Transformations and availability of phosphorus in three contrasting soil types from native and farming systems: A study using fractionation and isotopic labeling techniques

Background, aim, and scope  

Despite the contribution of many sequential P fractionation schemes to the study of P transformations in agricultural soils, the nature of P in each fraction remains qualitative rather than mechanistic. This study used the sequential extraction and isotopic dilution techniques to assess the recovery of a tracer (³²P) in soil P fractions and to elucidate the transformation of soil P in different P pools and its lability.     

Geochemical studies on the contamination and dispersion of trace metals in intertidal sediments around a military air weapons shooting range

Purpose  

A number of publications have raised trace metal contamination of soils and sediments within and around shooting ranges used for sport or military training. To our knowledge, however, there is no publication on the contamination of sediments derived from military shooting ranges in a marine environment. Therefore, this work was purposed to assess the dispersion and fractionation of ammunition- and bomb-derived trace metals in intertidal sediment.     

Applicability of a sequential P fractionation procedure to Si in sediment

Purpose  

A sequential phosphorus (P) fractionation procedure for sediments was applied to silicon (Si) to test its applicability. We wanted to know (1) whether it would be used in a cost-efficient way to study the finding of both elements, defining Si pools corresponding to the respective P pools, and in particular, (2) whether it could be shown that redox-sensitive processes affect Si mobility in sediment.     

Proposal of a simple screening method for a rapid preliminary evaluation of “heavy metals” mobility in soils of contaminated sites

Purpose  

Risks associated to “heavy metals” (HM) soil contamination depend not only on their total content but, mostly, on their mobility. Many extraction procedures have been developed to evaluate HM mobility in contaminated soils, but they are generally time consuming (especially the sequential extraction procedures (SEPs)) and consequently applicable on a limited number of samples. For this reason, a simple screening method, applicable even “in field”, has been proposed in order to obtain a rapid evaluation of HM mobility in polluted soils, mainly focused on the fraction associated to Fe and Mn oxide/hydroxides.     

Flooding-enhanced immobilization effect of sepiolite on cadmium in paddy soil

Purpose  

Little is known of the effect of sepiolite on the transformation of Cd in anthropogenically contaminated paddy soil under different moisture conditions; therefore, we studied the effects of sepiolite and flooding on the extractability and fractionation of Cd in paddy soils.     

Comparison of five methods to determine the cation exchange capacity of soil

Background

Cation exchange capacity (CEC) is a routinely measured soil fertility indicator. The standard NH₄OAc (pH 7) extraction procedure is time-consuming and overestimates actual CEC values of variable charge soils. Unbuffered extractants have been developed to measure the effective CEC (eCEC), but they differ in the type of index cation and extraction procedures.

Aim

This study was set up to systematically compare CEC values and exchangeable cation concentrations among different procedures and evaluate their practical aspects.

Methods

Five procedures were compared for (e)CEC, that is, silver thiourea (AgTU), cobalt(III) hexamine (Cohex), compulsive exchange (CE, i.e., BaCl₂/MgSO₄), BaCl₂ (sum of cations in single-extract), and NH₄OAc (pH 7). We applied these methods to a set of 25 samples of clay minerals, peat, or samples from soils with contrasting properties.

Results

The CEC values correlated well among methods (R² = 0.92–0.98). Median ratios of eCEC (AgTU as well as CE) to the corresponding eCEC (Cohex) value were 1.0, showing good agreement between eCEC methods, but NH₄OAc exceeded Cohex values (ratios up to 2.5 in acid soil). For BaCl₂-extracteable cations, the ratio ranged from low (<1.0) in acid soils (acid cations not measured) to high (>1.0) in high-pH soil (dissolution of carbonates). Multiple-extraction methods (CE and NH₄OAc) yielded more variation and increased labor.

Conclusions

The chemical properties of the sample cause method-specific interactions with chemical components of extractants. We found the Cohex method with ICP-MS detection to be the most efficient and cost-effective technique for determination of eCEC and exchangeable cations.     

Faba bean (Vicia faba L.) varieties reveal substantial and contrasting organic phosphorus use efficiencies (PoUE) under symbiotic conditions

Background

The excessive use of inorganic P (Pi) in soils is alarming as it is causing numerous environmental problems and may lead to the depletion of rock phosphate reserves earlier than expected. Hence, to limit the over-dependence on Pi, there is the need to investigate organic phosphorus (Po), which is the dominant P form of soil P pool, as an alternate P source for plant growth.

