Gian Gupta

Use of fly ash in reducing toxicity of and heavy metals in wastewater effluent

Abstract Fly ash is one of the most abundant waste materials; its major components make it a potential agent for the adsorption of heavy metal contaminants in water and wastewaters. The objective of this study was to measure the changes in toxicity of and heavy metals in a municipal (Salisbury, MD) wastewater treatment plant (SWTP) effluent on treatment with fly ash. The effluent from SWTP after treatment with fly ash for 4 h showed a significant reduction in toxicity, Cu and Pb, and PO43− and NO3− contents. Toxicity of the effluent was measured using the marine luminescent microorganisms—Vibrio fischeri (‘Microtox’ test). Heavy metals (Cu, Pb and Zn) were measured using Atomic Absorption Spectrophotometry. Fly ash removed Cu and Pb from the effluent (through adsorption), and the removal of these toxic heavy metals resulted in the reduction of toxicity.

Biodegradation of atrazine in soil using poultry litter

Microorganisms, including Pseudomonas and Actinomycetes species, are known to degrade atrazine and other pesticides in soil. Poultry litter has a large number of microorganisms along with many nutrients. Atrazine is applied to soil at times soon after using poultry litter as manure. The objective of this research was to study the degradation of atrazine (2 or 3 ppm) in soil using poultry litter. The soil + atrazine mixture was treated with either poultry litter, gamma irradiated poultry litter or water extract of the irradiated litter in order to differentiate between the effects of microorganisms, nutrients and organic matter. Atrazine in the soil was extracted with water and methanol and analyzed by pesticide immunoassay (ELISA) 1, 5, 10, 30 or 60 d after poultry litter treatment. The small loss of atrazine from soil treated with the irradiated litter was almost the same as from the sterile soil with no poultry litter. Atrazine was significantly (86%) degraded in soil with untreated poultry litter within 30 d. Degradation was virtually completed within 60 d. The rate of atrazine biodegradation with poultry litter was almost 2 times faster than without the litter. The toxicity (EC50) of the samples after treatments, to Photobacterium phosphoreum (“Microtox”), was also measured. The toxicity of the soil + atrazine mixture treated with poultry litter (both the untreated and the gamma irradiated) was the same as that of the soil + litter mixture; no significant concentrations of toxic by-products were produced from the biodegradation of atrazine.

Toxicity of and metals in coal combustion ash leachate

Abstract Land disposal of coal combustion ash can have a potential impact on the ecosystem due to the leaching of metals with increasing acidity of precipitation. The objective of this research was to study the effect of pH on the concentration of metals leached from coal combustion ash and to measure the toxicity of the leachates. Bottom coal combustion ash was leached with hydrochloric acid (HCl) or acetic acid (CH3COOH) at pH4, 5, 6 or 7. The toxicity of the aqueous leachates and concentrations of the metals (arsenic, cadmium, chromium, copper, iron, lead, nickel, silver and zinc) therein were measured using Microtox® (Vibrio fischeri—EC50%) and atomic absorption spectrophotometry, respectively. Toxicity and metal concentrations of the leachates were highest when ash was leached with HCl at pH 4. Toxicity and metal concentrations of ash leached with CH3COOH were significantly lower compared with ash leached with HCl. High correlation (r) was observed between the toxicity and the metal concentrations in both the acid leachates.

Effect of methanol on soybean photosynthesis and chlorophyll

Abstract Recently, an increase in the growth and yield of C3 plants in arid environments due to foliar application of methanol has been reported. The mechanism for these changes is not clear as little information is available on the changes in photosynthesis and chlorophyll content of plants caused by methanol application. The objective of this study was to measure the net photosynthesis (PN) and chlorophyll (CHL‐a, b) formation in soybean [Glycine max (L.) Merr] by foliar applications of methanol at the pod‐filling R5) stage. No changes were found in PN or CHL content with 0, 25, or 50% (v/v) methanol during 1, 2 or 3 weekly applications. Seed weight, seed yield, and pod number (per plant) were significantly higher for plants treated with methanol. A single application of methanol (25%) resulted in the highest increase in soybean growth and yield.

Photodegradation of polychlorinated biphenyl congeners using simulated sunlight and diethylamine

Abstract Photodegradation of polychlorinated biphenyls (PCBs) can be an important natural decomposition mechanism. As most PCB congeners do not strongly absorb wavelength above 300 nm, sensitizers are used in the transfer of light energy to the PCB molecule in order to enhance their degradation. The objectives of this study were to determine the rate-order of reaction and the photodegradation rates of PCB congeners by simulated sunlight in the presence of diethylamine. Five PCB congeners (66, 101, 110, 118, and 138) with diethylamine were exposed to simulated sunlight from 0, 1, 2, 4, 8, to 24 hr. These five congeners constitute 45.45 % of all the Aroclor 1254 congeners. Half-lives of these congeners, after exposure to simulated sunlight and diethylamine, ranged from 3.4 to 9.9 hr. The photodegradation rate constant of the PCB congeners varied from 0.07±0.01 to 0.20±0.04 hr−1. The photodegradation rate was proportional to the concentration of the PCB congener suggesting a pseudo first order reaction of PCB photodegradation. The data also indicated that the photodegradation is independent of the concentration of diethylamine. Degradation of congener 101 was 5 times faster with simulated than with natural sunlight. The product quantum yield of PCB congeners ranged from 2.6±0.3 to 7.5±0.2 × 10−4 in the presence of diethylamine.

