Incidence of metal and antibiotic resistance in Pseudomonas spp. from the river water, agricultural soil irrigated with wastewater and groundwater

A total of 144 isolates of Pseudomonas spp. (48 each from the Yamuna River water, wastewater irrigated soil and groundwater irrigated soil) were tested for their resistance against certain heavy metals and antibiotics. Minimum inhibitory concentrations (MICs) of Hg^2?+?, Cd^2?+?, Cu^2?+?, Zn^2?+?, Ni^2?+?, Pb^2?+?, Cr^3?+? and Cr^6?+? for each isolate were also determined. A maximum MIC of 200 ??g/ml for mercury and 3,200 ??g/ml for other metals were observed. The incidences of metal resistance and MICs of metals for Pseudomonas isolates from the Yamuna water and wastewater irrigated soil were significantly different to those of groundwater irrigated soil. A high level of resistance against tetracycline and polymyxin B (81.2%) was observed in river water isolates. However, 87.5% of Pseudomonas isolates from soil irrigated with wastewater showed resistance to sulphadiazine, whereas 79.1% were resistant to both ampicillin and erythromycin. Isolates from soil irrigated with groundwater exhibited less resistance towards heavy metals and antibiotics as compared to those of river water and wastewater irrigated soil. Majority of the Pseudomonas isolates from water and soil exhibited resistance to multiple metals and antibiotics. Resistance was transferable to recipient Escherichia coli AB2200 strains by conjugation. Plasmids were cured with the curing agent ethidium bromide and acridine orange at sub-MIC concentration.     

Prevalence of heavy metal resistance in bacteria isolated from tannery effluents and affected soil

In the present study, a total of 198 bacteria were isolated, 88 from the tannery effluents and 110 from agricultural soil irrigated with the tannery effluents. Tannery effluents and soils were analyzed for metal concentrations by atomic absorption spectrophotometer. The tannery effluents and soil samples were found to be contaminated with chromium, nickel, zinc, copper, and cadmium. All isolates were tested for their resistance against Cr^6?+?, Cr^3?+?, Ni^2?+?, Zn^2?+?, Cu^2?+?, Cd^2?+?, and Hg^2?+?. From the total of 198 isolates, maximum bacterial isolates were found to be resistant to Cr^6?+? 178 (89.9%) followed by Cr^3?+? 146 (73.7%), Cd^2?+? 86 (43.4%), Zn^2?+? 83 (41.9%), Ni^2?+? 61 (30.8%), and Cu^2?+? 51 (25.6%). However, most of the isolates were sensitive to Hg^2?+?. Among the isolates from tannery effluents, 97.8% were resistant to Cr^6?+? and 64.8% were resistant to Cr^3?+?. Most of the soil isolates were resistant against Cr^6?+? (83.6%) and Cr^3?+? (81.8%). All isolates were categorized into Gram-positive and Gram-negative bacteria. In a total of 114 Gram-positive isolates, 91.2% were resistant to Cr^6?+? followed by 73.7% to Cr^3?+?, 42.1% to Zn^2?+?, 40.4% to Cd^2?+?, and 32.5% to Ni^2?+?. Among Gram-negative isolates, 88.1% were found showing resistance to Cr^6?+?, 75.0% to Cr^3?+?, and 47.6% were resistant to Cd^2?+?. Majority of these metal-resistant isolates were surprisingly found sensitive to the ten commonly used antibiotics. Out of 198 isolates, 114 were found sensitive to all antibiotics whereas only two isolates were resistant to maximum eight antibiotics at a time. Forty-one and 40 isolates which constitute 20.7% and 20.2% were resistant to methicilin and amoxicillin, respectively.     

Multiple metal tolerance and biosorption of cadmium by Candida tropicalis isolated from industrial effluents: glutathione as detoxifying agent

