A chemical and toxicological profile of Dutch North Sea surface sediments

Chemical and toxicological profiles were assessed in surface sediments (fraction <63 μm) from the southern North Sea. In extracts of freeze-dried samples, polybrominated biphenyl (PBB), Irgarol 1051 and phthalate concentrations were below the respective detection limits (except di(2-ethylhexyl)phthalate, which was between 170 and 3300 μg kg⁻¹ dry weight (dw)). Hexabromocyclododecane (HBCD) concentrations were between 0.8 and 6.9 μg kg⁻¹ dw, with highest concentrations at river mouths. Polybrominated diphenylethers (PBDE) concentrations were 0.4–0.6 μg kg⁻¹ dw, decabromodiphenylether (BDE209) 1–32 μg kg⁻¹ dw. The ratio BDE209/PCB153 was used as a tracer for recent emissions, and pointed towards a BDE209 source in the Western Scheldt’s upper estuary. PCBs and PAHs were between 0.19–4.7 and 2.6–200 μg kg⁻¹ dw respectively and generally had highest concentrations at near-shore locations and river mouths.

Responses in the Microtox broad-spectrum and the Mutatox genotoxicity assays were generally low, with near-shore locations giving higher responses. The umu-C genotoxicity and the ER-CALUX assay for estrogenicity showed no response, with the exception of one near-shore location (IJmuiden outer harbour, ER-CALUX).

Highest dioxin-like toxicity (DR-CALUX) was found at near-shore locations, in the outflow of the Rhine/Meuse estuary including a dumping site of harbour sludge. At the Oyster Grounds, DR-CALUX responses appeared to be linked to the occurrence of larger PAHs (4–6 rings). A new, non-destructive clean up procedure resulted in significantly higher DR-CALUX responses than the current protocol. The Dutch legislation on disposal of harbour sludge at sea, dictates the use of the conventional clean up procedure. Our results therefore indicate that probably more dioxin-like toxicity associated with harbour sludge is disposed off at sea than assumed.     

Mercury levels in sediments of central Mediterranean Sea: a 150+ year record from box-cores recovered in the Strait of Sicily

To evaluate the degree of anthropogenic mercury pollution, Hg contents have been measured for box-core sediments sampled along three nearshore–offshore transects in the Strait of Sicily and well constrained for their mineralogy, bulk geochemistry and TOC%. Hg values are generally low (from 15 to 70 μg kg⁻¹); however, depth profiles clearly display upcore rising concentrations (up to 202 μg kg⁻¹ near the SE Sicily coast) that are attributed to anthropogenic load. Based on ²¹⁰Pb chronology, these trends are more dramatic across the last 20–30 years. Geogenic influence is thought to explain some anomalies related to volcanic emission and geothermal activity. Combined effects due to eastward flowing of the Modified Atlantic Water (MAW) and sea bottom morphology drove major anthropogenic accumulation.     

Distribution of pesticides and heavy metals in trophic chain

Determination of triazines herbicides (atrazine and simazine) by high performance liquid chromatography (HPLC) in samples of trophic chain were worked out. Determination limits of 0.5 μg g⁻¹ for atrazine, 0.8 μg g⁻¹ for simazine with pesticides recovery of 70–77% in trophic chain samples were obtained. The content of simazine in soils was in range 1.72–57.89 μg g⁻¹, in grass 5–88 μg g⁻¹, in milk 2.32–15.29 μg g⁻¹, in cereals 10.98–387 μg g⁻¹, in eggs 30.14–59.48 μg g⁻¹, for fruits: 2.45–6.19 μg g⁻¹. The content of atrazine in soils was in range 0.69–19.59 μg g⁻¹, in grass 7.85–23.85 μg g⁻¹, in cereals 1.88–43.08 μg g⁻¹. Cadmium, lead and zinc were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) in the same samples as atrazine and simazine. Determination limits for cadmium 5 × 10⁻³ μg g⁻¹, for lead 1 × 10⁻² μg g⁻¹, and for zinc 0.2 × 10⁻³ μg g⁻¹, were obtained. The content of cadmium in soil was in range 0.13–5.89 μg g⁻¹, in grass 114–627.72 × 10⁻³ μg g⁻¹, in milk 8.88–61.88 × 10⁻³ μg g⁻¹, in cereals 0.20–0.31 μg g⁻¹, in eggs 0.11–0.15 μg g⁻¹, in fruits 0.23–0.59 μg g⁻¹. The content of lead in soils was in range 0.57–151.50 μg g⁻¹, in grass 0.16–136.57 μg g⁻¹, in milk 1.16–3.74 μg g⁻¹, in cereals 1.05–5.47 μg g⁻¹, in eggs 5.79–55.87 μg g⁻¹, in fruits 21.00–87.36 μg g⁻¹. Zinc content in soil was in range 9.15–424.5 μg g⁻¹, in grass 35.20–55.87 μg g⁻¹, in milk 20.00–34.38 μg g⁻¹, in cereals 14.94–28.78 μg g⁻¹, in eggs 15.67–32.01 μg g⁻¹, in fruits 14.94–18.88 μg g⁻¹.

Described below extraction and mineralization methods for particular trophic chains allowed to determine of atrazine, simazine, cadmium, lead and zinc with good repeatability and precision. Emphasis was focused on liquid–liquid extraction and solid-phase extraction of atrazine and simazine from analysed materials, as well as, on monitoring the content of herbicides and metals in soil and along trophic chain. Higher concentration of pesticides in samples from west region of Poland in comparison to that of east region is likely related to common applying them in Western Europe in relation to East Europe. The content of metals strongly depends on samples origin (industry area, vicinity of motorways).     

Determination of 4-tert-octylphenol, 4-nonylphenol and bisphenol A in surface waters from the Haihe River in Tianjin by gas chromatography-mass spectrometry with selected ion monitoring

The estrogenic pollutants 4-tert-octylphenol (OP), 4-nonylphenol (NP) and bisphenol A (BPA) were determined in surface water samples from the Haihe River, Tianjin, China. The analytes were extracted and concentrated from 300 ml acidified water samples by liquid–liquid extractions using dichloromethane, derivatized with trifluoroacetic anhydride, and quantified by gas chromatography–mass spectrometry (GC–MS) with selected ion monitoring (SIM). Among the samples collected from 14 sampling sites, only one sample was found to have a relatively high concentration of BPA (8.30 μg l⁻¹) and NP (0.55 μg l⁻¹). The concentrations of OP, NP and BPA in the other samples were in the range of 18.0–20.2, 106–296 and 19.1–106 ng l⁻¹, respectively. Recoveries for OP, NP and BPA in the spiked water samples were all over 80%.     

Octyl and nonylphenol ethoxylates and carboxylates in wastewater and sediments by liquid chromatography/tandem mass spectrometry

This work presents an LC–MS–MS-based method for the quantitation of nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) in water, sediment, and suspended particulate matter, and three of their carboxylated derivatives in water. The alkylphenol ethoxylates (APEOs) were analyzed using isotope dilution mass spectrometry with [¹³C₆]-labeled analogues, whereas the carboxylated derivatives were determined by external standard quantitation followed by confirmation using standard additions. The method was used to study APEO’s behavior in a wastewater treatment plant (WWTP), where total dissolved NP0-16EO concentration was reduced by approximately 99% from influent (390 μg l⁻¹) to final effluent (4 μg l⁻¹), and total OP0-5EO concentration decreased by 94% from 3.1 to 0.2 μg l⁻¹. In contrast, the carboxylated derivatives were formed during the process with NP0-1EC concentrations increasing from 1.4 to 24 μg l⁻¹. Short-chain APEOs were present in higher proportions in particulate matter, presumably due to greater affinity for solids compared to the long-chain homologues. NP (0.49 μg l⁻¹) and NP0-1EC (4.8 μg l⁻¹) were the only APEO-related compounds detected in a surface water sample from a WWTP-impacted estuary; implying that 90% of the mass was in the form of carboxylated derivatives. Sediment analysis showed nonylphenol to be the single most abundant compound in sediments from the Baltimore Harbor area, where differences in homologue distribution suggested the presence of treated effluent in some of the sites and non-treated sources in the rest.     

Distribution of polycyclic aromatic hydrocarbons in agricultural soils in South Korea

The content and type of polycyclic aromatic hydrocarbons (PAH) in soils from paddy fields and upland areas in South Korea were determined using gas chromatography linked to mass spectrometry (GC–MS). The distribution map of total PAH content was obtained as a contour plot using a geographical information system. The overall distribution of PAH was found to be closely related to the pollution sources, the size of city and the type of industry. The average content of total PAH in all samples was 236 μg kg⁻¹, and the range was from 23.3 to 2834 μg kg⁻¹. The highest concentrations were found in soils sampled near iron processing plants. The concentration of PAH decreased in the order fluoroanthene>benzo(b)fluoroanthene>pyrene. Special PAH compound ratios, such as phenanthrene/anthracene and fluoroanthene/pyrene, were calculated to evaluate the origin. The collected data suggested that the pyrogenic origins such as motor vehicle exhaust and heavy industry emission were the dominant source of PAH in Korean soils.     

Concentrations of chlorine, bromine and iodine in Japanese rivers

Concentrations of halogens (Cl, Br and I) in 30 Japanese rivers were measured by ion chromatography and inductively coupled plasma mass spectrometry to understand their behavior in the terrestrial environment. Concentrations of Cl, Br and I in each river, obtained at 10 sampling points from the upper stream to the river mouth, tended to increase near the river mouth. The ranges of geometric means of Cl, Br and I in each river were 1.0–19.4 mg l⁻¹, 2.5–67.9 μg l⁻¹, and 0.18–8.34 μg l⁻¹, respectively. To compare halogen behavior, the concentration ratios, Br/Cl and I/Cl, were calculated. The Br/Cl range was (2.3–7.8) × 10⁻³ (geometric mean: 3.74 × 10⁻³), and it was nearly constant except for the Yoneshiro river. It was estimated that 60–80% of total Br in the middle to lower parts of this river was the excess Br. The Br chemical form in all the rivers is generally considered to be Br⁻. The I/Cl ratios had different trends in rivers flowing into the Japan Sea and Pacific Ocean, possibly due to the different geological features in the river catchments.     

Determination and distribution characteristics of degradation products of nonylphenol polyethoxylates in the rivers of Taiwan

Concentrations of degradation products of nonylphenol polyethoxylates (NPEOs) were analyzed in river water samples in order to determine the distribution characteristic of these alkylphenolic compounds in 18 major rivers of Taiwan. The degradation products of NPEOs were detected in all river samples, with the dicarboxylates alkylphenolic degradation products (CAPEC) being detected most frequently and at the highest concentrations. Concentrations of NP and NP1EO in rivers ranged from n.d. to 5.1 μg l⁻¹ and n.d. to 0.5 μg l⁻¹, respectively. The total concentrations of shortened carboxylates (i.e., NP1EC + NP2EC + NP3EC) and dicarboxylates alkylphenolic degradation products (CAP1EC + CAP2EC) ranged from n.d. to 63.6 μg l⁻¹ and n.d. to 94.6 μg l⁻¹, respectively. Concentrations of NP2EC, NP3EC and all CAPEC residues were determined semi-quantitatively by comparing with the internal standard. Significantly higher concentrations of CAPEC residues were detected in the river waters as compared to those of NP, NP1EO and NPEC degradation products and the average proportions of these compounds in the samples of the rivers were as follows: NP + NP1EO was 5 ± 2.5%, total NPEC was 25 ± 12%, and total CAPEC was 70 ± 12%. The high concentration ratios of CAPEC/NPEC illustrate that aerobic biodegradation plays a main route in the fate of NPEO in the rivers of Taiwan.     

Antimony content of macrofungi from clean and polluted areas

Species of macrofungi (mushrooms) were collected from clean areas and analyzed for their antimony content. These were compared to species collected from extremely polluted areas in the vicinity of a lead smelter and on mine and slag dumps. Antimony content was determined using long-term instrumental neutron activation analysis (INAA). Ectomycorrhizal and terrestrial saprobic macrofungi were examined. Antimony content of macrofungi from the clean areas was mostly less than 100 μg kg⁻¹ (dry mass). The highest concentrations (units of mg kg⁻¹) were found in various species of the ectomycorrhizal genera Chalciporus and Suillus. Antimony contents of macrofungi growing in the polluted areas were considerably higher. The highest content was found in a single collection of Chalciporus piperatus (1423 mg kg⁻¹).     

Isoprene emission from tropical trees in Okinawa Island, Japan

This study surveyed isoprene emission from 42 indigenous and exotic tropical trees in subtropic Okinawa, Japan. Of the 42 trees studied, 4 emitted isoprene at a rate in excess of 20 μg g⁻¹ h⁻¹, and 28 showed the rates of 1–10 μg g⁻¹ h⁻¹. The remainder emitted less than 1 μg g⁻¹ h⁻¹. The majority of trees in this study may therefore fall within the lower emitting species. However, species in Moraceae that is indigenous in Okinawa emitted isoprene at relatively higher rates with an average of 14.2 μg g⁻¹ h⁻¹. The highest emission rate of 107.1 μg g⁻¹ h⁻¹ for Ficus virgata yielded the area basis rate of 47.4 nmol m⁻² s⁻¹, which is almost equivalent to the rate of high emitting species. Furthermore, a linear relationship between light intensity and isoprene emission was noted with Ficus virgata up to 1700 μmol m⁻² s⁻¹. These findings may show the potential importance of subtropical areas as sources of isoprene to the atmosphere.     

Utilization and degradation of imazaquin by a naturally occurring isolate of Arthrobacter crystallopoietes

A species of bacteria that is capable of utilizing imazaquin as the sole carbon source was isolated from soil with repeated imazaquin applications, and was identified as Arthrobacter crystallopoietes (designated as strain “WWX-1”). This isolate degrades imazaquin as high as 200 μg ml⁻¹, and the estimated dissipation half-lives increased from 1.51 d for the treatment at 50 μg ml⁻¹ to 4.75 d for 200 μg ml⁻¹. Optimal growth of WWX-1 in mineral salt medium with 50 μg ml⁻¹ imazaquin was obtained at 35 °C and a pH of 5.0. Growth of WWX-1 was also observed in mineral salt medium with the addition of other imidazolinone herbicides such as imazethapyr and imazapyr, but not with different classes of herbicides such as metsulfuron-methyl. Two imazaquin metabolites were detected, and spectral analysis with HPLC–MS, ¹H NMR, and IR revealed one metabolite with a molecular weight (MW) of 199 as quinoline-2,3-dicarboxylic anhydride. We propose that A. crystallopoietes (WWX-1) could serve as an efficient biodegradation system for remediation of water and soils that are heavily contaminated with imazaquin or other structurally similar chemicals.     

Tidal salt marsh sediment in California, USA. Part 2: occurrence and anthropogenic input of trace metals

Surface sediment samples (0–5 cm) from 5 tidal salt marshes along the coast in California, USA were analyzed to investigate the occurrence and anthropogenic input of trace metals. Among study areas, Stege Marsh located in the central San Francisco Bay was the most contaminated marsh. Concentrations of metals in Stege Marsh sediments were higher than San Francisco Bay ambient levels. Zinc (55.3–744 μg g⁻¹) was the most abundant trace metal and was followed by lead (26.6–273 μg g⁻¹). Aluminum normalized enrichment factors revealed that lead was the most anthropogenically impacted metal in all marshes. Enrichment factors of lead in Stege Marsh ranged from 8 to 49 (median = 16). Sediments from reference marshes also had high enrichment factors (2–8) for lead, indicating that lead contamination is ubiquitous, possibly due to continuous input from atmospherically transported lead that was previously used as a gasoline additive. Copper, silver, and zinc in Stege Marsh were also enriched by anthropogenic input. Though nickel concentrations in Stege Marsh and reference marshes exceeded sediment quality guidelines, enrichment factors indicated nickel from anthropogenic input was negligible. Presence of nickel-rich source rock such as serpentinite in the San Francisco Bay watershed can explain high levels of nickel in this area. Coefficients of variation were significantly different between anthropogenically impacted and non-impacted metals and might be used as a less conservative indicator for anthropogenic input of metals when enrichment factors are not available.     

Nonylphenols in freshwaters of the hydrologic system of an Italian district: association with human activities and evaluation of human exposure

A sampling campaign for the determination of concentrations of nonylphenol isomers (NPs) in freshwaters and sediments of the hydrologic system of the Rieti district (central Italy) was conducted from 2002 to 2003. Eighteen sampling points, selected on the basis of the different human activities in the vicinity, were monitored; six series of water samples (from June 2002 to February 2003) and one of sediment samples (summer 2002) were analyzed by GC/MS.

There was a direct relationship between concentrations of NPs and the presence of urban or industrial activities near the sampling point. However, concentrations of NPs in water were in the range of <0.1–1.4 μg l⁻¹, and their presence limited to short distances from the sources of contamination. Accumulation factors in sediment samples ranged from 10² to 5 × 10³.     

Mercury deposition through litterfall in an Atlantic forest at Ilha Grande, Southeast Brazil

Atmospheric Hg transfer to the forest soil through litterfall was investigated in a primary rainforest at Ilha Grande (Southeast Brazil) from January to December 1997. Litter mass deposition reached 10.0 t ha⁻¹ y⁻¹, with leaves composing 50–84% of the total litter mass. Concentrations of Hg in the total fallen litter varied from 20 to 244 ng g⁻¹, with higher concentrations during the dry season, between June and August (225 ± 17 ng g⁻¹), and lower concentrations during the rainy season (99 ± 54 ng g⁻¹). This seasonal variability was reflected in the Hg flux through litterfall, which corresponded to a Hg input to the forest floor of 122 μg m⁻² y⁻¹, with average Hg deposition of 16.5 ± 1.5 μg m⁻² month⁻¹ during and just after the dry season (June–September) and 7.0 ± 3.6 μg m⁻² month⁻¹ in the rest of the year. The variability in meteorological conditions (determining atmospheric Hg availability to foliar scavenging) may explain the pulsed pattern of Hg deposition, since litterfall temporal variability was generally unrelated with such deposition, except by a peak in litterfall production in September. Comparisons with regional data on Hg atmospheric deposition show that litterfall promotes Hg deposition at Ilha Grande two to three orders of magnitude higher than open rainfall deposition in non-industrialized areas and approximately two times higher than open rainfall deposition in industrialized areas in Rio de Janeiro State. The observed input suggests that atmospheric Hg transfer through litterfall may explain a larger fraction of the total Hg input to forest soils in Southeast Brazil than those recorded at higher latitudes.     

A qualitative field method for monitoring pesticides in the edge-of-field runoff

A field method is described, which allows the qualitative estimation of pesticide contamination in the edgeof-field runoff. The method employs cheap and easy-to-use runoff sampling bottles, which were installed in an agricultural stream catchment over a period of three growing seasons. During this time 18 runoff events were detected, in nine of which insecticide contamination was measured (maximum concentrations: lindane 0.7 μg l⁻¹ and 12.7 μg kg⁻¹, parathion 20 μg l⁻¹ and 728 μg kg⁻, fenvalerate 18.4 μg 1-1 and 924 μg kg⁻¹). These insecticides were detected mainly as particle-bound chemicals. On about 80 % of the occasions the presence or absence of runoff measured in the field was in agreement with a simulation of runoff presence or absence using the runoff model KINEROS.     

