Influence of a 1,800 MHz electromagnetic field on the EEG energy

The present study investigated the influence of electromagnetic fields (EMF), similar to that emitted by mobile phones, on brain activity. Ten women and ten men, matched for age and educational level, performed a short memory task (Wechsler test), with simultaneous Electroencephalogram (EEG) recordings at 15 scalp electrodes, both without (baseline) and with exposure to an 1,800 MHz signal. The EEG energy was found concentrated at the four basic EEG bands [α (8–13 Hz), β (14–30 Hz), δ (0–4 Hz), and θ (5–7 Hz)]. The analysis revealed that in the presence of EMF, the energy of the β band was significantly greater for females than for males at the majority of the electrodes. Since beta oscillation is associated with the shift of attention during the perception, these findings may indicate that the particular EMF (1,800 MHz signal) exerts an influence on this brain activity, which appears to be gender-related.     

The frequency-dependent effect of extremely low-frequency electromagnetic field and mechanical vibration at infrasound frequency on the growth, division and motility of Escherichia coli K-12

The aim of this work was to investigate the frequency-dependent effects of extremely low-frequency electromagnetic field (ELF-EMF) and mechanical vibration at infrasound frequency (MV at IS frequency or MV) on growth and development of Escherichia coli K-12, by using classical microbiological (counting colony forming units), isotopic, spectrophotometric and electronmicroscopic methods. The frequency-dependent effects of MV and ELF-EMF were shown that they could either stimulate or inhibit the growth and the division of microbes depending on the periods following exposure. However, the mechanism through which the MV and ELF-EMF effects affect the bacteria cell is not clear yet. It was suggested that the aqua medium could serve a target through which the biological effect of MV and ELF-EMF on microbes could be realized. To check this hypothesis, the frequency-dependent effects (2, 4, 6, 8, 10 Hz) of both MV and ELF-EMF on the bacterial growth, division and their motility in cases of exposure, the preliminary treated microbes-free medium and microbes containing medium were studied. Both MV and ELF-EMF effect on microbes have frequency and post-exposure period duration-dependent characters. The [ ³ H]-thymidine involving experiments shown that EMF at 4 Hz exposure has pronounced stimulation effect on cell proliferation while 4 Hz MV has inhibition effect. But at 8–10 Hz, the both EMF and MV have inhibitory effects on cell proliferation. It is suggested that 4 and 8 Hz EMF have different biological effects on microbes.     

Influence of the Interaction of a 900 MHz Signal with Gender on EEG Energy: Experimental Study on the Influence of 900 MHz Radiation on EEG

Summary The effects of electromagnetic fields (EMF) emitted by cellular phones on human electroencephalogram (EEG) were studied during an auditory memory task. The experimental method and the experimental setup are introduced as a credible measurement method of EEG. 19 normal subjects (10 women and 9 men) performed the memory task both with and without exposure to a 900 MHz signal, emitted by a dipole antenna placed near the subjects' head. The energy of the EEG signals was calculated at the time domain. A Fourier transform of the EEG signals was done and the EEG energy was also calculated at the frequency domain. As the Parseval's theorem anticipates the energies were identical. The EEG energy was found concentrated at the four basic bands (α (8–13 Hz), β(14–30 Hz), δ (0–4 Hz) and θ(5–7 Hz)). The primary concern of the present study was the gender related influence of EMF on the spectral energy of EEG. The results show evidence of a strong gender—radiation interaction effect on the EEG energy and on the peak amplitudes within each of the four rhythms. Without radiation the spectral power of males is greater than of females, while under exposure the situation is reversed. Under the influence of EMF the spectral power of the males EEG is decreased while that of the females is increased. In conclusion both the baseline EEG and the changes effected to the EEG power spectrum under the influence of EMF seem to be gender dependent.     

