Root Disturbance Effects of Four Halophytes on Soil Physiochemical Charismatics in Intertidal Ecotone of the Yellow River Estuary

Four representative halophytes, Tamarix chinensis (Tc), Phragmites australis (Pa), Suaeda salsa (Ss), and Spartina alterniflora (Sa), in the Yellow River Estuary wetland were selected to clarify the root disturbance on soil nutrient elements, salt ions, and their stoichiometric ratios. The results showed that the average total organic carbon (TOC) content of Tc, Pa, Ss, and Sa in the rhizosphere (RS) group was 5.19, 2.15, 2.05, and 2.14 times higher than those in the non-rhizosphere (CK) group, respectively. The total nitrogen (TN) content of Tc in the RS group was about 3.44 times that of the CK group. The average soil salinity reduced by 41.35%, due to the root disturbance of Tc. Soil ions, including K+, Ca2+, Mg2+, Na+, Cl-, and SO42- reduced by 33.86-62.86%. The root disturbance of Pa reduced soil salinity and soil ions by 35.47% and 16.93%-46.85%, respectively. However, the root disturbance effects in Sa and Ss were not obvious. The disturbance of roots played a crustal role in affecting the spatial heterogeneity of soil properties in the coastal wetlands above the intertidal zone (Tc and Pa), but its effect was greatly weakened below the intertidal zone (Sa and Ss). These findings are important for understanding how halophytes can impact soil nutrient levels and salt concentrations in coastal wetlands, which is crucial for effective management and restoration

Root Disturbance Effects of Four Halophytes on Soil Physiochemical Charismatics in Intertidal Ecotone of the Yellow River Estuary

Four representative halophytes, Tamarix chinensis (Tc), Phragmites australis (Pa), Suaeda salsa (Ss), and Spartina alterniflora (Sa), in the Yellow River Estuary wetland were selected to clarify the root disturbance on soil nutrient elements, salt ions, and their stoichiometric ratios. The results showed that the average total organic carbon (TOC) content of Tc, Pa, Ss, and Sa in the rhizosphere (RS) group was 5.19, 2.15, 2.05, and 2.14 times higher than those in the non-rhizosphere (CK) group, respectively. The total nitrogen (TN) content of Tc in the RS group was about 3.44 times that of the CK group. The average soil salinity reduced by 41.35%, due to the root disturbance of Tc. Soil ions, including K+, Ca2+, Mg2+, Na+, Cl-, and SO42- reduced by 33.86-62.86%. The root disturbance of Pa reduced soil salinity and soil ions by 35.47% and 16.93%-46.85%, respectively. However, the root disturbance effects in Sa and Ss were not obvious. The disturbance of roots played a crustal role in affecting the spatial heterogeneity of soil properties in the coastal wetlands above the intertidal zone (Tc and Pa), but its effect was greatly weakened below the intertidal zone (Sa and Ss). These findings are important for understanding how halophytes can impact soil nutrient levels and salt concentrations in coastal wetlands, which is crucial for effective management and restoration

Impacts of inland pollution input on coastal water quality of the Bohai Sea

Inland pollutants input is a key impact factor for the coastal water quality of the Bohai Sea. The coastal and inland water pollutant inputs were analyzed by using monitoring data of recent years from the State Oceanic Administration. The results showed that more than 56% of the Bohai Sea area was unclean seawater in 2012, although the water quality improved gradually after that time. In 2017, about one-third of the Bohai Sea area still had unclean seawater. Inorganic nitrogen, reactive phosphate, and petroleum hydrocarbons are the main pollutants in the seawater. A total of approximately 840,000 t of pollutants was transported to the sea each year by major rivers during 2010-2017. Significant correlations (p < 0.05) were found between the third-grade level seawater area and the pollutants of CODcr, petroleum, NO3--N, NH4+-N, NO2--N, Cu, and Pb and between the inferior fourth-grade level seawater area and the pollutants of petroleum, NO2--N, Pb, and NO3--N. The standard discharge rate of terrestrial-source sewage outlets was no more than 50%. The low standard discharge rate of the major terrestrial-source sewage pollutants of CODcr, NH4+-N, TP, BOD5, and SS caused more than 80% of the monitored sea areas adjacent to the selected key sewage outlets to not meet the water quality requirements of the marine functional area. The results suggest that implementing a coastal water management plan is necessary to reduce the heavy ecological burdens on the coastal zone of the Bohai Sea. (C) 2020 Elsevier B.V. All rights reserved

