Survival, Pb-uptake and behaviour of three species of earthworm in Pb treated soils determined using an OECD-style toxicity test and a soil avoidance test

Mature (clitellate) Eisenia andrei Bouché (ultra epigeic), Lumbricus rubellus Hoffmeister (epigeic), and Aporrectodea caliginosa (Savigny) (endogeic) earthworms were placed in soils treated with Pb(NO(3))(2) to have concentrations in the range 1,000 to 10,000 mg Pb kg(-1). After 28 days LC50(-95%confidence limit)(+95%confidence limit) values were E. andrei 5824(-361)(+898) mg Pb kg(-1), L. rubellus 2867(-193)(+145) mg Pb kg(-1) and A. caliginosa2747(-304)(+239) mg Pb kg(-1) and EC50s for weight change were E. andrei2841(-68)(+150) mg Pb kg(-1), L. rubellus1303(-201)(+240) mg Pb kg(-1) and A. caliginosa1208(-206)(+212) mg Pb kg(-1). At any given soil Pb concentration, Pb tissue concentrations after 28 days were the same for all three earthworm species. In a soil avoidance test there was no difference between the behaviour of the different species. The lower sensitivity to Pb exhibited by E. andrei is most likely due to physiological adaptations associated with the modes of life of the earthworms, and could have serious implications for the use of this earthworm as the species of choice in standard toxicological testing.     

Organotin contamination in fishes with different living patterns and its implications for human health risk in Taiwan

Contaminated levels of butyl- and phenyltin compounds, tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT), diphenlytin (DPT), and monophenyltin (MPT), were investigated in pelagic, demersal and cultured fish species from different seasons and locations in Taiwan. Seasonal variations were found in fishes from Wuchi and Hsingta fishing harbors for their butyltin levels (winter>summer) with the opposite trend for phenyltins in fishes from Patoutzu fishing harbor and demersal fishes from four fishing harbors (summer>winter). Fish liver contained the lowest percentage of TBT and the highest percentage of TPT among six organotin compounds. Consumption of contaminated pelagic species and fishes from Hsingta fishing harbor had the highest hazard index. However, the hazard quotients and hazard indices were all less than 1, suggesting a daily exposure at these levels of TBT, DBT and TPT may not be likely to cause any deleterious effects during lifetime in human population.     

Bulk deposition in a rural area located around a large coal-fired power station, northeast Spain

This work focuses on bulk deposition in a rural area located around a large coal-fired power station in northeast Spain. Deposition chemistry was characterised by high concentrations of SO(4)(2-), Ca(2+) and NH(4)(+), which were relatively high when compared with other rural areas. Monthly bulk deposition evolution of major ions was the result of two superimposed patterns: one pattern related to the volume of precipitation and the other showed the seasonal influence of the major ionic sources. A major local origin was attributed to bulk deposition of SO(4)(2-), NH(4)(+), and Ca(2+), whereas a relatively higher contribution of an external source was deduced for NO(3)(-), Na(+) and Cl(-). The SO(4)(2-) concentrations showed a significant correlation with the local SO(2) emissions. High levels of Ca(2+) were due to the high alkalinity of soils in the study area, although an external origin was attributed to the frequent air mass intrusions from the Sahara. Sources of NH(4)(+) were related to intensive livestock farming in the area. Total suspended particles exert a marked influence over bulk deposition and neutralisation. Thus, despite the high emissions of SO(2) in the area, neutral pH values have always been attained given that the concentrations of Ca(2+) and NH(4)(+) account for the total neutralisation of NO(3)(-) and SO(4)(2-).     

Dry deposition, ionic species measured and source interpretation during seasonal cycle at offshore areas near Taiwan Strait

The characterization for water-soluble species of total suspended particulate (TSP), dry deposition flux, and dry deposition velocity (V(d)) were studied at Taichung Harbor (TH) and Wuchi traffic sampling sites at offshore sampling site near Taiwan Strait of central Taiwan during March 2004-January 2005. The average concentrations of TSP and dry deposition flux at the TH sampling site were higher than at the WT sampling site during the sampling period. The samples collected were analyzed by a ion chromatography (DIONEX-100) for the ionic species (Cl(-), SO(4)(2-), NO(3)(-), NH(4)(+), Na(+), Ca(2+), and Mg(2+)) analysis. The dominant ionic species for TSP are SO(4)(2-), NO(3)(-), and NH(4)(+) of the total mass of the inorganic ions at both sampling sites. In addition, the results indicated that the NH(4)(+), NO(3)(-) and SO(4)(2-) showed higher concentrations in winter and lower in summer for both TH and Wuchi sampling sites. Statistical methods such as correlation coefficient and principal component analysis were also used to identify the possible pollutant source.     

Microplastics distribution and possible ingestion by fish in lacustrine waters (Lake Bracciano,Italy)

Understanding the spatial distribution patterns of microplastics (plastics?<?5 mm) contributes to the assessment of sources and sinks of pollution thus providing information for the management of biota safety and overall ecosystem functionality. We chose a semi-closed study area, Lake Bracciano (Italy), to assess the environmental variability of contamination, focusing on the water compartment and the exposure of biota, specifically fish, by analysing the ingestion of microplastics. The focus of this study is to evaluate the concentration of microplastics in water (surface and column) across the lake and the ingestion of microplastics by two fish species of economic interest: Atherina boyeri and Coregonus lavaretus, inhabiting demersal and pelagic habitats respectively. Results show a surface contamination of 392,000?±?417,000 items km^?2 and a column one of 0.76?±?1.00 items m^?3. Fragments were the most abundant in surface while fibres in the column. Microplastics were found in C. lavaretus specimens, corresponding to contamination frequency of 5% and concentration of 0.15 items/fish. The main polymer found in water was polyethylene (81%); of minor percentages, there were various other polymers, including polystyrene and acrylic, which were also found in fish. As scientific literature provides few research where water and fish are simultaneously sampled, this investigation wants to contribute filling this knowledge gap by investigating for the first time a volcanic lake.

     

Levels and distribution of organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers in sediments and biota from the Danube Delta, Romania

Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs), such as dichlorodiphenyltrichloroethane (DDT) and analogues, hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB), were measured in sediments and biota (invertebrates, 11 fish species and cormorant tissues) collected in 2001 from the Danube Delta, the biggest European wetland. DDTs were the predominant pollutants in all samples. A high variability in the concentrations of pollutants within the same species was observed and this was related to sampling location, age, length and sex. DDTs were also the main organohalogenated contaminants in cormorant muscle and liver, followed by PCBs, HCHs, HCB and PBDEs. The present levels of DDTs in cormorant tissues are lower than levels measured in cormorant eggs sampled from the Danube Delta in 1982 and 1997, respectively. The variance of delta15N for herbivores was much greater than for carnivores, while carp and bream showed higher delta15N signatures than expected, probably due to a higher dietary proportion of benthos, typically more delta15N enriched relative to pelagic biota.     

Assessment of inorganic lead species and total organo-alkyllead in some Egyptian agricultural soils

This study was carried out to assess the amounts of (i) total Pb in soil, (ii) inorganic Pb species: exchangeable (EXCH), carbonate (CARB), easily reducible (EASR), moderately reducible (MODR), organic matter and sulfides (ORGS), and residual (RESD) bound Pb, and (iii) total organo-lead as alkyllead, in alluvial and lacustrine soils of the Nile delta, Egypt. Wide ranges of soil Pb were found in the alluvial (18.2-1850 microg g(-1)) and the lacustrine (39-1985 microg g(-1)) soils. The topsoil was highly enriched with Pb relative to the subsurface soils, especially in highly contaminated soils. There was no significant relationship between soil type and Pb content. Amounts of soil Pb greater than the background level (14 microg g(-1)) are due to Pb deposited from various anthropogenic activities. The partitioning of soil Pb into different species varied according to the intensity of contamination. It followed the sequence: RESD > ORGS > CARB > MODR > EASR in the slightly contaminated alluvial as well as lacustrine soils. In the highly contaminated soils, it followed the sequence: ORGS > MODR > CARB > EASR > RESD in the alluvial soils, and the sequence: ORGS > CARB > MODR > EASR > RESD in the lacustrine soils. There is high binding capacity of organic matter and sulfides to Pb, especially in the highly contaminated soils. The concentrations of total alkyllead in soils varied markedly and were related to both intensity of contamination and depth in the soil. The subsurface soil (15-30 cm) was highly enriched by alkyllead (means 224 and 353 ng g(-1) in the alluvial and lacustrine soils, respectively) relative to the surface and deeper soils. The proportion of total alkyllead as a percentage of total Pb in the soil was generally very low. It did not exceed 1.6% in the slightly contaminated soils, and 0.6% in the highly contaminated ones.     

Atmospheric nitrogen inputs to the Delaware Inland Bays: the role of ammonia

A previous assessment of nitrogen loading to the Delaware Inland Bays indicates that atmospheric deposition provides 15-25% of the total, annual N input to these estuaries. A large and increasing fraction of the atmospheric wet flux is NH(4)(+), which for most aquatic organisms represents the most readily assimilated form of this nutrient. Particularly noteworthy is a 60% increase in the precipitation NH(4)(+) concentration at Lewes, DE over the past 20 years, which parallels the increase in poultry production on the Delmarva Peninsula over this period (currently standing at nearly 585 million birds annually). To further examine the relationship between local NH(3) emissions and deposition, biweekly-integrated gaseous NH(3) concentrations were determined using Ogawa passive samplers deployed at 13 sampling sites throughout the Inland Bays watershed over a one-year period. Annual mean concentrations at the 13 sites ranged from <0.5 microg NH(3)m(-3) to >6 microg NH(3)m(-3), with a mean of 1.6+/-1.0 microg NH(3)m(-3). At most sites, highest NH(3) concentrations were evident during spring and summer, when fertilizer application and poultry house ventilation rates are greatest, and seasonally elevated temperatures induce increased rates of microbial activity and volatilization from soils and animal wastes. The observed north-to-south concentration gradient across the watershed is consistent with the spatial distribution of poultry houses, as revealed by a GIS analysis of aerial photographs. Based on the average measured NH(3) concentration and published NH(3) deposition rates to water surfaces (5-8 mm s(-1)), the direct atmospheric deposition of gaseous NH(3) to the Inland Bays is 3.0-4.8 kg ha(-1)yr(-1). This input, not accounted for in previous assessments of atmospheric loading to the Inland Bays, would effectively double the estimated direct dry deposition rate, and is on par with the NO(3)(-) and NH(4)(+) wet fluxes. A second component of this study examined spatial differences in NO(3)(-) and NH(4)(+) wet deposition within the Inland Bays watershed. In a pilot study, precipitation composition at the Lewes NADP-AIRMoN site (DE 02) was compared with that at a satellite site established at Riverdale on the Indian River Estuary, approximately 21 km southwest. While the volume-weighted mean precipitation NO(3)(-) concentrations did not differ significantly between sites, the NH(4)(+) concentration observed at Riverdale (26.3 micromoles L(-1)) was 73% greater than at Lewes (15.2 micromoles L(-1)). More recently, a NADP site was established at Trap Pond, DE (DE 99), which was intentionally located within the region of intense poultry production. A comparison of the initial two years (6/2001-5/2003) of precipitation chemistry data from Trap Pond with other nearby NADP-AIRMoN sites (Lewes and Smith Island) reveals fairly homogeneous NO(3)(-) wet deposition, but significant spatial differences ( approximately 60%) in the NH(4)(+) wet flux. Overall, these results suggest that local emissions and below-cloud scavenging provide a significant contribution to regional atmospheric N deposition.     

Dynamics of nitrogen in a PAHs contaminated soil amended with biosolid or vermicompost in the presence of earthworms

Nitrogen mineralization in PAHs contaminated soil in presence of Eisenia fetida amended with biosolid or vermicompost was investigated. Sterilized and unsterilized soil was contaminated with PAHs, added with E. fetida and biosolid or vermicompost and incubated aerobically for 70 days, while dynamics of inorganic N were monitored. Addition of E. fetida to sterilized soil increased concentration of NH(4)(+) 100> mg N kg(-1), while concentrations in unsterilized remained <60 mg N kg(-1) except for soil amended with biosolid plus PAHs where it increased to >80 mg kg(-1). Addition of PAHs had no significant effect on concentration of NH(4)(+) compared to the unamended soil, except in the soil added with biosolid. Addition of E. fetida to sterilized soil increased concentration of NO(2)(-) 15> mg N kg(-1) while concentrations in unsterilized soil remained <7.5 mg N kg(-1) except for soil amended with biosolid where it increased to >20 mg kg(-1). Addition of PAHs had no significant effect on concentration of NO(2)(-) compared to the unamended soil. Addition of biosolid and vermicompost increased concentration of NO(3)(-), while addition of E. fetida decreased concentration of NO(3)(-) in biosolid amended soil. It was found that NH(4)(+) and NO(2)(-) oxidizers were present in the gut of E. fetida, but their activity was not sufficient enough to inhibit a temporarily increase in concentrations of NH(4)(+) and NO(2)(-). Contamination with PAHs induced immobilization of N in biosolid or vermicompost amended soil, as did feeding of E. fetida on biosolid or vermicompost.     

Bioaccumulation of cyclopenta[cd]pyrene and benzo[ghi]fluoranthene by mussels transplanted in a coastal lagoon

The bioaccumulation of two isomeric non-alternant non-priority polycyclic aromatic hydrocarbons (PAHs), namely cyclopenta[cd]pyrene and benzo[ghi]fluoranthene, was investigated in caged mussels (Mytilus galloprovincialis) exposed for 30 days in three sites of a coastal lagoon (Pialassa Baiona, Ravenna, Italy) contaminated by pyrogenic PAHs. The concentration of cyclopenta[cd]pyrene and benzo[ghi]fluoranthene increased from undetectable levels in reference mussels withdrawn from the Adriatic sea to 10-30 ng g(-1) dry weight in transplanted mussels. Other contaminants bioaccumulated by caged mussels included pyrene, fluoranthene and mercury. Whilst the isomer concentration ratio pyrene/fluoranthene in biota was comparable to that observed in sediments, the cyclopenta[cd]pyrene/benzo[ghi]fluoranthene ratio was much lower in mussels than in sediments. The lower sediment biota accumulation factor of cyclopenta[cd]pyrene with respect to that of benzo[ghi]fluoranthene was tentatively attributed to the greater biological activity of the former compound, which contains a reactive olefinic bond in the cyclopenta fused ring moiety. Given the higher mutagenic activity of cyclopenta[cd]pyrene with respect to other priority PAHs, its bioaccumulation from contaminated sediments may rise considerably the overall toxicity of PAH residues in exposed biota.     

Ammonium-nitrogen transformation and nitrogen retention in broiler manure supplemented with a soil amendment containing nitrifying bacteria

The effect of a soil amendment on ammonium nitrogen transformation and nitrogen retention in broiler manure was evaluated. Prior to incubation, broiler manure was mixed with autoclaved soil or non-autoclaved soil in different ratios to make 1 kg mixtures; broiler manure:non-autoclaved soil=9:1, 5:5, and 1:9 or broiler manure:autoclaved soil=9:1, 5:5, and 1:9. The non-autoclaved soil treatment reduced either numerically or significantly NH(4)(+)-N concentration compared to the autoclaved soil treatment during the 8-wk incubation. Total-N concentration of the non-autoclaved soil treatments was lower than the autoclaved soil treatments from 4 to 8 wk. The lowest manure to non-autoclaved soil treatment (M:S=1:9) had considerably more nitrite and nitrate; however, the higher ratio manure to non-autoclaved soil treatments (M:S=9:1 and 5:5) had slightly higher total nitrite and nitrate levels compared to the same ratio of autoclaved soil treatments. The moisture level of the 9:1, 5:5, and 1:9 M:S treatments were approximately 70, 45, and 30%, respectively. The results indicated that nitrifying bacteria in the non-autoclaved soil reduced the ammonium nitrogen concentrations of poultry manure by converting NH(3) or NH(4)(+) to NO(2)(-) or NO(3)(-). However, the higher moisture levels in treatments with greater manure to soil ratios (M:S=9:1 and 5:5) created anaerobic conditions that allowed for denitrification and greater N losses.     

Oil spill in the Rio de la Plata estuary, Argentina: 1. Biogeochemical assessment of waters, sediments, soils and biota

Aliphatic (ALI) and aromatic (ARO) hydrocarbon concentrations, composition and sources were evaluated in waters, sediments, soils and biota to assess the impact of approximately 1000 tons of oil spilled in Rio de la Plata coastal waters. Total ALI levels ranged from 0.4-262 microg/l in waters, 0.01-87 microg/g in sediments, 5-39 microg/g in bivalves, 12-323 microg/g in macrophytes to 948-5187 microg/g in soils. ARO varied from non-detected 10 microg/l, 0.01-1.3 mug/g, 1.0-16 microg/g, 0.5-6.9 microg/g to 22-67 microg/g, respectively. Offshore (1, 5, 15 km) waters and sediments were little affected and contained low background hydrocarbon levels reflecting an effective wind-driven transport of the slick to the coast. Six months after the spill, coastal waters, sediments, soils and biota still presented very high levels exceeding baseline concentrations by 1-3 orders of magnitude. UCM/resolved aliphatic ratio showed a clear trend of increasing decay: coastal waters (3.3) < macrophytes (6.7) < soils (9.4) < offshore sediments (13) < coastal sediments (17) < clams (52). All environmental compartments consistently indicated that the most impacted area was the central sector close to Magdalena city, specially low-energy stream embouchures and bays which acted as efficient oil traps. The evaluation of hydrocarbon composition by principal component analysis indicated the predominance of biogenic (algae, vascular plant cuticular waxes), background anthropic, pyrogenic and diagenetic hydrocarbons, offshore and in non-impacted coastal sites. In contrast, polluted stations presented petrogenic signatures characterized by the abundance of isoprenoids, low molecular weight n-alkanes and methylated aromatics in different stages of alteration. The petrogenic/biogenic ratio ( n-C23) and petrogenic/pyrogenic relationship (methylated/unsubstitued PAH) discriminated the samples according to the different degree of impact. The following paper present the results of the study of the progress of hydrocarbon disappearance in sediments and soils 13 and 42 months after the spill.     

Lead and zinc in sediments and biota from Maarmorilik, West Greenland: an assessment of the environmental impact of mining wastes on an Arctic fjord system

Lead and zinc levels in sediments and biota from the fjord system surrounding the lead/zinc mine at Maarmorilik, West Greenland, were investigated to evaluate the impact of waste rock and marine-deposited tailings on the marine biota. Concentrations of metal in the sediment were up to 8,922 +/- 622 microg g(-1) (dry wt.) for lead and 19,351+/- 476 microg g(-1) (dry wt.) for zinc. Levels of lead and zinc were also elevated in a suite of monitor organisms. The feeding modes of the organisms were used to explain the sources of metals to the organisms. After closure of the mine, the concentrations of metals in the upper centimetres of the sediments decreased, and a decreased impact of metals on the brown alga Fucus distichus was observed. However, the metals in the sediments still affect the marine biota in the area.     