Subcutaneous Arteriolar Vasomotion Changes During and After ELF-EMF Exposure in Mice in Vivo

Summary Biological effects of extremely low-frequency electromagnetic fields (ELF-EMF) on microcirculation were investigated in vivo by monitoring arteriole diameters in conscious mice. Measurements of blood vessel diameter were monitored 33 min non-stop before during and after exposure with ELF-EMF and every 389 ms blood vessel diameter were calculated. Using a dorsal skinfold chamber (DSC), and following caudal vein injection of FITC-dextran 250 kDa, the microvasculature (initial arteriole diameter of 45–80 μm), was examined by intravital microscopy and video images were recorded for a total time of 33 min. Arteriole diameter was continuously measured by on-line analysis using a High-speed Digital Machine Vision System CV-2100, using an edge-gap detection algorithm. Since vessel diameters exhibit rhythmic variation expressed by vasomotion, for estimation of microcirculatory activity we used both raw data for frequency analysis of vasomotion (measured frequencies of vasomotion were in the range 0.008÷0.1 Hz) and evaluate mean blood vessel diameter for each 1 min period of time, and make a comparison between Pre, Exposure/Sham exposure and Post exposure periods, with the aim to evaluate possible changes in mean blood vessel diameter as a result of ELF-EMF action. During EMF exposure and post-exposure periods, arteriole diameters increased significantly compared with the pre-exposure period, and the changes were larger during post-exposure. In contrast to sham exposure, vasodilatation of the microvasculature was significantly greater during exposure and post-exposure to 16 Hz EMF. These findings suggest that ELF-EMF may have potential therapeutic use benefit for treating vascular disorders.     

Magnetically treated water at 4?Hz and 2.5?mT as a modulator of cisplatin effect on cell hydration and ouabain binding of sarcoma-180 tissue

There are many data about the extremely low-frequency electromagnetic fields (ELF-EMF) therapeutic use, especially in the field of oncology. Recent data suggest that 4 Hz EMF having dehydration effect on tissues has a pronounced antitumor activity on sarcoma-180 in mice. It was shown that 4 Hz EMF have pronounced effects on physicochemical properties of water and water solution. Therefore, the aim of the present work was the comparative study of the modulation effect of ELF-EMF on cisplatin-induced changes cell hydration and number of ouabain receptors in membrane of sarcoma-180 tumor tissues. Tissue hydration was measured as wet weight/dry weight and expressed as a water content of g/g in dry weight. The number of ³H-ouabain receptors in membrane was counted by isotope scintillation counter. In conclusion, ELF-EMF can be a possible tool for stimulation of cisPt antitumor effect.     

Preliminary studies about effects of ELF and TAMMEF electromagnetic fields on human lymphomonocytes

In our paper we studied the effects of exposure to ELF (extremely low frequency) or musically generated TAMMEF (therapeutic application of musically modulated electromagnetic fields) electromagnetic fields on the tumor necrosis factor alpha (TNF-α) release induced by a lipopolysaccharide (LPS) from cultured human lymphomonocytes of peripheral blood. Lymphomonocytes, isolated from blood donors buffy-coat, were prepared using standard techniques in cell culture flasks, kept in CO₂ incubator, with controlled temperature and humidity for 5 days. Flasks were subjected to an ELF electromagnetic field (100 Hz sinusoidal) or to TAMMEF electromagnetic fields (with intensity, frequency, and wave shape randomly modified in time, so that all possible codes can occur during a single application). The TNF-α release was determined by ELISA test every 24 h for 92 h and the results were evaluated by a non-parametric test. LPS induces a stronger TNF-α release in cultures that were subjected to ELF when compared with cultures subjected to TAMMEF, at each time period of the experimental protocol. These results seem to indicate that TAMMEF is able to induce a complex modulation of LPS-induced TNF-α release, a cytokine with pro inflammatory property whose release during chronic or neoplastic inflammatory diseases has strong negative effects on several organ systems.     

