Conventional clay capping for post-closure management of landfill commonly cracks and deteriorates over time. As a consequence, water ingress into waste increases as a function of time, potentially causing a range of environmental issues. An alternative approach is known as phytocapping, which utilizes select plant species to control cap stability and moisture percolation. In this study, growth of Arundo donax L. (giant reed), Brassica juncea (L.) Czern. (Indian mustard), and Helianthus annuus L. (sunflower) on a landfill site was studied with different biosolid amendment rates (0, 25, and 50 Mg ha−1). Cultivation of the landfill cap and amendment with biosolids significantly improved the characteristics of the soil. Growth of each plant species increased due to biosolid addition. Giant reed produced the largest biomass in the 50 Mg ha−1 biosolid amendment rate (38 Mg ha−1 dry weight). The high pH and clay content of landfill cap soil, and the low metal concentrations of the biosolid resulted in low heavy metal (copper, zinc, cadmium, and lead) accumulation in leaves of most treatments. The improvement in growth and limited uptake of metal contaminants to plant shoots indicated that biosolid application to landfill clay caps improves the application of phytocapping of old landfill sites.

Nitrogen (N) deposition to the ocean is thought to be increasing worldwide, but the amount of coastal and open ocean measurements is very limited. In this paper, we assess N deposition in the coastal zone of Cayo Coco, in central Cuba, during a multi-annual period (2005–2007). Wet and dry N depositions were estimated based on the NH 4 + and NO x – concentrations in the rain. Cold fronts and troughs, coming from the west, contributed most to rain (41%) and to N deposition, followed by tropical waves and storms coming from the east, which caused 31% of the rain. Average concentrations of NH 4 + and NO x – in the rain were 8.8 and 8.3 μM. NO x – presented a clearly decreasing trend (0.26 μM per month), decreasing by half during 2005–2007. Total N deposition averaged 3.23 kg N ha−1 year−1, similar to that found in Virgin Islands and Puerto Rico, but lower than previously measured in Cuba and in nearby areas of the USA and than model predictions for the oceanic region around Cuba. These low values and the decreasing trend found are attributed to drastic reduction of fossil fuel and fertilizer use in Cuba since 1990. Because land input has decreased even more drastically, deposition seems to be nowadays the most important N source to the coastal zone of Cayo Coco. The δ15N range of seagrass (Thalassia testudinum) and macroalgae (Penicillus dumetosus) in the area (−1.83‰ to 3.02‰ and +1.02‰ to +4.17‰, respectively) sustain that atmospheric sources (deposition and N2 fixation) comprise 70–90% of the N budget.

The effect of activated sludge acclimation on the biodegradation of toluene and dimethyldisulphide (DMDS) in the presence of a non-aqueous phase liquid, polydimethylsiloxane (PDMS), in a two-phase partitioning bioreactor was characterized. The influence of the presence of PDMS, at a ratio of 25% (v/v), and acclimation of activated sludge on two hydrophobic VOC biodegradation was studied. Activated sludge were acclimated to each VOC and in the presence of the non-aqueous phase liquid, namely in the emulsion of PDMS in water. Using acclimated cells, 97.9% and 108.7% improvement of the mean biodegradation rates were recorded for toluene and DMDS, respectively, if compared to the values recorded in the absence of acclimation. While and in agreement with the lower solubility in water of DMDS if compared to toluene, a most significant effect of PDMS addition on the rate of DMDS removal was recorded, 87.0% and 153.6% for toluene and DMDS, respectively. In addition and if both biomass acclimation and PDMS addition were considered, overall improvements of the removal rates were 204% and 338% for toluene and DMDS.

Nanocomposite of CeO₂–SnO₂ containing different CeO₂ contents was prepared by coprecipitation process. The material obtained was characterized by X-ray diffraction and N₂ adsorption–desorption isotherms. Its photocatalytic activity was tested in the degradation of azo dye of leather, Direct Black 38, in aqueous solution under sunlight. The photocatalytic activity of the coupled CeO₂–SnO₂ oxide ranged depending on the CeO₂ contents. The optimum amount of CeO₂ for the synthesis of CeO₂–SnO₂ was 7 wt.% since the nanoparticles showed high photocatalytic activity in the degradation of the dye, similar to that of the TiO₂–P25 photocatalyst. The kinetics of photocatalytic degradation and total organic carbon removal under sunlight were found to follow a first-order rate law. The results indicated that CeO₂–SnO₂ can be used for the removal of dyes from wastewater.

