2018 Vol. 40, No. 7
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2018, 40(7): .
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2018, 40(7): .
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2018, 40(7): 1-21.
doi: 10.3969/j.issn.0253-4193.2018.07.001
Abstract:
Foreign scientists firstly began to examine the delta of the estury of Zhujiang River along with the invasion of powers and the input of theory and technique of modern natural science into China. Then local scientists mastered and developed the associated knowledge and started the research of the natural entity. There are 6 leaps in the cognition of the Zhujiang River Estury. In 1915, W.Olivercrona wrote paper to call it "Guangzhou Delta" after field investigation and first proposed the concept of "Zhujiang River Delta", which is looked as the first leap. The second leap is made by Wu Shangshi, who discovered the geomorphology of sets of ancient sea cliff-sea cave-wave erosion platform and ancient sandbank-dried lagoon in the suburb of Guangzhou in 1937. In the academic debate of the presence of the Zhujiang River Delta, he supported the opinion that the seawater had been transgressioned into ancient estuary and developed delta. He wrote papers in 1941 and in 1947 to affirm the existence of the Zhujiang River Delta and determined its range. The third leap is created by Zeng Zhaoxuan, who proposed the development pattern of beading gap-cut deltas in 1980. He explained the special-time location of the the Zhujiang River Delta according to his creative study of historical morphology. The forth leap is in 1982, when Zhao Huanting revealed that the Zhujiang River Delta overlaid on old delta formed in the later period of later Pleistocene and modern delta forming in the middle Holocene, on the base of Wu Wenzhong's discovery about weathered granophyric ancient estuarine facies clay layer buried in the Zhujiang River Delta. New datum displayed the older delta formed in the middle period of later Pleistocene. The fifth leap is also marked by Zhao Huanting. In 1973-1982,he found the Zhujiang River Estury zone is distinct because river network in delta and residual estuary co-existed. He was one of the first scientists to study riverbed evolution of Zhujiang distributaries in the Shiziyang Distributary, estuary evolution in the Lingdingyang Estuary, and the distributaries mouth evolution in Modaomen distributary mouth. He used Simmons's concept of dominant flows and theory of estuary salt water wedge to study the morphological development and evolution of the distributary mouth and estuary. In 1990 he preliminarily summarized the evolution process of the Zhujiang River Estuary. The sixth leap is from Wu Chaoyu, who quantitatively reappeared the mosaic evolutionary process of the Zhujiang River Delta from 6 ka BP to 2.5 ka BP, according to the mutual confirmation of sedimentology, geomorphydynamics and his long-period mechanism model in 2006.
Foreign scientists firstly began to examine the delta of the estury of Zhujiang River along with the invasion of powers and the input of theory and technique of modern natural science into China. Then local scientists mastered and developed the associated knowledge and started the research of the natural entity. There are 6 leaps in the cognition of the Zhujiang River Estury. In 1915, W.Olivercrona wrote paper to call it "Guangzhou Delta" after field investigation and first proposed the concept of "Zhujiang River Delta", which is looked as the first leap. The second leap is made by Wu Shangshi, who discovered the geomorphology of sets of ancient sea cliff-sea cave-wave erosion platform and ancient sandbank-dried lagoon in the suburb of Guangzhou in 1937. In the academic debate of the presence of the Zhujiang River Delta, he supported the opinion that the seawater had been transgressioned into ancient estuary and developed delta. He wrote papers in 1941 and in 1947 to affirm the existence of the Zhujiang River Delta and determined its range. The third leap is created by Zeng Zhaoxuan, who proposed the development pattern of beading gap-cut deltas in 1980. He explained the special-time location of the the Zhujiang River Delta according to his creative study of historical morphology. The forth leap is in 1982, when Zhao Huanting revealed that the Zhujiang River Delta overlaid on old delta formed in the later period of later Pleistocene and modern delta forming in the middle Holocene, on the base of Wu Wenzhong's discovery about weathered granophyric ancient estuarine facies clay layer buried in the Zhujiang River Delta. New datum displayed the older delta formed in the middle period of later Pleistocene. The fifth leap is also marked by Zhao Huanting. In 1973-1982,he found the Zhujiang River Estury zone is distinct because river network in delta and residual estuary co-existed. He was one of the first scientists to study riverbed evolution of Zhujiang distributaries in the Shiziyang Distributary, estuary evolution in the Lingdingyang Estuary, and the distributaries mouth evolution in Modaomen distributary mouth. He used Simmons's concept of dominant flows and theory of estuary salt water wedge to study the morphological development and evolution of the distributary mouth and estuary. In 1990 he preliminarily summarized the evolution process of the Zhujiang River Estuary. The sixth leap is from Wu Chaoyu, who quantitatively reappeared the mosaic evolutionary process of the Zhujiang River Delta from 6 ka BP to 2.5 ka BP, according to the mutual confirmation of sedimentology, geomorphydynamics and his long-period mechanism model in 2006.
