Fate of DDT-related compounds in Bohai Bay and its adjacent Haihe Basin, North China

Concentrations of ten DDTs (2,2-bis-(chlorophenyl)-1,1,1-trichloroethane) of which p,p'-DDA (2,2-bis(chlorophenyl)acetic acid), p,p'-DDM (bis(chlorophenyl)methane) and p,p'-DBP (dichlorobenzophenone) are often neglected, were measured in 25 water and 25 sedimentary samples from Bohai Bay and its adjacent Haihe Basin. The ratio of o,p'-DDX/p,p'-DDX in the upper reaches of Yongdingxin River ranged from 0.71 to 2.44, suggesting that the potential source of pollution would be the manufacturing or use of dicofol near this river. While DDA accounted for 52-93% of the SigmaDDT concentration in water, DDA was only detected in three sedimentary samples. And DDM was found to be an important degradation product of DDT in water following DDA. It should be noted that DBP (0.60-3.30 ng/g) is a major metabolite comparable with DDE (2,2-bis(chlorophenyl)-1,1-dichloroethylene, nondetectable-1.80 ng/g) and DDD (2,2-bis-(chlorophenyl)-1,1-dichloroethane, nondetectable-2.86 ng/g) in sediment in Bohai Bay. Finally, the SigmaDDT concentration in sedimentary sample from Bohai Bay was found to be dependent on the TOC (total organic carbon) value.     

Spatial and vertical distribution of organochlorine pesticides in sediments from Daya Bay, South China

The spatial and vertical distribution of organochlorine pesticides (OCPs) has been investigated in Daya Bay, China. The concentration of total OCPs in surface sediment range from 16.66 to 44.04ng/g dry weight with a mean concentration of 26.60ng/g. DDTs and HCHs were the predominant species. The ratios of (DDD+DDE)/DDT reflected a cocktail input pattern of fresh and weathered DDTs. The predominant alpha-HCH and the alpha/beta-HCH ratios indicated that the technical HCH contamination was mainly due to historical usage, although there was fresh input of lindane. The variation profiles of concentrations showed that OCPs were extensively applied between the late 1950s and early 1980s in China. A recent increasing trend in concentrations of DDTs and HCHs was found in both cores. The increasing ratios of (DDE+DDD)/DDT with corresponding decreases of DDE/DDT ratio implied that most of the DDTs deposited after their production ban were more likely "weathered" DDTs derived from soil residues.     

Assessment of the distribution and risks of organochlorine pesticides in core sediments from areas of different human activity on Lake Baiyangdian,China

Burial characteristics and risks associated with 13 organochlorine pesticides (OCPs; α-HCH, β-HCH, γ-HCH, δ-HCH, p,p′-DDE, p,p′-DDD, p,p′-DDT, heptachlor, aldrin, dieldrin, endrin, α-endosulfan and β-endosulfan) in core sediments of Lake Baiyangdian were investigated. The core sediments were taken from areas of different anthropogenic activity along the lake. Concentrations of hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT), heptachlor, aldrin, and endosulfan ranged from 0.64 to 2.72, nd (undetectable levels) to 2.79, 0.29 to 1.37, nd to 2.62, and nd to 1.76 ng g^?1, respectively. Concentrations of OCPs in the core sediments exhibited the following spatial trend: Dongtianzhuang > Shaochedian > Zaolinzhuang. Concentrations in the surficial layer were also found to be greater than those in the bottom layer. OCPs were dominated by HCH. β-HCH was found in the greatest concentrations, indicating that the majority of HCH came from older inputs to the area. The ratio of DDT and its metabolites (DDD and DDE) also suggested a lack of recent inputs to the lake environment. The residues of heptachlor, aldrin, and endosulfan in core sediments indicated that cyclodienes were historically applied in the area. The OCP risk assessment, which was based on effect range low and threshold effect level values, suggested that the top layer of sediment in Dongtianzhuang cores had a relatively high toxicity to human health and the environment.     

