Accumulation of uranium derived from long-term fertilizer applications in a cultivated Andisol

The U concentrations in the soils of experimental fields with continuous fertilizer applications and in neighboring non-agricultural soils were determined. The surface soils in the three experimental fields with fertilizer applications contained higher amounts of U compared with the non-agricultural surface soils. The amount of U elevated in the soil was estimated by the vertical profile of U concentration, and an increase of about 200 mg m-2 of U was found in the soils at 0-35 cm depth during a 61-year cultivation period. The estimated value was almost the same as the amount of U added through the fertilizers as calculated from U concentrations in the applied fertilizers. Therefore, almost all the U from the fertilizers would still remain in the upper part of the soils. Chemical extraction results suggested that organic substances and noncrystalline clay minerals in the surface soil should play an important role for accumulation of U derived from the fertilizers.     

Gradient distribution of persistent organic contaminants along northern slope of central-Himalayas, China

High mountains may serve as condenser for persistent organic pollutants (POPs) and the vegetation in remote areas has been used as a means to characterized atmospheric concentrations of air pollutants. In this study, organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in Himalayan spruce needle samples from Zhangmu-Nyalam region (central-Himalayas) were analyzed and the altitudinal gradient of these pollutants was investigated. Total HCHs and DDTs concentration in needles were in the range of 1.3-2.9 ng g(-1) dry weight and 1.7-11 ng g(-1) dry weight, which were lower than concentrations reported in spruce needles from Alps, however higher than concentrations in conifer needles from mountain areas of Alberta. Total Himalayan spruce needle PAHs was below 600 ng g(-1) and fluorene, phenanthrene and acenaphthene were abundant individual compounds measured. The ratios of alpha-HCH/gamma-HCH in pine needles were similar with the usual values for technical HCH, implying technical HCHs might be used in this region. The high ratios of o-p'-DDT/p-p'-DDT and no p-p'-DDE measured in this study led to the suspicion that a new source of o-p'-DDT and/or p-p'-DDT existed in this region. In addition, higher ratios of low molecular weight-/high molecular weight-PAHs in this region indicated that petroleum combustion, vehicle emission and low-temperature combustion might be the major contributions of PAH source. To examine the POPs distillation, the analyte concentrations were correlated with altitude. The more volatile OCPs, alpha-HCH, gamma-HCH, aldrin and alpha-endosulfan positively correlated with altitude, however, less volatile OCPs (DDT and DDD) inversely related with elevation. Almost all PAHs detected in this area showed positive correlations with altitude. It is worthy to note that heavy PAHs (Benzo[k] fluoranthene and Benzo[a]anthracene) displayed positive correlation, which implied the sources of PAHs were near the sampling sites. The distillation of POPs was strongly affected by the proximity between sampling sites and contaminant sources. If the contaminant sources are close to the mountains, it may be the dominant factor that controls the concentration gradient.     

Mercury methylation along a lake-forest transect in the Tapajós river floodplain, Brazilian Amazon: seasonal and vertical variations

The seasonal and spatial variations of net methylmercury production in sediments, soils and other sites were evaluated by assays with 203Hg at different depths and locations along a lake-forest transect at lake Enseada Grande, Tapajós river. Soil and sediment samples were taken at the surface and at different depths up to 9 cm. Fresh samples and acidified controls (1-3 g dry wt.) were slurried with local water and incubated in the dark at 25-28 degrees C for 3 days with 0.5-1.6 microg Hg g(-1) (dry wt.) added as 203HgCl2. CH3 203Hg was extracted and measured in scintillation cocktail after acid leaching. Methylmercury production varied by orders of magnitude among sites and among sediment or soil layers. Seasonal variations were smaller than those with sample depth and location. In both seasons, MeHg formation in sediment and soil or flooded soil decreased with depth and was, in the top layers, one order of magnitude higher in the C-rich littoral macrophyte zone (2.3-8.9%) and flooded forest (3.2-4.5%) than in the center of the lake (0.2-0.56%). Similar MeHg production was found in slurried dry soils (dry season) and in soils already flooded for months. In the macrophyte zone soil (dry season), methylation was mainly associated with the thin Paspalum sp. rootlet layer. In the forest site, vertical variation in methylation was less pronounced in flooded than in dry soils and during the inundation the higher methylation rate was found in the flocculent sediment settled over the litter layer. The roots of floating Paspalum sp. were an important Hg methylation site, particularly those heavily colonized with periphyton (3.4-5.4%). Methylation in surface or near-bottom water was undetectable (< 3 x 10(-2)%) at all sites. Flooded forests and macrophyte mats are specific features of the Amazon and are important links between Hg inputs from natural and manmade sources and MeHg exposure of local populations through fish intake.     

