Salinization,alkalinization and sodification in Punjab (Pakistan): characterization of the geochemical and physical processes of degradation

Evidence of soil degradation impeding soil tillage and irrigation in cultivated soils in Pakistan is identified, described and represented in a general process of degradation. Based on a chemical analysis of soil characteristics, it is shown that a more general geochemical degradation process may occur in these soils. Two paths of salinization, i.e. neutral salinization and alkalinization inducing a process of sodification, are identified. The wide range of chemical properties of soils and corresponding geochemical processes can be explained by the great diversity of quality in irrigation water that is taken either from the canal or from the groundwater. The basic module of a geochemical model AQUA (Vallès and DeCockborne, 1992) is calibrated with the help of a study of the soil geochemical properties (identification of minerals, characterization of exchanges) and then used to assess the effect of four different water qualities on sandy and loamy soils. Based on these scenarios, the salinity, alkalinity and sodicity hazard of irrigation water is assessed by taking into account simultaneously the electrical conductivity and the residual alkalinity (calcite-residual alkalinity, residual sodium carbonates) or irrigation water and the soil cation exchange capacity: these three indicators appear the most relevant in the context of the study. Copyright © 1999 John Wiley & Sons, Ltd.     

Assessment of the soil phosphorus–mobilization potential by microbial reduction using the Fe(III)‐reduction test

The mobility of soil P is greatly influenced by the redox potential (Eh), which depends on the reducing activity of soil microorganisms. Standard extraction methods for the determination of the mobile soil P disregard the P mobilization caused by the influence of microorganisms on Eh, while P test methods that include soil microbial activities are lacking. Thus, the Fe(III)‐reduction test was investigated for its suitability to determine the P fraction that is mobilized in soil under reducing conditions (P_Red). In this test, the soil‐microbial reducing activity is measured from the microbial Fe(III) reduction combining a bioassay with 7 d incubation and a chemical extraction using 1M KCl. After the incubation, Eh in 26 different soil samples ranged from –282 to –123 mV. The concentration of P_Red in the soil samples ranged from concentrations below the limit of detection to 84.9 mg kg^–1 and was on average of all soil samples by a factor of 2.4 to 18 smaller than the P fractions determined by standard soil P–extraction methods. As standard agronomic and environmental P extractants, respectively, water (P_H2O), dithionite citrate bicarbonate (P_Dith), ammonium oxalate (P_Ox), ammonium lactate (P_AL), double lactate (P_DL), and sodium bicarbonate (P_Olsen) were selected. The P_Red fraction was not correlated with P_AL, P_DL, P_olsen, and the degree of P saturation, but with P_H2O (r = 0.43*), P_Dith (r = 0.60***), and P_Ox (r = 0.61***). Furthermore, P_Red depended on the concentration of amorphous Fe oxides (Fe_Ox, r = 0.53**) and was closely correlated with the concentration of microbially reduced Fe (Fe_Red, r = 0.94***). This indicated the influence of the Fe(III)‐reducing activity of soil microorganisms on P mobilization. In subsoils, low in Fe(III)‐reducing activity, no P was released by the Fe(III)‐reduction test, which was in contrast to the results from the other chemical extraction methods. Additional alterations of the microbial activity by inhibiting and activating amendments, respectively, clearly affected the microbial Fe(III)‐reducing activity and the associated release of P_Red. Thus, P_Red, determined by the Fe(III)‐reduction test, might be termed as the fraction that is potentially released from soil by microbial reduction.     

A Chronic Plant Test for the Assessment of Contaminated Soils. Part 1: Method development (9 pp)

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PREAMBLE According to the German Federal Soil Protection Act (BBodSchG 1998), the habitat function of soils must be protected. Despite the fact that in the Federal Soil Protection Ordinance (BBodSchV 1999) it has not been established how this goal can be reached reliably, it is clear that such a biological function can only adequately be assessed using biological test methods. This is especially true when a soil is contaminated by a mixture of often unknown chemicals. In such a case the use of chemical analysis aiming at a small range of known substances is not sufficient and must therefore be supplemented by biological methods. For this reason, several standardised test methods are available (e.g. using earthworms, collembolans or plants; Römbke and Knacker 2003; ISO 2003). Since acute tests are usually not sensitive enough for the assessment of potentially contaminated soils (e.g. Hund-Rinke et al. 2002), chronic tests like the earthworm reproduction tests (ISO 1998) are recommended for this purpose.