The ability of cadmium uptake by metal-resistant yeast, Candida tropicalis, from the liquid medium and wastewater was evaluated. The minimum inhibitory concentration of Cd^2?+? against C. tropicalis was 2,500 mg L^???1. The yeast also showed tolerance toward Zn^2?+? (1,400 mg L^???1), Ni^2?+? (1,000 mg L^???1), Hg^2?+? (1,400 mg L^???1), Cu^2?+? (1,000 mg L^???1), Cr^6?+? (1,200 mg L^???1), and Pb^2?+? (1,000 mg L^???1). The yeast isolate showed typical growth curves, but lag and log phases extended in the presence of cadmium. The yeast isolate showed optimum growth at 30°C and pH 8. The metal processing ability of the isolate was determined in a medium containing 100 mg L^???1 of Cd^2?+?. C. tropicalis could decline Cd^2?+? 70%, 85%, and 92% from the medium after 48, 96, and 144 h, respectively. C. tropicalis was also able to remove Cd^2?+? 40% and 78% from the wastewater after 6 and 12 days, respectively. Cd produced an increase in glutathione (GSH) and nonprotein thiol levels by 135% and 134% at 100-mg L^???1 concentration, respectively. An increase in the synthesis of GSH is involved in metal tolerance, and the presence of increasing GSH concentrations may be a marker for high metal stress in C. tropicalis. C. tropicalis, which is resistant to heavy metal ions and is adaptable to the local environmental conditions, may be employed for metal detoxification operations.     

Determination of antimicrobial and heavy metal resistance profiles of some bacteria isolated from aquatic amphibian and reptile species

The aim of the present study was to determine the level of antibiotic resistance patterns and distribution of heavy metal resistance of bacterial isolates from aquatic animals (Lissotriton vulgaris, Pelophylax ridibundus, Emys orbicularis, Mauremys rivulata, and Natrix natrix) in Turkey (Kavak Delta). A total of 153 bacteria have been successfully isolated from cloaca and oral samples of the aquatic amphibians and reptilians which were found, namely, Aeromonas sp. (n?=?29), Plesiomonas sp. (n?=?7), Vibrio sp. (n?=?12), Citrobacter sp. (n?=?12), Enterobacter sp. (n?=?11), Escherichia sp. (n?=?22), Klebsiella sp. (n?=?22), Edwardsiella sp. (n?=?6), Hafnia sp. (n?=?1), Proteus sp. (n?=?19), Providencia sp. (n?=?8), and Pseudomonas sp. (n?=?4). In terms of antibiotic and heavy metal susceptibility testing, each isolate was tested against 12 antibiotics and 4 metals. There was a high incidence of resistance to cefoxitin (46.40 %), ampicillin (44.44 %), erythromycin (35.29 %), and a low incidence of resistance to gentamicin (6.53 %), kanamycin (8.49 %), chloramphenicol (9.15 %), and cefotaxime (10.45 %). The multiple antibiotic resistance index of each bacterial species indicated that bacteria from raised amphibians and reptiles have been exposed to tested antibiotics, with results ranging from 0 to 0.58. Most isolates showed tolerance to different concentrations of heavy metals, and minimal inhibition concentrations ranged from100 to >3,200 μg/mL. According to these results, a significant occurrence of bacteria in the internal organs of reptiles and amphibians, with a high incidence of resistance against antibiotics and heavy metals, may risk aquatic animals and the public health. These data appoint the importance of epidemiological surveillance and microbiological monitoring and reinforce the need to implement environment protection programs for amphibian and reptile species.     

A field study of the relationship between sulfide-bound metals and bioaccumulation by Limnodrilus sp. in a heavily polluted river

Acid volatile sulfide (AVS) has been regarded as an important factor controlling metal bioavailability in anoxic sediments, but its effect on metal accumulation under natural conditions is poorly understood. Here, a field study of the influence of AVS on metal accumulation by Limnodrilus sp. in a heavily polluted river is provided. Most of the study area was subject to anaerobic and strongly reducing conditions, and the concentration of trace metals in surface sediments was high, as were the concentration of AVS and simultaneously extracted metals (SEM; average AVS?=?20.3 μmol g^?1, average ∑SEM₅?=?9.42 μmol g^?1; ∑SEM₅ refers to the sum of SEM_Cd, SEM_Cu, SEM_Pb, SEM_Ni, and SEM_Zn). Only a few species and small quantities of benthic invertebrates were found, and Limnodrilus sp. was dominant. There was no correlation between trace metal accumulation and (SEM-AVS), and in stations where (SEM-AVS) <0, the absolute value of bioaccumulation was high (average ∑BIO₅?=?4.07 μmol g^?1; ∑BIO₅ refers to the sum of BIO_Cd, BIO_Cu, BIO_Pb, BIO_Ni, and BIO_Zn), indicating that there was no relationship between (SEM–AVS) and metal accumulation in Limnodrilus sp. This was likely because Limnodrilus sp. ingest sediment particles as their main food source, so pore water metals play a minor role in their bioaccumulation (BIO) of materials. However, ∑BIO₅ was significantly correlated with ∑SEM₅ (r?=?0.795, p?<?0.01), revealing that the large number of sulfide-bound metals (SEM) in sediments may play an important role in metal accumulation in Limnodrilus sp., which can assimilate sulfide-associated metals by the help of the digestive fluids in the digestive systems.     