Effect of modulated microwave radiation on human EEG asymmetry

This study is aimed to investigation of the effect of modulated 450 MHz microwave radiation on the EEG inter-hemispheric asymmetry. Ten cycles of the microwave exposure (1 min off and 1 min on) at fixed modulation frequency were applied on two groups of healthy volunteers. The first group of 13 subjects was exposed to microwave radiation modulated at 14 Hz and the second group of 15 subjects at 40 Hz frequency. The peak specific absorption rate (SAR) average over 1 g was 0.303 W/kg. Differences in SAR between hemispheres were up to 20 dB. Rod antenna was located from the left side of the head. Differences of relative changes in EEG energy between symmetric channels FP1–FP2, T3–T4, P3–P4 and O1–O2 in exposed and sham conditions were analysed. The results showed increase in EEG energy from the left side caused by microwave exposure. Statistical analysis done for the whole group of subjects didn’t reveal significant differences in inter-hemispheres asymmetry between exposed and sham conditions. However, statistical analysis performed for individual subjects detected significant differences in asymmetry caused by exposure for 15–35% of individuals.     

Occupational noise exposure and hearing loss among pulse processing workers

Occupational noise exposure and noise-induced hearing loss (NIHL) has been recognised as a problem among workers in Indian industries. The major industries in India are based on the processing of agricultural products. There are appreciable numbers of pulse processing units spread throughout the country. The purpose of this study was to determine the prevalence of hearing loss among pulse processing workers. As a part of hearing protection intervention, audiometric tests were conducted at the binaural low (250–1,500 Hz), the binaural mid (1,500–4,000 Hz) and the binaural high (3,000–8,000 Hz) frequency averages. The prevalence of hearing loss was determined based on hearing threshold levels (HTLs) with a low fence of 25 dB. Over 50% of pulse processing workers (dana bazaar and dal mill) showed hearing loss in the noise-sensitive higher (binaural mid and high) frequencies. The rate of hearing loss was particularly high among workers in the dal mill. The analyses show a higher risk of prevalence of hearing loss among the dal mill workers compared to the workers associated with the grain preprocessing activities. The study shows alarming signals of NIHL, especially in the dal mill workers. The occupational exposure to noise could be minimised by efficient control measures through engineering controls, administrative controls and the use of personal protective devices. Applications of engineering and/or administrative controls are frequently not feasible in developing countries for technical and financial reasons. A complete hearing conservation programme, including training, audiometry and the use of hearing protection devices, is the most feasible method for the protection of industrial workers from prevailing noise in workplace environments in the developing countries.     

Age dependency of high-affinity ouabain receptors and their magnetosensitivity

Age dependency of [³H]-ouabain binding, ⁴⁵Ca²⁺ eflux and its magnetosensitivity in rats’ brain cortex and heart muscle tissues were studied. Curves of dose-dependent [³H]-ouabain binding consisted of three components with different affinities (10⁻⁷–10⁻⁴ M (α₁); 10⁻⁹–10⁻⁷ M (α₂); and 10⁻¹¹–10⁻⁹ M (α₃)). These curves were also characterized by different dose-dependent kinetics. [³H]-ouabain binding with α₃ receptors in brain cortex and heart muscle tissues of young and adult animals had a dose-dependent character, while that in old ones had a dose-independent character. A 0.2 T static magnetic field (SMF) exposure had modulation effect on ouabain binding with α₁, α₂ and α₃ receptors in young rats, while in adult ones, only α₃ receptors were magnetosensitive. In old animals, SMF exposure had no significant effect on ouabain binding with α₃ receptors in brain cortex, while in heart muscle, it had inhibitory effect on it. Age-dependent effect of ouabain impact on ⁴⁵Ca²⁺ efflux showed that all concentrations of ouabain lead to inhibitory effect in young animals’ brain cortex and heart muscle (with the exception of 10⁻¹⁰ and 10⁻⁶ M), while in old ones, it had activation effect as compared with data received without ouabain. SMF exposure in young animals had activation effect on ⁴⁵Ca²⁺ efflux from brain cortex and heart muscle in data without ouabain, and in old rats, ⁴⁵Ca²⁺ efflux from brain cortex was magnetic insensitive. In old animals, SMF increased ⁴⁵Ca²⁺ efflux even after extra low concentration of ouabain. It is suggested that α₃ receptors having a crucial role in the regulation of Na⁺/Ca²⁺ exchange serve as age-dependent magnetosensors of excitable cells.     

