The freshwater polyculture pond culturing occupied an important position in the aquaculture industry. Accumulation of trace metals was investigated in water, sediments, and fish (Carassius auratus, Cyprinus carpio, Ctenopharyngodon idellus) from typical polyculture ponds in Chengdu, China. The results showed most of the pond water in Chengdu were safe for fish cultivation. The Cd and Cr concentrations in sediment samples from sites S3, S4, and S9 which were near the industrial park and road with a high traffic volume were higher than those of the other sites. Cu, Cr, Fe, Zn, Mn, Ni, and Pb in sediments were unpolluted, while Cd was unpolluted to moderately polluted due to anthropogenic activities. Cu, Cd, and Pb in fish pond sediment of Chengdu had higher potential mobility under normal environmental circumstances. The trace metal concentrations in liver of three fish species were all higher than those in muscle tissues. The order of bioaccumulation factor (BAF) values for trace metals was Cr > Cu > Pb > Zn > Cd > Ni > 20. The concentrations of Cu, Cd, Pb, Zn, and Cr in the muscle of three fish species were all below the local and international maximum permissible levels. The target hazard quotient (THQ) and hazard index (HI) of trace metals in aquaculture fish ponds in Chengdu were lower than 1, which indicated that the consumption of grass, crucian, and common carp cultivated in the aquaculture ponds of Chengdu pose no health risk to the residents.

Industrial hydrodesulfurization method has not been efficient for removal of dibenzothiophene (DBT) from petroleum distillates. Therefore, in this current study, adsorptive desulfurization (investigated in batch mode) was carried out using functionalized carbon nanotubes (FCNTs) to reduce the amount of DBT in a model diesel. Different techniques, such as, scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX), were used to check the morphological structure and the elemental compositions of the adsorbent; Fourier transmission infrared (FTIR) was used to check the chemical functionalities of the adsorbent; and nitrogen physisorption at 77 K was used to check the surface area, pore size, and pore volume of the adsorbent. The results show that the FCNTs outperformed the non-functionalized carbon nanotubes (CNTs) during the desulfurization by about 10%, indicating the functionalization did improve the desulfurization performance of the CNTs. The % removal of DBT by the FCNTs and CNTs was 70.48 and 60.88%, respectively. It can be concluded that the acid treatment of CNTs enhanced its surface affinity for DBT, thus contributing to the improved adsorption performance of the adsorbent. The isotherm results show that Freundlich isotherm model described well the mechanism of the adsorption process for both CNTs and FCNTs. In addition, pseudo second-order kinetics describes the behavior of the adsorbents during the adsorption process. The results obtained in this study therefore show that functionalized CNTs could be efficient and potential adsorbent for removal of DBT in petroleum distillate (e.g., diesel), to meet up with the stringent policies regarding emission of sulfur oxides.

Drought is the most complex climate-related disaster issue in South Asia, because of the various land-cover changes, vegetation dynamics, and climates. The aims of the current research work were to analyze the performance of AVHRR Normalized Difference Vegetation Index (NDVI) and spatiotemporal differences in vegetation dynamics on a seasonal basis by correlating the results with NASA’s MERRA precipitation and air temperature for monitoring vegetation dynamics and drought over South Asia. Our approach is based on the use of AVHRR NDVI data and NASA’s MERRA rainfall and air temperature data (1990–2011). Due to the low vegetation and dryness, the NDVI is more helpful in describing the drought condition in South Asia. There were rapid increases in NDVI, VHI, and VCI from April to October. Monthly NDVI, VHI, and VCI stabilize in September and improved once more in October and then show a declining trend in December. The monthly PCI, TCI, VHI, and VCI values showed that the South Asia goes through an extreme drought in 2000, which continues up to 2002, which lead the highest water stress. Spatial correlation maps among NDVI, precipitation, air temperature, VHI, and VCI on a seasonal basis. The correlation between NDVI and precipitation showed a significantly higher correlation value in JJA and SON seasons; the spatial correlation between NDVI and air temperature showed significant high values in DJF, JJA, and SON periods, while the correlation between VHI and TCI showed a significantly higher values in MAM and SON seasons, which indicated a good sign for dryness monitoring, mainly for farming regions during these seasons in South Asia. It was confirmed that these indexes are a comprehensive drought monitoring indicator and a step to monitoring the climate change in South Asia, which will play a relevant role ongoing studies on vegetation types, monitoring climate change, and drought over South Asia.

