摘要:

Secondary‐treated, filtered, and chlorinated effluent (R‐l quality) blended with potable water was used for turf grass irrigation at the Hawaii Kai Golf Course on the island of Oahu, Hawaii. Blending was required because of the salinity level in the R‐l effluent. For control, only potable water was used for irrigation. Irrigation amounts varied with time based upon rainfall. Suction lysimeters were installed at 25‐cm and 40‐cm depths to collect soil‐water samples. In addition, water samples from potable water and blended water storage impoundments were collected for analysis. All water samples were analyzed for nitrate, chemical oxygen demand, pH, conductivity, and fecal coliform bacteria density. Grass samples and soil samples were analyzed for fecal bacteria. Results indicated that fertilization of the turf affected the nitrate content of certain suction lysimeter samples. Conductivity of the leachate samples decreased with time, indicating possible dilution with rainwater. The most significant observation was the growth of fecal bacteria in leachate waters and open storage reservoirs. Grass and soil samples also showed the presence of fecal coliform bacteria. This indicates that fecal coliforms should not be used as indicator bacteria in tropical environments, where they are naturally present. For Oahu, using fecal coliforms as indicator bacteria can be a problem if R‐l effluent is used on areas overlying potable water aquifers.Clostridium perfringens,which is present in large numbers in wastewaters, may be a better indicator bacterium since it is not found in large numbers in the natural soil environment.

ISSN:1093-4529    

DOI:10.1080/10934520009377015

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A column leaching study was conducted using a Riviera fine sand (Loamy, siliceous, hyperthermic, Arenic Glossaqualf), sampled at 30 cm increments to 150 cm depth, from a commercial grapefruit grove to evaluate the effects of leaching solution properties on the leaching of Zn, Cu, Mn, Fe, Ca, and Mg in seven pore volumes of leachate. The concentration of Cu in the leachate was highest in the surface horizon (0–30 cm), indicating its limited transport down the soil profile. The concentration of Zn was significantly greater in the 30–60 cm depth sample than at the other depths. The peak concentrations of Fe and Mn were found in the 60–90 cm depth while those of Ca and Mg were in the 120–150 cm depth. The concentrations of the above metals and cations were significantly correlated with those of Mehlich 3 extractable elements in the soil. The addition of N, P, and K to the leaching solution increased the Zn, Mn, Ca, and Mg concentrations, but decreased Fe and Cu concentrations in the leachate. The concentrations of Ca, Mg, and Mn in the leachate were positively correlated, while those of Cu and Fe were negatively correlated with electrical conductivity of the leachate. The cumulative amounts of metals in the leachate increased with an increase in the pore volume of the leachate. The leaching solution pH was negatively correlated with concentrations of Zn, Mn, Fe, and positively correlated with concentration of Ca in the leachate.

ISSN:1093-4529    

DOI:10.1080/10934520009377016

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Limonene, one of the most prevalent monoterpenes in indoor environment, was evaluated as an indicator of environmental air‐quality. Its association with health symptoms reported by workers was assessed from six large office‐buildings in the Midwestern USA that were identified as ‘non‐complaint’. The two‐year study from November 1996 to October 1998 focussed on monitoring 60 chemicals containing various functional groups including alcohol, aliphatic and aromatic hydrocarbons, alkene, carbonyl, ether, and halo‐hydrocarbons. Arithmetic mean of the reported number of physical symptoms was 3.4 ± 1.3 from a health symptoms‐questionnaire containing 19 items and 657 total responses. Wilcoxon‐sign and rank‐sum scores, and Kruskal‐Wallis (K‐W) tests did not indicate a significant association between the six buildings and the total number of symptoms identified by responses (K‐W χ2=0.5, df = 5, pH0= 0.99) or an association between the four seasons and mean number of symptoms (K‐W χ2= 2.7, df = 3, pH0= 0.43). Levels of concentration of odorous or irritant chemicals including n‐butyl acetate, aliphatic hydrocarbons, aromatic hydrocarbons and formaldehyde in all six buildings were different, while limonene, pinene and n‐ethyl acetate were not significantly different (K‐W χ2“limonene=3.5, df = 5, p = 0. 61), suggesting a random geographical‐distribution of limonene. Wilcoxon‐sign and rank‐sum scores, and K‐W tests further indicated only indoor limonene level was significantly higher in winter (0.76 ± 0.28 ppbv) than in summer, spring or fall (0.44 ± 0.07, 0.41 ± 0.08 and 0.33 ± 0.10 ppbv respectively; K‐W χ2= 7.1, df = 3, p = 0.07). Spearman correlation test suggested an apparent association between the mean number of symptoms with limonene (Rs= 0.48, pH0= 0.04), sum‐aliphatics (SAL) (Rs = 0.48, pH0= 0.04) and n‐butyl acetate (Rs = 0.51, pHo = 0.03). Limonene and pinene cause no irritation or CNS symptoms from short‐term exposures, but cause significant reduction in vital capacity at concentrationca. 8.0 x 104ppbv in humans (F‐Filipsson et al., J. Toxicol. Environ. Health,38, 77–88 (1993)). Limonene's oxidative product, epoxide, is known to cause upper respiratory and CNS symptoms, and dermatitis. Mean number of reported symptoms had a negative Spearman‐correlation for formaldehyde (Rs = ‐0.13, pH0= 0.60), although it is known for its upper respiratory irritation, allergy and sensitization reaction. Limonene levels correlated least with formaldehyde. Limonene levels in the six study buildings were in the range 0.2 to 1.5 ppbv, four orders of magnitude less than the recommended exposure limit for non‐industrial indoor work‐environment, 3.0 x 104ppbv. Random distribution of low levels limonene indoor and its positive correlation with other volatile organic compounds having different functional groups including aliphatics and esters suggest that limonene levels in indoor air should be an effective marker and an indicator of environmental air‐quality. Limonene levels also correlate with health symptoms that are positively identified with most prevalent upper respiratory health symptoms including dry, itching or irritated eyes (41%) and tired or strained eyes (37%), and headache (CNS‐symptom) (36%) reported by the workers.

