Hypoxia in Chesapeake Bay, 1950–2001: Long-term change in relation to nutrient loading and river flow

Estuaries ◽  
2004 ◽  
Vol 27 (4) ◽  
pp. 634-658 ◽  
Author(s):  
James D. Hagy ◽  
Walter R. Boynton ◽  
Carolyn W. Keefe ◽  
Kathryn V. Wood
Keyword(s):  
Chesapeake Bay ◽  
Nutrient Loading ◽  
River Flow ◽  
Term Change

Full scale implementation of post denitrification at the Blue Plains AWT in Washington D.C.

2000 ◽  
Vol 41 (9) ◽  
pp. 29-36 ◽  
Author(s):  
T. Sadick ◽  
W. Bailey ◽  
A. Tesfaye ◽  
M. McGrath ◽  
G. Daigger ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Chesapeake Bay ◽  
Nutrient Loading ◽  
District Of Columbia ◽  
Full Scale ◽  
Demonstration Project ◽  
Nitrogen Reduction ◽  
Year 2000 ◽  
Denitrification Process

The Chesapeake Bay Agreement of 1987 calls for an overall reduction in nutrient loading to the Bay of forty percent of 1985 levels by the year 2000. Signatories to the agreement include the states located in the Bay's watershed and the District of Columbia. The District's 16.2 m3 /sec (370 mgd) Blue Plains Advanced Wastewater Treatment (AWT) Plant is the single, largest point source of nitrogen load to the Bay, currently discharging approximately 18 metric tons (40,000 lbs) per day. In an effort toward meeting the nitrogen reduction goal, a post-denitrification demonstration project was recently undertaken to access its potential for long-term implementation. The denitrification demonstration project involved operating half of the nitrification facilities in a nitrification-denitrification mode using methanol as a carbon source for post-denitrification. The remaining half continued operation in a nitrification-only mode as a control. The two-year demonstration project was successful in meeting nitrogen reduction goals while meeting all other permit conditions. The District of Columbia Water and Sewer Authority is now proceeding to voluntarily implement the post denitrification process on a permanent, full-scale basis.

Long-Term Trends in Chesapeake Bay Seasonal Hypoxia, Stratification, and Nutrient Loading

2011 ◽  
Vol 34 (6) ◽  
pp. 1293-1309 ◽  
Author(s):  
Rebecca R. Murphy ◽  
W. Michael Kemp ◽  
William P. Ball
Keyword(s):  
Chesapeake Bay ◽  
Nutrient Loading ◽  
Long Term Trends ◽  
Seasonal Hypoxia

scholarly journals Modeling drivers of phosphorus loads in Chesapeake Bay tributaries and inferences about long-term change

2018 ◽  
Vol 616-617 ◽  
pp. 1423-1430 ◽  
Author(s):  
Karen R. Ryberg ◽  
Joel D. Blomquist ◽  
Lori A. Sprague ◽  
Andrew J. Sekellick ◽  
Jennifer Keisman
Keyword(s):  
Chesapeake Bay ◽  
Term Change ◽  
Phosphorus Loads

Vivid Imagers Are Better at Detecting Salient Changes

2006 ◽  
Vol 27 (4) ◽  
pp. 218-228 ◽  
Author(s):  
Paul Rodway ◽  
Karen Gillies ◽  
Astrid Schepman
Keyword(s):  
Individual Differences ◽  
Change Detection ◽  
Visual Imagery ◽  
Detection Task ◽  
Level Of Detail ◽  
Detection Accuracy ◽  
Change Detection Task ◽  
Term Change ◽  
High Level

This study examined whether individual differences in the vividness of visual imagery influenced performance on a novel long-term change detection task. Participants were presented with a sequence of pictures, with each picture and its title displayed for 17  s, and then presented with changed or unchanged versions of those pictures and asked to detect whether the picture had been changed. Cuing the retrieval of the picture's image, by presenting the picture's title before the arrival of the changed picture, facilitated change detection accuracy. This suggests that the retrieval of the picture's representation immunizes it against overwriting by the arrival of the changed picture. The high and low vividness participants did not differ in overall levels of change detection accuracy. However, in replication of Gur and Hilgard (1975) , high vividness participants were significantly more accurate at detecting salient changes to pictures compared to low vividness participants. The results suggest that vivid images are not characterised by a high level of detail and that vivid imagery enhances memory for the salient aspects of a scene but not all of the details of a scene. Possible causes of this difference, and how they may lead to an understanding of individual differences in change detection, are considered.

Chesapeake Bay Stock Assessment: Who are they, and Where are they?

