The problem of current urban groundwater pollution is very serious, which has influenced social development and people’s daily life. Around the land-sea interface, tide obviously changes nearshore the groundwater flow regime and makes the pollutant migration process become more complex. In the present study, the effect of tide-induced groundwater table fluctuations and on the pollutants migration in beach aquifers is investigated by constructing a two-dimensional sand trough physical experimental model. The model considered brackish-water density differences and the tide by controlling experimental medium properties and boundary conditions. The results showed that the groundwater table fluctuation cycle is the same as the tidal cycle and the fluctuation lag time increases linearly with the increase of the offshore distance. Tidal fluctuation flattens brackish-freshwater interface, widens the dispersion zone, and generates the upper saline and the freshwater belt. Time lag corresponding relationships between saline water and tidal fluctuation was observed. With the pollutant approaching the saline water area, the profile of the pollutant migration is gradually developed into a spindle shape until the strip shape, and the pollutant enters the saline water body along the curved edge of the upper part of the saline water. The transverse dispersion of pollutants is larger than the longitudinal dispersion in a tidal cycle and its outline presents a strip shape development. No mixing or exchange between the pollutants and the saline water body happened during the whole process. This study can provide scientific references for nearshore groundwater pollution prevention and control in the future.

The research comprised of studying the effect composting sewage sludge with sawdust and vermicomposting with earthworm Eisenia fetida has on the degradation of 16 polycyclic aromatic hydrocarbons (PAHs). Raw rural sewage sludge prior composting was more contaminated with PAHs than urban sewage sludge, in both cases exceeding EU cutoff limits of 6 mg/kg established for land application. Dibenzo[a,h]anthracene (DBahAnt), acenaphtylene (Acy) and indeno[1,2,3-c,d]pyrene (IPyr) were predominant in rural sewage sludge, whilst the urban sewage sludge contained the highest concentrations of benzo[b]fluoranthene (BbFl), benzo[k]fluoranthene (BkFl) and indeno[1,2,3-c,d]pyrene (IPyr). Thirty days of composting with sawdust has caused a significant reduction of 16 PAHs on average from 26.07 to 4.01 mg/kg (84.6%). During vermicomposting, total PAH concentration decreased on average from 15.5 to 2.37 mg/kg (84.7%). Vermicomposting caused full degradation of hydrocarbons containing 2 and 6 rings and significant reduction of PAHs with 3 aromatic rings (94.4%) as well as with 5 aromatic rings (83.2%). The lowest rate of degradation (64.4%) was observed for hydrocarbons with 4 aromatic rings such as fluoranthene, benzo(a)anthracene, chrysene and pyrene. On the other hand, the highest level of degradation was determined for PAHs with 2 rings (100%), 3 rings (88%) and 6 aromatic rings in the molecule (86.9%) after composting with sawdust. Acenaphthene and pyrene were found to be the most resistant to biodegradation during both composting methods.

Hexavalent chromium (Cr(VI)) and dyes are of particular environmental concern and need to be removed from water urgently due to their high toxicity. Herein, we explored the possibility of electron transferring from dye Orange II (OII) to Cr(VI) under UV and simulated solar light irradiation, expecting to simultaneously decolorize dyes and reduce Cr(VI). Experimental results show that light irradiation can partially decolorize OII but has no ability to reduce Cr(VI) in solution only with OII or Cr(VI). However, both dyes and Cr(VI) can effectively and simultaneously be decolorized and reduced in the solution containing both OII and Cr(VI) under light irradiation, and a low pH level and high OII/Cr(VI) concentration ratio significantly favor the co-removal. Additionally, insoluble organo–Cr(III) complexes identified by FTIR and XPS characterization were generated during the reaction. These complexes are beneficial to the removal of chromium and total organic carbon from water. The possible degradation pathway of OII is further proposed based on the detection of degraded products by GC-MS analysis. The results of this work offer an approach for simultaneously removing multiple contaminants.

