Natural Degradation Processes Research Articles

Modeling the hydrologic effects of roadside ditch networks on receiving waters

Summary Roadside drainage networks can affect deleterious changes to watershed hydrology and water quality. However, very few studies have explored these effects in agricultural settings where the potential for nonpoint source pollution and the implications of tighter hydrologic linkages between landscape and stream are more critical. In this study, we apply a GIS-based, spatially distributed hydrologic model under a variety of drainage scenarios to quantify the hydrologic effects of roadside ditches at multiple spatial scales. We also qualitatively investigate the relative impacts of ditches on phosphorus transport. Our principle findings indicate that roadside ditches: (i) substantially alter basin morphometry and natural flow pathways, (ii) increase peak and total event discharge and (iii) expedite the transport of agricultural pollutants, thereby short-circuiting natural degradation processes that would otherwise have mitigated their effects. These findings underscore how relatively fine-scale alterations to natural flow pathways can result in substantial impacts to watershed scale hydrology and water quality and may help to inform spatially-targeted water resource management decisions and future modeling efforts.

Natural Abiotic Formation of Oxalic Acid in Soils: Results from Aromatic Model Compounds and Soil Samples

Oxalic acid is the smallest dicarboxylic acid and plays an important role in soil processes (e.g., mineral weathering and metal detoxification in plants). We have first proven its abiotic formation in soils and investigated natural abiotic degradation processes based on the oxidation of soil organic matter, enhanced by Fe(3+) and H(2)O(2) as hydroxyl radical suppliers. Experiments with the model compound catechol and further hydroxylated benzenes were performed to examine a common degradation pathway and to presume a general formation mechanism of oxalic acid. Two soil samples were tested for the release of oxalic acid and the potential effects of various soil parameters on oxalic acid formation. Additionally, the soil samples were treated with different soil sterilization methods to prove the oxalic acid formation under abiotic soil conditions. Different series of model experiments were conducted to determine a range of factors including Fe(3+), H(2)O(2), reaction time, pH, and chloride concentration on oxalic acid formation. Under certain conditions, catechol is degraded up to 65.6% to oxalic acid referring to carbon. In serial experiments with two soil samples, oxalic acid was produced, and the obtained results are suggestive of an abiotic degradation process. In conclusion, Fenton-like conditions with low Fe(3+) concentrations and an excess of H(2)O(2) as well as acidic conditions were required for an optimal oxalic acid formation. The presence of chloride reduced oxalic acid formation.

Wetland-based passive treatment systems for gold ore processing effluents containing residual cyanide, metals and nitrogen species

Gold extraction operations generate a variety of wastes requiring responsible disposal in compliance with current environmental regulations. During recent decades, increased emphasis has been placed on effluent control and treatment, in order to avoid the threat to the environment posed by toxic constituents. In many modern gold mining and ore processing operations, cyanide species are of most immediate concern. Given that natural degradation processes are known to reduce the toxicity of cyanide over time, trials have been made at laboratory and field scales into the feasibility of using wetland-based passive systems as low-cost and environmentally friendly methods for long-term treatment of leachates from closed gold mine tailing disposal facilities. Laboratory experiments on discrete aerobic and anaerobic treatment units supported the development of design parameters for the construction of a field-scale passive system at a gold mine site in northern Spain. An in situ pilot-scale wetland treatment system was designed, constructed and monitored over a nine-month period. Overall, the results suggest that compost-based constructed wetlands are capable of detoxifying cyanidation effluents, removing about 21.6% of dissolved cyanide and 98% of Cu, as well as nitrite and nitrate. Wetland-based passive systems can therefore be considered as a viable technology for removal of residual concentrations of cyanide from leachates emanating from closed gold mine tailing disposal facilities.