The study area within the Stone Town Nature Reserve in Ciężkowice encloses a variety of occurrences of sandstone tors exposed within the Skała Hill (Rock Hill) from its top down into the Biała River Valley. The efflorescences of salt minerals on the walls of the sandstone tors represent end products of weathering. Several types of the efflorescences have been distinguished in relation to their distribution, the composition of the parent sandstones and local conditions of the natural environment. Laboratory methods have allowed identifying several sulphate minerals of various hydration (mainly pickeringite, hexahydrite, pentahydrite, alunogen, K-alum, gypsum, syngenite). They occur as two morphological varieties: as accumulations of a millimetre large flakes or as granules. The development, diversification and distribution of the efflorescences depend first of all on the rock moisture controlled by its capillary rise. The dampness of the lower tor parts is relatively the major factor; thus, such places are the sites favouring efflorescing phenomena. The presence of sulphur-bearing ions that are contained in salt minerals may be attributed to oxidation of pyrite occurring in the sandstone formations in the vicinity of Ciężkowice but may also be associated with local waters, more probably with mineral ones than with groundwater recharged by atmospheric precipitations. Air pollution, particularly with sulphur compounds, should also be considered in weathering of sandstone tors and the formation of the efflorescences.

An in situ wet chemical deposition method has been applied for the successful surface modification of Ce (IV)-incorporated hydrous Fe(III) oxide (CIHFO) with a hydrophilic graphene precursor, graphene oxide (GO). The surface area of as-prepared composite (GO-CIHFO) has enhanced (189.57 m² g⁻¹) compared with that of pristine CIHFO (140.711 m² g⁻¹) and has irregular surface morphology consisting of microcrystals (~ 2–3 nm) and mesoporous (3.5486 nm) structure. The GO-CIHFO composite shows enhanced fluoride scavenging capacity (136.24 mg F g⁻¹) than GO (3 mg F g⁻¹) and pristine CIHFO (32.62 mg F g⁻¹) at pH 7.0. Also, in acidic pH range and at 323 K temperature, the Langmuir capacity of as-prepared composite is 190.61 mg F g⁻¹. It has been observed that fluoride removal by GO–CIHFO occurs from solutions obeying pseudo-second-order kinetics and multilayer adsorption process. The film/boundary layer diffusion process is also the rate-determining step. The nature of the adsorption reaction is reasonably spontaneous and endothermic in thermodynamic sense. It was observed that 1.2 g.L⁻¹ of GO-CIHFO dosage can effectively optimise the fluoride level of natural groundwater samples (9.05 mg L⁻¹) to the desirable permissible limit. Reactivation of used material up to a level of 73.77% with a solution of alkaline pH has proposed reusability of nanocomposites ensuring sustainability of the proposed material as fluoride scavenger in future.

Aquaculture in many coastal estuaries is threatened by diffuse sources of runoff from different land use activities. The poor performance of septic tank systems (STS), as well as runoff from agriculture, may contribute to the movement of contaminants through ground and surface waters to estuaries resulting in oyster contamination, and following their consumption, impacts to human health. In monitoring individual STS in sensitive locations, it is possible to show that nutrients and faecal contaminants are transported through the subsurface in sandy soils off-site with little attenuation. At the catchment scale however, there are always difficulties in discerning direct linkages between failing STS and water contamination due to processes such as effluent dilution, adsorption, precipitation and vegetative uptake. There is often substantial complexity in detecting and tracing effluent pathways from diffuse sources to water bodies in field studies. While source tracking as well as monitoring using tracers may assist in identifying potential pathways from STS to surface waters and estuaries, there are difficulties in scaling up from monitored individual systems to identify their contribution to the cumulative impact which may be apparent at the catchment scale. The processes which may be obvious through monitoring and dominate at the individual scale may be masked and not readily discernible at the catchment scale due to impacts from other land use activities.