2018, 40(7): 22-37.
doi: 10.3969/j.issn.0253-4193.2018.07.002
Abstract:
From the perspective of interdisciplinary study, a brief review is conducted on the concept of "equilibrium" essential for the disciplines that the estuarine and coastal studies are closely related to. Based on output of the morphodynamic model PRD-LTMM, the water depth and corresponding area are selected as the state variables to construct the probability spaces that are used to calculate information entropy of the sub-delta systems. By comparing evolution of the depositional dynamic structures, which are briefly sketched in the context,and the geomorphic information entropy, it is found that the information entropy can be used as a phenomenological state function of the "morphodynamc equilibrium" in a given sense.
From the perspective of interdisciplinary study, a brief review is conducted on the concept of "equilibrium" essential for the disciplines that the estuarine and coastal studies are closely related to. Based on output of the morphodynamic model PRD-LTMM, the water depth and corresponding area are selected as the state variables to construct the probability spaces that are used to calculate information entropy of the sub-delta systems. By comparing evolution of the depositional dynamic structures, which are briefly sketched in the context,and the geomorphic information entropy, it is found that the information entropy can be used as a phenomenological state function of the "morphodynamc equilibrium" in a given sense.
2018, 40(7): 38-42.
doi: 10.3969/j.issn.0253-4193.2018.07.003
Abstract:
The P-A relationships of tidal inlets, the plan forms of shoreline, and the forms of offshore sand waves are analyzed as three coastal morphodynamic cases for the hydrodynamic, sedimentological and geomorphic systems. Along their equilibrium profiles, equal energy dissipation rate, equal increment in sediment transport rate, and equal sedimentary rate are arise together within large ranges of spatial and temporal scale. Such grading organised equilibrium statuses in the mixing fields among fluid mechanics, sediment dynamics, and morphodynamics, have been opened some valuable and clearly windows, research and practice, leading to cross-scale linkage and cross-scale modelling for the complex hydrodynamic, sedimentological and geomorphic systems.
The P-A relationships of tidal inlets, the plan forms of shoreline, and the forms of offshore sand waves are analyzed as three coastal morphodynamic cases for the hydrodynamic, sedimentological and geomorphic systems. Along their equilibrium profiles, equal energy dissipation rate, equal increment in sediment transport rate, and equal sedimentary rate are arise together within large ranges of spatial and temporal scale. Such grading organised equilibrium statuses in the mixing fields among fluid mechanics, sediment dynamics, and morphodynamics, have been opened some valuable and clearly windows, research and practice, leading to cross-scale linkage and cross-scale modelling for the complex hydrodynamic, sedimentological and geomorphic systems.
2018, 40(7): 43-54.
doi: 10.3969/j.issn.0253-4193.2018.07.004
Abstract:
A summer hydrologic survey in the Zhujiang River Estuary and its adjacent seas was performed in July and August, 2006. The survey data show that while a part of the diluted water from the Zhujiang River is transported eastwards by the overlying southwesterly monsoon, most of the diluted water is transported westwards off the coast of western Guangdong Province, and there is upwelling underlying the westwards spreading diluted water. In the existing modelling studies of the upwelling in the northern South China Sea, the upwelling does not occur off the Zhujiang River Estuary under the southwesterly monsoon, which demonstrates that the southwesterly monsoon should not be the major driving force of the upwelling off the Zhujiang River Estuary. As indicated by the distribution of sea water salinity and temperature, time series of currents from mooring observations and current fields from shipboard ADCP measurements, the major formation mechanism of upwelling ought to be:(1) the vertical gravitational circulations off the river mouth driven by the southwards spreading discharges; (2) the bottom boundary Ekman effect of the eastward coastal current beneath the density transition layer; and (3) the effect of mesoscale cool eddies among the diluted water bulges off the river mouths.
