Preeda Parkpian

Assessment of heavy metal contamination and its mobilization from municipal solid waste open dumping site

Influence of heavy metals was investigated by conducting various tests on the samples collected from Nonthaburi dumpsite in Thailand. The heavy metal concentration in the solid waste and its mobility potential based on its binding forms was studied. The sequential extraction method was used to determine the binding forms of metals. From the analysis, Zn was found to be highest concentrated heavy metal compared to Mn, Cu, Cr, Cd, Pb, Ni and Hg in the solid waste. From the sequential extraction, Mn, Zn and Cd mostly found in reducible form, showed its susceptibility to be leached easily. Cu and Cr were found predominantly in oxidizable form and stable under anaerobic condition. Pb and Ni were present in residual form, which is inert. The estimated individual contamination factor (C(f)(i)), showed Zn with highest affinity to leach. The concentration level of all the heavy metals in the leachate except for Cr was noticed to be below the National effluent standards. Though, indicated to be safe for disposal, its effect in any concentration proved toxic to the plant life from the seed germination toxicity test using synthetic chelate ethylene diamine tetraacetic acid (EDTA).

Paraquat Adsorption, Degradation, and Remobilization in Tropical Soils of Thailand

Paraquat adsorption, degradation, and remobilization were investigated in representative tropical soils of Yom River Basin, Thailand. Adsorption of paraquat in eight soil samples using batch equilibration techniques indicated that adsorption depended on soil characteristics, including exchangeable basic cations and iron content. Multiple regression analysis indicated significant contribution of exchangeable calcium percentage (ECP), total iron content (TFe) and exchangeable sodium percentage (ESP) to paraquat sorption (Q). ESP and TFe were significant at all adsorption stages, whereas ESP was significant only at the initial stage of paraquat adsorption. Adsorption studies using two soils representing clay and sandy loam textures showed that paraquat adsorption followed the Freundlich model, exhibiting a nonlinear sorption curve. Paraquat adsorption was higher in the clay soil compared to the sandy loam soil with K f values of 787 and 18, respectively. Desorption was low with 0.04 to 0.17% and 0.80 to 5.83% desorbed in clay and sandy loam soil, respectively, indicating some hysteresis effect. Time-dependent paraquat adsorption fitted to the Elovich kinetic model indicated that diffusion was a rate-limiting process. Paraquat mobility and degradation studies conducted using both field and laboratory soil column experiments with clay soil showed low mobility of paraquat with accumulation only in the surface 0–5 cm layer under field conditions and in the 0–1 cm layer in a laboratory soil column experiment. Degradation of paraquat in soil was faster under field conditions than at ambient laboratory conditions. The degradation rate followed a first-order kinetic model with the DT50 at 36–46 days and DT90 around 119–152 days.

Regional monitoring of lead and cadmium contamination in a tropical grazing land site, Thailand

An investigation was carried out to monitor Pb and Cd contamination in grazing land located near a highway. Environmental media at different distances fromhighway (soil, grass, water, cows forage, fertilizer,manure and milk samples) were collected from three samplinglocations. Soil and grass were characterized by high metalmobility (soil with Pb: 5.25±0.71–14.59±1.17 mgkg-1, dry mass and Cd: 0.038–0.33±0.04 mg kg-1, dry mass and grass with Pb: 0.76±0.05–6.62±0.18 mg kg-1, dry mass and Cd: 0.17±0.01–0.73±0.09 mg kg-1, dry mass). One-way analysis of variane (ANOVA) was applied to find out the correlation between metal (total and bioavailable) concentrationsin the soil and the distance from roadside. In most cases, the finding showed that plants growing nearer to the highway are usually exposed to more heavy metal accumulations than those awayfrom the highway. In addition, a correlation was established between plant available metal concentrations and plant metaluptake concentrations.Analysis of fertilizer and manure showed considerable amountof metals (fertilizer with Pb: 1.53±0.06 mg kg-1 andCd: 0.038 mg kg-1 and manure with Pb: 2.55–3.34 mgkg-1 and Cd: 0.14–0.31 mg kg-1). Long termsimultaneous application of fertilizer and manure on thecommercial farm showed higher metal accumulation in the soiland plants than those of co-operative farm Considerableconcentrations of metals (Pb: 1.60–2.94 mg kg-1 andCd: 0.025–0.19 mg kg-1) were observed in fodder. The finding clearly demonstrated that there are seasonalvariation in total daily metal intake by individual cow (Pb:109.37 mg day-1 (dry), 273.47 mg day-1 (rainy) andCd: 2.02 mg day-1 (dry), 19.62 mg day-1 (rainy)).The provisional tolerable weekly intake of heavy metals incows is 390 μg Pb and 28 μg Cd per kg bodyweight in the rainy season and 156 μg Pb and 2 μgCd per kg body weight in the dry season. The levels of metals (Pb: 0.014 mg L-1 and Cd: not detectable) and bio-transferfactor (10-5–10-4) in raw milk were found to be well below the Codex Alimentarius Commissions Draft (1997). Ouranalysis revealed that improvements on farm management give significant reduction in elevated levels of Pb and Cdin soil and plants, and however leads to minimize the amountof Pb and Cd in consumed milk.