High-affinity ouabain receptors: primary membrane sensors for ionizing radiation

Although the high sensitivity of the Na/K pump in cell membrane to ionizing radiation is well known in literature, the individual role of different isoforms of pump in determination of its radio-sensitivity is not clear yet. This is the subject of the present investigation. Using isotope, electro-physiological and enzymological methods, the effect of γ-ionizing radiation on cell membrane voltage-current characteristics, acetylcholine-induced membrane current, ²²Na⁺ and ⁴⁵Ca²⁺ exchange between cells and bathing solution, Na+K⁺-ATPase activity, dose-dependent ouabain binding with cell membrane, intracellular cAMP and membrane phosphorylation in snail neurons were studied. The changes in neurons as a result of 30-min γ-radiation exposure of snails to 5.16 Ci/kg at the end of the first 30 min of post-radiation period were as follows: the increase in membrane ionic conductance reversed the ouabain sensitivity of acetylcholine-induced currents, stimulation of ²²Na⁺ and ⁴⁵Ca²⁺ uptakes, inhibition of Na/K pump, activation Na/Ca exchange in reversed mode, increase in ouabain binding with high-affinity α₃ and decrease with α₂ middle-affinity receptors, decrease in intracellular cAMP content and membrane dephosphorylation. On the basis of the obtained data, it is suggested that both α₃ and α₂ catalytic subunits of Na⁺+K⁺-ATPase serve primary membrane sensors through the activation of which the biological effect of γ-radiation on neurons is realized. The IR has activation effects on α₃-dependent Na⁺/Ca²⁺ exchange in forward and its inactivation on α₂-dependent reverse modes.     

Effect of modulated at different low frequencies microwave radiation on human EEG

This study is aimed to clarify whether effect of low-level microwave radiation on human brain differs at different modulation frequencies. Resting EEG recordings were done on different groups of healthy volunteers. The 450 MHz microwave radiation modulated at 40 and 70 Hz (15 subjects) and 217 and 1,000 Hz (19 subjects) frequencies was applied. The results of our previous study at 7, 14 and 21 Hz modulation were included into analysis. Ten cycles of the exposure (1 min off and 1 min on) at each fixed modulation frequencies were applied. The field power density at the scalp was always 0.16 mW/cm². Our results showed that microwave exposure increased the EEG energy at EEG frequencies lower or close to the modulation frequency. No effect was detected at EEG frequencies higher than the modulation frequency. Statistically significant changes were caused by exposure in the EEG alpha and beta frequency bands; no significant effect was detected in the theta band. Our results suggest that telecommunication devices with complex spectrum of modulation frequencies like mobile phone can affect all human EEG frequency bands.     

Spatial Heterogeneity of Water Quality in a Highly Degraded Tropical Freshwater Ecosystem

Awareness of environmental heterogeneity in ecosystems is critical for management and conservation. We used the Xochimilco freshwater system to describe the relationship between heterogeneity and human activities. This tropical aquatic ecosystem south of Mexico City is comprised of a network of interconnected canals and lakes that are influenced by agricultural and urban activities. Environmental heterogeneity was characterized by spatially extensive surveys within four regions of Xochimilco during rainy and dry seasons over 2 years. These surveys revealed a heterogeneous system that was shallow (1.1 m, SD = 0.4 ), warm (17°C, SD = 2.9), well oxygenated (5.0 mg l⁻¹, SD = 3), turbid (45.7 NTU SD = 26.96), and extremely nutrient-rich (NO₃–N = 15.9 mg l⁻¹, SD=13.7; NH₄–N = 2.88 mg l⁻¹, SD = 4.24; and PO₄–P =  8.3 mg l⁻¹, SD = 2.4). Most of the variables were not significantly different between years, but did differ between seasons, suggesting a dynamic system within a span of a year but with a high resilience over longer periods of time. Maps were produced using interpolations to describe distributions of all variables. There was no correlation between individual variables and land use. Consequently, we searched for relationships using all variables together by generating a combined water quality index. Significant differences in the index were apparent among the four regions. Index values also differed within individual region and individual water bodies (e.g., within canals), indicating that Xochimilco has high local heterogeneity. Using this index on a map helped to relate water quality to human activities and provides a simple and clear tool for managers and policymakers.     

