This study compares the efficiency of a synthetic chelate (ethylenediaminetetraacetic acid-EDTA), a natural low-molecular-weight organic acid (citric acid), and their combination for phytoremediation of Cu-pyrene co-contaminated soils. Zea mays was grown in each soil and amended with citric acid and/or EDTA to understand the effect of chelates during phytoremediation of contaminated soils. In Cu or pyrene-contaminated soil, plant growth was negatively affected by EDTA (43 %) and citric acid (44 %), respectively, while EDTA + citric acid promoted (41 %) plant growth in co-contaminated soil. EDTA and EDTA + citric acid increased the phytoextraction of Cu in Cu-contaminated and co-contaminated soils, respectively. In pyrene-contaminated soil, all tested chelates increased the dissipation of pyrene reaching 90.4 % for citric acid, while in co-contaminated soil, only citric acid or EDTA + citric acid enhanced pyrene dissipation. These results show that Z. mays can be effective with the help of chelates in phytoextraction of Cu and dissipation of pyrene in co-contaminated soil.

Drainage water from acid sulfate soils with sulfuric material has high concentrations of protons and dissolved metals which can have detrimental effects on the surrounding ecosystems. Liming is expensive; therefore, alternative methods are needed. Organic materials such as plant residues, compost or biochars can bind protons and metals but have not been evaluated with respect to remediation of acid drainage water from acid sulfate soils. In this study, eight organic materials (compost, two straws and five biochars differing in feed stock and production temperature) were placed in small PVC cores at 1.5 g C/core and synthetic acid drainage water (pH 3, 28 mg Fe/l and 2 mg Al/l, properties based on long-term averages of drainage water from sulfuric acid sulfate soils) was applied in four leaching events. Mallee biochar produced at 550 °C and wheat biochar produced at 450 °C had high retention capacity for protons, Fe and Al. Retention was low in compost and wheat straw. Retention of protons was positively correlated with organic C concentration of the materials. Retention of Fe and Al was correlated with percentage alkyl, aryl and ketone groups. Other properties such as release of native Fe and Al and amount of material per core could explain differences in ability of organic materials to retain protons, Fe and Al. We conclude that some organic materials such as mallee biochar produced at 550 °C and wheat biochar produced at 450 °C could be used to remediate acidic drainage water.

Many products contain dyes, such as fabrics. However, most of the industry-generated waste is improperly handled, which causes serious environmental problems for the bodies of water that receive textile effluents. This study aimed to analyze the effect of biosorbents and biosorption techniques on decolorizing the textile azo dye Acid Blue 29 in an aqueous solution employing pine sawdust. Pine sawdust is low-cost substrate with minor environmental impact. A toxicity test was performed with Lactuca sativa seeds to determine the LC₅₀ of the dye. Subsequently, a biosorption test was performed to determine the toxicity of the resulting solutions. We observed that biosorption is a very feasible technique for the discoloration of the solutions and promotes reduction in their toxicity.

The dried powder of the alligator weed root (AWR) was employed as a biosorbent to remove As(III) from aqueous solution, using acid pre-treated AWR (HAWR) and As(V) as the contrasts. The results of batch adsorption experiment suggested that there is no substantial difference between As(III) and As(V) adsorption. Both of them are affected by the solution pH significantly, but insensitive to the ionic strength. The speciation analysis indicated that more than 95 % of the total As(III) in aqueous solution is oxidized into As(V) in the presence of AWR, while barely oxidized in the presence of HAWR. It proves that without pre-oxidation, AWR can oxidize and adsorb As(III), simultaneously. The properties of the biosorbent were characterized by various techniques including scanning electronic microscopy-energy dispersive spectrometer, Fourier transform infrared spectra analysis, inductive coupled plasma emission spectrometer and Zeta potential detection. The results suggested that typical metals including Mn, Fe and Al enrich in the morphology of metal (hydro) oxide over the surface of AWR, originally. Based on the nature of the biosorbent and arsenic besides the adsorption and oxidation performances, the metal (hydro) oxides are proved as the essential role to drive the adsorption and oxidation. The proof is that with the metal (hydro) oxides denuded, as the contrast of AWR, HAWR loses its capability of adsorption and oxidation for As(III), totally.

