Uptake and distribution of N, P and heavy metals in three dominant salt marsh macrophytes from Yangtze River estuary, China

Unveiling the nitrogen and phosphorus removal potential: Comparative analysis of three coastal wetland plant species in lab-scale constructed wetlands

It is well accepted that tidal wetland vegetation performs a significant amount of water filtration for wetlands. However, there is currently little information on how various wetland plants remove nitrogen (N) and phosphorus (P) and how they differ in their denitrification processes. This study compared and investigated the denitrification and phosphorus removal effects of three typical wetland plants in the Yangtze River estuary wetland (Phragmites australis, Spartina alterniflora, and Scirpus mariqueter), as well as their relevant mechanisms, using an experimental laboratory-scale horizontal subsurface flow constructed wetland (CW). The results showed that all treatment groups with plants significantly reduced N pollutants as compared to the control group without plants. In comparison to S. mariqueter (77.2-83.2%), S. alterniflora and P. australis had a similar total nitrogen (TN)removal effectiveness of nearly 95%. With a removal effectiveness of over 99% for ammonium nitrogen (NH4+-N), P. australis outperformed S. alterniflora (95.6-96.8%) and S. mariqueter (94.6-96.5%). The removal of nitrite nitrogen (NO2--N)and nitrate nitrogen (NO3--N)from wastewater was significantly enhanced by S. alterniflora compared to the other treatment groups. Across all treatment groups, the removal rate of PO43--P was greater than 95%. P. australis and S. alterniflora considerably enriched more 15N than S. mariqueter, according to the results of the 15N isotope labeling experiment. While the rhizosphere and bulk sediments of S. alterniflora were enriched with more simultaneous desulfurization-denitrification bacterial genera (such as Paracoccus, Sulfurovum, and Sulfurimonas), which have denitrification functions, the rhizosphere and bulk sediments of P. australis were enriched with more ammonia-oxidizing archaea and ammonia-oxidizing bacteria. As a result, compared to the other plants, P. australis and S. alterniflora demonstrate substantially more significant ability to remove NH4+-N and NO2--N/NO3--N from simulated domestic wastewater.

Health risk assessment of heavy metals in Coptodon zillii and Parachanna obscura from a tropical reservoir

In this study, the concentrations of trace metals were examined in commercially important fish, Coptodon zillii and Parachanna obscura from Osu reservoir. These were with a view to providing baseline information on the levels of heavy metals and its associated risks to human health through fish consumption. Fish samples were collected fortnightly for five months using fish traps and gill nets with the assistance of local fisherman. They were brought into the laboratory in an ice chest for identification. The fish samples were dissected and the gills, fillet and liver kept in freezer and later analyzed for heavy metals based on Atomic Absorption Spectrophotometric (AAS) method. The data collected were subjected to appropriate statistical software packages. The results revealed that the concentration of the heavy metals in P. obscura and C. zillii across the tissues were not significantly different (p > 0.05) from each other. Also, the mean concentration of heavy metals in the fish were below the recommended limits of FAO and WHO. The target hazard quotient (THQ) for each heavy metals were below one (1) while the estimated hazard index (HI) for C. zillii and P. obscura showed no threat to human health risk through the consumption of the fish species. However, continuous consumption of the fish could probably cause health risk to the consumers of the fish. According to the study's findings, human consumption of fish species with low concentration of heavy metals at the current accumulating level is safe.

Heavy metal compartmentalisation in salt marsh and seagrass of the urbanised Swartkops estuary, South Africa

Wetland plants are naturally exposed to high metal concentrations, and often have mechanisms to prevent metal toxicity. This study compared metal concentrations in seagrass (Zostera capensis) and salt marsh (Spartina maritima, Salicornia tegetaria) - to determine their niche as metal sinks. Samples were collected in each season over a year at five sites in the estuary and analysed using a Total X-Ray Fluorescence (TXRF) spectrometer. Spartina maritima and S. tegetaria accumulated in their roots, and displayed little translocation to leaves (BCF = 1-14; TF_[leaf/root] < 1). Contrastingly, Z. capensis showed high uptake to its leaves (TF_[leaf/root] = 1-8; Mn, Zn, Cr, Pb, Ni, Cu). Spartina maritima and S. tegetaria were identified as good phytostabilisers (BCF > 1, TF_[leaf/root] < 1). Compartmentalization was unique to each species, and considering their ecosystem service importance, more plant species should be analysed to estimate their ecological value for management purposes.

Mercury in Selected Abiotic and Biotic Elements in Two Lakes in Poland: Implications for Environmental Protection and Food Safety

Mercury, which tends to bioaccumulate and biomagnify in aquatic food webs, poses a potential health risk to wildlife and to consumers of predatory fish in particular. Its concentration in biota can be high even at low environmental concentrations. Therefore, the aim of this study was to determine mercury in both abiotic (water and sediment) and biotic elements (common reed (Phragmites australis) and fish: pike (Esox lucius), bream (Abramis brama) and roach (Rutilus rutilus)) in the context of assessing the pollution of two lakes in Poland and the safety of fish consumers. The possibility of Hg biomagnification in fish was also considered. Mercury was determined by means of cold vapor atomic absorption spectrometry (CVAAS). The concentrations of Hg in water and bottom sediments of Lake Ińsko were lower than in Lake Wisola. In the bottom sediments of both lakes, a positive correlation was found between the Hg content and organic matter. The concentration of mercury in the organs of common reed did not exceed 0.017 mg/kg dry weight (dw), and its distribution can be presented as follows: root > leaves > stems > rhizomes. In fish organs from both lakes, the average mercury content did not exceed 0.086 mg/kg of wet weight (ww) and in most cases it was the highest in pike. Higher values were only observed in the muscles and skin of roach. This indicates a lack of biomagnification in the relationships between planktivorous-predatory and benthivores-predatory fish. Based on the maximum levels of mercury in fish and the calculated parameters, i.e., estimated daily intake (EDI), target hazard quotient (THQ) and tolerable weekly intake (TWI), the muscles of the examined fish were found to be safe for consumption. The average dietary exposure to total mercury (THg) and methylmercury (MeHg) was below 0.3% of the TWI.