Profile storage of organic/inorganic carbon in soil: From forest to desert

Understanding the distribution of organic/inorganic carbon storage in soil profile is crucial for assessing regional, continental and global soil C stores and predicting the consequences of global change. However, little is known about the organic/inorganic carbon storages in deep soil layers at various landscapes. This study was conducted to determine the soil organic/inorganic carbon storage in soil profile of 0-3 m at 5 sites of natural landscape from forest to desert. Landscapes are temperate forest, temperate grassland, temperate shrub-grassland, temperate shrub desert, and temperate desert. Root mass density and carbon contents at the profile were determined for each site. The results showed that considerable decrease in root biomass and soil organic carbon content at the soil profile of 0-3 m when landscape varied from forest to desert along a precipitation gradient, while soil inorganic carbon content increased significantly along the precipitation gradient. Namely, for density of soil organic carbon: forest > grassland > shrub-grassland > shrub desert > desert; for density of soil inorganic carbon: forest, grassland < shrub-grassland < shrub desert < desert (P < 0.05 in all cases). In landscapes other than forest, more than 50% soil carbon storage was found in 1-3 m depth. For grassland and shrub-grassland, the contribution from 1-3 m was mainly in the form of organic carbon, while for shrub desert and desert the contribution from this depth was mainly in the form of inorganic carbon. The comparison of soil C storage between top 0-1 m and 1-3 m showed that the using top 1 m of soil profile to estimate soil carbon storages would considerably underestimate soil carbon storage. This is especially true for organic soil carbon at grassland region, and for soil inorganic carbon at desert region.     

Temporal and spatial variabilities of atmospheric polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and polycyclic aromatic hydrocarbons (PAHs) in the Canadian Arctic: results from a decade of monitoring

The Northern Contaminants Program (NCP) baseline monitoring project was established in 1992 to monitor for persistent organic pollutants (POPs) in Arctic air. Under this project, weekly samples of air were collected at four Canadian and two Russian arctic sites, namely Alert, Nunavut; Tagish, Yukon; Little Fox Lake, Yukon; Kinngait, Nunavut; Dunai Island, Russia and Amderma, Russia. Selected POPs, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides, were analyzed in both the gas and particulate phases. This paper summarizes results obtained from this project in the past 5 years. Temporal trends were developed for atmospheric PCBs and OCs observed at Alert using a digital filtration (DF) technique. It was found that trends developed with 5 years of data (1993-1997) did not differ significantly from those determined with 7 years of data (1993-1999). This implies that with the DF technique, long-term trends can still be developed with less than 10 years of data. An acceleration in decline of OC and PCB air concentrations was noted in 1999 for some compounds, although the reason is unknown. Monitoring efforts must continue to assess the effect of this decline on the long-term trends of POPs in the Canadian Arctic. Occasional high trans-/cis-chlordane ratios and heptachlor air concentrations measured at Alert between 1995 and 1997 suggests sporadic fresh usage of chlordane-based pesticides. However, significant decreasing trends of chlordanes along with their chemical signatures has provided evidence that emission of old soil residues is replacing new usage as an important source to the atmosphere. Measurements of OC air concentrations conducted at Kinngait in 1994-1995 and 2000-2001 indicated faster OC removal at this location than at Alert. This may be attributed to the proximity of Kinngait to temperate regions where both biotic and abiotic degradation rates are faster. The PAH concentrations observed at Alert mimic those at mid-latitudes and are consistent with long-range transport to the Arctic, particularly for the lighter PAHs. A decline in particulate PAH was observed, similar to atmospheric sulphate aerosol and can be attributed to the collapse of industrial activity in the former Soviet Union between 1991 and 1995. Spatial comparisons of OC seasonality at Alert, Tagish, Dunai and Kinngait show elevated air concentrations of some compounds in spring. However, elevated spring concentrations were observed for different compounds at different sites. Potential causes are discussed. Further investigation in the atmospheric flow pattern in spring which is responsible for the transport of POPs into the Arctic is required. OC and PCB air concentrations at Alert were found to be influenced by two climate variation patterns, the North Atlantic Oscillation (NAO) and the Pacific North American (PNA) pattern. Planetary atmospheric patterns must be taken into account in the global prediction and modelling of POPs in the future.     