In this work, we examined the effect of two different organic wastes, composted sheep manure and coir, on the sorption, persistence, and mobility of three pesticides (alachlor, chlorfenvinphos, and chlorpyrifos) included as priority substances in European Directive 2013/39/EU. With this aim, leaching studies were conducted using disturbed soil columns filled with a typical agricultural soil (hipercalcic calcisol) from a semiarid area (southeastern Spain) to determine their potential for groundwater pollution. The three compounds were found in leachates of unamended soil although in different proportions: 53% (alachlor), 9% (chlorfenvinphos), and 6% (chlorpiryfos). The addition of organic wastes significantly increased the sorption of the studied pesticides. As a consequence, the half-lives of the studied pesticides were higher in amended than in unamended soils. A marked reduction of the amount recovered in leachates was observed in the amended soils, except for chlorpiryfos, whose recoveries barely changed. According to their potential groundwater pollution calculated as the groundwater ubiquity score (GUS) index, alachlor and chlorfenvinphos show medium leachability while chlorpiryfos is unlikely to leach.

In the recent decades, most rivers and lakes in the Taihu Basin have experienced degradation from an excess of nutrients. The presence of the nitrogen in water contributes to the increase of eutrophication. The riparian zones are associated with these watercourses and can effectively reduce any excess nitrogen. Soil denitrification is the most significant process in the transfer of nitrogen, which migrates from the terrestrial to the aquatic ecosystem. The relationship between soil denitrification and soil characteristics is well documented. However, the degree of soil denitrification and the main impact factors during different processes within the riparian zones due to gradual changes in the surroundings are not well understood. The present study selected four types of riparian soils that are contained in three different watersheds. The soil denitrification potential was determined within these soils using the acetylene block technique. The results indicate that, among the local factors studied, the soil denitrification potential increased with the intensity of anthropogenic activities, which varied significantly within the basin. This variation indicated a trend in the soil denitrification potential: cropland > woodland > grassland > bareland. Results suggest that soil moisture, nitrate-nitrogen concentration, and microbial biomass carbon concentration are the dominant factors that influence the riparian soil denitrification potential in the Tiaoxi watershed, while soil organic matter is the major factor for soil denitrification potential in the Hexi watershed and nitrate-nitrogen concentration is the dominant factor in the Tianmuhu watershed.

Regular monitoring of key water quality parameters is important for assessing the hydrological status of a lagoon and its management activities. In this study, a new cost-effective technique based on the geo-ecological information-modeling system (GIMS) is implemented employing the combined use of simulation experiments and in-field observations to investigate the problem of optimizing water quality monitoring of a lagoon. The GIMS is accompanied by 39 elements selected in 8 management systems and 31 functional elements, which are described in detail. It is shown that the combined use of model and field observations allows reliable recording of lagoon water quality and optimization of the monitoring regime. Finally, simulation experiments are presented, demonstrating the fidelity of the proposed modeling system to optimize water quality control through regular in-field measurements and simulations.

An airlift biofilm reactor was employed to study phenol biodegradation by Pseudomonas putida. Hydrodynamic tests were also conducted in a conventional column to facilitate the comparison of the dynamic behavior in different types of columns. The three-phase airlift column offered better aeration than the conventional column as liquid and solid circulation in the downcomer favored bubble breakup, increasing oxygen dissolved in the liquid phase and favoring the phenol biodegradation process. Kinetic parameters of phenol biodegradation by P. putida were obtained in an agitated batch reactor, with the initial phenol concentration varying from 10 to 750 mg/L. Experimental data were fitted using different microbial growth models found in literature. The Yano and Koga model, which considers the formation of multiple inactive enzyme–substrate complexes, fitted well with our experimental data, with a correlation coefficient, R ² = 0.952. An internal loop airlift bioreactor was used for aerobic phenol biodegradation in which polystyrene particles were utilized to support biomass immobilization. Several tests were performed by varying the influent phenol concentration, hydraulic retention time, upstream flow, and superficial air velocity. It was concluded that until an influent phenol concentration of approximately 300 mg/L, phenol acted as the limiting substrate. For higher phenol concentrations, oxygen became the limiting substrate. An increase in the oxygen concentration resulted in the complete consumption of phenol under high phenol concentration of 500 mg/L.

