Phosphorus supply influences heathland responses to atmospheric nitrogen deposition

On an upland moor dominated by pioneer Calluna vulgaris and with an understorey of mosses and lichens, experimental plots were treated with factorial combinations of nitrogen (N) at +0 and +20kg Nha(-1)yr(-1), and phosphorus (P) at +0 and +5kg Pha(-1)yr(-1). Over the 4-year duration of the experiment, the cover of the Calluna canopy increased in density over time as part of normal phenological development. Moss cover increased initially in response to N addition but then remained static; increases in cover in response to P addition became stronger over time, eventually causing reductions in the cover of the dominant Calluna canopy. Lichen cover virtually disappeared within 4 years in plots receiving +20kg Nha(-1)yr(-1) and also in separate plots receiving +10kg Nha(-1)yr(-1), but this effect was reversed by the addition of P.     

Fecal source tracking by antibiotic resistance analysis on a watershed exhibiting low resistance

The ongoing development of microbial source tracking has made it possible to identify contamination sources with varying accuracy, depending on the method used. The purpose of this study was to test the efficiency of the antibiotic resistance analysis (ARA) method under low resistance by tracking the fecal sources at Turkey Creek, Oklahoma exhibiting this condition. The resistance patterns of 772 water-isolates, tested with nine antibiotics, were analyzed by discriminant analysis (DA) utilizing a five-source library containing 2250 isolates. The library passed various representativeness tests; however, two of the pulled-sample tests suggested insufficient sampling. The resubstitution test of the library individual sources showed significant isolate misclassification with an average rate of correct classification (ARCC) of 58%. These misclassifications were explained by low antibiotic resistance (Wilcoxon test P < 0.0001). Seasonal DA of stream E. coli isolates for the pooled sources human/livestock/deer indicated that in fall, the human source dominated (P < 0.0001) at a rate of 56%, and that human and livestock respective contributions in winter (35 and 39%), spring (43 and 40%), and summer (37 and 35%) were similar. Deer scored lower (17–28%) than human and livestock at every season. The DA was revised using results from a misclassification analysis to provide a perspective of the effect caused by low antibiotic resistance and a more realistic determination of the fecal source rates at Turkey Creek. The revision increased livestock rates by 13–14% (0.04 ≤ P ≤ 0.06), and decreased human and deer by 6–7%. Negative misclassification into livestock was significant (0.04 ≤ P ≤ 0.06). Low antibiotic resistance showed the greatest effect in this category.     

Vanadium recovery from oil fly ash by leaching, precipitation and solvent extraction processes

In order to reduce the environmental impact due to land disposal of oil fly ash from power plants and to valorize this waste material, the removal of vanadium was investigated using leaching processes (acidic and alkaline treatments), followed by a second step of metal recovery from leachates involving either solvent extraction or selective precipitation. Despite a lower leaching efficiency (compared to sulfuric acid), sodium hydroxide was selected for vanadium leaching since it is more selective for vanadium (versus other transition metals). Precipitation was preferred to solvent extraction for the second step in the treatment since: (a) it is more selective; enabling complete recovery of vanadate from the leachate in the form of pure ammonium vanadate; and (b) stripping of the loaded organic phase (in the solvent extraction process) was not efficient. Precipitation was performed in a two-step procedure: (a) aluminum was first precipitated at pH 8; (b) then ammonium chloride was added at pH 5 to bring about vanadium precipitation.     

Biomonitoring of heavy metals by pollen in urban environment

Abstract Industrial development and consumption of petroleum products leads to increase air pollution levels especially in urban and industrial areas. Heavy metal components associated with air pollutants have far reaching effects with respect to economic and ecological importance of pollens. The pollens are male reproductive organs of the plant and travel through air from flower to flower for pollination purpose. During this period they are exposed to air pollutants. Present investigation thus pertains to study of effect of air pollutants on pollens especially biosorption and bioaccumulation of heavy metals. The pollens of three commonly occurring plants namely Cassia siamea, Cyperus rotundus, Kigelia pinnata have been studied from the NH-6 of Nagpur city, India. The pollens exposed to polluted air showed the presence of higher concentrations of Ca, Al and Fe as compared to unexposed pollens. Higher concentration of these metals was observed in Cyperus rotundus followed by Cassia siamea and Kigelia pinnata. These results indicate that pollens act as good indicator of air pollution giving results in short time of exposure of 5–10 h. Apart from this, it is also reported that some of these metals play crucial role in the metabolic activity in pollens for example Calcium is necessary for growth of pollen tube and other metabolic activities in pollens. The presence of these metals in pollens may also enhance the allergenicity of the pollens. Similarly accumulation of heavy metals may also deteriorate the quality of pollen for their economical use. The viability of pollen is also affected by these pollutants in sensitive species leading to impairment of their fertility.     