Uptake of potentially toxic elements and polycyclic aromatic hydrocarbons from the hydromorphic soil and their cellular effects on the Phragmites australis

The current study provides an information on the combined effect of pollution with potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in hydromorphic soils on the accumulation, growth, functional and morphological-anatomical changes of macrophyte plant, i.e., Phragmites australis Cav., as well as information about their bioindication status on the example of small rivers of the Azov basin. The territory of the lower reaches of the Kagalnik River is one of the small rivers of the Eastern Azov region was examined with different levels of PTEs contamination in soils, where the excess of the lithosphere clarkes and maximum permissible concentrations (MPC) for Mn, Cr, Zn, Pb, Cu, and Cd were found. The features of the 16 priority PAHs quantitative and qualitative composition in hydromorphic soils and P. australis were revealed. The influence of soil pollution on accumulation in P. australis, as well as changes in the morphological parameters were shown. It has been observed that morphometric changes in P. australis at sites experiencing the сontamination and salinity are reflected with the changes in the ultrastructure of plastids, mitochondria, and EPR elements of plant cells. PTEs accumulated in inactive organs and damaged cell structures. At the same time, PAHs penetrated through the biomembranes and violated their integrity, increased permeability, resulted cell disorganization, meristem, and conductive tissues of roots. The nature and extent of the structural alterations found are dependent on the type and extent of pollution in the examined regions and can be utilized as bioindicators for evaluating the degree of soil phytotoxicity characterized by the accumulation of PTE and PAHs.

Phytoremediation potential of the naturally occurring wetland species in protected Long Beach in Ulcinj, Montenegro

Long Beach, situated in southern Montenegro, is subject to considerable biogenic and abiogenic influences. Thus, analyzing total heavy metal content in soil and plants in this region is, while challenging, highly important in order to assess the level for determining the soil degradation level and the phytoremediation potential of naturally growing salt marsh species. This area together with a Bojana river and backshore forms a real vegetation mosaic where habitats of various types coexist. Therefore, it represents good model system. In the present study, the levels of As, Al, B, Cd, Co, Cr, Cu, Hg, Fe, Mn, Mo, Ni, Pb and Zn in coastal soils as well as in eight salt marsh plants: Bolboschoenus maritimus, Juncus acutus, Juncus anceps, Juncus articulatus, Juncus gerardii, Juncus maritimus, Scirpus holoschoenus and Schoenus nigricans, were investigated in order to identify the plant species that can be used for the remediation of polluted sites, especially those located along the coastline. The obtained results show that species J. gerardii, J. articulatus and B. maritimus can be clearly separated from J. acutus, J. anceps, J. maritimus, S. holoschoenus and Sh. nigricans based on the degree of heavy metal accumulation in various organs. Moreover, analyses revealed that the bioaccumulation factor of underground organs is significantly higher relative to that of the aboveground parts for almost all investigated metals and species. The bioaccumulation factor had the highest value in the underground organs of J. gerardii and B. maritimus, where a value of 3.37 was measured for B and 2.54 for Hg, respectively. Hence, as all investigated species are "underground accumulators" for most of the analyzed metals, they could be useful for phytostabilization and phytoremediation of B and Hg in particular. Moreover, each plant species can be used in the phytoremediation process targeting specific heavy metals.

Analysis of Heavy Metal Content in Soil and Plants in the Dumping Ground of Magnesite Mining Factory Jelšava-Lubeník (Slovakia)

A high content of heavy metals in the soil and plants of a magnesite mining area might cause serious damage to the environment and can be a threat to the health of the surrounding population. This paper presents the results of research that focused on analyzing the heavy metal content in soil and plants in the dumping grounds of the magnesite mining factory Jelšava-Lubeník (Slovakia). The analysis focused on the content of heavy metals in soil (X-ray fluorescence spectrometry, atomic absorption spectrometry), in plants (inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectrometry), and pH (1M KCl solution). The results showed that the soil in the study area was slightly acidic to strongly alkaline and the content of Cr, As, Mn, and Mg exceeded by several times the limit values for the Slovak Republic. The results of the hierarchical cluster analysis and the correlation analysis show that the grouped metals come from the same sources of pollution. The content of heavy metals in plants was high and the highest concentration was found in the roots of Elytrigia repens > Agrostis stolonifera > Phragmites australis and flowers of Phragmites australis. The findings confirmed the suitability of the used plants in the process of phytoextraction and phytostabilization. The acquired knowledge can help in planning and realization remediation measures and improve the state of the environment in areas exposed to magnesite mining.