Using soil biomass as an indicator for the biological removal of effluent-derived organic carbon during soil infiltration

This study investigates the relationship between soil biomass and organic carbon removal during the infiltration of conventionally treated effluents used for groundwater recharge during soil-aquifer treatment (SAT). Investigations were conducted on samples collected from full-scale SAT sites, revealing a positive correlation between biodegradable organic carbon (BOC) concentrations in the recharged effluents and total viable soil biomass concentrations in the infiltration zone of soil samples collected from respective recharge basins. Findings of this study suggest that BOC limits soil biomass growth and was able to support a steady-state concentration of viable soil biomass that is characteristic to BOC concentrations introduced with the recharged effluents. All investigated sites indicate that BOC is primarily removed within 30 cm soil depth leading to a significant increase in soil biomass levels (measured as substrate induced respiration (SIR), total viable biomass, and dehydrogenase activity (DHA)). Controlled biological column studies revealed that the primary components of BOC in domestic effluents are organic colloids. Findings of this study support that hydrophobic acids, commonly believed to be recalcitrant, may also be attenuated by biological processes during soil infiltration.     

Link between DOC in near surface peat and stream water in an upland catchment

Hydrologic transport of dissolved organic carbon (DOC) from peat soils may differ to organo-mineral soils in how they responded to changes in flow, because of differences in soil profile and hydrology. In well-drained organo-mineral soils, low flow is through the lower mineral layer where DOC is absorbed and high flow is through the upper organic layer where DOC is produced. DOC concentrations in streams draining organo-mineral soils typically increase with flow. In saturated peat soils, both high and low flows are through an organic layer where DOC is produced. Therefore, DOC in stream water draining peat may not increase in response to changes in flow as there is no switch in flow path between a mineral and organic layer. To verify this, we conducted a high-resolution monitoring study of soil and stream water at an upland peat catchment in northern England. Our data showed a strong positive correlation between DOC concentrations at -1 and -5 cm depth and stream water, and weaker correlations between concentrations at -20 to -50 cm depth and stream water. Although near surface organic material appears to be the key source of stream water DOC in both peat and organo-mineral soils, we observed a negative correlation between stream flow and DOC concentrations instead of a positive correlation as DOC released from organic layers during low and high flow was diluted by rainfall. The differences in DOC transport processes between peat and organo-mineral soils have different implications for our understanding of long-term changes in DOC exports. While increased rainfall may cause an increase in DOC flux from peat due to an increase in water volume, it may cause a decrease in concentrations. This response is contrary to expected changes in DOC exports from organo-mineral soils, where increase rainfall is likely to result in an increase in flux and concentration.     

Polychlorinated biphenyls (PCBs) in sediments of the southern Baltic Sea--trends and fate.

Polychlorinated biphenyls (PCBs) have been determined in recent [0-1(2), 1(2)-5 and 5-10 cm deep layers] sediments from different sites of the southern Baltic Sea, including the Szczecin Lagoon, collected from May 1996 to October 1999, i.e. before and after the great flood in Poland of July/August 1997. The PCB distribution has been correlated with location and hydrological conditions as well as with organic carbon, algal pigments and their derivatives in the sediments. The sum of PCB (seven congeners) was equal to approximately 1-149 ng/g dry wt., on average this was rather low (up to 40 ng/g). There was a decreasing trend in PCBs concentrations in the bottom sediments of the southern Baltic in 1996 but considerable amounts were still accumulated there. The flood of 1997 caused a distinct increase of PCB concentration level in the sediments, which again showed a decreasing trend in the next few years. This illustrates that at present the main source of PCBs for the southern Baltic are not a direct consequence of human activity, but from floods and heavy rains washing these compounds from land to the sea. Algae and algal detritus play an important role in the transport and distribution of PCBs in the southern Baltic. High correlation of PCBs with chlorophyll a derivatives--products of zooplankton grazing--indicates that PCBs are ingested by zooplankton with phytoplankton and then exuded with fecal pellets. PCBs bound to algal detritus or to fecal pellets in the water column are transferred to sediments, there they may be trapped either in a bonded and unchanged form or resuspended, remobilized and/or dechlorinated, depending on their properties and environmental conditions.     

