The potential of natural Chinese zeolite to remove ammonium from rainfall runoff following urea applications to a paddy rice field is assessed in this study. Laboratory batch kinetic and isotherm experiments were carried out first to investigate the ammonium adsorption capacity of the natural zeolite. Field experiments using zeolite adsorption barriers installed at drain outlets in a paddy rice field were also carried out during natural rainfall events to evaluate the barrier’s dynamic removal capacity of ammonium. The results demonstrate that the adsorption kinetics are accurately described by the Elovich model, with a coefficient of determination (R ²) ranging from 0.9705 to 0.9709, whereas the adsorption isotherm results indicate that the Langmuir–Freundlich model provides the best fit (R ² = 0.992) for the equilibrium data. The field experiments show that both the flow rate and the barrier volume are important controls on ammonium removal from rainfall runoff. A low flow rate leads to a higher ammonium removal efficiency at the beginning of the tests, while a high flow rate leads to a higher quantity of ammonium adsorbed over the entire runoff process.

To demonstrate the variation and affecting factors of dissolved oxygen under different aeration strategies in polluted urban river sediment, simulation systems constructed with collected sediment and in situ overlaying water were aerated up or beneath the sediment-water interface 6 h day⁻¹ for 15 days. The results showed that aeration greatly altered the spatial pattern of DO in overlying water regardless of the way of treatment. Within the first 5 min of aeration, DO in overlying water increases rapidly from 0.86–3.13 mg L⁻¹ to the saturated range of 6.12–8.14 mg L⁻¹. During the first 5 days, aeration to water costed 5 min to reach the highest DO, while aeration to sediment costed 30 min to reach a lower highest level of DO in overlaying water. Analysis showed that DO was significantly negatively correlated with NO₂ ⁻-N and COD Mₙ , suggesting that DO was synergistically consumed by biochemical processes of organic matter degradation and nitrification. Aeration to sediment (ES group) and aeration to water (EW group) differently influenced nitrification and organic matter degradation. After daily aeration treatment, nitrification was the main oxygen-depleting process in EW group, especially after the action of the second stage of nitrification, where organic matter was probably largely degraded during aeration. However, in ES group, DO was consumed by both organic matter oxidation and nitrification processes.

In this study, batch experiments have been carried out to investigate the mechanism of fluoride uptake by layered double hydroxide (LDH) and calcined layered double hydroxide (CLDH). Furthermore, practical use of these synthetic minerals was studied in continuous mini-column experiments. In these column studies, groundwater from Ethiopia was tested. LDH and CLDH were synthesized with Mg/Al mole ratio of 2. From batch experimental study, LDH and CLDH have shown maximum removal capacity of 84 and 222 mg F⁻/g from aqueous solution, respectively. It was observed that fluoride removal was pH dependent with favorable pH range of 5–7 (max. at pH 6). The mechanism of removal is suggested to be ion exchange for LDH and a memory effect followed by surface precipitation reaction for CLDH. The presence of other anions lowered defluoridation capacity of LDH in the order of PO₄ ³⁻ > SO₄ ²⁻ > NO₃ ⁻ ≈ Cl⁻. From continuous experiments at 1 mM NaHCO₃, LDH showed maximum defluoridation capacity of 1.3 mg/g and CLDH up to 20 mg/g. It was also observed that increase of bicarbonate concentration to 10 mM lowered the fluoride uptake capacity of CLDH to 4 mg/g. The presence of 1 mM H₄SiO₄ further reduced fluoride uptake capacity to 3 mg/g. CLDH column tested with groundwater from the Rift Valley with 10.5 mg F⁻/L has shown maximum removal capacity of 2.2 mg F⁻/g. Regeneration of this column indicated that CLDH has a good potential to be re-used.

This work investigates the sorption behaviour of six hydrophobic organic compounds (HOCs) from the trichlorobenzenes (TCBs) and polycyclic aromatic hydrocarbons (PAHs) on Danube sediment using batch and column experiments, either in the presence or absence of carbon nanotubes (CNTs). For all HOCs investigated, nonlinear isotherms were obtained. Based on logKoc, it can be concluded that the Danube sediment has a higher sorption affinity for PAHs than TCBs. A positive correlation between HOC molecular hydrophobicity and sorption affinity was obtained, meaning that hydrophobic interactions play a significant role. There was a negative correlation between molecular hydrophobicity and the percentage of eluted HOCs, indicating that more hydrophobic molecules show less mobility in the sediment column. In the presence of CNTs in the sediment column, HOC concentrations in the column eluate decreased by factors of 2–3. Metal oxides and hydroxides on the surface of the sediment under the given experimental conditions had positively charged centres that caused the deposition of CNTs, leading to simultaneous sorption of organic compounds on both sediment organic matter (SOM) and CNTs. The increased retention of HOCs in the presence of CNTs on the sediment column reduces their mobility, which might also suggest that CNTs may be used for remediation of contaminated soils and sediments.

This study evaluates the present day effects of air pollutants emitted from an iron sintering plant near Wawa (Ontario, Canada) decades ago (1939–1998). During smelting and refining of iron ore, gaseous sulfur-rich emissions and large amounts of metal-containing (iron oxides) particulate materials were released in to the air, and eventually settled onto vegetation and soil cover. We test the feasibility of using magnetic measurements to investigate and quantify the soil pollution resulting from the sintering plant. Surface and subsurface magnetic susceptibility measurements, as well as various magnetic mineral properties, have been collected in a scheme designed to mimic the previously determined pollutant contamination zones. A total of 50 sites were sampled (with a sampling grid of 250 m) within and around the smelter kill zone to the northwest of Wawa. Results were plotted on cross sections perpendicular (X-X′) and parallel (Y-Y′) to the dominant wind direction in order to investigate magnetic properties of the soil samples as a function of both wind direction and distance from the source. Samples located in Rao and LeBlanc’s (The Bryologist 70:141–17, 1967) pollution zones 1 and 2 typically have κ ᵢₙ₋ₛᵢₜᵤ values >120 × 10⁻⁵ SI, while the zone 3 and 4 results are <100 × 10⁻⁵ SI. Magnetic susceptibility enhancements at depths of 5–10 cm were found to be related to the presence of magnetic spherules (fly-ashes) at sites on the wind-parallel Y-Y′ profile in the previously defined kill zone. An estimated minimum migration rate of iron-rich particulates is calculated for coarse sand and silt/clay sites as 0.24 and 0.1 cm/year, respectively.

In this study, the effects of exposure to engineered nickel oxide (NiO 40–60 nm) and cobalt oxide (CoO <100 nm) nanoparticles (NP) were investigated on Artemia salina. Aggregation and stability of the aqueous NP suspensions were characterized by DLS and TEM. Acute exposure was conducted on nauplii (larvae) in seawater in a concentration range from 0.2 to 50 mg/L NPs for 24 h (short term) and 96 h (long term). The hydrodynamic diameters of NiO and CoO NPs in exposure medium were larger than those estimated by TEM. Accumulation rate of NiO NPs were found to be four times higher than that of CoO NPs under the same experimental conditions. Examinations under phase contrast microscope showed that the nanoparticles accumulated in the intestine of Artemia, which increased with increasing exposure concentration. Differences were observed in the extent of dissolution of the NPs in the seawater. The CoO NPs dissolved significantly while NiO NPs were relatively more stable. Oxidative stress induced by the NP suspensions was measured by malondialdehyde assay. Suspensions of NiO NPs caused higher oxidative stress on nauplii than those of CoO NPs. The results imply that CoO and NiO NPs exhibit toxicity on Artemia (e.g., zooplankton) that is an important source of food in aquatic food chain.

The study delineates the investigation to determine the adsorption and desorption behaviour of Pretilachlor in three soils of Punjab with varying physicochemical characteristics using batch equilibration techniques. Kinetics of adsorption followed a pseudo-second-order model (R ² > 0.99) and adsorption–desorption data fitted well to the Freundlich equation for the three soils. L-type isotherms were obtained for the adsorption process, which indicated high affinity between Pretilachlor and adsorption sites. The magnitude of logK Fₐdₛ values for the three soils ranged from 0.887–1.226 μg¹⁻¹/ⁿ g⁻¹ mL¹/ⁿ and the order of adsorption was clay loam > sandy loam > loamy sand. Desorption of Pretilachlor was concentration dependent and in three desorption cycles ranged from 5.04 to 56.03 % in loamy sand, 3.14 to 23.12 % in sandy loam and 1.63 to 18.64 % in clay loam soil indicative of difficulty in the release of strongly adsorbed Pretilachlor. The removal of organic matter by hydrogen peroxide (H₂O₂) oxidation increased the adsorption of Pretilachlor in three Punjab soils. Pretilachlor desorption was hysteretic in the original as well as H₂O₂-treated soils. It could therefore be concluded that the adsorption was controlled by clay minerals and desorption of Pretilachlor in soils was controlled by the organic matter.