On-site solid-phase extraction and application to in situ preconcentration of heavy metals in surface water

An on-site solid-phase extraction, consisting of the sorption, the separation and the elution function units, was designed for in situ preconcentration of heavy metals ions. The D401 resin powder was employed as sorbent to capture Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Co²⁺, and Ni²⁺, and then they desorbed with 2 mol/L nitric acid as eluent. Under the optimized conditions, these heavy metals ions in West Lake, Taihu Lake, and Yangtze River of China were captured and then determined by ICP-OES with the recovery of 92.5% to 111.5%. The on-site solid-phase extraction achieved a quick preconcentration of heavy metals to avoid the transport and storage of a large volume water sample. It is suitable for in situ monitoring of water quality in mountains, tablelands or other remote areas.     

The evaluation of the association constant between R-SN and Hg2+

The effective determination of heavy metals from environmental media is among the most important issues for many industrialized countries. The interaction between RS-N, as novel heavy metal probe, and metal ions was studied. RS-N shows selective color change from colorless to pink in the presence of Hg²⁺ in methanol/water solvent and the UV–Vis study shows peak at 560 nm. Fluorescence data revealed that the fluorescence enhance of RS-N by Hg²⁺ dramatically was the result of the formation of [Hg²⁺]RS-N complex. The effective association constants (K _a ) were 3.97?×?10⁵ and 0.204?×?10⁵ M^?1 for Hg²⁺ and Cu²⁺ to RS-N, respectively. The thermodynamic parameters, enthalpy change (ΔH ⁰) and entropy change (ΔS ⁰), were calculated to be ?6.431?±?0.226 kJ/mol and ?0.129?±?0.008 J/K/mol, respectively, according to van’t Hoff equation on the basis of Gibbs free energy (ΔG ⁰) ranged from ?33.8326 to ?28.5389 kJ/mol.     

Vehicular stress a cause for heavy metal accumulation and change in physico-chemical characteristics of road side soils in Pahalgam

In an effort to determine vehicular impact on soil quality, soil samples were collected from three different zones (Pahalgam, Batakote, and Chandanwari) in Pahalgam forest ecosystem. Results showed that a significant decrease in moisture content, organic carbon, available nitrogen, and potassium was observed in nearby road side soils. However, pH was observed to be on neutral side and available phosphorus recorded high concentration. The concentration of heavy metals Pb²⁺, Cu²⁺, Zn²⁺, Ni²⁺, and Cd²⁺ estimated was also significantly high. Furthermore, concentration of Pb²⁺ at high vehicular load subzones was observed to be highest (1.168 mg/Kg) followed by Zn²⁺ (0.896 mg/Kg), Ni²⁺ (0.649 mg/Kg), Cu²⁺ (0.415 mg/Kg), and Cd²⁺ (0.079 mg/Kg). An inter-zone analysis revealed that the concentration of the heavy metals (Pb²⁺?>?Ni²⁺?>?Cd²⁺) was observed to follow the trend, Z-I?>?Z-II?>?Z-III. Variation along the temporal gradient and the impact on soil qualities were notably higher in summer. Vehicular pollution to a great extent impacts physico-chemical characteristics and more interestingly adds substantial concentration of heavy metals in soils.     

Determination of EC 50 toxicity data of selected heavy metals toward Heterocypris incongruens and their comparison to ��direct-contact�� and microbiotests

The sensitivity of Heterocypris incongruens to selected heavy metal ions is discussed. Although the Ostracodtoxkit ${\textregistered}$ has been present on the market for a few years, data on its selectivity and sensitivity to toxicants is scarce; such data is indispensable when interpreting the results of sediment toxicity. The LC₅₀ and EC₅₀ results with the Ostracodtoxkit ${\textregistered}$ are compared with those obtained with other commercially available ??direct-contact?? tests (utilizing Hyalella azteca and Chironomus riparius) and microbiotests for assessing the toxicity of aqueous samples (Vibrio fischeri, Daphnia magna, and Selenastrum capricornatum). The sensitivity of H. incongruens to metal ions (Cd^2?+?>?>Hg^2?+?> Cu^2?+?>Cr^6?+?>Ni^2?+???Mn^7?+?>Zn^2?+?>Pb^2?+?>Li^1?+?> Fe^3?+?) was found to be similar to that of H. azteca and of C. riparius. The Ostracodtoxkit ${\textregistered}$ has shown itself to be an efficient and reliable element of test batteries for toxicity determination.     

