Metal immobilization may contribute to the environmental management strategy of dredged sediment landfill sites contaminated by metals. In a field experiment, amendment effects and efficiency were investigated, focusing on plants, springtails and bacteria colonisation, metal extractability and sediment ecotoxicity. Conversely to hydroxylapatite (HA, 3% DW), the addition of Thomas Basic Slag (TBS, 5% DW) to a 5-yr deposited sediment contaminated with Zn, Cd, Cu, Pb and As resulted in a decrease in the 0.01 M Ca(NO₃)₂-extractable concentrations of Cd and Zn. Shoot Cd and Zn concentration in Calamagrostis epigejos, the dominant plant species, also decreased in the presence of TBS. The addition of TBS and HA reduced sediment ecotoxicity and improved the growth of the total bacterial population. Hydroxylapatite improved plant species richness and diversity and decreased antioxidant enzymes in C. Epigejos and Urtica dïoica. Collembolan communities did not differ in abundance and diversity between the different treatments.

The physico-chemical properties of dust particles collected During Dust Storm (DDS) and After Dust Storm (ADS) events were studied using Scanning Electron Microscope coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray Fluorescence Spectroscopy (XRF) and X-ray Photoelectron Spectroscopy (XPS). Morphological and compositional change in dust particles were observed as they react with the anthropogenic pollutants present in the urban environment. The calcite rich particles were observed to transform into calcium chloride, calcium nitrate, and calcium sulfate on reacting with the chlorides, nitrates, and sulfates present in the urban atmosphere. The frequency distributions of Aspect Ratio (AR) for the DDS and ADS particles were observed to be bimodal (mode peaks at 1.2 and 1.5) and monomodal (mode peak at 1.1), respectively. The highly irregular shaped solid dust particles were observed to transform into nearly spherical semisolid particles in the urban environment. XPS analysis confirms the high concentration of oxides, nitrates, and chlorides at the surface of ADS samples which show the signatures of mineral dust particles aging. Species with a high value of imaginary part of refractive index (like Cr metal, Fe metal, Cr₂O₃, FeO, Fe₂O₃) were observed at the surface of dust particles. At 550 nm wavelength, the light-absorbing potential of the observed species along with black carbon (BC) was found to vary in the order; Cr metal > Fe metal > Cr₂O₃> FeO > BC > Fe₂O₃> FeOOH. The presence of the aforementioned species on the surface of ADS particles will tremendously affect the particle optical and radiative properties compared to that of DDS particles. The present work could reduce the uncertainty in the radiation budget estimations of mineral dust and assessment of their climatic impacts over Delhi.

Municipal solid wastes (MSW) can be composted to become an organic fertilizer. However, besides plant nutrients, it can also contain high concentration of some toxic metals than can pollute agricultural soils, contaminate food, animals and human being. A greenhouse experiment was carried out for two purposes: i) to evaluate the concentrations of cadmium, copper, chromium, nickel, lead and zinc in four Brazilian MSW composts, and, ii) to know which is the best solution for extracting those metals in phytoavailable form from the composts. In order to evaluate the phytoavailability of metals, they were extracted with six chemical extractants: i) water, ii) 0.05 mol L⁻¹ Ca(NO₃)₂, iii) 0.1 mol L⁻¹ HCl, iv) 0.005 mol L⁻¹ DTPA at pH 7.3, v) 0.05 mol L⁻¹ CaCl₂ and vi) Mehlich 3 solution. In addition, lettuces were cultivated as a test plant in pots containing 1.8 kg of MSW compost as substrate. Fifty-six days later, lettuce plants were harvested. New lettuces were then planted for a second cycle, and then harvested after fifty-six days. Semi-total concentration of metals in composts and total in plants was also determined through an extraction with nitric-perchloric acid. Semi–total concentration of Cd and Pb exceeded the intervention limits from Brazil in the four studied composts, and lettuce plants were polluted by those two elements. Therefore, compost made of MSW must be characterized before being used for agricultural soils. Copper and nickel in phytoavailable were effectively extracted with the strongest chelating agents used, HCl and Mehlich 3, probably because most metal is bound to organic matter in the compost. Cadmium, chromium, lead and zinc were no efficiently extracted with any of the tested extractants.

