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12 pages, 56937 KiB

Open AccessArticle

Holocene Hydroclimatic Changes in Northern Peloponnese (Greece) Inferred from the Multiproxy Record of Lake Lousoi

by Dionysios Stamatis, Alexandros Emmanouilidis, Alessia Masi, Adam Izdebski and Pavlos Avramidis

Water 2022, 14(4), 641; https://doi.org/10.3390/w14040641 - 18 Feb 2022

Cited by 3 | Viewed by 2508

Abstract

This research presents the paleoenvironmental evolution of a drained lake at the Lousoi plateau (northern Peloponnese), for the last 10,000 years, through the study of a 7 m depth core. Analyses conducted on the core include grain size, TOC, TN, pH, EC, total [...] Read more.

This research presents the paleoenvironmental evolution of a drained lake at the Lousoi plateau (northern Peloponnese), for the last 10,000 years, through the study of a 7 m depth core. Analyses conducted on the core include grain size, TOC, TN, pH, EC, total carbonates (%), magnetic susceptibility measurements, XRF analysis, and radiocarbon dating. Our paleoenvironmental reconstruction was based on geochemical proxies’ distribution in the core, combined with sediment physical and textural characteristics and later comparison between additional lacustrine archives from northern Peloponnese. From 10,900 to 7700 cal BP lacustrine, organic-rich deposits were recognized, reflecting increased lake water levels. Wet climatic conditions seem to have prevailed during this phase, interrupted by a dry pulse at 9400 cal BP. Transition to more shallow waters was marked at 8200 cal BP due to increased sediment deposition in the lake, with the environmental status shifting to a more oxygenated phase. Overall, wet conditions prevailed in this period and are in good agreement with regional records. In the Late Holocene period, the lake seems to have been highly affected by pedogenic processes, and thus, it was difficult to distinguish paleoclimatic/paleoenvironmental signals. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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12 pages, 2162 KiB

Open AccessArticle

Estimation of Heavy Metal Concentrations in the Water of Urban Lakes in the Russian Arctic (Murmansk)

by Marina A. Postevaya, Zakhar I. Slukovskii, Vladimir A. Dauvalter and Daria S. Bernadskaya

Water 2021, 13(22), 3267; https://doi.org/10.3390/w13223267 - 17 Nov 2021

Cited by 8 | Viewed by 3505

Abstract

This article presents the results of the analysis and estimation of the seasonal variation of heavy metals in the water of urban lakes and the assessment of their environmental state based on the chemical data. The research covered seven lakes in Murmansk, subject [...] Read more.

This article presents the results of the analysis and estimation of the seasonal variation of heavy metals in the water of urban lakes and the assessment of their environmental state based on the chemical data. The research covered seven lakes in Murmansk, subject to various levels of anthropogenic load. Field studies were conducted in 2019–2020. Water samples were taken both in summer and in winter/spring seasons. The most polluted lake was Lake Ledovoe, where the highest concentrations of V, Cr, Co, Ni, Cu, W, and Mn were found. Lake Yuzhnoe, which is characterized by the lowest concentrations of studied heavy metals, was the least subject to anthropogenic load. In total, V, Ni, Zn, Fe, and Mn were above the background levels in the lakes of Murmansk. The analysis of the seasonal variation showed that the highest concentrations of heavy metals were found in winter/spring season and reached their maximum during the period of melt water intake from the catchment area. The research showed the impact of the urban environment on the chemical composition of the Murmansk lakes. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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13 pages, 2139 KiB

Open AccessFeature PaperArticle

Effects of Plastic Debris on the Biofilm Bacterial Communities in Lake Water

by Chao Shen, Liuyan Huang, Guangwu Xie, Yulai Wang, Zongkai Ma, Yu Yao and Hong Yang

Water 2021, 13(11), 1465; https://doi.org/10.3390/w13111465 - 23 May 2021

Cited by 15 | Viewed by 4454

Abstract

Increasing discharge of plastic debris into aquatic ecosystems and the worsening ecological risks have received growing attention. Once released, plastic debris could serve as a new substrate for microbes in waters. The complex relationship between plastics and biofilms has aroused great interest. To [...] Read more.

