Integrated Assessment of Affinity to Chemical Fractions and Environmental Pollution with Heavy Metals: A New Approach Based on Sequential Extraction Results

To assess the affinity degree of heavy metals (HMs) to geochemical phases, many indices with several limitations are used. Thus, this study aims to develop a new complex index for assessing contamination level and affinity to chemical fractions in various solid environmental media. For this, a new integrated approach using the chemical affinity index (CAF) is proposed. Comparison of CAF with %F on the literature examples on fractionation of HMs from soils, bottom sediments, atmospheric PM10, and various particle size fractions of road dust proved a less significant role of the residual HMs fraction and a greater contribution of the rest of the chemical fractions in the pollution of all studied environments. This fact is due to the normalization relative to the global geochemical reference standard, calculations of contribution of an individual element to the total pollution by all studied HMs, and contribution of the particular chemical fraction to the total HMs content taken into account in CAF. The CAF index also shows a more significant role in pollution and chemical affinity of mobile and potentially mobile forms of HMs. The strong point of CAF is the stability of the obtained HM series according to the degree of chemical affinity and contamination. Future empirical studies are necessary for the more precise assessment of CAF taking into account the spatial distribution of HMs content, geographic conditions, geochemical factors, the intensity of anthropogenic impact, environmental parameters (temperature, humidity, precipitation, pH value, the content of organic matter, electrical conductivity, particle size distribution, etc.). The combined use of CAF along with other indices allows a more detailed assessment of the strength of HMs binding to chemical phases, which is crucial for understanding the HMs’ fate in the environment.

Metal and phosphorus in bottom sediment of a small-sized reservoir in a rural mountainous catchment (NE Portugal): accumulation and geochemical mobility

<p>Small-sized reservoirs have less capacity for the retention of sediment but are widely distributed in regulated basins. Therefore, small reservoirs collectively impart an important anthropogenic signature to the global sediment-flux, increasing the mean sediment retention when compared with estimates of mean sediment retention of large reservoirs.</p><p>A geochemical study of sediment-associated metal and phosphorus from a small-sized riverine reservoir, located in a mountainous rural region (Vila Real in NE Portugal), was conducted to evaluate the effectiveness of the reservoir as traps for these elements. The contents of metals and P were determined, as well as their spatial distribution pattern and their potential availability by using a four-step sequential extraction procedure for metals and the Chang and Jackson fractionation for P.</p><p>The metal contents in sediments were in the ranges of (µg/g): Cr (22-122); Cu (31-83); Ni (5-71); Pb (49-160); Zn (207-334). All the geochemical phases studied were important in the retention of the metals; within the most labile fractions, the reducible fraction was the most significant. The studied elements can be classed by potential relative mobility: Zn > Pb > Cu > Cr, Ni. The partition of elements contents through the geochemical phases and the balance between contents associated with the most mobile fractions and with the residual fraction suggest an important contribution from lithology to the total contents of Cr and Ni, and a significant contribution of anthropogenic activities to the contents of Cu, Pb, and Zn in the sediments from the reservoir. The analysis of the results on the geochemical partitioning of metals revealed to be important when the Sediment Quality Guidelines (SQGs) are considered. Phosphorus showed contents ranging between 1518-2454 µg/g; most samples revealed the predominance of the Fe-P fraction.</p><p>In general, the sediments of the reservoir showed maximum values of contents of metals above the Threshold Effect Level (TEL, µg/g: Cr-37.3; Cu-35.7; Ni-18; Pb-35; Zn-123). Chromium, Ni, Pb and Zn showed total contents exceeding the values of Probable Effect Level (PEL, µg/g: Cr-90; Cu-197; Ni-36; Pb-91.3; Zn-315). Chromium and Ni showed higher values than the reference ones, but these can be considered relatively unavailable since they are associated with the residual phase. The potentially available and/or total amounts of metals and P in sediments were relatively high, indicating that the quality of bottom sediments accumulated in this small-sized reservoir should be considered in management policies.</p>

Batch washing of lead contaminated and spiked soils using extracts of dried Terminalia mantaly, Panicum maximum and Eleusine indica plants

Application of dried plant water soluble extracts in soil Pb decontamination is rear, but advantageous due to their ecological biodegradability. Single batch laboratory scale suitability of Terminalia mantaly, Panicum maximum, Eleusine indica and water as washing solutions for Pb removal from contaminated and spiked soils at different soil pulp densities (3%, 6%, 9%, 12%, 15% and 18%) and washing time (1, 3, 6, 12, 24 and 96 h) was investigated. Washings of Terminalia mantaly and Panicum maximum proved more efficient comparatively for contaminated soil with Pb removal efficiency of 27.2±0.64% and 27.0±0.52% respectively at 3% soil pulp density and washing time of 96 h. Removal efficiency increased with increasing washing time but decreased with increasing of soil pulp density. Furthermore, water was found effective for removing Pb from spiked soils with maximum removal efficiency of 74.5±3.38% at 3% soil pulp density after 1 h washing. High exchangeable fraction of Pb (81.2%) in spiked soil makes water more suitable against other washing solutions. Statistical t-testing showed significant difference in Pb removal efficiency between contaminated and spiked soils for all four washing solutions, reflecting differences in geochemical phases of Pb in both soils. Terminalia mantaly and Panicum maximum showed promising result in soil washing and have potential for application in Pb removal from contaminated soils. However, chemical modifications are needed to enhance and improve on their efficiencies. Similarly, more information is needed to predict and model removal efficiencies when multiple washing steps are applied.

