Sulfur-rich geothermal emissions elevate acid aerosol levels in metropolitan Taipei

Several studies have demonstrated that millions of people globally are potentially exposed to volcanic gases. Hydrogen sulfide is a typical gas in volcanic and geothermal areas. The gas is toxic at high concentrations that predominantly affects the nervous, cardiovascular, and respiratory systems. The WHO air quality guideline for hydrogen sulfide is 150 μg m⁻³ (105 ppb). The northwest part of Taipei is surrounded by sulfur-rich geothermal and hot springs. Active fumaroles and bubbling springs around the geothermal area emit acidic gases. In combination with automobile emissions, the pollution of acid aerosols is characteristic of the metropolis. This study considered sulfur-rich geothermal, suburban and downtown locations of this metropolis to evaluate geothermally emitted acid aerosol and H₂S pollution. Acid aerosols were collected using a honeycomb denuder filter pack sampling system (HDS), and then analyzed by ion chromatography (IC). Results indicated that long-term geothermal emissions, automobile emissions and photochemical reactions have led to significant variations in air pollution among regions of metropolitan Taipei. The highest H₂S concentration was 1705 ppb in the geothermal area with low traffic density and the mean concentration was 404.06 ppb, which was higher than WHO guideline and might cause eye irritation. The SO₂ concentrations were relatively low (mean concentration was 3.9 ppb) in this area. It may partially result from the chemical reduction reaction in the geothermal emission, which converted the SO₂ gas into SO₄²⁻ and H₂S. Consequently, very high sulfate concentrations (mean concentration higher than 25.0 μg m⁻³) were also observed in the area. The geothermal areas also emitted relatively high levels of aerosol acidity, Cl⁻, F⁻, PO₄³⁻, and N-containing aerosols. As a result, concentrations of HNO₃, NO₂⁻, PO₄³⁻, and SO₄²⁻ in metropolitan Taipei are significantly higher than those in other urban areas considered in other studies. These results provide evidence that geothermal emissions represent a significant source of acid aerosols in metropolitan Taipei. Therefore, in this metropolitan area, the combined health effects of air pollutants from automobiles and geothermal emissions should be particular concern.     

Comparative irritant potency of inhaled sulfate aerosols—Effects on bronchial mucociliary clearance

The effect of 1-hr oral inhalation exposures to submicrometer aerosols of ammonium bisulfate (NH₄HSO₄), ammonium sulfate (NH₄)₂SO₄), and sodium sulfate (Na₂SO₄) upon mucociliary clearance from the bronchial tree of rabbits was examined. Exposures to NH₄HSO₄ at concentrations of ～600–1700 μg/m³ produced a significant depression of clearance rate only at the highest exposure level. No significant effects were observed with the other sulfates at levels up to ～2000 μg/m³. When results were compared to those from another study in this laboratory using sulfuric acid (H₂SO₄) aerosol, the ranking of irritant potency was H₂SO₄ > NH₄HSO₄ > (NH₄)₂SO₄, Na₂SO₄. Alteration in bronchial mucociliary clearance due to sulfate aerosols appears to be related to the deposition of [H⁺] on the mucus lining of conducting airways.     

Toxicity of heavy metals and salts to eurasian watermilfoil (Myriophyllum spicatum L.)

The toxicity of various heavy metals and salts to Eurasian watermilfoil (Myriophyllum spicatum L.) was determined under controlled growth conditions. Toxicants were added to water or to soil in systems with and without woods earth in the substrate.Fifty precent inhibition of root weight occurred with concentrations of 0.25 ppm Cu⁺², 1.9 ppm Cr₂O₇ ^–2, 3.4 ppm Hg⁺², 2.9 ppm AsO₂ ^–1, 7.4 ppm Cd⁺², 2.5 ppm Al⁺³, 9.9 ppm Cr⁺³, 41.2 ppm Ba⁺², 21.6 ppm Zn⁺², 13.3 ppm NH₄ ⁺¹, 22.4 ppm CN^–1, 143 ppm B₄O₇ ^–2, 363 ppm Pb⁺², 10,228 ppm Na₂SO₄, and 8,183 ppm NaCl. Soil increased toxicity of Cr⁺² and Ba⁺² but decreased toxicity of Cr₂O₇ ^–2, Cu⁺², Cd⁺², Al⁺³, and Hg⁺². In distilled water, CaCl₂ increased toxicity of Cr⁺³ but not Cr₂O₇ ^–2.For most toxicants there was a consistent relationship between inhibition of length and inhibition of weight and between inhibition of roots and inhibition of shoots. However, Cr₂O₇ ^–2 disproportionately decreased dry weight, and Hg⁺² and Na₂SO₄ disproportionately decreased stem length growth. With Cd⁺² and Cu⁺² stem length was greater relative to other measures of growth. Toxicity of Na₂SO₄ and NaCl was the same when concentrations were calculated as osmotic pressure but not when calculated as Na atoms or as total molecules/L.     