Monitoring toxic cyanobacteria and cyanotoxins (microcystins and cylindrospermopsins) in four recreational reservoirs (Khon Kaen, Thailand)

The toxic cyanobacterial communities of four recreational reservoirs (Bueng Kaen Nakhon, Bueng Thung Sang, Bueng Nong Khot, and Bueng See Than) in Amphur Muang, Khon Kaen Province, Thailand, were investigated. Water samples were collected via monthly sampling from June to October 2011 for the study on the diversity and density of toxic cyanobacteria and toxin quantification. The main toxic cyanobacteria present in these reservoirs were Aphanocapsa sp., Cylindrospermopsis sp., Leptolyngbya sp., Limnothrix sp., Microcystis sp., Oscillatoria sp., Planktolyngbya sp., Planktotrix sp., and Pseudanabaena sp. The dominant bloom-forming genera in the water samples from Bueng Nong Khot and Bueng See Than were Microcystis sp. and Cylindrospermopsis sp., respectively. Enzyme-linked immunosorbent assays specific for cyanotoxins were performed to detect and quantify microcystins and cylindrospermopsins, with the highest average microcystins content (0.913 μgL^?1) being found in the sample collected from Bueng Nong Khot and the highest average cylindrospermopsins content (0.463 μgL^?1) being found in the sample collected from Bueng See Than. The application of 16S rRNA analyses to cyanobacterial isolates BKN2, BNK1, BNK2, and BST1 indicated that these isolates are most closely related to Limnothrix planctonica (JQ004026) (98 % similarity), Leptolyngbya sp. (FM177494) (99 % similarity), Microcystis aeruginosa (DQ887510) (99 % similarity), and Limnothrix redekei (FM177493) (99 % similarity), respectively.     

The levels and composition of persistent organic pollutants in alluvial agriculture soils affected by flooding

The concentrations and composition of persistent organic pollutants (POPs) were determined in alluvial soils subjected to heavy flooding in a rural region of Poland. Soil samples (n?=?30) were collected from the upper soil layer from a 70-km² area. Chemical determinations included basic physicochemical properties and the contents of polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and polycyclic aromatic hydrocarbons (PAHs, 16 compounds). The median concentrations of Σ7PCB (PCB28?+?PCB52?+?PCB101?+?PCB118?+?PCB138?+?PCB153?+?PCB180), Σ3HCH (α-HCH?+?β-HCH?+?γ-HCH) and Σ3pp′(DDT?+?DDE?+?DDD) were 1.60?±?1.03, 0.22?±?0.13 and 25.18?±?82.70 μg kg^?1, respectively. The median concentrations of the most abundant PAHs, phenanthrene, fluoranthene, pyrene, benzo[b]fluoranthene and benzo[a]pyrene were 50?±?37, 38?±?27, 29?±?30, 45?±?36 and 24?±?22 μg kg^?1, respectively. Compared with elsewhere in the world, the overall level of contamination with POPs was low and similar to the levels in agricultural soils from neighbouring countries, except for benzo[a]pyrene and DDT. There was no evidence that flooding affected the levels of POPs in the studied soils. The patterns observed for PAHs and PCBs indicate that atmospheric deposition is the most important long-term source of these contaminants. DDTs were the dominant organochlorine pesticides (up to 99 %), and the contribution of the parent pp′ isomer was up to 50 % of the ΣDDT, which indicates the advantage of aged contamination. A high pp′DDE/pp′DDD ratio suggests the prevalence of aerobic transformations of parent DDT. Dominance of the γ isomer in the HCHs implies historical use of lindane in the area. The effect of soil properties on the POP concentrations was rather weak, although statistically significant links with the content of the <0.02-mm fraction, C_total or N_total were observed for some individual compounds in the PCB group.     