Which persistent organic pollutants can we map in soil using a large spacing systematic soil monitoring design? A case study in Northern France

Persistent organic pollutants (POPs) impact upon human and animal health and the wider environment. It is important to determine where POPs are found and the spatial pattern of POP variation. The concentrations of 90 molecules which are members of four families of POPs and two families of herbicides were measured within a region of Northern France as part of the French National Soil Monitoring Network (RMQS: Réseau de Mesures de la Qualité des Sols). We also gather information on five covariates (elevation, soil organic carbon content, road density, land cover and population density) which might influence POP concentrations. The study region contains 105 RMQS observation sites arranged on a regular square grid with spacing of 16 km. The observations include hot-spots at sites of POP application, smaller concentrations where POPs have been dispersed and observations less than the limit of quantification (LOQ) where the soil has not been impacted by POPs. Fifty nine of the molecules were detected at less than 50 sites and hence the data were unsuitable for spatial analyses. We represent the variation of the remaining 31 molecules by various linear mixed models which can include fixed effects (i.e. linear relationships between the molecule concentrations and covariates) and spatially correlated random effects. The best model for each molecule is selected by the Akaike Information Criterion. For nine of the molecules, spatial correlation is evident and hence they can potentially be mapped. For four of these molecules, the spatial correlation cannot be wholly explained by fixed effects. It appears that these molecules have been transported away from their application sites and are now dispersed across the study region with the largest concentrations found in a heavily populated depression. More complicated statistical models and sampling designs are required to explain the distribution of the less dispersed molecules.     

The status of soil contamination by semivolatile organic chemicals (SVOCs) in China: a review

This paper summarizes the published scientific data on the soil contamination by semivolatile organic chemicals (SVOCs) in China. Data has been found for more than 150 organic compounds which were grouped into six classes, namely, polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs) and phthalic acid esters (PAEs). An overview of data collected from the literature is presented in this paper. The Chinese regulation and/or other maximum acceptable values for SVOCs were used for the characterization of soils. In general, the compounds that are mostly studied in Chinese soils are OCPs, PAHs and PCBs. According to the studies reviewed here, the most abundant compounds were PAEs and PAHs (up to 46 and 28 mg kg(-1) dry weight, respectively); PCBs and OCPs occurred generally at concentrations lower than 100 microg kg(-1) dry weight. Nevertheless, quite high concentrations of PCDD/Fs, PCBs and PBDEs were observed in contaminated sites (e.g., the sites affected by electronic waste activities). The average concentrations of PAHs and OCPs in soils of North China were higher than those in South China. The principal component analysis demonstrated different distribution patterns for PAH, PCB and PCDD/F congeners and for the various sites/regions examined. The isomer ratios of DDTs and hexachlorocyclohexanes (HCHs) indicated different sources and residue levels in soils. Finally, this review has highlighted several areas where further research is considered necessary.     

Urban stormwater contamination by polychlorinated biphenyls (PCBs) and its importance for urban water systems in Switzerland

Like other persistent organic pollutants (POPs), polychlorinated biphenyls (PCBs) are still present in the environment despite their almost worldwide prohibition. A study was conducted over 1 year in Switzerland to analyze the source and load of PCBs in urban stormwater and their importance in urban water systems. The mean PCB concentrations of 89 rain events were determined in five different strictly separate drainage systems (three in Lausanne and two in Geneva). The mean concentrations of PCBs in stormwater ranged from values below the detection limit (0.11-0.24 ng/l) to 403 ng/l. A model for the wet and dry deposition of PCBs based on these results estimates that their concentration in rainwater has remained practically constant (35 ng/l) over a period of 12 years. A mass balance of Swiss levels estimates a total input load of PCBs in the urban water systems at 110-125 kg/year. The contribution of stormwater is 75-94 kg/year in combined sewer systems and 23-34 kg in separate sewer systems. This mass balance illustrates that a major part of the PCB load in the environment or in WWTP sludges originates from urban stormwater. This result was confirmed by a fingerprint of PCB congeners in stormwater, which showed a pattern identical to that found in sewage sludge in combined sewer systems.     

