and in soils these pulses often occur in response to wetting. To better understand variation in soil pulses, we conducted a distributed field experiment at seven sites along a 2200-m elevation transect in southern California, USA. Treatments included both water and water + substrate additions and two measurements of soil respiration within one hour. These experiments were repeated 11 times throughout 2009-2010. Additions of substrate led to consistently higher pulse fluxes, exceeding 10 micromol CO2 x m(-2( x s(-1), than additions of water alone. These results support a sequential limitation by two resources where an initial limiting resource acts as a switch and, after activation, processes are regulated by a second resource. In contrast to general expectations of increasing pulses with higher soil organic matter (SOM), pulses exhibited strong scale dependencies. Pulses during the summer period and SOM were correlated positively within sites and negatively between sites. This cross-scale divergence implies that, at low elevations, the proportion of SOM available for pulse metabolism was a much larger fraction than at higher elevations. With expected climate changes leading to more frequent drying-wetting cycles, regulation of metabolic pulses will increasingly influence long-term biogeochemical dynamics.     

A study on the phytoaccumulation of waste elements in wetland plants of a Ramsar site in India

Some wetland plant species are adapted to growing in the areas of higher metal concentrations. Use of such vegetation in remediation of soil and water contaminated with heavy metals is a promising cost-effective alternative to the more established treatment methods. Throughout the year, composite industrial effluents bringing various kinds of heavy metals contaminate our study site, the East Calcutta Wetlands, a Ramsar site at the eastern fringe of Kolkata city (formerly Calcutta), India. In the present study, possible measures for remediation of contaminated soil and water (with elements namely, Ca, Cr, Cu, Pb, Zn, Mn, and Fe) of the ecosystem had been investigated. Ten common regional wetland plant species were selected to study their efficiency and diversity in metal uptake and accumulation. Results showed that Bermuda grass (Cynodon dactylon) had the highest total Cr concentration (6,601 ± 33 mg kg^???1 dw). The extent of accumulation of various elements in ten common wetland plants of the study sites was: Pb (4.4?C57 mg kg^???1 dw), Cu (6.2?C39 mg kg^???1 dw), Zn (59?C364 mg kg^???1 dw), Mn (87?C376 mg kg^???1 dw), Fe (188?C8,625 mg kg^???1 dw), Ca (969?C3,756 mg kg^???1 dw), and Cr (27?C660 mg kg^???1 dw) indicating an uptake gradient of elements by plants as Ca>Fe>Mn>Cr>Zn>Cu>Pb. The present study indicates the importance of identification and efficiency of metal uptake and accumulation capabilities by plants in relation to their applications in remediation of a contaminated East Calcutta Wetland ecosystem.     

Plastic waste management practices pertaining to India with particular focus on emerging technologies

Environmental Science and Pollution Research - Under the parent petrochemical industries, plastic industry is proliferating enormously over the past several years globally due to its advantages in...     

Fabrication of ZnO–SnO2 nanocomposite and its photocatalytic activity for enhanced degradation of Biebrich scarlet

Environmental Science and Pollution Research - The n–n-type ZnO–SnO2 nanocomposite was fabricated using malic acid following a simple one-pot co-precipitation method. The fabricated...     

Role of competition in phytoplankton population for the occurrence and control of plankton bloom in the presence of environmental fluctuations

Termination of harmful algal blooms (HABs) and coexistence of phytoplankton–zooplankton populations are of great importance to human health, ecosystem, environment, tourism and fisheries. In this paper, we propose a three component model consisting of non-toxic phytoplankton (NTP), toxin producing phytoplankton (TPP) and zooplankton (Z). The growth of zooplankton species is assume to reduce due to toxic chemicals released by TPP population. We have extended the model proposed by Chattopadhyay et al. [Chattopadhyay, J., Sarkar, R.R., Pal, S., 2004. Mathematical modelling of harmful algal blooms supported by experimental findings. Ecol. Comp. 1, 225–235] by including competition terms between TPP and NTP. We observe the effect of competition factors both in the presence and absence of the environmental fluctuation. From our field as well as model analysis we observe that competition helps in the coexistence of the species, but if the effect of competition is very high on the TPP population, it results in planktonic bloom. It is shown that the coexistence equilibrium loses its stability when the competition coefficient crosses a critical value and resulting Hopf-bifurcation around the positive equilibrium depicting oscillations phenomena of the populations.     

Distribution and possible source of trace elements in the sediment cores of a tropical macrotidal estuary and their ecotoxicological significance

The paper presents the first document regarding concentration, distribution and possible sources of selected trace elements (Cu, Fe, Mn, Zn, Cr, Co, Ni, Pb, Al, B and Ba) in core sediments (<63 micro particle size) from the lower stretch of Hugli (Ganges) estuary, northeast coast of Bay of Bengal by ICP-AES and EDXRF to evaluate geochemical processes influencing their distribution and possible environmental consequences. The levels of elements showed a wide range of variations in different core depths, in upper and lower intertidal zones as well as among three sampling stations. The most interesting feature of the study is the downward increase of concentrations of majority of the elements reaching overall maximum values at a depth of 20-28 cm in upper littoral zone of the site located in the extreme downstream stretch of the estuary. Values of organic carbon showed very strong positive correlations with most of the elements as revealed by correlation matrix (r) values. The interelemental relationship revealed the identical behavior of element during its transport in the estuarine environment. The overall variation in concentration can be attributed to differential discharge of untreated effluents originating from industrial, agricultural, and aquacultural sources as well as from domestic sewage along with the fishing and boating activities. The resulting compositional dataset was tested by principal component analyses and cluster analyses. Pollution load index (PLI) and index of Geoaccumulation (Igeo) revealed overall low values but the enrichment factors (EFs) for Pb were typically high for all the stations. The mean concentrations of Zn and to some extent Cu exceeded the Effects Range-Low (ER-L) values in the majority of the cases indicating that there may be some ecotoxicological risk to organisms living in sediments. The concentration of the trace elements reported in this work is useful as baselines for comparison in future sediment quality studies.     

Prenatal diagnosis of aortic atresia by colour doppler flow mapping

A case of aortic atresia with insufficiency of mitral valve diagnosed prenatally at 33 weeks of gestation is presented. An accurate diagnosis of this fetal cardiovascular malformation was possible by application of Doppler colour flow mapping, which demonstrated (a) the absence of forward flow in the hypoplastic ascending aorta, (b) reverse flow of blood from the ductus arteriosus into the severely hypoplastic ascending aorta in the late systole, (c) pansystolic mitral valve regurgitation, and (d) absent flow across the foramen ovale as a result of premature closure of the foramen ovale.