Long-term changes in climate, streamflow, and nutrient budgets for first-order catchments at the Experimental Lakes Area (Ontario, Canada)This paper is part of the series “Forty Years of Aquatic Research at the Experimental Lakes Area”.

2009 ◽  
Vol 66 (11) ◽  
pp. 1848-1863 ◽  
Author(s):  
Brian R. Parker ◽  
David W. Schindler ◽  
Ken G. Beaty ◽  
Michael P. Stainton ◽  
Susan E.M. Kasian
Keyword(s):  
Forest Succession ◽  
Summer Precipitation ◽  
Experimental Lakes Area ◽  
Dissolved Nitrogen ◽  
Total Dissolved Nitrogen ◽  
Apparent Relationship ◽  
Central United States ◽  
Long Term Trends ◽  
Lake Catchment

We analyzed 36 years of records for climate, hydrology, and the chemistry of precipitation and runoff from the Lake 239 (Rawson Lake) catchment at the Experimental Lakes Area (Ontario, Canada). No evidence of significant periodicity was found for any variable in the Experimental Lakes Area records. The longer (67-year) record from nearby Kenora, Ontario, revealed a 31-year cycle in precipitation but not temperature. Significant increasing long-term trends at the Experimental Lakes Area were found for annual and winter temperature and summer precipitation and deposition of ammonium, total nitrogen (TN), and total dissolved nitrogen (TDN). Large (80%) increases in ammonium deposition appear to be related to higher emissions in the central United States. A significant negative trend for dissolved organic carbon (DOC) in precipitation cannot be explained. In runoff, significant positive trends were found for TDN and DOC in the northeast catchment and TN, TDN, ammonium, and DOC in the northwest. Significant negative trends were found for TDP and nitrate in the northeast. Significant increases were found for retention of ammonium in all catchments and DOC in the northeast and northwest. There was no apparent relationship between forest succession and retention of nutrients. Results are compared with those from three other long-term monitoring sites in eastern North America.

Long-Term Trends in Urban Forest Succession

2019 ◽  
pp. 236-250
Author(s):  
Grace S. Brush ◽  
Daniel J. Bain
Keyword(s):  
Urban Forest ◽  
Forest Succession ◽  
Long Term Trends

Preliminary Chemical Characterization of Waters in the Experimental Lakes Area, Northwestern Ontario

1971 ◽  
Vol 28 (2) ◽  
pp. 171-187 ◽  
Author(s):  
F. A. J. Armstrong ◽  
D. W. Schindler
Keyword(s):  
Chemical Characterization ◽  
Specific Conductance ◽  
Canadian Shield ◽  
Nitrogen And Phosphorus ◽  
Experimental Lakes Area ◽  
Mean Values ◽  
Dissolved Phosphorus ◽  
Dissolved Nitrogen ◽  
Total Dissolved Nitrogen ◽  
Northwestern Ontario

Water analyses in 1968 and 1969 from 40 small lakes within a small area of the Canadian Shield in northwestern Ontario gave mean values for Ca, Na, Mg, and K of 1.6, 0.9, 0.9, and 0.4 mg/liter with Ca > Na > Mg > K on a molar basis. HCO3, SO4, and Cl (on a smaller number of samples) were 4.1, 3.0, and 1.4 mg/liter. Total CO2 was variable in the range 0.3–12.0 mg/liter. Specific conductance was in the range 10–35 μmho/cm at 25 C and pH 5.4–7.5. Color was < 5–150 Hazen units, and plant pigments (as chlorophyll a) < 1–21 μg/liter. Total dissolved nitrogen was in the range 110–300 mg N/liter and total dissolved phosphorus 3–20 μg P/liter. NO3-N and PO4-P were often undetectable in summer, and reached winter maxima around 100 and 10 μg/liter.Total dissolved nitrogen and phosphorus contents of five lakes were computed at the beginning and end of periods of several weeks during summer stagnation. Changes were negligibly small in three of the deeper lakes, but the two shallowest showed increases of 0.22 and 0.62 g N/m2 and 0.03 and 0.13 g P/m2. Analyses of precipitation and stream waters were used, with stream flow rates, to calculate input and output of nutrients from four of these lakes during the same periods. Retention of nutrients had occurred in all, and it was concluded that in the two deeper lakes nutrients had been lost to the sediments, whereas in the two shallower ones the increases in dissolved nutrients found were derived from the sediments.Analyses of 33 other Canadian Shield lake areas and of 13 other dilute lakes in other regions are tabulated. Comparison with the Experimental Lakes Area (ELA) lakes shows that the latter are more dilute than any in the Shield area except for some in the Northwest Territories, and much more dilute than any others in the world except for some alpine lakes in California.