Assessment of Hg contamination and exposure to miners and schoolchildren at a small-scale gold mining and recovery operation in Thailand

Gold extracted by Hg-amalgamation process, which can cause both health and environmental problems, is widespread in South East Asia including Myanmar, Laos, Cambodia, and Thailand. Small-scale gold mining operations have been carried out since the year 2000 in Phanom Pha District, Phichit Province, Thailand. Since no data is available for evaluating Hg exposure, an investigation of mercury (Hg) contamination and exposure assessment was carried out at this mine site. Environmental monitoring illustrated the total Hg in water was as high as 4 μg/l while Hg in sediment ranged between 102 to 325 μg/kg dry weight. Both Hg deposition from the air (1.28 μg/100 cm2/day) and concentration in surface soil (20,960 μg/kg dry weight) were elevated in the area of amalgamation. The potential of Hg exposure to miners as well as to schoolchildren was assessed. The concentrations of Hg in urine of 79 miners who were directly (group I) or indirectly (group II) involved in the gold recovery operation were 32.02 and 20.04 μg/g creatinine, respectively, which did not exceed regulatory limits (35 μg/g creatinine). Hair Hg levels in both groups (group I and group II) also were not significantly higher than the non-exposed group. In terms of risk factors, gender and nature of food preparation and consumption were the two significant variables influencing the concentration of Hg in urine of miners (P < 0.05). A hazard quotient (HQ) was estimated based on the inorganic Hg exposure of individual miners. The HQ values of group I were in a range 16 to 218 times higher than the safety level set as 1. By comparison the group II HQ index was very low (0.03–0.39). The miners in group I who worked and ate food from this area experienced potentially high exposure to Hg associated with the mining process. In a second Hg exposure assessment, a group of 59 schoolchildren who attended an elementary school near the gold mine site was evaluated for Hg exposure. A slightly higher Hg urine concentration was detected in group I and group II (involved and not involved in gold recovery) at average levels of 15.82 and 9.95 μg/g creatinine, respectively. The average Hg values for both groups were below the established levels indicating no risk from Hg intake. Average Hg hair level in all schoolchildren (0.93 μg/g) was not significantly higher than reference group. There were two variables (gender and personal hygiene) which affected the concentration of Hg in urine of schoolchildren (P < 0.05). The result (HQ) also suggested that schoolchildren were not at risk (< 1). Schoolchildren involved in gold mining activities showed some indirect exposure to Hg from the adults working in mining area.

Adsorption, desorption and degradation of α‐endosulfan in tropical soils of Thailand

Abstract The adsorption, desorption, and degradation of endosulfan (1,2,3,4,7,7‐hexachlorobicyclo[2,2,l]‐2‐heptene‐5,6‐bisoxymethylene sulfite) in two major tropical soils from Thailand were studied. Each soil‐type, Rangsit lowland soils (Rangsit series) and Phrabat upland soils (Pakchong series), were sub‐divided into surface or plow layer, 0–20 cm depth, and subsoils, 20–40 cm depth. Adsorption was determined using 24 h batch equilibrium, with five different concentrations of 14C labelled endosulfan ranging from 1.04 to 16.64 ng/mg soils. Adsorption coefficient values (Kads) as by Freundlichs model ranged from 0.02 to 0.20. Higher adsorption coefficients were measured in Rangsit soils as compared to Phrabat soils. Desorption as attributed to hysteresis was also measured. Desorption coefficient values (Kjes) were higher than adsorption (Kads) in each study. Degradation of endosulfan was through microbial process. Little abiotic degradation was measured in sterile soil sample. Measured degradation rates ...

