Heavy metal accumulation in soils at three field sites subject to effluent irrigation

Three field sites were chosen to study the environmental assimilative capacity of heavy metals in soil. These sites were the Werribee Farm and the Myome Farm in Australia and Shenyang Zhangshi Irrigation Area in China. The Werribee Farm and the Shenyang Zhangshi Irrigation Area received sewage treatment and application on land for a long time. The Myome farm is an experimental site in which investigations on land application of municipal wastewater on water repellent soils is currently being trailed. Heavy metal contamination, in particular Cr, Cu and Zn, in the Land Filtration soil of Werribee Farm was widespread. More than a century of sewage irrigation has occurred in the Werribee Farm. The temporal distribution pattern of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in the soil at this site follow an exponential trend with time and the spatial distribution pattern of accumulation of heavy metals in different paddocks correlates with the number of years of sewage irrigation at that site in the Farm. Extensive sewage irrigation at Shenyang Zhangshi Irrigation Area resulted in significant Cd pollution in soil-plant (rice) system and poses a significant threat to the health of local people. Even after eight years since cessation of sewage irrigation, the bioavailable fractions of Cd in the soil as analyzed by sequential extraction techniques were very high thus illustrating long-term persistence. The simultaneous competitive adsorption of metals in water repellent soils (at Myome Farm in South Australia) was studied. In the competitive situation, Cr, Pb and Cu are the heavy metal cations more strongly adsorbed by the soil, whereas Cd, Ni and Zn are the least adsorbed. The increase in Freundlich adsorption capacity by clay amendment suggested that clayed soils are capable sorption of higher heavy metal loadings compared to the non-clayed water repellent soil, which is more vulnerable to heavy metal inputs. A simple model of environmental assimilative capacity is proposed. The results of comparison of the three field sites shows that the Werribee Farm has a higher environmental assimilative capacity of heavy metals in soil than the soils at Shenyang Zhangshi Irrigation Area and Myome Farm, however heavy metal contamination at Werribee Farm is still a concern. The model of environmental assimilative capacity of heavy metals in soil is an effective tool to assist management of effluent applied land irrigation systems and can be used to better design environmental engineering systems.

Pop, heavy metal and the blues: secondary analysis of persistent organic pollutants (POP), heavy metals and depressive symptoms in the NHANES National Epidemiological Survey

Persistent environmental pollutants, including heavy metals and persistent organic pollutants (POPs), have a ubiquitous presence. Many of these pollutants affect neurobiological processes, either accidentally or by design. The aim of this study was to explore the associations between assayed measures of POPs and heavy metals and depressive symptoms. We hypothesised that higher levels of pollutants and metals would be associated with depressive symptoms.

Arsenic and heavy metal contamination of rice, pulses and vegetables grown in Samta village, Bangladesh

Arsenic contaminated water from tube wells has become the major health problem threatening millions of people in Bangladesh. However, the arsenic (As) contaminated water is not just used for drinking, it is used to irrigate crops, and to wash and prepare food. Contamination of agricultural soils by long-term irrigation with As contaminated water can lead to contamination and phyto-accumulation of the food crops with As and other toxic metals. As a consequence, dietary exposure to As and other toxic metals may contribute substantially to the adverse health effects caused by the contaminated tube wells in Bangladesh. Various vegetables, rice, pulses and the grass pea were sampled in Samta village in the Jessore district of Bangladesh and screened for As, Cd, Cu, Pb and Zn by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. These local food crops provide the majority of the nutritional intake of the people in this area and are of great importance to their overall health. In general, our data show the potential for some vegetables to accumulate heavy metals with concentrations of Pb greater than Cd. The concentrations of As and Cd were higher in vegetables than in rice and pulses. The concentration of Pb was generally higher in rice than in pulses and vegetables. However, some vegetables such as bottle ground leaf, ghotkol, taro, eddoe and elephant foot had much higher concentrations of Pb. Other leafy and root vegetables contained higher concentrations oJ2n and Cu. Rice grown at Samta had increased Pb and As, but, considering an average daily intake of only 260 g rice per person per day, only the Pb is at concentrations which would be a health hazard/or human consumption.