Levels and profiles of PCBs and OCPs in marine benthic species from the Belgian North Sea and the Western Scheldt Estuary

Various benthic invertebrates (flying crab, common shrimp, and red starfish), small fish (sand goby), benthic flatfish (dab, plaice, and sole) and gadoids (bib and whiting) were collected in the Belgian North Sea and along the Scheldt Estuary, both representing areas impacted by various contaminants to different degrees. The levels of 25 polychlorinated biphenyls (PCBs) and 15 organochlorine pesticides (OCPs), which included penta- and hexachlorobenzene, alpha-, beta-, and gamma-hexachlorocyclohexane isomers, chlordanes, and DDT and metabolites, were determined. Sum of PCBs and OCPs in benthic invertebrates and goby ranged from 1.5 to 280 ng/g wet weight (ww) and from 0.27 to 23 ng/g ww, respectively. The fish livers revealed total PCB and OCP levels ranging from 20 to 3200 ng/g ww and from 6.0 to 410 ng/g ww, respectively. Levels of both contaminant groups were significantly higher in samples from the Scheldt Estuary compared to the Belgian North Sea. For most species a highly inverse correlation was found between the concentration of contaminants and the distance to Antwerp (r between 0.812 and 0.901, p < 0.05), pointing to a higher degree of exposure further upstream. PCB and OCP exposures are highly correlated (r between 0.836 and 1.000, p < 0.05), which suggests that the pollution can be classified as historical. However, because urban and industrial centres may still be emitting these compounds, more recent point and non-point sources cannot be ruled out.     

Modelling and experimental study of coupled exchange of p,p′‐DDE and colloids in a flume simulated stream–streambed system

Stream–subsurface exchange plays a significant role in the fate and transport of contaminants in streams. It has been modelled explicitly by considering fundamental processes such as hydraulic exchange, colloid filtration, and contaminant interactions with streambed sediments and colloids. The models have been successfully applied to simulate the transport of inorganic metals and nutrients. In this study, laboratory experiments were conducted in a recirculating flume to investigate the exchange of a hydrophobic organic contaminant, p,p′‐dichloro‐diphenyl‐dichloroethane (DDE), between a stream and a quartz sand bed. A previously developed process‐based multiphase exchange model was modified by accounting for the p,p′‐DDE kinetic adsorption to and desorption from the bed sediments/colloids and was applied to interpret the experimental results. Model input parameters were obtained by conducting independent small‐scale batch experiments. Results indicate that the immobilization of p,p′‐DDE in the quartz sand bed can occur under representative natural stream conditions. The observed p,p′‐DDE exchange was successfully simulated by the process‐based model. The model sensitivity analysis results show that the exchange of p,p′‐DDE can be sensitive to either the sediment sorption/desorption parameters or colloidal parameters depending on the experimental conditions tested. For the experimental conditions employed here, the effect of colloids on contaminant transport is expected to be minimal, and the stream–subsurface exchange of p,p′‐DDE is dominated by the interaction of p,p′‐DDE with bed sediment. The work presented here contributes to a better mechanistic understanding of the complex transport process that hydrophobic organic contaminants undergo in natural streams and to the development of reliable, predictive models for the assessment of impacted streams. Copyright © 2015 John Wiley & Sons, Ltd.     

