Macrocapsules, composed of a pH-sensitive polymer and phosphate buffer, offer a novel remediation alternative for acidic ground waters. To test their potential effectiveness, laboratory experiments were carried out followed by a field trial within a coal pile runoff (CPR) acidic contaminant plume. Results of traditional limestone and macrocapsule treatments were compared in both laboratory and field experiments. Macrocapsules were more effective than limestone as a passive treatment for raising pH in well water from 2.5 to 6 in both laboratory and field experiments. The limestone treatments had limited impact on pH, only increasing pH as high as 3.3, and armoring by iron was evident in the field trial. Aluminum, iron and sulfate concentrations remained relatively constant throughout the experiments, but phosphate increased (0.15-32 mg/L), indicating macrocapsule release. This research confirmed that macrocapsules may be an effective alternative to limestone to treat highly acidic ground water. Encapsulated phosphate buffer macrocapsules were more effective than limestone for passive treatment of acidic coal pile runoff (CPR) contaminated ground water, increasing pH from 2.5 to 6 in laboratory and field experiments.

The Tinto and Odiel rivers are heavily affected by acid mine drainage from mining areas in the Iberian Pyrite Belt. In this work we have conducted a study along these rivers where surface water samples have been collected. Field measurements, total dissolved metals and Fe and inorganic As speciation analysis were performed. The average total concentration of As in the Tinto river (1975 μg L-1) is larger than in the Odiel river (441 μg L-1); however, the mean concentration of As(III) is almost four times higher in the Odiel. In wet seasons the mean pH levels of both rivers (2.4 and 3.2 for the Tinto and Odiel, respectively) increase slightly and the amount of dissolved total arsenic tend to decrease, while the As(III)/(V) ratio strongly increase. Besides, the concentration of the reduced As species increase along the water course. As a result, As(III)/(V) ratio can be up to 100 times higher in the lower part of the basins. An estimation of the As(III) load transported by both rivers into the Atlantic Ocean has been performed, resulting in about 60 kg yr-1 and 2.7 t yr-1 by the Tinto and Odiel rivers, respectively. Total arsenic concentration decreases along the water basins, however the As(III)/(V) ratio increases.

The evaluation of metal contents in the environment is of vital importance for the assessment of human exposure. Thus the species Usnea amblyoclada, Ramalina celastri and Tillandsia capillaris were tested as bioaccumulators of transition metals in the urban area of Córdoba city, Argentina. The level of metals on biomonitors was compared to that of total deposition samples. All three species discriminated zones within the urban area of Córdoba city with different pollution levels; they revealed high levels of Zn in the downtown area and confirmed high levels of some transition metals in an industrial area. The correlation analysis revealed that the lichen R. celastri had the highest correlation rates with total deposition samples, suggesting it is a valuable biomonitor of atmospheric pollution. A significant relationship was also observed between respiratory diseases in children and the contents of metal accumulated in R. celastri and T. capillaris, indicating their usefulness when assessing human exposure to metals. Metal accumulation in epiphytes is correlated with human respiratory diseases.

Paddy rice may contribute considerably to the human intake of As. The knowledge of soil characteristics affecting the As content of the rice plant enables the development of agricultural measures for controlling As uptake. During field surveys in 2004 and 2006, plant samples from 68 fields (Italy, Po-area) revealed markedly differing As concentration in polished rice. The soil factors total As(aqua regia), pH, grain size fractions, total C, plant available P(CAL), poorly crystalline Fe(oxal.) and plant available Si(Na-acetate) content that potentially affect As content of rice were determined. A multiple linear regression analysis showed a significant positive influence of the total As(aqua regia) and plant available P(CAL) content and a negative influence of the poorly crystalline Fe(oxal.) content of the soil on the As content in polished rice and rice straw. Si concentration in rice straw varied widely and was negatively related to As content in straw and polished rice. Field selection for total As, poorly crystalline Fe and plant available P in soil might contribute to control As content of paddy rice.

Effects of high atmospheric nitrogen-deposition partly depend on availability of phosphate. Lime-poor, but iron-rich dune grasslands are supposedly protected from grass-encroachment, due to P-fixation in iron phosphate. However, in iron-rich Dutch hinterdunes, dunes have low, but dry former beach plains high grass-encroachment. To test whether these zones differ in nutrient availability, and whether this changed with duration of grass-encroachment, we measured net N-mineralization, microbial characteristics and different fractions of P and Fe from pioneer and shortgrass to tallgrass stages approximately 10, 20 and >25 years old. N-mineralization did not differ between zones, but increased in older tallgrass stages in the organic layer. P-availability was significantly lower in the low grass-encroachment zone, with SOM values below 3% and mineral Fe above 40% allowing for P-fixation in iron phosphates. In the high grass-encroachment zone, however, P-availability increased, because SOM increased and Fe became incorporated in organic matter complexes, with more reversible P-sorption. Iron-rich dune grasslands may be protected from high N-deposition and grass-encroachment only when SOM is low, because only then P-fixation in iron phosphates occurs.

