The major objectives of the study were to test the hypothesis of the Zarrin-Gol River as a reference site for ecotoxicological studies and to assess the contamination degree of heavy metals and metalloids in the river using four contamination indices. For these purposes, eleven heavy metal and metalloid concentrations were analyzed. The average concentrations (mgkg−1) in the sediments were: 37.67 (chromium) 286.28 (manganese), 13,751.04 (iron), 8.79 (cobalt), 12.39 (nickel), 32.68 (zinc), 21.91 (arsenic), 40.59 (selenium), 2923.86 (aluminum), ND (silver) and 785.96 (magnesium). Contamination factor, enrichment factor, pollution load index, and geoaccumulation index were calculated to evaluate the contamination degree and influence of human activities on heavy metal levels. The contamination indices of the sediment samples showed that arsenic and selenium were the highest pollutants. The results indicated that the Zarrin-Gol River could not be used as a reference site at least for arsenic and selenium.

In this study, the concentration and sources of aliphatic and petroleum markers were investigated in 105 samples of Anzali, Rezvanshahr and Astara cores from the southwest of Caspian Sea. Petroleum importation was diagnosed as a main source in most depths of cores by the results of unresolved complex mixture, carbon preference index and hopanes and steranes. From the chemical diagnostic parameters, petroleum inputs in sediment of cores were determined to be different during years and the sources of hydrocarbons in some sections differed than Anzali and Turkmenistan and Azerbaijan oils. Diagenic ratios in most sediments of upper and middle sections in Astara core were determined to be highly similar to those of Azerbaijan oil, while the presence of Turkmenistan and Anzali oils were detected in a few sections of Anzali and Rezvanshahr cores and only five layers of downer section in Anzali core, respectively.

A weak acid extraction was used to mobilize the loosely bound metals in estuary sediment samples. More than 30% of Ag, As, Ca, Cd, Co, Cu, Hg, Mn Ni, Pb and Zn were leached from the sediment showing that these metals are significantly present in the bioavailable form. PCA/APCS identified three sources of the metals, namely: lithogenic accounting for 72%, shipping related contributing 15% and traffic related representing 13% of the total load. Application of pollution index (PI) and modified pollution index (MPI) revealed that the sediment range from unpolluted to heavily polluted while ecological risk index (RI) classifies the sediment as posing low ecological risk modified ecological risk index (MRI) suggests considerable to very high ecological risk. To provide holistic insights into the ecological risks posed by metals, enrichment factor, MPI and MRI are recommended for the assessment of sediment in complex environments such as estuaries.

PURPOSE OF REVIEW: Mangroves are under increasing heavy metal (HM) pollution pressure from human activities because of the rapid industrialization and urbanization in coastal areas. Field and laboratory experiments showed that the tolerance of mangrove plants to HM stress is normally a mixture of metal avoidance and scavenging of reactive oxygen species (ROS). In this review, related studies during the past few decades on the accumulation and tolerance of mangrove to HMs have been synthesized. RECENT FINDINGS: In mangroves, metal accumulation mainly occurred at the root level with restricted transport to the aerial portions of the plant. The common founded HMs, such as copper, zinc, cadmium, chromium, and mercury, generally showed high bioconcentration factor in roots, while the concentration factors for these metals in leaves were usually much lower than one. The limited translocation of the toxic metals to the aerial parts renders the mangrove plants a high endurance ability to high levels of HM stress. To protect the cellular components from oxidative damage by HMs, mangroves have developed both enzymatic and nonenzymatic antioxidant mechanisms to scavenge the ROS. In some circumstances, the changes of antioxidative enzyme activity were usually in accordance with the changes of toxic metal concentrations in plant tissues. However, the responses of antioxidative enzymes in mangroves to HM stress varied with plant species, metal type, and concentration, as well as the duration of the treatment time. More toxicity tests are needed with early life stages of mangroves to determine threshold effect concentrations under more realistic conditions.

We examined hepatic concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), manganese (Mn), mercury (Hg), rubidium (Rb), selenium (Se) and zinc (Zn) in 10 breeding female common eiders (Somateria mollissima) from each of three colonies across 20° of latitude. Levels of many elements were elevated in eiders, although generally below levels of toxicological concern. We found significant differences in concentrations of As, Rb, Hg, Mn and Se among colonies, but not in a consistent pattern with latitude, and Hg:Se molar ratios did not vary among colonies. Furthermore, overlap in element concentrations from birds at different colonies meant that we could not reliably differentiate birds from different colonies based on a suite of their hepatic trace element concentrations. We encourage other researchers to assess baseline trace element levels on this important, harvested species, as a means of tracking contamination of nearshore benthic environments in the circumpolar Arctic.