Phthalates and nonylphenols in profiles of differently dressed soils

The concentrations of nonylphenols and phthalates in depth profiles of eight differently dressed, fertilised and cultured fields were investigated. The fields were typical for Danish agriculture and comprised an uncultured location, two manured fields, an artificially fertilised field and three fields amended with different amounts of sewage sludge. In addition, a location receiving run-off from a sewage sludge storage facility were investigated. At each location, two 50 cm vertical soil cores were taken, divided into sections of 10 cm each and analysed for nonylphenols and phthalates by high-resolution mass spectrometry. Di-(2-ethylhexyl)-phthalate (DEHP) was the most abundant phthalate in all samples whereas Di-(n-butyl)-phthalate (DBP) played a minor role. Nonylphenols occurred in significant concentrations only in soil samples exposed to high amounts of sludge and at the run-off location. A close relationship was found between the concentrations of contaminants in the soil samples and the method of dressing. The concentrations were low at comparable levels in the soil samples from the artificially fertilised field and in the fields amended with low amounts of sludge, as well as in the manured fields. Remarkably, these concentrations did not differ significantly from the level in an uncultured recreational preserved area, which was used as a reference. In contrast, much higher levels of contaminants were found in the soil samples from fields exposed to high amounts of sludge. We must conclude that sludge amendment below a certain limit does not lead to elevated levels of nonylphenols and phthalates in the soils, whereas heavy sludge amendment leads to the accumulation of these contaminants. For the vertical distribution of substances in the soils, an influence of soil characteristics on the concentration profile was noted. Thus, in soils with visible clay in the upper layers, a DEHP maximum occurred at a depth of 10-20 cm, whereas in most sandy soils no such maximum was observed. A 2-year time trend study of the highly sludge amended soil showed no measurable reduction in the substances during this period. The time study further suggested a downward movement of the DEHP maximum of approximately 10 cm per year.     

Degradation of C2-C15 volatile organic compounds in a landfill cover soil

The composition of non-methane volatile organic compounds (hereafter VOCs) in i) the cover soil, at depths of 30, 50 and 70 cm, and ii) gas recovery wells from Case Passerini landfill site, (Florence, Italy) was determined by GC-MS. The study, based on the analysis of interstitial gases sampled along vertical profiles within the cover soil, was aimed to investigate the VOC behaviour as biogas transits from a reducing to a relatively more oxidizing environment. A total of 48 and 63 different VOCs were identified in the soil and well gases, respectively. Aromatics represent the dominant group (71.5% of total VOC) in soil gases, followed by alkanes (6.8%), ketones (5.7%), organic acids (5.2%), aldehydes (3.0%), esters (2.6%), halogenated compounds (2.1%) and terpenes (1.3%). Cyclics, heterocyclics, S-bearing compounds and phenols are ≤ 1%. In the wells the VOC composition is characterized by higher concentrations of cyclic (7.6%) and S-bearing compounds (2%) and lower concentrations of O-bearing compounds. The vertical distribution of VOCs in the cover soil shows significant variations: alkanes, aromatics and cyclics decrease at decreasing depth, whereas an inverse trend is displayed by the O-bearing species. Total VOC and CH₄ concentrations at a depth of 30 cm in the soil are comparable, inferring that microbial activity is likely affecting VOCs at a very minor extent with respect to CH₄. According to these considerations, to assess the biogas emission impact, usually carried out on the sole basis of CO₂ and CH₄ emission rates, the physical-chemical behaviour of VOCs in the cover soil, regulating the discharge of these highly contaminant compounds in ambient air, has to be taken into account. The soil vertical distribution of these species can be used to better evaluate the efficiency of oxidative capability of intermediate and final covers.     