Environmental threats induced heavy ecological burdens on the coastal zone of the Bohai Sea, China

The environment of the Bohai Sea is under enormous pressure because of rapid economic and urban development associated with increased population inhabiting the coastal zone. Environmental threats to the coastal ecosystem were analyzed using 2006-2017 statistical/monitoring data from the State Oceanic Administration, China. The results showed that harmful algal blooms occurred a total of 104 times during the period of 2006-2017, for a cumulative area of more than 21,275 km(2). The main environmental threats came from offshore oil and gas production in the form of hydrocarbon pollution during extraction, as well as from urban wastewater and sewage. Oil pollution, mainly generated from spills, offshore oil platforms and large number of vessels/ports, was found to cause very severe negative impacts on the environment. Another threat is from excessive ground-water exploitation which has resulted in seawater intrusion and soil salinization occurrence in more than 90% of coastal areas around the Bohai Sea. The maximum distance of intrusion by seawater and soil salinization was more than 40 and 32 km inland, respectively. Contamination by terrestrial pollutants was identified as another threat affecting the environment quality of the Bohai Sea. Approximately 840,000 t of pollutants were carried into the sea by major rivers annually for 2010-2017. The standard discharge rate of terrestrial-source sewage outlets did not exceed 50%; however, only 13.12% of sea areas adjacent to sewage outlets (rivers) met the environmental quality requirements for functional marine areas. The results also showed the frequency of storm surges in the Bohai Sea which was 8.83 times per year and the resulting annual direct economic losses reached (RMB) 1.77 billion for 2006-2017. The results highlight the urgent need to implement an ecological management strategy to reduce the heavy ecological burdens in the coastal zone of the Bohai Sea. (C) 2020 Elsevier B.V. All rights reserved

A Comparison of the Development of Wetland Restoration Techniques in China and Other Nations

Based on retrieved results of literature and patents related to international wetland ecological restoration, the current status and development of ecological restoration techniques for degraded wetlands in both China and international states were analyzed synthetically. The results showed that the United States was the pioneering country in studies on the wetland ecological restoration, while China began to pay widespread attention from 2000. Compared to the international developed countries, the start time of concern for wetland ecological restoration in China was about 10 years later. The phytoremediation and engineering restoration were the most popular among all the wetland ecological restoration techniques. Besides the United States, the number of publications increased most quickly in China since 2004. The Louisiana State University published most of the researching findings among the international institutions related to wetland ecological restoration. The Chinese Academy of Sciences was the most important institution for wetland restoration study in China. The analysis of the wetland ecological restoration practice in China and international states indicated that the study and application of combined bioremediation techniques would receive more attention for wetland ecological restoration in the future

Influence of Gate Dams on Yellow River Delta Wetlands

Nested Delft 3D and Hydrus 1D models were applied to simulate variations in the hydrological process of tidal creeks, soil water, and salt transport in the soil profile of the reconstruction area in the Yellow River Delta under six gate dam scenarios. The results showed that the gate dam set up near the sea area was more conducive to reducing the variation range of water depth in the reconstruction area. The water depth changes in scenarios with 6 m gate valves were higher than those with 3 m sluice valves in the same gate dam location. The variations in surface water salinity, cumulative flooding time, flooding frequency, and cumulative infiltration in each scenario were similar to those for water depth. Rapid changes in soil water and salt content occurred in each scenario in periods without flooding. The fluctuation of soil salt content in different soil layers was contrary to the changes in soil water content. The overall difference in the soil salt contents and soil water content of the soil profile in scenarios with a gate dam near the sea was relatively larger than that of those with a gate dam near the shore. Obvious differences in both the soil water content and soil salt content between scenarios with 3 m and 6 m gate valves were not observed. Our results contribute to the understanding of the function of gate dams in controlling soil water and salt content in coastal wetlands