Study of the Early Stages of Mn Intrusion in Corroded Glass by Means of Combined SR FTIR/μXRF Imaging and XANES Spectroscopy

Historical glass, especially medieval glass, can undergo weathering under the influence of time and environmental conditions. The aim of this investigation was to better understand the processes involved in this natural degradation process by studying artificially altered glass samples prepared for the use of evaluation of conservation methods. Non-durable glass sensors produced by the Fraunhöfer Institute (type M1.0) were used as a starting material for artificial alteration. These were immersed in acidic (pH = 0, 2, 4) and neutral solutions (1h - 8h). In a second stage the glass samples were immersed in a 0.5M MnCl2 solution (24h, 48h and 72h), allowing intrusion of Mn from the solution into the gel layer. The samples were characterized at different stages with reflectance FTIR spectroscopy, μXRF mapping and μXANES. All measurements were carried out at ESRF, beamline ID21. Reflectance FTIR spectroscopy measurements were performed in the 800 4000 cm-1 range. Cluster analysis of the resulting maps evidenced the rapid growth of the gel layer in strong acidic conditions. The average spectra for each cluster feature show for the original glass a strong Si-O− stretching band between 900 and 1000 cm-1, whereas the gel layer could be identified by the increasing Si-O-Si bands around 1100 and 1250 cm-1. μXRF maps were recorded at different stages of the experiment at energies around the Mn-K edge (6.539 keV) and with a step size of 2 by 2μ m. These confirm the leaching of K+ and Ca+2 from the glass and the intrusion of Mn from the solution. Mn was found throughout the entire gel layer, but with a concentration gradient peaking at the surface. XANES point measurements were recorded at various points where Mn was present. No spatial variation was found, but linear combination fitting of the spectra with various Mn reference compounds indicated that Mn2+Mn3+2 O4 is the main Mn compound in the gel layer, as was hypothesised by Watkinson et al. The standard corroded glass samples studied here can be used for the evaluation of conservation treatments in follow-up experiments.

Susceptibility of magnetic information storage to power frequency magnetic fields

The potential for loss of magnetically stored information in the presence of power frequency magnetic fields is described in terms of fundamental physical mechanisms. Three important mechanisms are identified: (1) short term erasure when external fields are high enough to be a significant fraction of the demagnetizing field, (2) long term thermal degradation when external fields exceed a magnetic field associated with the acceleration of the natural thermal degradation process to an unacceptable level, and (3) concentration of magnetic flux by recording equipment, leading to erasure, augmented thermal degradation or corruption of the recording process. Quantitative expressions are developed for evaluation of the first two mechanisms in terms of fundamental magnetic properties of the recording medium, and a 3-D finite element simulation is used to quantitatively assess the third mechanism for a modern recording head. The first two mechanisms typically require field levels much larger than ordinary power frequency fields, but the third mechanism can lead to local fields large enough to bring the prior mechanisms into play. Results are put in the context of prior published standards and descriptions.

Diffusion consistent calibrations for improved chemical imaging using nanoparticle enhanced optical sensors

A basic square root function was successfully used as a diffusion consistent calibration function that considers depletion mechanisms often occurring within optical chemical sensors. This continuous function improved image quality and simplified the calibration process. It may be a universal tool for the typical response function of reversible diffusion controlled sensing reactions. Further, we demonstrate that the gold nanoparticle interaction based ammonium fluorosensor is suitable for non-invasive high-resolution quantitative imaging of complex samples. The plasmon sensitized optical sensors were utilized as a bioanalytical tool for chemical imaging of natural degradation processes occurring in biological tissues. Analytical performance of the nanoparticle enhanced sensors confirmed superior sensitivity, reversibility, durability and overall image quality over non-doped sensing membranes. Although applied in a complex matrix of high potassium (major interferent) and very high sodium (interferent) excellent performance is achieved. The nanoparticle interaction/coextraction based sensing scheme utilized in this study is general and can be used for numerous ions, preferably combined with the diffusion consistent calibrations for superior analytical performance. A table with 44 commercially available ionophores is provided to guide potential users of this sensor configuration.