Sequential Extractions and Toxicity Potential of Trace Metals Absorbed into Airborne Particles in an Urban Atmosphere of Southwestern Nigeria

The paper investigates the hypothesis that biotoxicities of trace metals depend not only on the concentration as expressed by the total amount, but also on their geochemical fractions and bioavailability. Airborne particles were collected using SKC Air Check XR 5000 high volume Sampler at a human breathing height of 1.5–2.0 meters, during the dry season months from November 2014 to March 2015 at different locations in Akure (7°10′N and 5°15′E). The geochemical-based sequential extractions were performed on the particles using a series of increasingly stringent solutions selected to extract metals (Cd, Cu, Cr, Ni, Pb, Zn, and Mn) into four operational geochemical phases—exchangeable, reducible, organic, and residual—and then quantified using an Atomic Absorption Spectrophotometer. The results showed metals concentration of order Pb > Cr > Cd > Zn > Ni > Cu > Mn. However, most metals in the samples exist in nonmobile fractions: exchangeable (6.43–16.2%), reducible (32.58–47.39%), organic (4.73–9.88%), and residual (18.28–27.53%). The pollution indices show ingestion as the leading route of metal exposure, with noncarcinogenic (HQ) and cancer risk (HI) for humans in the area being higher than 1.0 × 10−4, indicating a health threat.

Spatiotemporal redox dynamics in a freshwater lake sediment under alternating oxygen availabilities: combined analyses of dissolved and particulate electron acceptors

Environmental contextAt sediment surfaces, the availability of oxygen is controlled by its downward transport from the water surface and its consumption in microbial metabolism. Microorganisms can also consume substances other than oxygen to dispose of the surplus charge that is generated during microbial metabolism. We investigate the complex dynamics of these other substances when the oxygen availability fluctuates, and thereby contribute to the mechanistic understanding of oxygen-consuming processes in aquatic environments. AbstractBenthic mineralisation in lakes largely controls the availability of oxygen in the water column above the sediment. In stratified lakes with anoxic hypolimnetic waters, mineralisation proceeds by anaerobic respiration using terminal electron acceptors (TEAs) other than O2. In past work, hypolimnetic oxygen consumption has been estimated from vertical concentration profiles of redox-active dissolved species in the water column and the underlying sediment. Electron transfer to and from particulate mineral and organic phases in the sediments was, however, not accounted for, mainly because of methodological constraints. In this work we use an electrochemical approach, mediated electrochemical analysis, to directly quantify changes in the redox states of particulate geochemical phases in a lake sediment. In mesocosm incubations, sediments were subjected to shifting oxygen availability similar to conditions during and after lake overturn events. The temporal redox dynamics of both dissolved and particulate phases in sediments were monitored at a high spatial resolution. We used a combination of experimental and modelling approaches to couple the observed changes in the redox state of dissolved and particulate species in the sediment to the oxygen turnover in the overlying water column. For the studied freshwater sediment, the amount of O2 consumed during the re-oxidation of these phases in the top 21mm of the sediment after switching from hypoxic to oxic conditions corresponded to ~50% of the total sediment oxygen consumption that was estimated from in-lake measurements after the onset of summer stratification. We found that solid phases in the sediments play a more profound role in electron accepting processes than previously considered. Based on these results, we propose that the herein presented analytical method offers the possibility to constrain parameters in theoretical models that simulate benthic redox dynamics including the electron transfer to and from geochemical phases in the sediments.

Copper Mobility Assessment Using Speciation Schemes: Case Study–Mantrijeron District, Yogyakarta, Indonesia

factors such physical and chemical properties, especially mineralogical composition of such environment. This study focused on the mineralogical of two soils types (fine sandy loam and loamy fine sand) to retain/mobile Cu. Two non contaminated soils from Yogyakarta urban area, Indonesia, were artificially contaminated with Cu solution. Subsequently, soils artificially contaminated were extracted from various geochemical phases of soil by sequential extraction procedure. The results show that both of soils types can retain Cu well with maximum is 5.8 mg/g of loamy fine sand and 3.9mg/g of fine sandy loam. Additionally, the iron amorphous phase content in clay fraction is influence Cu retains in these soils. This is advantage in environment of Yogyakarta urban area, Indonesia, where this area underlain by loamy sand soil. Keywords: Copper, mobility, iron, sequential extraction.