493 research outputs found
Improving the Understanding of N Transport in a Rural Catchment Under Atlantic Climate Conditions From the Analysis of the ConcentrationâDischarge Relationship Derived From a High-Frequency Data Set
[Abstract] Understanding processes controlling stream nutrient dynamics over time is crucial for implementing effective management strategies to prevent water quality degradation. In this respect, the study of the nutrient concentrationâdischarge (CâQ) relationship during individual runoff events can be a valuable tool for extrapolating the hydrochemical processes controlling nutrient fluxes in streams. This study investigated nitrogen concentration dynamics during events by analyzing and interpreting the nitrogen CâQ relationship in a small Atlantic (NW Iberian Peninsula) rural catchment. To this end, nitrate (NO3-N) and total Kjeldahl nitrogen (TKN) concentrations were monitored at a high temporal resolution during 102 runoff events over a 6-year period. For each of the selected runoff events, CâQ response was examined visually for the presence and direction of hysteresis loops and classified into three types of responses, namely clockwise, counterclockwise, and no hysteresis. Changes in concentration (ÎC) and the hysteresis direction (ÎR) were used to quantify nitrogen (
and TKN) patterns during the runoff events. The transport mechanisms varied between compounds. The most frequent hysteretic response for was counterclockwise with enrichment. On the contrary, the main TKN dynamic was enrichment with clockwise hysteresis. Event characteristics, such as rainfall amount, peak discharge (i.e., maximum discharge of the runoff event), and event magnitude relative to the initial baseflow (i.e., the difference between the maximum discharge of the runoff event and the initial baseflow divided by initial baseflow) provided a better explanation for hysteresis direction and magnitude for TKN than antecedent conditions (antecedent precipitation and baseflow at the beginning of the event). For hysteresis, the role of hydrometeorological conditions was more complex. The hysteresis magnitude was related to the magnitude of the event relative to the initial baseflow and the time elapsed since a preceding runoff event. These findings could be used as a reference for the development of N mitigation strategy in the region.This research has been supported by the Spanish Ministry of Education and Science (grant no. REN2003-08143) and Xunta of Galicia (grant nos. PGIDIT05RAG10303PR and 10MDS103031PR)Xunta of Galicia; PGIDIT05RAG10303PRXunta of Galicia; 10MDS103031P
Characteristics principals of soils of HolguĂn province (Cuba). Use and soils management
[Abstract] In this paper was performed an compilation of the main characteristic and degradation processes of soils HolguĂn province (Cuba) in order to stablish a proposal management leading to soil preservation. The main soils in the zone are of four types. According to the cuban classification system the major soils are Fersialitics, Vertisoils, Bruns and Ferritic, which are respectively equivalent to the Luvisols, Vertisols, Cambisols and Ferralsols of the FAO system (1998). About 70% of the agricultural soils of the HolguĂn province are affected by different erosion degree. About 17% of soils are affected by salinity and are associated mainly to the group of Vertisoils, that in the greater part are dedicated to the sugarcane cultivated and at grassland. Together with the erosion and salinity procceses others limiting factors of the soils are the sodicity, contents of gravels and stones, efective deepth, carbonates content and relief
Improving the understanding of N transport in a rural catchment under Atlantic climate conditions from the analysis of the concentrationâdischarge relationship derived from a high-frequency data set
Understanding processes controlling stream nutrient dynamics over time is crucial for implementing effective management strategies to prevent water quality degradation. In this respect, the study of the nutrient concentrationâdischarge (CâQ) relationship during individual runoff events can be a valuable tool for extrapolating the hydrochemical processes controlling nutrient fluxes in streams. This study investigated nitrogen concentration dynamics during events by analyzing and interpreting the nitrogen CâQ relationship in a small Atlantic (NW Iberian Peninsula) rural catchment. To this end, nitrate (NO3-N) and total Kjeldahl nitrogen (TKN) concentrations were monitored at a high temporal resolution during 102 runoff events over a 6-year period. For each of the selected runoff events, CâQ response was examined visually for the presence and direction of hysteresis loops and classified into three types of responses, namely clockwise, counterclockwise, and no hysteresis. Changes in concentration