Few studies have quantified the accuracy of soil metal bioavailability assays using large datasets. A meta-analysis from experiments spanning 6 months to 13 years on 12 soil types, compared bioavailability estimate efficiencies for wheat and ryegrass. Treatments included biosolids ± metals, comparing total metal, Ca(NO₃)₂, EDTA, soil solution, DGT and free ion activity. The best correlations between soil metal bioavailability and shoot concentrations were for Ni using Ca(NO₃)₂ (r² = 0.72) which also provided the best estimate of Zn bioavailability (r² = 0.64). DGT provided the best estimate of Cd bioavailability, accounting for 49% of shoot Cd concentrations. There was no reliable descriptor of Cu bioavailability, with less than 35% of shoot Cu concentrations defined. Thus interpretation of data obtained from many soil metal bioavailability assays is unreliable and probably flawed, and there is little justification to look beyond Ca(NO₃)₂ for Ni and Zn, and DGT for Cd.

We studied the bonding and release kinetics of Cd, Cu and Pb from different soils in the older metropolitan area of Copenhagen. Total Cd, Cu and Pb concentrations were elevated 5–27 times in the urban soils compared to an agricultural reference soil, with Cd and Pb in mainly mobilisable pools and Cu in strongly bound pools. The soils were subjected to accelerated leaching studies in Ca(NO3)2 or HNO3 solutions resulting in release up to 78, 18 and 15% of total Cd, Cu and Pb soil concentrations over a period of 15 weeks. The relative initial Cd and Pb release rates increased 10 fold when pH decreased 2 and 3 units, respectively, while increases in Cu release rates were only seen at pH below 4. The total leachable Cu and Pb pools were higher in urban soils compared the agricultural reference soil but not for Cd.

Simultaneous measurements of gaseous SO2, NO2, HNO3, NH3 and particulate SO42–, NO3– and NH4+ were carried out in a suburban area in Cairo during summer 2009 and winter 2009–2010. PTFE membrane filters were used to collect particulate SO42–, NH4+ and NO3–, followed by the impregnated filter to collect HNO3. Colorimetric methods were used for determination of NO2, SO2, NH3, SO42–, NH4+ NO3–, and HNO3 levels. The mean concentrations of NO2, SO2 and NH3 were 75.0, 40.1 and 29.1 µg/m3 in winter and 54.1, 25.1 and 44.9 µg/m3 in summer, respectively. The daytime/nighttime concentration ratios were 1.3 and 1.2 for NO2, 1.3 and 1.2 for SO2 and 0.6, and 0.8 for NH3 during the winter and summer, respectively. The mean values of NH4+, SO42–, NO3–, HNO3 and total NO3– were 4.4, 19.0, 3.4, 1.1 and 4.5 µg/m3 in winter and 7.5, 28.0, 4.2, 3.1 and 7.3 µg/m3 in summer, respectively. The levels of NH4+, SO42–, NO3– and HNO3 were relatively higher in daytime than in nighttime. Sulfur conversion (Fs) and nitrogen conversion ratios (Fn) in summer were about 1.78 and 2.15 times higher than in winter, respectively. Fs and Fn were higher in daytime than in nighttime. Significant positive correlation was found between Fs and relative humidity. The positive correlation between Fn and relative humidity was insignificant. The correlation between the concentration of NH4+ and NO3– indicates that NO3– may be found in fine mode (NH4NO3) in winter and it may be present predominantly as a coarse mode, such as Ca(NO3)2, Mg(NO3)2 and NaNO3 in summer. The concentration of SO42– was significantly correlated with NH4+ concentration, suggesting neutralization by NH3 and indicating that the forms of (NH4)2SO4 and/or NH4HSO4 exist in the aerosol. The NH4+/SO42– molar ratio indicates that SO42– in aerosol may be present as (NH4)2SO4, (NH4)2SO4.CaSO4.2H2O and CaSO4.

