The important effects of minerogenic particles delivered from watersheds on optical and phosphorus metrics of lacustrine water quality have recently been quantified through measurements of the projected area of these particles per unit volume of water (PAVₘ), using an individual particle analysis technique. A mass balance type model for PAVₘ, partitioned according to the contributions of four size classes, is developed and tested for Cayuga Lake, New York, supported by long-term monitoring of PAVₘ in the lake and its primary tributaries. The model represents the source of PAVₘ of tributary inputs and three in-lake loss processes: (1) size-dependent settling, (2) enhancement of settling through aggregation, and (3) filter feeding by dreissenid mussels. The central roles of major runoff events and localized external loads of minerogenic sediment at one end of the lake in driving patterns of PAVₘ in time and space are successfully simulated, including (1) the higher PAVₘ levels in a shallow area (“shelf”) adjoining these inputs, relative to pelagic waters, following runoff events; and (2) the positive dependence of the shelf increases on the magnitude of the event. Analyses conducted with the model establish that settling, with aggregation enhancement, dominates the loss of PAVₘ from the water column of the shelf, while mussel filtration increases in relative importance in pelagic waters. The utility of PAVₘ predictions to quantify the effects of these particles on optical and phosphorus concentration metrics of water quality is established.

This paper has its origin via an inadvertent error wherein a length of rubber hose was added to the sampling line of a sulphur gas analyser at the Australian Baseline Station at Cape Grim. This carbon disulphide (CS₂) contamination source was removed after a period of 10 weeks. In the interim, substantial data was collected and is here compared with the record of ambient station temperatures. CS₂ was found to vary with ambient temperature over both short and monthly time scales. Comparisons of linear, natural log (ln) and log₁₀ correlations yield the conclusion that log₁₀ and ln CS₂ emission vs. temperature (°C) associations provide the best correlations. No significant depletion of CS₂ emission from the rubber over a 10-week period was detected. Implications for regional and global emission inventories of CS₂ and carbonylsulphide (COS) are discussed.

This study investigated the effects of various soil conditions, including drying-rewetting, nitrogen deposition, and temperature rise, on the quantities and the composition of dissolved organic matter leached from forest and wetland soils. A set of forest and wetland soils with and without the nitrogen deposition were incubated in the growth chambers under three different temperatures. The moisture contents were kept constant, except for two-week drying intervals. Comparisons between the original and the treated samples revealed that drying-rewetting was a crucial environmental factor driving changes in the amount of dissolved organic carbon (DOC). The DOC was also notably increased by the nitrogen deposition to the dry forest soil and was affected by the temperature of the dry wetland soil. A parallel factor (PARAFAC) analysis identified three sub-fractions of the fluorescent dissolved organic matter (FDOM) from the fluorescence excitation–emission matrices (EEMs), and their compositions depended on drying-rewetting. The data as a whole, including the DOC and PARAFAC components and other optical indices, were possibly explained by the two main variables, which were closely related with the PARAFAC components and DOC based on principal component analysis (PCA). Our results suggested that the DOC and PARAFAC component information could provide a comprehensive interpretation of the changes in the soil-leached DOM in response to the different environmental conditions.

Biodegradable polymer poly(3-hydroxybutyrate) (P3HB) has been used as a matrix to construct slow-release formulations of the fungicide tebuconazole (TEB). P3HB/TEB systems constructed as films and pellets have been studied using differential scanning calorimetry, X-ray structure analysis, and Fourier transform infrared spectroscopy. TEB release from the experimental formulations has been studied in aqueous and soil laboratory systems. In the soil with known composition of microbial community, polymer was degraded, and TEB release after 35 days reached 60 and 36 % from films and pellets, respectively. That was 1.23 and 1.8 times more than the amount released to the water after 60 days in a sterile aqueous system. Incubation of P3HB/TEB films and pellets in the soil stimulated development of P3HB-degrading microorganisms of the genera Pseudomonas, Stenotrophomonas, Variovorax, and Streptomyces. Experiments with phytopathogenic fungi F. moniliforme and F. solani showed that the experimental P3HB/TEB formulations had antifungal activity comparable with that of free TEB.

Emissions of nitrous oxide (N₂O) from wetland ecosystems are globally significant and have recently received increased attention. However, relatively few direct studies of these emissions in response to water depth-related changes in sediment ecosystems have been conducted, despite the likely role they play as hotspots of N₂O production. We investigated depth-related differential responses of the dissolved inorganic nitrogen distribution in Phragmites australis (Cav.) Trin. ex Steud. rhizosphere versus non-rhizosphere sediments to determine if they accelerated N₂O emissions and the release of inorganic nitrogen. Changes in static water depth and P. australis growth both had the potential to disrupt the distribution of porewater dissolved NH₄⁺, NO₃⁻, and NO₂⁻ in profiles, and NO₃⁻ had strong surface aggregation tendency and decreased significantly with depth. Conversely, the highest NO₂⁻ contents were observed in deep water and the lowest in shallow water in the P. australis rhizosphere. When compared with NO₃⁻, NH₄⁺, and NO₂⁻, fluxes from the rhizosphere were more sensitive to the effects of water depth, and both fluxes increased significantly at a depth of more than 1 m. Similarly, N₂O emissions were obviously accelerated with increasing depth, although those from the rhizosphere were more readily controlled by P. australis. Pearson’s correlation analysis showed that water depth was significantly related to N₂O emission and NO₂⁻ fluxes, and N₂O emissions were also strongly dependent on NO₂⁻ fluxes (r = 0.491, p < 0.05). The results presented herein provide new insights into inorganic nitrogen biogeochemical cycles in freshwater sediment ecosystems.

