Åsgeir R. Almås

Solubility and lability of cadmium and zinc in two soils treated with organic matter

The effect of organic matter (pig manure, Sus scrofa) addition on solubility and free Cd(II) and Zn(II) speciation was studied in two mineral soils. The soils were extracted with ultra pure 0.01 M KNO3, and the extracts were analyzed for total dissolved Cd and Zn by graphite furnace AAS and ICP, res

Sewage sludge disposal strategies for sustainable development

ABSTRACT The main objective of the present review is to compare the existing sewage sludge management solutions in terms of their environmental sustainability. The most commonly used strategies, that include treatment and disposal has been favored within the present state‐of‐art, considering existing legislation (at European and national level), characterization, ecotoxicology, waste management and actual routs used currently in particular European countries. Selected decision making tools, namely End‐of‐waste criteria and Life Cycle Assessment has been proposed in order to appropriately assess the possible environmental, economic and technical evaluation of different systems. Therefore, some basic criteria for the best suitable option selection has been described, in the circular economy “from waste to resources” sense. The importance of sewage sludge as a valuable source of matter and energy has been appreciated, as well as a potential risk related to the application of those strategies. HighlightsEnvironmental sustainability in sewage sludge management.Investigation of eco‐innovations in wastewater treatment.Assessment of ecological consequences of sewage sludge disposal.

Antimony (Sb) and lead (Pb) in contaminated shooting range soils: Sb and Pb mobility and immobilization by iron based sorbents, a field study

Small-arm shooting ranges often receive a significant input of lead (Pb), copper (Cu) and antimony (Sb) from ammunition. The goal of the present study was to investigate the mobility, distribution and speciation of Pb and Sb pollution under field conditions in both untreated and sorbent-amended shooting range soil. Elevated Sb (19-349μgL(-1)) and Pb (7-1495μgPbL(-1)) concentrations in the porewater of untreated soil over the four-year test period indicated a long-term Sb and Pb source to the adjacent environment in the absence of remedial measures. Mixing ferric oxyhydroxide powder (CFH-12) (2%) together with limestone (1%) into the soil resulted in an average decrease of Sb and Pb porewater concentrations of 66% and 97%, respectively. A similar reduction was achieved by adding 2% zerovalent iron (Fe°) to the soil. The remediation effect was stable over the four-year experimental period indicating no remobilization. Water- and 1M NH4NO3-extractable levels of Sb and Pb in field soil samples indicated significant immobilization by both treatments (89-90% for Sb and 89-99% for Pb). Results from sequential extraction analysis indicate fixation of Sb and Pb in less accessible fractions like amorphous iron oxides or even more crystalline and residual mineral phases, respectively. This work shows that amendment with Fe-based sorbents can be an effective method to reduce the mobility of metals both in cationic and anionic form in polluted shooting range soil.

Use of Diffusive Gradients in Thin Films to Predict Potentially Bioavailable Selenium in Soil

Abstract In this study, diffusive gradients in thin films (DGT) were used for determination of anionic selenium (Se) species. First, a laboratory experiment was carried out to investigate ferrihydrite (the anionic sorbent in the DGT) complexation of anionic Se in an aqueous solution. A conditional DGT effective diffusion coefficient (DDGT) for Se was estimated to be 5.0×10−6 and 5.3×10−6 cm2 s−1 at pH 5.1 and pH 6.3, respectively. Second, DGT units were placed in pastes of soil that were sampled from a field experiment with mineral Se fertilization at two soil pH levels. Based on the DGT measurements, an effective concentration (CE) for Se in soil was calculated. A CE(Se) value significantly higher than the control was estimated at the highest Se dose and the lower pH (5.5). Refinement of the method is needed, but this investigation indicates that the DGT technique can be used to determine potentially bioavailable Se fractions in soil.

Water extractable concentrations of Fe, Mn, Ni, Co, Mo, Pb and Cd under different land uses of Danube basin in Croatia

Abstract Water extraction of trace elements can simulate the concentration of elements in the soil solution from where the plant takes up the elements. The objective of this investigation was to determine the water extractable concentration of seven trace elements (Fe, Mn, Ni, Co, Mo, Pb and Cd) and to assess their relationship with soil properties of the Danube basin in Croatia. Soil samples from the surface layer (0–25 cm) of 74 sites, having different land uses (forest and agricultural land), were collected. Samples were analysed for total and water extractable trace elements as well as for pH, DOC, SOC and CEC. The concentrations of water extractable fraction of trace elements were on average: 20.14 mg kg−1 for Fe, 3.61 mg kg−1 for Mn, 0.07 mg kg−1 for Ni, 0.016 mg kg−1 for Co, 0.01 mg kg−1 for Mo, 0.01 mg kg−1 for Pb and 0.0009 mg kg−1 for Cd. Soil properties were in the following range: pH 4.3–8 (Avg: 6.35), DOC 6.1–73 mg l−1 (Avg: 26 mg l−1), CEC 1.3–24 cmol kg−1 (Avg: 9 cmol kg−1) and SOC 0.5–5% (Avg: 1.7%). The concentration of water extractable fraction of trace elements was significantly correlated with pH (p <0.001), DOC (p <0.001 – p <0.05) and CEC (p <0.001) but their relationship with total content of trace element and SOC was rather weak, suggesting that total metal alone cannot be an indicator of toxicity or deficiency. Results show that pH, DOC and CEC are important soil quality parameters taking part in the solubility control of trace metals in the soil rather than their total concentration. The difference between land uses has been observed as well, suggesting that a change in land use can cause a change in trace element solubility.

