Wind Characteristics of Mesquite Streets in the Northern Chihuahuan Desert, New Mexico, USA

Past research has shown that the most important areas for active sand movement in the northern part of the Chihuahuan Desert are mesquite-dominated desert ecosystems possessing sandy soil texture. The most active sand movement in the mesquite-dominated ecosystems has been shown to take place on elongated bare soil patches referred to as “streets”. Aerodynamic properties of mesquite streets eroded by wind should be included in explaining how mesquite streets are more emissive sand sources than surrounding desert land. To understand the effects of wind properties, we measured them at two flat mesquite sites having highly similar soil textures but very different configurations of mesquite. The differences in wind properties at the two sites were caused by differences of size, orientation, and porosity of the mesquite, along with the presence of mesquite coppice dunes (sand dunes stabilized by mesquites growing in the dune and on its surface) found only at one of the two sites. Wind direction, u_* (friction velocity), z₀ (aerodynamic roughness height) and D (zero plane displacement height) were estimated for 15-m tower and 3-m mast data. These aerodynamic data allowed us to distinguish five categories with differing potentials for sediment transport. Sediment transport for the five categories varied from unrestricted, free transport to virtually no transport caused by vegetation protection from wind forces. In addition, “steering” of winds below the level of the tops of mesquite bushes and coppice dunes allowed longer parallel wind durations and increased wind erosion for streets that aligned roughly SW–NE. U.S. Government right to retain a non-exclusive royalty-free licence in and to any copyright is acknowledged.     

Geographic patterns of non-carpeted floor dust loading in Syracuse, New York (USA) homes

Residential floor dust loading was measured on the smooth floor surface of 488 houses in Syracuse, New York, during the summers of 2003 and 2004. Using U.S. Environmental Protection Agency (EPA) wipe methods, pre-weighed Ghost Wipes, Lead Wipes, or Whatman Filters were employed to collect duplicate samples from (predominantly) kitchens. The collection efficiency of the various media was determined from multiple wipe tests and side-by-side comparisons. The results were normalized and aggregated at the census tract level to determine whether spatial patterns of dust loading could be observed. Loading was found to be log-normally distributed, with a geometric mean value of 0.311 g m⁻² (29 mg of dust per square foot of floor); 95% of the observations fell in the range of 0.042–2.330 g m⁻² (4–216 mg foot⁻²). The sampling for floor dust loading shows some bias for day of the week in which visits to the residential properties were made. After a first-order correction for this effect, results were aggregated by census tract and mapped in a geographic information system (GIS); strong spatial patterns can be identified in an inverse distance weighted mapping. The geographic patterns exhibit a strong correlation with socio-economic/demographic covariates extracted from the 2000 census summaries. Dust mass on the floors is positively correlated with renter-occupied properties and family size; it is negatively correlated with measures of household income.     

Chemical speciation and bioaccessibility of lead in surface soil and house dust,Lavrion urban area,Attiki, Hellas

In the Lavrion urban area study, Hellas, a five-step sequential extraction method was applied on samples of ‘soil’ (n = 224), affected by long-term mining and metallurgical activities, and house dust (n = 127), for the purpose of studying the potential bioaccessibility of lead and other metals to humans. In this paper, the Pb concentrations in soil and house dust samples are discussed, together with those in rocks and children’s blood. Lead is mainly associated with the carbonate, Fe–Mn oxides and residual fractions in soil and house dust. Considering the very low pH of gastric fluids (1–3), a high amount of metals, present in soil (810–152,000 mg/kg Pb) and house dust (418–18,600 mg/kg Pb), could be potentially bioaccessible. Consequently, children in the neighbourhoods with a large amount of metallurgical processing wastes have high blood-Pb concentrations (5.98–60.49 μg/100 ml; median 17.83 μg/100 ml; n = 235). It is concluded that the Lavrion urban and sub-urban environment is extremely hazardous to human health, and the Hellenic State authorities should urgently tackle this health-related hazard in order to improve the living conditions of local residents.     