The Arabian Gulf is a semi-enclosed water body that has witnessed accelerated anthropogenic activity, in terms of commissioning of nuclear power plants, desalination facilities, oil refineries and extensive coastal development. Furthermore, three wars during the past three decades is a potential worry. This study presents the first plutonium baseline in seawater from the Northern Arabian Gulf. The 239+240Pu concentrations in seawater vary, between 2.9 and 4.9mBqm−3, a range that is comparable to other water masses at this latitude. The 238Pu ranged between 0.04 and 0.05mBqm−3 and the 137Cs concentration between 1.04 and 1.18Bqm−3. The ratio of 238Pu/239+240Pu at all eight sampling stations was 0.01, while the ratio of 239+240Pu/137Cs varied between 0.01 and 0.02. The presence of 137Cs and 239+240Pu in seawater from this region can mainly be attributed to the global atmospheric deposition and fluvial transport. The seawater concentration of 239+240Pu is five order of magnitude lower than bottom sediments in the area.

Membrane photocatalytic ozonization coupled with wet absorption offers potential for elemental mercury (Hg0) removal. This study reports on a novel FeTiO2-coated polyvinylidene fluoride (PVDF) wet photocatalytic membrane reactor (WPCMR) for mercury removal in flue gas. Hg0 removal efficiency in the WPCMR reached up to 93.3%. Ozone could enhance mercury oxidation in WPCMR. Wet absorption helps to increases mercury removal efficiency. FeTiO2 catalyst was synthesized by sol-gel method and characterized by XRD, FTIR, UV–Vis, XPS and SEM. XPS analysis confirmed Hg0 oxidation to divalent mercury (Hg (II)). Elemental mercury was oxidized to mercuric oxide followed by wet absorption in the presence of OH free radical and ozone. Wet photocatalytic membrane reactor and photocatalytic membrane reactor (PCMR) of elemental mercury reaction with the FeTiO2/PVDF catalyst all follow Langmuir-Hinshelwood kinetics.

Three one-off burial treatments were designed in intertidal zone of the Yellow River estuary to determine the effects of sediment burial on decomposition and heavy metal levels of Suaeda salsa. Sediment burial showed significant effect on decomposition rate of S. salsa. With increasing burial depth, Cu, Zn, Cd and Co levels generally increased, while Cr and Mn levels decreased. Except for Zn, Mn, Cd and Co, stocks of Pb, Cr, Cu, Ni and V in S. salsa among burials were greatly different. The S. salsa in three burials was particular efficient in binding V and Co and releasing Pb, Zn and Cd, and, with increasing burial depth, stocks of Cr, Cu, Ni and Mn shifted from accumulation to release. In future, the eco-toxic risk of Pb, Cr, Cu, Zn, Ni, Mn and Cd exposure might be serious as the strong burial episodes occurred in S. salsa marsh.

Aliphatic hydrocarbons (AHs), biomarker and polycyclic aromatic hydrocarbons (PAHs) concentrations of surface water and sediment samples collected from Yellow River Estuary and adjacent coastal area in China were measured to determine their spatial distributions, analyze their sources and evaluate the ecological risk of PAHs in the water–sediment system. The spatial distributions of n-alkane in sediments are mainly controlled by the mixing inputs of terrigenous and marine components. In comparison with AHs, the total concentrations of Σ16PAHs in surface sediments from a transect of the offshore area were noticeably higher than that of the riverine and estuary areas. Additionally, the AHs and total PAHs concentrations all indicated an overall pattern of a seaward decrease. The PAHs concentrations during the dry season (mainly in the form of dissolved phase) were higher than that of PAHs (mainly dissolved phase and particulate phase form) in the flooding season. In comparison with global concentration levels of PAHs, the level of PAHs in suspended particulate matter and sediments from the Yellow River Estuary was lower than those from other countries, while the concentration of PAHs in the dissolved phase were in the middle range. Petroleum contamination, mainly from oil exploration and discharge of pollutants from rivers, was the main source of n-alkanes. The PAHs in the river were mostly of petrogenic origin, while those in the estuarial and marine areas originated mainly from pyrogenic sources. The results of the toxicology assessment suggested that the PAHs in sediments from Yellow River Estuary and adjacent coastal area exhibited a low potential eco-toxicological contamination level.