This study investigated drivers of denitrification and overall NO₃ ⁻ removal in an agricultural riparian area in central New York. Denitrification was measured using an in situ “push-pull” method with ¹⁵N–NO₃ ⁻ as a tracer during summer and fall 2011 at a pair of riparian sites characterized by different hydrologic regimes. Median denitrification rates were 1347 and 703 μg N kg soil⁻¹ day⁻¹ for the two study sites. These rates are higher than those reported for other riparian areas, emphasizing the role of some riparian areas as hotspots of NO₃ ⁻ removal. N₂O production was significantly higher at one site, demonstrating that riparian areas can be a greenhouse gas source under certain conditions. Denitrification was negatively correlated with groundwater flux, suggesting that slower flushing of water, and thus longer residence time, promotes denitrification. A mass balance of NO₃ ⁻ loss revealed that denitrification only accounted for 5–12 % of total NO₃ ⁻ loss, and production of NH₄ ⁺ indicated that dissimilatory NO₃ ⁻ reduction to NH₄ ⁺ (DNRA) may be occurring at both sites. While both sites were characterized by high NO₃ ⁻ removal, differences in denitrification rates and NO₃ ⁻ removal processes demonstrate the need to improve our ability to capture spatial and process heterogeneity in landscape biogeochemical models.

Submerged harbor steel structures often employ cathodic protection using galvanic anodes to guard against corrosion. A laboratory experiment, with three different cathodic protection configurations by galvanic aluminum-based anodes, was performed to evaluate the potential metal transfer from the anodic alloy dissolution into the surrounding marine water. The anode dissolution rate is proportional to the imposed current demands and induced a significant Al, In, and Zn transfer in the dissolved and particulate fractions of the corrosion product layers covering the anode surface. These layers were poorly adherent, even under low hydrodynamic conditions. Consequently, at the anode vicinity, the suspended particle matter and dissolved fraction of surrounding marine waters showed strong enrichments in Al and Zn, respectively, the values of which could potentially affect the adjacent biota. After the anode activation period, however, the metal inputs from galvanic anode dissolution are rapidly diluted by seawater renewal. At regional scale, these metal fluxes should be negligible compared to river and wastewater fluxes. These results also showed that it is difficult to assess the impact of the anode dissolution on the concentrations of metals in the natural environment, especially for metals included in trace amounts in the anode alloy (i.e., Cu, Fe, In, Mn, and Si) in the aquatic compartment.

Biosolids are a source of recycled organic matter and nutrients. To evaluate the impact of biosolids application (1984–2008) on soil quality, composite soils (Genesee silt loam, fine loamy, mixed, nonacid, and mesic typic udifluvent) were randomly sampled at geo-referenced sites from 0 (control), 2, 5, and 25 years of lime-stabilized anaerobically digested biosolid-applied fields. Results showed that microbial biomass C (Cₘᵢc), N (Nₘᵢc), and P (Pₘᵢc) contents were significantly higher at both depths of the 5 and 25 years of biosolid-applied fields compared to the control. Biosolid application significantly enlarged the biologically labile C (Cₘᵢc over total organic C, Cₘᵢc:Cₒᵣg) and N (Nₘᵢc over total N, Nₘᵢc:TN) pools with an associated decrease in metabolic C loss (20–53 %) by specific maintenance respiration (qCO₂) relative to the control. The Cₒᵣg, active (AC) and soluble C (SC), TN and reactive N (RN), and reactive P (RP) contents were significantly higher in the long-term biosolid-applied fields than in the control. However, there was an indication of leaching of SC, RN, and RP between depths. Years of biosolid application significantly increased soil moisture content (θ ᵥ at −0.03 MPa) by 20–40 %, macroaggregate stability (MaA) by 2–44 %, and mean weight diameter (MWD) of aggregates by 7–51 %, respectively. Consequently, there was a decrease in soil bulk density (ρ b) and microaggregate stability (MiA) at both depths. Results confirmed that biosolids application at rates recommended is a viable management option to improve soil quality for crop production. However, long-term and repeated biosolid applications above the recommended agronomic N and P rates may be responsible for accumulation and consequent leaching and runoff of SC, RN, and RP to cause groundwater and surface water pollution with environmental consequences.