Anaerobic digestion of sewage sludge with grease trap sludge and municipal solid waste as co-substrates ☆

&NA; The feasibility of simultaneous treatment of multiple wastes via co‐digestion was studied in semi‐continuous mode at mesophilic conditions. The obtained results indicated that sewage sludge, organic fraction of municipal waste (OFMSW) and grease trap sludge (GTS) possess complementary properties that can be combined for successful anaerobic digestion. During the co‐digestion period, methane yield and VS removal were significantly higher in comparison to digestion of sewage sludge alone. Addition of GTS to digesters treating sewage sludge resulted in increased VS removal and methane yield up to 13% (from 50 to 56.4) and 52% (from 300 to 456,547 m3/Mg VSadd), respectively. While the use of OFMSW as the next co‐substrate in the feedstock, can boost methane yield and VS removal up to 82% (300–547 m3/Mg VSadd) and approximately 29% (from 50% to 64.7%), respectively. Moreover, the results of the present laboratory study revealed that the addition of co‐substrates to the feedstock had a significant influence on biogas composition. During the experiment methane content in biogas ranged from 67% to 69%. While, the concentration of LCFAs was increasing with the gradual increase in the share of co‐substrates in the mixtures, wherein only the oleic acid was higher than some inhibition concentrations which have been reported in the literature. However, it did not significantly affect the efficiency of the co‐digestion process. HighlightsAddition of two waste into the sewage sludge digester improves process efficiency.Co‐digestion of 3‐component mixtures increases VS removal up to 29%.While, methane yield increased up to and 82% relative to the control digester.Effectiveness of the process depends on OLR and the content of waste in the feedstock.

Trace Element Concentrations in Soil, Sediments, and Waters in the Vicinity of Geita Gold Mines and North Mara Gold Mines in Northwest Tanzania

The “Geita Gold Mine” (GGM) and “North Mara Gold Mines” (NMGM) have developed large quarries in the middle of fertile agricultural lands. Possible hazardous impact on the natural recourse has warranted a study on the trace element concentrations in soils, sediments, and natural waters. Generally, the study shows a great variation in type of elements and intensity of their spill to soils, sediments, and waters. We found indications of acid mine drainage (AMD) of trace metals near the GGM waste rock tailings, but the data are inconclusive. The environmental impact at NMGM was, on the other hand, more extensive. Severe trace element contamination of sediments and waters near one of the mining facilities managed by NMGM is connected to an accidental acid spill in 2009. However, we found strong indication that, in addition to the accident, leakage of alkaline wastewater into surface soils and free water took place from a large wastewater reservoir. We found very high concentrations, especially of As in sediments and water samples downside this reservoir. Water from several sites contained As concentration in the free water at more than one order of magnitude higher than the WHO drinking water recommendations. The chemical speciation of water samples indicated high fraction of Free Ion Activity (FIA) in several samples and the change in pH had a significant impact on the FIA. Due to extensive alkaline and acidic runoff from these sites, more information about hydrological transport routes and the chemical speciation of the free water is of great importance for assessing potential risk of these mines.

Prediction of trace metal concentrations (Cd, Cu, Fe, Mn and Zn) in wheat grain from unpolluted agricultural soils

Abstract Regression modelling and statistical correlations are often developed to aid reasonable predictions of metal solubility and free metal ion in terrestrial ecosystems. In the present study, we test how regression model predictions of metal solubility and free metal ion correlate with metal concentrations in plants. We previously optimised a model for the prediction of metal solubility and free metal ion concentrations in soil solution from sites collected in the Danube basin of Eastern Croatia, containing total metal concentration (concentrated HNO3), soil pH, soil organic matter (SOM) and dissolved organic carbon (DOC) as model parameters. In the present study, we report how our optimised models correlate with metal concentration in plants reported by Lončarić et al., which was based on a study from a smaller part of the same sampling area. Our default regression model and further optimised model predicted metal solubility and free metal ion concentrations. These predictions correlated well with Fe, Mn, Zn and Cd concentrations in wheat grain, but the different extraction methods and parameter optimisations affected the significance of correlations differently. Due to the low concentrations of total metal concentrations in soil and little variation in SOM, the soil pH was the only variable, in addition to the total metal controlling the metal solubility, free metal ion in soil water and also the concentrations in wheat grain. Results show that after optimisation for the few most important soil chemical variables regression models can predict metal concentrations in plants fairly well. For this particular study, optimisation for total metal, soil pH and perhaps also SOM and DOC are sufficient.