Heavy metals in sediments of two Chesapeake Bay tributaries — Wicomico and Pocomoke Rivers

Abstract Aquatic sediments can be both sinks and sources of heavy metals. The objective of this study was to measure the concentrations of heavy metals in sediments and sediment-porewaters of two Chesapeake Bay tributaries — Wicomico (WR) and Pocomoke (PR) Rivers so as to better understand the contributions of point (sewage treatment plant — STP) or non-point (agricultural runoff) sources of pollution. Sediment samples from three different depths (3″, 6″ and 9″) at four different sites (one mile before, adjacent to, one and two miles after the STP) on each of the two rivers were collected. This part of WR is residential and receives only STP effluent; whereas this part of PR gets effluents from both the STP and agricultural runoff including runoff from a poultry production farm that generates and stores large amounts of litter. The samples were analyzed for zinc (Zn), lead (Pb), copper (Cu), cadmium (Cd) and arsenic (As) using atomic absorption spectrophotometer (AAS). The concentrations of metals in sediment were normalized against organic carbon content and the correlation coefficient was found to be high in all cases. Concentrations of these metals were significantly higher in the second (near the STP outlet) and third (near the poultry farm) sampling sites in WR and PR, respectively. Metal concentrations decreased significantly (p ≤ 0.05) with depth in both the rivers. High concentrations of ammonia and nitrate in the WR indicate STP as the source of pollution, whereas a large amount of organic matter in PR sediment points toward agricultural runoff (from the poultry farm). As there was no baseline or earlier data on metal concentrations in these rivers the exact anthropogenic metal input could not be estimated.

Sulphur dioxide and carbon dioxide induced changes in soybean physiology

Abstract Soybean ( Glycine max L. Merrill) plants were exposed to sulfur dioxide (SO 2 , 0.1 μl/l) and carbon dioxide (CO 2 , 450 μl/l), singly and in combination, in open-top field chambers at the flowering stage. The exposure for SO 2 and CO 2 was for 4 h and 12 h/day, respectively, for 5 days. Photosynthetic rate (PN), specific root nodule nitrogenase activity (SNA), foliar nitrogen (N) and chlorophyll (Ch-a and Ch-b) were measured after the exposure. The plants exposed to SO 2 showed reduction in PN (by 13%), SNA (by 28%), N (by 23%) without significant change in Ch-a and Ch-b. The plants exposed to CO 2 showed no change in PN, reduction in SNA (by 18%) and N (by 23%) and an increase in both Ch-a and Ch-b. When the plants were exposed to a combination of these two gases PN and SNA were the same as that of the control plants, N decreased slightly (by 6%) but both Ch-a and Ch-b increased significantly. Carbon dioxide was able to compensate the negative impact of SO 2 .

Toxicity of methyl tertiary butyl ether to Daphnia magna and Photobacterium phosphoreum.

Methyl tertiary butyl ether (MTBE) is a liquid organic compound added to gasoline to increase its oxygen content and to reduce the emission of carbon monoxide during combustion in many urban areas. In order to meet the 1990 Clean Air Act amendments, gasoline must contain 2.7% oxygen (by weight) or 15% (by volume) of MTBE in gasoline to meet the regulations for the control of carbon monoxide emissions. Health effects caused by inhalation of MTBE include headaches, dizziness, irritated eyes and nausea; MTBE is one of cancer--causing chemicals. Intracaval injection of MTBE (0.2 mg/kg) caused the highest mortality (100%) in rats. General anesthetic effect induced by MTBE was found at or above 1200 mg/kg body weight; Rosenkranz and Klopman (1991) predicted that MTBE is neither a genotoxicant nor a carcinogen. Nevertheless, the safety of using MTBE in oxygenated fuels is now being questioned from its potential as groundwater pollutant. This study measures the toxicity of MTBE to Daphnia magna and Photobacterium phosphoreum. 13 refs.

Adsorption/desorption of hydrocarbons on clay minerals

Adsorption/desorption of a mixture of 5 hydrocarbons (benzene, toluene, p-xylene, m-xylene, and o-xylene) on montmorillonite, illite and kaolinite was studied using the batch equilibrium method. The adsorption coefficient (K) values ranged from 0.01 to 0.85 and were relatively lower than the reported K values with soils high in organic matter. The adsorption of these hydrocarbons on montmorillonite and illite was higher than on kaolinite. The adsorption reactions were reversible for toluene and illite. A smaller amount of toluene was adsorbed from the hydrocarbons mixture (K = 0.83) compared to the adsorption from a single hydrocarbon solution (K = 2.42). The adsorption coefficients were poorly related to water solubility and octanol-water partition coefficients (Kow) of hydrocarbons.

Chronological changes in toxicity of and heavy metals in sediments of two Chesapeake Bay tributaries

Abstract Sediments are storage compartments for many toxicants and act as indicators of pollution. The objective of this research was to study the chronological changes in the toxicity and heavy metals concentrations in the sediments of Wicomico River (WR) and Pocomoke River (PR)—two Chesapeake Bay tributaries. The sediments were collected from four sites in both the rivers; sediment and porewater were separated and analyzed for toxicity using the marine luminescent bacteria— Vibrio fischeri (Microtox®). The most toxic site from each river was used for studying the chronological changes in toxicity and heavy metals concentrations. A mean sedimentation rate (7.5 cm/yr) was used for calculating the time scale. The sediments were collected at a depth of 23.0 cm and divided into three 10-yr periods. The sediment collected from the depth corresponding to the years 1965–1975 was the least toxic and contained the lowest amount of metals in both the rivers. The toxicity and heavy metal concentrations from this depth were used as the baseline data. Five heavy metals—all EPA priority pollutant—zinc, lead, copper, cadmium and arsenic were identified and measured both in the sediment and porewater. The results show an increase in both the toxicity and input of metals over the next 20 yr compared to the baseline data for both the rivers. The increases in toxicity and heavy metals concentrations appear to be related to increase in industrial and agricultural activity around WR and PR, respectively.