The size distribution of water-soluble inorganic components of urban aerosols in Shanghai was studied. The size-resolved aerosol samples collected by an 8-stage cascade sampler between April and May of 2012 were analyzed by ion chromatography. The ion mass concentrations followed the sequence of SO42−>NO3−~NH4+>Ca2+>Na+ ~Cl−>K+>Mg2+>F− for each size fraction below 2.1μm, while the sequence was NO3−>SO4−2>Ca2+>NH4+>Na+>Cl−>K+>Mg2+>F− for coarse mode particles larger than 3.3μm. The size distribution in 5 fractions showed that SO42−, NO3−, and NH4+ were generally in the fine mode peaking below 1μm while Ca2+, Mg2+, Na+, and Cl− were bimodally distributed with a second peak larger than 2.1μm. Back trajectory analyses revealed that the air masses could be classified into three main groups. The total ion concentrations were comparable between the terrestrial and mixing regimes. In the terrestrial regime, fine mode sulfate and nitrate were predominantly associated with ammonium. The excessive sulfate and nitrate over the whole size range might exist in the forms of Ca(NO3)2 and CaSO4. In the maritime regime, the decrease in SO42−, NO3−, and NH4+ contributed to the improvement in air quality. Besides marine aerosols, local emissions from soil dust and coal combustion were also important sources of sea-salt type ions (i.e., Na+ and Cl−).

Recently, calcium nitrate (CN) has been widely used in contaminated sediments remediation. However, the release of NO₃⁻–N, NO₂⁻–N, and Pb into the overlying water accompanying with the addition of CN may cause a toxic threat to the water ecosystem. Herein, this study investigated the effect of CN addition dosages on the sediment remediation, including oxidation-reduction potential (ORP), acid-volatile sulfide (AVS), phosphorus, nitrogen, and Pb. Results showed that, with the increase of CN addition ratio from 0.5× to 2.0× (from 0.5 to 2.0 times the theoretical CN dosage, based on autotrophic sulfide-driven denitrification), the ORP, AVS, and Fe (II) removal rates had a significant improvement. Moreover, due to the abundant Ca²⁺ and the oxidization of Fe (II), it would make O–P transformed to Ca–P and Fe/Al–P, which lead to the locking of phosphorus in sediments. However, this study indicated that the more CN added, the more NO₃⁻–N, NO₂⁻–N, and Pb²⁺ released in the overlying water. In addition, the increase of exchangeable Pb and oxidizable fraction Pb in sediments were characterized, which had a positive correlation with CN dosages (p < 0.01). Thus, secondary pollution needs to be considered for sediment remediation, and adding nitrate directly into sediments may not be suitable for natural water bodies.

Aim of this study was to evaluate the interactive effects of glycine, alanine, calcium nitrate [Ca(NO₃)₂], and their mixture on the growth of two wheat (Triticum aestivum L.) varieties, i.e., var. Punjab-2011 and var. Anaj-2017 under lead [0.5 mM Pb(NO₃)₂] stress. A pot experiment was conducted for this purpose. Pre-sowing seed treatment with 1 mM glycine, alanine, and calcium nitrate [Ca(NO₃)₂] was applied under two levels of lead nitrate [Pb(NO₃)₂] stress, i.e., control and 0.5 mM Pb(NO₃)₂. Lead (0.5 mM) stress significantly decreased root and shoot lengths, fresh and dry weights of root and shoot, and chlorophyll contents, while it increased activities of antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and peroxidase (POD) in both wheat varieties. Lead (0.5 mM) stress increased the accumulation of free proline, glycinebetaine, total free amino acids, and total soluble protein contents. Although var. Punjab-2011 was higher in root fresh and dry weights, shoot length, and total leaf area per plant, however, var. Anaj-2017 showed less reduction in shoot dry weight, root fresh weight, and shoot length under lead stress. Under lead stress, Punjab-2011 was higher in grain yield and number of grain plant⁻¹, chlorophyll a contents, membrane permeability (%), POD activity, total free amino acids, and glycinebetaine (GB) contents as compared to Anaj-2017. Pre-sowing seed treatments with glycine, alanine, calcium nitrate, and their mixture (1 mM of each) increased shoot dry weight, number of grains per plants, 100-grain weight, number of spikes, and chlorophyll a contents under normal and lead-stressed conditions. Wheat var. Anaj-2017 showed higher growth and yield attributes as compared to var. Punjab-2011. Results of the current study have shown that pre-sowing seed treatments with glycine, alanine, calcium nitrate, and their mixture (1 mM of each) can overcome the harmful effects of lead (Pb) stress in wheat plants.