<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dc="http://purl.org/dc/elements/1.1/">
<title>Chemical Sciences</title>
<link href="http://drs.nio.org/drs/handle/2264/3" rel="alternate"/>
<subtitle/>
<id>http://drs.nio.org/drs/handle/2264/3</id>
<updated>2017-07-09T18:04:39Z</updated>
<dc:date>2017-07-09T18:04:39Z</dc:date>
<entry>
<title>Dynamics of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of Cochin estuary, India</title>
<link href="http://drs.nio.org/drs/handle/2264/5088" rel="alternate"/>
<author>
<name>Ramzi, A.;</name>
</author>
<author>
<name>Rahman, K.H.</name>
</author>
<author>
<name>Gireeshkumar, T.R.</name>
</author>
<author>
<name>Balachandran, K.K.</name>
</author>
<author>
<name>Jacob, C.</name>
</author>
<author>
<name>Chandramohanakumar, N.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/5088</id>
<updated>2017-03-01T21:30:15Z</updated>
<published>2017-01-01T00:00:00Z</published>
<summary type="text">Dynamics of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of Cochin estuary, India
Ramzi, A.;; Rahman, K.H.; Gireeshkumar, T.R.; Balachandran, K.K.; Jacob, C.; Chandramohanakumar, N.
Polycyclic aromatic hydrocarbons (PAHs) showed significant seasonal dynamics in surface sediments of a tropical ecosystem (Cochin estuary, south west coast of India). Concentrations ranged from 304 to 5874 ngg&lt;sup&gt;-1&lt;/sup&gt; in pre-monsoon, 493 to 14,149 ngg&lt;sup&gt;-1&lt;/sup&gt; in monsoon, and 194 to 10,691 ngg&lt;sup&gt;-1&lt;/sup&gt; in post-monsoon. The estuary was moderately contaminated with low molecular weight PAH fractions, which increased rapidly during the monsoon season indicating land/river runoff as the major transport pathway. The dominance of 2–3 ring fractions in the PAH indicated petrogenic and low temperature combustion processes as major sources, while the very low levels of 5–6 ring components indicated low contribution from pyrolytic sources. Low molecular weight fractions were higher in concentration than the Effective Range-Median (ERM) levels, whereas high molecular weight PAHs were lower than the Effective Range-Low values (ERL). Calculated carcinogenic toxicity equivalents (TEQ) values ranged from 1 to 971 ng g&lt;sup&gt;-1&lt;/sup&gt; in the surface sediments
</summary>
<dc:date>2017-01-01T00:00:00Z</dc:date>
</entry>
<entry>
<title>N2 production rates limited by nitrite availability in the Bay of Bengal oxygen minimum zone</title>
<link href="http://drs.nio.org/drs/handle/2264/5082" rel="alternate"/>
<author>
<name>Bristow, L.A.</name>
</author>
<author>
<name>Callbeck, C.M.</name>
</author>
<author>
<name>Larsen, M.</name>
</author>
<author>
<name>Altabet, M.A.</name>
</author>
<author>
<name>Dekaezemacker, J.</name>
</author>
<author>
<name>Forth, M.</name>
</author>
<author>
<name>Gauns, M.</name>
</author>
<author>
<name>Glud, R.N.</name>
</author>
<author>
<name>Kuypers, M.M.M.</name>
</author>
<author>
<name>Lavik, G.</name>
</author>
<author>
<name>Milucka, J.</name>
</author>
<author>
<name>Naqvi, S.W.A.</name>
</author>
<author>
<name>Pratihary, A.K.</name>
</author>
<author>
<name>Revsbech, N.P.</name>
</author>
<author>
<name>Thamdrup, B.</name>
</author>
<author>
<name>Treusch, A.H.</name>
</author>
<author>
<name>Canfield, D.E.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/5082</id>
<updated>2017-03-01T21:30:22Z</updated>
<published>2017-01-01T00:00:00Z</published>
<summary type="text">N2 production rates limited by nitrite availability in the Bay of Bengal oxygen minimum zone
Bristow, L.A.; Callbeck, C.M.; Larsen, M.; Altabet, M.A.; Dekaezemacker, J.; Forth, M.; Gauns, M.; Glud, R.N.; Kuypers, M.M.M.; Lavik, G.; Milucka, J.; Naqvi, S.W.A.; Pratihary, A.K.; Revsbech, N.P.; Thamdrup, B.; Treusch, A.H.; Canfield, D.E.