Arsenic and heavy metal contamination of vegetables grown in Samta village, Bangladesh

Drinking of arsenic (As) contaminated well water has become a serious threat to the health of many millions in Bangladesh. However, the implications of contamination of agricultural soils from long-term irrigation with As-contaminated groundwater for phyto-accumulation in food crops, and thence dietary exposure to As, and other metals, has not been assessed previously in Bangladesh. Various vegetables were sampled in Samta village in the Jessore district of Bangladesh, and screened for As, Cd, Pb, Cu and Zn by inductively coupled plasma emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). These local food products are the basis of human nutrition in this region and of great relevance to human health. The results revealed that the individual vegetables containing the highest mean As concentrations (μg g⁻¹) are snake gourd (0.489), ghotkol (0.446), taro (0.440), green papaya (0.389), elephant foot (0.338) and Bottle ground leaf (0.306), respectively. The As concentration in fleshy vegetable material is low. In general, the data show the potential for some vegetables to accumulate heavy metals with concentrations of Pb greater than Cd. Some vegetables such as bottle ground leaf, ghotkol, taro, eddoe and elephant foot had much higher concentrations of Pb. Other leafy and root vegetables, contained higher concentrations of Zn and Cu. Bioconcentration factors (BCF) values, based on dry weight, were below 1 for all metals. In most cases, BCF values decreased with increasing metal concentrations in the soil. From the heavily As-contaminated village in Samta, BCF values for As in ladies finger, potato, ash gourd, brinjal, green papaya, ghotkol and snake gourd were 0.001, 0.006, 0.006, 0.014, 0.030, 0.034 and 0.038, respectively. Considering the average daily intake of fresh vegetables per person per day is only 130 g, all the vegetables grown at Samta had Pb concentrations that would be a health hazard for human consumption. Although the total As in the vegetables was less than the recommended maximum intake of As, it still provides a significant additional source of As in the diet.

Heavy metal concentrations in wild and cultured blacklip abalone (haliotis rubra Leach) from southern Australian waters

The concentrations of 12 trace metals were assessed in wild and cultured specimens of blacklip abalone, Haliotis rubra, from each of two sites, Geelong and Port Fairy, in Victoria, Australia. Cadmium, copper, iron and zinc were quantified in the foot muscle of specimens from all four populations but the concentrations of aluminium, arsenic, beryllium, chromium, lead, manganese, nickel and vanadium were below the detection limits of the instrumental techniques employed. When similar sized specimens from each population were compared, the concentrations of each of the quantifiable metals varied according to location. The Geelong wild population had the highest or equal highest concentrations of each metal. Metal concentrations in the wild populations were usually greater than or equal to the concentrations in the corresponding cultured population. The concentrations of the regulated essential elements, copper and zinc, decreased with an increase in abalone length whereas the concentrations of iron, manganese and cadmium were independent of length. Metal concentrations in H. rubra from all sites complied with the Australian Food Code and other standards of food safety.

Improved extraction of heavy metal ions using membrane technology

Investigates tha application of polymer membranes in industrial wastewater treatment. Several novel membrane systems have been developed. The new systems overcome the problems of low extractant capacity and slow rate of extraction of the traditional membrane system. These new systems offer significant scope for the treatment of industrial wastewater containing heavy metal ions.

Spectroscopic and computational characterizations of alkaline-earth- and heavy-metal-exchanged natrolites

Synchrotron infrared (IR) and micro-Raman spectra of natrolites containing alkaline-earth ions (Ca2+, Sr2+, and Ba2+) and heavy metals (Cd2+, Pb2+, and Ag+) as extra-framework cations (EFCs) were measured under ambient conditions. Complementing our previous spectroscopic investigations of natrolites with monovalent alkali metal (Li+, Na+, K+, Rb +, and Cs+) EFCs, we establish a correlation between the redshifts of the frequencies of the 4-ring and helical 8-ring units and the size of the EFCs in natrolite. Through ab initio calculations we have derived structural models of Ca2+- and Ag+-exchanged natrolites with hydrogen atoms, and found that the frequency shifts in the H - O - H bending mode and the differences in the O - H stretching vibration modes can be correlated with the orientations of the water molecules along the natrolite channel. Assuming that the members of a solid solution series behave as an ideal mixture, we will be able to use spectroscopy to probe compositions. Deviation from ideal behavior might indicate the occurrence of phase separation on various length scales. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graphene nanodots-encaged porous gold electrode fabricated via ion beam sputtering deposition for electrochemical analysis of heavy metal ions

All rights reserved. A graphene nanodots-encaged porous gold electrode via ion beam sputtering deposition (IBSD) for electrochemical sensing is presented. The electrodes were fabricated using Au target, and a composite target of Al and graphene, which were simultaneously sputtered onto glass substrates by Ar ion beam, followed with hydrochloric acid corrosion. The as-prepared graphene nanodots-encaged porous gold electrodes were then used for the analysis of heavy metal ions, e.g. Cu2+ and Pb2+ by Osteryoung square wave voltammetry (OSWV). These porous electrodes exhibited enhanced detection range for the heavy metal ions due to the entrapped graphene nanodots in 3-D porous structure. In addition, it was also found that when the thickness of porous electrode reached 40 nm the detection sensitivity came into saturation. The linear detection range is 0.009-4 μM for Cu2+ and 0.006-2.5 μM for Pb2+. Good reusability and repeatability were also observed. The formation mechanism and 3-D structure of the porous electrode were also investigated using scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray photoelectron spectra (XPS). This graphene entrapped 3-D porous structure may envision promising applications in sensing devices.