In recent years, high concentrations of hexavalent chromium, Cr(VI), have been observed in the groundwater system of the Asopos River Basin, raising public concern regarding the quality of drinking and irrigation water. The work described herein focuses on the development of a groundwater flow and Cr(VI) transport model using hydrologic, geologic, and water quality data collected from various sources. An important dataset for this goal comprised an extensive time series of Cr(VI) concentrations at various locations that provided an indication of areas of high concentration and also served as model calibration locations. Two main sources of Cr(VI) contamination were considered in the area: anthropogenic contamination originating from Cr-rich industrial wastes buried or injected into the aquifer and geogenic contamination from the leaching process of ophiolitic rocks. The aquifer’s response under climatic change scenario A2 was also investigated for the next two decades. Under this scenario, it is expected that rainfall, and thus infiltration, will decrease by 7.7 % during the winter and 15 % during the summer periods. The results for two sub-scenarios (linear and variable precipitation reduction) that were implemented based on A2 show that the impact on the study aquifer is moderate, resulting in a mean level decrease less than 1 m in both cases. The drier climatic conditions resulted in higher Cr(VI) concentrations, especially around the industrial areas.

Brazil is an important country within the global mineral industry. The main reserves of phosphate rock in Brazil are contained in the states of Goiás and Minas Gerais, at the Catalão and Tapira cities, respectively. Atmospheric inputs due to the mining of phosphate rock may have various effects on human health in areas near these types of mines. Thus, this work evaluated the influence of phosphate mining on the chemical composition and annual atmospheric deposition in Catalão (GO) and Tapira (MG), Brazil. The pH of rainwater was 6.90 in Catalão and 6.80 in Tapira. The ionic concentrations (in μeq/L) at both study sites decreased in the following order: Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ for cations and HCO₃ ⁻ > NO₃ ⁻ > SO₄ ²⁻ > PO₄ ³⁻ > F⁻ > Cl⁻ for anions. High Ca²⁺ content indicates that Ca²⁺ contributes to the neutralisation of the rainwater pH in both of the areas studied. The annual atmospheric deposition of NO₃ ⁻ and SO₄ ²⁻ can be attributed to the use of diesel-powered trucks in and around mining areas. Soil dust derived is responsible for the annual atmospheric deposition of Na⁺ and K⁺. Phosphate mining activities are the main source of the annual atmospheric deposition of PO₄ ³⁻ and F⁻.

This study evaluated the resistance to wind erosion of a consolidated soil layer (CSL) using an indoor wind tunnel under simulated wind erosion conditions. The CSL consisted of the experimental soil (classified as a sandy soil), fly ash (FA) at two addition rates (10 and 20 % (w/w) soil), and polyacrylamide (PAM) at two addition rates (0.05 and 0.1 % (w/w) soil). Prior to the wind tunnel experiments, according to the different addition rates of FA and PAM, the sandy soil, FA, and PAM were homogeneously mixed by spraying an appropriate amount of deionized water to form different CSLs. The moisture content of the CSL was balanced to that of the sandy soil in the field. The threshold wind speeds and wind erosion amounts of different CSLs at two wind speeds of 8 and 14 m/s were measured, respectively. The results showed that the threshold wind speed of the sandy soil was significantly increased due to the formation of CSL by FA and PAM, exhibiting an increasing trend with increasing addition rate of FA and PAM. The wind erosion amounts of different CSLs were all decreased when compared with that of the sandy soil. The resistance to wind erosion of the CSL consisting of 10 % FA and 0.1 % PAM was strongest at a wind speed of 8 m/s, while only slight wind erosion occurred after 30-min exposure to the wind with a speed of 14 m/s.

The effect of titanium dioxide nanoparticles (TiO₂ NPs) on biological wastewater treatment in a sequencing batch reactor was investigated. The overall removal of chemical oxygen demand (COD) and NH₄ ⁺-N were relatively unaffected; efficiencies remained at >95 % and around 99 %, respectively, after 30 days of continuous exposure to the NPs. However, TiO₂ NPs resulted in increased conversion of NO₂ ⁻-N to NO₃ ⁻-N and caused slight inhibition effect on denitrification, with the total nitrogen removal reduced from 95 to 90 %. Several shifts in the bacteria community composition were noted. However, the overall community structure and biodiversity remained relatively unchanged. The polysaccharide content in the extracellular polymeric substances (EPS) was generally unaffected, suggesting a low potential of substantial shock or damage that may result in cytoplasmic leakage. However, a decrease in protein content occurred and indicated the inhibitive effects of the NPs. TiO₂ NPs were removed in the system mainly via deposition into the sludge. The removal efficiency decreased from 90 to 70 % after 4 weeks, due to sorption saturation as well as the change in the EPS content of the activated sludge.

Selective adsorption of Pb(II) and Cr(VI) by surfactant-modified and unmodified zeolites is discussed in this paper. The influences of pH, ionic strength, temperature, and adsorption time on Cr(VI) and Pb(II) adsorption are studied, The characteristics of the surface and inner structures of zeolites before and after modification are analyzed through infrared spectroscopy, scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller analysis, and zeta potential measurement. Results show that the characteristics of electric charge on the zeolite surface had changed after modification, which resulted in selective adsorption of Cr(VI) and Pb(II). Moreover, kinetic study reveals that adsorption by the different zeolites coincides with the Langmuir model and pseudo-second-order kinetic equation. The intraparticle diffusion equation proves that the Cr(VI) adsorption is mainly electrostatic, whereas Pb(II) adsorption proceeds via intrapore and electrostatic adsorption on the zeolite surface. This difference in mechanisms endows selectivity of metal ion adsorption by the modified zeolites. This study provides a reference on zeolite modification for use in various applications, such as wastewater treatment.