Rainwater chemistry at the summit and southern flank of the Itatiaia massif, Southeastern Brazil

Wet deposition and related rainwater chemistry were studied at the Itatiaia massif, on which is settled the Itatiaia National Park (INP). Samples were simultaneously collected on a weekly basis over 12 months, using automated wet and dry samplers, at the INP-Headquarters (INP-Hq; altitude=820 m) and the Itatiaia Plateau (It-Pt; altitude=2460 m). Conductivity, pH, Na(+), K(+), Mg(2+), Ca(2+), NH(4)(+), Cl(-), NO(3)(-) and SO(4)(2-) were determined in 36 rainwater samples. Volume-weighted mean (VWM) pH was lower at the INP-Hq (4.9) than at the It-Pt (5.3). Very strong correlation between Cl(-) and Na(+) was found for the INP-Hq (r=0.99). At the Itatiaia massif, SO(4)(2-), NO(3)(-), and NH(4)(+) comprised together about 60% of the total inorganic ions and appear to exert the major control on rainwater pH.     

Tin compounds in sediments of Lake Maryut, Egypt

Concentrations of inorganic, methyl- and butyltin compounds were quantified by a hydride derivatization/atomic absorption technique for eleven short sediment cores sampled from Lake Maryut, Alexandria, Egypt. All samples contained inorganic Sn concentrations ranging from 1875 to 8190 ng g(-1) dw, the highest levels occurring in the eastern portion of the lake. Methyltin concentrations were also highest in the eastern lake, decreasing considerably in the western lake. Mono- and dimethyltins were found at all sites, the former species being the highest in concentration. Trimethyltin was much lower than either, and was absent from four out of 11 sites. An opposite trend was observed for the butyltin species, their concentration being highest in the west lake, decreasing eastward. Mono- and dibutyltin were almost equal in concentration. Although tributyltin was absent from one site in the lake, it was much higher in concentration than the two other species, particularly in the western lake. In general, methyl- and butyltin concentrations decreased with depth in the cores. Methyltin compounds appear to form within the lake mainly by methylation of inorganic Sn, and butyltin compounds are derived from anthropogenic sources. No significant correlations were found between organic C and concentrations of methyltin species. A significant negative correlation was found between total butyltin concentrations and organic C in surficial sediments.     

Presence of alkyllead in rural and urban air: Evaluation of some sources of alkyllead pollution of the atmosphere in Norway

Concentrations of alkyllead in ambient air were measured, as well as in car exhaust and in gasoline vapours. In Oslo the concentration in air ranged from 0.010 to 0.100 μg Pb m⁻³, and these values were compared to the concentrations (< 0.001 μg Pb m⁻³) measured in a low traffic rural area of Norway. The amount of alkyllead in car exhaust varied between 0.1 and 15 μg Pb m⁻³, which was between 0.01 and 0.5% of the amount of inorganic lead in exhaust. Evaporation of alkyllead from parked cars was estimated at 0.5 mg Pb per day per car. The concentrations of alkyllead in saturated gasoline vapour were found to be 10–20 mg Pb m⁻³ at ambient air temperatures.     

Can we predict uranium bioavailability based on soil parameters? Part 2: soil solution uranium concentration is not a good bioavailability index

The present study aimed to quantify the influence of soil parameters on uranium uptake by ryegrass. Ryegrass was established on eighteen distinct soils, spiked with (238)U. Uranium soil-to-plant transfer factors (TF) ranged from 0.0003 to 0.0340kgkg(-1). There was no significant relation between the U soil-to-plant transfer (or total U uptake or flux) and the uranium concentration in the soil solution or any other soil factor measured, nor with the U recovered following selective soil extractions. Multiple linear regression analysis resulted in a significant though complex model explaining up to 99% of variation in TF. The influence of uranium speciation on uranium uptake observed was featured: UO(2)(+2), uranyl carbonate complexes and UO(2)PO(4)(-) seem the U species being preferentially taken up by the roots and transferred to the shoots. Improved correlations were obtained when relating the uranium TF with the summed soil solution concentrations of mentioned uranium species.     