New procedure to investigate external sulphate attack on cementitious materials

Abstract In order to predict the durability of concrete structures in contact with sulphate rich environments, laboratory tests have to be sufficiently representative of the field conditions. This study is focused on the degradation of cement-based materials submitted to external sulphate attack. To be close to the natural degradation process, a new experimental procedure has been developed on the basis of two studies. The first was conducted on concrete and showed the deficiencies of common experimental programs only based on the measurement of the expansion. The second investigated the relation between the specimen size and the resistance to sulphate attack. As a result, the basic points of a representative procedure were identified. The mass and length of the specimens were monitored. The pH of the sodium sulphate solution was controlled, which allowed the assessment of leaching kinetics. This procedure was then validated by analysing, at macroscopic and microscopic scales, the influence of the water sulphate concentration on the behaviour of cementitious materials. The accelerating effect of high sulphate concentrations is due to the increase in leaching kinetics rather than the type of expansive products. Whatever the concentration, the same critical proportion of the cross section is required to generate global swelling.

Functional Reorganization of Promyelocytic Leukemia Nuclear Bodies during BK Virus Infection

BK virus (BKV) is the causative agent for polyomavirus-associated nephropathy, a severe disease found in renal transplant patients due to reactivation of a persistent BKV infection. BKV replication relies on the interactions of BKV with many nuclear components, and subnuclear structures such as promyelocytic leukemia nuclear bodies (PML-NBs) are known to play regulatory roles during a number of DNA virus infections. In this study, we investigated the relationship between PML-NBs and BKV during infection of primary human renal proximal tubule epithelial (RPTE) cells. While the levels of the major PML-NB protein components remained unchanged, BKV infection of RPTE cells resulted in dramatic alterations in both the number and the size of PML-NBs. Furthermore, two normally constitutive components of PML-NBs, Sp100 and hDaxx, became dispersed from PML-NBs. To define the viral factors responsible for this reorganization, we examined the cellular localization of the BKV large tumor antigen (TAg) and viral DNA. TAg colocalized with PML-NBs during early infection, while a number of BKV chromosomes were adjacent to PML-NBs during late infection. We demonstrated that TAg alone was not sufficient to reorganize PML-NBs and that active viral DNA replication is required. Knockdown of PML protein did not dramatically affect BKV growth in culture. BKV infection, however, was able to rescue the growth of an ICP0-null herpes simplex virus 1 mutant whose growth defect was partially due to its inability to disrupt PML-NBs. We hypothesize that the antiviral functions of PML-NBs are inactivated through reorganization during normal BKV infection.

Management of the Piankatank River, Virginia, in Support of Oyster (Crassostrea virginica,Gmelin 1791) Fishery Repletion

The Piankatank River is a trap-type estuary on the western shore of Chesapeake Bay that has been managed for seed oyster production since 1963. Market oyster production in the river is minimal. Repletion efforts include shell planting and seed removal. We describe sequential changes in population demographics and habitat in relation to repletion activities on eight Piankatank River public oyster reefs from 1998 through 2009. Two reef groups (northern and southern) may be distinguished by density (oysters/m 2 ), biomass (g dry tissue weight), and shell volume (L/m 2 ) data. Age-at-length relationships were estimated from demographic data using a quadratic model. Observed mortality rates were high, and age 3+ oysters were essentially absent. A strong recruitment signal was observed in 1999 and 2002. Between 1998 and 2009, about 30% of the live oysters in the river were harvested as seed, corresponding to ;7.5% of the total shell base in an average year. Typically, for every 5 bushels of shell planted, 1 bushel of seed was harvested (20% return). Even with shell planting (;10 L/m 2 /y), the river shell budget showed a deficit with respect to the accretion rate required to balance sea level rise and natural degradation processes. During the study period, the mean river recruit-to-stock ratio was ;4. The unusual and consistently high recruit-to-stock ratios suggest that management for modest continuous seed removal may be accomplished without shell planting. Annual stock assessment to identify low recruitment years is recommended as a method to adjust annual seed harvest quotas.