Levels and distribution of organochlorine pesticides and hexachlorobutadiene in soils and terrestrial organisms from a former pesticide-producing area in Southwest China

The contamination of organochlorine pesticides (OCPs) and hexachlorobutadiene (HCBD) in soils, plants, and terrestrial fauna from a former pesticide-producing area in Southwest China was investigated. High levels of OCP residues (ΣHCHs and ΣDDTs of 3.89–13,386 and 23.3–11,186 ng g^?1 dw, respectively) were found in the soils within the producing factory, indicating that the former pesticide factory brownfield site poses a high environment risk and that effective soil remediation is needed. The OCP concentrations in soils surrounding the pesticide factory were 1–2 orders of magnitude higher than in the other agricultural areas from China. Grass, vegetables, and tree leaves from the surrounding areas of the point source showed moderate OCP pollution, which was likely to be causing potential negative impacts on terrestrial ecosystem. OCP levels in terrestrial species from the studied area including insects, free-range chickens and birds were moderate, and were generally within accepted safe levels. β-HCH was the most prevalent isomer, implying that hexachlorocyclohexane (HCH) residues were mainly derived from the degradation of technical HCH. The dichlorodiphenyltrichloroethane (DDT) profiles reflected obvious degradation of technical DDT. In the study area, the concentrations of HCBD were <0.02–5.59, 0.03–24.6 ng g^?1 dw and 1.65–3.80 ng g^?1 lw in soils, plants, and animals, respectively, which were relatively low and not sufficient to cause observable adverse biological effects.     

Root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate

The root‐zone moisture replenishment mechanisms are key unknowns required to understand soil hydrological processes and water sources used by plants. Temporal patterns of root‐zone moisture replenishment reflect wetting events that contribute to plant growth and survival and to catchment water yield. In this study, stable oxygen and hydrogen isotopes of twigs and throughfall were continuously monitored to characterize the seasonal variations of the root‐zone moisture replenishment in a native vegetated catchment under Mediterranean climate in South Australia. The two studied hillslopes (the north‐facing slope [NFS] and the south‐facing slope [SFS]) had different environmental conditions with opposite aspects. The twig and throughfall samples were collected every ~20 days over 1 year on both hillslopes. The root‐zone moisture replenishment, defined as percentage of newly replenished root‐zone moisture as a complement to antecedent moisture for plant use, calculated by an isotope balance model, was about zero (±25% for the NFS and ± 15% for the SFS) at the end of the wet season (October), increased to almost 100% (±26% for the NFS and ± 29% for the SFS) after the dry season (April and May), then decreased close to zero (±24% for the NFS and ± 28% for the SFS) in the middle of the following wet season (August). This seasonal pattern of root‐zone moisture replenishment suggests that the very first rainfall events of the wet season were significant for soil moisture replenishment and supported the plants over wet and subsequent dry seasons, and that NFS completed replenishment over a longer time than SFS in the wet season and depleted the root zone moisture quicker in the dry season. The stable oxygen isotope composition of the intraevent samples and twigs further confirms that rain water in the late wet season contributed little to root‐zone moisture. This study highlights the significant role of the very first rain events in the early wet season for ecosystem and provides insights to understanding ecohydrological separation, catchment water yield, and vegetation response to climate changes.     

Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in harbor sediments from Sea Lots, Port-of-Spain, Trinidad and Tobago

Concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in nearshore marine surficial sediments from three locations in Trinidad. Sediments were sampled at Sea Lots on the west coast, in south Port-of-Spain Harbor, south of Sea Lots at Caroni Lagoon National Park, and on Trinidad’s east coast at Manzanilla. Total PCB concentrations in Sea Lots sediments ranged from 62 to 601 ng/g (dry weight {dw}), which was higher than at Caroni and Manzanilla, 13 and 8 ng/g dw, respectively. Total OCP concentrations at Sea Lots were ranged from 44.5 to 145 ng/g dw, compared with 13.1 and 23.8 n/g (dw), for Caroni and Manzanilla respectively. The concentrations of PCBs and of some OCPs in sediments from Sea Lots were above the Canadian interim sediment quality guidelines. To date, this data is the first report on the levels of PCBs and other organochlorine compounds from Trinidad and Tobago.     