Temporal Potential of Phragmites australis as a Phytoremediator to Remove Ni and Pb from Water and Sediment in Lake Burullus, Egypt

In the current work, we investigated the concentration of Ni and Pb in different organs of Phragmites australis to evaluate its potential application as a phytoremediator to remove these two metals from contaminated water and sediment in Lake Burullus (a Ramsar site in Egypt). Above- and below-ground biomass of P. australis, water and sediment were sampled monthly for 1 year at six sites of Lake Burullus (three sites represent each of the northern and southern parts of the lake) using six randomly distributed quadrats (each of 0.5 × 0.5 m) at each sampling site. Significant variation was detected for Ni and Pb concentrations in the sediments and waters between the northern and southern sites of the lake. The biomass of P. australis in the southern sites was greater than that in the northern sites; in addition, the above-ground biomass was higher than the below-ground biomass. The above-ground organs accumulated higher concentrations of Ni and Pb than the below-ground organs. The Ni and Pb standing stocks data indicated that the organs of P. australis extracted higher amounts of Ni and Pb per its area from the southern rather than the northern sites. In the current study, the Ni and Pb above-ground standing stocks increased from the early growing season (February) and reached its peak during August and then decreased. The highest monthly Ni and Pb standing stock (18.2 and 18.4 g m^- 2, respectively) was recorded in the above-ground organs of plants in the southern sites in August. The bioaccumulation factor of Ni was 157.6 and 153.4 in the northern and southern sites, respectively, whereas that of Pb was 175.3 and 158.3. The translocation factor of Ni and Pb from the below- to above-ground organs was generally > 1. Thus, this reed species is a potential candidate for Ni and Pb phytoextraction. Based on our results, P. australis could be used for the extraction of Ni and Pb to reduce the pollution in Lake Burullus, if the above-ground biomass is harvested at its maximum value in August, as was the case regarding the maximum standing stock of Ni and Pb.

Accumulation of elements by submerged (Stuckenia pectinata (L.) Börner) and emergent (Phragmites australis (Cav.) Trin. ex Steud.) macrophytes under different salinity levels

Accumulation of essential/beneficial and non-essential chemical elements by submerged (Stuckenia pectinata (L.) Börner) and emergent (Phragmites australis (Cav.) Trin. ex Steud.) rooted macrophytes in three water bodies was studied as dependent on water salinity (specific conductivity) and main environmental factors (temperature, pH of water, growing period, element contents in water and sediments). Inductively coupled plasma optical emission spectrometry (ICP - OES) was used for the element detection in the plants, sediments, and water. Multivariate statistics redundancy analysis (RDA) showed that investigated factors together explained 37.8 - 44.7% and 29.9 - 42.6% of the essential/beneficial and non-essential elements variability, respectively, whereas salinity was one of the main factors determining the accumulation of a number of elements (Mg, S, Na, Li, Sr, Sb) by the macrophytes. A decrease in the essential element contents (K, P, N, Cu, Zn) was observed in both species of the macrophytes during the growing season. Environmental factors (salinity, growing period, and pH) were more significant than the element contents in water and the sediments for the essential/beneficial element accumulation by two species of the macrophytes. The element contents in the sediments to a greater extent determined non-essential element accumulation by P. australis than by S. pectinata. The study showed that the efficiency of using P. australis and S. pectinata for remediation of aquatic ecosystems contaminated by heavy metals should not decrease with a salinity increase.

Ferrous iron facilitates the formation of iron plaque and enhances the tolerance of Spartina alterniflora to artificial sewage stress

The ferrous iron (Fe²⁺) facilitates the formation of root Fe plaque of wetland plants, but its effect on the tolerance of wetland plants to artificial sewage stress has been seldom reported. In this study, the influences of Fe²⁺ on the formation of Fe plaque and its effects on the tolerance of Spartina alterniflora to artificial sewage stress were investigated. The artificial sewage stress decreased the plant height and chlorophyll content and significantly increased the MDA content in leaves. The symptoms of these stresses were alleviated with increasing Fe²⁺ concentration accompanied by significant increase in leaf alcohol dehydrogenase activity. The increase of Fe²⁺ concentration significantly increased the root Fe plaque content and reduced the accumulation of toxic metals in leaves of S. alterniflora. These results support our hypothesis that the exogenous Fe²⁺ supply may enhance the stress resistance of S. alterniflora to artificial sewage containing heavy metals.

Uptake and accumulation of metals in Spartina alterniflora salt marshes from a South American estuary

Salt marshes are capable of reducing metal pollution in coastal waters, but this capacity is highly dependent on the metal, the physico-chemical characteristics of the sediment, the plant species, the production of biomass, the time of the year, etc. The aim of this study was to assess the uptake and accumulation of Pb, Ni, Cu and Zn in Spartina alterniflora from three salt marshes within the Bahía Blanca estuary (BBE), a human-impacted Argentinean system. Metal concentrations in sediments and plants showed the same order at all sites: Zn > Cu > Pb ≥ Ni. The site with lower organic matter and fine sediment content had lower metal concentrations in the sediments, but not a lower metal content in the plant tissues, meaning that the sediment characteristics influenced the metal concentrations in the sediment and their uptake by plants. Despite differences in sediment characteristics between sites, metals were always higher in the belowground tissues than in aboveground ones and, in general, higher in dead than in live tissues. Some metals were accumulated in plant tissues, but not others, and this is dependent on the metal and the sediment characteristics. Allocation patterns of metals in tissues of S. alterniflora were mainly dependent on metal concentrations, determining higher belowground pools, but the aboveground pools were important in some cases due to higher biomass. Partitioning of metals in above or belowground pools determines their fate within the estuarine system, since tissues can decompose in situ (belowground) or be exported (aboveground). Seasonal dynamics were important for some variables but were less noticeable than the differences between sites and tissues. Our results indicate that S. alterniflora from the BBE is efficient in accumulating some metals, despite usually low metal concentrations in sediments and plants. This accumulation capacity has implications for the whole system through the fate of the tissues.