Exposure to persistent organic pollutants as potential risk factors for developing diabetes

Persistent organic pollutants (POPs), such as dioxins, polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs), which are synthetic chemicals or by-products with an intrinsic resistance to natural degradation processes, are released into the environment, resulting in the widespread dispersal and accumulation in the environment, as well as in human and ecological food chains. Due to their ubiquity in the environment and lipophilic properties, there is emerging concern over the potential risks of human exposure to POPs. Extensive growing evidence indicated that exposure to POPs might be strongly associated with increased risk of a worldwide epidemic of diabetes, especially type 2 diabetes, suggesting that POPs might play a key role in their pathogenesis. Based on summary of the related studies, this paper reviews the epidemiologic and experimental data that addresses the association between increased risk of diabetes and POP exposure, including dioxins, PCBs, OCPs, polybrominated flame retardants (PBFRs), and some environmental estrogens. The potential mechanisms whereby POPs cause diabetes were discussed, such as alterations in lipid metabolism, in glucose transport, in insulin signaling pathway, in steroid metabolism, and disruption of endocrine system, induction of tumor necrosis factor-α (TNF-α). However, with respect to diabetes, some of the evidence on POPs linked to risk of diabetes was suggestive of a direct or indirect association but was limited or inconclusive. Future research is urgently needed for determining the relative contribution of POPs to diabetes and elucidating the exact mechanisms.

Photostability and Photodegradation Pathways of Distinctive Pesticides

Transformation of pesticides in the environment is a highly complex process affected by different factors. Biological and physical-chemical factors may play a role in the degradation to variable extent. Photodecomposition might be regarded as one of the most crucial factors affecting the fate of pesticides. Therefore, our study focused on revealing specific details of the photolytic degradation of pesticides. The toxicity of the examined pesticides is well known; however, little information is available regarding their natural degradation processes. More detailed examinations are required to reveal the exact mechanism of the pesticide decomposition and the biological impacts of the degradates. Significance of this study is enhanced by the fact that decomposition of pesticides may result in the formation of toxic degradation products. The photolytic degradation of frequently applied pesticides (e.g., acetochlor, simazine, chlorpyrifos, and carbendazim) with different chemical structures was investigated. An immersible ultraviolet light source was applied to induce photodegradation. The degradation processes were followed by thin-layer chromatography and gas chromatography/mass spectrometry techniques. Electron ionization mass spectrometry was used to identify the degradation species. Detailed mechanisms of photolytic transformation were established by identification of each degradate. The photolytic degradation of pesticides of distinctive chemical character exhibited markedly different photodecomposition mechanisms. At least four degradation species were detected and identified in each case. Loss of alkyl, chloro, and hydroxyl groups as well as cleavage of alkyloxy, amide, amino-alkyl, and ester bonds might be regarded as typical decomposition patterns. Deamination and ring opening might be observed at the last stages of decomposition.

Interpretation and modelling of environmental behaviour of diverse pesticides by revealing photodecomposition mechanisms

Pesticides are commonly applied agrochemicals, however their long-term chemical behaviour and environmental fate involving degradation processes have not been studied thoroughly and extensively yet. As photolytic decomposition might be regarded as one of the key factor in determining environmental behaviour of pesticides, it is of high relevance to have comprehensive knowledge on characteristics of pesticide degradates having potential harmful biological effects. Toxicity of the examined pesticides is well known, however scarce information is available on their natural degradation processes, as well as the quality, structure and biological impact of the decomposition products. Our study is focused on revealing specific details of photolytic degradation behaviour of 3 frequently applied pesticides and mapping the entire decomposition mechanisms. Special, immerseable, low pressure mercury-vapour lamp was applied to induce photolytic transformation, which was followed by TLC and GC. The pesticides and the obtained products were identified by using GC-MS technique. The structure identifications were based on the interpretation of the fragmentation pathways. All the pesticide studied proved to be photosensitive and major stages of the UV-degradation pathway were found to be the loss of alky-groups, cleavage of the chloro-group and the hydroxylation, scission of N-alkyl groups and decarbonylation. In contrast to previous studies, different and specific degradates and end-products have been established, and the existence of alternative conversion pathways was revealed.