Persistent Organic Pollutants (POPs) in Bottom Sediments of the Vistula River,Poland

The Vistula (Wisla) river, the biggest river in Poland, is 1038 km long and has a drainage area of 168 689 km². The river is strongly polluted by wastewaters. Big industrial plants are situated mainly in the upper part of the river, where it is slow‐flowing. This paper presents the results of the analysis of bottom sediment samples gathered from different locations along the Vistula river, from Kraków to Gdansk. The study was conducted in 2005. The following parameters were determined: chloroorganic pesticides, polychlorinated biphenyls (PCBs), chlorophenols, polycyclic aromatic hydrocarbons (PAHs), total organic carbon (TOC). The sum of chloroorganic pesticides was in the range of 2.0 to 77.5 ng/g d.w. (dry wet) with the highest values in the upper part of the river. p,p′‐DDT was found in the highest concentration. The sum of PCBs was in the range of 0.9 to 64.2 ng/g d.w. The sum of chlorophenols varied from 0.48 to 14.3 ng/g d.w. 2,4‐Dichlorophenol and pentachlorophenol occurred in the highest concentration. The sum of PAHs was in the range of 1552 to 7832 ng/g d.w. Phenantren was found in the highest concentration and antracen in the lowest. TOC values varied from 4.3 to 43.9 g/kg d.w. The concentrations of pesticides and PCBs were the highest in the upper part of the river and decreased along the course of the river, but the other determined compounds did not show this trend. However, the highest values occurred always in the upper part of the river.     

Composition and distribution of organochlorine pesticide residues in surface sediments from the Wu-Shi River Estuary,Taiwan

The contamination of organochlorine pesticides (OCPs) in sediments from the Wu-Shi River estuary was investigated to evaluate the pollution potentials and distribution of OCPs in central Taiwan. A total of 19 sediment samples were collected at five sampling stations along the River estuary. The concentrations of OCPs were in the range of 0.99–14.5 ng/g-dry weight (dw) for ΣHCH (-, β-, γ-, δ-HCH), 0.46–13.4 ng/g-dw for Σcyclodiene and 0.53–11.4 ng/g-dw for ΣDDT (p,p^′-DDD, p,p^′-DDE, p,p^′-DDT). The mean concentrations of ΣHCH, Σcyclodiene and ΣDDT were 3.79, 4.87 and 2.51 ng/g-dw, respectively. The total concentrations of OCPs correspond to 1.73–71.9 μg/g-OC when normalized to TOC contents. Among the organochlorine pesticides, endosulfan sulfate, β-HCH, and p,p^′-DDD were the most dominant compounds in the sediments with the average concentrations of 1.97, 3.43 and 2.08 ng/g, respectively. Also, different contamination patterns among sampling seasons were observed. The measured concentrations of OCPs collected in spring were higher than those in autumn and winter. A linear relationship between sediment characteristics and OCP residues was also demonstrated. The results obtained in this study show that there still exist a variety of organochlorine pesticide residues in the sediments from the near shore of central Taiwan.     

POPs and their ecological risk in sewage sludge of waste water treatment plants in Beijing, China

The concentrations of three classes of persistent organic compounds (POPs) in the sewage sludge from 12 Beijing wastewater treatment plants (WWTPs) were investigated and their ecological risks were assessed. The concentrations of 15 polycyclic aromatic hydrocarbons (PAHs), 27 polychlorinated biphenyl congeners (PCBs) and 15 organochlorine pesticides (OCPs) in sewage sludge were measured using gas chromatography–tandem mass spectrometry (GC–MS/MS) technique. Total PAHs concentrations ranged from 445.1 to 3,586.4 ng g^?1 dry weight (dw), and the sum of the phenanthrene (Phe), anthracene (Ant), naphthalene (Nap), fluoranthene and chrysene accounted for 69.3–97.0 % of the total PAHs. The most abundant compounds present were 2-ring and 3-ring Ant, Phe and Nap, indicating a possible petrogenic source. Total PCBs concentrations were ranged between 3.2 and 21.8 ng g^?1 dw. Total OCPs concentrations ranged from 38.0 to 143.3 ng g^?1 dw, and the sum of total DDT, HCB and HCHs accounted for 69.6–97.7 % of the total OCPs. The levels of PAHs, PCBs and OCPs in this study were comparable to or lower than those reported in relatively WWTPs from other regions. In addition, they were also shown to have various distribution patterns, possibly due to their different wastewater sources. The 12 WWTPs may be classified into 4 groups because of their different sources of waste water based on cluster analysis. The ecological risk assessment shows that the concentrations of Ant or Fla at two sites, p,p′-DDE and ∑DDT at 83 % of the 12 sites may cause adverse ecological effects.     

PCBs and organochlorine pesticides in Hector’s (Cephalorhynchus hectori hectori) and Maui’s (Cephalorhynchus hectori maui) dolphins

Polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticide levels were determined in blubber samples collected from stranded and incidentally by-caught Hector’s (Cephalorhynchus hectori hectori) and Maui’s (Cephalorhynchus hectori maui) dolphins from New Zealand waters between 1997 and 2009. PCBs (45 congeners) and a range of OC pesticides including dieldrin, hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), along with its metabolites DDE and DDD were determined. OC pesticides dieldrin, p,p′-DDE, p,p′-DDD and p,p′-DDT were present at the highest concentrations. Sum DDT concentrations ranged from 93.7 to 8210 (Mean = 1358, S.D = 1974) and 252.4 to 57,390 (Mean = 12,389, S.D = 18,161) μg/kg wet weight in females and males, respectively. Similarly, Σ45CB concentrations ranged from 45.5 to 981.3 (Mean = 333.2, S.D = 265.8) and 60.5 to 5574 (Mean = 1833, S.D = 1659) μg/kg wet weight in females and males, respectively. The transfer of ΣDDTs and summed PCBs (both as ΣICES7CBs and Σ45CBs) between a pregnant female and her unborn fetus was calculated at 5.7% and 4.3%, respectively. As the fetus was close to term, this likely represents the degree of placental transfer. Concentrations of OC pesticides determined in the present study are higher than those previously reported for Hector’s dolphins. Sum DDT and DDE/ΣDDT levels calculated reveal New Zealand’s legacy of DDT usage, particularly off the east coast of the South Island.     

Levels of Organohalogenated Pollutants in Human Milk Samples from Konya City,Turkey

This study reports the levels of organochlorine pesticides (OCPs, α‐, β‐, γ‐ and Δ‐HCHs, p,p′‐DDE, p,p′‐DDD and p,p′‐DDT), polychlorinated biphenyls (PCBs, PCB 28, 52, 101, 153, 138 and 180 congeners) and polybrominated diphenyl ethers (PBDEs, PBDE 47, 99, 100, 153 and 154 congeners) in 45 individual human milk samples collected from Konya City, Turkey. Average concentrations of ΣHCHs, ΣDDTs, ΣPCBs and ΣPBDEs were 22.62, 37.10, 104.95 and 67.34 ng/g lipid wt., respectively. No significant differences in investigated pollutants were found between primiparous and multiparous mothers. There was no correlation between levels of each group of pollutants in human milk and the age of mothers. Moreover, there was no significant difference in the levels of ΣDDTs, between mothers who have eaten fish more than once a week and those who consumed fish less than once. An analysis of the infant exposure to DDTs, HCHs and PCBs via mother's milk indicated that the estimated daily intakes of these pollutants were below the guideline proposed by the World Health Organization (WHO) and the Health Canada which means that there is definitely no concern on children health.     

Variations in DDE percentage correlated with total DDT burden in the blubber of fin and sei whales

Total DDT burden and DDE percentage (DDE/DDT+TDE+DDE) in the blubber of fin and sei whales are highly correlated. Total DDT concentration may be an important source of variation for the DDE percentage detected in different individuals of the same population. Such a positive correlation is explained by the intensification of the dehydrochlorinative and differential excretive functions at higher pollutant levels. In the past, variations in the DDE percentage have been attributed to differences in the chronology of DDT input into the ecosystem and assumed to be indicators of population discreteness or changes in the pattern of DDT exposure of a given population. However, changes in the DDE percentage as related to total DDT burden may be important within the observed normal ranges of variation of total DDT residue levels caused by age and sex composition of the population. Therefore, the DDE percentage may be reliably used only when full control of the life history parameters of the sample is achieved and when strict homogeneity among the samples to be compared has been proved.     

Monitoring pesticides in the Great Barrier Reef

Pesticide runoff from agriculture poses a threat to water quality in the world heritage listed Great Barrier Reef (GBR) and sensitive monitoring tools are needed to detect these pollutants. This study investigated the utility of passive samplers in this role through deployment during a wet and dry season at river mouths, two near-shore regions and an offshore region. The nearshore marine environment was shown to be contaminated with pesticides in both the dry and wet seasons (average water concentrations of 1.3-3.8 ng L⁻¹ and 2.2-6.4 ng L⁻¹, respectively), while no pesticides were detected further offshore. Continuous monitoring of two rivers over 13 months showed waters flowing to the GBR were contaminated with herbicides (diuron, atrazine, hexazinone) year round, with highest average concentrations present during summer (350 ng L⁻¹). The use of passive samplers has enabled identification of insecticides in GBR waters which have not been reported in the literature previously.     

Levels of organochlorine pesticide residues in some organs of the Ganges perch, Lates calcarifer, from the Ganges-Brahmaputra-Meghna Estuary, Bangladesh

Levels of organochlorine pesticide residues (p,p′ DDT, DDD, DDE, Aldrin, Dieldrin, Lindane, Heptachlor and BHC) were analysed in the dry and wet seasons in four organs (muscle, liver, gut and egg samples) of Ganges Perch, Lates calcarifer, collected during October–November–December, 1996 and May–June–July, 1997 from the Ganges–Brahmaputtra–Meghna estuary. The residues were analysed by using gas-chromatography (GC) in electron capture detector (ECD) mode and were verified by thin layer chromatography (TLC). Among the four organs analysed, the residues were found in the order egg > gut > muscle > liver. The pesticide residues were found in the order ∑DDT > Heptachlor >Dieldrin > Aldrin. Higher levels of residues were found during the dry season due to high lipid content in fishes. A positive correlation was observed between the pesticide residues (∑DDT and ∑OCs) and lipid contents of fish, and the correlation was found to be linear. The concentrations of pesticide residues in muscle, liver and gut were below the FAO/WHO (1993) recommended permissible limit except in eggs.     

Levels of Organochlorine Pesticide Residues in Some Organs of the Ganges Perch, Lates calcarifer, from the Ganges–Brahmaputra–Meghna Estuary, Bangladesh

Levels of organochlorine pesticide residues (p,p′ DDT, DDD, DDE, Aldrin, Dieldrin, Lindane, Heptachlor and BHC) were analysed in the dry and wet seasons in four organs (muscle, liver, gut and egg samples) of Ganges Perch, Lates calcarifer, collected during October–November–December, 1996 and May–June–July, 1997 from the Ganges–Brahmaputtra–Meghna estuary. The residues were analysed by using gas-chromatography (GC) in electron capture detector (ECD) mode and were verified by thin layer chromatography (TLC). Among the four organs analysed, the residues were found in the order egg > gut > muscle > liver. The pesticide residues were found in the order ∑DDT > Heptachlor >Dieldrin > Aldrin. Higher levels of residues were found during the dry season due to high lipid content in fishes. A positive correlation was observed between the pesticide residues (∑DDT and ∑OCs) and lipid contents of fish, and the correlation was found to be linear. The concentrations of pesticide residues in muscle, liver and gut were below the FAO/WHO (1993) recommended permissible limit except in eggs.     