Heavy metal contamination in two commercial fish species of a trans-Himalayan freshwater ecosystem

Toxic metals have disturbed the quality of freshwater ecosystems worldwide. The concentration of heavy metals was investigated in liver, gills and muscle tissues of Schizothorax niger and Cyprinus carpio captured from river Jhelum of Kashmir Himalaya. The heavy metals displayed a wide range of disparity in studied tissues, seasons, sites and species. Cu²⁺ exhibited the highest concentration (279.6 μg/kg) in the liver tissues of S. niger in autumn at site 2 and the lowest (53.1 μg/kg) in the gill tissues in winter at site 1. In C. carpio, the Cu²⁺ was recorded highest (309.4 μg/kg) in the liver tissues in autumn at site 2. The concentration of Zn²⁺ was found highest (575.7 μg/kg) in the liver tissues at site 2 and the lowest (65.8 μg/kg) was recorded in the muscle tissues in autumn at site 1. Zn²⁺ was recorded highest (416.6 μg/kg) in the liver tissues in autumn at site 3 and lowest (51.5 μg/kg) in the gills of C. carpio during winter at site 1 (control). The concentration of Pb²⁺ (14.42 μg/kg) and Fe²⁺ (323.9 μg/kg) was observed in the liver tissue and gills of S. niger at site 3. Similar levels of Pb²⁺ and Fe²⁺ were recorded in the tissues of C. carpio at different sites. Four-way ANOVA (four way) indicated a statistically significant variation (p ≤ 0.05) in heavy metals with the sites, seasons, species and organs. The study emphasises the utmost need to monitor the level of heavy metals in S. niger on a regular basis as this native fish species is showing a continuous decline in the freshwater ecosystems of Kashmir Valley.

Metal biomonitoring in a Patagonian salt marsh

Patagonian salt marshes are not affected by pollution, but historical mining wastes are a continuous source of metals to salt marsh in San Antonio Bay. The present study evaluated the concentration of metals in sediments and used the halophyte Spartina spp. and the crab N. granulata as biomonitors. The levels of metals in sediment and organisms in SAB remained at levels corresponding to a slight enrichment or contamination. The highest levels corresponded to innermost sites of the Encerrado channel and close to the mining wastes. Spartina is a phytostabilizer so its aboveground tissues do not reflect the concentrations in the sediment; although, it retains the metals in its belowground tissues and in the rhizosediment. N. granulata showed to be a useful biomonitor for Pb, but not for the other metals.

Combined effect of water inundation and heavy metals on the photosynthesis and physiology of Spartina alterniflora

The frequency and duration of tidal flooding significantly influence the bioavailability of heavy metals (HMs) in sediment and hence exert toxicological effects on coastal wetland plants. In this study, the combined effects of different water inundation times (3, 6, 9, and 12 h) and HMs (Cu, Zn, Pb, and Cr) on the photosynthesis and physiology of Spartina alterniflora were investigated under greenhouse conditions. Results showed that S. alterniflora was somehow tolerant to the combined HMs treatments, and only the highest level of HM treatment decreased leaf chlorophyll content. Furthermore, the plants did not show any signs of victimization. Different times of water inundation with HMs did not exert any significant effect on the malonaldehyde (MDA) and chlorophyll contents in the leaves of S. alterniflora at day 20. Prolonged water inundation time at day 60 significantly reduced leaf chlorophyll content with the decrease in leaf photosynthetic rate, which was accompanied by a significant increase in the intercellular concentration of CO₂. At day 60, abscisic acid dose-dependently increased along the different water inundation times, indicating that this phytohormone is involved in plant responses to flooding stress. Peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), showed different responses to the combined treatment of water inundation and HMs at different times. At day 20, the long duration of water inundation and HMs treatments (9 h+HMs and/or 12 h+HMs) significantly increased enzyme activity in the leaves compared with the control group (6 h). At day 60, the POD and SOD activities in the leaves of S. alterniflora decreased with prolonged water inundation time, and root APX activity significantly decreased compared with the 6 h water inundation treatment.

Iron plaque formation and heavy metal uptake in Spartina alterniflora at different tidal levels and waterlogging conditions

Tidal flat elevation in the estuarine wetland determines the tidal flooding time and flooding frequency, which will inevitably affect the formation of iron plaque and accumulations of heavy metals (HMs) in wetland plants. The present study investigated the formation of iron plaque and HM's (copper, zinc, lead, and chromium) accumulation in S. alterniflora, a typical estuarine wetland species, at different tidal flat elevations (low, middle and high) in filed and at different time (3, 6, 9, 12 h per day) of waterlogging treatment in greenhouse conditions. Results showed that the accumulation of copper, zinc, lead, and chromium in S. alterniflora was proportional to the exchangeable fraction of these metals in the sediments, which generally increased with the increase of waterlogging time, whereas the formations of iron plaque in roots decreased with the increase of waterlogging time. Under field conditions, the uptake of copper and zinc in the different parts of the plants generally increased with the tidal levels despite the decrease in the metals' exchangeable fraction with increasing tidal levels. The formation of iron plaque was found to be highest in the middle tidal positions and significantly lower in low and high tidal positions. Longer waterlogging time increased the metals' accumulation but decreased the formation of iron plaque in S. alterniflora. The binding of metal ions on iron plaque helped impede the uptake and accumulation of copper and chromium in S. alterniflora.

