The effects of various experimental parameters on adsorption of Zn2+ metal ion from its aqueous solution by castor seed hull and also by activated carbon have been investigated using batch adsorption experiments. It has been found that the amount of zinc adsorbed per unit mass of the hull increases with the initial metal ion concentration, contact time, solution pH and with the amount of the adsorbent. Kinetic experiments clearly indicate that adsorption of zinc on both castor hull and activated carbon is a three-step process—a rapid adsorption of the metal ion, a transition phase, and an almost flat plateau. This has also been confirmed by the intraparticle diffusion model. It has also been found that the zinc adsorption process followed pseudo-second order kinetics. The kinetic parameters including rate constants have been determined at different initial metal ion concentration, pH, amount, and type of adsorbent, respectively. The Langmuir and Freundlich adsorption isotherm models have been used to interpret the equilibrium adsorption data. The Langmuir model yields better correlation coefficients. The monolayer adsorption capacities (q m) of castor hull and activated carbon have been compared with those for others reported in the literature. The value of separation factor (R L) derived from the Langmuir model gives an indication of favorable adsorption. Finally, from comparative studies, it has been found that castor hull is a potentially attractive adsorbent as compared to commercial activated carbon for the removal of zinc from aqueus effluents.

Acid rock drainage (ARD) often contains ferrous iron, sulphate and high concentrations of trace elements detrimental to the environment. Future costs will be enormous if the problem is not treated today. Simple and cost-effective methods for remediation of historical mine sites are therefore desired. In this study, three mine waters were mixed with alkaline ash leachates, and the fate of trace elements from both the mine waters (Cd, Cu, Pb, Zn, Ni and Co) and the ash leachates (Cr and Mo) was studied. Addition of ash water precipitates hydrous ferric oxides (HFO) and hydrous aluminium oxides (HAO) induced trace element sorption and coprecipitation. Composition of the formed HFO/HAO mix determines efficiency of the sorption and the relative order of sorption for different trace elements. Sorption occurred much earlier (often one pH unit or more) in a system with high iron concentrations compared to systems with lower iron concentrations. Removal of cadmium and zinc was low, below pH 8, if the amount of precipitates was low. Using ash for generation of alkaline water may be a problem with regard to chromium and molybdenum. This study shows that it is possible to avoid problems with molybdenum by keeping the final pH around 7, and chromium(VI) from the ash water will be reduced into chromium(III) and precipitated as the hydroxide in the presence of iron(II). Results imply that it is possible to also use fly ashes in alkaline leach beds in order to neutralize ARD followed by precipitation and sorption of trace elements.

This paper focuses on the influence of uranium tailing piles on the contamination of their immediate surroundings. The monitoring was carried out on arable land near Pribram in Central Bohemia, Czech Republic. The monitored arable land is located 600 m northeast of the bottom of the piles. In addition, the high uranium (U) content in the topsoil ranged from 40 to 220 ppm. A former portion of it was found in an exchangeable fraction (49%). Both of these facts make this land unsuitable for agricultural use. The sequential extraction discovered a shift in the U content among sample spots situated in and outside the path of the predominant wind direction. In the first group, uranium binds mainly to Fe/Mn oxides, while in the other samples, U is accumulated in the more mobilizable fractions.

Contamination of metal ions in soil and water represents more pressing threats to resources as well as human health. The present research was carried out to screen the phytosequester plants growing in industrial waste- and wastewater-affected industrial areas of Okhla, New Delhi, India. Accumulation trend of metal Fe, Zn, Cu, Cr, Pb, Cd, Hg, and As from soil and wastewater by plants were collected for study. Among aquatic plants Hydrilla verticillata, Marsilea quadrifolia, and Ipomea aquatica were found to be highest metals accumulator, Eclipta alba and Sesbania cannabina among terrestrial plant were highest accumulator of metals. Among the algal spp. Spirulina platensis and Phormidium papyraceum were the most efficient in accumulating Cd and Hg. The maximum bioconcentration factor (BCF) was recorded in Hygroryza aristata for the metals (Hg, Cd) in M. quadrifolia (Cd, Cr), in E. alba (Cr, Cu), and in S. platensis (Hg, Pb). However, the translocation factor (TF) of metals was found more in M. quadrifolia followed by I. aquatica than other plants. Among all the plants, H. verticillata showed high TF and low BCF values for toxic metals (Pb, Cr) and was suitable for phytostabilization of these metals. Our study showed that native plant species growing on contaminated sites may have a potential of phytosequestration of these metals.