(ÎC) and the hysteresis direction (ÎR) were used to quantify nitrogen (NO3- and TKN) patterns during the runoff events. The transport mechanisms varied between compounds. The most frequent hysteretic response for NO3- was counterclockwise with enrichment. On the contrary, the main TKN dynamic was enrichment with clockwise hysteresis. Event characteristics, such as rainfall amount, peak discharge (i.e., maximum discharge of the runoff event), and event magnitude relative to the initial baseflow (i.e., the difference between the maximum discharge of the runoff event and the initial baseflow divided by initial baseflow) provided a better explanation for hysteresis direction and magnitude for TKN than antecedent conditions (antecedent precipitation and baseflow at the beginning of the event). For NO3- hysteresis, the role of hydrometeorological conditions was more complex. The NO3- hysteresis magnitude was related to the magnitude of the event relative to the initial baseflow and the time elapsed since a preceding runoff event. These findings could be used as a reference for the development of N mitigation strategy in the region.</p
Distribution and Origin of Iron Oxides in Soils over Limestone
[Resumen] Se pretende conocer la distribuci6n y el origen de los compuestos de hierro en suelos formados sobre calizas en Galicia. Predominan las formas minerales de hierro, encontrando en la fracciĂłn arena magnetita, goethita y/o hematites y excepcionalmente ilmenita, que se consideran heredadas del material de partida. En lĂĄmina delgada se observaron goethita y hematites como granos aislados, constituyendo nĂłdulos e integrados en fragmentos de caliza. En la arcilla, trazas de goethita estĂĄn presentes en casi todos los perfiles; s610 en uno de ellos la hematites es el Ășnico 6xido de hierro. La goethita puede haberse formado tanto por neoformaci6n como por microdivisi6n a partir de las fracciones gruesas, siendo este Ășltimo fen6meno el que ha originado la hematites de la fracci6n arcilla. En dos perfiles la goethita va acompañada de magnetita y se discute la posible existencĂa y formaci6n de maghemita.[Abstract] Iron distribution in soils formed over limestone of Galicia is studied an the origin
of the different iron forms is established. Organic iron is very scarce and mineral iron components dominate. Magnetite, goethite and / or hematite, less cornmonly ilmenite, are found in the sand fraction; they are considered as interited from the parent material. In polished sections goethite an hematite appear as single grains, nodules and il1corporated into limestone fragments. In the clay fraction, traces of goethite are present in aH except one of the profiles where only traces of hematite are indentified. Neoformation and microdivision from coarse fractions can act in the genesis of goethite; only microdivision is considered as the origin of hematite. Magnetite accompanies goethite in two profiles; the possible presence of maghemite and its origin is also discusse
Observation of the Crab Nebula with the HAWC Gamma-Ray Observatory
The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been
used for the past 25 years as a reference source in TeV astronomy, for
calibration and verification of new TeV instruments. The High Altitude Water
Cherenkov Observatory (HAWC), completed in early 2015, has been used to observe
the Crab Nebula at high significance across nearly the full spectrum of
energies to which HAWC is sensitive. HAWC is unique for its wide field-of-view,
nearly 2 sr at any instant, and its high-energy reach, up to 100 TeV. HAWC's
sensitivity improves with the gamma-ray energy. Above 1 TeV the
sensitivity is driven by the best background rejection and angular resolution
ever achieved for a wide-field ground array.
We present a time-integrated analysis of the Crab using 507 live days of HAWC
data from 2014 November to 2016 June. The spectrum of the Crab is fit to a
function of the form . The data is well-fit with values of
, , and
log when
is fixed at 7 TeV and the fit applies between 1 and 37 TeV. Study of the
systematic errors in this HAWC measurement is discussed and estimated to be
50\% in the photon flux between 1 and 37 TeV.
Confirmation of the Crab flux serves to establish the HAWC instrument's
sensitivity for surveys of the sky. The HAWC survey will exceed sensitivity of
current-generation observatories and open a new view of 2/3 of the sky above 10
TeV.Comment: Submitted 2017/01/06 to the Astrophysical Journa
All-particle cosmic ray energy spectrum measured by the HAWC experiment from 10 to 500 TeV
We report on the measurement of the all-particle cosmic ray energy spectrum
with the High Altitude Water Cherenkov (HAWC) Observatory in the energy range
10 to 500 TeV. HAWC is a ground based air-shower array deployed on the slopes
of Volcan Sierra Negra in the state of Puebla, Mexico, and is sensitive to
gamma rays and cosmic rays at TeV energies. The data used in this work were
taken from 234 days between June 2016 to February 2017. The primary cosmic-ray
energy is determined with a maximum likelihood approach using the particle
density as a function of distance to the shower core. Introducing quality cuts
to isolate events with shower cores landing on the array, the reconstructed
energy distribution is unfolded iteratively. The measured all-particle spectrum
is consistent with a broken power law with an index of prior to
a break at ) TeV, followed by an index of . The
spectrum also respresents a single measurement that spans the energy range
between direct detection and ground based experiments. As a verification of the
detector response, the energy scale and angular resolution are validated by
observation of the cosmic ray Moon shadow's dependence on energy.Comment: 16 pages, 11 figures, 4 tables, submission to Physical Review
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