Potash in salt extruded at Sar Pohl diapir, Southern Iran

Recent progress in the search for potassium salts in Iran is outlined. After reviewing how most potassium ores form by the evaporation of seawater ± hydrothermal brines, we focus on how most ores are deformed within salt diapirs. We summarise the history of the 150 or so diapirs of Hormoz salt emergent in the Zagros Mountains of Iran and then consider in detail the nature of potash at Sar Pohl, 60 km west of Bandar Abbas. These deposits are unique in that they occur in salt that extruded sub-aerially and spread over the surrounding ground surface via gravity-driven collapse. Mapping and drilling of the complex structural geology of Sar Pohl found the potash beds to be dispersed in distal salt but concentrated in piles of recumbent folds with axes circumferential to the mountain over lows in the vent rim. Equivalents of the curtain folds surviving in the stems of German diapirs presumably still exist beneath Sar Pohl and would be safer to mine than the recumbent folds in this soluble mountain. However, it should be possible to continuously pump water onto the exposed salt and guide the resulting brines through evaporation ponds and then a crystallization plant on the adjacent plains. This approach would accelerate natural degradation processes but harvest potash currently draining into the gulf.

Relationships between specific ultraviolet absorbance and trihalomethane precursors of different carbon sources

A rapid and effective detection method is essential for water utilities to monitor variability of dissolved organic carbon (DOC) in source waters in order to apply strategies to minimize formation of disinfection by-products in treated waters. Ultraviolet absorbance at 254 nm (UVA254) and specific UVA254 (SUVA254) have been widely used as surrogates of concentration and reactivity of DOC, respectively. However, poor correlations between SUVA254 and specific trihalomethane formation potential (STHMFP) have been occasionally reported and the reliability of using SUVA254 to predict trihalomethane (THM) formation has been questioned. In this study, the correlations of SUVA254 and THM reactivity of three different DOC sources commonly found in water treatment facilities (aquatic carbon, soil carbon, and fecal matter) were evaluated. A 0.22 μm filter, instead of 0.45 μm filter, was used for water filtration to minimize the effects of colloidal materials on UVA254. UVA254 and DOC after chlorination were also examined and differential UVA254 and SUVA254 (ΔSUVA254) were compared to THM reactivity. Results showed correlations between UVA254 and DOC were source dependent suggesting natural humification and degradation processes did not alter DOC characteristics from its original sources. The STHMFP of river and soil DOC samples were comparable, whereas their UVA254 normalized THMFP were different ( p <0.05), suggesting that UVA254 is a better indicator in predicting THM formation potential than DOC concentrations. ΔSUVA254 showed a stronger correlation with STHMFP than the conventional surrogate—SUVA254.

Identifying optimal spectral bands to assess soil properties with VNIR radiometry in semi-arid soils

Mediterranean soils are critically endangered by natural and human induced degradation processes. Rapid and cost effective techniques for in situ diagnosis of soil properties are highly valuable for soil assessment and management studies. The combined use of remote sensing techniques and Geographic Information Systems (GIS) has introduced a new era for soil resources assessment and monitoring. This work deals with soils in SE Spain and explores the use of spectral derivative analysis to predict several soil properties using field based visible-near infrared (VNIR) spectroradiometry. Robust regression models were obtained for electric conductivity (E.C.), carbonates, soil organic matter (SOM) and sand content with the first and/or second derivative approximation. Future research stages will include evaluating the technique presented in this paper for other semi-arid soils and scaling-up field based regression model predictions for soil properties to the resolution of satellite remote sensors.

Monitoring the Onset and Propagation of Natural Degradation Process in a Slow Speed Rolling Element Bearing With Acoustic Emission

The monitoring and diagnosis of rolling element bearings with the high frequency acoustic emission (AE) technology has been ongoing since the late 1960s. This paper demonstrates the use of AE measurements to detect, locate, and monitor natural defect initiation and propagation in a conventional rolling element bearing. To facilitate the investigation a special purpose test rig was built to allow for accelerated natural degradation of a bearing race. It is concluded that subsurface initiation and subsequent crack propagation can be detected with the AE technology. The paper also presents comparative results between AE and vibration diagnosis.