Increasing discharge of plastic debris into aquatic ecosystems and the worsening ecological risks have received growing attention. Once released, plastic debris could serve as a new substrate for microbes in waters. The complex relationship between plastics and biofilms has aroused great interest. To confirm the hypothesis that the presence of plastic in water affects the composition of biofilm in natural state, in situ biofilm culture experiments were conducted in a lake for 40 days. The diversity of biofilm attached on natural (cobble stones (CS) and wood) and plastic substrates (Polyethylene terephthalate (PET) and Polymethyl methacrylate (PMMA)) were compared, and the community structure and composition were also analyzed. Results from high-throughput sequencing of 16S rRNA showed that the diversity and species richness of biofilm bacterial communities on natural substrate (observed species of 1353~1945, Simpson index of 0.977~0.989 and Shannon–Wiener diversity index of 7.42~8.60) were much higher than those on plastic substrates (observed species of 900~1146, Simpson index of 0.914~0.975 and Shannon–Wiener diversity index of 5.47~6.99). The NMDS analyses were used to confirm the taxonomic significance between different samples, and Anosim (p = 0.001, R = 0.892) and Adonis (p = 0.001, R = 808, F = 11.19) demonstrated that this classification was statistically rigorous. Different dominant bacterial communities were found on plastic and natural substrates. Alphaproteobacterial, Betaproteobacteria and Synechococcophycideae dominated on the plastic substrate, while Gammaproteobacteria, Phycisphaerae and Planctomycetia played the main role on the natural substrates. The bacterial community structure of the two substrates also showed significant difference which is consistent with previous studies using other polymer types. Our results shed light on the fact that plastic debris can serve as a new habitat for biofilm colonization, unlike natural substrates, pathogens and plastic-degrading microorganisms selectively attached to plastic substrates, which affected the bacterial community structure and composition in aquatic environment. This study provided a new insight into understanding the potential impacts of plastics serving as a new habitat for microbial communities in freshwater environments. Future research should focus on the potential impacts of plastic-attached biofilms in various aquatic environments and the whole life cycle of plastics (i.e., from plastic fragments to microplastics) and also microbial flock characteristics using microbial plastics in the natural environment should also be addressed. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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19 pages, 3401 KiB

Open AccessFeature PaperArticle

Efficient Removal of Antimony(III) in Aqueous Phase by Nano-Fe₃O₄ Modified High-Iron Red Mud: Study on Its Performance and Mechanism

by Yizhe Peng, Lin Luo, Shuang Luo, Kejian Peng, Yaoyu Zhou, Qiming Mao, Jian Yang and Yuan Yang

Water 2021, 13(6), 809; https://doi.org/10.3390/w13060809 - 16 Mar 2021

Cited by 10 | Viewed by 3267

Abstract

The resource utilization of excess red mud produced from aluminum production is a current research focus. In this study, novel nano-Fe₃O₄ modified high-iron red mud material (HRM@nFe₃O₄) was fabricated using the method of co-precipitation to remove [...] Read more.

The resource utilization of excess red mud produced from aluminum production is a current research focus. In this study, novel nano-Fe₃O₄ modified high-iron red mud material (HRM@nFe₃O₄) was fabricated using the method of co-precipitation to remove Sb(III) from the aqueous phase. The HRM@nFe₃O₄ at a nFe₃O₄:HRM mass ratio of 1:1 had optimal adsorbing performance on Sb(III) in water. Compared with others, the synthetic HRM@nFe₃O₄ sorbent had a superior maximum Sb(III) adsorption capacity of 98.03 mg·g⁻¹, as calculated by the Langmuir model, and a higher specific surface area of 171.63 m²·g⁻¹, measured using the Brunauer-Emmett-Teller measurement. The adsorption process was stable at an ambient pH range, and negligibly limited by temperature the coexisting anions, except for silicate and phosphate, suggesting the high selectivity toward Sb(III). HRM@nFe₃O₄ retained more than 60% of the initial adsorption efficiency after the fifth adsorption-desorption cycle. The kinetic data fitted by the pseudo-second-order model illustrated the existence of a chemical adsorption process in the adsorption of Sb(III). Further mechanism analysis results indicated that the complexation reaction played a major role in Sb(III) adsorption by HRM@nFe₃O₄. This HRM@nFe₃O₄ adsorbent provides an effective method for the removal of Sb(III) in wastewater treatment and is valuable in the reclamation of red mud. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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13 pages, 2092 KiB