Heavy metal contamination in vegetables grown in Rawalpindi, Pakistan

Summary: Copper (Cu), cadmium (Cd), chromium (Cr) nickel (Ni), lead (Pb), Iron (Fe), Manganese (Mn) and zinc (Zn) contents of various vegetables (bitter melon, tomato, eggplant, lettuce, cucumber and bell pepper) produced in Rawalpindi, Pakistan was determined using Atomic absorption spectrophotometer (AAS). These plants are the basis of human nutrition in the study area. All vegetables grown at sewage water by farmers showed the highest contamination of heavy metals, followed by local market, Progressive farmers and hydroponic plant. The concentration ranges in mg/kg were (1.45 -2.55) for Cd, (3.10 to 4.92) Cr, (12.15- 20.50) Cu, (25.00-51.00) for Fe, (7.80 to 15.60) for Mn, (10.16 to 15.42) for Ni, (2.12 to 5.41) Pb and (16.58 to 24.08) for zinc. The contamination was above the Maximum Residue Limits (MRLs), set out by WHO. Irregular trends in concentration were also observed in vegetables obtained from local market, progressive farmers and hydroponic plant.

Using inorganic polymer to reduce leach rates of metals from brown coal fly ash

The burning of brown coal for electricity generation produces thousands of tonnes of fly ash each year. Treatment of the fly ash can reduce leach rates of metals and allow it to be disposed in less prescribed landfill. A geopolymer matrix was investigated as a potential stabilisation method for fly ash obtained from electrostatic precipitators and ash disposal ponds. The ratio of fly ash and geopolymer was varied to determine the effects of different compositions on leaching rates. The major element leachate concentrations obtained from pond ash were lower than that of precipitator fly ash. Conversely, precipitator ash-geopolymers were better for trace heavy metal stabilisation. Effective reduction of elemental concentrations in the leachate has been achieved, particularly for calcium, arsenic, selenium, strontium and barium. Scanning electron microscopy revealed the distribution of metals originated from fly ash and from added geopolymer material. It also showed that some elements are leached from ash particles to the geopolymer phase and others remained as undissolved particles. Qualitative analysis showed that fly ash particles interacted with the geopolymers phase through surface reactions.

Internal structure and pigment granules in colored alpaca fibers

Alpaca fibers have some distinct properties such as softness and warmth, which have not been fully understood in combination with the fiber internal structures. In the present investigation, the internal structures of alpaca fibers have been closely examined under the scanning electron microscope (SEM), especially in the longitudinal direction. The results showed that numerous pigment granules reside loosely inside pockets in brown and dark-brown alpaca fibers. These pigment granules were mainly distributed inside the cortical cells, the medullation regions as well as underneath the cuticles. Their size in the brown alpaca fibers was smaller and more uniformly round than in the dark-brown fibers. These granules in colored alpaca fibers loosen the bundle of cortical cells, providing many crannies in the fibers which may contribute to the superior flexibility, warmth and softness of the fibers. Moreover, there are no heavy metal elements found in the granules. The mordant hydrogen peroxide bleaching employed could eliminate the pigment granules and create many nano-volumes for further dyeing of fibers into more attractive colors.

Competitive sorption of intermixed heavy metals in water repellent soil in Southern Australia

In water repellent soil, Cr, Pb and Cu showed higher adsorption intensities than Zn, Cd and Ni did. Soil water repellency is much more widespread than formerly thought. In order to promote fertility and productivity, the irrigation of recycled water onto water repellent soil may be an applied technology to be used in some areas of Southern Australia. Therefore, heavy metals in recycled water potentially enter into the soil. The competitive sorption and retention capacity of heavy metals in soil are important to be determined, especially considering the special geochemical origin of water repellent soil that was caused by waxes on or between the soil particles. Batch equilibrium sorption experiments on Cd, Cr, Cu, Ni, Pb and Zn in their typical proportion in recycled water were conducted in water repellent soil. The sorption intensity, sorption isotherm in the experiments together showed that Cr, Pb and Cu have higher sorption intensity than those of Zn, Ni and Cd in the competitive system. The risk assessment for the application of recycled water onto water repellent soil is definitely necessary, especially for the metal cations with relatively weak sorption.