The software RCB-arsenic was developed previously to simulate the metalloid behavior in a constructed wetland (CW). The model simulates water flow and reactive transport by contemplating the major processes of arsenic (As) retention inside of CW. The objective of this study was to validate the RCB-arsenic model by simulating the behavior of horizontal flow CW for As removal from water. The model validation was made using data from a 122-day experiment. Two CWs prototypes were used: one planted with Eleocharis macrostachya (CW_planted) and another one unplanted (CW_unplanted) as a control. The prototypes were fed with synthetic water prepared using well water and sodium arsenite (NaAsO₂). In the RCB-arsenic model, a CW prototype was represented using a 2D mesh sized in accordance with the experiment. For simulation of As retention in CW, data addition was established in two stages that considered the mechanisms in the system: (1) aqueous complexation, precipitation/dissolution, and adsorption on granular media and (2) retention by plants: uptake (absorption) and rhizofiltration (adsorption). Simulation of As outlet (μg/L) in stage_1 was compared with CW_unplanted; the experimental mean was 40.79 ± 7.76 and the simulated 39.96 ± 6.32. As concentration (μg/L) in stage_2 was compared with CW_planted, the experimental mean was 9.34 ± 4.80 and the simulated 5.14 ± 0.72. The mass-balance simulation and experiment at 122 days of operation had a similar As retention rate (94 and 91%). The calibrated model RCB-arsenic adequately simulated the As retention in a CW; therefore, it constitutes a powerful tool of design.

Large-scale wastewater schemes rely on multi-barrier approach for the production of safe and sustainable recycled water. In multi-barrier wastewater reclamation systems, conventional activated sludge process (ASP) often constitutes a major initial treatment step. The main aim of this research was to determine most appropriate sampling approach to establish pathogen removal efficacy of ASP. The results suggest that ASP is capable of reducing human adenovirus (HAdV) and polyomavirus (HPyV) by up to 3 log₁₀. The virus removal data suggests that HAdV removal is comparable to somatic bacteriophage belonging to Microviridae family. Due to the high removal of Escherichia coli (>3 log₁₀) and very poor correlation with the enteric virus, it is not recommended that E. coli be used as a surrogate for enteric virus removal. The results also demonstrated no statistically significant differences (t test, P > 0.05) in calculated log removal values (LRVs) for HAdV, HPyV, and Microviridae from samples collected on hydraulic retention time (HRT) or simultaneous paired samples collected for influent and effluent. This indicates that a more practical approach of simultaneous sampling for influent and effluent could be used to determine pathogen removal efficiency of ASP. The results also suggest that a minimum of 10, preferably 20 samples, are required to fully capture variability in the removal of virus. In order to cover for the potential seasonal prevalence of viruses such as norovirus and rotavirus, sampling should be spread across all seasons.

Thirty-two chemical species were determined in PM₁₀ sampled at a suburban site on the north coast of Spain. Enrichment factors were applied to infer their soil/non-soil origin. The geochemical ratios were calculated using two databases: soil composition from locations in the surroundings of the sampling station and the Earth’s average upper-crust composition. In the present study, dissimilarities were found between the enrichment factors obtained using these two databases. Al, Ti, La and Ce were taken as the reference elements to normalise the data, reaching analogous conclusions. Bi, Cd, Cu, Sb, Se, Sn and Zn were associated with predominantly non-soil apportionments. As the relevance of soil/non-soil sources for the other analysed elements was found to be variable, they were probably of mixed origin. Furthermore, pairs of elements showed strong relationships, thus pointing to a common origin. Na–Mg and Co–Ni, with Pearson correlation coefficients above 0.9, were respectively related to marine and industrial apportionments. Enrichment factors have proved to be a useful tool to distinguish the soil/non-soil origin of chemical species present in airborne particulate matter. However, the choice of the reference database for soil composition considerably determined the accuracy of the conclusions.