The objective of this study was to investigate the effects of adding different rates of diethylenetriamine pentaacetate (DTPA) at different concentrations (0, 0.5, 1, and 5 mmol kg−1) and ethylenediamine disuccinate (EDDS) at 0, 5, 7.5, and 10 mmol kg−1 on the capacity of Brussels sprouts plants to take up Se from soils contaminated with 0, 5, 10, and 15 mg kg−1 NaSeO4, under a greenhouse conditions. Results indicated that the application of DTPA and EDDS to Se-contaminated soils significantly affect plant Se concentration, Se uptake, and dry matter yield of plants. Se concentration in the plant leaves, stems, and roots increased with increase in DTPA and EDDS application doses, but total Se uptake increased from 0 to 1.0 and 7.5 mmol kg−1 DTPA and EDDS application doses, respectively, and decreased after those levels due to toxic Se concentration for plant. Most plant available fractions and the carbonate, metal oxide, and organic matter-bound fractions increased linearly with Se application. At all DTPA and EDDS application rates, the Se concentrations in the leaves were about two to three times higher than those in the roots and about three to four times higher than those in the stems. This study suggests that the above-ground organs like leaf and shoots of Brussels sprouts can effectively be used in the removal of Se from soils contaminated with Se. Under the conditions in this experiment, Brussels sprouts were capable of removing 0.9–1.8 mg Se pot−1 when harvested at maturity without any chelating agent take into consideration one growing season per year. Based on the data of present experiment, it would be necessary to approximately 57–67 growing seasons without EDDS and EDTA to remove all total Se from polluted soil. Selenium removal can be further increased 12- to 20-fold with 7.5 mmol kg−1 EDDS and 1.0 mmol kg−1 DTPA application, respectively.

Following the Deepwater Horizon explosion and crude oil contamination of a marsh ecosystem in AL in June 2010, hydrocarbon-degrader microbial abundances of aerobic alkane, total hydrocarbon, and polycyclic aromatic hydrocarbon (PAH) degraders were enumerated seasonally. Surface sediment samples were collected in October and December of 2010 and in April and July of 2011 along 40–70-m transects from the high tide to the intertidal zone including Spartina alterniflora-vegetated marsh, seagrass (Ruppia maritima)-dominated sediments, and nonvegetated sediments. Alkane and total hydrocarbon degraders in the sediment were detected, while PAH degraders were below detection limit at all locations examined during the sampling periods. The highest counts for microbial alkane degraders were observed at the high tide line in April and averaged to 8.65 × 105 of cells/g dry weight (dw) sediment. The abundance of alkane degraders during other months ranged from 9.49 × 103 to 3.87 × 104, while for total hydrocarbon degraders, it ranged between 5.62 × 103 and 1.14 × 105 of cells/g dw sediment. Pore water nutrient concentrations (NH 4 + , NO 3 − , NO 2 − , and PO 4 3− ) showed seasonal changes with minimum values observed in December and April and maximum values in October and July. Concentrations of total petroleum hydrocarbons in sediments averaged 100.4 ± 52.4 and 141.9 ± 57.5 mg/kg in January and July, 2011, respectively. The presence of aerobic microbial communities during all seasons in these nearshore ecosystems suggests that an active and resident microbial community is capable of mineralizing a fraction of petroleum hydrocarbons.