Changes in metal speciation and pH in olive processing waste and sulphur-treated contaminated soil

Degradation of organic matter from olive mill waste and changes in the heavy metal fractionation of a metal-contaminated calcareous soil were studied in a laboratory experiment, in which the olive mill waste was mixed with the soil and then incubated under aerobic conditions. The soil was calcareous (15% CaCO₃) with high Zn and Pb concentrations (2058 and 2947 mg kg⁻¹, respectively). The organic amendment was applied at a rate equivalent to 20 g kg⁻¹ soil, and unamended soil was run as a control. To discern if changes in metal solubility were due to the acidic character of the waste, elemental sulphur was applied to soil as a non-organic acidifying material. The S⁰ rates used were 3.14, 4.71 and 6.28 g kg⁻¹. The mineralisation of total organic-C (TOC) from the waste reached 14.8% of the original TOC concentration after 56 days of incubation. The CO₂–C produced from S⁰-treated soils showed the carbonate destruction by the H₂SO₄ formed through S⁰ oxidation. The organic waste increased EDTA-extractable Zn and Pb concentrations and CaCl₂-extractable Mn levels in soil after two days of incubation. The changes in metal availability with time indicated that the oxidation of phenols from the waste reduced Mn (IV) oxides, releasing Zn and Pb associated with this mineral phase. Organic waste addition did not decrease soil pH; the acidifying effect of S⁰ did not change metal fractionation in the soil.     

Simultaneous determination of Fe and Ni in guarana (Paullinia cupana Kunth) by HR-CS GF AAS: Comparison of direct solid analysis and wet acid digestion procedures

Direct solid sampling method was compared with the conventional wet acid digestion method to simultaneously assay iron and nickel in guarana by high-resolution continuum source graphite furnace atomic absorption spectrometry. Measurements were done with the secondary lines of Fe and Ni. Four digestion procedures using mixtures of HNO₃ and H₂O₂ (procedure A), HNO₃ and HCl (procedure B), HNO₃, HCl and H₂O₂ (procedure C) and HNO₃, H₂SO₄ and H₂O₂ (procedure D) were evaluated. All tested procedures provided quantitative recoveries for Ni, whereas a good recovery for Fe was obtained only with procedure D. Procedure D was chosen for the digestion of all guarana samples. The limit of detection for the direct solid sampling method was 1.004 μg g⁻¹ for Fe and 0.022 μg g⁻¹ for Ni, and the precision ranged from 3.5–20.0% and 2.8–8.0% for Fe and Ni, respectively. Method accuracy was evaluated by statistical comparison between analyte concentrations, obtained by measurements in the solid samples by the proposed method and after the digestion of the samples by procedure D. The validation of the analytical results obtained for the solid and the digested sample was performed by Energy Dispersive X-Ray Fluorescence.     

Characteristics and Sources of Water-Soluble Ionic Species Associated with PM10 Particles in the Ambient Air of Central India

PM₁₀ aerosol samples were collected in Durg City, India from July 2009 to June 2010 using an Andersen aerosol sampler and analyzed for eight water-soluble ionic species, namely, Na⁺, NH₄ ⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻, NO₃ ⁻ and SO₄ ²⁻ by ion chromatography. The annual average concentration of PM₁₀ (253.5 ± 99.4 μg/m³) was four times higher than the Indian National Ambient Air Quality Standard of 60 μg/m³ prescribed by the Central Pollution Control Board, India. The three most abundant ions were SO₄ ²⁻, NO₃ ⁻, and NH₄ ⁺, with average concentrations of 8.88 ± 4.81, 5.63 ± 2.22, and 5.18 ± 1.76 μg/m³, respectively, and in turn accounting for 27.1 %, 16.5 %, and 15.5 % of the total water-soluble ions analyzed. Seasonal variation was similar for all secondary ions i.e., SO₄ ²⁻, NO₃ ⁻, and NH₄ ⁺, with high concentrations during winter and low concentrations during monsoon. Varimax Rotated Component Matrix principal component analysis identified secondary aerosols, crustal resuspension, and coal and biomass burning as common sources of PM₁₀ in Durg City, India.     