Effects of forest cover and topographic factors on TOC and associated metals at various scales in western Scotland

Studies at the stream catchment scale have yielded inconclusive evidence of the effects of forest land use on the concentrations of organic carbon in drainage waters. The aim of this paper is to examine the effects of forests on carbon in drainage waters at the plot scale by comparing concentrations of total organic carbon (TOC) and associated metals in soil solutions from sites under forest and moorland vegetation. At an upland site in south-west Scotland soil solution TOC, aluminium and iron concentrations varied with land cover. Mean concentrations of all three determinands were at least 1.5 times greater under forest than under moorland, despite considerable spatial and temporal (seasonal) variability. TOC in soil solutions was also found to vary significantly with both relief and altitude. The altitude effect was particularly marked, with an increase of 26 mg x l(-1) x 100 m(-1) increase in altitude found at an upland site in west-central Scotland. There were no differences in chloride, sulphate or base cation concentrations between forest and moorland sites. Differences in aluminium concentrations could not be linked to atmospheric scavenging at the forest sites, but were closely linked to differences in TOC.     

Assessing the transfer of pentachlorophenol through soil columns using 13[C]isotope

The transfer of organic pollutants was studied through soil columns using 13[C]-labelled pentachlorophenol (PCP) as a model compound. The organic carbon content and the 13[C]/12[C] ratio were measured in two soil sections, 0-3 cm and 3-6 cm, and in percolated water using an Elemental Analyser coupled with a Magnetic Mass Sector. The mass balance of carbon was evaluated and the amount of PCP was calculated in each compartment of the soil-water systems. The results show that more than 80% of the PCP-derived 13[C] remained in the upper layer of the soil column. Approximately 20% was transferred to the lower soil layer, and less than 1% was found in the water leachates. The 13[C]-labelled tracers may thus be used as an alternative to radioactive compounds to follow the fate of organic pollutants in soil and water under field conditions.     

Viral transport through soil columns under conditions of saturated flow

Movement of poliovirus 1, reovirus 3, and bacteriophage OX174 was studied in 8 different soils. Soils were sampled to a depth of 100 cm in three 33 cm profiles, and packed into acrylic cylinders, 10 cm in dia. and 33.66 and 100 cm in length according to the vertical distribution and bulk density of the soil as found in the field. Sequential flooding of the columns with wastewater and distilled water resulted in a cyclical pattern of viral release in column percolates.The total number of viruses detected in percolates differed among the soils tested. This was due to the differences among soil properties. Poliovirus recovery correlated most favorably with low soil cation exchange capacity and high organic carbon and clay content. The recovery of OX174 was related to low soil organic carbon and residence time of liquid within a column in combination with either high soil pH or per cent clay. As with poliovirus, detection of reovirus in soil column percolates was negatively correlated with soil cation exchange capacity.     

砂土地基强夯地面变形与加固深度的半模试验研究

在量纲分析的基础上,利用尺寸50cm×40cm×60cm(长×宽×高)的玻璃模型箱,采用3种不同干重度的砂土,对之施加4种不同能量的冲击能,观测了不同的夯击能作用时夯点下的地面变形与中心点下不同深度的竖向位移,拟合了位移—深度关系,建立了夯坑深度和有效加固深度与土质参数及施工工艺参数之间无量纲的相关方程,并用工程实例对方程进行了验证。结果表明:方程可有效地定量分析强夯时的夯坑深度和有效加固深度,对强夯法的设计与施工具有一定的指导意义。     

Mobile arsenic species in unpolluted and polluted soils

The fate and behaviour of total arsenic (As) and of As species in soils is of concern for the quality of drinking water. To estimate the relevance of organic As species and the mobility of different As species, we evaluated the vertical distribution of organic and inorganic As species in two uncontaminated and two contaminated upland soils. Dimethylarsinic acid (up to 6 ng As g(-1)), trimethylarsine oxide (up to 1.5 ng As g(-1)), 4 unidentified organic As species (up to 3 ng As g(-1)) and arsenobetaine (up to 15 ng As g(-1)), were detected in the forest soils. Arsenobetaine was the dominant organic As species in both unpolluted and polluted forest soils. No organic As species were detected in the contaminated grassland soil. The organic As species may account for up to 30% of the mobile fraction in the unpolluted forest floor, but never exceed 9% in the unpolluted mineral soil. Highest concentrations of organic As species were found in the forest floors. The concentrations of extractable arsenite were highest in the surface horizons of all soils and may represent up to 36% of total extractable As. The concentrations of extractable arsenate were also highest in the Oa layers in the forest soils and decreased steeply in the mineral soil. In conclusion, the investigated forest soils contain a number of organic As species. The organic As species in forest soils seem to result from throughfall and litterfall and are retained mostly in the forest floor. The relative high concentrations of extractable arsenite, one of the most toxic As species, and arsenate in the forest floor point to the risk of their transfer to surface water by superficial flow under heavy rain events.     