A summer hydrologic survey in the Zhujiang River Estuary and its adjacent seas was performed in July and August, 2006. The survey data show that while a part of the diluted water from the Zhujiang River is transported eastwards by the overlying southwesterly monsoon, most of the diluted water is transported westwards off the coast of western Guangdong Province, and there is upwelling underlying the westwards spreading diluted water. In the existing modelling studies of the upwelling in the northern South China Sea, the upwelling does not occur off the Zhujiang River Estuary under the southwesterly monsoon, which demonstrates that the southwesterly monsoon should not be the major driving force of the upwelling off the Zhujiang River Estuary. As indicated by the distribution of sea water salinity and temperature, time series of currents from mooring observations and current fields from shipboard ADCP measurements, the major formation mechanism of upwelling ought to be:(1) the vertical gravitational circulations off the river mouth driven by the southwards spreading discharges; (2) the bottom boundary Ekman effect of the eastward coastal current beneath the density transition layer; and (3) the effect of mesoscale cool eddies among the diluted water bulges off the river mouths.
2018, 40(7): 55-65.
doi: 10.3969/j.issn.0253-4193.2018.07.005
Abstract:
In this study, the temporal-spatial distribution patterns of residual water level under the influence of nonlinear tide-river interaction in the Modaomen Estuary was explored by means of a one-dimensional analytical model for tidal river hydrodynamics. Model results showed that the distribution patterns of residual water level were characterized by an apparent spring-neap cycle and a dry-flood change. In particular, for the dry season, the residual water level was featured by significant spring-neap cycle, with values ranging between 0 and 0.4 m. On the other hand, the magnitude of residual water level in the flood season is one-order larger than that in the dry season (ranging between 0 and 6 m) and is closely related to the freshwater discharge imposed at the upstream end. With analytical model, it is possible to decompose the residual water level into different components, linking to tide, river and tide-river interaction, respectively. It was shown that, during the dry season, the residual water level was mainly controlled by the tidal forcing in the downstream reach of the Modaomen Estuary, while it was impacted by both the tide and river flow in the upstream part. For the flood season, the model results showed that the residual water level was mainly determined by the river flow for the whole estuary.
In this study, the temporal-spatial distribution patterns of residual water level under the influence of nonlinear tide-river interaction in the Modaomen Estuary was explored by means of a one-dimensional analytical model for tidal river hydrodynamics. Model results showed that the distribution patterns of residual water level were characterized by an apparent spring-neap cycle and a dry-flood change. In particular, for the dry season, the residual water level was featured by significant spring-neap cycle, with values ranging between 0 and 0.4 m. On the other hand, the magnitude of residual water level in the flood season is one-order larger than that in the dry season (ranging between 0 and 6 m) and is closely related to the freshwater discharge imposed at the upstream end. With analytical model, it is possible to decompose the residual water level into different components, linking to tide, river and tide-river interaction, respectively. It was shown that, during the dry season, the residual water level was mainly controlled by the tidal forcing in the downstream reach of the Modaomen Estuary, while it was impacted by both the tide and river flow in the upstream part. For the flood season, the model results showed that the residual water level was mainly determined by the river flow for the whole estuary.
The formation and development of the deposition bodies and main channels in the Zhujiang River Delta
2018, 40(7): 66-78.
doi: 10.3969/j.issn.0253-4193.2018.07.006
Abstract:
A long-term morphdynamic model (PRD-LTMM) and a non-linear dynamics theory Lagrangian coherent structures were applied to study the formation and development of the deposition bodies and main channels in the Zhujiang River Delta. The results indicated that mainly due to the convoluted coastline and hundreds of rocky islands scattered in the paleo-estuarine bay, seven different dynamic zones were formed, and many different kinds of medium and small scale dynamic structures were generated, then caused a great deal of deposition bodies. Deposition bodies is the basic unit in the hierarchical deposition structure of the Zhujiang River Delta. The general evolution of the Zhujiang River Delta can be summarized as a number of relatively separate ‘filling up’ processes. With the continuous growth of the deposition bodies, the broad water body was funneled into the channel frame of the Zhujiang River Delta network, and a continuous delta plain was formed.
