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941.
Agricultural practices, hydrology, and water quality of the 267-km2 Big Spring groundwater drainage basin in Clayton County, Iowa, have been monitored since 1981. Land use is agricultural; nitrate-nitrogen
(-N) and herbicides are the resulting contaminants in groundwater and surface water. Ordovician Galena Group carbonate rocks
comprise the main aquifer in the basin. Recharge to this karstic aquifer is by infiltration, augmented by sinkhole-captured
runoff. Groundwater is discharged at Big Spring, where quantity and quality of the discharge are monitored.
Monitoring has shown a threefold increase in groundwater nitrate-N concentrations from the 1960s to the early 1980s. The nitrate-N
discharged from the basin typically is equivalent to over one-third of the nitrogen fertilizer applied, with larger losses
during wetter years. Atrazine is present in groundwater all year; however, contaminant concentrations in the groundwater respond
directly to recharge events, and unique chemical signatures of infiltration versus runoff recharge are detectable in the discharge
from Big Spring.
Education and demonstration efforts have reduced nitrogen fertilizer application rates by one-third since 1981. Relating declines
in nitrate and pesticide concentrations to inputs of nitrogen fertilizer and pesticides at Big Spring is problematic. Annual
recharge has varied five-fold during monitoring, overshadowing any water-quality improvements resulting from incrementally
decreased inputs.
Electronic Publication 相似文献
942.
Kozlov V. I. 《GeoJournal》1980,4(1):23-30
The paper deals with the processes of ethnic consolidation, ethnic and linguistic assimilation and inter-ethnic integration taking place in the USSR. The author shows the influence of consolidation and assimilation processes over the trends in the numerical strength of individual peoples and the resulting change in the country's ethnic composition as this is reflected in the Soviet population censuses of 1926, 1959, 1970, and 1979. 相似文献
943.
From the studies of ore deposit geologic settings,sulfur isotopes,lead isotopes,carbon isotopes and oxygen isotopes,fluid inclusions and petrochemistry in this paper,the authors have drawn a conclusion that the ore-forming hydrothermal solutions are the high-temperature magmatic hydrothermal solutions for the gold ore deposit,and at the same time,the involvemety of crustal materials can not be ruled out .It is the first time that the authors have proposed that the Laozuoshan gold-ploymetallic ore deposit in Heilongjiang Province was formed in the calc-alkaline series environment at the margin of an active continent. 相似文献
944.
1IntroductionLanmuchangite ,anewmineralTlAl[SO4]2 ·1 2H2 O ,occursintheoxidationzoneofrichthalli umorebodiesattheLanmuchangthallium(mercury)deposit.Itisnamedafterthelocalitywhereitwasdiscovered .InJune,2 0 0 1 ,themineralanditsnamewereapprovedbytheCommissiononNewMineralsandMineralNames,IMA .ItstypicalmaterialisdepositedattheGeologicalMuseumofChina ,Beijing .2OccurrenceandmineralassociationLanmuchangiteoccursintheoxidationzoneofrichthalliumorebodiesattheLanmuchangthal lium(mercury)or… 相似文献
945.
Ernst-Dieter Hornig 《Geotechnical and Geological Engineering》2010,28(3):233-240
Measured settlements of buildings on the weathered Keuper Marl appeared to be much smaller than calculated settlements, which
were based on stiffness modulus from standard oedometer tests. Therefore, both special triaxial K
0-tests and oedometer tests were carried out for an accurate determination of stiffness moduli. Modulus obtained in the triaxial
K
0-tests were at least two to three times the values obtained in the oedometer tests. To verify observations from the laboratory
tests, the loads and the settlements of two single footings on weathered Keuper mudstone have been measured during construction
of a building over 1 year. Also, a large scale footing load test with measurements of deformations were conducted on the weathered
Keuper mudstone. The measured settlements of the two single footings and the tested foundation were compared with the settlements
based on conventional calculations with moduli from oedometer tests and triaxial K
0-tests. Up to a foundation pressure of σv = 500 kN/m2 the calculated settlement based on E
S-modulus obtained from triaxial K
0-tests was found to correspond well to the measured deformation. For foundation pressure beyond 500 kN/m2, the foundation
response was highly non-linear and it could not be described any more with the linear-elastic model. Therefore the footing
load test was also simulated by FEM analyses. 相似文献
946.
A total of 42 samples of road dust were collected along ring road, city centre, city side, and freeway in Urumqi, China. Total
concentrations of Cd, Cr, Cu, Ni, Pb, Mn, Be, Co, Zn, and U were determined by using the inductively coupled plasma-mass spectrometry
in order to assess and to compare road dust contamination levels of metals among the four roads. The results show that, among
the four categories of roads, mean concentrations of Co and U vary little. City centre locations show strong enrichments of
Cd, Cu, Pb, and Be. Along the ring road, the highest mean concentrations were found for Cr, Ni, Mn, and Co. However, the highest
concentrations of Zn and U were found along the freeway. The cluster analysis shows that three main groups can be distinguished.