Relationship between persistent organic pollutants (POPs) and ranging patterns in common bottlenose dolphins (Tursiops truncatus) from coastal Georgia, USA

Bottlenose dolphins (Tursiops truncatus) are apex predators in coastal southeastern U.S. waters; as such they are indicators of persistent organic pollutants (POPs) in coastal ecosystems. POP concentrations measured in a dolphin's blubber are influenced by a number of factors, including the animal's sex and ranging pattern in relation to POP point sources. This study examined POP concentrations measured in bottlenose dolphin blubber samples (n = 102) from the Georgia, USA coast in relation to individual ranging patterns and specifically, distance of sightings from a polychlorinated biphenyl (PCB) point source near Brunswick, Georgia. Dolphin ranging patterns were determined based upon 5 years of photo-identification data from two field sites approximately 40 km apart: (1) the Brunswick field site, which included the Turtle/Brunswick River Estuary (TBRE), and (2) the Sapelo field site, which included the Sapelo Island National Estuarine Research Reserve (SINERR). Dolphins were categorized into one of three ranging patterns from photo-identification data. Individuals with sighting histories exclusively within one of the defined field sites were considered to have either Brunswick or Sapelo ranging patterns. Individuals sighted in both field sites were classified as having a Mixed ranging pattern. Brunswick males had the highest concentrations of PCBs reported for any marine mammal. The pattern of PCB congeners was consistent with Aroclor 1268, a highly chlorinated PCB mixture associated with a Superfund site in Brunswick. PCB levels in Sapelo males were lower than in Brunswick males, but comparable to the highest levels measured in other dolphin populations along the southeastern U.S. Female dolphins had higher Aroclor 1268 proportions than males, suggesting that the highly chlorinated congeners associated with Aroclor 1268 may not be offloaded through parturition and lactation, as easily as less halogenated POPs. Individuals sighted farther from the Superfund point source had lower Aroclor 1268 proportions.     

Impact of irrigating rice paddies with groundwater containing arsenic in Bangladesh

Soil and soil-water As profiles were obtained from 4 rice paddies in Bangladesh during the wet growing season (May-November), when surface water with little arsenic is used for irrigation, or during the dry season (January-May), when groundwater elevated in arsenic is used instead. In the upper 5 cm of paddy soil, accumulation of 13+/-12 mg/kg acid-leachable As (n=11) was observed in soil from 3 sites irrigated with groundwater containing 80-180 microg/L As, whereas only 3+/-2 mg/kg acid-leachable As (n=8) was measured at a control site. Dissolved As concentrations averaged 370+/-340 microg/L (n=7) in the upper 5 cm of the soil at the 3 sites irrigated with groundwater containing 80-180 microg/L As, contrasting with soil water As concentrations of only 18+/-7 microg/L (n=4) over the same depth interval at the control site. Despite the accumulation of As in soil and in soil water attributable to irrigation with groundwater containing elevated As levels, there is no evidence of a proportional transfer to rice grains collected from the same sites. Digestion and analysis of individual grains of boro winter rice from the 2 sites irrigated with groundwater containing 150 and 180 microg/L As yielded concentrations of 0.28+/-0.13 mg/kg (n=12) and 0.44+/-0.25 mg/kg (n=12), respectively. The As content of winter rice from the control site was not significantly different though less variable (0.30+/-0.07; n=12). The observations suggest that exposure of the Bangladesh population to As contained in rice is less of an immediate concern than the continued use of groundwater containing elevated As levels for drinking or cooking, or other potential consequences of As accumulation in soil and soil-water.