A long-term morphdynamic model (PRD-LTMM) and a non-linear dynamics theory Lagrangian coherent structures were applied to study the formation and development of the deposition bodies and main channels in the Zhujiang River Delta. The results indicated that mainly due to the convoluted coastline and hundreds of rocky islands scattered in the paleo-estuarine bay, seven different dynamic zones were formed, and many different kinds of medium and small scale dynamic structures were generated, then caused a great deal of deposition bodies. Deposition bodies is the basic unit in the hierarchical deposition structure of the Zhujiang River Delta. The general evolution of the Zhujiang River Delta can be summarized as a number of relatively separate ‘filling up’ processes. With the continuous growth of the deposition bodies, the broad water body was funneled into the channel frame of the Zhujiang River Delta network, and a continuous delta plain was formed.
2018, 40(7): 79-89.
doi: 10.3969/j.issn.0253-4193.2018.07.007
Abstract:
Coastal wetland is an interaction interface among terrestrial, ocean and atmosphere, and is sensitive to the responses of global change and anthropogenic impacts, and the sedimentary records in coastal wetland can be used to reveal the information of local environmental change and anthropogenic impacts. Analyzed results for the sediment core named QA, obtained by drilling in coastal wetland of west Qi'ao Island (QAI), indicate that the surrounding area of the QAI was estuarine environment during the mid-Holocene, and the sea-bed began to experience a slight accumulation. However, due to the extreme cold climate influence near 4 200 a BP, the sediment showed a coarsen trend. Since 2 500 a BP, the sedimentary environment near the QAI was stable except during the Little Ice Age (LIA). Based on the radioisotope dating (14C and 210Pb) and the inferring conclusions according to the sedimentary structure of the core and sediment grain size variation, the mean sedimentation rate since mid-Holocene was 0.29 cm/a, and the sedimentation rates in the stages of 4 160-2 500 a BP, 2 500 a BP-1488 AD, 1488-1893 AD, 1893-1986 AD, and since 1990 AD were 0.17 cm/a, 0.23 cm/a, 0.35 cm/a, 1.37 cm/a and 5.94 cm/a, respectively. The increase of sedimentation rate indicated the variation of sedimentary facies and sedimentaryenvironment during the formation and evolution of the Zhujiang River Delta. During 1986-1990, the construction of the seawall disturbed the sedimentary process immensely and induced a 112 cm sediment layer occurred near the seawall, and the sedimentation rate increased evidently after the construction of seawall. The depth-distribution of total organic carbon (TOC), total nitrogen (TN) and C/N ratio indicated that the organic carbon was composed mainly by marine source during 4 160-2 500 a BP because the sedimentary environment near the QAI was influenced by marine environment mainly; since 2 500 a BP, the contents of TOC and TN increased as well as the variation of the C/N ratio revealed that the organic carbon mainly came from terrestrial input, although the contribution of marine source increased slightly during the LIA; however, the contribution of terrestrial organic carbon increased remarkably in recent one hundred years due to the intense anthropogenic impacts in the catchment area of the Zhujiang River and surrounding area of the estuary.