Seasonal variation of nitrogen biogeochemical processes constrained by nitrate dual isotopes in cascade reservoirs, Southwestern China 

2021 ◽  
Author(s):  
Sainan Chen ◽  
Fu-Jun Yue ◽  
Xiao-Long Liu ◽  
Jun Zhong ◽  
Yuan-Bi Yi ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Fertilizer Application ◽  
Isotopic Signature ◽  
Average Concentration ◽  
Cascade Reservoirs ◽  
Dissolved Nitrogen ◽  
Total Dissolved Nitrogen ◽  
N Concentration ◽  
The Relationship

&lt;p&gt;The increase of affected river reaches by reservoirs has drastically disturbed the original hydrological conditions, and subsequently influenced the nutrient biogeochemistry in the aquatic system, particularly in the cascade reservoir system. To understand the seasonal variation of nitrogen (N) behaviors in cascade reservoirs, hydrochemistry and nitrate dual isotopes (&amp;#948;&lt;sup&gt;15&lt;/sup&gt;N-NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;#8722; &lt;/sup&gt;and&lt;sup&gt;&lt;/sup&gt;&amp;#948;&lt;sup&gt;18&lt;/sup&gt;O-NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;#8722;&lt;/sup&gt;) were conducted in a karst watershed (Wujiang River) in southwest China. The results showed that NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&amp;#8211;N accounted for almost 90% of the total dissolved nitrogen (TDN) concentration with high average concentration 3.8 &amp;#177; 0.4 mg/L among four cascade reservoirs. Higher N concentration (4.0 &amp;#177; 0.8 mg/L) and larger longitudinal variation were observed in summer than in other seasons. The relationship between the variation of NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&amp;#8211;N and dual isotopes in the profiles demonstrated that nitrification was dominated transformation, while assimilation contributed significantly in the epilimnion during spring and summer. The high dissolved oxygen concentration in the present cascade reservoirs system prevented the occurrence of N depletion processes in most of the reservoirs. Denitrification occurred in the oldest reservoir during winter with a rate ranging from 18 % to 28 %. The long-term record of surface water TDN concentration in reservoirs demonstrated an increase from 2.0 to 3.6 mg/L during the past two decades (~ 0.1 mg/L per year). The seasonal nitrate isotopic signature and continuously increased fertilizer application demonstrated that chemical fertilizer contribution significantly influenced NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;#8722;&lt;/sup&gt;&amp;#8211;N concentration in the karst cascade reservoirs. The research highlighted that the notable N increase in karst cascade reservoirs could influence the aquatic health in the region and further investigations were required.&lt;/p&gt;

scholarly journals Trends in U.S. Surface Humidity, 1930–2010

2013 ◽  
Vol 52 (1) ◽  
pp. 147-163 ◽  
Author(s):  
Paula J. Brown ◽  
Arthur T. DeGaetano
Keyword(s):  
Relative Humidity ◽  
Specific Humidity ◽  
Atmospheric Moisture ◽  
Detection Rates ◽  
Temperature Trends ◽  
Homogeneity Assessment ◽  
Central United States ◽  
Breakpoint Detection ◽  
Long Term Trends