ISSN:1093-4529    

DOI:10.1080/10934520009377017

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A simple three‐pitcher (locally known as ‘3‐kalshi') filtration assembly made entirely from readily available local materials is tested for its efficacy in removing arsenic from the groundwater of Bangladesh. In a 3‐ kalshi assembly, the first kalshi has iron chips and coarse sand, the second kalshi has wood charcoal and fine sand, and the third kalshi is the collector for filtered water. About 240 L of arsenic contaminated groundwater and groundwater spiked with high concentrations of both As(III) and As(V) were filtered. Analytical measurements were performed by using anodic stripping voltammetry (ASV) for trace level As(III) and As(total) and redox potential. Atomic absorption spectrometry with graphite furnace and Zeeman background correction (AASGF‐Z) and inductively coupled plasma atomic emission spectrometry (ICPAES) were used to validate measurements of arsenic and measure 24 other metals before and after filtration. Total Fe, ionic conductivity, Eh, pH, temperature and flow rates were measured at various stages of the filtration process. It has been shown that more toxic As(III) can be removed from 800 ppb to below the detection limit of 2 ppb. The As(total) can be removed to a concentration below 10 ppb for most samples even at the highest input concentration of 1100 ppb As(total). The dissolved iron concentration decreased from an average 6000 ppb to 200 ppb. Calculations based on compound formation and arsenic adsorption on hydrous ferric oxide show that, with a constant input of dissolved iron the arsenic removal capacity increases linearly with each filtration. Although the role of metallic iron was difficult to quantitate, it provided excess soluble iron in the filtering media of the second kalshi. The wood charcoal was used to remove any organic impurities that may be present in groundwater. The redox potential change shows speciation of iron in agreement with literature data. The decrease in conductivity by 35% of the original value indicates substantial removal of dissolved ions. This is also supported by ICPAES measurement. The filtered water remained crystal clear for months and free from most toxic metal ions. The daily capacity of the 3‐kalshi system varies from 42–148 L/day. The final water quality meets and exceeds the guideline values suggested by USEPA, World Health Organization and Bangladesh. We suggest the use of this simple setup to make potable water.

ISSN:1093-4529    

DOI:10.1080/10934520009377018

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The objective of this study was to develop and evaluate electrochemically‐enhanced immobilization of radionuclides in contaminated groundwater using Fe°. A bench‐scale flow‐through Fe° reactor column with direct current was tested to increase the efficiency and effective life of the Fe° medium by (i) providing an external supply of electrons, (ii) controlling the rate of iron oxidation, and (iii) enhancing the rate of radionuclide immobilization. The removal mechanism appears to be reductive coprecipitation of radionuclides by iron oxidation by creating a reducing environment in the reactive iron barrier. Several factors influence the removal of radionuclides from groundwater using this reactor column including electrode configuration, applied voltage, distance between cathode and anode, and radionuclide concentration.