Coastal wetland is an interaction interface among terrestrial, ocean and atmosphere, and is sensitive to the responses of global change and anthropogenic impacts, and the sedimentary records in coastal wetland can be used to reveal the information of local environmental change and anthropogenic impacts. Analyzed results for the sediment core named QA, obtained by drilling in coastal wetland of west Qi'ao Island (QAI), indicate that the surrounding area of the QAI was estuarine environment during the mid-Holocene, and the sea-bed began to experience a slight accumulation. However, due to the extreme cold climate influence near 4 200 a BP, the sediment showed a coarsen trend. Since 2 500 a BP, the sedimentary environment near the QAI was stable except during the Little Ice Age (LIA). Based on the radioisotope dating (14C and 210Pb) and the inferring conclusions according to the sedimentary structure of the core and sediment grain size variation, the mean sedimentation rate since mid-Holocene was 0.29 cm/a, and the sedimentation rates in the stages of 4 160-2 500 a BP, 2 500 a BP-1488 AD, 1488-1893 AD, 1893-1986 AD, and since 1990 AD were 0.17 cm/a, 0.23 cm/a, 0.35 cm/a, 1.37 cm/a and 5.94 cm/a, respectively. The increase of sedimentation rate indicated the variation of sedimentary facies and sedimentaryenvironment during the formation and evolution of the Zhujiang River Delta. During 1986-1990, the construction of the seawall disturbed the sedimentary process immensely and induced a 112 cm sediment layer occurred near the seawall, and the sedimentation rate increased evidently after the construction of seawall. The depth-distribution of total organic carbon (TOC), total nitrogen (TN) and C/N ratio indicated that the organic carbon was composed mainly by marine source during 4 160-2 500 a BP because the sedimentary environment near the QAI was influenced by marine environment mainly; since 2 500 a BP, the contents of TOC and TN increased as well as the variation of the C/N ratio revealed that the organic carbon mainly came from terrestrial input, although the contribution of marine source increased slightly during the LIA; however, the contribution of terrestrial organic carbon increased remarkably in recent one hundred years due to the intense anthropogenic impacts in the catchment area of the Zhujiang River and surrounding area of the estuary.
2018, 40(7): 90-102.
doi: 10.3969/j.issn.0253-4193.2018.07.008
Abstract:
Precipitation and evaporation data were used to investigate the annual distribution characteristics of precipitation, evaporation and net fresh water flux in the tropical Indian Ocean (TIO), then four typical areas were chosen to analyze the seasonal and interannual variation of precipitation, evaporation and net fresh water flux. The results suggest that the maximum annual precipitation appears in the western sea area of Sumatra in eastern Indian Ocean (EIO), which belongs to the rainy weather throughout the year with small seasonal variations; the higher annual precipitation is observed in the northeastern Bay of Bengal (BoB) and northern Andaman Sea, with the interannual variation rising by 4.2 mm per year, and the heavy rainfall falls in the period from May to September. The smaller annual precipitation was found in the western of Arabian Sea. The smaller annual precipitation and higher annual evaporation were found in the eastern sea area in the southern Indian Ocean(20°-30°S,80°-110°E) with the interannual variation increase by 5.1 mm per year before 2000 and decrease by 4.5 mm per year after 2000. The influence of precipitation and evaporation on sea surface salinity (SSS) is discussed by using the Argo salinity. Further analysis indicates that while rainfall is more (less) than evaporation, SSS becomes lower(higher). The inconsistency between the center of higher net freshwater flux (higher evaporation) and lower salinity (higher salinity) is mainly caused by surface horizontal circulation. The SSS seasonal variation has little relation with surface horizontal circulation, while it is highly related to net freshwater flux in the four chosen typical areas. The heavy precipitation has a remarkable influence on surface salinity in BoB. It can cause a decrease in SSS by 0.2-0.8 from 30 m to 50 m.
Precipitation and evaporation data were used to investigate the annual distribution characteristics of precipitation, evaporation and net fresh water flux in the tropical Indian Ocean (TIO), then four typical areas were chosen to analyze the seasonal and interannual variation of precipitation, evaporation and net fresh water flux. The results suggest that the maximum annual precipitation appears in the western sea area of Sumatra in eastern Indian Ocean (EIO), which belongs to the rainy weather throughout the year with small seasonal variations; the higher annual precipitation is observed in the northeastern Bay of Bengal (BoB) and northern Andaman Sea, with the interannual variation rising by 4.2 mm per year, and the heavy rainfall falls in the period from May to September. The smaller annual precipitation was found in the western of Arabian Sea. The smaller annual precipitation and higher annual evaporation were found in the eastern sea area in the southern Indian Ocean(20°-30°S,80°-110°E) with the interannual variation increase by 5.1 mm per year before 2000 and decrease by 4.5 mm per year after 2000. The influence of precipitation and evaporation on sea surface salinity (SSS) is discussed by using the Argo salinity. Further analysis indicates that while rainfall is more (less) than evaporation, SSS becomes lower(higher). The inconsistency between the center of higher net freshwater flux (higher evaporation) and lower salinity (higher salinity) is mainly caused by surface horizontal circulation. The SSS seasonal variation has little relation with surface horizontal circulation, while it is highly related to net freshwater flux in the four chosen typical areas. The heavy precipitation has a remarkable influence on surface salinity in BoB. It can cause a decrease in SSS by 0.2-0.8 from 30 m to 50 m.