Open AccessFeature PaperArticle

Nitrogen Loss in Vegetable Field under the Simulated Rainfall Experiments in Hebei, China

by Baoguo Ma, Ronghao Guan, Liang Liu, Zhixi Huang, Shuanwang Qi, Zengfu Xi, Ying Zhao, Shihao Song and Hong Yang

Water 2021, 13(4), 552; https://doi.org/10.3390/w13040552 - 21 Feb 2021

Cited by 13 | Viewed by 3320

Abstract

Agricultural non-point source pollution is one of the main factors contaminating the environment. However, the impact of rainfall on loss of non-point nitrogen is far from well understood. Based on the artificial rainfall simulation experiments to monitor the loss of dissolved nitrogen (DN) [...] Read more.

Agricultural non-point source pollution is one of the main factors contaminating the environment. However, the impact of rainfall on loss of non-point nitrogen is far from well understood. Based on the artificial rainfall simulation experiments to monitor the loss of dissolved nitrogen (DN) in surface runoff and interflow of vegetable field, this study analyzed the effects of rainfall intensity and fertilization scheme on nitrogen (N) loss. The results indicated that fertilizer usage is the main factor affecting the nitrogen loss in surface runoff, while runoff and rainfall intensity play important roles in interflow nitrogen loss. The proportion of DN lost through the surface runoff was more than 91%, and it decreased with increasing rainfall intensity. There was a clear linear trend (r² > 0.96) between the amount of DN loss and runoff. Over 95% of DN was lost as nitrate nitrogen (NN), which was the major component of nitrogen loss. Compared with the conventional fertilization treatment (CF), the amount of nitrogen fertilizer applied in the optimized fertilization treatment (OF) decreased by 38.9%, and the loss of DN decreased by 28.4%, but root length, plant height and yield of pak choi increased by 6.3%, 2.7% and 5.6%, respectively. Our findings suggest that properly reducing the amount of nitrogen fertilizer can improve the utilization rate of nitrogen fertilizer but will not reduce the yield of pak choi. Controlling fertilizer usage and reducing runoff generation are important methods to reduce the DN loss in vegetable fields. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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17 pages, 5174 KiB

Open AccessFeature PaperArticle

Identifying the Mechanisms behind the Positive Feedback Loop between Nitrogen Cycling and Algal Blooms in a Shallow Eutrophic Lake

by Yu Yao, Huaji Liu, Ruiming Han, Dujun Li and Limin Zhang

Water 2021, 13(4), 524; https://doi.org/10.3390/w13040524 - 18 Feb 2021

Cited by 7 | Viewed by 5036

Abstract

Algal blooms have increased in frequency, intensity, and duration in response to nitrogen (N) cycling in freshwater ecosystems. We conducted a high-resolution sedimentary study of N transformation and its associated microbial activity in Lake Taihu to assess the accumulation rates of the different [...] Read more.

Algal blooms have increased in frequency, intensity, and duration in response to nitrogen (N) cycling in freshwater ecosystems. We conducted a high-resolution sedimentary study of N transformation and its associated microbial activity in Lake Taihu to assess the accumulation rates of the different N fractions in response to algal blooms, aiming to understand the mechanisms of N cycling in lacustrine environments. Downcore nitrification and denitrification processes were measured simultaneously in situ via diffusive gradients in thin-films technique, peeper, and microelectrode devices in a region of intensified algal blooms of shallow lake. The decomposition of different biomasses of algal blooms did not change the main controlling factor on different N fractions in profundal sediment. However, the decomposition of different algal biomasses led to significant differences in the nitrification and denitrification processes at the sediment–water interface (SWI). Low algal biomasses facilitated the classic process of N cycling, with the balanced interaction between nitrification and denitrification. However, the extreme hypoxia under high algal biomasses significantly limited nitrification at the SWI, which in turn, restricted denitrification due to the lack of available substrates. Our high-resolution results combined with estimates of apparent diffusion fluxes of the different N fractions inferred that the lack of substrates for denitrification was the main factor influencing the positive feedback loop between N and eutrophication in freshwater ecosystems. Moreover, this positive feedback can become irreversible without technological intervention. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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19 pages, 3198 KiB