Wet and Dry Deposition Fluxes of Inorganic Chemical Species at a Rural Site in Northern Jordan

Wet and dry deposition samples were collected in a rural region in northern Jordan during the period of December 1998 to April 2000. Concentrations of 20 chemical species (Na, K, Ca, H⁺, Mg, NH₄⁺, Cl⁻, NO₃⁻, SO₄²⁻,Pb, Cd, Zn, Cu, Al, Fe, Mn, Mo, Ni, Sb, and V) were determined in collected samples. Most of the Al, Fe, Mn, Mo, Sb, and V were not soluble, whereas major ions (Na, K, Ca, H⁺, Mg, NH₄⁺, Cl⁻, NO₃⁻, and SO₄²⁻) and some trace elements (Cd, Cu, and Zn) were wet deposited mostly in the soluble form. Concentration of the soil-related elements and/or highly soluble species were washed out at the early stages of a precipitation event, and their concentrations were mostly controlled by dilution, whereas concentrations of anthropogenic species were controlled by other factors. Annual fluxes of the soil-related elements and ions were significantly higher than the primarily anthropogenic elements. This was attributed to the arid nature of the region and to the frequent input of the Saharan dust pulses.     

Heavy Metals (Cr, Zn, Ni, V, Pb, Cd) in Lingonberries (Vaccinium vitis-idaea L.) and Assessment of Human Exposure in Two Industrial Areas in the Kemi-Tornio Region, Northern Finland

The concentration of Cr, Zn, Ni, V, Pb, and Cd were measured in lingonberries (Vaccinium vitis-idaea L.) sampled at 23 sampling sites around a ferrochrome and stainless steel works and opencast chromium mine in the Kemi-Tornio region, Northern Finland. Two different microwave-assisted digestion procedures were used for sample digestion, i.e., a mixture of HNO₃ + H₂O₂ and a mixture of HNO₃ + H₂O₂ + HCl + HF + H₃BO₃. According to the results, the digestion procedure with the mixture of HNO₃ + H₂O₂ underestimated especially the Cr concentrations in plant material. The maximum concentrations of Cr (1.3 mg kg^–1, wet weight), Ni (358 g kg^–1; ww), V (36 g kg^–1; ww), and Cd (2.4 g kg^–1; ww) in the immediate vicinity of the point sources were 33, 6, 4, and 8 times higher than the background levels, respectively. The dietary intakes of Cd and Pb were assessed and compared to the health criteria recommendations set by the joint Food and Agriculture Organization and World Health Organization Expert Committee on Food Additives (JECFA). The results showed that, depending on the consumption of lingonberries, human exposure based on the mean concentrations for Pb and Cd varied between 0.04% and 0.07% for Pb and between 0.04% and 0.09% for Cd compared to the tolerable total quantities of 25 g kg^–1 for Pb and 7 g kg^–1 for Cd per body weight per week set by JECFA.     

Differential sensitivity of Dugesia dorotocephala and Cheumatopsyche pettiti to water acidification: Ecological implication for predator-prey interactions

The initial hypothesis that predation pressure should decrease with decreasing pH in aquatic macrobenthic communities if predatory invertebrates are more sensitive to water acidification than prey invertebrates is tested. Short-term toxicity bioassays were conducted in soft water (average value of total hardness 38.0 mg CaCO₃/L) to determine the differential sensitivity of the predator, Dugesia dorotocephala (Turbellaria, Tricladida), and the prey, larvae of Cheumatopsyche pettiti (Insecta, Trichoptera), to low pH. Test pH solutions were prepared with sulfuric acid (H₂SO₄). Test species were also exposed to high concentrations of sulfate ion (95 mg SO₄=/L for D. dorotocephala and 340 mg SO₄=/L for C. pettiti) as sulfate toxicity controls, using potassium sulfate (K₂SO₄). No mortality was observed during these toxicity controls, indicating that toxic effects generated by low pH were fundamentally due to H⁺ ions. The 72 and 96-h LC50s (as pH values) and their 95% confidence limits were 4.88 (4.72–5.05) and 5.04 (4.89–5.21) for D. dorotocephala, and 3.25 (3.00–3.51) and 3.48 (3.24–3.73) for C. pettiti. Net-spinning caddisfly larvae migrated from their retreat nets and protruded their anal papillae before dying. After short-term bioassays, predation-pressure laboratory experiments were performed for 6 days. The cumulative mortality of C. pettiti by predation of D. dorotocephala decreased with decreasing sublethal pH values. The average predation rates at mean pH values of 7.7, 7.7, 6.6, 6.5, 6.2 and 6.0 were 2.5, 2.0, 1.33, 1.17, 0.67 and 0.33 larvae/day, respectively. The major biotic factor affecting predation pressure appears to be the reduction in the physiological activity of triclads at low pH. It is concluded that predation pressure can decrease in aquatic macrobenthic communities if prey are more tolerant to water acidification than predators.     