A third or more of the fixed nitrogen lost from the oceans as N&lt;sub&gt;2&lt;/sub&gt; is removed by anaerobic microbial processes in open ocean oxygen minimum zones. These zones have expanded over the past decades, and further anthropogenically induced expansion could accelerate nitrogen loss. However, in the Bay of Bengal there has been no indication of nitrogen loss, although oxygen levels are below the detection level of conventional methods (1 to 2 ìM). Here we quantify the abundance of microbial genes associated with N2 production, measure nitrogen transformations in incubations of sampled seawater with isotopically labelled nitrogen compounds and analyse geochemical signatures of these processes in the water column. We find that the Bay of Bengal supports denitrifier and anammox microbial populations, mediating low, but significant N loss. Yet, unlike other oxygen minimum zones, our measurements using a highly sensitive oxygen sensor demonstrate that the Bay of Bengal has persistent concentrations of oxygen in the 10 to 200 nM range. We propose that this oxygen supports nitrite oxidation, thereby restricting the nitrite available for anammox or denitrification. If these traces of oxygen were removed, nitrogen loss in the Bay of Bengal oxygen minimum zone waters could accelerate to global significance
</summary>
<dc:date>2017-01-01T00:00:00Z</dc:date>
</entry>
<entry>
<title>Influence of atmospheric dry deposition of inorganic nutrients on phytoplankton biomass in the coastal Bay of Bengal</title>
<link href="http://drs.nio.org/drs/handle/2264/5058" rel="alternate"/>
<author>
<name>Yadav, K.</name>
</author>
<author>
<name>Sarma, V.V.S.S.</name>
</author>
<author>
<name>Rao, D.B.</name>
</author>
<author>
<name>DileepKumar, M.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/5058</id>
<updated>2016-12-02T21:30:21Z</updated>
<published>2016-01-01T00:00:00Z</published>
<summary type="text">Influence of atmospheric dry deposition of inorganic nutrients on phytoplankton biomass in the coastal Bay of Bengal
Yadav, K.; Sarma, V.V.S.S.; Rao, D.B.; DileepKumar, M.
The aerosols from continents contain relatively higher amounts of inorganic nutrients than those of marine origin and can make a notable contribution to the coastal biological productivity. To test this hypothesis, the composition of aerosols over the city of Visakhapatnam (central east coast of India) were studied when continental flow was dominant and its impact on phytoplankton biomass was estimated through microcosm experiments between September 2013 and November 2014. Higher nitrate (NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;) and ammonium (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;) concentrations were observed in the aerosols collected in January while higher phosphate (PO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;3-&lt;/sup&gt;) was observed in September. Simultaneous observations of aerosols over the city and neighboring coastal waters revealed that the concentrations of nitrate in ambient aerosols ranged from 0.56 to 1.89 Mug m&lt;sup&gt;-3&lt;/sup&gt; and 0.09 to 0.86 Mu g m&lt;sup&gt;-3&lt;/sup&gt;, respectively. Our results suggest that 52-89% of city's aerosols borne nitrogen deposited over waters within 10 km from the coastline. Microcosm experiments were conducted by spiking the surface water samples, collected from the coastal Bay of Bengal (BoB), with the dust borne nutrients. Upon spiking, dissolved inorganic nitrogen (NO&lt;sub&gt;3-&lt;/sub&gt; + NH&lt;sub&gt;4+&lt;/sub&gt;) increased from 0.3 to 11.7 Mu mol L&lt;sup&gt;-1&lt;/sup&gt; and