Open AccessFeature PaperArticle

Identification of Nitrate Sources in Rivers in a Complex Catchment Using a Dual Isotopic Approach

by Yunyun Xu, Qiqi Yuan, Chunfa Zhao, Lachun Wang, Yuhua Li, Xiaoxue Ma, Jiaxun Guo and Hong Yang

Water 2021, 13(1), 83; https://doi.org/10.3390/w13010083 - 1 Jan 2021

Cited by 13 | Viewed by 4923

Abstract

Excessive nutrient input to surface water, including nitrate, exacerbates water eutrophication. Clarifying the proportions of different nitrate sources in the aquatic environment is critical for improving the polluted water. However, nitrate sources in river basins are very complex and not clearly understood. In [...] Read more.

Excessive nutrient input to surface water, including nitrate, exacerbates water eutrophication. Clarifying the proportions of different nitrate sources in the aquatic environment is critical for improving the polluted water. However, nitrate sources in river basins are very complex and not clearly understood. In this study, nitrogen concentrations and nitrate isotopic compositions were determined to estimate the spatiotemporal variation in nitrate sources in the Yuntaishan River basin, Nanjing, East China, from March 2019 to January 2020. The results showed that the concentrations of total nitrogen (TN), ammonium (NH₄⁺-N), and nitrate (NO₃⁻-N) changed in the ranges of 0.53–18.0 mg/L, 0.01–15.4 mg/L, and 0.06–9.3 mg/L, respectively, wherein NO₃⁻-N was the main nitrogen form. Higher nitrogen concentrations appeared in winter and in the downstream parts of the river. In the entire river basin, the NO₃⁻-N mainly originated from sewage (67%) and soil (26%), with clear spatial variations. NO₃⁻-N in the Yunba sub-watershed was mainly derived from sewage (78%), which was higher than that in other tributaries, i.e., Shengli River (44%) and Yangshan River (49%). This was due to the fact that that Shengli and Yangshan sub-watersheds were covered by urban areas and were equipped with a complete sewage treatment system. In addition, the contributions of sewage to NO₃⁻-N rose from 60% upstream to 86% downstream, suggesting the increasing influence of the point source of sewage. The results showed that 53% of NO₃⁻-N in the basin outlet originated from the point source of sewage near the M4 site. Sewage contributed 75% of NO₃⁻-N in the rainy season and 67% of NO₃⁻-N in the dry season, suggesting the weakly temporal variation. Our results highlight the spatiotemporal variations in sources of NO₃⁻-N. These results will aid in the development of measures needed to control nitrogen pollution in river basins. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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14 pages, 984 KiB

Open AccessArticle

Microbial Carbon Metabolic Functions in Sediments Influenced by Resuspension Event

by Miao Wu, Ming Zhang, Wei Ding, Lin Lan, Zhilin Liu, Lingzhan Miao and Jun Hou

Water 2021, 13(1), 7; https://doi.org/10.3390/w13010007 - 23 Dec 2020

Cited by 9 | Viewed by 2748

Abstract

Microorganisms in sediments are an important part of the aquatic ecosystem, and their functional activities are sensitive to external environmental pressure. Shallow lakes are characterized by frequent sediment resuspension events, leading to large amounts of nutrients being released. However, information about the potential [...] Read more.