This paper presents a bi-level optimization waste load allocation programming model under a fuzzy random environment to assist integrated river pollution control. Taking account of the leader-follower decision-making in the water function zones framework, the proposed approach examines the decision making feedback relationships and conflict coordination between the river basin authority and the regional Environmental Protection Agency (EPA) based on the Stackelberg-Nash equilibrium strategy. In the pollution control system, the river basin authority, as the leader, allocates equitable emissions rights to different subareas, and the then subarea EPA, as the followers, reallocates the limited resources to various functional zones to minimize pollution costs. This research also considers the uncertainty in the water pollution management, and the uncertain input information is expressed as fuzzy random variables. The proposed methodological approach is then applied to Tuojiang River in China and the bi-level linear programming model solutions are achieved using the Karush-Kuhn-Tucker condition. Based on the waste load allocation scheme results and various scenario analyses and discussion, some operational policies are proposed to assist decision makers (DMs) cope with waste load allocation problem for integrated river pollution control for the overall benefits.

The extensive oil exploration has led to a series of environmental issues in the Niger Delta, Nigeria, over the years. Aside from oil spill, insufficient wastewater treatment of oil refineries and the discharged effluents become another potential source of pollution that has not received enough attention from the government and the public. Through reviewing the current oil refinery wastewater treatment processes and the discharge standards of wastewater effluents in Nigeria, we aimed to raise the awareness of the shortcomings of the current wastewater treatment technology and to discuss the consequences of insufficient treatment to the environment. This article further discussed the use of nanotechnology as a potential upgrade to the conventional treatment technologies as it has shown its capacity of removing persistent organic pollutants (POPs) or converting hazardous components to environmentally friendly derivatives. It should also prove beneficial to the key stakeholders involved in the exploration of crude oil in the region to consider optimization of oil refinery wastewater treatment processes through integration of emerging technologies.

Cover systems are commonly placed over waste rock piles (WRPs) to limit atmospheric water and oxygen ingress and control the generation and release of acid mine drainage (AMD) to the receiving environment. Although covers containing geomembranes such as high-density polyethylene (HDPE) exhibit the attributes to be highly effective, there are few, if any, published studies monitoring their performance at full-scale WRPs. In 2011, a HDPE cover was installed over the Scotchtown Summit WRP in Nova Scotia, Canada, and extensive field performance monitoring was conducted over the next five years. A range of parameters within the atmosphere, cover, waste rock, groundwater and surface water, were monitored and integrated into a comprehensive hydrogeochemical conceptual model to assess (i) atmospheric ingress to the waste rock, (ii) waste rock acidity and depletion and (iii) evolution of groundwater and surface water quality. Results demonstrate that the cover is effective and meeting site closure objectives. Depletion in oxygen influx resulted in slower sulphide oxidation and AMD generation, while a significant reduction in water influx (i.e. 512 to 50 mm/year) resulted in diminished AMD release. Consistent improvements in groundwater quality (decrease in sulphate and metals; increase in pH) beneath and downgradient of the WRP were observed. Protection and/or significant improvement in surface water quality was evident in all surrounding watercourses due to the improved groundwater plume and elimination of contaminated runoff over previously exposed waste rock. A variably saturated flow and contaminant transport model is currently being developed to predict long-term cover system performance.

Within the framework of a study on the extent and history of marine pollution in the central area of Gabes Gulf, the concentrations of four trace metals (Cd, Cu, Pb, and Zn) were assessed in three different tissues of the seagrass species, Posidonia oceanica (leaves, rhizomes, and roots), in the mat of P. oceanica meadows at different depths from the sea floor (− 30 to − 150 cm) and in sediments. The results showed that P. oceanica leaves accumulate more Cd, Cu, and Zn, whereas Pb was found to be more concentrated in roots. The analysis of P. oceanica mat highlighted a clear decreasing gradient of trace metal concentrations from lower (− 30 cm) to higher (− 150 cm) depths. Considering that P. oceanica mat continuously rises above the initial level, with a rate of 1 m per century (~1 cm year⁻¹; Molinier and Picard Ann Inst Océanogr Fr 27:157–234, 1952), the latter observation suggested that the pollution level in Gabes Gulf increased continuously during the last few decades. The results of the P. oceanica mapping in the study area showed a continuous regression of its meadows as well as its local disappearance from various areas in the central part of Gabes Gulf. The current status of P. oceanica is most likely due to the cumulative effects of the discharges from the coastal industrial complex of Gabes-Ghannouche represented mainly by the phosphogypsum discharges. This study confirms the usefulness of P. oceanica not only as a bioindicator of the “health status” of coastal ecosystems but also as a record register tracing back the history and temporal evolution of coastal contamination level.