Assessment of metal speciation evolution in sewage sludge dewatered in vertical flow reed beds using a sequential extraction scheme

Abstract An investigation was carried out into the speciation of metals contained in an industrial sewage sludge dewatered in vertical flow reed beds as compared to conventional sand drying beds. The highly contaminated sludge was loaded for two consecutive months and the dewatered sludge layers were monitored periodically during an ageing period of 15 months. Metal speciation was assessed by means of sequential extraction. The raw sludge was characterised by high metal mobility. 445 mg kg−1 dry matter (DM) Mn (70% of total Mn), 632 mg kg−1 DM Ni (42% of total Ni), 11,246 mg kg−1 DM Fe (32% of total Fe), 2,315 mg kg−1 DM Zn (19% of total Zn) and 258 mg kg-1 DM Pb (14% of total Pb) were retrieved in the exchangeable and acid extractable fractions. Cu and Cr were less mobile, with 24 mg kg−1 DM Cu (1.2% of total Cu) and 7 mg kg−1 DM Cr (0.8% of total Cr) occuring in these fractions. Upon sludge ageing, all metals except copper, were greatly immobilised in the oxidisable, reducible and residual fractions. However, considerable amounts remained mobile, posing environmental threats upon final disposal of the dewatered sludge.

METAL LEACHABILITY FROM SEWAGE SLUDGE-AMENDED THAI SOILS

ABSTRACT Determining mobility and availability of metals in sewage sludge amended soil is an environmental concern. Potential leachability and bioavailability of metals following sludge applied to agricultural soil was evaluated. Geochemical forms of metal occurring in sludge-amended soil were subjected to fractionation for understanding heavy metal transformation and remobilization in sludge-amended soil. Metal leachability was determined using reconstructed soil profiles where dewatered sewage sludge was incorporated into the surface 0–10 cm of soil. Two-sludge application rates; 150 and 300 kgN/ha, equivalent to sludge at 4 and 8 ton/ha, were applied to soil columns representing typical agricultural clay soils of Thailand (Rangsit acid sulfate soil). The soil columns were leached with 32 l equivalent to 600 mm of surface water using different leachants (distilled water pH 6, distilled water adjusted to pH 3 and rainwater pH 5). Among metals measurement, results showed Mn leachability from sludge-amended Rangsit soil were high at both sludge application rates (18–29% of total Mn applied). The leachability of other metals was less than 2.5 and 7.2% following application of 150 and 300 kgN/ha of sludge, respectively. Results from the experiments indicated that the leachant at pH 3 had the most effect on potential leachability of Cu, Zn, Cd, and Ni, except Fe and Mn, at low sludge application rate. Whereas, only the leachability of two metals was influenced by the lowest pH (pH 3) when sludge applied was increased. Besides pH of leachant, it appeared that leachability of elements from the soil column depended on rate of sludge applied, the particular metal, and metal form or fraction. The soil studied had organic matter, CEC, pH, clay content, etc., that resulted in high buffering capacity, which favors metal retention. Less than 0.5 and 1.8% of the added Cu and Zn applied at the 150 and 300 kgN/ha application rates, respectively, were detected in the leachate. Approximately 100% of the added Cu and Zn in the sludge remained in the surface 10 cm at each sludge application rate. Sequential extraction of sludge-amended soil following leaching (at the high sludge application rate) revealed that most of the Cu remained in the surface sludge-amended soil layer (0–2 cm depth) in the form of organic and residual Cu fractions that are not easily mobilized. An exchangeable fraction of Zn increased, approximately representing 60% total Zn applied in sludge–soil layer as compared with its native soil Zn fractions. These results demonstrate that Zn availability in the soil would increase as a result of sludge application. However, the total Zn in the leachate is safe for agricultural use, because it represents an amount of less than 2% of total Zn applied.

Mercury emission and distribution: Potential environmental risks at a small-scale gold mining operation, Phichit Province, Thailand