Microorganisms in sediments are an important part of the aquatic ecosystem, and their functional activities are sensitive to external environmental pressure. Shallow lakes are characterized by frequent sediment resuspension events, leading to large amounts of nutrients being released. However, information about the potential impacts of sediment resuspension events on the functional activities of microbial communities is limited. In this study, the responses of microbial carbon metabolism in sediments under different wind–wave disturbance were analyzed by BIOLOG ECO microplates. The results showed that under four disturbance conditions (wind speeds of 0, 1.60, 3.62, and 14.10 m/s), the total carbon metabolism function of the sediment microbial community (represented as average well-color development, AWCD) remained unchanged (p > 0.05), and the final total AWCD value stabilized at about 1.70. However, compared with the control group, some specific carbon sources (e.g., amines and carboxylic acids) showed significant changes (p < 0.05). We found that short-term (8 h) resuspension events did not affect the total carbon metabolism of sediment microbial communities, while it affected the microbial utilization ability of some specific types of carbon sources. For example, we found that the microbial utilization capacity of polymers in the 14.10 m/s group was the best. This study provides a new insight into the carbon cycle process of shallow lake sediments that resuspension events will affect the carbon cycle process of sediments. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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17 pages, 3040 KiB

Open AccessArticle

Spatiotemporal Variation in Relative Humidity in Guangdong, China, from 1959 to 2017

by Zhanming Liu, Hong Yang and Xinghu Wei

Water 2020, 12(12), 3576; https://doi.org/10.3390/w12123576 - 20 Dec 2020

Cited by 8 | Viewed by 3571

Abstract

Despite the marked influence of relative humidity (RH) on ecosystems and human society, the spatiotemporal pattern of RH is far from clearly understood. This study analyzed the spatiotemporal variation in RH in Guangdong Province, South China, in the period of 1959–2017. The RH [...] Read more.

Despite the marked influence of relative humidity (RH) on ecosystems and human society, the spatiotemporal pattern of RH is far from clearly understood. This study analyzed the spatiotemporal variation in RH in Guangdong Province, South China, in the period of 1959–2017. The RH data were collected from 74 national standard meteorological stations. The spatiotemporal variation in RH was evaluated using rotate empirical orthogonal function (REOF) zoning, Mann–Kendall test, and wavelet transform methods. Based on the REOF decomposition situation of monthly RH field, Guangdong was divided into six subareas. The annual mean of RH in the whole province was 78.90%. In terms of spatial variation, overall annual mean RH decreased from southwest to northeast in the province. Temporally, annual mean RH showed a declining trend in the last six decades. Particularly, the RH in the Pearl River Delta area declined at the rate of 1.349%/10a. Mann–Kendall tests showed that mutation points of annual mean RH mostly appeared in the 1990s, especially in the early 1990s. Continuous wavelet transforms of annual mean RH displayed that inland subareas have similar cycle characteristics, and the east coast and Pearl River Delta have no significant period in most time domains. The results provide new understanding of RH variation in the last six decades in South China, which is valuable for detecting climate change, monitoring hazardous weather, and predicting future environmental change. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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19 pages, 4351 KiB

Open AccessEditor’s ChoiceArticle

Spatiotemporal Analysis of Water Quality Using Multivariate Statistical Techniques and the Water Quality Identification Index for the Qinhuai River Basin, East China

by Xiaoxue Ma, Lachun Wang, Hong Yang, Na Li and Chang Gong

Water 2020, 12(10), 2764; https://doi.org/10.3390/w12102764 - 4 Oct 2020

Cited by 44 | Viewed by 5634

Abstract

Monitoring water quality is indispensable for the identification of threats to water environment and later management of water resources. Accurate monitoring and assessment of water quality have been long-term challenges. In this study, multivariate statistical techniques (MST) and water quality identification index (WQII) [...] Read more.