Phytochelatins and monothiols in salt marsh plants and their relation with metal tolerance

Phytochelatins (PCs) and monothiols and their relation with trace element concentrations were studied in three plant species from two Portuguese salt marshes. Belowground tissues showed always higher element concentrations, while enhanced values of monothiols were found in aboveground biomass. Glutathione was usually the most abundant monothiol. The concentration of total PCs was higher in leaves or stems than in roots of Halimione portulacoides and Sarcocornia perennis, while in Spartina maritima the highest concentrations were reported in large roots. PC₂ was synthesized by all tissues and species and was higher in large roots of S. maritima. PC₄ and PC₅ were in high levels in small roots of S. maritima. PC₂ was positively correlated with As, Zn and Pb. Although being the first evidence of PCs and monothiols in these species under natural conditions, our results do not point to a simple relationship with elements concentrations, suggesting a complex mechanism involved.

Removal of Cu, Zn, Pb, and Cr from Yangtze Estuary Using the Phragmites australis Artificial Floating Wetlands

Contamination of heavy metals would threaten the water and soil resources; phytoremediation can be potentially used to remediate metal contaminated sites. We constructed the Phragmites australis artificial floating wetlands outside the Qingcaosha Reservoir in the Yangtze Estuary. Water characteristic variables were measured in situ by using YSI Professional Pro Meter. Four heavy metals (copper, zinc, lead, and chromium) in both water and plant tissues were determined. Four heavy metals in estuary water were as follows: 0.03 mg/Kg, 0.016 mg/Kg, 0.0015 mg/Kg, and 0.004 mg/Kg. These heavy metals were largely retained in the belowground tissues of P. australis. The bioaccumulation (BAF) and translation factor (TF) value of four heavy metals were affected by the salinity, temperature, and dissolved oxygen. The highest BAF of each metal calculated was as follows: Cr (0.091 in winter) > Cu (0.054 in autumn) > Pb (0.016 in summer) > Zn (0.011 in summer). Highest root-rhizome TF values were recorded for four metals: 6.450 for Cu in autumn, 2.895 for Zn in summer, 7.031 for Pb in autumn, and 2.012 for Cr in autumn. This indicates that the P. australis AFW has potential to be used to protect the water of Qingcaosha Reservoir from heavy metal contamination.

Hazardous metal pollution in a protected coastal area from Northern Patagonia (Argentina)

The San Antonio Bay is a protected natural coastal area of Argentina that has been exposed to mining wastes over the last three decades. Iron and trace metals of potential concern to biota and human health (Cd, Pb, Cu, and Zn) were investigated in the sediments from the bay and in the soils of the Pile (mining wastes). Concentrations of Cd (45 mg kg^-1), Pb (42,853 mg kg^-1), Cu (24,505 mg kg^-1), and Zn (28,686 mg kg^-1) in the soils Pile exceeded guidelines for agricultural, residential, and industrial land uses. Risk assessment due to exposure to contaminated soils (Pile) was performed. Hazard quotients were superior to non-risk (HQ >1) for all trace metals, while accumulative hazard quotient index indicated a high risk for children (HI = 93) and moderate for adults (HI = 9). In the bay, sediments closest to the Pile (mudflat and salt marsh) exceeded sediment quality guidelines for protection of biota. Results of different acid extraction methods suggest that most of the pseudototal content was potentially mobile. Principal component analysis indicated that the sites near the Pile (Encerrado channel) were more polluted than the distal ones. Tissues of Spartina spp. located within Encerrado channel showed the highest metal levels among all studied sites. These results show that the problem still persists and the mining wastes are the sources of the pollution. Furthermore, the Encerrado channel is a highly impacted area, as it is shown by their metal enriched sediments.

Biomass production, nutrient cycling, and carbon fixation by Salicornia brachiata Roxb.: A promising halophyte for coastal saline soil rehabilitation

In order to increase our understanding of the interaction of soil-halophyte (Salicornia brachiata) relations and phytoremediation, we investigated the aboveground biomass, carbon fixation, and nutrient composition (N, P, K, Na, Ca, and Mg) of S. brachiata using six sampling sites with varying characteristics over one growing season in intertidal marshes. Simultaneously, soil characteristics and nutrient concentrations were also estimated. There was a significant variation in soil characteristics and nutrient contents spatially (except pH) as well as temporally. Nutrient contents in aboveground biomass of S. brachiata were also significantly differed spatially (except C and Cl) as well as temporally. Aboveground biomass of S. brachiata ranged from 2.51 to 6.07 t/ha at maturity and it was positively correlated with soil electrical conductivity and available Na, whereas negatively with soil pH. The K/Na ratio in plant was below one, showing tolerance to salinity. The aboveground C fixation values ranged from 0.77 to 1.93 C t/ha at all six sampling sites. This study provides new understandings into nutrient cycling-C fixation potential of highly salt-tolerant halophyte S. brachiata growing on intertidal soils of India. S. brachiata have a potential for amelioration of the salinity due to higher Na bioaccumulation factor.