The presence of synthetic dyes in effluents leads to an environmental imbalance characterized by a decrease in photosynthetic activity and, therefore, a reduction of available oxygen, which affects all living aquatic species. To reduce this problem, a combination adsorption and biodegradation treatment strategy is proposed. In this work, Red 40 dye was adsorbed onto a low-cost waste product, followed by degradation by Trametes versicolor under solid state fermentation conditions. The principal aim of this research was to establish the best fermentation conditions using a kinetic evaluation of both degradation and laccase enzyme activity. The process was scaled-up using a rotating drum bioreactor. The best process conditions were a carbon:nitrogen ratio of 30:1, a moisture percentage of 75%, and an inductor concentration of 0.5 mM; the maximum dye degradation was 96.04%. Under these optimized conditions, the highest enzymatic activity was 8.49 U/gdₘ after 14 days of culture at the flask scale. Using a rotating drum bioreactor, 630 mg of azo dye was degraded after 30 days of culture. Red 40 dye degradation was confirmed using infrared spectroscopy Fourier transform infrared spectrometer and HPLC-MS techniques. The results show that the degradation percentage has a direct relation with laccase activity, and the obtained efficiency in the rotating drum bioreactor confirms the potential of this methodology for implementation at the industrial level.

Filter-based toxicology studies are conducted to establish the biological plausibility of the well-established health impacts associated with fine particulate matter (PM₂.₅) exposure. Ambient PM₂.₅ collected on filters is extracted into solution for toxicology applications, but frequently, characterization is nonexistent or only performed on filter-based PM₂.₅, without consideration of compositional differences that occur during the extraction processes. To date, the impact of making associations to measured components in ambient instead of extracted PM₂.₅ has not been investigated. Filter-based PM₂.₅ was collected at locations (n = 5) and detailed characterization of both ambient and extracted PM₂.₅ was performed. Alveolar macrophages (AMJ2-C11) were exposed (3, 24, and 48 h) to PM₂.₅ and the pro-inflammatory cytokine interleukin (IL)-6 was measured. IL-6 release differed significantly between PM₂.₅ collected from different locations; surprisingly, IL-6 release was highest following treatment with PM₂.₅ from the lowest ambient concentration location. IL-6 was negatively correlated with the sum of ambient metals analyzed, as well as with concentrations of specific constituents which have been previously associated with respiratory health effects. However, positive correlations of IL-6 with extracted concentrations indicated that the negative associations between IL-6 and ambient concentrations do not accurately represent the relationship between inflammation and PM₂.₅ exposure. Additionally, seven organic compounds had significant associations with IL-6 release when considering ambient concentrations, but they were not detected in the extracted solution. Basing inflammatory associations on ambient concentrations that are not necessarily representative of in vitro exposures creates misleading results; this study highlights the importance of characterizing extraction solutions to conduct accurate health impact research.

Forest fire is a natural disturbance that occurs in many terrestrial ecosystems specifically in the semi-arid environments and is considered to be an important cause of environmental change. Though many causes of fire are identified, including lightning, volcanic eruption, power line sparks, etc., human involvement is the most significant factor. Fire events are able to alter the physical, chemical and biogeochemical properties of the soil and surface materials and are able to release major and trace metals into the environment. This may be more significant in mining-affected and industrial landscapes, where elevated concentrations of metals present in the soil. After the fire event, metals become more mobile due to the increase in soil surface exposure and the mobility associated with ash dispersal. This mobility may increase the bioavailability of the metals, which may generate water quality issues and may contribute to human and environmental health concerns. Even though, the influences of fire on many soil properties are well established, the behaviour of metals with respect to fire is not well investigated. However, a few studies report that major and trace metals include Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, Zn and As are mobilized after fire with increased concentrations in soil and water resources and this might pose a risk to human health and ecosystems. Climate change may increase the intensity, frequency and areal extend of fire events and hence increase the metal concentrations and their potential health impacts. This paper reviews post-fire (wild fire) mobility of metals in soil common in contaminated forest ecosystems. The human and ecological health risks of these metals are also considered.