ISSN:1093-4529    

DOI:10.1080/10934520009377019

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The objective of this study was to develop and evaluate electro‐enhanced dechlorination of trichloroethene (TCE) in groundwater using Fe°. A bench‐scale flow‐through Fe° reactor column with direct current was tested to increase the efficiency of Fe° medium by providing an external supply of electrons. The bench‐scale column tests confirmed that the application of direct current with Fe° was highly effective in enhancing the rate of TCE dechlorination. The t1/2for the TCE dechlorination without current was 10.3 hours and the t1/2for the TCE dechlorination with current was about 1 hour. The dechlorination mechanism appears to be reductive dechlorination, with the electrons supplied by the iron oxidation and external direct current power supply serving as the source of the electrons.

ISSN:1093-4529    

DOI:10.1080/10934520009377020

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The diurnal variability ofAureoumbra lagunensis,dissolved metals (Cd, Pb, Mn, Cr, Cu, Zn, Ni, Se, and Fe), and environmental parameters (salinity, temperature, turbidity, pH, and dissolved oxygen) were studied to understand the role of metals in the occurrence of the Texas “brown tide.” TheA. lagunensisdensities were high in the afternoon; suggesting the influence of light on the growth ofA. lagunensis. The results indicate that metals, Cd, Pb, Mn, Cr, and Se may not be influencing the growth ofA. lagunensis. The dissolved Cu, Zn, and Ni concentrations were inversely related withA. lagunensisdensities while Fe had positive relationship withA. lagunensis. The spectroscopic characterization of the surfaces ofA. lagunensissuggests that these metals might be playing a role in the occurrence of Texas “brown tide” through involvement of ‐OH and ‐CH functional groups on the surfaces ofA. lagunensis.

ISSN:1093-4529    

DOI:10.1080/10934520009377021

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Environmental data, including information regarding soil heavy metals, may contain significant uncertainty and exhibit a skewed distribution with a complex and unexplainable spatial variation. This study identified the spatial patterns and variations of soil heavy metals (Cu, Cd, Hg, and Pb) in the northern part of Changhua County in Taiwan to clarify the characteristics and pollution of soil heavy metals. The spatial maps of soil heavy metals were also estimated and simulated using kriging and simulated annealing methods. Correlation analysis indicated that Pearson and Spearman correlation coefficients among these four heavy metals were significant; between Cd and Cu, these two correlation coefficients were strongly significant. As expected, the spatial maps of estimation and simulation of soil heavy metals revealed high concentration areas of Cd, Cu along the main irrigation‐ditch system and surrounding industrial plants in the area of study. In addition to reproducing the spatial variation of the investigated Cd, Cu, Hg and Pb, simulated annealing could also identify the global spatial continuity and discontinuity patterns of soil heavy metals. Kriging and simulated annealing methods can both be applied to identify pollution sources and patterns for monitoring and remedy.

ISSN:1093-4529    

DOI:10.1080/10934520009377022

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Electrokinetic technology was conducted on three copper contaminated soils to investigate the potential use of this technology for soil remediation. Several variables, such as adsorption capacity of the soils, fractions of copper in the soils, reaction time, pH and injection of conducting solutions into the soils that may affect the removal efficiency of electrokinetic process were studied. The results showed that the electrokinetic process has the potential to remove carbonate and Fe‐Mn oxides’ copper in contaminated soils, which accounts for 70–85% of copper in the soils. With 8 volts of electrification for 30 days, the highest removal efficiency was found in an acidic clay soil mixed with 0.1 N of HC1 conducting solution. This study suggests that the higher adsorption capacity and the lower saturated basic soils produce lower removal efficiency. In order to increase removal efficiency, injection of strong acid into the specimen seems to be a promising solution. Strong acid solutions prevent the precipitation of copper hydroxide in the specimen and support the ion desorbed from the soils, which result in increasing the removal efficiency by 40%.

ISSN:1093-4529    

DOI:10.1080/10934520009377023

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This study was aimed to evaluate the quantity and bioavailability of five metals from five contaminated soils. A selective sequential fractionation procedure was used to separate the metals into six groups: water soluble, exchangeable, carbonate, Fe‐Mn oxide, organic, and residual. The residual fraction was the most abundant only for Pb in most soils, suggesting that Pb was probably more stable and less bioavailable in these soils. Lead, Cd, and Cu were not detected in the water‐soluble fraction of most soils. Although the greatest amounts of Zn and Cu in the non‐residual fraction were in general associated with the Fe‐Mn oxide fraction, and Ni with the organic fraction, an appreciable percentage of these metals were concentrated in the exchangeable or the carbonate bound fraction. As metal behavior in the environment is dependent upon its solubility and mobility in soils, the potential hazard of these metals in these contaminated soils was assessed in this study.

ISSN:1093-4529    

DOI:10.1080/10934520009377024

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor