Large Amounts Of Heavy Metals Research Articles

Review of the Spatial Distribution, Source and Extent of Heavy Metal Pollution of Soil in China: Impacts and Mitigation Approaches.

Background.China has undergone a rapid industrial revolution and urbanization during the past three decades. This expansion is largely responsible for the release of a large amount of heavy metals into soils and is increasingly raising concerns over the potential effects on human health and the environment. The problem is drawing increasing attention, especially after an extensive nationwide soil survey report in 2014. A number of studies have examined soil contamination by heavy metals in China. However, most of these studies have been small in scale and it is therefore challenging to get a general overview of the level of contamination across the entire country.Objectives.The present study is aimed at presenting a synthesized overview of the extent, pattern, and impact of heavy metal contamination of soils in China, including mitigation approaches.Methods.Eighty-six journal articles and other literature such as reports, internet sources, and statistical yearbooks were narratively and critically synthesized to compile a holistic summary of sources of heavy metals, the extent of pollution, spatial distribution and impact of heavy metal contamination in China. The major findings from these studies are presented, along with mitigation approaches applicable to China.Discussion.A synthesis of major findings from recent scientific journals shows that about 10.18% of farmland soils which supports 13.86% of grain production in China is affected by heavy metals. The main sources of pollution are anthropogenic activities. Even though the spatial distribution of pollution is highly variable owing to natural and human factors, provinces with intensive industrial activities such as Henan, Shandong, and Sichuan are more highly polluted than others. These regions are top grain producing areas and hence require close follow-up for development of feasible approaches to mitigating crop contamination and associated health risks emerging in parts of China. The government recently launched a program aimed at determining sound reclamation strategies.Conclusion.Mitigation of heavy metal contamination in China requires coordination of different actors and integration of all feasible reclamation approaches.Competing Interests.The authors declare no competing financial interests.

Assessment of Contamination of Soil and Groundwater Due to e-Waste Handling

This paper reveals the magnitude of heavy metal contamination of soil and groundwater in and around an unauthorized e-waste recycling site in Delhi. Though unsafe and unorganized and with the e-waste handling now legally banned in Delhi, the informal sector is still actively involved in dismantling, extracting and disposing of e-waste in certain places on a considerably large scale. The leachate produced by these recycling units contains a large amount of heavy metals which are likely to pollute the groundwater and soil adjoining the recycling sites. This study evaluates the e-waste contamination at such sites by monitoring the potential contaminants at a number of specific monitoring points in Krishna Vihar near Mandoli. The soil and underground water samples are tested for the presence of heavy metals around e-waste recycling and dumping sites using atomic absorption spectrometry. The standard values according to Central Ground Water Board are taken as reference values for water, and standards for agricultural soil in Britain as reference values for soil. The results show that the groundwater and soil in and around these sites have been contaminated by lead, copper, chromium and cadmium to a large extent.

ASSESSMENT OF CADMIUM CONTENT IN COSMETICS BY EXTRACTION WITH DILUTED HCl AND AQUA REGIA

The intensive industrial and technological development results in an appearance of a large amount of pollutants and toxic substances in the biosphere including large quantities of heavy metals. Some heavy metals are biogenic (Cu, Zn, Se etc.) and essential for proper maintaining of the metabolism in the human body. The main dangers to the human health are associated with the exposure to toxic elements such as Pb, Cd, Hg and As. Emission of Cd in the environment has increased during the 20th century mainly due to the recycling of the products containing this element. Cadmium accumulates in the human body with a biological half-life from 10 to 30 years and could cause very serious toxic effects. Cosmetic products are potentially a source of cadmium as well as some other heavy metals mostly due to the frequent and uncontrolled usage of cosmetics of poor аnd/or suspicious quality. The goal of the study is to determine the cadmium content in various cosmetic products (lipsticks, eyeshadows and blushes) present in the markets of the Republic of Srpska. The content of Cd was determined with atomic absorption spectrophotometry (AAS) after the extraction with diluted HCl and aqua regia. The results of the research show that the cadmium concentrations in the investigated products are in accordance with the regulations of the Republic of Srpska (Regulations on safety of consumer goods; „Official Gazette RS“ – No.17/15).