Bioaccumulation of selected metals in bivalves (Unionidae) and Phragmites australis inhabiting a municipal water reservoir

Urbanization can considerably affect water reservoirs by, inter alia, input, and accumulation of contaminants including metals. Located in the course of River Cybina, Maltański Reservoir (Western Poland) is an artificial shallow water body built for recreation and sport purposes which undergoes restoration treatment (drainage) every 4 years. In the present study, we demonstrate an accumulation of nine metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in water, sediment, three bivalve species (Anodonta anatina, Anodonta cygnea, Unio tumidus), and macrophyte Phragmites australis collected before complete drainage in November 2012. The mean concentrations of metals in the sediment, bivalves, and P. australis (roots and leaves) decreased in the following order: Fe > Mn > Zn > Cu > Cr > Ni > Pb > Co > Cd. A considerably higher bioconcentration of metals was observed in samples collected from the western and southern sites which undergo a higher degree of human impact. Sediments were found to be a better indicator of metal contamination than water samples. Interspecific differences in levels of metal accumulation were found between investigated unionids. U. tumidus accumulated higher levels of Cr, positively correlated with ambient concentrations, predisposing this species as a potential bioindicator of this metal in aquatic environments. On the other hand, species of Anodonta genus demonstrated higher accumulation of Cu and Cd. Positive correlations were found between Pb content in the sediments and tissues of all three bivalve species. In P. australis, metals were largely retained in roots except for Cd and Pb for which higher concentrations were found in leaves suggesting additional absorption of these metals from aerial sources. P. australis and bivalve from the Maltański Reservoir may be a potential source of toxic metals for animals feeding upon them and contribute to further contamination in the food chain.

Constructed wetlands to reduce metal pollution from industrial catchments in aquatic Mediterranean ecosystems: a review to overcome obstacles and suggest potential solutions

In the Mediterranean area, surface waters often have low discharge or renewal rates, hence metal contamination from industrialised catchments can have a high negative impact on the physico-chemical and biological water quality. In a context of climate and anthropological changes, it is necessary to provide an integrative approach for the prevention and control of metal pollution, in order to limit its impact on water resources, biodiversity, trophic network and human health. For this purpose, introduction of constructed wetlands (CWs) between natural aquatic ecosystems and industrialised zones or catchments is a promising strategy for eco-remediation. Analysis of the literature has shown that further research must be done to improve CW design, selection and management of wetland plant species and catchment organisation, in order to ensure the effectiveness of CWs in Mediterranean environments. Firstly, the parameters of basin design that have the greatest influence on metal removal processes must be identified, in order to better focus rhizospheric processes on specific purification objectives. We have summarised in a single diagram the relationships between the design parameters of a CW basin and the physico-chemical and biological processes of metal removal, on the basis of 21 mutually consistent papers. Secondly, in order to optimise the selection and distribution of helophytes in CWs, it is necessary to identify criteria of choice for the plant species that will best fit the remediation objectives and environmental and economic constraints. We have analysed the factors determining plant metal uptake efficiency in CWs on the basis of a qualitative meta-analysis of 13 studies with a view to determine whether the part played by metal uptake by plants is relevant in comparison with the other removal processes. Thirdly, we analysed the parameters to consider for establishing suitable management strategies for CWs and how they affect the whole CW design process. Finally, we propose monitoring and policy measures to facilitate the integration of CWs within Mediterranean industrialised catchments.

Nutrient retention in plant biomass and sediments from the salt marsh in Hangzhou Bay estuary, China

Nutrient load into the ocean can be retained during the process of plant uptake and sedimentation in marshes along the bay zone. Seasonal variations of biomass and nutrient concentration in three dominated plant assemblages and associated sediments were monitored in this study area to determine effects of salt marsh on nutrient retention. Results showed that plant aboveground biomass displayed a unimodal curve with nutrient concentration generally decreased from spring to winter. Belowground biomass was relatively low during the rapid growth period with nutrient concentration tending to decrease and then increase during this period. Plant total nitrogen (TN) pools are higher than total phosphorus (TP) pools, and both pools showed significant seasonal variations. Water purification coefficients (WPC) of nutrients by plant assimilation were 34.4/17.3, 19.3/24.0, and 5.14/6.04 t/(m(2) year) (TN/TP) for Phragmites australis, Spartina alterniflora, and Scirpus mariqueter, respectively. Overall, these results suggest that higher annual plant biomass and nutrient assimilation contribute to greater nutrient retention capacity and accumulation in sediments, thereby enabling reduced eutrophication in transitional waters.

Influence of Spartina alterniflora on the mobility of heavy metals in salt marsh sediments of the Yangtze River Estuary, China

Using bio-disturbed sulphide to trace the mobility and transformation of Cu, Pb, Ni and Zn in the sediments of the Spartina alterniflora-dominated salt marsh in the Yangtze River Estuary, measurements were made of the seasonal variations of acid-volatile sulphide (AVS) and of the simultaneously extracted metals (SEM) in the rhizosphere sediments. Microcosm incubation experiments recreating flooding conditions were conducted to evaluate the effect of AVS and other metal binding phases upon the dynamics of Cu, Pb, Ni and Zn in the salt marsh sediments. The results demonstrate that the ratio values of SEM/AVS have a significant seasonal variation in the rhizosphere sediments and that the anoxic conditions in the sediments were likely enhanced by S. alterniflora during the summer and autumn compared with the anoxic conditions resulting from the native species Phragmites australis and Scirpus mariqueter. The incubation experiments suggest that Fe(III) and Mn(IV/III) (hydr)oxides provide important binding sites for heavy metals under oxic conditions, and sulphide provides important binding sites for the Cu and Pb under anoxic conditions. Our observations indicate that the mobility of heavy metals in the salt marsh sediments is strongly influenced by biogeochemical redox processes and that the invasive S. alterniflora may increase the seasonal fluctuation in heavy metal bioavailability in the salt marsh ecosystem.