Sludge treatment beds (STBs) have been used widely in many countries due to low energy consumption, low operating and maintenance costs, and better environmental compatibility. Penetration, evaporation, and transpiration are the main processes for sludge dewatering in STBs. However, the leachate quality from STBs usually cannot meet discharge limits. Moreover, such leachate has very low COD/N ratio, which makes it difficult to treat. In the present study, two subsurface flow (SSF) constructed wetlands (CWs) were investigated for the treatment of leachate from STBs under three different hydraulic retention time (HRT) (3 days, 4 days, 6 days), aiming for evaluating the effects of plants and HRT on treatment performance, as well as the potential of SSF CWs to treat sludge leachate with low COD/N ration. The results showed that plants play an important role in leachate treatment. The best treatment performance was achieved with HRT of 4 days. In this condition, the mean removal efficiencies of COD (chemical oxygen demand), NH₄⁺-N, TN (total nitrogen), and TP (total phosphorus) in the planted and the unplanted CWs were 61.6% (unplanted − 3.7%), 76.6% (unplanted 43.5%), 70% (unplanted 41%), and 65.6% (unplanted 6%), respectively. Heavy metal concentrations were below the Chinese integrated wastewater discharge standard during the experimental period in the planted CW, and the removal efficiencies in the planted CW system were higher than in the unplanted CW system. In all, planted SSF CWs can be an effective approach in removing leachate from sludge treatment beds. Furthermore, considering to temperature and seasonal variation, the leachate from STBs needs to be further studied in pilot- and full-scale condition.

In this study, the properties of unstable and stable flocs were investigated under the steady operation of a membrane bioreactor (MBR). The extracellular polymeric substances (EPS) composition, surface charge, and hydrophobicity of unstable and stable flocs were examined and compared. Interfacial interactions of the membrane with unstable flocs, unstable flocs themselves, and unstable and stable flocs were assessed using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) models. Cake layer resistance was found to contribute more than 80% of total resistance under steady operating conditions. Compared with stable flocs, unstable flocs possessed a higher level of EPS, more diverse protein, more negative charge, weaker hydrophobicity, and higher fouling potential. Thermodynamic analyses showed that unstable flocs had a higher adhesive strength (− 63.4 mJ/m²) with the membrane, lower self-cohesive strength (− 18.3 mJ/m²), and higher cohesive strength (− 54.3 mJ/m²) with stable flocs. Therefore, some unstable flocs remained on the membrane surface to form the cake layer due to their poor cohesion strength.

Efforts to improve sludge resource utilization have become increasingly important. In this study, humic acid (HA) was extracted from sludge samples collected from a sewage treatment plant, and then used for the adsorption of heavy metals. We used two-dimensional correlation spectroscopy (2D-COS) integrated with Fourier-transform infrared spectroscopy (FTIR) to explore the adsorption between sludge HA (HA) and three metal ions (Cu, Ni, and Pb). The resulting adsorbing data conformed to the isotherm of Langmuir adsorption. The maximum capacity values (qₘ) were 5.34, 1.49, and 26.29.8 mg/g for Cu, Ni, and Pb, respectively. The data from 2D-FTIR-COS analysis showed that the susceptibility of the functional group followed the order 2300 → 1130 → 1330 → 1480 → 1580 cm⁻¹ for Cu(II) and Ni(II), and 2300 → 1130 → 1330 → 1480 → 1200 → 1580 cm⁻¹ for Pb(II). The sludge HA with Pb(II) showed more adsorption sites than sludge HA with Cu(II) and Ni(II), and these adsorption sites could preferentially bond with Pb(II) at × 1 compared with Cu(II) and Ni(II). Our findings indicate that 2D-FTIR-COS technology has great potential for application as a useful tool for understanding the adsorption mechanism between adsorbents with heavy metals.

Bioconcentration factors (BCF) for regulatory purposes are usually determined by fish flow-through tests according to technical guidance document OECD 305. Fish bioconcentration studies are time consuming, expensive, and use many laboratory animals. The aim of this study was to investigate whether the freshwater amphipod Hyalella azteca can be used as an alternative test organism for bioconcentration studies. Fourteen substances of different hydrophobicity (log Kₒw 2.4–7.6) were tested under flow-through conditions to determine steady state and kinetic bioconcentration factors (BCFₛₛ and BCFₖ). The results were compared with fish BCF estimates for the same substances described in the literature to show the relationship between both values. Bioconcentration studies with the freshwater amphipod H. azteca resulted in BCF estimates which show a strong correlation with fish BCF values (r² = 0.69). Hyalella BCF values can be assessed in accordance with the regulatory B criterion (BCF > 2000, i.e., REACH) and thereby enable the prediction of B or non-B classification in the standard fish test. Therefore, H. azteca has a high potential to be used as alternative test organism to fish for bioconcentration studies.