Impact of ultrasonic treatment on dewaterability of sludge during Fenton oxidation

Fenton oxidation was compared with Fenton oxidation coupled with ultrasonication (Fenton?+?US) for sludge dewatering. Different Fenton reagent (H₂O₂, Fe²⁺) concentrations, pH, and reaction times were studied in different systems on the basis of the specific resistance to filtration (SRF) and capillary suction time (CST). It was found that Fenton?+?US can significantly reduce Fe²⁺ and H₂O₂ dosages and reaction times. After ultrasonication of the system at pH 3, with an ultrasonic frequency of 25 kHz and a sound energy density of 100 W/L, the Fe²⁺, H₂O₂ dosage, and reaction time were reduced by 66.7, 75.0, and 75.0 %, respectively, when compared with Fenton oxidation at the same dewaterability of sludge. The microstructure of sludge and hydroxyl radical (·OH) density in Fenton oxidation and Fenton?+?US was further examined. Fenton?+?US produced more?·?OH in a sludge system than did individual Fenton oxidation. The concentration of?·?OH in Fenton?+?US fell from 79.2 to 6 mg/L over 3.5 h, while the concentration of?·?OH in Fenton oxidation fell from 59.6 to 1 mg/L over 2 h, thus destroying the microstructure of sludge more effectively. Sludge treated using Fenton?+?US for 30 min showed a much thinner and looser microstructure.     

Determination of trace transition metals in environmental matrices by chelation ion chromatography

Trace transition metals (Fe^3?+?, Mn, Cu, Cd, Co, Zn, Ni) in environmental samples were analyzed by chelation ion chromatography using a mixed bed ion-exchange column with pyridine-2,6-dicarboxylic acid (PDCA) and oxalic acid as eluent and large volume direct injection (1,000 ??l). The two eluents, PDCA and oxalic acid, were tested, and repeatability and detection limits were compared. The total analysis time was ~15 min. The separation with PDCA was more successful than that obtained with acid oxalic. It was observed that utilizing PDCA resulted in lower detection limits, higher repeatability, and a quantitative detection of Cd and Mn, which coelute as a single peak when using the oxalic acid. At last, the PDCA calibration graphs resulted linear (r ²?>?0.999) in the range 0.4?C1,000 ??g/L. The procedure was applied to the analysis of metals in soils and in water samples. The results obtained from the analysis of natural waters have demonstrated that the method is simple and efficient, therefore, can be used for the determination of metals in natural waters using a continuous and automatic monitoring system.     

An assessment of contamination of the Fusaro Lagoon (Campania Province,southern Italy) by trace metals

The Fusaro Lagoon is a shallow lagoon, located in SW Italy, largely influenced in the last decades by several anthropic impacts. The study examined the pollution status of the lagoon, during year 2011–2012 at nine sampling stations with the aim to find out proper measurements of water lagoon restoration. Concentrations of heavy metals (HMs) (aluminium [Al], barium [Ba], cadmium [Cd], copper [Cu], iron [Fe], manganese [Mn], vanadium [V] and zinc [Zn]) were examined in water, sediments and specimens of the ascidian Ciona intestinalis sp. A. Low levels of dissolved oxygen concentration were detected at many stations, with mean values of 5.2–6.4 mg L^?1. The redox potential of surface waters was also low, ?2.7 to 50.7 mV. Sediments possessed high organic matter content, 17.7–29.4 %. In sediments, the mean Zn level, 251.4 mg kg^?1, was about sixfold higher than that recorded in year 2000 (38.5 mg kg^?1) and considerably higher than that recorded in 2007 (191 mg kg^?1). The mean levels of Cd were outstandingly high, with a mean value of 70.5 mg kg^?1, about 30- and 50-fold higher than those determined in 2000 and 2007, respectively. Cadmium (Cd), Cu and nickel (Ni) appeared in excess with respect to most current guidelines, reaching significant pollution levels. C. intestinalis sp. A was detected only at few stations, with metals accumulated preferentially in the body in respect to the tunic, from 1.2 times for Zn (178 mg kg^?1) to 4.0 times for V (304 mg kg^?1). Data suggests the necessity of an immediate action of eco-compatible interventions for environmental restoration.     