Zerovalent iron powder (ZVI or Fe⁰) and nanoparticulate ZVI (nZVI or nFe⁰) are proposed as cost-effective materials for the removal of aqueous antibiotics. Results showed complete removal of Amoxicillin (AMX) and Ampicillin (AMP) upon contact with Fe⁰ and nFe⁰. Antibiotics removal was attributed to three different mechanisms: (i) a rapid rupture of the β-lactam ring (reduction), (ii) an adsorption of AMX and AMP onto iron corrosion products and (iii) sequestration of AMX and AMP in the matrix of precipitating iron hydroxides (co-precipitation with iron corrosion products). Kinetic studies demonstrated that AMP and AMX (20 mg L⁻¹) undergo first-order decay with half-lives of about 60.3 ± 3.1 and 43.5 ± 2.1 min respectively after contact with ZVI under oxic conditions. In contrast, reactions under anoxic conditions demonstrated better degradation with t1/2 of about 11.5 ± 0.6 and 11.2 ± 0.6 min for AMP and AMX respectively. NaCl additions accelerated Fe⁰ consumption, shortening the service life of Fe⁰ treatment systems. 21Fe⁰ is efficient for the aqueous removal of the β-lactam antibiotics and chlorides enhanced the removal rate by sustaining the process of iron corrosion.

In Brazil's littoral, many iron ore industries are located in areas of restinga, a type of coastal ecosystem; such industries represent stationary sources of iron and acid particulates. The industrial sector is under expansion, threatening the already fragile ecosystem. In the present study, the simulated impact of these emissions was studied on the early establishment stages of two native plant species, Sophora tomentosa and Schinus terebinthifolius. The results indicate that S. tomentosa display deficient germination and low root tolerance when exposed to iron dust and acidity. Toxic iron concentrations were found to accumulate only in the roots of S. tomentosa plants exposed to increasing doses of iron dust. In these plants, initial growth was reduced, leading to the conclusion that S. tomentosa was unable to regulate, and, thus, to overcome, the effects of the iron dust in the substrate. In contrast, the germination, root tolerance index, and initial growth of S. terebinthifolius were not affected by iron dust and acidity, revealing the species' resistance to these pollutants. We propose that under similar field conditions, S. tomentosa would be adversely affected, whereas S. terebinthifolius would thrive. On a long-term basis, this imbalance is likely to interfere in the vegetational composition and dynamics of the affected ecosystem.

Mobilization of arsenic (As) in the subsurface environment can result in elevated concentrations of As in groundwater and potential human exposure and adverse health effects. Natural attenuation (i.e., sequestration) of As may, under appropriate geochemical conditions, serve to limit human exposure to As. The effectiveness of As sequestration by sorption, co-precipitation, and/or precipitation can be strongly influenced by redox conditions, which can control the solubility of sorbent phases and the stability of As-containing solids. The redox transformation of As between the +III and +V oxidation states can also affect the extent of As sorption. The effect of amendment with synthetic manganese (Mn) oxide birnessite (nominally MnO₂) on As sequestration in a sediment suspension was examined in the absence and presence of iron (Fe) added as Fe(II). In the absence of Fe(II), the extent of As(III) oxidation to As(V) increased with increasing birnessite amendment, but As sequestration was not increased. In the presence of Fe(II), however, As sequestration did increase with increasing birnessite amendment. Concurrently, Fe(II) was also sequestered, and the Fe(III) content of the solid phase was observed to increase, suggesting that the oxidative precipitation of an Fe(III) oxyhydroxide phase plays an important role in As sequestration. These results suggest that amendment with Mn(III, IV) oxides could be an effective way to augment natural attenuation of As in cases where As-contaminated groundwater also contains elevated concentrations of Fe(II).

Mesostructured iron oxyhydroxide (FeO x ) and iron oxyhydroxide-phosphate (FeO x P) composites were organized using dodecylsulfate surfactant as a template. X-ray diffraction studies depicted a lamellar structure of the product. Ion exchange and solvent extraction methods were employed for the removal of the surfactant. Carboxylate ions exchanged lamellar type mesostructured material reorganized to a wormhole-like mesoporous material when heated under N₂ atmosphere. Surfactant was completely removed by carboxylate ions as observed by the Fourier transform infrared spectra. High surface area acetate-exchanged FeO x (230 m² g⁻¹) was obtained after the surfactant removal from the composite (2.8 m² g⁻¹). Surface area of acetate-exchanged FeO x P was the highest (240 m²g⁻¹) after the removal of the surfactant. Local structure of iron species of FeO x was investigated by X-ray absorption fine structure spectroscopy. Further, Fe···Fe bond appeared at 3.21-3.25 Å with coordination number 2-3, showing a high degree of un-saturation of Fe···Fe bonds. As compared with bulk iron oxyhydroxide and iron-intercalated montmorillonite, the mesoporous iron materials were highly effective for arsenic removal from low concentrations of aqueous solutions. Furthermore, mesoporous iron materials were stable in aqueous phase.

In this study, a high-rate fibre filter was used as a pre-treatment to stormwater in conjunction with in-line flocculation. The effect of operating the fibre filter with different packing densities (105, 115 and 125 kg/m³) and filtration velocities (20, 40, 60 m/h) with and without in-line flocculation was investigated. In-line flocculation was provided using 5, 10 and 15 mg/L of ferric chloride (FeCl₃·6H₂O). The filter performance was studied in terms of pressure drop (ΔP), solids removal efficiency, heavy metals (total) removal efficiency and total organic carbon (TOC) removal efficiency. It is found that the use of in-line flocculation at a dose of 15 mg/L improved the performance of fibre filter as measured by turbidity removal (95%), total suspended solids reduction (98%), colour removal efficiency (99%), TOC removal (reduced by 30-40 %) and total coliform removal (93%). The modified fouling index reduced from 750-950 to 12 s/L² proving that fibre filter can be an excellent pre-treatment to membrane filtration that may be consider as post-treatment. The removal efficiency of heavy metal was variable as their concentration in raw water was small. Even though the concentration of some of these metals such as iron, aluminium, copper and zinc were reduced, others like nickel, chromium and cadmium showed lower removal rates.