Aim

The present study seeks to investigate organic P use efficiency of eight varieties of faba bean grown symbiotically.

Methods

The plants were grown in pots (6 kg soil) under greenhouse condition with three P source, namely, phytic acid (organic P, Po), KH₂PO₄ (inorganic P, Pi), and no-P. The P was applied at the rate of 1.79 g kg⁻¹ soil.

Results

The plants grown with Po and Pi produced similar amounts of root, shoot, and total dry matters. Despite producing statistically similar dry matters, P uptake by Pi-fertilized plants was twofold higher than by Po-fertilized plants. Meanwhile, Pi differed significantly from Po in terms of nodulation characteristics such as nodule dry biomass and individual nodule dry biomass. However, Po varied significantly from Pi in P utilization and acquisition efficiencies. Principal component analysis of Pi and Po revealed no significant variation and close association, confirming the nonsignificant differences between the two P treatments. Among the varieties tested, Tiffany tended to accumulate more dry matter, coupled with highest organic P utilization efficiency (0.48 g mg⁻¹) as well as the highest organic P beneficiary factor (80%).

Conclusion

These results provide a solid basis for further comparisons at physiological, biochemical, and molecular levels between Tiffany (Po-efficient) and Fuego (Po-inefficient) varieties, offering deep insights into and making it easier to understand the mechanisms that allow soil Po to be utilized under symbiotic conditions.     

Dynamic interactions between cohesive sediment tracers and natural mud

Purpose  

Cohesive sediment tracers have been developed to improve our understanding of fine sediment transport in the aquatic environment. However, there is little understanding of their physical and dynamic characteristics compared to the natural sediments they are intended to mimic. This work focuses on a labelled clay mineral tracer examining its dynamic characteristics and determining whether it flocculates and interacts with natural estuarine mud.     

Characterizing deep soils from an impacted subtropical isolated wetland: implications for phosphorus storage

Purpose  

Soils within the Lake Okeechobee drainage basin, FL, USA, have been impacted by beef cattle and dairy operations and the landscape ditched and drained to facilitate stocking and grazing pastures. Restoring wetlands located on pastures has been proposed to reduce overland loss of phosphorus (P) by retaining it within the soils. However, soil properties of deeper horizons within impacted wetlands are rarely investigated due to the assumption that most dominant biogeochemical interactions occur at the soil–water interface. In this paper, we investigate soil properties up to 160 cm below the surface from an impacted isolated wetland and its surrounding upland pasture.     

X-ray fluorescence spectrometry-based approach to precision management of bioavailable phosphorus in soil environments

Purpose  

Managing declining nutrient use efficiency in crop production has been a global priority to maintain high agricultural productivity with finite non-renewable nutrient resources, in particular phosphorus (P). Rapid spectroscopic methods increase measurement density of soil nutrients and improve the accuracy of rates of additional P inputs.     

A new sediment contact assay to assess particle-bound pollutants using zebrafish (<Emphasis Type="Italic">danio rerio</Emphasis>) embryos

Goal, Scope and Background  

Based on a bioassay battery covering only primary producers and consumers as well as degraders, the potential ecological hazard of sediments to vertebrates cannot be estimated comprehensively. Therefore, there is an urgent need to develop and standardize integrated vertebrate-based test systems for sediment investigation strategies. Whereas vertebrate-based in vitro systems have frequently been used for the investigation of aqueous samples, there is a significant lack of whole sediment assays. Thus, the purpose of the present study was: (1) to develop a rapid and reliable, but comprehensive method to investigate native sediments and particulate matters without preceding extraction procedures; (2) to compare the hazard potential of solid phase sediments to the effects of corresponding pore waters and organic extracts in order to characterize the bioavailability of the particle-bound pollutants; and (3) to relatively evaluate the embryotoxic effects of sediments from the catchment areas of the rivers Rhine, Neckar and Danube.     

Phosphorus transfer across boundaries: from basin soils to river bed sediments

Purpose  

The study of phosphorus (P) transfer from soils to rivers is a subject of interest as there is a clear relation between land use and water quality. P transfer in the soil/sediment system was evaluated by comparing the concentrations of total (P_T) and bioavailable P (P_A).     

Influence of incubation time on phosphorus sorption dynamics in lake sediments

Purpose  

Estimating phosphorus (P) sorption is generally achieved by measuring a decrease in P concentration over a defined period. However, information within the literature has not been able to be widely applied, probably due to the variability in incubation periods and initial P concentrations in reported experiments. The objective of this study was to investigate whether variations in incubation time and initial P concentration might result in differences in measured levels of P sorption in sediments.     