Interspecific interactions between Phragmites australis and Spartina alterniflora along a tidal gradient in the Dongtan wetland, Eastern China

The invasive species Spartina alterniora Loisel was introduced to the eastern coast of China in the 1970s and 1980s for the purposes of land reclamation and the prevention of soil erosion. The resulting interspecific competition had an important influence on the distribution of native vegetation, which makes studying the patterns and mechanisms of the interactions between Spartina alterniora Loisel and the native species Phragmites australis (Cav.) Trin ex Steud in this region very important. There have been some researches on the interspecific interactions between P. australis and S. alterniora in the Dongtan wetland of Chongming, east China, most of which has focused on the comparison of their physiological characteristics. In this paper, we conducted a neighbor removal experiment along a tidal gradient to evaluate the relative competitive abilities of the two species by calculating their relative neighbor effect (RNE) index. We also looked at the influence of environmental stress and disturbance on the competitive abilities of the two species by comparing interaction strength (I) among different tidal zones both for P. australis and S. alterniora. Finally, we measured physiological characteristics of the two species to assess the physiological mechanisms behind their different competitive abilities. Both negative and positive interactions were found between P. australis and S. alterniora along the environmental gradient. When the direction of the competitive intensity index for P. australis and S. alterniora was consistent, the competitive or facilitative effect of S. alterniora on P. australis was stronger than that of P. australis on S. alterniora. The interspecific interactions of P. australis and S. alterniora varied with environmental conditions, as well as with the method used, to measure interspecific interactions.

Growth and nutrient accumulation of Phragmites australis in relation to water level variation and nutrient loadings in a shallow lake

Shallow lake eutrophication is a global environmental issue. This study investigated the effects of water level variation and nutrient loadings on the growth and nutrient accumulation of Phragmites australis (reed) by field samplings in Baiyangdian Lake, the largest shallow lake of northern China. The field samplings were conducted in two sites of different nutrient loadings during the whole growth period of reeds, and three types of zones with different water depths were chosen for each site, including the terrestrial zone with water level below the ground, the ecotone zone with the water level varying from belowground to aboveground, and the submerged zone with water level above the ground. The result showed that reed growth was more limited by water level variation than nutrient loadings. The average stem lengths and diameters in terrestrial zones were about 26.3%-27.5% and 7.2%-12.0% higher than those in submerged zones, respectively. Similarly, the terrestrial status increased the aboveground biomass of reeds by 36.6%-51.8% compared with the submerged status. Both the nutrient concentrations and storages in the aboveground reeds were mainly influenced by the nutrient loadings in surface water and sediment rather than the water level variation of the reed growth environment, and the nutrient storages reached their maxima in late August or early September. It was observed that the maximum nitrogen storage occurred in the terrestrial zone with higher nutrient loadings, with the value of 74.5 g/m2. This study suggested that water level variation and nutrient loadings should be considered when using reeds to control and remediate eutrophication of shallow lakes.

A shallow lake remediation regime with Phragmites australis: Incorporating nutrient removal and water evapotranspiration

Shallow lake eutrophication has been an important issue of global water environment. Based on the simulation and field sampling experiments in Baiyangdian Lake, the largest shallow lake in North China, this study proposed a shallow lake remediation regime with Phragmites australis (reed) incorporating its opposite effects of nutrient removal and water evapotranspiration on water quality. The results of simulation experiments showed that both total nitrogen (TN) and phosphorus (TP) removal efficiencies increased with the increasing reed coverage. The TN removal efficiencies by reed aboveground uptake and rhizosphere denitrification were 11.2%, 13.8%, 22.6%, 28.4%, and 29.6% for the reed coverage of 20%, 40%, 60%, 80%, and 100%, respectively. Correspondingly, TP removal efficiencies by aboveground reed uptake were 1.4%, 2.5%, 4.4%, 7.4% and 7.9%, respectively. However, the water quality was best when the reed coverage was 60% (72 plants m(-2)). This was due to the fact that the concentration effect of reed evapotranspiration on nutrient increased with reed coverage. When the reed coverage was 100% (120 plants m(-2)), the evapotranspiration was approximately twice that without reeds. The field sampling results showed that the highest aboveground nutrient storages occurred in September. Thus, the proposed remediation regime for Baiyangdian Lake was that the reed coverage should be adjusted to 60%, and the aboveground biomass of reeds should be harvested in each September. With this remediation regime, TN and TP removal in Baiyangdian Lake were 117.8 and 4.0 g m(-2), respectively, and the corresponding removal efficiencies were estimated to be 49% and 8.5% after six years. This study suggests that reed is an effective plant for the remediation of shallow lake eutrophication, and its contrasting effects of nutrient removal and evapotranspiration on water quality should be considered for establishing the remediation regime in the future.

Arundo donax as a potential biomonitor of trace element contamination in water and sediment

Environmental monitoring through living organisms is an effective technique of human impact assessment, based on reliable and cost-effective biological tools of control. In this study, roots, stems and leaves of the worldwide distributed macrophyte Arundo donax (giant reed) were tested as potential biomonitors of trace element contamination in water and sediment. In particular, the concentrations of the following elements were analyzed: Al, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn. A two-year sampling was conducted in an urban watercourse of Catania (Sicily, Italy), affected by municipal and industrial discharges of wastewaters. Results showed that the amount of concentrations in plant tissues is significantly dependent on the kind of organ and element. Trace element concentrations decreased according to the pattern of root>leaf>stem, implying that roots acted as the main centers of bioaccumulation, and stems as transit organs as a consequence of the general high translocation from roots to leaves. Overall, A. donax showed a significant capacity of bioaccumulation in agreement with ecologically similar macrophytes. Positive correlations were found between trace concentrations in plant organs and sediment (Al, Cr, Mn, Ni, Zn), and water (Cu, Ni, Zn). The results of this study suggested that A. donax acts as an ecological indicator of environmental conditions, thus, its application may prove a useful tool during monitoring campaigns of wetlands.