Heavy metals in the habitat and throughout the food chain of the Neotropical otter, Lontra longicaudis, in protected Mexican wetlands

Top predators like the Neotropical otter, Lontra longicaudis annectens, are usually considered good bioindicators of habitat quality. In this study, we evaluated heavy metal contamination (Hg_tot, Pb, Cd) in the riverine habitat, prey (crustaceans and fish), and otter feces in two Ramsar wetlands with contrasting upstream contamination discharges: Río Blanco and Río Caño Grande in Veracruz, Mexico, during the dry, the wet, and the nortes seasons. Most comparisons revealed no differences between sites while seasonal differences were repeatedly detected for all of the compartments. Higher concentrations of Pb during the dry season and of Cd during the wet season in otter feces mirrored differences detected in the most seasonally consumed prey. Compared with fecal methylmercury values reported for the European otter (0.25–0.75 mg kg^?1) in unprotected areas, the Hg_tot levels that we measured were lower (0.02–0.17 mg kg^?1). However, Pb (117.87 mg kg^?1) and Cd (9.14 mg kg^?1) concentrations were higher (Pb, 38.15 mg kg^?1 and Cd, 4.72 mg kg^?1) in the two Ramsar wetlands. Protected areas may shelter species, but those with water-linked diets may suffer the effect of chemicals used upstream.     

31P-NMR evaluation of organophosphorus pesticides degradation through metal ion promoted hydrolysis

The degradation of some organophosphorus pesticides (OPPs) in the presence of metal ions was studied by ³¹P-NMR spectroscopy. Both ³¹P-NMR and gas chromatography/mass spectroscopy results were used in order to determine the nature of metabolites formed after degradation. The degraded organophosphorus pesticide were investigated for chlorpyrifos and phoxim in the presence of several metal ions including Hg²⁺, Cu²⁺, Cd²⁺, Ni²⁺, Pb²⁺, and Ag⁺. ³¹P-NMR results indicated Ag⁺ and Hg²⁺ ion promoted degradation of OPPs and other metal ions formed complex with OPPs and cannot degrade OPPs. We found that the degradation of chlorpyrifos and phoxim with Ag⁺ or Hg²⁺ led to the formation of O,O-diethyl-O-methyl phosphorothionate, (C₂H₅O)₂(CH₃O)PS, at metal ion/pesticide mole ratios ≤1.0 and completely decomposed at a higher mole ratio of 10. Finally, the method was successfully applied to the degradation study of a number of technical and formulated pesticides in the presence of Ag⁺ ion at a metal ion/pesticide mole ratio of 10.     

The prevalence of bacterial resistance in clinical, food, water and some environmental samples in Southwest Nigeria

The resistance pattern and mechanisms of bacterial isolates obtained from clinical origin, soil, industrial effluent, orange juice products and drinking water were studied using commonly used antibiotics. The microbial load of the water samples, industrial effluent and orange juice products were 1.0 × 10¹–2.25 × 10⁶, 2.15 × 10⁵, and 3.5 × 10⁴–2.15 × 10⁵ cfu mL^–1, respectively. The faecal coliform test revealed that only two out of twenty orange juice products had MPN of 2 and 20, the MPN of water ranged from 1–1800, while the effluent had MPN of 1800. The bacterial isolates that were isolated include E. coli, S. aureus, P. vulgaris, S. marcescens, S. pyogenes, B. cereus, B. subtilis, Micrococcus sp., Klebsiella sp., P. aeruginosa, and Enterobacter sp. Also, clinical and soil isolates of P. aeruginosa were used in the study. Among the eight antibiotics tested for resistance on five strains of each bacterium, seven different resistance patterns were observed among the bacterial isolates obtained from water, effluent and orange juice products. Among the clinical and soil isolates of P. aeruginosa, four multiple-drug resistance patterns were obtained. Thirty strains of E. coli and S. aureus were tested for -lactamase production and fourteen strains, seven each of E. coli and S. aureus that had high Minimum Inhibitory Concentration values (MIC) for both Amoxycillin and Cloxacillin were positive.     