Methane fluxes from tundra soils and snowpack in the maritime Antarctic

Methane fluxes were measured from three exposed tundra sites and four snowpack sites on the Fildes Peninsula in the maritime Antarctic in the summertime of 2002. The average fluxes at two normal tundra sites were −15.3 μg m⁻² h⁻¹ and −14.3 μg m⁻² h⁻¹, respectively. The fluxes from tundra site with fresh penguin dropping addition showed positive values with the average of 36.1 μg m⁻² h⁻¹, suggesting that the deposition of fresh droppings greatly enhanced CH₄ emissions from the poor Antarctic tundra during penguin breeding periods. The summertime variation in CH₄ flux was correlated with surface ground temperature and the precipitation. The correlation between the flux and PT₀, which is the product of the precipitation and surface ground temperature, was quite strong. The diurnal cycle of CH₄ flux from the tundra soils was not obtained due to local fluky weather conditions. The fluxes through four snowpack sites were also obtained by the vertical CH₄ concentration gradient and their average fluxes were −46.5 μg m⁻² h⁻¹, −28.2 μg m⁻² h⁻¹, −46.4 μg m⁻² h⁻¹ and −17.9 μg m⁻² h⁻¹, respectively, indicating that tundra soils under snowpack also consume atmospheric CH₄ in the maritime Antarctic; therefore these fluxes could constitute an important part of the annual CH₄ budget for Antarctic tundra ecosystem.     

TBT and TPhT persistence in a sludged soil

The persistence of tributyltin (TBT) and triphenyltin (TPhT) in soils was studied, taking into consideration the quantity of sewage sludge, TBT and TPhT concentrations in soil as well as the soil pH. The organotin compounds (OTC) were introduced into the soil via a spiked urban sludge, simulating agricultural practise. OTC speciation was achieved after acidic extraction of soil samples followed by gas chromatography–pulsed flame photometric analysis (GC–PFPD). Leaching tests conducted on a spiked sludge showed that more than 98% of TBT are sorbed on the sludge. TBT persistence in soil appeared to depend on its initial concentration in sludge. Thus, it was more important when concentration is over 1000 μg(Sn) kg⁻¹ of sludge. More than 50% of the initial TBT added into the soil were still present after 2 months, whatever the experimental conditions. The main degradation product appeared to be dibutyltin. About 90% of TPhT were initially sorbed on sludge, whatever the spiking concentration in sludge was. However, TPhT seemed to be quantitatively exchangeable at the solid/liquid interface, according to the leaching tests. It was also significantly degraded in sludged soil as only about 20% of TPhT remain present after 2 months, the monophenyltin being the main degradation product. pH had a significant positive effect on TBT and particularly TPhT persistence, according to the initial amounts introduced into the soil. Thus, at pH over 7 and triorganotin concentration over 100 μg(Sn) kg⁻¹, less than 10% of TBT but about 60% of TPhT were degraded. When the sludge was moderately contaminated by triorganotins (typically 50 μg(Sn) kg⁻¹ in our conditions) the pH had no effect on TBT and TPhT persistence.     

Endocrine disrupter nonylphenol and bisphenol A contamination in Okinawa and Ishigaki Islands, Japan--within coral reefs and adjacent river mouths

Certain chemicals possess the potential to modulate endocrine systems, and thereby interfere with reproduction and developmental processes in the wild. We analyzed endocrine disrupters nonylphenol (NP) and bisphenol A (BPA) levels at various sites in Okinawa and Ishigaki Islands, Japan. River-water samples showed undetectable to low concentrations of NP and BPA at most of the sites investigated. However, an appreciable amount of BPA was detected in sediments at one coral reef site. In addition, significant numbers of river sediment samples showed appreciable amounts of NP and BPA. Most of the sampling sites for this study are located within a distance of 1 km from the coral reefs, which are under influence of river-waters to a variable extent. Therefore, influence of endocrine disrupters may have already begun on adjacent coral reefs. Both endocrine disrupters were positively correlated with human population densities, but not with the contents of red soil generated by farm land reformation. Therefore, it is concluded that NP and BPA pollution is a consequence of human waste discharge, both domestic and industrial, and not by agricultural activities.     