Air Quality Status During Diwali Festival of India: A Case Study

The PM_2.5 and PM₁₀ samples were collected during Diwali celebration from study area and characterized for ionic concentration of four anions (NO₃ ⁻, NO₂ ⁻, Cl⁻, SO₄ ²⁻) and five cations (K⁺, Mg²⁺, NH₄ ⁺, Ca²⁺, Na⁺). The results showed that the ionic concentrations were three times compared to those on pre and post Diwali days. Predominant ions for PM_2.5 were K⁺ 33.7 μg/m³, Mg⁺ 31.6 μg/m³, SO₄ ²⁻ 22.1 μg/m³, NH₄ ⁺ 17.5 μg/m³ and NO₃ ⁻ 18 μg/m³ and for PM₁₀ the ionic concentrations were Mg⁺ 29.6 μg/m³, K⁺ 26 μg/m³, SO₄ ²⁻ 19.9 μg/m³, NH₄ ⁺ 16.8 μg/m³ and NO₃ ⁻ 16 μg/m³. While concentration of SO₂ and NO₂ were 17.23, 70.33 μg/m³ respectively.     

Health Hazards from Volcanic Gases: A Systematic Literature Review

Millions of people are potentially exposed to volcanic gases worldwide, and exposures may differ from those in anthropogenic air pollution. A systematic literature review found few primary studies relating to health hazards of volcanic gases. SO₂ and acid aerosols from eruptions and degassing events were associated with respiratory morbidity and mortality but not childhood asthma prevalence or lung function decrements. Accumulations of H₂S and CO₂ from volcanic and geothermal sources have caused fatalities from asphyxiation. Chronic exposure to H₂S in geothermal areas was associated with increases in nervous system and respiratory diseases. Some impacts were on a large scale, affecting several countries (e.g., Laki fissure eruption in Iceland in 1783–4). No studies on health effects of volcanic releases of halogen gases or metal vapors were located. More high quality collaborative studies involving volcanologists and epidemiologists are recommended.     

Chemical extractions of heavy metals in sediments as related to metal uptake by grass shrimp (Palaemonetes pugio) and clam (Mercenaria mercenaria)

Sediments from four sites in the Hampton Roads Harbor and Elizabeth River system were subjected to solid phase bioassays usingPalaemonetes pugio andMercenaria mercenaria. Metal levels in both organisms after exposure to the sediments varied little between sites; there was no difference in metal uptake between organisms exposed to the test sediments and to the reference sediment. All of the test sites would be acceptable for ocean disposal with respect to the tested metals. Metals concentrations inPalaemonetes were generally greater thanMercenaria. The amounts of metals extracted from the sediments were in the order of Conc HNO₃+H₂O₂>1N HNO₃>DTPA. Differences in metal levels in the Conc HNO₃+H₂O₂ and DTPA extracts from different sediments were generally significant and related to sediment type and sampling location. Since there was no significant difference in the concentrations in tissue for either organism, there was no correlation of metal uptake with the sediment extraction method. Out of four sites and metals studied with two test organisms, there were only four instances of bioaccumulation. Data from sediment extractable metals and metal/Fe ratios indicatedPalaemonetes were enriched with respect to the sediment in Cr, Cu, Ni, Pb, and Zn;Mercenaria were enriched with Pb and Zn.     