Benzo[a]pyrene (BaP) has been proven to be toxic and carcinogenic. Since 2010, the European Union officially established target values for BaP concentrations in ambient air. In this study BaP concentrations over Europe have been modelled using a modified version of the chemistry transport model Community Multiscale Air Quality (CMAQ) which includes the relevant reactions of BaP. CMAQ has been run using different emission datasets for the years 1980, 2000, and 2020 as input data. In this study, the changes in BaP concentrations between 1980 and 2020 are evaluated and regions which exceed the European annual target value of 1 ng/m3 are identified, i.e. the Po Valley, the Paris metropolitan area, the Rhine-Ruhr area, Vienna, Madrid, and Moscow. Additionally, the impact of emission reductions on atmospheric concentrations of BaP is investigated. Between 1980 and 2000, half of the BaP emission reductions are due to lower emissions from industrial sources. These emission reductions, however, only contribute to one third of the total ground-level BaP concentration reduction. Further findings are that between 2000 and 2020, a large part (40%) of the BaP concentration reduction is not due to changes in BaP emissions but caused by changes in emissions of criteria pollutants which have an impact on the formation of ozone.

Over the past few years the number of biogas slurries, which are generally used as nitrogen fertilisers, have seen a steady increase in Germany. A mechanistic ammonia volatilisation model was developed to predict the ammonia losses of these slurries when applied to bare soil, maize, wheat and rye grass canopies. Data for model development were collected from several field measurements carried out at two locations in Northern Germany between the years of 2007 and 2008. Additionally, the behaviour of the slurries on and in the soil was investigated through the use of infiltration pot experiments. The model includes three main compartments: slurry, atmosphere and soil. The soil compartment model is relatively simple, as the slurry infiltration, nitrification and ploughing dislocation into the soil determined in the experiments showed quantitatively no significant differences between the tested slurries (mono-fermented, co-fermented and pig slurry) and soils (sand soil and loamy sand). Hence, instead of a complex soil model, stable reduction factors, as derived from the experiments, were implemented in the model. Simulated ammonia emissions were statistically compared (root mean square error (RMSE), modelling efficiency (ME), linear regression) to the observed emissions. All evaluations showed an acceptable model performance (RMSE = 1.80 kg N ha−1), although there were a few number of anomalies which could not be modelled in an adequate way. A model sensitivity analysis showed that temperature and slurry pH value are the main drivers of NH3 volatilization in the model. Following a change of +1°C or of +0.1 pH unit ammonia volatilization will increase by about 1% and 1.6% of the applied total ammoniacal nitrogen, respectively. We were able to show that a simple model approach could explain most factors of ammonia volatilization in biogas crop rotations.

A new speciation model developed and implemented in Polymath was found to be successful in predicting struvite precipitation in soils. Struvite (NH4MgPO4) has been identified as a mineral for the recovery of nitrogen (N) and phosphorus (P). Predicting struvite precipitation potential in soil is important for optimal quantification of nutrient species. Polymath and Visual Minteq models were used for prediction of several solid phases in the soil. One approach to immobilize P for solid-phase formation is by co-blending. Immobilization was achieved through the blending of an Al-based water treatment residual (Al-WTR) and with Ca–Mg-based materials [slag and magnesium oxide (MgO)]. The results suggest that Polymath model revealed solid Phases of dicalcium phosphate pentahydrate (DCPP), magnesium hydroxide (MHO), magnesium orthophosphate (v) docosahydrate (MP22), magnesium orthophosphate (v) octahydrate (MP8), and struvite, which were lacking in the modeling from Visual Minteq. Residual leachate from the co-blended amendments; Soil+WTR+Slag, Soil+WTR+MgO, Soil+MgO, Soil+Slag, Soil+WTR, and the control (without amendment) had struvite of 353, 199, 119, 90, 37, and 12 mg l-1, respectively. This implies that struvite, a phosphate mineral can be precipitated in the soil and could be released as nutrients for plant uptake. Struvite precipitation in soil and for reuse may reduce cost and may be a safe practice for sustainable environmental nutrient management.

The adsorption of residue oil from palm oil mill effluent using natural zeolite was investigated in this study. The adsorption was performed in batch mode, and the effect of different operational parameters such as pH, dose of adsorbent, stirring rate, contact time and initial oil concentration were explored. It was found that the pH plays a major role in the adsorption process. Isotherm data best fitted with the Freundlich model, and kinetic data followed the pseudo-second-order kinetic model. The results obtained demonstrated that the oil removal efficiencies by natural zeolite were up to 70 % at a pH of 3.0 and 50 min of contact time. The adsorbent material also has been characterised by X-ray diffraction, X-ray fluorescence and scanning electron microscopy.