1992 ◽  
Vol 26 (12) ◽  
pp. 2705-2709 ◽  
Author(s):  
H. M. Austin
Keyword(s):  
Chesapeake Bay ◽  
Stock Assessment ◽  
Human Consumption ◽  
Population Fluctuations ◽  
Important Species ◽  
Fisheries Resources ◽  
Environmentally Sensitive ◽  
Climate Scale ◽  
Resource And Environment

The Chesapeake Bay, while a significant habitat for fisheries resources, is in actuality an aquatic “bedroom community”, as many of the economically important species are seasonally transient. The pressure on these resources due to their demand for human consumption and recreation, proximity to extensive industrial activity along the shores, and climate scale environmental fluctuations has resulted in stock declines by most important species. Our inability to separate natural population fluctuations from those of anthropogenic origin complicates management efforts. The only way to make these separations, and subsequent informed management decisions is by supporting long-term stock assessment programs (monitoring) in the Bay which allow us to examine trends, cycles and stochastic processes between resource and environment. These programs need to monitor both recruitment and fishing mortality rates of the economically important species, and to identify and monitor the environmentally sensitive “canary” species.

Social Cohesion, Breaks, and Transformations in Italy, 535–600

2018 ◽  
Author(s):  
Walter Pohl
Keyword(s):  
The Political ◽  
Late Antique ◽  
Religious Context ◽  
Ancient Society ◽  
Complex Process ◽  
Term Change ◽  
Two Generations ◽  
Classical Culture

When the Gothic War began in Italy in 535, the country still conserved many features of classical culture and late antique administration. Much of that was lost in the political upheavals of the following decades. Building on Chris Wickham’s work, this contribution sketches an integrated perspective of these changes, attempting to relate the contingency of events to the logic of long-term change, discussing political options in relation to military and economic means, and asking in what ways the erosion of consensus may be understood in a cultural and religious context. What was the role of military entrepreneurs of more or less barbarian or Roman extraction in the distribution or destruction of resources? How did Christianity contribute to the transformation of ancient society? The old model of barbarian invasions can contribute little to understanding this complex process. It is remarkable that for two generations, all political strategies in Italy ultimately failed.

Enhanced Seasonal Exchange of CO2 by Northern Ecosystems Since 1960

Science ◽  
2013 ◽  
Vol 341 (6150) ◽  
pp. 1085-1089 ◽  
Author(s):  
H. D. Graven ◽  
R. F. Keeling ◽  
S. C. Piper ◽  
P. K. Patra ◽  
B. B. Stephens ◽  
...  
Keyword(s):  
Boreal Forests ◽  
Atmospheric Carbon Dioxide ◽  
Ecosystem Models ◽  
The North ◽  
Ecological Changes ◽  
Term Change ◽  
Major Shift ◽  
Underlying Mechanisms ◽  
Global Carbon

Seasonal variations of atmospheric carbon dioxide (CO2) in the Northern Hemisphere have increased since the 1950s, but sparse observations have prevented a clear assessment of the patterns of long-term change and the underlying mechanisms. We compare recent aircraft-based observations of CO2 above the North Pacific and Arctic Oceans to earlier data from 1958 to 1961 and find that the seasonal amplitude at altitudes of 3 to 6 km increased by 50% for 45° to 90°N but by less than 25% for 10° to 45°N. An increase of 30 to 60% in the seasonal exchange of CO2 by northern extratropical land ecosystems, focused on boreal forests, is implicated, substantially more than simulated by current land ecosystem models. The observations appear to signal large ecological changes in northern forests and a major shift in the global carbon cycle.

scholarly journals High Mountain Asian glacier response to climate revealed by multi-temporal satellite observations since the 1960s

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Atanu Bhattacharya ◽  
Tobias Bolch ◽  
Kriti Mukherjee ◽  
Owen King ◽  
Brian Menounos ◽  
...  
Keyword(s):  
Mass Loss ◽  
River Flow ◽  
Tien Shan ◽  
High Mountain ◽  
Glacier Mass Balance ◽  
Temperature And Precipitation ◽  
Multi Temporal ◽  
The 1960S ◽  
Northern Tien Shan

AbstractKnowledge about the long-term response of High Mountain Asian glaciers to climatic variations is paramount because of their important role in sustaining Asian river flow. Here, a satellite-based time series of glacier mass balance for seven climatically different regions across High Mountain Asia since the 1960s shows that glacier mass loss rates have persistently increased at most sites. Regional glacier mass budgets ranged from −0.40 ± 0.07 m w.e.a−1 in Central and Northern Tien Shan to −0.06 ± 0.07 m w.e.a−1 in Eastern Pamir, with considerable temporal and spatial variability. Highest rates of mass loss occurred in Central Himalaya and Northern Tien Shan after 2015 and even in regions where glaciers were previously in balance with climate, such as Eastern Pamir, mass losses prevailed in recent years. An increase in summer temperature explains the long-term trend in mass loss and now appears to drive mass loss even in regions formerly sensitive to both temperature and precipitation.

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