Prediction of particulate air pollution from a landfill site using CFD and LIDAR techniques

Landfill sites have been the most common way of eliminating solid urban waste, as well as that of public and mining wastes. Landfill sites are a constant source of environmental pollution and wind is the most important contributing factor to air pollution, due to the erosion which it produces over the landfill site surfaces, transporting dust away from the source point. This causes serious risks for human health and general dirt in the surrounding areas of the landfill site. The result of dust air pollution produced in a landfill site is analysed through CFD3D (Computational Fluid Dynamics) by joining the LIDAR (Light Detection and Ranging) technique and Ansys CFX 10.0 software. The CFD simulations determine the wind velocity distribution on the landfill site surface and the different particle threshold friction velocities which determine the dust emission in multiphase simulations (air-particles). These simulations are validated from field data obtained in three measurement programmes for each type of landfill site surface treatment which has been studied. It was determined that the superficial landfill site treatment with the lowest air pollution is tall grass and bushes. The methodology used can be applied to the dust emission calculation in the design or evaluation of other landfill sites.     

A little movement orientated to the geomagnetic field makes a big difference in strong flows

Whilst a range of animals have been shown to respond behaviourally to components of the Earth’s magnetic field, evidence of the value of this sensory perception for small animals advected by strong flows (wind/ocean currents) is equivocal. We added geomagnetic directional swimming behaviour for North Atlantic loggerhead turtle hatchlings (Caretta caretta) into a high-resolution (1/4°) global general circulation ocean model to simulate 2,925-year-long hatchling trajectories comprising 355,875 locations. A little directional swimming (1–3 h per day) had a major impact on trajectories; simulated hatchlings travelled further south into warmer water. As a result, thermal elevation of hatchling metabolic rates was estimated to be between 63.3 and 114.5% after 220 days. We show that even small animals in strong flows can benefit from geomagnetic orientation and thus the potential implications of directional swimming for other taxa may be broad.     

Feeding behaviour of the sea cucumber <Emphasis Type="Italic">Cucumaria frondosa</Emphasis> (Echinodermata: Holothuroidea) in the laboratory and the field: relationships between tentacle insertion rate,flow speed,and ingestion

The sea cucumber, Cucumaria frondosa, is a benthic suspension feeder that captures food particles on its tentacles and then inserts them into its mouth one at a time. Previous studies have suggested that tentacle insertion rate (TIR) could be a useful indicator of food intake. The present study determined whether flow velocity affects TIR and whether TIR is a good indicator of ingestion. Video observations of sea cucumbers in Passamaquoddy Bay (45°01.70N, 66°55.74W) in August 1995 showed that TIRs increased with velocities up to 55 cm s⁻¹ and decreased steadily at flows above that up to 130 cm s⁻¹. In October 2006, laboratory flume studies were carried out on specimens collected from the same site in the previous August. Temperature and salinity (12°C and 32) in the flume were the same as in the field at the time of collection. There was high individual variation in feeding behavior at free-stream velocities of 4–40 cm s⁻¹ and TIR was independent of flow. As the number of tentacle insertions increased in the flume experiments, the amount of chloropigments in the digestive tracts of the sea cucumbers also increased. This suggests that TIR, which can be measured non-intrusively using remote video techniques, could be a good indicator of feeding behavior and ingestion in C. frondosa.     