Dew water chemical composition and source characterization in the IGP outflow location (coastal Bhola,Bangladesh)

Dew water samples were collected during the winter season (December, 2014 to January, 2015) at an outflow location from the Indo-Gangetic Plain (IGP) to the Bay of Bengal (Coastal Bhola, Bangladesh). Physical properties of the dew water, including pH and electrical conductivity (EC), were measured. The concentrations of water soluble ions (Cl^?, SO₄ ^2?, NO₃ ^?, HCO₃ ^?, Na⁺, K⁺, Ca²⁺, and Mg²⁺) and trace metals (Zn, Fe, Mn, Cu, Cr, Pd, and Ni) were also measured. Source characterization of the chemical species was done by correlation analysis, enrichment factor analysis, percent source contribution calculation, and air mass trajectory analysis. The average pH and EC of the collected dew water were 6.81 and 154.80 μS cm^?1, respectively. The average concentration of SO₄ ^2? and NO₃ ^? was 264.10 and 222.20 μeq L^?1, respectively. The concentrations of water soluble ions followed the sequence: Ca²⁺ > Cl^?> SO₄ ² > Na⁺ > NO₃ ^?> Mg²⁺ > K⁺ > HCO₃ ^?. The concentrations of trace metals ranged in order with Zn > Fe > Mn > Cu, while the concentrations of Cr, Pb, and Ni were below detection limit in dew water. Regression analysis showed significant correlations among sea, soil, and anthropogenic species. High enrichment factors of SO₄ ^2?, NO₃ ^?, Zn, Mn, and Cu indicates anthropogenic sources. Percent source contribution of different species showed significant anthropogenic contribution for Cl^?(1.80%), SO₄ ^2?(83.5%), and NO₃ ^?(99.3%). Air mass trajectory analysis supported that the regional urban pollutions have significant influence on the dew water chemistry at the coastal Bhola, Bangladesh.     

Effects of subchronic nitrite exposure on rainbow trout (Oncorhynchus mykiss)

Subchronic toxicity of nitrite in rainbow trout (Oncorhynchus mykiss; mean mass±S.D., 18.9±1.3 g) was assessed in a 28-day trial. The influence of nitrite on fish mortality, growth rate, haematology, blood biochemistry, and gill histology was observed. Survival was not affected by exposures up to 1 mg l⁻¹ NO₂⁻ (at 10 mg l⁻¹ Cl⁻). On the basis of growth rate inhibition data, the values of NOEC (28 d LC₀) and LOEC (28 d LC₁₀) were estimated at 0.01 and 0.2 mg l⁻¹ NO₂⁻, respectively. At 0.01 mg l⁻¹ NO₂⁻ (the lowest concentration tested), there was segmental hyperplasia of the respiratory epithelium of secondary lamellae and elevated glucose and decreased potassium. Elevated nitrite concentrations were found in blood plasma of fish exposed to concentrations of 1.0 mg l⁻¹ NO₂⁻ and higher, and in muscle tissue at the highest concentration 3.0 mg l⁻¹ NO₂⁻. Plasma and muscle nitrite levels were lower than those in the ambient water in all experimental groups.     

Water-soluble ionic composition of PM2.5–10 and PM2.5 aerosols in the lower troposphere of an industrial city Raipur, the eastern central India

Size-segregated aerosol samples were collected at Raipur, India, during the period of October 2008 to September 2009, using eight-stage cascade impactor-type aerosol sampler at a flow rate of 28.3 l/min. The results give information about the mass concentrations, seasonal variations, and sources of water-soluble inorganic species viz. Na⁺, NH ₄ ⁺ , K⁺, Mg²⁺, Ca²⁺, Cl^-, NO ₃ ^- , and SO ₄ ^2- in both PM_2.5–10 (coarse) and PM_2.5 (fine) fractions. Annual mean of mass concentrations of PM_2.5–10 and PM_2.5 aerosols were monitored to be 200.7?±?55.1 and 185.9?±?66.9 μg/m³, respectively. The annual mean concentrations of the inorganic components were monitored to be 5.4?±?2.4, 6.2?±?4.7, 5.3?±?1.8, 3.2?±?0.46, 40.8?±?7.9, 9.2?±?3.8, 21.6?±?5.5, and 17.9?±?4.0 μg/m³ in PM_2.5–10 aerosols and 4.1?±?2.1, 13.4?±?4.2, 7.7?±?2.0, 1.7?±?0.4, 18.7?±?5.4, 9.7?±?3.1, 13.4?±?5.7, and 36.8?±?10.0 μg/m³, respectively, in PM_2.5 aerosols, for the above ions. The concentration of Na⁺, Mg²⁺, and Ca²⁺ were higher in spring and summer. The seasonal variation of secondary components NH ₄ ⁺ , NO ₃ ^- , and SO ₄ ^2- were similar; that means high concentration in winter and low concentration in fall. The results obtained from factor analysis suggested the presence of three main components/sources in the coarse and fine modes namely regional pollution, airborne road dust, and traffic emissions, which contributed 94.0% and 83.2% of the total variance of the system respectively for the PM_2.5–10 and PM_2.5 aerosols data set.     