AbstractU.S. hourly surface observations are examined at 145 stations to identify annual and seasonal changes in temperature, dewpoint, relative humidity, and specific humidity since 1930. Because of numerous systematic instrument changes that have occurred, a homogeneity assessment was performed on temperatures and dewpoints. Dewpoints contained higher breakpoint detection rates associated with instrumentation changes than did temperatures. Temperature trends were tempered by adjusting the data, whereas dewpoints were unaffected. The effects were the same whether the adjustments were based on statistically detected or fixed-year breakpoints. Average long-term trends (1930–2010) indicate that temperature has warmed but that little change has occurred in dewpoint and specific humidity. Warming is strongest in spring. There is evidence of inhomogeneity in the relative humidity record that primarily affects data from prior to 1950. Therefore, long-term decreases in relative humidity, which are strongest in winter, need to be viewed with caution. Trends since 1947 indicate that the warming of temperatures has coincided with increases in dewpoints and a moistening of specific humidity. This moistening is especially pronounced during the summer in the Midwest. For the nation, trends in relative humidity show little change for the period 1947–2010, during which these data are more homogeneous. Moistening has occurred throughout the central United States while other regions have experienced drying. Urban-related warming and drying trends are present in the data, but their effect is minimal. Regional changes in land use and moisture availability are likely influencing trends in atmospheric moisture.

Corrigendum to: Long-term watershed management is an effective strategy to reduce organic matter export and disinfection by-product precursors in source water

2019 ◽  
Vol 28 (10) ◽  
pp. 822 ◽  
Author(s):  
Hamed Majidzadeh ◽  
Huan Chen ◽  
T. Adam Coates ◽  
Kuo-Pei Tsai ◽  
Christopher I. Olivares ◽  
...  
Keyword(s):  
Organic Matter ◽  
South Carolina ◽  
Watershed Management ◽  
Prescribed Fire ◽  
Management Practices ◽  
Long Term Effects ◽  
Dissolved Nitrogen ◽  
Total Dissolved Nitrogen

Watershed management practices such as prescribed fire, harvesting and understory mastication can alter the chemical composition and thickness of forest detritus, thus affecting the quantity and quality of riverine dissolved organic matter (DOM). Long-term effects of watershed management on DOM composition were examined through parallel field and extraction-based laboratory studies. The laboratory study was conducted using detritus samples collected from a pair of managed and unmanaged watersheds in South Carolina, USA. Results showed that dissolved organic carbon (DOC), total dissolved nitrogen (TDN) and ammonium (NH4+-N) concentrations were higher in water extracts from the unmanaged watershed than from the managed watershed (PPP

Delineating Long-Term Trends in Beach Change, Central California

2005 ◽  
Author(s):  
Cope M. Willis ◽  
Gary B. Griggs
Keyword(s):  
Central California ◽  
Long Term Trends

Analysis of variability and long-term trends of sea surface temperature over the China Seas derived from a newly merged regional data set

2017 ◽  
Vol 73 (3) ◽  
pp. 217-231 ◽  
Author(s):  
Y Li ◽  
L Mu ◽  
Y Liu ◽  
G Wang ◽  
D Zhang ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Surface ◽  
China Seas ◽  
Regional Data ◽  
Data Set ◽  
Long Term Trends ◽  
The China Seas

Commercial trawling in seagrass beds: bycatch and long-term trends in effort of a major shrimp fishery

2014 ◽  
Vol 513 ◽  
pp. 143-153 ◽  
Author(s):  
CD Stallings ◽  
JP Brower ◽  
JM Heinlein Loch ◽  
A Mickle
Keyword(s):  
Seagrass Beds ◽  
Shrimp Fishery ◽  
Long Term Trends

Long-Term Trends in the Asia-Pacific Region: A Soviet Evaluation

Asian Survey ◽  
1989 ◽  
Vol 29 (3) ◽  
pp. 237-251 ◽  
Author(s):  
Henry Trofimenko
Keyword(s):  
Asia Pacific ◽  
Pacific Region ◽  
Asia Pacific Region ◽  
Long Term Trends
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