Taxonomic survey of nickel hyperaccumulating plants in a Mining Site on Luzon Island, Philippines

Plants that accumulate large amounts of heavy metals can be useful for environmental phytoremediation. These hyperaccumulators are capable of tolerating high concentrations of metals which are otherwise toxic to non-hyperaccumulators. This study aimed to account and categorize hyperaccumulating plant species in the Lagonoy ophiolite complex located in Camarines Sur province on Luzon Island. Plants were collected from several sampling sites within the mining area, identified, and their nickel content was measured using AAS. A total of 44 species from 30 families were collected and classified into non-accumulators, hemiaccumulators, hyperaccumulators and hypernickelophores based on the nickel level ranges defined in the work of Fernando et al. (2013). Six species were classified as non-nickel accumulators, in which the nickel content was <100 ppm (1 ppm=1 μg Ni/g dry matter). Twenty-one species were classified as hemiaccumulators, having 100-999 μg/g Ni levels. There were 11 species of hyperaccumulators with nickel content of >1000 μg/g Ni in dry matter and six hypernickelophores with nickel content of >10000 μg/g Ni in dry matter. The plant with the highest nickel content was Lygodium circinnatum (Burm.f.) Swartz. The potential of this fern as a phytoremediation plant is discussed.

Resistance of black soldier fly (Diptera: Stratiomyidae) larvae to combined heavy metals and potential application in municipal sewage sludge treatment.

Treating municipal sewage sludge (MSS) sustainably and economically in China remains a challenge because of risks associated with the heavy metals it contains. In this study, black solider fly larvae (BSFL) were used for MSS treatment. The resistance of larvae to combined heavy metals and their potential use in conversion of MSS were investigated. The results indicated that seven MSS samples contained large amounts of heavy metals, with the lead and nickel contents of several samples exceeding Chinese national discharge standards. BSFL were highly tolerant to an artificial diet spiked with combined heavy metals. Principal component analysis revealed that high concentrations of lead, nickel, boron, and mercury potentially interfered with larval weight gain, while zinc, copper, chromium, cadmium, and mercury slightly reduced larval survival. The addition of chicken manure and wheat bran as co-substrates improved the conversion process, which was influenced by the nature and amount of added co-substrate and especially the quantity of nitrogen added. With the amended substrate, the BSFL accumulated heavy metals into their bodies but not into extracted larval oil. The heavy metal content of the treatment residue was lower than that considered safe for organic-inorganic compound fertilizers standards in China and the harvested larvae could be used as a source of oil for industrial application.

BOF steel slag as a low-cost sorbent for vanadium (V) removal from soil washing effluent

Soil washing is an effective remediation method to remove heavy metals from contaminated soil. However, it produces wastewater that contains large amounts of heavy metals, which lead to serious pollution. This study investigated the removal of vanadium (V) from synthetic soil washing effluent using BOF steel slag. The effects of particle size, slag dosage, initial pH, and initial vanadium concentration on removal behavior were studied. Adsorption kinetics and isotherms were also analyzed. The results showed that the vanadium removal efficiency increased as the steel slag particle size decreased and as the amount of slag increased. The initial pH and vanadium concentration did not play key roles. At the optimum particle size (<0.15 mm) and dosage (50 g/L), the removal rate reached 97.1% when treating 100 mg/L of vanadium. The influence of the washing reagent residue was studied to simulate real conditions. Citric acid, tartaric acid, and Na2EDTA all decreased the removal rate. While oxalic acid did not have negative effects on vanadium removal at concentrations of 0.05–0.2 mol/L, which was proved by experiments using real washing effluents. Considering both soil washing effect and effluent treatment, oxalic acid of 0.2 mol/L is recommended as soil washing reagent.

Distribution and health risk assessment to heavy metals near smelting and mining areas of Hezhang, China.

Mining and smelting areas in Hezhang have generated a large amount of heavy metals into the environment. For that cause, an evaluative study on human exposure to heavy metals including Co, Ni, Cu, Zn, Cr, As, Cd, Pb, Sb, Bi, Be, and Hg in hair and urine was conducted for their concentrations and correlations. Daily exposure and non-carcinogenic and carcinogenic risk were estimated. Sixty-eight scalp hair and 66 urine samples were taken from participants of different ages (6-17, 18-40, 41-60, and ≥65years) living in the vicinity of an agricultural soil near mine and smelting areas. The results compared to the earlier studies showed an elevated concentration of Pb, Be, Bi, Co, Cr, Ni, Sb, and Zn in hair and urine. These heavy metals were more elevated in mining than in smelting. Considering gender differences, females were likely to be more affected than male. By investigating age differences in this area, high heavy metal concentrations in male's hair and urine existed in age of 18-40 and ≥66, respectively. However, females did not present homogeneous age distribution. Hair and urine showed a different distribution of heavy metals in different age and gender. In some cases, significant correlation was found between heavy metals in hair and urine (P>0.05 and P>0.01) in mining area. The estimated average daily intake of heavy metals in vegetables showed a great contribution compared to the soil and water. Non-carcinogenic and carcinogenic risk values of total pathways in mining and smelting areas were higher than 1 and exceeded the acceptable levels. Thus, the obtained data might be useful for further studies. They can serve as a basis of comparison and assessing the effect of simultaneous exposure from heavy metals in mining and smelting areas, and potential health risks from exposure to heavy metals in vegetables need more consideration.

Combined toxicity and underlying mechanisms of a mixture of eight heavy metals.

With the rapid development of modernization and industrialization in China, a large quantity of heavy metals, including zinc, copper, lead, cadmium and mercury, have been entering the atmosphere, soil and water, the latter being the primary route of pollution. In the present study, invitro experiments were performed to examine the joint toxicity and the underlying mechanisms of the eight most common heavy metals contaminating offshore waters on the eastern coast of Ningbo region. Using a cell cycle assay, cell apoptosis and reactive oxygen species (ROS) detection methods, the present study demonstrated that the heavy metal mixture arrested JB6 cells at the S phase, induced the generation of ROS and cell apoptosis. A luciferase assay indicated that the levels of activator protein‑1 and nuclear factor‑κB transcription factors were upregulated. Upregulation of the protein levels of C‑jun and p65 were detected in the JB6 cells by western blot analysis; these two genes have important roles in cell carcinogenesis. These results provide a useful reference for further investigations on the combined toxicity of the exposure to multiple heavy metals.

The Effect of Ammonium Sulfate on the Sulphate Reducing Bacteria Bio-Derived Material

The lead-zinc tailings, a kind of hazardous wastes, containing large amount of heavy metals with high extraction toxicity, which would be released into solution with water, oxygen, microorganism and make the environment contaminated. Sulfide ion and alkaline substance were produced with the growth and anaerobic metabolism of sulphate reducing bacteria, inhibiting the oxidation and release of heavy metal ions from the lead-zinc tailings. Sulphate reducing bacteria attached on the calcined activated carbon while growing in the nutrient solution, which could be used to decline heavy metal ions as bio-derived material. Inorganic nitrogen source could be used by autotrophic bacteria effectively and was negative for the sulphate reducing bacteria to deposit toxic elements in the solution.

Immobilization of heavy metals in electroplating sludge by biochar and iron sulfide.

Electroplating sludge (ES) containing large quantities of heavy metals is regarded as a hazardous waste in China. This paper introduced a simple method of treating ES using environmentally friendly fixatives biochar (BC) and iron sulfide (FeS), respectively. After 3days of treatment with FeS at a FeS-to-ES mass ratio of 1:5, the toxicity characteristic leaching procedure (TCLP)-based leachability of total Cr (TCr), Cu(II), Ni(II), Pb(II), and Zn(II) was decreased by 59.6, 100, 63.8, 73.5, and 90.5%, respectively. After 5days of treatment with BC at a BC-to-ES mass ratio of 1:2, the TCLP-based leachability was declined by 35.1, 30.6, 22.3, 23.1, and 22.4%, respectively. Pseudo first-order kinetic model adequately simulated the sorption kinetic data. Structure and morphology analysis showed that adsorption, electrostatic attraction, surface complexation, and chemical precipitation were dominant mechanisms for heavy metals immobilization by BC, and that chemical precipitation (formation of metal sulfide and hydroxide precipitates), iron exchange (formation of CuFeS2), and surface complexation were mainly responsible for heavy metals removal by FeS. Economic costs of BC and FeS were 500 and 768 CNY/t, lower than that of Na2S (940 CNY/t). The results suggest that BC and FeS are effective, economic, and environmentally friendly fixatives for immobilization of heavy metals in ES before landfill disposal.