The use of reclaimed water (RW) for irrigation alleviates agricultural water shortages. However, N₂O emissions and N fertilizer transformations in soils irrigated with RW under different N fertilizer types and soil moisture contents are poorly understood. A 216-h laboratory incubation experiment was conducted to evaluate the effects of irrigation water types (RW and fresh water, FW), N fertilizer types (¹⁵N-labeled KNO₃ and (NH₄)₂SO₄), and soil moisture contents at 40, 60, and 90 % water-filled pore space (WFPS) on N₂O emissions and N fertilizer transformations in intact soil cores. The results showed that cumulative N₂O emissions ranged from 3.78 to 36.30 mg N m⁻², and fertilizer-derived N₂O losses accounted for 0.14–2.44 % of N fertilizers, while fertilizer-derived N residues (NO₃ ⁻-N + NH₄ ⁺-N) accounted for 10.16–26.95 % of N fertilizers. The N₂O emissions at 40 % WFPS and fertilizer-derived N residues at 60 % WFPS in soils irrigated with RW were significantly (10.98 and 20.95 %, respectively) higher than those irrigated with FW, while fertilizer-derived N₂O losses at 60 % WFPS in soils irrigated with RW were 10.26 % higher than those irrigated with FW. The N₂O emissions and fertilizer-derived N₂O losses in soils amended with (NH₄)₂SO₄ at 40 and 60 % WFPS were significantly (26.61–178.84 %) larger than those amended with KNO₃, while fertilizer-derived N residues in soils amended with KNO₃ were significantly (41.47 %) higher than those amended with (NH₄)₂SO₄. The N₂O emissions significantly increased with increasing soil moisture content. Our results indicate that N fertilizer types and soil moisture contents are the two important factors regulating N₂O emissions and N fertilizer transformations. When RW irrigation is used, controlling soil moisture contents within 41 and 60 % WFPS (the optimum is 46 % WFPS) and application of KNO₃ can reduce N₂O emissions and fertilizer-derived N₂O losses, and correspondingly increase fertilizer-derived N residues, which can contribute to climate change mitigation.

The presence of insecticides in the waterways of the municipality of Ouro Branco, MG, Southeastern Brazil, has become a public health problem. Recent research correlates the presence of these toxins in the water to the high indexes for hypertension and abortions occurring in the rural area. These insecticide residues are only slightly concentrated in the water, and as such, it is necessary to search for and optimize analytic methods that are capable of detecting these very low concentrations. To define the method that presents the best detectability for the organochlorine chlorpyrifos, one of the most used pesticides in the area, sample extraction techniques such as liquid–liquid extraction with low temperature partition (LLE-LTP) and headspace solid-phase microextraction (HS-SPME) were used, followed by gas chromatography analysis with electron capture detection (GC-ECD). Full factorial design 2⁴ and the Doehlert matrix were used to optimize both extraction techniques. The results displayed that HS-SPME-GC-ECD was the method that presented the best performance for determining the presence of chlorpyrifos in the water. The optimum condition was defined at the extraction time and temperature of 60 min and 85 °C, respectively, with a sample volume of 11 mL and Na₂HPO₄ concentration of 0.04 mol/L. The optimized method was validated for the principal figures of merit. The method displayed linearity with R ² equal to 0.992 and detection limit (LOD) and quantification limit (LOQ) of 0.50 and 1.67 μg/L, respectively. The results indicate that the HS-SPME-GC-ECD technique proposed is efficient for determining the presence of chlorpyrifos in water, and analyses of the collected sample indicated the presence of chlorpyrifos in water bodies in the rural zone of Ouro Branco in concentrations within detection and quantification limits.

The fate of emerging organic micropollutants (EOMs) in wastewater treatment plants (WWTPs) is still not fully determined, and further studies are still needed to assess whether the existing treatment units can be further exploited (e.g., by modifying the operating parameters) or new and different techniques have to be implemented for their removal. The present study investigates the fate of a class of EOMs, i.e., the endocrine disrupting chemicals (EDCs), in batch-activated sludge tests under mixed and aerated conditions, as those usually adopted in full-scale WWTPs. Among the EDCs, the research focused on: bisphenol A, 17α-ethinylestradiol (EE2), and two natural EDCs—estrone (E1) and 17β-estradiol (E2). By applying different operating conditions to the tests, it was possible to distinguish between contributions due to volatilization, adsorption onto the sludge flocs, and biodegradation to the overall removal of each EDC. It was found that all the investigated EDCs were removed mainly by adsorption and biodegradation. Starting from a relatively high concentration (1000 ng/L), the removal process was capable of reducing the influent load to very low values within the duration of the test (i.e., 48 h). Kinetics of the removal process were found to be best fitted by the pseudo-second-order model for all the investigated EDCs; the values of the relative constants were always found to be equal to about 0.0023 1/h. Furthermore, the values of the coefficients K D and K OM were determined and found to be comparable with the data reported by the specialized literature.