Comparison of models of simazine transport and fate in the subsurface environment in a citrus farm

Contamination of groundwater by agrochemicals is now widely recognized as an extremely important environmental problem. Modern agricultural practices involve the combined use of irrigation with the application of large amounts of agrochemicals to maximize crop yield. Due to flood irrigation and natural runoff, agricultural activities might generate soil, surface water and groundwater contamination problems and leaching of pesticides. Modeling of the transport and fate of pesticides, such as simazine, may help understand the long-term potential risk to the subsurface environment. This paper illustrates a comparative study via the use of three different pesticide transport simulation models and the applicability of those models in determining the groundwater vulnerability to pesticides contamination in a citrus orchard located at the Lower Rio Grande Valley (LRGV). The three models used in the study are the pesticide root zone model-3 (PRZM-3), the pesticide analytical model (PESTAN) and integrated pesticide transport modeling (IPTM). The concentration values obtained from all three models are in agreement, and they show a decreasing trend from the surface through the vadose zone. The problem is how to use this information and, specifically, how to combine the testimony of a number of experts into a single useful judgment. With the aid of the fuzzy multiattribute decision making method, PRZM-3 is deemed as the most promising one for such precision farming applications.     

A directional passive air sampler for monitoring polycyclic aromatic hydrocarbons (PAHs) in air mass

A passive air sampler was developed for collecting polycyclic aromatic hydrocarbons (PAHs) in air mass from various directions. The airflow velocity within the sampler was assessed for its responses to ambient wind speed and direction. The sampler was examined for trapped particles, evaluated quantitatively for influence of airflow velocity and temperature on PAH uptake, examined for PAH uptake kinetics, calibrated against active sampling, and finally tested in the field. The airflow volume passing the sampler was linearly proportional to ambient wind speed and sensitive to wind direction. The uptake rate for an individual PAH was a function of airflow velocity, temperature and the octanol-air partitioning coefficient of the PAH. For all PAHs with more than two rings, the passive sampler operated in a linear uptake phase for three weeks. Different PAH concentrations were obtained in air masses from different directions in the field test.     

Behavior of an aerated submerged fixed-film reactor (ASFFR) under simultaneous organic and ammonium loading

The performance of an aerated submerged fixed-film reactor (ASFFR) under simultaneous organic and ammonium loading and its effect on nitrification was studied. Organic loadings varied in the range of 1.93 to 5.29 g chemical oxygen demand (COD) m-2 d-1 and NH4-N loadings were in the range of 116 to 318 mg NH4-N m-2 d-1. Increments of loading rates were obtained both by increasing the flow rate and increasing the influent substrate in individual pilot runs. Results showed that with organic loading rates up to 3.97 g COD m-2 d-1, complete nitrification was achievable. Although high organic loading such as 5.29 g COD m-2 d-1 could cause nitrification to stop, shifting to lower organic loadings made nitrification start and set rapidly to its previous steady-state concentrations. Comparison of results showed that in the ASFFR, nitrification would be severely affected by an organic loading rate of 5.29 g COD m-2 d-1 by increasing either the flow or the influent substrate. It should be noted that the average value of dissolved oxygen was 3.4 mg L-1 with an air supply of 15 L min-1, and there was no indication of oxygen limitation. The results of this study show the flexibility of ASFFRs under changing organic loads. Furthermore, for achieving complete nitrification and optimum application of these reactors for protecting receiving water from the environmental hazards of ammonium, the maximum organic loading that would present complete nitrification should be considered.     

Lichen and moss bags as monitoring devices in urban areas. Part II: trace element content in living and dead biomonitors and comparison with synthetic materials

Lobes of the lichen Pseudevernia furfuracea (L.) Zopf and shoots of the moss Hypnum cupressiforme Hedw. were subjected to different treatments (water washing, oven drying, HNO3 washing, NH4-oxalate extraction) to assess the influence of vitality on accumulation efficiency, during a 6-week exposure in bags in two Italian cities, Trieste and Naples. No trend emerged between treatments, in terms of accumulation ability, for major and trace elements. Only water-washed lichens showed an increased C and N content after exposure in both cities. Element concentrations generally reached higher values in mosses than in lichens, especially for Al, Fe, and Zn (both cities), and for Cu, Mg and Na (Naples). Surface development strongly influenced accumulation capacity of the biomonitors. Quartzose and cation exchange filters revealed, on a weight basis, a poor performance. In urban environments, surface interception of atmospheric particulate seems to play a major role in accumulation, irrespective of organism vitality.     

Occurrence and fate of pesticides in four contrasting agricultural settings in the United States

Occurrence and fate of 45 pesticides and 40 pesticide degradates were investigated in four contrasting agricultural settings--in Maryland, Nebraska, California, and Washington. Primary crops included corn at all sites, soybeans in Maryland, orchards in California and Washington, and vineyards in Washington. Pesticides and pesticide degradates detected in water samples from all four areas were predominantly from two classes of herbicides--triazines and chloroacetanilides; insecticides and fungicides were not present in the shallow ground water. In most samples, pesticide degradates greatly exceeded the concentrations of parent pesticide. In samples from Nebraska, the parent pesticide atrazine [6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] was about the same concentration as the degradate, but in samples from Maryland and California atrazine concentrations were substantially smaller than its degradate. Simazine [6-chloro-N,N'-diethyl-1,3,5-triazine-2,4-diamine], the second most detected triazine, was detected in ground water from Maryland, California, and Washington. Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] rarely was detected without its degradates, and when they were detected in the same sample metolachlor always had smaller concentrations. The Root-Zone Water-Quality Model was used to examine the occurrence and fate of metolachlor at the Maryland site. Simulations accurately predicted which metolachlor degradate would be predominant in the unsaturated zone. In analyses of relations among redox indicators and pesticide variance, apparent age, concentrations of dissolved oxygen, and excess nitrogen gas (from denitrification) were important indicators of the presence and concentration of pesticides in these ground water systems.