In situ burning is a method by which oil is burned at a spill site under controlled conditions, and this method is subject to increased interest due to its applicability in the Arctic. This paper reviews the literature regarding the characterization and environmental effects of burn residues in Arctic waters. The results of a systematic literature search indicate that only a very limited number of studies have arctic pertinence. From the review, it is also indicated that the properties and composition of the residues depend on the efficiency of the burning and the oil type. Furthermore, the studies within the frame of the literature search reach consensus that in situ burning may increase the concentrations of large poly-aromatic hydrocarbons (PAHs; high ring number) while reducing small PAHs (low ring number). There are very few toxicity studies of burn residues on aquatic and arctic organisms, and to enhance the knowledge base, more organisms as well as oil types must be studied. Furthermore, there is a lack of studies investigating the potential effect of sinking burn residues on benthic organism and the smothering effects of the more viscous burn residues on birds and other organisms related to the sea surface. More knowledge regarding environmental fate and effect of residues is crucial to complete a robust net environmental benefit analysis prior to an oil spill response operation in arctic waters.

The objective of this study was to investigate the chemisorption mechanisms of Cu(II) on alcohol functionalized carbon nanotubes (OH-CNT) compared to granulated activated carbon (F-400). Two different sizes of OH-CNT were used on both adsorption isotherm experiments and continuous-flow fixed-bed columns. The experiments were conducted as a function of adsorbent type with fixed bed height (5 cm), fixed flow rate (0.035 mL/min), and one initial Cu(II) concentration (10 mg/L) at pH 5.1 and room temperature. Isotherm curves follow Freundlich model with better adsorption capacity for OH-CNT (6.3 and 15.7 mg/g) compared to F-400 (6.0 mg/g). Breakthrough curves for all adsorbents were typical, while OH-CNT showed higher capacity to treat water per amount of adsorbent than F-400. After 5 days of desorption, there was very little Cu(II) leached from the OH-CNT column as compared to F-400 that slowly desorbed 85 % of Cu(II). These results indicated chemisorption process on OH-CNT with low residual release of Cu(II) from adsorbent after reaching saturation. A systematic correlation method using converted FTIR absorbance curves (first derivative analysis) of as-received and hybrid OH-CNT identified new peaks on the spectra for Cu(II) chemisorbed on CNT surface, showing that Cu(II) target acidic functional groups during adsorption.

Long-term impacts of acidic deposition on the Great Smoky Mountains National Park (GRSM) include elevated inputs of sulfate, nitrate, and ammonium; the depletion of available nutrient cations from soil; and acidification of high-elevation streams. Critical loads and target loads (CLs/TLs) are useful tools to help guide future air quality management. We evaluated past and potential future effects of nitrate and sulfate deposition for 12 watersheds in the GRSM, USA, using the hydrochemical model, photosynthesis evapotranspiration biogeochemical (PnET-BGC). Two of the streams studied were listed by the state of Tennessee as impaired due to low stream pH. We reconstructed historical meteorological, atmospheric deposition, and land disturbance data for study watersheds for the period 1850 to present for model hindcasts. As future emissions are expected to decline, the model was run under a range of future scenarios from 2008 to 2200 of decreases in sulfate, nitrate, and ammonium and combinations of sulfate and nitrate deposition to estimate CLs and TLs of how watersheds might respond to emission control strategies. Model simulations of stream chemistry generally agreed with long-term (>10 years) observations. Model hindcasts indicate that watersheds in the GRSM are inherently sensitive to acidic deposition. Simulated mean projected stream ANC of 71 μeq/L (range 32 to 107 μeq/L) prior to industrial development (~1850) decreases in response to historical acidic deposition to 33 μeq/L (−13 to 88 μeq/L) in 2007. Future model projections show that decreases in sulfate deposition result in smaller increases in stream ANC compared with equivalent decreases in nitrate deposition; simultaneous controls on nitrate and sulfate deposition are more effective in ANC increases than individual control of nitrate or sulfate. Although there are no current programs in the USA to control ammonia emissions, model simulations suggest that decreases in ammonium deposition could also help mitigate acidification to a greater extent than equivalent controls on nitrate deposition.