Every group may be associated with different main sources and concentrations of the metals. The results of contamination assessment
reveal that, among all of the potential toxic metals, Cd, Cu, and Zn pollution were obviously heavier with moderate or high
contamination indices for most road dust samples, while Cr, Ni, and Pb contamination were lower along the four categories
of roads. Compared with the city side, Cd, Cu, Pb, Ni, and Zn contamination were heavier along the ring road, the city centre,
and the freeway with high traffic density. Low Pb contamination or no contamination in all the road dust samples may be related
to the increasing usage of lead-free petrol. 相似文献
947.
Within the engineering profession and natural sciences, vulnerability is widely accepted to be defined as the degree of loss
(or damage) to a given element or set of elements within the area affected by a threat. The value of vulnerability is expressed
nondimensionally between 0 and 1. It is a fundamental component in the evaluation of landslide risk, and its accurate estimation
is essential in making a reasonable prediction of the landslide consequences. Obviously, vulnerability to landslides depends
not only on the characteristics of the element(s) at risk but also on the landslide intensity. This paper summarizes previous
research on vulnerability to landslides and proposes a new quantitative model for vulnerability of structures and persons
based on landslide intensity and resistance of exposed elements. In addition, an approximate function is suggested for estimating
the vulnerability of persons in structures. Different methods for estimating the vulnerability of various elements to slow
or rapid landslides are discussed. Finally, the application of the new model is illustrated through an example. 相似文献
948.
Role of selected riparian herbs in reducing soil erosion and nutrient loss under simulated rainfall 总被引:1,自引:2,他引:1
The native riparian herbs such as Leonotis nepetaefolia (L.) R. Br., Cassia tora L., Ageratum conyzoides L., Parthenium hysterophorus L. and Sida acuta burm f., dominant on the bank of River Damodar in Eastern Jharia Area, Dhanbad (India), were selected to assess experimentally
their quantitative role in conserving the soil and reducing water runoff and nutrient (N and P) losses. A total of 42.5 mm
simulated rainfall were applied at 30 cm h−1 rain intensity on both vegetated and bare plots. The collected runoff water and eroded soil from each plot were determined
in terms of soil, water and nutrient conservation value (CV). Among the vegetated plots, soil CV ranged from 30 to 85% and
water CV from 20 to 48%. Nutrient (N and P) CV varied from 22 to 65% for total-N, 48 to 80% for ammonia-N and 50 to 86% for
nitrate-N. CV for total-P varied from 40 to 62%, inorganic-P from 42 to 60% and organic-P from 20 to 58%. In a stepwise multiple
regression equation comprising four independent variables (canopy cover, litter mass, soil moisture and plant biomass), canopy
cover explained 70–88% (P < 0.01) of variability in conserving soil, water and nutrient. The losses through runoff water and eroded soil from vegetated
plots were found to be minimized to a great extent as compared to bare plots. The role of these species in maintaining the
texture and fertility status of riparian soil is discussed. 相似文献
949.
Jun-De Dong Yan-Ying Zhang Si Zhang You-Shao Wang Zhi-Hao Yang Mei-Lin Wu 《Environmental Earth Sciences》2010,60(8):1673-1682
A large data set obtained by a 1-year monthly determination of water quality from Sanya Bay, South China Sea, was treated
by three-way principal component analysis aimed at exploring the spatial and temporal patterns of water quality in Sanya Bay.
Tucker3 model of optimum complexity (2, 2, 1) explaining 33.18% of the data variance, allowed interpretation of the data information
in three modes. The model explained spatial and temporal variation trends in terms of water quality variables during the study
period. Water quality in sampling station (S2) Sanya River was mainly influenced by Sanya River, and water quality in other
stations (S1, S3–S10) were mainly influenced by the waters in South China Sea. The results delineated the mouth of Sanya River
as critical from pollution point of view. The dry season from October to the next April and rainy season from May to September
have different influences on water quality in Sanya Bay. The information extracted by the three-way models would be very useful
to regional agencies in developing a strategy to carry out scientific plans for resource use based on marine system functions. 相似文献
950.
The results of geotechnical explorations, engineering geological investigation (including laboratory and in situ tests) and
field observations have been used, along with borehole logging charts, to obtain the rock mass geotechnical data. Based on
the data, the rock mass along the Sabzkuh water conveyance tunnel route was classified by rock mass rating (RMR), Q-system
(Q), rock mass index (RMi) and geological strength index (GSI) (3 methods). A new series of correlations were established between
the systems based on the data collected from the study area. These relationships were then compared with those reported in
the literature, and two new relations were recommended. The classifications were utilized to calculate mechanical properties
(rock mass strength and deformation modulus) of the rock mass along the tunnel according to available empirical relations,
and to distinguish the upper-bound and lower-bound relations. 相似文献