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A chronic plant test for the determination of phytotoxicity was missing until quite recently. The term phytotoxicity is understood here as the capacity of a compound or a contaminated soil to cause temporary or long-lasting damage to plants (EPPO 1997). Therefore, the German Ministry for Education and Research sponsored a project (1997 – 1999) in which – based on existing standardised methods – such a chronic plant laboratory test was developed and partly validated (Kalsch and Römbke 2000). The new test can be used for the evaluation of single chemicals (see Part 1 of this mini-series) as well as for the assessment of contaminated or remediated soils (see Part 2 of this mini-series).

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ABSTRACT Background and Scope. As part of the efforts to improve the biological testing of contaminated soils, the German government sponsored the standardisation of a chronic plant bioassay. This new test is based on experiences with various acute plant tests (e.g. published by OECD or ISO) and existing North American Plant-Life-Cycle Bioassays. In this contribution the characteristic properties of the test are described.

Methods

The test can be performed either with Brassica rapa (turnip) or Avena sativa (oat). Its duration is 35 to 64 days with OECD artificial soil and a German standard field soil acting as controls. Water and nutrients are provided by an automatic wick irrigation system. Besides measuring biomass and shoot length, the number of pods, seeds and flowers are applied as chronic measurement endpoints. During the development of the test, TNT (2,4,6-trinitrotoluene) and Pyrene were used as model test substances.

Results

Pyrene did not affect B. rapa (turnip) in concentrations of up to 10.000 mg/kg soil (due to the often low sensitivity of A. sativa (oat) no further test with this substance was performed). Depending on the endpoint the results varied in the tests with TNT. With few exceptions, the NOEC (No Observed Effect Concentration) values were determined as 55.5 mg TNT/kg soil for B. rapa (turnip) and as 75 (unfertilised) and 150 (fertilised) mg TNT/kg soil for A. sativa (oat). The EC50-values varied between 96.3 and 207.2 mg TNT/kg soil for B. rapa (turnip) and 183.1 – 505.6 mg TNT/kg soil for A. sativa (oat), depending on the endpoint.

Outlook

The results of this work have been used to prepare a draft test guideline, which has recently been standardised by the International Organisation for Standardisation (ISO). Practical experiences with this test system are described in Part II of this mini series.     

Adsorption of glycerophosphate on goethite (α‐FeOOH): A macroscopic and infrared spectroscopic study

Adsorption, desorption, and precipitation reactions at environmental interfaces govern the bioavailability, mobility, and fate of organic phosphates in terrestrial and aquatic environments. Glycerophosphate (GP) is a common environmental organic phosphate, however, surface adsorption reactions of GP on soil minerals have not been well understood. The adsorption characteristics of GP on goethite were studied using batch adsorption experiments, zeta (ζ) potential measurements, and in situ attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR). GP exhibited fast initial adsorption kinetics on goethite, followed by a slow adsorption. The maximum adsorption densities of GP on goethite were 2.00, 1.95, and 1.44 μmol m^?2 at pH 3, 5, and 7, respectively. Batch experiments showed decreased adsorption of GP with increasing pH from 3 to 10. Zeta potential measurements showed a remarkable decrease in the goethite isoelectric point upon GP adsorption (from 9.2 to 5.5), suggesting the formation of inner‐sphere surface complexes. In addition, the ATR‐FTIR spectra of GP sorbed on goethite were different from those of free GP at various pH values. These results suggested that GP was bound to goethite through the phosphate group by forming inner‐sphere surface complexes.     