The enhancement of photodegradation efficiency using Pt-TiO2 catalyst

The residues from the extraction of lead/zinc (Pb/Zn) ores of most Pb/Zn mines are permanently stored in tailings ponds, which require revegetation to reduce their environmental impact. This can only be done if the main constraints on plant establishment are evaluated. This can readily be done by field and greenhouse studies.

To test this, the properties of different tailings from Lechang Pb/Zn mine located at the north of Guangdong Province in southern China have been studied. Physical and chemical properties including concentrations of metals (Pb, Zn, Cd and Cu) in the tailings and soils collected from different sites have been measured. The results showed that tailings contain low nitrogen (0.016–0.075%), low-organic matter (0.58–1.78%), high salt (3.55–13.85 dS/m), and high total and diethylene–tetramine–pentaacetic acid (DTPA)-extractable metal concentrations (total: 1019–1642 μg g⁻¹ Pb, 3078–6773 μg g⁻¹ Zn, 8–23 μg g⁻¹ Cd, and 85–192 μg g⁻¹ Cu; DTPA-extractable: 59–178 μg g⁻¹ Pb, 21–200 μg g⁻¹ Zn, 0.30–1.5 μg g⁻¹ Cd, and 4.3–12 μg g⁻¹ Cu). Aqueous extracts of tailings/soils (10%, 20% and 30%, w/v) from different sites were prepared for testing their effects on seed germination and root elongation of a vegetable crop Brassica chinensis and a grass species Cynodon dactylon. It was found that root elongation provided a better evaluation of toxicity than seed germination. The ranking of toxicity using root elongation was: high-sulfur tailings>tailingdam>sparsely vegetated tailings>densely vegetated tailings>mountain soil for both plants. This order was consistent with DTPA-extractable Pb contents in the tailings and soils. B. chinensis seedlings were then grown in the mixtures of different proportions of tailings and farm soil for 4 weeks, and the results (dry weights of seedlings) were in line with the root elongation test. All these demonstrated that heavy metal toxicity, especially available Pb, low content of nutrient, and poor physical structure were major constraints on plant establishment and colonization on the Pb/Zn mine tailings.     

Selective adsorption of phenanthrene dissolved in surfactant solution using activated carbon

Selective adsorption of a hazardous hydrophobic organic compound (HOC) by activated carbon as a means of recovering surfactants after a soil washing process was investigated. As a model system, phenanthrene was selected as a representative HOC and Triton X-100 as a nonionic surfactant. Three activated carbons that differed in size (Darco 20–40 (D20), 12–20 (D12) and 4–12 (D4) mesh sizes) were used in adsorption experiments. Adsorption of surfactant onto activated carbon showed a constant maximum above the critical micelle concentration, which were 0.30, 0.23, 0.15 g g⁻¹ for D20, D12, and D4, respectively. Selectivity for phenanthrene to Triton X-100 was much higher than 1 over a wide range of activated carbon doses (0–6 g l⁻¹) and initial phenanthrene concentrations (10–110 mg l⁻¹). Selectivity generally increased with decreasing particle size, increasing activated carbon dose, and decreasing initial concentration of phenanthrene. The highest selectivity was 74.9, 57.3, and 38.3 for D20, D12, and D4, respectively, at the initial conditions of 10 mg l⁻¹ phenanthrene, 5 g l⁻¹ Triton X-100 and 1 g l⁻¹ activated carbon. In the case of D20 at the same conditions, 86.5% of the initial phenanthrene was removed by sorption and 93.6% of the initial Triton X-100 remained in the solution following the selective adsorption process. The results suggest that the selective adsorption by activated carbon is a good alternative for surfactant recovery in a soil washing process.