Fate and Transport of Selected Herbicides in an Estuarine Environment

1983 ◽  
Vol 40 (S2) ◽  
pp. s337-s345 ◽  
Author(s):  
J. C. Means ◽  
R. D. Wijayaratne ◽  
W. R. Boynton
Keyword(s):  
Chesapeake Bay ◽  
Water Column ◽  
Fate And Transport ◽  
Water Systems ◽  
Estuarine Environment ◽  
Estuarine Sediments ◽  
Equilibrium Sorption ◽  
Degradation Rates ◽  
Hydrophobic Pollutants ◽  
Ambient Levels

Representative compounds from three classes of herbicides (atrazine, linuron, and treflan) were studied to determine ambient levels in the Chesapeake Bay and its tributaries during portions of 1980. All levels were 1 μg/L or less, and all three herbicides exhibited non-conservative behavior in the estuary. Concentrations of herbicides in runoff from a defined watershed did not exceed 9 μg/L. Degradation rates for all three herbicides in estuarine sediment-water systems were 2–10 times greater than those reported for soils. Equilibrium sorption constants (Koc) of estuarine sediments were similar to soils, but suspended colloids were found to sorb atrazine and linuron 10–30 times more strongly on a per gram of carbon basis, suggesting that refractory hydrophobic pollutants may be transported greater distances in the water column than previously assumed. However, the large degradative capacity of the estuarine community may act to prevent transport of labile organics from the land to the oceans.

scholarly journals Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay

2018 ◽  
Vol 15 (20) ◽  
pp. 6127-6138 ◽  
Author(s):  
Qixing Ji ◽  
Claudia Frey ◽  
Xin Sun ◽  
Melanie Jackson ◽  
Yea-Shine Lee ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Chesapeake Bay ◽  
Water Column ◽  
N2o Emissions ◽  
N2o Production ◽  
Isotope Tracer ◽  
Relative Contribution ◽  
Environmental Controls ◽  
Long Run ◽  
Nitrate And Nitrite

Abstract. Nitrous oxide (N2O) is a greenhouse gas and an ozone depletion agent. Estuaries that are subject to seasonal anoxia are generally regarded as N2O sources. However, insufficient understanding of the environmental controls on N2O production results in large uncertainty about the estuarine contribution to the global N2O budget. Incubation experiments with nitrogen stable isotope tracer were used to investigate the geochemical factors controlling N2O production from denitrification in the Chesapeake Bay, the largest estuary in North America. The highest potential rates of water column N2O production via denitrification (7.5±1.2 nmol-N L−1 h−1) were detected during summer anoxia, during which oxidized nitrogen species (nitrate and nitrite) were absent from the water column. At the top of the anoxic layer, N2O production from denitrification was stimulated by addition of nitrate and nitrite. The relative contribution of nitrate and nitrite to N2O production was positively correlated with the ratio of nitrate to nitrite concentrations. Increased oxygen availability, up to 7 µmol L−1 oxygen, inhibited both N2O production and the reduction of nitrate to nitrite. In spring, high oxygen and low abundance of denitrifying microbes resulted in undetectable N2O production from denitrification. Thus, decreasing the nitrogen input into the Chesapeake Bay has two potential impacts on the N2O production: a lower availability of nitrogen substrates may mitigate short-term N2O emissions during summer anoxia; and, in the long-run (timescale of years), eutrophication will be alleviated and subsequent reoxygenation of the bay will further inhibit N2O production.

scholarly journals Modelling approach to the assessment of biogenic fluxes at a selected Ross Sea site, Antarctica

2009 ◽  
Vol 6 (2) ◽  
pp. 1477-1512 ◽  
Author(s):  
M. Vichi ◽  
A. Coluccelli ◽  
M. Ravaioli ◽  
F. Giglio ◽  
L. Langone ◽  
...  
Keyword(s):  
Bottom Sediment ◽  
Water Column ◽  
Sediment Trap ◽  
Biogeochemical Model ◽  
Bacterial Respiration ◽  
Deposition Flux ◽  
Austral Spring ◽  
Degradation Rates ◽  
Biogenic Material ◽  
Biogenic Fluxes

Abstract. Several biogeochemical data have been collected in the last 10 years of Italian activity in Antarctica (ABIOCLEAR, ROSSMIZE, BIOSESO-I/II). A comprehensive 1-D biogeochemical model was implemented as a tool to link observations with processes and to investigate the mechanisms that regulate the flux of biogenic material through the water column. The model is ideally located at station B (175° E–74° S) and was set up to reproduce the seasonal cycle of phytoplankton and organic matter fluxes as forced by the dominant water column physics over the period 1990–2001. Austral spring-summer bloom conditions are assessed by comparing simulated nutrient drawdown, primary production rates, bacterial respiration and biomass with the available observations. The simulated biogenic fluxes of carbon, nitrogen and silica have been compared with the fluxes derived from sediment traps data. The model reproduces the observed magnitude of the biogenic fluxes, especially those found in the bottom sediment trap, but the peaks are markedly delayed in time. Sensitivity experiments have shown that the characterization of detritus, the choice of the sinking velocity and the degradation rates are crucial for the timing and magnitude of the vertical fluxes. An increase of velocity leads to a shift towards observation but also to an overestimation of the deposition flux which can be counteracted by higher bacterial remineralization rates. Model results suggest that the timing of the observed fluxes depends first and foremost on the timing of surface production and on a combination of size-distribution and quality of the autochtonous biogenic material. It is hypothesized that the bottom sediment trap collects material originated from the rapid sinking of freshly-produced particles and also from the previous year's production period.

scholarly journals Iron and manganese cycling influence on alkalinity from a redox stratified water column of the Chesapeake Bay

2021 ◽  
Author(s):  
Aubin Thibault de Chanvalon ◽  
George Luther ◽  
Wei-Jun Cai ◽  
Bradley Tebo ◽  
Emily Estes ◽  
...  
Keyword(s):  
Chesapeake Bay ◽  
Water Column ◽  
Iron And Manganese

scholarly journals Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

2020 ◽  
Vol 44 (1) ◽  
pp. 103-122
Author(s):  
Julia M. Moriarty ◽  
Marjorie A. M. Friedrichs ◽  
Courtney K. Harris
Keyword(s):  
Organic Matter ◽  
Chesapeake Bay ◽  
Water Column ◽  
Primary Productivity ◽  
Environmental Changes ◽  
Light Attenuation ◽  
Sediment Resuspension ◽  
Nitrogen Dynamics ◽  
Biogeochemical Model ◽  
Order Of Magnitude

AbstractSediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic–sediment transport–biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.

Simultaneous butyltin determinations in the microlayer, water column and sediment of a northern Chesapeake Bay marina and receiving system

1988 ◽  
Vol 2 (6) ◽  
pp. 547-552 ◽  
Author(s):  
Cheryl L Matthias ◽  
Steven J Bushong ◽  
Lenwood W Hall ◽  
Jon M Bellama ◽  
F E Brinckman
Keyword(s):  
Chesapeake Bay ◽  
Water Column

Internal recycling of particle reactive organic chemicals in the Chesapeake Bay water column

2003 ◽  
Vol 81 (3-4) ◽  
pp. 163-176 ◽  
Author(s):  
Fung-Chi Ko ◽  
Lawrence P Sanford ◽  
Joel E Baker
Keyword(s):  
Chesapeake Bay ◽  
Water Column ◽  
Organic Chemicals
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