The Monitoring of Cr(III) and Cr(VI) in Natural Water and Synthetic Solutions: An Assessment of the Performance of the Dgt and Dpc Methods

The technique of diffusive gradients in thin films or diffusive gradient in thin films (DGT) has been used in this work for the in situ measurement of labile Cr(III) and Cr(VI) species. Direct measurement of Cr(VI) was also carried out in parallel with a field-based colourimetric technique based on the EPA 7196 diphenyl-carbohydrazide (DPC) method. The efficiency of the DGT and DPC methods were tested (a) in the laboratory, using synthetic solutions in the presence of realistic concentrations of Cr, humic substances (HS), and ethylenediaminetetraacetic acid (EDTA), and (b) in the field, in river water affected by effluents discharged by the tannery industry. The main advantage of the DGT method is that it allows the in situ separation of labile species of Cr(III) and Cr(VI), though there are still uncertainties about its performance in field conditions. The DPC method proved to be a fast, accurate, and relatively economical option for the field-based determination of Cr(VI). Sample acidification and ageing of unacidified samples from contaminated aquatic environments, produced significant errors in the determination of ‘dissolved’ Cr. The concentration of Cr(VI) determined by either the DGT or the DPC method exceeds recommended international guidelines.     

Characterization of the porous structure of soils: adsorption of nitrogen (77 K) and carbon dioxide (273 K), and mercury porosimetry

Accessibility of adsorbates to internal active sites of soils depends mainly on the porous structure of the material. We aimed to determine the distribution of pore sizes in soils with varied physico-chemical properties, by combining adsorption of gases and mercury porosimetry. Microporosity was studied by physical adsorption of N₂ at 77 K and CO₂ at 273 K; mercury intrusion porosimetry allowed us to evaluate the macroporosity; and mesoporosity was determined by capillary condensation of N₂ and mercury porosimetry. The soils investigated were essentially macroporous, with volumes between 0.33 and 0.73 cm³ g^–1; the maxima in the differential pore-size distribution were in the range 1500–4000 nm. Volumes of meso- or micropores were always less than 10% of macropore volumes. Calculations based on the theory of Dubinin and the α_s-method (for N₂ at 77 K) provided, generally, coincident results. In a soil containing much organic matter, N₂ adsorption was only one-ninth that of CO₂ adsorption, showing that N₂ adsorption into the narrow micropores of organic matter was kinetically restricted. When accessibility to micropores was not restricted, the total volume of micropores could be deduced from N₂ adsorption, whereas CO₂ measured exclusively the narrowest microporosity.     

How to characterize ‘good’ and ‘greening’ in the EU Common Agricultural Policy (CAP): the case of clay soils in the Netherlands

The change in the Common Agricultural Policy (CAP) of the European Union from product to producer support, including requirements for ‘good agricultural and environmental conditions’ and ‘greening’, is excellent. However, these requirements are now defined in rather general terms. Questions can be raised about suitable indicators, and there is a recognized need for effective management recommendations to support farmers in achieving the required ‘good’ conditions. These recommendations are bound to be quite different for different soils in different countries. A study of Dutch clay soils was based on a storyline describing current problems and management options for improvement, which were quantified using a soil–water–crop simulation model. Indicators were defined for agricultural conditions and suggestions made for the use of the model in a predictive mode to help farmers improve their soil management. Environmental conditions were judged by current environmental guidelines for water and air. When modelling, implicit assumptions that soils are homogeneous were shown to be unrealistic for these clay soils, requiring development of innovative methods and procedures, presenting a challenge for soil research.     

An archaeopedological and phytolitarian study of the “Dark Earth” on the site of Rue de Dinant (Brussels, Belgium)

During the excavations of the site of Rue de Dinant in the historic centre of Brussels (Belgium), remains of the first city wall dating from the 13th century have been discovered. Intra muros thick dark sediment units predating this wall are observed. These dark units are among the oldest occupation traces so far encountered in this higher, eastern, part of the historic centre of Brussels. In order to characterise them, and to understand the human activities and natural processes behind their formation, an interdisciplinary research, integrating archaeopedology and phytolith study, has been undertaken. This approach permitted us to identify a range of natural and cultural processes leading to the formation of these dark layers, and to characterise different activities. Remains of a hearth, old plough land (cropfields) and grassland have been identified, all activities referring to a rural landscape organisation. Later on, the area changes into an enormous silt extraction area, whereby Dark Earth is thrown into the dug pits. Finally, the construction of the first city wall marks the area as becoming part of the city. The study of Dark Earth shows to be a potentially valuable tool to shed light on the development and spatial organisation of pre-urban Brussels, a historically very poorly documented period.     