Crop demand of manganese

The peri-urban soils of Huelva, one of the first industrial cities in Spain, are subject to severe pollution problems primarily due to past poor management of industrial wastes and effluents. In this study, soil cores were collected in seven sites potentially contaminated with toxic chemicals arising from multiple anthropogenic sources, in order to identify trace elements of concern and to assess human health risks associated with them. In most soil core samples, total concentrations of As (up to 4,390 mg kg⁻¹), Cd (up to 12.9 mg kg⁻¹), Cu (up to 3,162 mg kg⁻¹), Pb (up to 6,385 mg kg⁻¹), Sb (up to 589 mg kg⁻¹) and Zn (up to 4,874 mg kg⁻¹) were by more than one order of magnitude greater than the site-specific reference levels calculated on the basis of regional soil geochemical baselines. These chemicals are transferred from the hazardous wastes, mainly crude pyrite and roasted pyrite cinders, to the surrounding soils by acid drainage and atmospheric deposition of wind-blown dust. Locally, elevated concentrations of U (up to 96.3 mg kg⁻¹) were detected in soils affected by releases of radionuclides from phosphogypsum wastes. The results of the human health risk-based assessment for the hypothetical exposure of an industrial worker to the surface soils indicate that, in four of the seven sites monitored, cancer risk due to As (up to 4.4 × 10⁻⁵) is slightly above the target health risk limit adopted by the Spanish legislation (1 × 10⁻⁵). The cumulative non-carcinogenic hazard index ranged from 2.0 to 12.2 indicating that there is also a concern for chronic toxic effects from dermal contact with soil.     

Arsenic distribution and bioaccessibility across particle fractions in historically contaminated soils

Incidental soil ingestion is a common contaminant exposure pathway for humans, notably children. It is widely accepted that the inclusion of total soil metal concentrations greatly overestimates the risk through soil ingestion for people due to contaminant bioavailability constraints. The assumption also assumes that the contaminant distribution and the bioaccessible fraction is consistent across all particle sizes. In this study, we investigated the distribution of arsenic across five particle size fractions as well as arsenic bioaccessibility in the <250-, <100-, <10- and 2.5-μm soil particle fractions in 50 contaminated soils. The distribution of arsenic was generally uniform across the larger particle size fractions but increased markedly in the <2.5-μm soil particle fraction. The marked increase in arsenic concentration in the <2.5-μm fraction was associated with a marked increase in the iron content. Arsenic bioaccessibility, in contrast, increased with decreasing particle size. The mean arsenic bioaccessibility increased from 25 ± 16% in the <250-μm soil particle fraction to 42 ± 23% in the <10-μm soil particle fraction. These results indicate that the assumption of static arsenic bioaccessibility values across particle size fractions should be reconsidered if the ingested material is enriched with small particle fractions such as those found in household dust.     

Lead speciation in indoor dust: a case study to assess old paint contribution in a Canadian urban house

Residents in older homes may experience increased lead (Pb) exposures due to release of lead from interior paints manufactured in past decades, especially pre-1960s. The objective of the study was to determine the speciation of Pb in settled dust from an urban home built during WWII. X-ray absorption near-edge structure (XANES) and micro-X-ray diffraction (XRD) analyses were performed on samples of paint (380–2,920 mg Pb kg⁻¹) and dust (200–1,000 mg Pb kg⁻¹) collected prior to renovation. All dust samples exhibited a Pb XANES signature similar to that of Pb found in paint. Bulk XANES and micro-XRD identified Pb species commonly found as white paint pigments (Pb oxide, Pb sulfate, and Pb carbonate) as well as rutile, a titanium-based pigment, in the <150 μm house dust samples. In the dust fraction <36 μm, half of the Pb was associated with the Fe-oxyhydroxides, suggesting additional contribution of outdoor sources to Pb in the finer dust. These results confirm that old paints still contribute to Pb in the settled dust for this 65-year-old home. The Pb speciation also provided a clearer understanding of the Pb bioaccessibility: Pb carbonate > Pb oxide > Pb sulfate. This study underscores the importance of taking precautions to minimize exposures to Pb in house dust, especially in homes where old paint is exposed due to renovations or deterioration of painted surfaces.     