Controlling the corrosion of historical and archaeological ferrous metal objects presents a significant challenge to conservators. Chloride is a major corrosion accelerator in coastal areas for historic ferrous metal structures and for the many chloride-containing archaeological objects within museums. Corrosion reactions involve the formation of akaganéite (βFeOOH) which incorporates chloride within its crystal structure and adsorbs it onto its surface. The mobility of the surface-adsorbed chloride in aqueous systems and atmospheric moisture means βFeOOH can itself cause iron to corrode. The extraction of chloride from βFeOOH by aqueous Soxhlet hot wash and aqueous room temperature washing is measured. The impact of this washing on the ability of βFeOOH to corrode iron is quantitatively investigated by determining the oxygen consumption of unwashed, Soxhlet-washed and room temperature-washed samples of βFeOOH mixed with iron powder and exposed to 80 % relative humidity. This acts as a proxy measurement for the corrosion rate of iron. The results are discussed relative to climatic factors for outdoor heritage objects and the treatment of archaeological iron in museums. Delivering better understanding of the properties of βFeOOH supports the development of evidence-based treatments and management procedures in heritage conservation.

Cow bone char was investigated as sorbent for the defluoridation of aqueous solutions. The cow bone char was characterized in terms of its morphology, chemical composition, and functional groups present on the bone char surface using different analytical techniques: SEM, EDS, N₂-BET method, and FTIR. Batch equilibrium studies were performed for the bone chars prepared using different procedures. The highest sorption capacities for fluoride were obtained for the acid washed (q = 6.2 ± 0.5 mg/g) and Al-doped (q = 6.4 ± 0.3 mg/g) bone chars. Langmuir and Freundlich models fitted well the equilibrium sorption data. Fluoride removal rate in batch system is fast in the first 5 h, decreasing after this time until achieving equilibrium due to pore diffusion. The presence of carbonate and bicarbonate ions in the aqueous solution contributes to a decrease of the fluoride sorption capacity of the bone char by 79 and 31 %, respectively. Regeneration of the F-loaded bone char using 0.5 M NaOH solution leads to a sorption capacity for fluoride of 3.1 mg/g in the second loading cycle. Fluoride breakthrough curve obtained in a fixed-bed column presents an asymmetrical S-shaped form, with a slow approach of C/C ₀ → 1.0 due to pore diffusion phenomena. Considering the guideline value for drinking water of 1.5 mg F⁻/L, as recommended by World Health Organization, the service cycle for fluoride removal was of 71.0 h ([F⁻]fₑₑd ∼ 9 mg/L; flow rate = 1 mL/min; m ₛₒᵣbₑₙₜ = 12.6 g). A mass transfer model considering the pore diffusion was able to satisfactorily describe the experimental data obtained in batch and continuous systems.

Surface sediments were collected from three mangrove wetlands (Yifeng Xi, Shuanghan, and Su’ai Wan) in Shantou coastal zone of South China to investigate spatial distributions of polybrominated diphenyl ethers (PBDEs). The results demonstrate that PBDEs were detected in all the samples, indicating their widespread occurrence in coastal sediments of the studied area. Σ₉PBDEs (defined as the sum of nine targeted PBDE congeners except BDE-209) and BDE-209 are in the range of 2.3 to 11.5 and 16.7 to 58.2 ng/g, respectively. BDE-209 is the dominant PBDE congener in all sediment samples. The sediment concentrations of ∑₉PBDEs and BDE-209 among the three wetlands decrease in the order of Su’ai Wan > Shuanghan > Yifeng Xi. The concentrations of ∑₉PBDEs are higher in mangrove sediments than in mudflats, but no obvious regularity can be found on the correlation between mangrove species and PBDE levels in sediments. The contents of total organic carbon are moderately correlated with BDE-209 concentrations in sediments but not with ∑₉PBDE concentrations. The samples collected from different locations show slightly different composition profiles except BDE-209, with BDE-100 and BDE-47 being the pre-dominated congeners. The mudflats exhibit higher abundances of tri- to hexa-substituted congeners than the mangrove sediments. Ecological risk assessment demonstrates that the surface sediments from Shantou may pose a potential ecological risk of exposure to sediment-dwelling organisms.