Three numerical indexes, based on soil enzyme activities, which can discriminate between altered and unaltered soils, are presented and validated. Seven enzymes were measured at three different agricultural sites subjected to contamination by municipal and industrial wastes (site 1), intensive cultivation without either crop rotation or organic fertilization (site 2), and irrigation with brackish water (site 3). At each site neighbouring, unaltered soils were sampled and analysed as control soils.The three indexes were developed by means of canonical discriminant analysis (CDA) using data from two sites, while the third site was kept aside as an independent test. The first index is built up using all of the enzyme activities studied; the second, using the most discriminating enzyme activities only; and the third was developed for testing against data in published papers that deal with enzyme measurements in soils under different management regimes.The three indexes were able to discriminate between altered and control soils when applied to the data set from the third site, i.e., that not used for index development. When tested against published data, the third index was usually able to discriminate altered soils from controls by higher index scores. This index was successful in most cases: it was consistently able to classify soils according to their reported degree of alteration. Our results confirm that enzyme activities are suitable indicators of soil alteration and may be usefully integrated to develop soil alteration indexes suitable for monitoring soil status under different conditions. 相似文献
Background, Aim and Scope
Contamination of soils does not only occur on their surface over large areas, but also in depth. Therefore a characterization
of soil state after pollution demands a three-dimensional soil sampling, by what a large number of samples has to be analyzed.
Analytical results could be evaluated by multivariate statistical methods, which have already been used for the evaluation
of data sets containing results from soil sampling of two dimensions like areas or single profiles. In this case study, multivariate
statistical methods were applied to investigate structure and interactions between features in a data set containing results
of three-dimensional soil sampling. The investigated soil profiles were contaminated by emissions of a former cement and phosphate
fertilizer plant. The aim of this study was to determine the remaining extent of contamination and to analyze whether pollutants
are mobilized and vertically transported within the profiles.
Materials and Methods:
Three soil profiles were sampled in the surroundings of the plant. Grain size, organic and carbonatic bonded carbon, pH value,
and the total contents of Ca, Cd, Co, Cu, F, Fe, K, Mn, Mg, Na, Ni, P, Pb, and Zn were determined. The resulting data set
was evaluated by cluster analysis, linear discriminant analysis, and principal components analysis. The sequential extraction
procedure according to Zeien and Brümmer was applied to analyze the binding properties of Ca, Cd, Cu, Na, Pb, and Zn from
selected samples.
Results:
Cd was identified as contaminant of the top soils. The pH values of the bottom soils were determined to be in alkaline range,
which is unnaturally high. Variables were clustered according to enrichment of variables in top soils. The samples were classified
regarding their pollution state and their substrate by cluster analysis, which was confirmed by linear discriminant analysis.
Geogenic and anthropogenic sources of variables as well as relationships between variables like the binding of heavy metals
at organic matter were detected by using principal components analysis. The binding of heavy metals at organic matter in the
top soils was confirmed by the results of the applied sequential extraction. A vertically altered distribution of Na binding
was determined.
Discussion:
According to the current soil conditions, the uptake of heavy metals had probably occurred by the over ground part of plants
during the deposition. The distribution of Na should likely result from the vertical transport of Na, which would also explain
the high pH values of the bottom soils by ion exchange. Altogether, the main amount of deposited Ca, F, Na, P, and heavy metals
is likely nearly insoluble bound in the top soils.
Conclusions:
Ten years after the end of production, the pollution of top soils in the surroundings of the former plant is still high. However,
regarding the ecotoxicological relevance the now explored interactions between several soil features and elements strongly
indicate that there is no short-term to medium-term risk of a mobilization of the deposited elements with the exception of
Na.
Recommendations and Perspectives:
The results of this case study prove that multivariate statistical methods are powerful tools to explore interactions of variables
and relationships in a data set derived from three dimensional soil sampling. The methods applied in this work can be highly
recommended for evaluations of large data sets resulting from two- or three-dimensional samplings. Multivariate statistical
methods enable the characterization of soils and their pollution state in a simple and economic way. 相似文献
Bacteriological status, somatic cell counts and proportions of lymphocytes, granulocytes and monocytes were determined in 1,659 quarter milk samples from 39 dairy cows. Discriminant analysis was performed in order to assess the ability of total and differential somatic cell counts and combinations of total somatic cell count and each of the differential cell counts, to discriminate between infected and pathogen-free quarters, as well as between quarters infected with minor pathogens and quarters infected with major pathogens. Total somatic cell count classified 82.9% of all quarters correctly with respect to bacteriological status. Differential somatic cell count was less effective than total somatic cell count in discriminating between infected and pathogen-free quarters, as well as between quarters infected with minor vs. major pathogens. Combination of total and differential somatic cell counts did not improve the rate of correctly classified quarters. Inclusion of demographic data into the discriminant function increased the number of quarters correctly classified, mainly through an increase in the proportion of correctly classified infected quarters. 相似文献
Our aim was to assess the seroprevalence of Chlamydophila (Cd) abortus (Chlamydia psittaci serotype 1), denoted ovine enzootic abortion (OEA), in the Swiss sheep population. A competitive enzyme-linked immunosorbent assay (cELISA) was adapted for the investigation of pooled serum samples (pool approach) and receiver-operator characteristic (ROC) analysis was applied to define the cut-off of the pool approach. At a cut-off value of 30% inhibition, the flock-level pooled sensitivity and specificity were 92.9% and 97.6% when compared to classifying the flock based on individual-animal samples.
Subsequently, sera from 775 randomly selected flocks out of 11 cantons of Switzerland were investigated using the pool approach. The cantons included in the study represented 72% of the Swiss sheep flocks and 76% of Swiss sheep population. Antibodies against Cd. abortus were found in almost 19% (144) of the 775 examined sheep flocks. Test prevalences were adjusted for the imperfect test characteristics using the Rogan–Gladen estimator and Bayesian inference. Seroprevalence was highest (43%) in the canton Graubünden. In the remaining 10 cantons the seroprevalence ranged from 2 to 29%. The cELISA in combination with testing pooled sera and statistical methods for true prevalence estimation provided a good survey tool at lower costs and time when compared to other approaches. 相似文献
In veterinary practice the clinician often evaluates and predicts herd health status over time according to clinical criteria. In this paper, we modeled three different clinical signs among pigs based on longitudinal clinical observations in 15 pig herds. We compared and discussed the outputs from two different approaches for making clinical forecasts in a herd: a naive approach using a simple time series model with previous disease observations as predictors and a Bayesian state space models approach, in which the time lag variable entered into the random component of the model. We used the Markov chain Monte Carlo technique to calculate posterior distributions of the forecasts. For the herd specific forecasts the results showed that there were only minor differences between the forecasts from the simple time series model and the median forecasts from the Bayesian model. However, the credibility intervals from the Bayesian model were wider than the forecasts from the simple model and, therefore the Bayesian model encompassed the variability in the forecasts better. Compared to the statistical model, the simple time series would be easier to implement in a practical setting. However, the latter lacks the inherent “generality” from the statistical model that allows the user to make statements about the distribution of the herds and to predict disease status based on the “average” correlation among the herds. The applicability of the Bayesian approach within a clinical decision-making framework was discussed, with special emphasis on the use of prior information and clinical forecasting. 相似文献