Quantifying plant biomass and related processes such as element allocation is a major challenge at the scale of entire riparian zones. We applied sub-decimetre-resolution (5 cm) remote sensing using an unmanned aircraft system (UAS) in combination with field sampling to quantify riparian vegetation biomass at three locations (320-m river stretches) along a mining-impacted boreal river and estimated the amounts of Cd, Cu, and Zn stored in the dominant species. A species-level vegetation map was derived from visual interpretation of aerial images acquired using the UAS and field sampling to determine species composition and cover. Herbaceous and shrub biomass and metal contents were assessed by combining the vegetation maps with field sampling results. Riparian zone productivity decreased from 9.5 to 5.4 t ha⁻¹with increasing distance from the source of contamination, and the total amount of vegetation-bound Cd and Zn decreased from 24 to 0.4 and 3,488 to 211 g, respectively. Most Cu was stored at the central location. Biomass and metal contents indicated large variation between species. Salix spp. comprised only 17 % of the total dominant-species biomass but contained 95 % of all Cd and 65 % of all Zn. In contrast, Carex rostrata/vesicaria comprised 64 % of the total dominant-species biomass and contained 63 % of all Cu and 25 % of all Zn. Our study demonstrates the applicability of UAS for monitoring entire riparian zones. The method offers great potential for accurately assessing nutrient and trace element cycling in the riparian zone and for planning potential phytoremediation measures in polluted areas.

In view of the fatal illnesses caused by methylene blue (MB) which is contained in the dye wastewater, the present study focused on the use of natural sunlight in heterogeneous photocatalysis to decolorize and degrade MB. The present study also investigated the effects of enhancers (hydrogen peroxide and persulfate ion) and inhibitors (chloride and carbonate ions) on photodecolorization of MB. Pseudo-first-order rate constants for each studied effect were determined through Langmuir-Hinshelwood model. The recommended conditions to photodecolorize 60 ppm of MB under natural sunlight were 1.0 g/L of titanium dioxide nanopowder at initial pH 10.5 in order to achieve 85.3 % decolorization (rate constant of 10.8 × 10⁻³ min⁻¹). The addition of 4,080 ppm of hydrogen peroxide and persulfate ion significantly enhanced the decolorization efficiency up to 96.6 and 99.3 %, respectively (rate constants of 66.2 and 91.0 × 10⁻³ min⁻¹, respectively). However, the addition of 2,000 ppm of chloride and carbonate ions reduced the decolorization efficiency of MB to 74.7 and 70.2 %, respectively (rate constants of 7.8 and 7.3 × 10⁻³ min⁻¹, respectively). The present study implied that it was possible to use natural sunlight as a light source for photocatalytic treatment of dye in tropical countries like Malaysia.

Effect of biochar, derived from unfertilized dates, on the immobilization of Cd and Ni, in a sandy loam alkaline soil, was investigated. The biochar was applied to the soil columns at the rate of 0.5, 1, and 2 % (w/w) artificially polluted with 10 mg kg⁻¹Cd and 100 mg kg⁻¹Ni. After 1 month incubation of soil-biochar mixture under ambient conditions, the soil bulk density was reduced by 0.19 g cm⁻³as compared with no biochar addition with increase in soil pH. A reduction of 53 % in the NH₄NO₃-extractable soil Ni was recorded as compared with the corresponding control without biochar addition. After incubation, the water-soluble Ni and NH₄NO₃-extractable soil Cd and Ni contents were significantly lower in all the biochar treatments than the control. A reduction of 53 % in the NH₄NO₃-extractable soil Ni was recorded as compared with the corresponding control. The biochar content separated from the incubated soil showed low concentrations of NH₄NO₃-extractable Cd and Ni. The total Ni and Cd contents recovered from biochar samples after incubation were 35.2 and 3.7 mg kg⁻¹, respectively. Their contents in soil were substantially reduced by the incorporation of biochar amendment (114 to 57.2 mg kg⁻¹Ni, 9 to 5.6 kg⁻¹Cd) as compared with the no-biochar control. Therefore, addition of the biochar improved the soil physical properties and succeeded in immobilizing the studied metals.

In this study, an artificial neural networks (ANN) model was developed to predict the removal of a polycyclic aromatic hydrocarbon (PAH), namely, naphthalene from marine oily wastewater by using UV irradiation. The removal rate was used as model output and simulated as a function of five independent input variables, including fluence rate, salinity, temperature, initial concentration and reaction time. The configuration of the ANN model was optimized as a three-layer feed-forward Levenberg–Marquardt backpropagation network with log-sigmoid and linear transfer functions at the hidden (12 hidden neurons) and output layers, respectively. By considering goodness-of-fit and cross validated predictability, the ANN model was trained to provide good overall agreement with experimental results with a slope of 0.97 and a correlation of determination (R ²) of 0.943. Sensitivity analysis revealed that fluence rate and temperature were the most influential variables, followed by reaction time, salinity and initial concentration. The findings of this study showed that neural network modeling could effectively predict the behavior of the photo-induced PAH degradation process.