Endocrine disruption in a terrestrial isopod under exposure to bisphenol A and vinclozolin

Background, aim, and scope  

In the past decade there has been an increasing awareness about the possible consequences of human and wildlife exposure to endocrine disrupting compounds (EDCs). Bisphenol A (BPA) and vinclozolin (Vz) are EDCs which impacts on vertebrates have been largely investigated. Nevertheless, research on invertebrate effects, especially on soil organisms, are still largely under-represented. This work aims to extend the limited ecotoxicological datasets available and to provide tools to assess the effects of EDCs on the terrestrial species, using Porcellio scaber (Crustacea: Isopoda) as a model organism.     

Single-step chemical extraction procedures and chemometrics for assessment of heavy metal behaviour in sediment samples from the Bahía Blanca estuary,Argentina

Purpose  

The objective of this research was to study heavy metal mobility and availability in sediment samples. A rapid diagnosis about metal behaviour was performed using the combination of several single-step extraction procedures and multi-way chemometric tools.     

Comparison of soil phosphorus extraction methods regarding their suitability for organic farming systems

Background

Organic farmers frequently report sufficient yield levels despite low or even very low soil phosphorous (P) contents questioning the applicability of widely used laboratory methods for soil P testing for organic farming.

Aims

The aim of this study was to compare the validity of a broad range of different soil extraction methods on soils under organic management from South West Germany and to test the correlation of the measured soil P concentration with plant offtake.

Methods

Twenty-two soil samples of eight different organic farms were extracted with different solutions: (1) water, (2) CAL, (3) Olsen, (4) Mehlich 3, (5) Bray P1, (6) Bray P2, (7) NaOH+Na₂EDTA, and (8) total P. The results were then correlated with above ground plant P.

Results

Spearman's rank correlation coefficient (r_s) of correlations between above ground plant P and extractable soil P (Water-P, CAL-P, and Olsen-P [+active charcoal {+AC}]) determined with ICP-OES were strong (0.94, 0.90, and 0.93, respectively). Among the tested methods, above ground plant P showed a strong correlation with CAL-P as detected by ICP-OES (r_s = 0.90) and colorimetry (r_s = 0.91). The comparison of CAL-P data provided by farmers and CAL-P analyzed during this research showed discrepancies between the results.

Conclusions

The results of this study indicate that the CAL method can be used in organic farming despite a low extraction of organic P (P_org). Furthermore, it is recommended for farmers to take soil samples for analyses regularly and interpret changes in P in the long-term instead of interpreting individual samples.     

Assessing chromate availability in tropical ultramafic soils using isotopic exchange kinetics

Background, aim, and scope  

The presence of labile chromate in the soils is an environmental problem because of its high toxicity. The isotopic exchange kinetics (IEK) methods have been shown to be a useful tool to measure the phytoavailability of major (P, K) and trace elements (Cd, Zn, Ni, Pb) in soils. This study focused on the potential of applying IEK for chromate to characterize its availability in two tropical ultramafic Ferralsols.     

Organic and inorganic phosphate interactions with soil hydroxy-interlayered minerals

Background  

Even though extensive work has been done on P interactions with free Al- and Fe-hydroxide minerals, limited or no information exists on sorption/desorption processes of organic and inorganic phosphate forms with soil hydroxy-interlayered minerals.     

Lead,Zn, and Cd in slags,stream sediments,and soils in an abandoned Zn smelting region,southwest of China,and Pb and S isotopes as source tracers

Purpose  

Smelting activity produced tons of slags with large quantities of highly toxic metals, resulting in contamination in adjacent soils and sediments as well. This study investigated the fractionation and sources of metals Pb, Zn, and Cd in polluted soils and sediments in a region with once prosperous Zn smelting activities in southwestern China. Soils with varying land uses were of a special concern due to their connection to the food chain. Obtained data would offer a valuable reference to the development of land-use management strategy in this region.     

Ecotoxicological assessment of road runoff residues for aquatic surface ecosystems in a scenario of reuse

Purpose  

Road runoff residues are often reused in road and civil works building. Although the physicochemical and ecotoxicological characteristics of these materials are known, no extensive ecotoxicological studies have been carried out on the leachates obtained from these residues once they have been spread and exposed to rainfall. This study was aimed at assessing the ecotoxicological risks for lentic aquatic ecosystems receiving the leachates of road runoff residues, either raw or treated, through granulometric sieving.