2018, 40(7): 103-115.
doi: 10.3969/j.issn.0253-4193.2018.07.009
Abstract:
Using the oxygen isotope stratigraphy method to establish the age mode of core DLW3101.The bottom of the core is about 306 ka old. Based on this age mode the sediments were used to make grain-size and XRF element scanning test. The conclusion shows that high values of 22.1-63 μm grades may reveal the enhancement of East Asian winter monsoon and the decline of the sea level. High values of 0.35-1.16 μm and 2.32-13.14 μm grades may reveal the enhancement of East Asian summer monsoon and the rise of the sea level. Al/Ti and K/Ti ratio are adopted to reflect chemical weathering degree of sediments source area in order to reveal the strength of East Asian summer monsoon.
Using the oxygen isotope stratigraphy method to establish the age mode of core DLW3101.The bottom of the core is about 306 ka old. Based on this age mode the sediments were used to make grain-size and XRF element scanning test. The conclusion shows that high values of 22.1-63 μm grades may reveal the enhancement of East Asian winter monsoon and the decline of the sea level. High values of 0.35-1.16 μm and 2.32-13.14 μm grades may reveal the enhancement of East Asian summer monsoon and the rise of the sea level. Al/Ti and K/Ti ratio are adopted to reflect chemical weathering degree of sediments source area in order to reveal the strength of East Asian summer monsoon.
2018, 40(7): 116-133.
doi: 10.3969/j.issn.0253-4193.2018.07.010
Abstract:
Shenhu area of South China Sea is one of the most important research areas for natural gas hydrate in China. Geochemical and mineralogical characteristics were investigated in ten sediment samples, which included the sediments of gas-hydrate-bearing layer, collected from W19B site in Shenhu area. Analyses of major elements and X-ray diffraction indicated that several layers contained pyrite with unusual high content. The SEM images revealed that the pyrite crystals became more euhedral and the morphology varied from aggregate framboids to single framboid and finally tiny grain types as sediment depth increased, and some intermediate products in the textural evolution were also identified. Both 53.0 mbsf (meters below seafloor) and 140.4 mbsf layers were observed with significant abundances of pyrite. At the 140.4 mbsf layer, pyrite filling the chamber of the foraminifer shell was common and coupled with a large amount of columnar pyrite, which might be related to the anaerobic oxidation of organic matter and methane, especially with the anaerobic oxidation of methane (AMO). The layer of 140.4 mbsf might be close to the paleo sulfate-methane interface (SMI). Based on the results obtained, it is proposed that anomaly high AMO derived pyrites around 53.0 mbsf and 140.4 mbsf were probably related to the high methane flux, which might be resulted from the unusual methane events. The presence of several high pyrite layers might be related to the multi-stage methane events which might be caused by tectonic activities or the decompositions of gas hydrate in the depositional history.
Shenhu area of South China Sea is one of the most important research areas for natural gas hydrate in China. Geochemical and mineralogical characteristics were investigated in ten sediment samples, which included the sediments of gas-hydrate-bearing layer, collected from W19B site in Shenhu area. Analyses of major elements and X-ray diffraction indicated that several layers contained pyrite with unusual high content. The SEM images revealed that the pyrite crystals became more euhedral and the morphology varied from aggregate framboids to single framboid and finally tiny grain types as sediment depth increased, and some intermediate products in the textural evolution were also identified. Both 53.0 mbsf (meters below seafloor) and 140.4 mbsf layers were observed with significant abundances of pyrite. At the 140.4 mbsf layer, pyrite filling the chamber of the foraminifer shell was common and coupled with a large amount of columnar pyrite, which might be related to the anaerobic oxidation of organic matter and methane, especially with the anaerobic oxidation of methane (AMO). The layer of 140.4 mbsf might be close to the paleo sulfate-methane interface (SMI). Based on the results obtained, it is proposed that anomaly high AMO derived pyrites around 53.0 mbsf and 140.4 mbsf were probably related to the high methane flux, which might be resulted from the unusual methane events. The presence of several high pyrite layers might be related to the multi-stage methane events which might be caused by tectonic activities or the decompositions of gas hydrate in the depositional history.