Monitoring water quality is indispensable for the identification of threats to water environment and later management of water resources. Accurate monitoring and assessment of water quality have been long-term challenges. In this study, multivariate statistical techniques (MST) and water quality identification index (WQII) were applied to analyze spatiotemporal variation in water quality and determine the major pollution sources in the Qinhuai River, East China. A rotated principal component analysis (PCA) identified three potential pollution sources during the wet season (mixed pollution, physicochemical, and nonpoint sources of nutrients) and the dry season (nutrient, primary environmental, and organic sources) and they explained 81.14% of the total variances in the wet season and 78.42% of total variances in the dry season. The result of redundancy analysis (RDA) showed that population density, urbanization, and wastewater discharge are the main sources of organic pollution, while agricultural fertilizer consumption and industrial wastewater discharge are the main sources of nutrients such as nitrogen and phosphorus. The water quality of the Qinhuai River basin was determined to be mainly Class III (slightly polluted) and Class IV (moderately polluted) based on WQII. Temporally, the change trend of WQII showed that water quality gradually deteriorated between 1990 and 2005, improved between 2006 and 2010, and then deteriorated again. Spatially, the WQII distribution map showed that areas with more developed urbanization were relatively more polluted. Our results show that MST and WQII are useful tools to help the public and decision makers to evaluate the water quality of aquatic environment. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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19 pages, 6507 KiB

Open AccessArticle

Spatiotemporal Variation in Precipitation during Rainy Season in Beibu Gulf, South China, from 1961 to 2016

by Zhanming Liu, Hong Yang and Xinghu Wei

Water 2020, 12(4), 1170; https://doi.org/10.3390/w12041170 - 19 Apr 2020

Cited by 8 | Viewed by 3216

Abstract

The spatiotemporal variation in precipitation is an important part of water cycle change, which is directly associated with the atmospheric environment and climate change. The high-resolution spatiotemporal change of precipitation is still unknown in many areas despite its importance. This study analyzed the [...] Read more.

The spatiotemporal variation in precipitation is an important part of water cycle change, which is directly associated with the atmospheric environment and climate change. The high-resolution spatiotemporal change of precipitation is still unknown in many areas despite its importance. This study analyzed the spatiotemporal variation in precipitation in Beibu Gulf, South China, during the rainy season (from April to September) in the period of 1961–2016. The precipitation data were collected from 12 national standard rain-gauge observation stations. The spatiotemporal variation in precipitation was evaluated with incidence rate and contribution rate of precipitation. The tendency of variations was analyzed using the Mann–Kendall method. The precipitation in the rainy season contributed 80% to the total annual precipitation. In general, there was an exponential decreasing tendency between the precipitation incidence rate and increased precipitation durations. The corresponding contribution rate showed a downward trend after an initial increase. The precipitation incidence rate decreased with the rising precipitation grades, with a gradual increase in contribution rate. The precipitation incidence rate and contribution rate of 7–9 d durations showed the significant downward trends that passed the 95% level of significance test. The results provide a new understanding of precipitation change in the last five decades, which is valuable for predicting future climate change and extreme weather prevention and mitigation. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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17 pages, 3569 KiB

Open AccessArticle

Spatial Variation in Aragonite Saturation State and the Influencing Factors in Jiaozhou Bay, China

by Yunxiao Li, Longjun Zhang, Liang Xue, Wenhua Fan, Fenwu Liu and Hong Yang

Water 2020, 12(3), 825; https://doi.org/10.3390/w12030825 - 14 Mar 2020

Cited by 13 | Viewed by 3983

Abstract

Both natural processes and human activities affect seawater calcium carbonate saturation state (Ω_arag), while the mechanisms are still far from being clearly understood. This study analysed the seawater surface Ω_arag during summer and winter in Jiaozhou Bay (JZB), China, based [...] Read more.

Both natural processes and human activities affect seawater calcium carbonate saturation state (Ω_arag), while the mechanisms are still far from being clearly understood. This study analysed the seawater surface Ω_arag during summer and winter in Jiaozhou Bay (JZB), China, based on two cruises observations performed in January and June 2017. The ranges of Ω_arag values were 1.55~2.92 in summer and 1.62~2.15 in winter. Regression analyses were conducted to identify the drivers of the change of Ω_arag distribution, and then the relative contributions of temperature, mixing processes and biological processes to the spatial differences in Ω_arag were evaluated by introducing the difference between total alkalinity (TA) and dissolved inorganic carbon (DIC) as a proxy for Ω_arag. The results showed that biological processes were the main factor affecting the spatial differences in Ω_arag, with relative contributions of 70% in summer and 50% in winter. The contributions of temperature (25% in summer and 20% in winter) and the mixing processes (5% in summer and 30% in winter) were lower. The increasing urbanization in offshore areas can further worsen acidification, therefore environmental protection in both offshore and onshore is needed. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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Review