Characterizing the Relative Contributions of Large Vessels to Total Ocean Noise Fields: A Case Study Using the Gerry E. Studds Stellwagen Bank National Marine Sanctuary

In 2006, we used the U.S. Coast Guard’s Automatic Identification System (AIS) to describe patterns of large commercial ship traffic within a U.S. National Marine Sanctuary located off the coast of Massachusetts. We found that 541 large commercial vessels transited the greater sanctuary 3413 times during the year. Cargo ships, tankers, and tug/tows constituted 78% of the vessels and 82% of the total transits. Cargo ships, tankers, and cruise ships predominantly used the designated Boston Traffic Separation Scheme, while tug/tow traffic was concentrated in the western and northern portions of the sanctuary. We combined AIS data with low-frequency acoustic data from an array of nine autonomous recording units analyzed for 2 months in 2006. Analysis of received sound levels (10–1000 Hz, root-mean-square pressure re 1 μPa ± SE) averaged 119.5 ± 0.3 dB at high-traffic locations. High-traffic locations experienced double the acoustic power of less trafficked locations for the majority of the time period analyzed. Average source level estimates (71–141 Hz, root-mean-square pressure re 1 μPa ± SE) for individual vessels ranged from 158 ± 2 dB (research vessel) to 186 ± 2 dB (oil tanker). Tankers were estimated to contribute 2 times more acoustic power to the region than cargo ships, and more than 100 times more than research vessels. Our results indicate that noise produced by large commercial vessels was at levels and within frequencies that warrant concern among managers regarding the ability of endangered whales to maintain acoustic contact within greater sanctuary waters. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The EMF-induced changes in aqua medium’s properties depend on background ionizing radiation, illumination and temperature

The effects of extremely low-frequency electromagnetic field (ELF EMF) and ELF-modulated millimeter waves (MMW) on physicochemical properties of physiological solution (PS) at different environmental medium were studied. The existence of frequency “windows” at 4 Hz and 8 Hz frequencies of ELF EMF and ELF-modulated MMW which have different effects on heat fusion period (HFP), hydrogen peroxide (H₂O₂) formation and oxygen (O₂) content of water solution and different dependency on temperature, background radiation (BGR) and illumination was shown. The obtained data allow us to suggest that cell bathing medium serving as a target through which the biological effects of ELF EMF and ELF-modulated MMW on cells are realized is extra sensitive to environmental factors. Therefore, the variability of experimental data on EMF biological effects, obtained in different laboratories can be explained by different environmental conditions of experiments, which very often are not considered adequately.     

Effects of Sea-Level Rise and Anthropogenic Development on Priority Bird Species Habitats in Coastal Georgia, USA

We modeled changes in area of five habitats, tidal-freshwater forest, salt marsh, maritime shrub-scrub (shrub), maritime broadleaf forest (oak) and maritime narrowleaf (pine) forest, in coastal Georgia, USA, to evaluate how simultaneous habitat loss due to predicted changes in sea level rise (SLR) and urban development will affect priority bird species of the south Atlantic coastal plain by 2100. Development rates, based on regional growth plans, were modeled at 1% and 2.5% annual urban growth, while SLR rates, based on the Intergovernmental Panel on Climate Change’s A1B mean and maximum scenarios, were modeled at 52 cm and 82 cm, respectively. SLR most greatly affected the shrub habitat with predicted losses of 35–43%. Salt marsh and tidal forest also were predicted to lose considerable area to SLR (20–45 and 23–35%, respectively), whereas oak and pine forests had lesser impact from SLR, 18–22% and 11–15%, respectively. Urban development resulted in losses of considerable pine (48–49%) and oak (53–55%) habitat with lesser loss of shrub habitat (21–24%). Under maximum SLR and urban growth, shrub habitat may lose up to 59–64% compared to as much as 62–65% pine forest and 74–75% oak forest. Conservation efforts should focus on protection of shrub habitat because of its small area relative to other terrestrial habitats and use by Painted Buntings (Passerina ciris), a Partners In Flight (PIF) extremely high priority species. Tidal forests also deserve protection because they are a likely refuge for forest species, such as Northern Parula and Acadian Flycatcher, with the decline of oak and pine forests due to urban development.     