Mercury (Hg) contamination was assessed in environment near an amalgamation gold recovery operation located at a small scale mining operation (Phanom Pha) in Phichit Province, Thailand. Total mercury (THg) concentrations was determined in water, sediment, bivalves in the aquatic environment and as dry deposition or atmospheric fallout on surface soil and leaves of Neem tree (Azadirachta indica Juss. var. siamensis Valeton) near the mining operation. THg in surface soil, Neem flowers (edible part) and rice grain in surrounding terrestrial habitat and with distance from the mining area were also evaluated for possible contamination. Potential environmental risks were evaluated using the hazard quotient equation. Hg analyses conducted in the aquatic habitat showed that THg in water, sediment and bivalves (Scabies cripata Gould) ranged from 0.4 to 4 μ g L− 1, 96 to 402 μ g kg− 1dry weight (dw) and 15 to 584 μ g kg− 1 wet weight (ww), respectively. High concentrations of THg in water, sediment and bivalves were observed in the receiving stream near the mining operation which was located near the Khao Chet Luk Reservoir. Whereas the THg concentration in water, sediment and bivalves from monitoring stations outside the gold mining operation (upstream and downstream), were considerably lower with the values of 0.4–0.8 μ g L− 1, 96–140 μ g kg− 1 dw and 88–658 μ g kg− 1 dw, respectively. The elevated concentration of Hg found in the sediment near the mining operation was consistent with Hg accumulation measured in bivalves. The elevated Hg levels found in living bivalves collected from highly contaminated sites suggested that the sediment bound Hg was bioavailable. THg in surface soils, brown rice grain (Jasmine rice #105) and Neem flowers of terrestrial habitats were in the range of 16 to 180 μ g kg− 1 dw, 190 to 300 μ g kg− 1 dw, and 622 to 2150 μ g kg− 1 dw, respectively. Elevated concentrations of mercury were found in Neem flowers with the concentration greater than 600 μ g kg− 1 ww, which exceeds the maximum permissible concentration reported for biota tissue (500 μ g kg− 1 ww). An evaluation of air and soil pollution near the mining operations showed high concentrations of THg in dry deposit from atmospheric fallout (139 μ g m− 2 d− 1), and in surface soil (10,564 μ g kg− 1 dw) at station near where open burning of gold ore extracts using the amalgamation process occurred. High or elevated concentration of THg (1172–1301 μ g kg− 1 dw) in leaves of Neem tree was also measured near the mining operations. A survey of Hg in surface soil showed elevated Hg concentrations near the site which corresponded to the elevated THg concentration in dry deposition. These results suggested that atmospheric fallout is a major source of Hg to the area surrounding the mining or gold ore extraction. Results also suggest that Hg emitted into the air (estimated to be 60–150 g d− 1) from the gold mining activities (over the past 10 years) contaminated air, the aquatic environment, surface soil and biota in the area surrounding the gold mining operation.

Potential for land application of contaminated sewage sludge treated with fermented liquid from pineapple wastes

The suitability for land application of anaerobically digested sewage sludge treated with naturally fermented and Aspergillus niger (A. niger) fermented raw liquid from pineapple wastes, in terms of changes in the forms and amount of heavy metals and nutrient and pathogen content, were investigated in this study. Leaching studies for fermented liquid at optimum conditions (pH and contact time with best metal removal efficiencies) were carried out for the removal of Cd, Cr, Cu, Pb, Ni and Zn from sewage sludge, with citric acid as a reference. Using the same sludge before and after leaching, sequential fractionation studies were done to observe the effect of treatment on the forms of metals in sludge and their mobility and bioavailability. Results of laboratory scale studies revealed that leaching with all extractants at selected optimum conditions resulted in a decrease in heavy metals and pathogen content of the treated sludge, presence of sufficient amount of nutrients (nitrogen and phosphorous) and dominance of residual fractions in most metals, with sludge treated with A. niger, having the best quality. The results, therefore, indicate the high potential of the treated sludge for land application, with no harm from heavy metals released and no toxicity to the soil and groundwater.

Environmental conditions associating microcystins production to Microcystis aeruginosa in a reservoir of Thailand.

ABSTRACT Three heptapeptide toxins, microcystin-RR, microcystin-RY and microcystin-LR, which can cause health problems in animals and humans were monitored in Bang Phra Reservoir, Thailand using reversed-phase high performance liquid chromatography. The concentrations of the three toxins in the reservoir varied greatly depending on location and time water samples were collected. Water quality parameters such as light intensity, temperature, pH, dissolved oxygen, suspended solid, chemical oxygen demand, dissolved organic carbon, total nitrogen, total phosphorus, ammonia, nitrate, phosphate, total dissolved nitrogen, total dissolved phosphorus and chlorophyll-a were also measured in parallel with microcystin determinations. Relationships among water quality parameters, toxins and chlorophyll-a were established. Toxin concentration increased in proportion to increases in total phosphorus, fraction of dissolved phosphorus, but was inversely correlated with water pH and total suspended solids. The other measured parameters in the study showed no correlations to toxin level in reservoir water. Significant correlations between chlorophyll-a and suspended solids, phosphate, nitrate and ammonia were observed suggesting that nitrogen and phosphorus are the two major nutrients governing growth of algae in the reservoir. This relationship suggests that algal production as well as toxin concentration are dependant on nutrient levels in the water body, since both measured light intensity and temperature level was favorable for algal growth. A small algal bloom observed in the rainy season of each year (lasting for only a couple of months) paralleled measured increases in toxin concentration, chlorophyll-a, TP and TN in the water column. Toxin level in the water column remain detectable for 3--4 months period following the initiation of algal bloom. Results indicate that major blooms are likely to occur following the raining season which usually occurs near the end of October when runoff would increase nutrient level entering the reservoir. This study also demonstrated that an ongoing field-monitoring program is needed in these lakes and reservoirs for predicting toxic level of microcystin production for use in risk assessment and for alerting the public to potential health hazards. Concentration of toxin in the reservoir can perhaps be controlled by reducing non point source nutrient input within the watershed.