Distribution patterns of lead in urban soil and dust in Shenyang city, Northeast China

We investigated the spatial distribution of Pb in soil and dust samples collected from 54 sites in Shenyang city, Liaoning province, Northeast China. Soil background Pb concentration was 22 mg kg⁻¹ and control values from non-industrial areas were 33 mg kg⁻¹ for soil and 38 mg kg⁻¹ for dust. Soil Pb concentrations varied widely, ranging from 26 to 2911 mg kg⁻¹, with a mean concentration of 200 mg kg⁻¹, 9 times the background value and 6 times the control value. There was great variation in soil Pb, with a coefficient of variation (CV) of 1.06 and a standard deviation (SD) of 212 mg kg⁻¹. Dust Pb concentrations fluctuated from 20 to 2810 mg kg⁻¹, with a mean value of 220 mg kg⁻¹, almost 6 times the control value. No significant differences in distribution were observed between soil Pb and dust Pb. The highest Pb concentration was observed in Tiexi district in an industrial area. Soil Pb concentration decreased with depth and with distance from the pollution source. Lead concentrations initially changed little but then decreased with distance from the roadside, and were generally higher on the east side of roads than on the west. Lead contents in different categories of urban area differed substantially with dust and soil Pb concentrations decreasing in the sequence: industrial >business >mixed (residential, culture and education)> reference areas.     

Risk remaining from fine particle contaminants after vacuum cleaning of hard floor surfaces

In the indoor environment, settled surface dust often functions as a reservoir of hazardous particulate contaminants. In many circumstances, a major contributing source to the dust pool is exterior soil. Young children are particularly susceptible to exposure to both outdoor derived soil and indoor derived dust present in the indoor dust pool. This is because early in life the exploratory activities of the infant are dominated by touching and mouthing behavior. Inadvertent exposure to dust through mouth contact and hand-to-mouth activity is an inevitable consequence of infant development. Clean-up of indoor dust is, in many circumstances, critically important in efforts to minimize pediatric exposure. In this study, we examine the efficiency of vacuum cleaner removal of footwear-deposited soil on vinyl floor tiles. The study utilized a 5 × 10 foot (c. 152.5 × 305 cm) test surface composed of 1-foot-square (c. 30.5 × 30.5 cm) vinyl floor tiles. A composite test soil with moderately elevated levels of certain elements (e.g., Pb) was repeatedly introduced onto the floor surface by footwear track-on. The deposited soil was subsequently periodically removed from randomly selected tiles using a domestic vacuum cleaner. The mass and loading of soil elements on the tiles following vacuuming were determined both by wet wipe collection and by subsequent chemical analysis. It was found that vacuum cleaner removal eliminated much of the soil mass from the floor tiles. However, a small percentage of the mass was not removed and a portion of this residual mass could be picked up by moistened hand-lifts. Furthermore, although the post-vacuuming tile soil mass was sizably reduced, for some elements (notably Pb) the concentration in the residual soil was increased. We interpret this increased metal concentration to be a particle size effect with smaller particles (with a proportionately higher metal content) remaining in situ after vacuuming.     

On the heating environment in street canyon

This study investigates the impact of building aspect ratio (building-height-to-street-canyon-width-ratio), wind speed and surface and air-temperature difference (Δθ_s−a) on the heating environment within street canyon. The Reynolds-averaged Navier-Stokes (RANS) and energy transport equations were solved with Renormalization group (RNG) theory version of k-e{\varepsilon} turbulence model. The validation process demonstrated that the model could be trusted for simulating air-temperature and velocity trends. The temperature and velocity patterns were discussed in idealized street canyons of different aspect ratios (0.5–2.0) with varying ambient wind speeds (0.5–1.5 m/s) and Δθ_s−a (2–8 K). Results show that air-temperatures are directly proportional to bulk Richardson number (R _b ) for all but ground heating situation. Conversely, air-temperatures increase significantly across the street canyon with a decrease in ambient wind speed; however, the impact of Δθ_s−a was negligible. Clearly, ambient wind speed decreases significantly as it passes over higher AR street canyons. Notably, air-temperatures were the highest when the windward wall was heated and the least during ground heating. Conversely, air-temperatures were lower along the windward side but higher within the street canyon when the windward wall was heated.     