Many studies were conducted measuring the lethal concentration of pollutants by using a contaminated solution or polluted sediments. Considering the impact of polluted food on mortality and uptake quantity of invertebrate shredders in batch cultures, little is known about, e.g. uranium and cadmium. Consequently, we investigated in situ the impact of metal and metalloid polluted food and water on Gammarus pulex L. under nature-like conditions. In contrast to other publications, a very low mortality rate of the invertebrates was found. Furthermore, fixation of elements by G. pulex was shown to be low compared to initial concentrations. Fixation of non essential metals and metalloids is shown to take place mainly on the surface of the invertebrates. This is deduced from easy desorption of a relevant amount of fixed metals and metalloids. It is concluded that the accumulation of metals and metalloids in situ under nature-like conditions within the food web via invertebrate shredders is very low. The invertebrates seem to minimize the uptake of non essential elements in the presence of nutrient-rich food even in habitats with higher contamination levels. Hence, invertebrates seem to be adapted to higher contamination levels in their favourable habitats.

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants produced by incomplete combustion sources such as home heating, biomass burning, and vehicle emissions. PAH concentrations in soils are influenced by source inputs and environmental factors that control loss processes and soil retention. Many studies have found higher concentrations of these pollutants in soils within cities of temperate climates that have a centralized urban core. Less is known about the factors regulating PAH abundance in warm, arid urban ecosystems with low population densities but high traffic volumes. The relative importance of sources such as motor vehicle traffic load and aridland ecosystem characteristics, including temperature, silt, and soil organic matter (SOM) were explored as factors regulating PAH concentrations in soils near highways across the metropolitan area of Phoenix, AZ (USA). Highway traffic is high compared with other cities, with an average of 155,000 vehicles/day. Soils contained low but variable amounts of SOM (median 2.8 ±â€‰1.8% standard deviation). Across the city, median PAH concentrations in soil were low relative to other cities, 523 ±â€‰1,886 μg/kg, ranging from 67 to 10,117 μg/kg. Diagnostic ratio analyses confirmed that the source of PAHs is predominantly fuel combustion (i.e., vehicle emissions) rather than petrogenic, biogenic, or other combustion sources (coal, wood burning). However, in a multiple regression analysis including traffic characteristics and soil properties, SOM content was the variable most strongly related to PAH concentrations. Our research suggests that dryland soil characteristics play an important role in the retention of PAH compounds in soils of arid cities.

Mining activities generate spoils and effluents with extremely high metal concentrations of heavy metals that might have adverse effects on ecosystems and human health. Therefore, information on soil and plant metal concentrations is needed to assess the severity of the pollution and develop a strategy for soil reclamation such as phytoremediation. Here, we studied soils and vegetation in three heavily contaminated sites with potential toxic metals and metalloids (Zn, Pb, Cd, As, TI) in the mining district of Les Malines in the Languedoc region (southern France). Extremely high concentrations were found at different places such as the Les Aviniéres tailing basins (up to 160,000 mg kg–1 Zn, 90,000 mg kg–1 Pb, 9,700 mg kg–1 of As and 245 mg kg–1 of Tl) near a former furnace. Metal contamination extended several kilometres away from the mine sites probably because of the transport of toxic mining residues by wind and water. Spontaneous vegetation growing on the three mine sites was highly diversified and included 116 plant species. The vegetation cover consisted of species also found in non-contaminated soils, some of which have been shown to be metal-tolerant ecotypes (Festuca arvernensis, Koeleria vallesiana and Armeria arenaria) and several Zn, Cd and Tl hyperaccumulators such as Anthyllis vulneraria, Thlaspi caerulescens, Iberis intermedia and Silene latifolia. This latter species was highlighted as a new thallium hyperaccumulator, accumulating nearly 1,500 mg kg–1. These species represent a patrimonial interest for their potential use for the phytoremediation of toxic metal-polluted areas.