Status of Toxic Metal Pollution of Soil in and around Araromi Metal Scrap Dumpsite, Akure, Ondo State

Most problems of soil pollution are associated with large amount of heavy metals deposited on it through disposed waste. This study was carried out to assess heavy metals (Fe, Zn, Pb, Cu and Cd) in soil samples around metal scrap dumps at Araromi vicinities of Akure South Local Government, Ondo State, Nigeria, in order to assess the effects of the dumps on the soils. A total of thirty nine soil samples were taken for laboratory analysis. The soil samples were collected using hand driven stainless steel auger at various depths at the dumpsite, and at various horizontal distances away from the dumpsite including human settlements close to the dumpsite. The heavy metals in the waste soils samples was sequentially extracted and quantified, using atomic absorption spectrometry (AAS). The findings revealed that Iron, Lead, Cadmium and Copper with concentration of 611.7 mg/kg, 200.8 mg/kg, 4.9 mg/kg and 103 mg/kg respectively, all exceeded National Environmental Standards and Regulation Enforcement Agency (NESREA) acceptable limit Original Research Article Simon-Oke and Fadoju; JGEESI, 5(4): 1-9, 2016; Article no.JGEESI.23363 2 and index of 2007, except Zinc 229.2 mg/kg The order was Fe>Zn>Pb>Cu>Cd for the study area. A consistent trend showing a decrease in the concentration of toxic metals was observed at increasing depths and distances from dumpsite, which suggest a discontinuation or mitigation of anthropogenic input on the environment.

A Review on the Management of Municipal Solid Waste Fly Ash in American

With the accelerating process of urbanization, the amount of municipal solid waste (MSW) generation increases continuously. Landfill occupies a lot of land resources, leading several cities run into a condition being surrounded by MSW. In recent years, MSW incineration rises gradually. Incineration can reduce the MSW volume by 85%∼90% and the mass by about 80%, and incineration with energy recovery is one of the several waste-to-energy (WtE) technologies [1–3]. However, municipal solid waste incineration fly ash, byproducts of MSW incineration, contains large amounts of heavy metals and dioxins, improper disposal will cause serious environmental and human health hazards. This review summarizes the MSW incineration fly ash management system and related policies and regulations in United States, as well as the main disposal methods and utilization technology, in order to provide reference for the management of MSW incineration fly ash in China.

Distribution and assessment of heavy metals in the surface sediment of Yellow River, China

Large amounts of heavy metals discharged by industrial cities that are located along the middle reach of Yellow River, China have detrimental impacts on both the ecological environment and human health. In this study, fourteen surface sediment samples were taken in the middle reach of the Yellow River. Contents of Zn, Pb, Ni, Cu, Cr, Cd, As were measured, and the pollution status was assessed using three widely used pollution assessment methods, including the single factor index method, Nemerow pollution index method and potential ecological risk index. The concentrations of the studied heavy metals followed the order: Zn>Cr>Cu>Ni>Pb>As>Cd. Nearly 50% of sites had Cu and Cr accumulation. The concentration of Cu at the Yiluo River exceeded the secondary standard value of the Environmental quality standard for soils. Comparison of heavy metal concentrations between this study and other selected rivers indicated that Cu and Cr may be the major pollutants in our case. The single factor index indicated that many samples were at high levels of pollution for Cu and Cd; the Nemerow pollution index indicated that the Yihe River, Luohe River, Yiluo River and Huayuankou were polluted. According to the results of potential ecological risk assessment, Cd in the tributaries of Luo River, Yihe River, and Yiluo River showed high risk toward the ecosystem and human health, Cd in Huanyuankou and Cu in Yiluo River showed a middle level of risk and other samples were at a low level of risk.

The major parameters on biomass pyrolysis for hyperaccumulative plants--A review.

Phytoextraction is one of the main phytoremediation techniques and it has often been described as a potentially feasible in situ soil decontamination method of large amounts of heavy metals, organic pollutants and explosive compounds. As this remediation technique is approaching extensive on-field experimentation and commercialization, research focus is on investigating new ways to achieve the valorisation of its by-products. Biomass pyrolysis represents a key step to numerous valorisation options and it is characterized by differential output products that are determined by the operating conditions of the process and the characteristics of the input. However, when used to valorise plants that have undergone significant metal uptake, this strategy involves some new aspects related to harvest, procedure and final product reutilization. This paper reviews the studies made on biomass pyrolysis of plants with emphasis on the differential quality and distribution of pyrolysis products in relation with the variables of the process and the metal-rich phytoextraction feedstock properties. By investigating these parameters, this survey provides indications on ways to optimize the valorisation of phytoremediation by-products through biomass pyrolysis.