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides in water columns from the Pearl River and the Macao harbor in the Pearl River Delta in South China

Polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) were measured in suspended particles and dissolved phase from the Baiertang water column and the Macao water column samples as collected from the Guangzhou channel of the Pearl River and the Macao harbor, where the sediments were heavily contaminated with organic pollutants. Total OCPs concentration varies from 23.4 to 61.7 ng/l in Baiertang water column and from 25.2 to 67.8 ng/l in Macao column, while total PAHs concentration varies from 987.1 to 2878.5 ng/l in the Baiertang water column and from 944.0 to 6654.6 ng/l in the Macao column. The vertical distribution profiles of pollutants and the partition of pollutants between particles and dissolved phases indicate that the sediments in Baiertang act as an important source of selected pollutants, and the pollutants in water of this region were mainly originated from the release and re-suspension of contaminants residing in the sediments. The sediments in Macao harbor act as a reservoir for organochlorine pesticides, such as DDTs mainly introduced by river inflow from Xijiang and PAHs input by brackish water from the Lingdingyang estuary. Combustion of fossil fuels and petroleum input are the main sources of PAHs in the Macao water column, while combustion of fossil fuels and coal is responsible for the PAHs in the Baiertang water column. The ratios of DDT/(DDD+DDE) for the Macao water column samples demonstrate that such chemicals were input into this region in recent times.     

Striped weakfish (Cynoscion guatucupa): a biomonitor of organochlorine pesticides in estuarine and near-coastal zones

The general goal of this study was to investigate the role of Cynoscion guatucupa as a biomonitor of organochlorine pesticides (OCP) contamination in Bahía Blanca estuary. Thus, we evaluated whether or not OCP fish distribution pattern reflects the OCP land sources, and if size-related bioaccumulation and biomagnification of these contaminants does occur by comparing different tissues of juvenile and adults of C. guatucupa (Cuvier, 1830). Size-related bioaccumulation in C. guatucupa was observed and it was more important for the more lipophilic and biomagnifying OCP, being determined over time by diet influence. Endosulfan sulfate, chlordanes, HCH isomers and DDT compounds predominated in tissues and ingested food of C. guatucupa, being alpha-chlordane, heptachlor and p,p'-DDE highly bioaccumulated and biomagnificated. Our findings also showed that male adults of C. guatucupa are biomonitors of OCP pollution so we propose this species for further investigations in other coastal zones of South America.     

Laboratory simulation of the salt weathering of schist: 1. Weathering of schist blocks in a seasonally wet tropical environment

Data describing sediment generation focusing on the temporal evolution of size gradation are required for the prediction of long‐term landform evolution. This paper presents such data for the salt weathering of a quartz‐chlorite schist obtained from the Ranger Uranium Mine in northern Australia. Rock fragment samples are subjected to three different climate regimes: (1) a dry season climate; (2) a wet season climate (both based on observations at the Ranger site); and (3) an oven‐drying sequence designed to test the sensitivity of the weathering process by exposing the rocks to more extreme temperatures. Two MgSO₄ salt solutions are applied, one being typical of wet season runoff and the other a more concentrated solution. Salt solution is applied daily in the wet season experiments and once only at the beginning of the dry season experiments. Results of the experiments reveal four stages of weathering. The kinetics of each stage are described and related to the formation of sediment of different sizes. Wet season climate conditions are shown to produce greater moisture variability and lead to faster weathering rates. However, salt concentrations in the wet season are typically lower and so when climate is combined with observed salt concentrations, the dry and wet season experiments weather at approximately equal rates. Finally, small variations in rock properties were shown to have a large impact on weathering rates, leading to the conclusion that rock weathering experiments need to be carefully designed if results are to be used to help predict weathering behaviour at the landscape scale. Copyright © 2006 John Wiley & Sons, Ltd.