Role of living environments in the accumulation characteristics of heavy metals in fishes and crabs in the Yangtze River Estuary, China

Correlation of heavy metals in the tissues of typical organisms (i.e., fishes and crabs) and those in their living environments (i.e., surface water, bottom water, and sediment) in Yangtze River Estuary has been qualitatively and quantitatively analyzed. Metal levels followed the trend: sediments > Eriocheir sinensis > Eriocheir leptognathus > benthic fish > pelagic fish > bottom water > surface water. Tissues in fishes and crabs of different species and sizes had diverse metal bioaccumulation characteristics, which was significantly affected by environment factors and their living habits. Metal levels in legs of crabs, and heads and skins of fishes showed significant correlations with those in their living environments. Collichthys lucidus is an effective bioindicator for assessing metal levels in water. No significant health risk was identified by the estimated daily intake and target hazard quotients analyses.

Dynamics of arsenic in salt marsh sediments from Dongtan wetland of the Yangtze River Estuary, China

The mobility and transformation of arsenic (As) in salt marsh sediments were investigated in Dongtan wetland of the Yangtze River estuary, China. As in surface water, pore water and the rhizosphere sediments were quantified. The microcosm incubation experiments were conducted during the flooding of the sediments to examine As dynamics that occurred during changing redox conditions. The concentrations of dissolved As in pore water (0.04-0.95 micromol/L) were significantly greater than that in surface water (0.03-0.06 micromol/L). Under anoxic conditions, the reactive As could be initially mobilized by the reductive dissolution of Fe(III) (hydr)oxides. Subsequently, most of the dissolved As was likely to be associated with secondary iron (hydr)oxide phases and remained in solid phases. The seasonal variability of acid volatile sulfide concentrations suggest the anoxic conditions are enhanced during summer by Spartina alterniflora compared to Phragmites australis and Scirpus mariqueter, causing a notable increase in As mobility. Generally, there was a typical variation in redox conditions with season in salt marsh sediments of Dongtan wetland, in which the dynamics of As mobility and transformation possibly were controlled by iron, and all of this could be significantly influenced by the rapid spread of S. alterniflora.

Contribution of primary producers to mercury trophic transfer in estuarine ecosystems: possible effects of eutrophication

There is an ongoing eutrophication process in the Ria de Aveiro coastal lagoon (Portugal), with progressive replacement of rooted primary producers for macroalgae. Taking advantage of a well-defined environmental contamination gradient, we studied mercury accumulation and distribution in the aboveground and the belowground biomass of several salt marsh plants, including the seagrass species Zostera noltii and the dominant green macroalgal species Enteromorpha sp. The results of these experiments were then placed into the context of the estuarine mercury cycle and transport from the contaminated area. All salt marsh plants accumulated mercury in the root system, with Halimione portulacoides showing the highest levels, with up to 1.3 mg kg(-1) observed in the most contaminated area. Belowground/aboveground ratios were generally below 0.4, suggesting that salt marsh plants are efficient immobilizers and retainers of mercury agents. Moreover, due to their sediment accretion capacities, salt marsh plants seem to play an important role in the sequestration of mercury in estuarine sediments. Seagrasses, on the other hand, accumulated considerable amounts of mercury in the aboveground biomass with belowground/aboveground ratios reaching as high as 1.4. These results may be due to their different routes of uptake (roots and foliar uptake) which suggests that seagrass meadows can be an important agent in the export of mercury from contaminated areas, considering the high aboveground biomass replacement rates. Rooted macrophytes accumulate less mercury in their aboveground biomass than macroalgae. The change of primary producer dominance due to eutrophication can originate a 4- to 5-fold increase in primary producer associated mercury. This mercury would be available for export, making it bioavailable to estuarine food webs, which stresses the need to reverse the current eutrophic status of estuarine systems.

Seasonal bioconcentration of heavy metals in Onchidium struma (Gastropoda: Pulmonata) from Chongming Island, the Yangtze Estuary, China

The seasonal concentration changes of selected heavy metal Cd, Cr, Cu, Fe, Mn, Pb, and Zn in five tissues of marine gastropod Onchidium struma were studied in the Chongming Island, the Yangtze Estuary in April 2007, July 2006, September 2006, and November 2006, respectively. The results demonstrated that the bioconcentration factor of Cu (biomass/water) in all selected tissues was about 10(4) magnitudes, Fe and Cd were 10(3), Zn was 10(2), and Mn, Pb, and Cr were 10(1). Hepatopancreas was proven to be the dominant storage tissue of Cr, Cu, Mn, and Zn, whereas Fe and Pb were mainly stored in muscle and digenetic gland, and Cd was stored in vitelline gland and albumen gland. Additionally, it was found that Cu, Fe, Mn, and Zn were concentrated significantly by O. struma (whole-body) in summer or autumn, and Cd, Cr, and Pb increased slightly in spring and winter. Furthermore, the bioconcentration of Cr was nearly 2-fold higher and Zn was 1.6-fold higher in the water compared with the Water Quality Standard for Fisheries. With view of excessive amount of Pb, Cd, and Cu according to seafood standard, the consumption of O. struma might have the risk of health hazard.