Bioavailability of Metals at a Southeastern Brazilian Coastal Area of High Environmental Concern Under Anthropic Influence: Evaluation Using Transplanted Bivalves (<Emphasis Type="Italic">Nodipecten nodosus</Emphasis>) and the DGT Technique

Metals are commonly determined in aquatic organisms, primarily using bivalves to provide important data on their bioavailability. The technique of diffusive gradients in thin films (DGTs) has also been employed to assess the concentration of metals in freshwater and marine environments, determining their lability. The present work evaluated and compared the labile and bioavailable concentrations of Cd, Co, Cu, Mn, Ni and Pb in seawater from Ilha Grande Bay, RJ, using DGT and transplanted bivalves (Nodipecten nodosus), respectively. The scallops and DGTs were immersed in water at three sampling locations within the bay from July to September 2012 (winter campaign) and from December 2012 to February 2013 (summer campaign). The metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and optical emission spectrometry (ICP-OES). DGT technique was successfully used to determine the concentrations of metals in waters, except for Pb when short deployment times were used. All metals were determined using transplanted bivalves (N. nodosus), but pre-exposure to Cd was evident, which made the interpretation of the data for this analyte difficult. The data on metal lability in Ilha Grande Bay waters obtained from the DGT technique were correlated with the metal bioavailability determined in the soft tissues of the transplanted N. nodosus for Co, Cu, Mn, Ni and Pb. This is the first evaluation of this type for this area of high environmental concern. Both techniques revealed that Náutico was the location with the highest concentration of metals in the study area.     

Comparing Different Infiltration Methods of the HEC‐HMS Model: The Case Study of the Mésima Torrent (Southern Italy)

The Hydrologic Engineering Center – Hydrologic Modelling System (HEC‐HMS) model has been widely applied for estimating hydrological variables at event scale. The choice of the most suitable infiltration method simplifies model's applicability under different environmental conditions. A proper case study for evaluating the runoff prediction capability of HEC‐HMS by the available infiltration methods is the semi‐arid torrents typical of Southern Italy as they are small and intermittent water courses, often subject to high‐magnitude flash floods and erosive events. HEC‐HMS performance of the ‘SCS‐CN’, ‘Green‐Ampt’ and ‘Initial and Constant’ infiltration methods in predicting runoff volume and peak flow was evaluated at the outlet of the Mésima torrent, Calabria, Southern Italy. Fourteen rainfall–runoff events were simulated by HEC‐HMS and compared with the corresponding observations by a quantitative approach. A good accuracy in predicting runoff volume was achieved using the ‘SCS‐CN’ method after calibration of the initial curve numbers. Peak flow was better estimated using the ‘Initial and Constant’ method, also thanks to calibration of the ‘constant rate’ parameter. The calibrated hydrographs were very similar to the observations for both ‘SCS‐CN’ and ‘Initial and Constant’ methods. Adopting the ‘Green‐Ampt’ equations, however, showed low reliability. The evaluation of the time to flood peak was in some cases inadequate. Copyright © 2016 John Wiley & Sons, Ltd.     

Submicroscopic characterisation of phosphatic and sesquioxidic nodules of some soils of the “Chaco deprimido” (Argentina): Preliminary results

In this paper two examples are presented of the investigation by submicroscopic techniques, of particular problems in the characterisation and analysis of various pedological features in soils of the “Chaco Deprimido”.

The first concerns nodules seen in an alluvial soil. The techniques established their phosphatic composition and identified them as small bone fragments which are undergoing alteration.

The second relates to study of sesquioxidic nodules and cutans in solodised soils and planosols, and shows them to have a dominantly manganiferous composition; this result enables one to make certain interpretations concerning the physicochemical conditions essential for the formation of such pedological features.