Discriminant analysis for the prediction of sand mass distribution in an urban stormwater holding pond using simulated depth average flow velocity data

The approach of this paper is to predict the sand mass distribution in an urban stormwater holding pond at the Stormwater Management And Road Tunnel (SMART) Control Centre, Malaysia, using simulated depth average floodwater velocity diverted into the holding during storm events. Discriminant analysis (DA) was applied to derive the classification function to spatially distinguish areas of relatively high and low sand mass compositions based on the simulated water velocity variations at corresponding locations of gravimetrically measured sand mass composition of surface sediment samples. Three inflow parameter values, 16, 40 and 80 m³ s^?1, representing diverted floodwater discharge for three storm event conditions were fixed as input parameters of the hydrodynamic model. The sand (grain size?>?0.063 mm) mass composition of the surface sediment measured at 29 sampling locations ranges from 3.7 to 45.5 %. The sampling locations of the surface sediment were spatially clustered into two groups based on the sand mass composition. The sand mass composition of group 1 is relatively lower (3.69 to 12.20 %) compared to group 2 (16.90 to 45.55 %). Two Fisher’s linear discriminant functions, F ₁ and F ₂, were generated to predict areas; both consist of relatively higher and lower sand mass compositions based on the relationship between the simulated flow velocity and the measured surface sand composition at corresponding sampling locations. F ₁?=??9.405?+?4232.119?×?A???1795.805?×?B?+?281.224?×?C, and F ₂?=??2.842?+?2725.137?×?A???1307.688?×?B?+?231.353?×?C. A, B and C represent the simulated flow velocity generated by inflow parameter values of 16, 40 and 80 m³ s^?1, respectively. The model correctly predicts 88.9 and 100.0 % of sampling locations consisting of relatively high and low sand mass percentages, respectively, with the cross-validated classification showing that, overall, 82.8 % are correctly classified. The model predicts that 31.4 % of the model domain areas consist of high-sand mass composition areas and the remaining 68.6 % comprise low-sand mass composition areas.     

Observational and modeling study of dry deposition on surrogate surfaces in a South China city: implication of removal of atmospheric crustal particles

Dry deposition samples collected during 1999–2001 at a South China site using surrogate surfaces were analyzed by capillary electrophoresis. Collector surface properties played important roles to the dry deposition. The deposition velocities for various species ranged from 0.02 to 1.69 cm s^???1, in general agreement with literature values. More than 90% of Ca^2?+? was deposited by sedimentation and its comparable values of dry or wet removal residence times imply that dry deposition is an important atmospheric removal process for the ubiquitous crustal species in South China, compared with precipitation scavenging. Relatively good agreement was found when the species deposition velocities were modeled based on up-to-date knowledge of particle dry deposition. The total depositions for anthropogenic and crustal species in northern China are likely to be much higher than those in the south, including our site where the fluxes of the acidic species SO₄ ^2??? and NO₃ ^??? were 4.4 and 2.2 g m^???2 year^???1, respectively. The sum of dry deposition for cations Na^?+?, Ca^2?+?, Mg^2?+?, and K^?+? contributes 44% of the total flux, which is equivalent to the value estimated in Europe.     

Seasonal variation, source, and regional representativeness of the background aerosol from two remote sites in western China

Using observations from two remote sites during July 2004 to March 2005, we show that at Akdala (AKD, 47° 06′ N, 87° 58′ E, 562 m asl) in northern Xinjiang Province, there were high wintertime loadings of organic carbon (OC), elemental carbon (EC), and water-soluble (WS) ${\rm SO}_{4}^{2-}$ , ${\rm NO}_{3}^{2-}$ , and ${\rm NH}_{4}^{+}$ , which is similar to the general pattern in most areas of China and East Asia. However, at Zhuzhang (ZUZ, 28° 00′ N, 99° 43′ E, 3,583 m asl) in northwestern Yunnan Province, the aerosol concentrations and compositions showed little seasonal variation except for a decreasing trend of OC from August to autumn–winter. Additionally, the OC variations dominated the seasonal variation of PM₁₀ (particles ≤10 μm diameter) level. Chemical characteristics combined with transport information suggested sea salt origin of ionic Na^?+?, Mg^2?+?, and Cl^??? at ZUZ. At AKD, ionic Ca^2?+?, Mg^2?+?, Na^?+?, and Cl^??? primarily originated from salinized soil. Furthermore, the WS Ca^2?+? contributions (5.4–6%) to the PM₁₀ mass during autumn, winter, and early spring reflected a constant dust component. The results of this study indicated that both sites were regionally representative. However, the representative regions and scales of these background sites may vary seasonally as the regional atmospheric transport patterns change. Seasonal variations in the background aerosol levels from these two areas need to be considered when evaluating the regional climate effects of the aerosols.