Settlement of <Emphasis Type="Italic">Macoma balthica</Emphasis> larvae in response to benthic diatom films

The role of multi-species benthic diatom films (BDF) in the settlement of late pediveliger larvae of the bivalve Macoma balthica was investigated in still-water bioassays and multiple choice flume experiments. Axenic diatom cultures that were isolated from a tidal mudflat inhabited by M. balthica were selected to develop BDF sediment treatments characterized by a different community structure, biomass, and amount of extracellular polymeric substances (EPS). Control sediments had no added diatoms. Although all larvae settled and initiated burrowing within the first minute after their addition in still water, regardless of treatment, only 48–52% had completely penetrated the high diatom biomass treatments after 5 min, while on average 80 and 69% of the larvae had settled and burrowed into the control sediments and BDF with a low diatom biomass (<3.5 μg Chl a g⁻¹ dry sediment), respectively. The percentage of larvae settling and burrowing into the sediment was negatively correlated with the concentration of Chl a and EPS of the BDF. This suggests higher physical resistance to bivalve penetration by the BDF with higher diatom biomass and more associated sugar and protein compounds. The larval settlement rate in annular flume experiments at flow velocities of 5 and 15 cm s⁻¹ was distinctly lower compared to the still-water assays. Only 4.6–5.8% of the larvae were recovered from BDF and control sediments after 3 h. Nonetheless, a clear settlement preference was observed for BDF in the flume experiments; i.e., larvae settled significantly more in BDF compared to control sediments irrespective of flow speed. Comparison with the settlement of polystyrene mimics and freeze-killed larvae led to the conclusion that active selection, active secondary dispersal and, at low flow velocities (5 cm s⁻¹), passive adhesion to the sediment are important mechanisms determining the settlement of M. balthica larvae in estuarine biofilms.     

Cadmium-hazard mapping using a general linear regression model (Irr-Cad) for rapid risk assessment

Research undertaken over the last 40 years has identified the irrefutable relationship between the long-term consumption of cadmium (Cd)-contaminated rice and human Cd disease. In order to protect public health and livelihood security, the ability to accurately and rapidly determine spatial Cd contamination is of high priority. During 2001–2004, a General Linear Regression Model Irr-Cad was developed to predict the spatial distribution of soil Cd in a Cd/Zn co-contaminated cascading irrigated rice-based system in Mae Sot District, Tak Province, Thailand (Longitude E 98°59′–E 98°63′ and Latitude N 16°67′–16°66′). The results indicate that Irr-Cad accounted for 98% of the variance in mean Field Order total soil Cd. Preliminary validation indicated that Irr-Cad ‘predicted’ mean Field Order total soil Cd, was significantly (p < 0.001) correlated (R ² = 0.92) with ‘observed’ mean Field Order total soil Cd values. Field Order is determined by a given field's proximity to primary outlets from in-field irrigation channels and subsequent inter-field irrigation flows. This in turn determines Field Order in Irrigation Sequence (Field Order^IS). Mean Field Order total soil Cd represents the mean total soil Cd (aqua regia-digested) for a given Field Order^IS. In 2004–2005, Irr-Cad was utilized to evaluate the spatial distribution of total soil Cd in a ‘high-risk’ area of Mae Sot District. Secondary validation on six randomly selected field groups verified that Irr-Cad predicted mean Field Order total soil Cd and was significantly (p < 0.001) correlated with the observed mean Field Order total soil Cd with R ² values ranging from 0.89 to 0.97. The practical applicability of Irr-Cad is in its minimal input requirements, namely the classification of fields in terms of Field Order^IS, strategic sampling of all primary fields and laboratory based determination of total soil Cd (T-Cd_P) and the use of a weighed coefficient for Cd (Coeff_W). The use of primary fields as the basis for Irr-Cad is also an important practical consideration due to their inherent ease of identification and vital role in the classification of fields in terms of Field Order^IS. The inclusion of mean field order soil pH (1:5_water) to the Irr-Cad model accounted for over 79% of the variation in mean Field Order bio-available (DTPA (diethylenetriaminepentaacetic acid)-extractable) soil Cd. Rice is the staple food of countries of the Greater Mekong Sub-region (includes Vietnam, Myanmar, Lao PDR, Thailand and Yunnan Province, China). These countries also have actively and historically mined Zn, Pb, and Cu deposits where Cd is likely to be a potential hazard if un-controlled discharge/runoff enters areas of rice cultivation. As such, it is envisaged that the Irr-Cad model could be applied for Cd hazard assessment and effectively form the basis of intervention options and policy decisions to protect public health, livelihoods, and export security.     