the N:P ratio increased from 2 to 97. This led to enhanced phytoplankton biomass (1.5 to 4 times) upon spiking. The increase in phytoplankton biomass was linearly related to dissolved N:P ratios in water as aerosol deposition increased the N:P ratios in the microcosms, leading to phytoplankton growth. Though aerosols did not contribute to bioavailable silicate, our microcosm experiments showed linear relationships between ambient silicate phytoplankton biomass, and concentrations of Fucoxanthin (a marker pigment for diatoms). This indicates that the availability of silicate in coastal waters facilitated dominant diatom growth in the presence of higher N:P ratios due to aerosol deposition. The deposition of soluble aerosol nitrogen appears to support ~ 3 to 33% of the biological production in the coastal waters off Visakhapatnam with higher contribution in winter (~ 33%) than in summer (10%). This study suggests that atmospheric deposition of nutrients enhances phytoplankton biomass in waters along the central east coast of India during the winter monsoon period, in particular, supporting the hypothesis stated above
</summary>
<dc:date>2016-01-01T00:00:00Z</dc:date>
</entry>
<entry>
<title>Variability in concentrations and fluxes of methane in the Indian estuaries</title>
<link href="http://drs.nio.org/drs/handle/2264/5042" rel="alternate"/>
<author>
<name>Rao, G.D.</name>
</author>
<author>
<name>Sarma, V.V.S.S.</name>
</author>
<id>http://drs.nio.org/drs/handle/2264/5042</id>
<updated>2016-12-02T21:30:13Z</updated>
<published>2016-01-01T00:00:00Z</published>
<summary type="text">Variability in concentrations and fluxes of methane in the Indian estuaries
Rao, G.D.; Sarma, V.V.S.S.
In order to examine the fluxes of methane (CH4) from the Indian estuaries, measurements were carried out by collecting samples from 26 estuaries along the Indian coast during high discharge (wet) and low water discharge (dry) periods. The CH4 concentrations in the estuaries located along the west coast of India were significantly higher (113  } 40 nM) compared to the east coast of India (27  } 6 nM) during wet and dry periods (88  } 15 and 63  } 12 nM, respectively). Supersaturation of CH4 was observed in the Indian estuaries during both periods ((0.18 to 22.3  ~ 103 %). The concentrations of CH4 showed inverse relation with salinity indicating that freshwater is a significant source. Spatial variations in CH4 saturation were associated with the organic matter load suggesting that its decomposition may be another source in the Indian estuaries. Fluxes of CH4 ranged from 0.01 to 298 ƒÊmol m&amp;#8722;2 day&amp;#8722;1 (mean 13.4  } 5 ƒÊmol m&amp;#8722;2 day&amp;#8722;1) which is ~30 times lower compared to European estuaries (414 ƒÊmol m&amp;#8722;2 day&amp;#8722;1). The annual emission from Indian estuaries, including Pulicat and Adyar, amounted to 0.39  ~ 1010 g CH4 year&amp;#8722;1 with the surface area of 0.027  ~ 106 km2 which is significantly lower than that in European estuaries (2.7  } 6.8  ~ 1010 g CH4 year&amp;#8722;1 with the surface area of 0.03  ~ 106 km2). This study suggests that Indian estuaries are a weak source for atmospheric CH4 than European estuaries and such low fluxes were attributed to low residence time of water and low decomposition of organic matter within the estuary. The CH4 fluxes from the Indian estuaries are higher than those from Indian mangroves (0.01  ~ 1010 g CH4 year&amp;#8722;1) but lower than those from Indian inland waters (210  ~ 1010 g CH4 year&amp;#8722;1)
</summary>
<dc:date>2016-01-01T00:00:00Z</dc:date>
</entry>
</feed>