Response of ciliated epithelium to ozone and sulfuric acid

The effects of ozone (O₃), sulfuric acid (H₂SO₄), and their interaction on ciliary activity were investigated. Following in vivo exposure to various concentrations of O₃ and H₂SO₄, ciliary activity of isolated tracheal ring cultures was microscopically determined under stroboscopic illumination. Assay of tracheal rings immediately after a 2-hr exposure to 880 μg H₂SO₄/m³ showed a significant decrease (P < 0.0001) in ciliary beating frequency from controls. Following 72 hr in vitro maintenance, there was still a significant depression (P < 0.01) in ciliary activity of treatment cultures. In vivo recovery studies indicated that ciliary activity had returned to the normal range 72 hr after exposure. Exposure to 196 μg O₃/m³ for 3 hr resulted in no significant difference from controls in ciliary activity. Experiments designed to investigate the effects of a sequential exposure to O₃ followed by H₂SO₄ indicated a significant decrease (P < 0.05) in the ciliary beating frequency of exposed animals which was less than that observed with H₂SO₄ alone. As indicated by the results of these studies, combined action experiments are extremely relevant in assessing the toxicity of environmental pollutants.     

Acid precipitation effect on anion transport of the Atkins Reservoir,Massachusetts

The anion concentration of the water in the precipitation reservoir and its watershed of Atkins Reservoir, Massachusetts was studied. In the precipitation study, the NO₃ ^– and SO₄ ^2– levels increased with a pH drop andvice versa, but the Cl^– was interfered with by regional marine air masses. The average pH of precipitation and the reservoir were 3.85 (SD=±0.89) and 6.08 (SD= ±0.18), respectively. The average alkalinity of the reservoir was very low; 0.88 mg/L CaCO₃ (SD= ±0.68). The precipitation and reservoir concentrations of anions were: F^– (0.5 and 0.2 ppm), Cl^– (2 and 4 ppm), and SO₄ ^2– (7 and 7.8 ppm), respectively. The NO₃ ^– level in the precipitation (4 to 6 ppm) was at least an order higher than the reservoir (0.2 to 0.4 ppm) and this was due to selective NO₃ ^– uptake by terrestrial plants. About 50% of the samples collected at the bottom of the reservoir were high in NO₃ ^– where organic decomposition would be expected. The response of the SO₄ ^2– and and Cl^– levels to pH drop in the reservoir inlet study followed a SO₄ ^2– retention-Cl^– release mechanism. The F^– concentration in the precipitation and reservoir was not dependent on pH changes. The lack of F^– in soil samples adjacent to the reservoir indicated that the F^– in the reservoir came primarily from precipitation.     

HPLC Determination of Plasma Thiocyanate Concentrations in Fish Blood: Application to Laboratory Pharmacokinetic and Field-Monitoring Studies

The pharmacokinetics of thiocyanate (SCN⁻) in the blood plasma of 35-g rainbow trout (Oncorhynchus mykiss) were followed during a 20-day exposure to 39.8 mg SCN⁻ liter⁻¹ and the subsequent 16-day depuration period. SCN⁻ concentrations were determined by reverse-phase HPLC. Kinetic constants were estimated using a one-compartment first-order kinetic model fitted to the data by the computer programs BIOFAC and SYSTAT. The respective BIOFAC and SYSTAT estimates for the uptake rate constant (k₁, 0.55 and 0.49 day⁻¹), the depuration rate constant (k₂, 0.34 and 0.29 day⁻¹), and the bioconcentration factor (BCF, 1.61 and 1.66) were similar for both methods of calculation. Field studies were conducted to determine the impact of SCN⁻ on white sucker (Catostomus commersoni) populations in waters receiving SCN⁻ bearing effluents. The assessment was based on SCN⁻ concentrations in water and fish plasma, and the thyroid histology of the fish. Although SCN⁻ was detected in the water at one site, no SCN⁻ was detected in fish plasma and none of the thyroid pathology characteristic of chronic SCN⁻ exposure was present. The results suggest that SCN⁻ was not a hazard to the white sucker populations studied.     