Lacustrine sedimentation and trace metal accumulation are naturally occurring processes that can be altered by anthropogenic activities. Indices of sediment or metal dynamics are important for the management and operational use of man-made reservoirs and their drainage basins. In this study, we compared two reservoirs in Virginia, USA, to quantify the effect of varying watershed characteristics on sediment and metal fluxes. Lake Pelham is a human-impacted reservoir surrounded by agricultural fields and anthropogenic developments, whereas Lake Moomaw is an undeveloped reservoir surrounded by moderate to extremely sloping forested landscapes. Three sediment cores were taken from each reservoir to estimate²¹⁰Pb-based sediment accumulation rates, organic matter content, and indices of trace metal enrichment and accumulation. The average²¹⁰Pb-based sediment accumulation rates were 0.348 ± 0.053 and 0.246 ± 0.043 g cm⁻² year⁻¹for Lake Pelham and Lake Moomaw, respectively. The sediment trace metal results showed strong correlation with sediment organic content, and both reservoirs had moderate to high enrichment of Cu and little enrichment of Zn and Pb. Overall, Lake Moomaw had relatively low sediment accumulation and metal enrichment. Comparatively, Lake Pelham had significantly greater metal concentrations, which were highest in the upper reaches of the reservoir. Lake Pelham also had higher sediment accumulation rates and higher metal enrichment, reflecting the impact of human development within the greater watershed. Results from this study suggest that urbanization can increase reservoir sediment and metal fluxes, but atmospheric deposition is also important in forested watersheds that have not undergone anthropogenic land-use change.

The genotoxic effects of four heavy metal mixtures on Drosophila melanogaster were investigated with reference to gene expressions of heat shock proteins (HSP26, HSP60, HSP70 and HSP83), DNA profiles, and mitochondrial NADH dehydrogenase sequence. Adult D. melanogaster flies were treated with a mixture of four (Fe, Cu, Cd and Pb) heavy metals (HMs) in three different concentrations, which were selected based on one higher dose (HM3) and one lower dose (HM1) relative to the permitted limits (HM2) in drinking water at 1st, 5th and 10th days. It was determined that the amount of the accumulated heavy metals and the expressions of the HSP genes were changed with increasing exposure time. The accumulations of Cd and Pb were increased with increasing exposure time; additionally, the HSP expression patterns were determined as HSP70 > HSP60 > HSP26 > HSP83 HM1 (5th day), HM2 (5th day and 10th day), and HM3 (all exposure times). It was also determined that the application of the heavy metal mixture affected the random amplified polymorphic DNA (RAPD) profiles and the mitochondrial NADH dehydrogenase sequence of D. melanogaster. The highest base pair changes (9 bp) were determined at the HM2 concentration (permissible limits in drinking water) on the 1st day of treatment. Therefore, it was shown that mixture of four heavy metals caused a genotoxic effect and D. melanogaster is a useful model organism for heavy metal-induced genotoxicity studies.

US National Ambient Air Quality Standards (NAAQS) are based on quantitative linkages between ambient air concentrations and an effects indicator. Critical loads (CLs) can provide quantitative information on safe levels of atmospheric deposition to aquatic systems, but CLs cannot be directly used in the NAAQS context because they are not expressed in terms of atmospheric concentrations. Here, we describe the aquatic acidification index (AAI) model that incorporates CL concepts and relates atmospheric nitrogen and sulfur concentrations to an acid neutralizing capacity (ANC) effects indicator (Fig. 1). The AAI estimates the potential surface water ANC associated with a set of atmospheric concentrations of nitrogen and sulfur and a region's biogeochemical and hydrological attributes by combining steady-state CL modeling with air quality modeling outputs. Initial applications of the AAI model yielded results consistent with well-recognized spatial patterns of acid-sensitive aquatic systems. Furthermore, the response of AAI predictions to future year changes in NO ₓ and SO ₓ emissions suggest that planned national emission reduction strategies designed to reduce ozone and particulate matter air pollution will produce increases in surface water ANC.

Natural clinoptilolite from Zlatokop deposit, Serbia, was activated by microwave irradiations (10 min, 550 W) and its adsorptive efficiency for removal of crystal violet (CV) dye from aqueous solution was investigated. The process variables were specified by response surface method and the central composite design (CCD). Percentage of dye removal as a function of two numeric factors (the amount of zeolite and the concentration of crystal violet) with five values (rotatibility factor α = 0. 41) and one numeric factor (contact or agitation time) with three values (rotatibility factor α = 1. 00) at dynamic ambient conditions and pH = 6 was tested. The optimal conditions for 91.99 % decolorization were predicted to be 2 g of the zeolite in 100 ml of CV aqueous solution with concentration of 250 mg/l, and contact time of 678 s. The model was validated experimentally. Two isotherm models—Langmuir type 2 and Freundlich could describe the adsorption process with high correlation to experimental data. The calculated adsorbent capacity from the CCD (12.625 mg/g) showed a good agreement with the adsorption capacity obtained by Langmuir-2 isotherm (13.477 mg/g) and with pseudo-second-order kinetic model (12.404 mg/g).

Preliminary analysis on dredged marine sediments from Benoi basin in Singapore was carried out showing elevated concentrations of Zn, Cu, Pb, Cd, Cr and Ni. Ethylenediamine tetraacetic acid (EDTA) thermal washing experiments were conducted for heavy metal extraction at temperature 100 °C. Results indicated the significant efficiency of thermal washing to extract Pb, Zn and Ni. However, there was little or no influence in the removal of Cu and Cr and a slight effect to Cd indicating multiple mechanisms. In addition, agitation was found to have great influence on the removal efficiency of heavy metals as experiments without agitation performed lesser or no extraction due to limited contact of the washing solution and the dredged sediment. Sequencing processes of thermal treatment followed by EDTA washing showed limited performance, likely due to thermal stabilization of the contaminants particularly at low liquid-to-soil (L/S) ratio. Furthermore, sequential extraction analysis on the metal speciation was performed before and after thermal washing. It was revealed that metals mainly extracted from fractions bound to carbonates and Fe-Mn oxides, the relative mobile fraction. On the contrary, metals in the residual fraction displayed a considerable stability.