Submicron-Scale Heterogeneities in Nickel Sorption of Various Cell-Mineral Aggregates Formed by Fe(II)-Oxidizing Bacteria.

Fe(II)-oxidizing bacteria form biogenic cell-mineral aggregates (CMAs) composed of microbial cells, extracellular organic compounds, and ferric iron minerals. CMAs are capable of immobilizing large quantities of heavy metals, such as nickel, via sorption processes. CMAs play an important role for the fate of heavy metals in the environment, particularly in systems characterized by elevated concentrations of dissolved metals, such as mine drainage or contaminated sediments. We applied scanning transmission (soft) X-ray microscopy (STXM) spectrotomography for detailed 3D chemical mapping of nickel sorbed to CMAs on the submicron scale. We analyzed different CMAs produced by phototrophic or nitrate-reducing microbial Fe(II) oxidation and, in addition, a twisted stalk structure obtained from an environmental biofilm. Nickel showed a heterogeneous distribution and was found to be preferentially sorbed to biogenically precipitated iron minerals such as Fe(III)-(oxyhydr)oxides and, to a minor extent, associated with organic compounds. Some distinct nickel accumulations were identified on the surfaces of CMAs. Additional information obtained from scatter plots and angular distance maps, showing variations in the nickel-iron and nickel-organic carbon ratios, also revealed a general correlation between nickel and iron. Although a high correlation between nickel and iron was observed in 2D maps, 3D maps revealed this to be partly due to projection artifacts. In summary, by combining different approaches for data analysis, we unambiguously showed the heterogeneous sorption behavior of nickel to CMAs.

Effective reuse of electroplating rinse wastewater by combining calcined oyster shell powder with H2O2/UV process

In this study, the merits of combining the oyster shell powder (OSP) pre-treatment with H2O2/UV post-oxidation for the reuse of electroplating rinse wastewater were evaluated. The results showed that the calcined OSP was more effective in removing heavy metals than the original OSP. For the 1,000°C-calcined OSP of 0.6 g/L, the removals were 98, 94, and 99% for Fe, Ni, and Cr, respectively. That is, a small quantity of the calcined OSP could remove a large quantity of heavy metals due to the large specific surface area and the dramatically increased pH; the former resulted in a better adsorption capability and the latter induced buck precipitation. Further, after the post H2O2/UV process, the chemical oxygen demand and total organic carbon were reduced from 1,206 to 41.2 mg/L and from 252 to 12.6 mg/L, respectively, for pH of 8.0, H2O2 of 1,000 mg/L, UV of 52 W, and oxidation time of 240 min. That is, the combination of calcined OSP pre-treatment and H2O2/UV post-oxidation could not only treat the electroplating rinse wastewater to comply with the Taiwan’s effluent standard but could also satisfy the in-house water reuse criteria while resolving the issue of waste oyster shells simultaneously.

Cadmium, lead, and zinc mobility and plant uptake in a mine soil amended with sugarcane straw biochar.

Accumulation of heavy metals in unconsolidated soils can prove toxic to proximal environments, if measures are not taken to stabilize soils. One way to minimize the toxicity of metals in soils is the use of materials capable of immobilizing these contaminants by sorption. Biochar (BC) can retain large amounts of heavy metals due to, among other characteristics, its large surface area. In the current experiment, sugarcane-straw-derived biochar, produced at 700 °C, was applied to a heavy-metal-contaminated mine soil at 1.5, 3.0, and 5.0% (w/w). Jack bean and Mucuna aterrima were grown in pots containing a mine contaminated soil and soil mixed with BC. Pore water was sampled to assess the effects of biochar on zinc solubility, while soils were analyzed by DTPA extraction to confirm available metal concentrations. The application of BC decreased the available concentrations of Cd, Pb, and Zn in the mine contaminated soil leading to a consistent reduction in the concentration of Zn in the pore water. Amendment with BC reduced plant uptake of Cd, Pb, and Zn with the jack bean uptaking higher amounts of Cd and Pb than M. aterrima. This study indicates that biochar application during mine soil remediation could reduce plant concentrations of heavy metals. Coupled with this, symptoms of heavy metal toxicity were absent only in plants growing in pots amended with biochar. The reduction in metal bioavailability and other modifications to the substrate induced by the application of biochar may be beneficial to the establishment of a green cover on top of mine soil to aid remediation and reduce risks.