Jump to: Research

16 pages, 12277 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Use of Constructed Wetland for Mitigating Nitrogen and Phosphorus from Agricultural Runoff: A Review

by Jiayu Li, Bohong Zheng, Xiao Chen, Zhe Li, Qi Xia, Hua Wang, Yuan Yang, Yaoyu Zhou and Hong Yang

Water 2021, 13(4), 476; https://doi.org/10.3390/w13040476 - 12 Feb 2021

Cited by 41 | Viewed by 11254

Abstract

The loss of nitrogen and phosphate fertilizers in agricultural runoff is a global environmental problem, attracting worldwide attention. In the last decades, the constructed wetland has been increasingly used for mitigating the loss of nitrogen and phosphate from agricultural runoff, while the substrate, [...] Read more.

The loss of nitrogen and phosphate fertilizers in agricultural runoff is a global environmental problem, attracting worldwide attention. In the last decades, the constructed wetland has been increasingly used for mitigating the loss of nitrogen and phosphate from agricultural runoff, while the substrate, plants, and wetland structure design remain far from clearly understood. In this paper, the optimum substrates and plant species were identified by reviewing their treatment capacity from the related studies. Specifically, the top three suitable substrates are gravel, zeolite, and slag. In terms of the plant species, emergent plants are the most widely used in the constructed wetlands. Eleocharis dulcis, Typha orientalis, and Scirpus validus are the top three optimum emergent plant species. Submerged plants (Hydrilla verticillata, Ceratophyllum demersum, and Vallisneria natans), free-floating plants (Eichhornia crassipes and Lemna minor), and floating-leaved plants (Nymphaea tetragona and Trapa bispinosa) are also promoted. Moreover, the site selection methods for constructed wetland were put forward. Because the existing research results have not reached an agreement on the controversial issue, more studies are still needed to draw a clear conclusion of effective structure design of constructed wetlands. This review has provided some recommendations for substrate, plant species, and site selections for the constructed wetlands to reduce nutrients from agricultural runoff. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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20 pages, 1619 KiB

Open AccessFeature PaperReview

A Critical Review of Methods for Analyzing Freshwater Eutrophication

by Yan Zhang, Mingxuan Li, Jiefeng Dong, Hong Yang, Lukas Van Zwieten, Hui Lu, Aref Alshameri, Zihan Zhan, Xin Chen, Xueding Jiang, Weicheng Xu, Yanping Bao and Hailong Wang

Water 2021, 13(2), 225; https://doi.org/10.3390/w13020225 - 18 Jan 2021

Cited by 61 | Viewed by 12715

Abstract

Water eutrophication is a global environmental problem that poses serious threats to aquatic ecosystems and human health. The evaluation of eutrophication provides a theoretical basis and technical guidance for the management and rehabilitation of water ecosystems. In the last four decades, dozens of [...] Read more.

Water eutrophication is a global environmental problem that poses serious threats to aquatic ecosystems and human health. The evaluation of eutrophication provides a theoretical basis and technical guidance for the management and rehabilitation of water ecosystems. In the last four decades, dozens of evaluation methods have been applied to freshwater eutrophication, but there is a clear need to optimize and standardize the most suitable methods. We have addressed this gap by presenting a systematic review of methodologies. Due to the diversity and complexity of water bodies, no single evaluation method was identified that would adequately represent eutrophication under all scenarios. We demonstrate that lakes can best be assessed using the trophic level index (TLI) method, reservoirs and wetlands the trophic state index (TSI) and fuzzy comprehensive evaluation (FCE) method, respectively, and rivers the FCE method or back propagation (BP) neural network methods. More recently applied methodologies including spectral imaging and 3-D mapping of water quality using underwater gliders allow greater resolution and can be effective in managing waterbodies to avoid future eutrophication. The aim of this review is to guide future studies on the most appropriate methods available for assessing and reporting water eutrophication. Full article

(This article belongs to the Special Issue The Impact of Climate Change and Human Activities on Aquatic Environments)

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