2018, 40(7): 134-142.
doi: 10.3969/j.issn.0253-4193.2018.07.011
Abstract:
The air water interface is an important interface where material exchanges, it has important influence on ecosystem and biogeochemical cycle. The rain can change the balance of interface, improve the exchange rate of gas flux, and make the distribution of dissolved oxygen and pH of the interface change in horizontal and vertical direction. Based on planar sensing film with highly spatial and temporal resolution, which can provide the characteristics of two-dimensional distribution information, we carry out the simulation experiment of raindrops about oxygen and pH distribution in air-water interface by using double parameters planar optode. The results show that rainfall process plays an important role in adjusting dissolved oxygen and pH of the surface water, the raindrop can break the balance of micro surface of water-gas interface mechanism, and promote the dissolution of oxygen in the atmosphere in water to make a average increase of about 2.3 mg/L in vertical direction 23 mm. The impact of rainfall on pH of the water surface within 12 mm is relatively obvious, the pH value decreased by an average of 0.2-0.4 units, indicating that the raindrop promoted the migration of the atmosphere in the air-water interface, and the dissolved CO2 caused the surface water acidification. This study provides a new technical method for understanding the influence of raindrops on the dissolved oxygen concentration and pH of the surface water in low wind impacting area and static water area.
The air water interface is an important interface where material exchanges, it has important influence on ecosystem and biogeochemical cycle. The rain can change the balance of interface, improve the exchange rate of gas flux, and make the distribution of dissolved oxygen and pH of the interface change in horizontal and vertical direction. Based on planar sensing film with highly spatial and temporal resolution, which can provide the characteristics of two-dimensional distribution information, we carry out the simulation experiment of raindrops about oxygen and pH distribution in air-water interface by using double parameters planar optode. The results show that rainfall process plays an important role in adjusting dissolved oxygen and pH of the surface water, the raindrop can break the balance of micro surface of water-gas interface mechanism, and promote the dissolution of oxygen in the atmosphere in water to make a average increase of about 2.3 mg/L in vertical direction 23 mm. The impact of rainfall on pH of the water surface within 12 mm is relatively obvious, the pH value decreased by an average of 0.2-0.4 units, indicating that the raindrop promoted the migration of the atmosphere in the air-water interface, and the dissolved CO2 caused the surface water acidification. This study provides a new technical method for understanding the influence of raindrops on the dissolved oxygen concentration and pH of the surface water in low wind impacting area and static water area.
2018, 40(7): 143-149.
doi: 10.3969/j.issn.0253-4193.2018.07.012
Abstract:
Multi-beam backscatter strengths (BS) are widely applied in many fields. The sonar image often has low quality caused by the impact of angular response (AR), and due to the poor adaptation of existing AR correction model in complex submarine environment, two kinds of BS normalization methods are proposed to solve the AR influence, namely Gaussian Fitting correction and AR correction. Where, the former is based on the BS regulation and the latter is based on the acoustic scattering mechanism. The experimental results showed that the accuracy of the two methods was about 30% higher than that with the default correction method, and the AR correction method is more accurate than the gauss fitting correction method, but the calculation efficiency was decreased. The above results verify the effectiveness of the two methods, and the normalization of BS is realized and improve the quality of sonar images.
Multi-beam backscatter strengths (BS) are widely applied in many fields. The sonar image often has low quality caused by the impact of angular response (AR), and due to the poor adaptation of existing AR correction model in complex submarine environment, two kinds of BS normalization methods are proposed to solve the AR influence, namely Gaussian Fitting correction and AR correction. Where, the former is based on the BS regulation and the latter is based on the acoustic scattering mechanism. The experimental results showed that the accuracy of the two methods was about 30% higher than that with the default correction method, and the AR correction method is more accurate than the gauss fitting correction method, but the calculation efficiency was decreased. The above results verify the effectiveness of the two methods, and the normalization of BS is realized and improve the quality of sonar images.
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