Bacterial Treatment and Metal Characterization of Biomedical Waste Ash

Biomedical waste ash generated due to the incineration of biomedical waste contains large amounts of heavy metals and polycyclic aromatic hydrocarbons (PAHs), which is disposed of in regular landfills, and results in unfavorable amounts of hazardous materials seeping into the ground and may pollute surface water and groundwater. Therefore, it is essential to remove the toxicity of ash before disposal into landfills or reutilization. Environmental characteristic analysis of BMW ash showed increased hardness (1320 mg/L) and chloride (8500 mg/L) content in leachate compared to World Health Organization (WHO) and Environment Protection Agency (EPA) guidelines for drinking water (hardness, 300 mg/L; chloride, 250 mg/L). The alkalinity and pH of the ash leachate were 400 mg/L and 8.35, respectively. In this paper, study was carried out to investigate the metal tolerance level of bacterial isolates isolated from soil. The isolate Bacillus sp. KGMDI can tolerate up to 75 mg/L of metal concentration (Mn, Mo, Cr, Fe, Cu, and Zn) in enriched growth medium. This shows that the isolated culture is capable of growing in presence of high concentration of heavy metals and acts as potential biological tool to reduce the negative impact of BMW ash on the environment during landfilling.

Pike (Esox lucius) Bio-indicator of Heavy Metal Pollution in Anzali Wetland

The economical and industrial aspects of aquatic organisms like fish make the topic of toxicants important. The present study was carried out to measure the accumulation of heavy metals (Pb, Sn and Zn) in the liver and muscle of pike (Esox lucius). Totally, 60 pikes have been collected from 6 stations in the Anzali wetland (the south coast of the Caspian Sea) included Pirbazar, Anzali, Abkenar, Sangachin, Beshman, and Khazarvila. Tissue samples were prepared according to MOOPAM method. Zn concentration was determined using a atomic absorption spectrophotometer. Pb and Sn were also measured by graphite furnace atomic absorption spectrophotometer. The highest concentrations of heavy metals were measured in the muscle and liver of pikes collected from Anzali and Pirbazar stations (located in the northeast of the wetland) due to the large amount of heavy metals release into these stations from adjacent shipbuilding factories and oil jetty. Comparison of the levels of three metals in fish tissues with international standards showed that Pb concentration was significantly higher in Anzali and Pirbazar fish than the permissible limit determined by WHO.

Impact of artificial water and sediment discharge regulation in the Huanghe (Yellow River) on the transport of particulate heavy metals to the sea

Variations in the concentrations of major particulate heavy metals (PHMs) (Mn, Pb, Zn, V, Cr, and Ni) and fluxes into the sea during the water–sediment regulation scheme (WSRS) in the Huanghe (Yellow River) were examined based on observational and measured data during June and July of 2009. Two stages of variations in the concentrations of PHMs were observed in the WSRS with lower values in the early stage and higher values in the late stage. The early stage corresponded to a high water discharge with coarser sediment that was largely scored from the riverbed, and the late stage corresponded to a low water discharge with much finer sediment that was released from the Xiaolangdi reservoir. The significant increase in PHM concentrations by 2–4 fold from the early to the late stage largely resulted from a decrease in the suspended-sediment grain size and an increase in the quantity of anthropogenic pollutants caused by changes in the sediment sources from riverbed in the lower reaches to the Xiaolangdi reservoir during the WSRS. The concentrations of PHMs, particularly in the late stage of the WSRS, were approximately two times as high as those during the pre-WSRS period as the anthropogenic pollutants have been increasing in recent years. More than 57% of the annual quantity of PHMs was transported to the sea during the WSRS, and over 34% of that from the Xiaolangdi reservoir was delivered to the sea during the late stage of the WSRS over a period of approximately 4–5days. This large quantity of heavy metals, with a high proportion of labile components because of the increasing contribution of anthropogenic pollutants, emptied into the sea over a short period and may thus drastically alter the eco-environment in the river mouth and its adjacent seas.