Simplified performance assessment methodology for addressing soil quality of nature-based solutions

Journal of Soils and Sediments - In urban areas, soil functions are deeply impacted by all human activities, e.g., water infiltration, carbon storage, and chemical substances degradation potential....     

Evaluation of platinum distribution between different soil components

Purpose

More attention has been given to the determination of background levels of platinum group element (PGE) in an urban environment. But, few studies have been conducted for its environmental behaviour. The necessity to understand the PGE behaviour in environment increases due to the increase in platinum (Pt) emissions. The aim of the study is to evaluate the adsorption and the distribution of Pt within soil and sediment components. This study investigated the Pt adsorption on kaolinite, hematite and humic acid.

Materials and methods

A batch experiment was used to determine sorption of Pt. The experiments were carried out on the three solids and on two mixtures of iron oxide and kaolinite, with two ratios 25:75 and 75:25. An elemental distribution of Pt was determined on the mixtures iron oxide–kaolinite by micro-X-ray fluorescence.

Results and discussion

The highest concentrations of Pt were found on kaolinite, followed by hematite and humic acid. Kaolinite exhibited the highest adsorption capacity. The sorption capacity of both mixtures was lower than that of kaolinite and iron oxide. Moreover, the shape of isotherms, for both mixtures, tends towards that of kaolinite. The elemental distribution maps of mixtures showed, for both ratios, a high enrichment of kaolinite with Pt opposite to a slight enrichment of hematite.

Conclusions

The results showed that Pt is adsorbed mainly on kaolinite, which suggests that Pt was mainly associated with clay in soil. The results allowed the evaluation of the impact of the matrix of soil or sediment on the ability to retain or promote Pt dispersion in an urban environment.     

Spatial variability of trace elements in allotment gardens of four European cities: assessments at city,garden, and plot scale

Purpose

Urban allotment gardens (UAGs) are expanding worldwide, especially in large cities. Environmental pressures (direct and diffuse pollution, gardener practice, geogenic contamination) often result in the accumulation of potentially harmful trace elements in garden soils. The objectives of this study were to assess the spatial variability of trace element distribution in UAGs from city, garden, and plot scale in four European cities; to provide a baseline understanding and identify abnormal values under environmental pressures; and to evaluate the potential of portable X-ray fluorescence screening as a useful tool in soil management.

Materials and methods

The four cities (Ayr and Greenock (Scotland), Lisbon (Portugal), Nantes (France)) provided a wide range of environmental pressures on soils. The locations of the 14 allotment gardens were identified in consultation with the local municipality in each city to reflect various land uses or according to previous evaluation of soil quality. Soil sampling was carried out in 66 plots in total, from which 3 datasets were produced: (i) basic soil properties and trace element concentrations from a composite sample of topsoil for each plot (trace elements quantified by inductively coupled plasma–optical emission spectrometry/mass spectrometry (ICP-OES/MS) or using in-lab portable X-ray fluorescence (PXRF); (ii) in situ PXRF measurement on composite samples (263 plots in Nantes); and (iii) composite samples from 32 small areas within 4 plots in one garden of Nantes.

Results and discussion

The results were analyzed to assess the spatial variability of soil properties. At city and garden scale, the variability observed for basic soil properties and major elements is dominated by local geology/parent material (pH, CaCO₃, Fe) and gardening practice (OM, CaCO₃), which vary between each country. The range of trace element concentrations is similar between each city except for Greenock. Extreme values are observed for Cu, Pb, and Zn reflecting human disruption. In most situations, the trace element contamination was explained through the historical and environmental situations of the site. The PXRF screening method proved useful in providing detailed mapping for hot spot detection or delineation, providing support for soil management at plot and garden scale.

Conclusions

As anticipated, basic soil properties appear to be controlled by the parent material. At plot and garden scale, the trace element variability shows the influence of land use history and background and strong inputs from external factors (e.g., by industrial activity or traffic emission). The PXRF screening method appears to be an efficient solution for soil management as it can be used to discriminate zones which may require restriction on cultivation.