The Influence of Nutrients and Physical Habitat in Regulating Algal Biomass in Agricultural Streams

This study examined the relative influence of nutrients (nitrogen and phosphorus) and habitat on algal biomass in five agricultural regions of the United States. Sites were selected to capture a range of nutrient conditions, with 136 sites distributed over five study areas. Samples were collected in either 2003 or 2004, and analyzed for nutrients (nitrogen and phosphorous) and algal biomass (chlorophyll a). Chlorophyll a was measured in three types of samples, fine-grained benthic material (CHL_FG), coarse-grained stable substrate as in rock or wood (CHL_CG), and water column (CHL_S). Stream and riparian habitat were characterized at each site. TP ranged from 0.004–2.69 mg/l and TN from 0.15–21.5 mg/l, with TN concentrations highest in Nebraska and Indiana streams and TP highest in Nebraska. Benthic algal biomass ranged from 0.47–615 mg/m², with higher values generally associated with coarse-grained substrate. Seston chlorophyll ranged from 0.2–73.1 μg/l, with highest concentrations in Nebraska. Regression models were developed to predict algal biomass as a function of TP and/or TN. Seven models were statistically significant, six for TP and one for TN; r ² values ranged from 0.03 to 0.44. No significant regression models could be developed for the two study areas in the Midwest. Model performance increased when stream habitat variables were incorporated, with 12 significant models and an increase in the r ² values (0.16–0.54). Water temperature and percent riparian canopy cover were the most important physical variables in the models. While models that predict algal chlorophyll a as a function of nutrients can be useful, model strength is commonly low due to the overriding influence of stream habitat. Results from our study are presented in context of a nutrient-algal biomass conceptual model.     

50 Hz alternating extremely low frequency magnetic fields affect excitability,firing and action potential shape through interaction with ionic channels in snail neurones

In spite of growing concern about the influence of magnetic fields on biological systems, the interaction between extremely low frequency magnetic field (ELF magnetic fields) and biological structures at the cellular level remains obscure. The aim of this study was to investigate if 50 Hz magnetic fields could have an effect on the neuronal excitability and firing responses. Under Current-Clamp condition, exposure to 50 Hz ELF magnetic fields at 2 mT or 0.8 mT intensities resulted in an increase in the peak amplitude of action potential and after hyperpolaization potential in a time dependent manner. Both magnetic field intensities decreased also the firing frequency and the duration of action potential. Taken together, these data suggest that 50 Hz ELF magnetic fields at 2 mT or 0.8 mT intensities may change the electrophysiological behavior of neuronal cells and underlying ion channel currents.     

Characteristic levels of heavy metals in canned sardines consumed in Nigeria

Samples of some popular brands of canned sardines in soybean oil in the Nigerian market were analyzed for levels of cadmium, lead, iron, cobalt, nickel, manganese, chromium, copper and zinc after wet digestion with acids by graphite furnace atomic absorption spectrophotometry. The mean concentrations for the metals in the different brands were as follows: cadmium 0.11–0.26 μg/g, iron 8.04–48.18 μg/g, cobalt 0.01–7.23 μg/g, nickel 0.04–3.26 μg/g, manganese 0.64–1.37 μg/g, chromium 0.01–0.10 μg/g, copper 0.10 μg/g and zinc 0.09–4.63 μg/g. Significant differences were observed in the heavy metal levels in the different brands of canned sardines except for copper and chromium. Cadmium, nickel and lead exceeded statutory safe limits.     