Soil arsenic surveys of New Orleans: localized hazards in children’s play areas

Arsenic (As) ranks first on the 2005 and 2007 hazardous substances priority lists compiled for the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). This study describes two New Orleans soil As surveys: (1) a survey of composite soil samples from 286 census tracts and (2) a field survey of soil As at 38 play areas associated with the presence of chromated-copper-arsenate (CCA)-treated wood on residential and public properties. The survey of metropolitan New Orleans soils revealed a median As content of 1.5 mg/kg (range <0.2–16.4) and no distinctive differences between the soils of the city core and outlying areas. Play area accessible soils associated with CCA-treated wood (N = 32) had a median As of 57 mg/kg and 78% of the samples were ≥12 mg/kg, the Louisiana soil As standard. The field survey of play areas for CCA-treated wood (N = 132 samples at 38 sites) was conducted with a portable energy-dispersive X-ray fluorescence (XRF) analyzer. Seventy-five of 132 wood samples (56.8%) were deemed CCA-treated wood. Of the 38 play areas surveyed, 14 (36.8%) had CCA-treated wood. A significant association (Fisher’s exact p-value = 0.348 × 10⁻⁶) was found between CCA-treated wood and soil As (N = 75). At one elementary school CCA-treated woodchips (As range 813–1,654 mg As/kg) covered the playgrounds. The situation in New Orleans probably exists in play areas across the nation. These findings support a precautionary program for testing soils and wood for hazardous substances at all play areas intended for children.     

Energy dissipation, flow resistance and gas-liquid interfacial area in skimming flows on moderate-slope stepped spillways

With the re-evaluation and revision of a number of design floods, several embankment overtopping protection systems have been developed and a common technique is the construction of a stepped spillway on the downstream slope. For such moderate slope stepped channels, detailed air–water flow measurements were performed in a large facility with a focus on the rate of energy dissipation, flow resistance, air–water interfacial areas and re-aeration rates. Past and present experimental results showed a significant aeration of the flow. The median dimensionless residual head was about 3 × d_c for the 21.8° sloping chute and smaller than that for flatter slopes (θ = 3.4° and 15.9°). The flow resistance results yielded an equivalent Darcy friction factor of about 0.25 implying a larger flow resistance for the 21.8° slope angle than for smaller slope angles. The re-aeration rate was deduced from the integration of the mass transfer equation using measured air–water interfacial areas and air–water flow velocities. The results suggested an increasing re-aeration rate with increasing rate of energy dissipation. The stepped invert contributed to intense turbulence production, free-surface aeration and large interfacial areas. The experimental data showed however some distinctive seesaw pattern in the longitudinal distribution of air–water flow properties with a wave length of about two step cavities. While these may be caused by the interactions between successive adjacent step cavities and their interference with the free-surface, the existence of such “instabilities” implies that the traditional concept of normal flow might not exist in skimming flows above moderate-slope stepped spillways.     