Chemical characteristics and possible causes of acid rain at a regional atmospheric background site in eastern China

A total of 43 rainwater samples were collected from March 2014 to February 2015 at a regional atmospheric background station, in Lin’an, Zhejiang province, eastern China. We analyzed all rainwater samples for pH, electrical conductivity, and concentration of SO₄ ^2?, NO₃ ^?, Cl^?, F, NH₄ ⁺, Ca²⁺, Na⁺, Mg²⁺, and K⁺. The pH of the 43 analyzed rainfall events ranged from 3.39–6.37, with a volume-weighted mean (VWM) of 4.74; 72% of the precipitation events qualified as acid rainfall (those where the rain pH was <5.6), indicating that acid rain pollution was severe in Lin’an area. Although the ionic concentrations in the Lin’an rainwater were lower than those found in most urban areas in China and in rural areas in India, they were still higher than those in Waliguan (a global atmospheric background station in northwestern China) and in Newark, NJ, USA. We found that SO₄ ^2? and NO₃ ^? were the major anions in the precipitation, accounting for an average of 88% of the total inorganic anions. The SO₄ ^2? concentration was between 3.8–303.9 μeq L^?1 with a VWM value of 49.8 μeq L^?1, while the NO₃ ^? concentration was between 3.0–206.5 μeq L^?1 with a VWM value of 32.6 μeq L^?1. The ratios of SO₄ ^2? to NO₃ ^? ranged from 0.71 to 2.56 with an average of 1.53, indicating that SO₄ ^2? was the most significant anion causing rainfall acidification in Lin’an area. This is similar to observations made in 2008. Compared to observations in Lin’an area in 2008, the contribution of SO₄ ^2? to rainwater acidity had decreased due to sharp reduction in SO₂ emissions, while the contribution of NO₃ ^? had increased due to a rapid growth in the use of motor vehicles in eastern China. We observed that the alkaline component NH₄ ⁺ made the largest contribution toward neutralizing rainwater acidity. The neutralization factor (NF) for NH₄ ⁺ was between 0.26 and 1.03 with an average of 0.63, and the NF for Ca²⁺ was between 0.09 and 1.21 with an average of 0.30. The ratio of Ca²⁺ to NH₄ ⁺ was between 0.15 and 4.70 with an average of 0.48, lower than that observed in Chinese urban areas and close to that observed in non-urban Chinese sites. These results indicated that Ca²⁺ was still a major factor in buffering rainwater acidity in most urban areas in China, while NH₄ ⁺ seemed to be the most important basic ion for neutralizing rainwater acidity in non-urban areas. In the Lin’an area, the Cl^? and K⁺ in rainwater were mostly of marine origin; however, SO₄ ^2?, Ca²⁺ and Mg²⁺ were generated mainly from the earth’s crust and anthropogenic emissions.     

Potential of vetiver (Vetiveria zizanoides L. Nash) for phytoremediation of phenol

Aseptically grown Vetiveria zizanoides were evaluated for their potential for phytoremediation of phenol from Murashige and Skoog's liquid medium. Phenol was found to be completely removed from incubation medium at the end of 4 days by V. zizanoides plantlets, when medium was supplemented with 50 and 100 mg L⁻¹ phenol, while with 200, 500, and 1000 mg L⁻¹ of phenol, 89%, 76% and 70%, respectively, were removed. Phenol removal was found to be associated with inherent production of peroxidase and hydrogen peroxide. Coupled with H₂O₂ formation, the levels of antioxidant enzymes like superoxide dismutase and peroxidase showed an enhancement when plants were exposed to phenol, whereas catalase levels initially showed a decline due to the utilization of H₂O₂ by peroxidase for phenol oxidation. However, when peroxidase levels declined, there was an enhancement in catalase levels to minimize the presence of H₂O₂ in the medium. Having confirmed that the removal of phenol was by V. zizanoides plantlets, in the next phase, micropropagated plantlets and well-developed plants grown in hydroponics were used under in vivo conditions to study the effect of phenol (200 mg L⁻¹) on plant growth and reuse. Although plant growth was reduced in presence of phenol, the results of the reuse study indicated the possibility of plants getting adapted to phenol without any decline in potential for phenol remediation.