Corrosion of brass archaeological blinker: Characterisation of natural degradation process

The high variety of roman activities that took place during the roman conquest of Spain during the ancient era, have allowed obtaining a high variety of glasses, ceramics and metals objects. In the present work, we show the study of the natural degradation of a roman horse eye-guard. The samples were prepared by conventional metallographic techniques and they were observed by Optical and Electronical Microscopy (OM, SEM). The different constituents were analysed using techniques of Energy Dispersive Spectrometry (EDS). These studies have allowed us to deduce which are the mechanisms that took place during the natural degradation of these roman pieces.

A pilot plant for the treatment of lemon industry wastewater

A pilot plant with a 10-m3 airlift reactor, a settler and a 300-m3 pond were developed for the treatment of the lemon processing industry wastewater. The aim of this work is to evaluate reactor and pilot plant performance. We worked in a continuous system with activated sludge, using wastewater microorganisms and testing the most important parameters of the process (HRT, SRT, F/M, VRC, K La). An outflow settler tube added to the reactor design increased sludge concentration in 25% at 200–500 l/h flow rates. At 600–800 l/h flow rates sludge concentration was 10–15% higher. Volumetric removal capacity of the suspended solid in the reactor was more than 6 kg BOD5/m3 day with lesser than 17 h hydraulic retention time. Maximum BOD5 removal was 92% with 200 l/h flow. The reactor had a good mixing performance and a satisfactory volumetric mass transfer coefficient. Efficient reactor design made foam disposal easy. The effluent came out of the pond with DBO = 50 mg/l, i.e. a total BOD removal of 99% with 600 l/h flow. The pond also had a very important function: it completely eliminated reactor produced biomass by using a natural degradation process.

GC-MS studies to map mechanistic aspects of photolytic decomposition of pesticides

Transformation of pesticides in the environment is a highly complex process affected by different factors. Both biological and physical-chemical factors may play a role in the degradation, whose ratio depends on the actual environmental conditions.Our study aims to reveal specific details of photolytic degradation of pesticides as important soil contaminants. Significance of these studies is enhanced by the fact that pesticide decomposition may contribute to soil degradation, and have harmful biological effects by degrading to toxic products. The toxicity of the examined pesticides is well known, however very little information is available regarding their natural degradation processes, the quality, structure and biological impact of the degradation products.The photolytic degradation of frequently applied pesticides of distinctive types (acetochlor – acetanilide, simazine – triazine, chlorpyrifos – organophosphate, carbendazim – benzimidazole) was investigated. A special, immerseable UV-light source was applied in order to carry out photodegradation. The degradation processes were followed by thin layer chromatography (TLC) and mass spectrometry coupled with gas chromatography (GC/MS). EI mass spectrometry was used to identify the degradation species.Each of the studied pesticides underwent photolytic decomposition, and the detailed mechanism of photolytic transformation was established. At least four degradation species were detected and identified in each case. Loss of alkyl, alkyloxy, amino-alkyl and chloro groups might be regarded as typical decomposition patterns. Deamination occurred at the last stage of decomposition.

Analysis of the 2003 Varunawat Landslide, Uttarkashi, India using Earth Observation data

Mass movements such as landslides in mountainous terrains are natural degradation processes and one of the most important landscape-building factors. Varunawat Parbat overlooking Uttarkashi town witnessed a series of landslides on 23 September 2003 and the debris slides and rock falls continued for 2 weeks. This landslide complex was triggered due to the incessant rainfall prior to the event, and its occurrence led to the blockage of the pilgrim route to Gangotri (source of the Ganges river) and evacuation of thousands of people to safer places. Though there was no loss of lives due to timely evacuation, heavy losses to the property were reported. High-resolution stereoscopic earth observation data were acquired after the incidence to study the landslide in detail with emphasis on the cause of the landslide and mode of failure. Areas along the road and below the Varunawat foothill region are mapped for landslide risk. It was found that the foothill region of the Varunawat Parbat was highly disturbed by man-made activities and houses are dangerously located below steep slopes. The potential zones for landslides along with the existing active and old landslides are mapped. These areas are critical and their treatment with priority is required in order to minimise further landslide occurrences.