Evaluation of the QUIC-URB fast response urban wind model for a cubical building array and wide building street canyon

This paper describes the QUIC-URB fast response urban wind modeling tool and evaluates it against wind tunnel data for a 7 × 11 cubical building array and wide building street canyon. QUIC-URB is based on the Röckle diagnostic wind modeling strategy that rapidly produces spatially resolved wind fields in urban areas and can be used to drive urban dispersion models. Röckle-type models do not solve transport equations for momentum or energy; rather, they rely heavily on empirical parameterizations and mass conservation. In the model-experiment comparisons, we test two empirical building flow parameterizations within the QUIC-URB model: our implementation of the standard Röckle (SR) algorithms and a set of modified Röckle (MR) algorithms. The MR model attempts to build on the strengths of the SR model and introduces additional physically based, but simple parameterizations that significantly improve the results in most regions of the flow for both test cases. The MR model produces vortices in front of buildings, on rooftops and within street canyons that have velocities that compare much more favorably to the experimental results. We expect that these improvements in the wind field will result in improved dispersion calculations in built environments.     

Quantification and fractionation of mercury in soils from the Chatian mercury mining deposit,southwestern China

Contents of total Hg and Hg fraction, organic matter, pH, grain size and chemical composition were measured to investigate the pollution characteristics and binding behavior of Hg in soils collected from the Chatian Hg mining deposit (CMD), southwestern China. The average concentration of Hg concentration in the CMD soils was 155 and 1,315 times higher than that in control soils and Chinese soils, respectively, suggesting that the CMD soils were heavily contaminated by the element. The finding was confirmed by Müller geoaccumulation index assessment with 75% very seriously polluted, 6.25% highly to very highly polluted and 18.75% moderately to highly polluted. Hg sources in the region were natural and anthropogenic: in addition to the pedogenic process and original geochemical situation, human mining–refining activities have also seriously impacted the redistribution of Hg in soils, especially in paddy soils. Based on the BCR protocol, soil Hg was divided into exchangeable (EXC), amorphous Fe–Mn oxides (AFe–MnOX), organic-crystalline iron oxides (OM-CFe) and residual (RES) fraction. The average percentage of the four fractions in the CMD followed the trend: RES (85.77%) > OM-CFe (12.44%) > AFe–MnOX (0.93%) ≥ EXC (0.86%), suggesting that the majority proportion of soil Hg in the study area remained of residual form inside the soil mineral matrix. However, their concentrations and percentages significantly varied among different locations and land use types. Soil physico-chemical parameters were key factors affecting the presence of Hg fraction. Generally, Hg fraction concentrations were positively correlated with the sand contents and soil pH values, which was presumably due to the basic anthropogenic input of Hg-containing materials and their similarity to sand in physical characteristics. However, organic matter caused adsorption–fixation and reduction–volatilization to coexist, which had opposite effects on Hg concentrations in soil, consequently exhibiting its dual nature.     

Dust exposures in tractor and combine operations in eastern Mediterranean, Turkey

The objective of this study was to determine the dust concentrations in selected tractor and combine operations in eastern Mediterranean region in Turkey Mean dust concentrations were 137.9 mg m(-3), 83.6 mg m(-3), 80.3 mg m(-3), and 88.8 mg m(-3) respectively for soil packing, furrowing, straw making, and baling on tractors with no cabins whereas 106.9 mg m(-3) was found in combines without cabins, which are much higher than the limit dust concentration (10 mg m(-3)) considered hazardous for workers' health. In tractor operations with field-installed cabins, mean dust concentrations were 5.6 mg m(-3), 6.6 mg m(-3), 6.4 mg m(-3), and 3.7 mg m(-3), respectively in soil packing, furrowing, straw making, and baling while 4.7 mg m(-3) was measured in combines with field-installed cabins. Considering unit-manufactured cabins, mean dust concentrations were 1.1 mg m(-3), 1.6 mg m(-3), 3.2 mg m(-3), and 1.4 mg m(-3) respectively in tractor operations, and 1.4 mg mr(-3) in combine operations. Variance analyses showed that not only the respiration environment of the workers but also the field operation had a significant effect on measured dust concentrations (p < 0.01). Pearson correlation coefficient was 0.74 (very strong level) between dust concentration and wind speed in soil packing, 0.46 (medium level) between dust concentration and wind speed in baling, and 0.44 (medium level) between dust concentration and ground speed in combining.