C and N Content in Density Fractions of Whole Soil and Soil Size Fraction Under Cacao Agroforestry Systems and Natural Forest in Bahia,Brazil

Agroforestry systems (AFSs) have an important role in capturing above and below ground soil carbon and play a dominant role in mitigation of atmospheric CO₂. Attempts has been made here to identify soil organic matter fractions in the cacao-AFSs that have different susceptibility to microbial decomposition and further represent the basis of understanding soil C dynamics. The objective of this study was to characterize the organic matter density fractions and soil size fractions in soils of two types of cacao agroforestry systems and to compare with an adjacent natural forest in Bahia, Brazil. The land-use systems studied were: (1) a 30-year-old stand of natural forest with cacao (cacao cabruca), (2) a 30-year-old stand of cacao with Erythrina glauca as shade trees (cacao + erythrina), and (3) an adjacent natural forest without cacao. Soil samples were collected from 0-10 cm depth layer in reddish-yellow Oxisols. Soil samples was separated by wet sieving into five fraction-size classes (>2000 μm, 1000–2000 μm, 250–1000 μm, 53–250 μm, and <53 μm). C and N accumulated in to the light (free- and intra-aggregate density fractions) and heavy fractions of whole soil and soil size fraction were determined. Soil size fraction obtained in cacao AFS soils consisted mainly (65 %) of mega-aggregates (>2000 μm) mixed with macroaggregates (32–34%), and microaggregates (1–1.3%). Soil organic carbon (SOC) and total N content increased with increasing soil size fraction in all land-use systems. Organic C-to-total N ratio was higher in the macroaggregate than in the microaggregate. In general, in natural forest and cacao cabruca the contribution of C and N in the light and heavy fractions was similar. However, in cacao + erythrina the heavy fraction was the most common and contributed 67% of C and 63% of N. Finding of this study shows that the majority of C and N in all three systems studied are found in macroaggregates, particularly in the 250–1000 μm size aggregate class. The heavy fraction was the most common organic matter fraction in these soils. Thus, in mature cacao AFS on highly weathered soils the main mechanisms of C stabilization could be the physical protection within macroaggregate structures thereby minimizing the impact of conversion of forest to cacao AFS.     

Diversity of Soil Nematodes in Areas Polluted with Heavy Metals and Polycyclic Aromatic Hydrocarbons (PAHs) in Lanzhou,China

This study investigated the soil nematode community structure along the Yellow River in the Lanzhou area of China, and analyzed the impact of heavy metals (Cd, Pb, Cr, Cu, and Zn) and polycyclic aromatic hydrocarbons (PAHs) on the nematode community. Soil samples from five locations (named A–E), which were chosen for soil analysis, showed significant differences in their heavy metal content (p < 0.01), as well as in the variety of nematodes (up to 41 genera) and families (up to 20) that were present. The different samples also differed significantly in the total PAH content (p < 0.05), as well as the six types of PAH present. Sites A–C showed the most severe contamination with heavy metals and PAHs; these sites had the lowest abundance of fungivores and omnivore/predators, but the proportion of bacteriovores was the highest (p < 0.05). Site E, in contrast, showed only minor pollution with heavy metals and PAHs, and it contained the highest abundance of plant parasites (p < 0.05). Several nematode ecological indicators were found to correlate with concentration of soil pollutants at all the sites tested: the maturity index (MI, in addition to plant parasites), plant parasite index (PPI), ΣMI (including all the soil nematodes), Shannon-Wiener diversity index (H′′), and Wasilewska index (WI). Disturbance to the soil environment was more severe when MI, ΣMI, and H′ values were lower. The results of the study show that the abundance and structure of the soil nematode communities in the sampling locations were strongly influenced by levels of heavy metals and PAHs in the soil. They also show that the diversity index H′ and the maturity index can be valuable tools for assessing the impact of pollutants on nematodes.