Effect of immobilized microalgal bead concentrations on wastewater nutrient removal

A unicellular green microalga, Chlorella vulgaris, entrapped in calcium alginate as algal beads were employed to remove nutrients (N and P) from simulated settled domestic wastewater. A significantly higher nutrient reduction was found in bioreactors containing algal beads (at concentrations ranging from 4 to 20 beads ml(-1) wastewater) than the blank alginate beads (without algae). A complete removal of NH(4)(+)-N and around 95% reduction of PO(4)(3-)-P was achieved within 24 h of treatment in bioreactors having the optimal algal bead concentration (12 beads ml(-1), equivalent to 1:3 algal beads:wastewater, v/v). The NH(4)(+)-N removal was significantly lower at low (around 4 beads ml(-1)) and high (>15 beads ml(-1)) algal bead concentrations. On the other hand, the effect of bead concentration on phosphate removal was less obvious, and bead concentrations ranging from 8 to 20 beads ml(-1) showed comparable percentages of phosphate reduction. Algal uptake and adsorption on alginate gels were found to be the major processes involved in the removal of N and phosphate in the present study. In addition, NH(4)(+)-N could be lost via ammonia volatilization while PO(4)(3-)-P was removed by chemical precipitation, as alkaline pH was recorded in the immobilized microalgal treatment system.     

Factors affecting the organochlorine pollutant load in biota of a rice field ecosystem (Ebro Delta, NE Spain)

The concentrations of PCBs, DDTs, HCHs, HCB and OCS were determined in sediments and associated biota, both invertebrates (Physella acuta, Hirudo medicinalis, chironomid larvae, Hydrous pistaceus, Helochares lividus) and vertebrates (Rana perezi), in a temporary aquatic system, a rice field in the Ebro Delta (NE Spain). The qualitative and quantitative distribution of organochlorine compounds in sediments and aquatic biota has been explained by two mechanisms: equilibrium partitioning and/or biomagnification through the trophic web. Nevertheless, bioaccumulation processes are by far more complex, since several biotic and abiotic factors contribute to the observed pollutant loads in the organisms. In this respect, the biological characteristics of the organisms considered (e.g. species, age, lipid contents, feeding habits, etc.), as well as ecological factors (e.g. the habitat of the species and vertical distribution), have been shown to account for the organochlorine levels observed.     

Chlorinated hydrocarbon contaminants in Hong Kong surficial sediments.

Twenty surficial sediments were sampled from nearshore Hong Kong waters during 1997-1998, and analyzed for a range of chlorinated pesticides and polychlorinated biphenyls (PCBs). Results showed that concentrations (on a dry weight basis) of total HCHs were in the range 0.1-16.7 ng g-1, and total DDTs 0.3-14.8 ng g-1. PCBs, measured as an Aroclor 1242, 1248, 1254, 1260 (1:1:1:1) mixture, were found to be in a range of 0.5-97.9 ng g-1, and were at highest concentrations in Victoria Harbour. Results indicated that chlorinated pesticides and PCBs in Hong Kong nearshore sediments were most likely derived from waste discharge from a variety of sources, including agricultural, sewage, industrial waste disposal and shipping-related activities. In addition, as the north and west sides of Hong Kong are subject to influence from the Pearl River (due mainly to agricultural activities in the Pearl River Delta, and to a lesser extent developments around the Shenzhen Special Economic Zone), these inputs are also thought to be likely sources of contamination.