Fluid catalytic cracking unit is of great importance in petroleum refining industries as it treats heavy fractions from various process units to produce light ends (valuable products). FCC unit feedstock consists of heavy hydrocarbon with high sulfur contents, and the catalyst in use is zeolite impregnated with rare earth metals, i.e., lanthanum and cerium. Catalytic cracking reaction takes place at elevated temperature in fluidized bed reactor generating sulfur-contaminated coke on the catalyst with large quantity of attrited catalyst fines. In the regenerator, coke is completely burnt producing SO2, PM emissions. The impact of the FCC unit is assessed in the immediate neighborhood of the refinery. Year-long emission inventories for both SO2 and PM have been prepared for one of the major petroleum refining industry in Kuwait. The corresponding comprehensive meteorological data are obtained and preprocessed using Aermet (Aermod preprocessor). US EPA approved dispersion model, Aermod, is used to predict ground level concentrations of both pollutants in the selected study area. Model output is validated with measured values at discrete receptors, and an extensive parametric study has been conducted using three scenarios, stack diameter, stack height, and emission rate. It is noticed that stack diameter has no effect on ground level concentration, as stack exit velocity is a function of stack diameter. With the increase in stack height, the predicted concentrations decrease showing an inverse relation. The influence of the emission rate is linearly related to the computed ground level concentrations.

Daily mass concentrations of PM1, PM2.5, and PM10 were measured along with meteorological parameters from October 2008 to October 2009 in the city of Elche, close to the southeastern Spanish Mediterranean coast. Annual mean levels of 9.2, 13.2, and 26.2 μg m−3 were obtained for PM1, PM2.5, and PM10, respectively. PM2.5 and PM10 concentrations were lower than those previously measured at the same location due to unusual weather conditions that occurred during winter 2009, specially the decrease in the number of high atmospheric stability episodes. The contribution of road traffic to the levels of submicron (PM1), fine (PM2.5–1), and coarse (PM10–2.5) particles was studied by correlating PM concentrations with NO2. The results showed a higher relative contribution in winter (0.45 < r < 0.65) than in summer (−0.26 < r < 0.05). However, the scarce variability in traffic intensity (in terms of number of vehicles per day) was unable to explain daily and seasonal variations in PM levels. Rather, these variations were associated to seasonal changes in other PM sources and meteorological conditions. The three size fractions showed good negative correlations with wind speed during winter, suggesting that the main effect of cold season winds was the dilution of atmospheric aerosols. For the coarse fraction, good correlation coefficients were obtained with temperature and solar radiation (0.60 and 0.70, respectively) due to identical seasonal behavior of coarse PM and these parameters during the study period.

Pot culture experiments were conducted to study the remediation potentials of a newly found accumulator Kalimeris integrifolia Turcz. ex DC. under different cadmium (Cd) concentrations with same fertilizer level, as well as the same Cd dose under different fertilizer doses. At medium (100 g/kg) chicken manure level, Cd concentrations in roots, stems, leaves, inflorescences, and shoots of K. integrifolia grown in the soils contaminated with 2.5, 5, 10, and 25 mg/kg Cd significantly decreased (p < 0.05) in average by 23.8%, 29.9%, 24.0%, 30.1%, and 38.6%, respectively, when compared to those of the pots without addition of chicken manure. In contrast, the medium urea amendment level (1 g/kg) showed no effect on the bioaccumulated Cd concentrations of K. integrifolia regardless of the spiked Cd doses. However, Cd extraction capacities (micrograms per pot) of K. integrifolia shoots were significantly increased (p < 0.05) due to the gain in biomass (more than one- to twofolds) by the soil fertilizing effect of urea and chicken manure. Particularly, Cd extraction capacities (micrograms per pot) of K. integrifolia shoots amended by urea were higher than that of chicken manure. Under the condition of 25 mg/kg Cd addition, shoot biomasses of K. integrifolia were significantly increased (p < 0.05) with the amendment of chicken manure (50, 100, and 200 g/kg) and urea (0.5, 1, and 2 g/kg). As a result, the Cd extraction capacities (micrograms per pot) were increased in treatments even though soil extractable Cd concentrations were significantly decreased (p < 0.05) by amendment with chicken manure and maintained by urea addition. For practical application concerns, chicken manure is better used as phytostabilization amendment owing to its reducing role to extractable heavy metal in soil, and urea is better for phytoextraction.