Comparative Study of the Physicochemical Quality of the Waters of the Méné River (Sassandra Watershed, Ivory Coast) in the Dry Season and in the Rainy Season

The study carried out on the waters of the Méné River led to an overall assessment of its water quality during the dry season and the rainy season. The analysis focused on eight (8) water samples taken from the river during a period of dry season (January-February) and a period of rainy season (June and September). The various physicochemical parameters were measured according to Afnor standardized methods. The readings of temperature, turbidity, pH and conductivity made it possible to account for the disturbances occurring in water quality. A temporal variation correlated with the seasons (dry or rainy) is noted. Turbidity depends on the concentration of suspended solids (SS) in the water and drained particles and therefore on the seasons. Just like the temperature, the conductivity changes with the season. The waters of the Méné River are generally acidic. The results obtained show that there is a low level of pollution by chlorides, phosphates, nitrites and nitrates. A slight pollution of the waters of Méné in organic matter (chemical oxygen demand values are less than 25 mg∙L−1 during dry season and 32.33 ± 4.73 mg∙L−1 during rainy season) was observed. The concentrations of metallic trace elements such as iron, manganese and aluminum indicate significant pollution of these waters by these elements. Overall, the waters of the Méné River are of satisfactory quality because all the physicochemical parameters analyzed have values below standards during the dry season as well as during the rainy season with the exception of COD and a few metallic trace elements.

Functional groups and seasonal diversity of crustacean zooplankton in adjacent waters of Haizhou Bay,South Yellow Sea

Zooplankton are important linkages in the food web and can respond nonlinearly to environmental changes.Marine organisms thrive from spring to summer.Thus,it is crucial to understand how ecological functions of zooplankton communities may shift under seasonal environmental changes during this period.Samples were collected from May to August(May,June-Ⅰ,June-Ⅱ,July-Ⅰ,July-Ⅱ,and August)in 2018 in Haizhou Bay,Jiangsu,East China for zooplankton and environmental variables.Crustaceans accounted for 75 out of 134 zooplankton taxa and 91.8%of total zooplankton abundance.The average abundance of crustacean varied between 2824.6±635.4 inds./m3 in July-Ⅱand 6502.7±1008.8 inds./m3 in June-Ⅱ.Multivariate analyses results showed that the dissimilarity of community increased gradually in the time series.Body length,feeding type,trophic group,and reproduction mode were used to investigate crustacean community functions.Trait-based functional groups contained species with similar ecological roles.Functional diversity fused the differences of species and trait.The proportion of large-sized species(2-5 mm)decreased with the increasing proportion of medium-sized species(1-2 mm).The proportion of current feeders increased with the drop in the proportion of mixed feeders.Parthenogenesis species increased with decreasing free spawners,and omnivores-carnivores increased with decreasing omnivoresherbivores.Generalized additive models suggested that temperature was the main driver of variations in crustacean zooplankton function.Seven identified functional groups varied with increasing temperature.Omnivorous-herbivorous copepods declined(90.0%-68.0%),whereas the parthenogenetic cladocerans increased(0-24.1%).The small egg-brooding ambush copepods fluctuated(6.5%-9.3%)with increasing water temperature.The other functional groups changed slightly.Functional diversity also varied according to temperature changes.The community structure and ecological function of crustacean zooplankton community showed gradual changes with increasing temperature from spring to summer.

Characteristics of dissolved sugars in the Southern Yap Trench from sea surface to hadal zone

2,4,6-Tripyridine-s-triazine(TPTZ)spectrophotometric method was applied to determine the concentrations of dissolved monosaccharides(MCHO),polysaccharides(PCHO),and total carbohydrate(TCHO)in seawater samples collected from sea surface to hadal zone and sediment-seawater interface of the Southern Yap Trench in the Western Pacific Ocean.Results show that the concentrations of MCHO,PCHO,and TCHO ranged from 6.3 to 22.3μmol C/L,1.1 to 25.4μmol C/L,and 12.1 to 44.9μmol C/L,respectively,from the euphotic layer to the hadal zone of the trench.At different sampling stations,the concentrations of MCHO,PCHO,and TCHO in the seawater showed complex vertical variation characteristics,but the overall variation trends were decreasing with water depth.In the Southern Yap Trench,the maximum concentration of MCHO in the seawater appeared in the euphotic layer,and the minimum in the hadal zone.The maximum concentration of PCHO appeared in the euphotic layer,and the minimum in the bathypelagic layer.The water layer where the maxima and minima of the average concentration of TCHO appeared was consistent with that of PCHO.PCHO was the major component of TCHO in the seawater of the Southern Yap Trench.In the seawater from the sediment-seawater interface,the concentrations of MCHO,PCHO,and TCHO ranged from 8.4 to 10.6μmol C/L,3.8 to 5.8μmol C/L,and 12.2 to 15.2μmol C/L,respectively,and MCHO was the major component of TCHO.The key factors affecting the concentration and existing forms of dissolved sugars in the seawater of the Southern Yap Trench included photosynthesis,respiration,polysaccharide hydrolysis,adsorption and desorption of particulate matter,trench“funnel effect”,deep ocean currents,sediment resuspension,and etc.This study provided fundamental data about labile organic matter in abyss and hadal zone of marine environment,which is significant for further understanding of deep-sea organic carbon cycle.

Impacts of algal blooms on sinking carbon flux and hypoxia off the Changjiang River estuary

Based on 10 multidisciplinary investigations conducted from February 2015 to January 2016,the phytoplankton community and its association with ambient seawater physicochemical parameters in the Changjiang(Yangtze)River estuary(CE)and its adjacent waters were comprehensively examined.In total,265 taxa were identified,belonging to 5 phyla and 94 genera.Diatoms(63.78%)and dinoflagellates(33.21%)were the dominant groups.The variation of diatom abundance showed a positive relationship with the nutrient concentrations while the dinoflagellate abundance showed a negative relationship.Two algal bloom events occurred during the investigation period.The Changjiang Diluted Water(CDW)induced environmental gradients in the upper layer,favoring the diatom bloom in July.The invasion of the nearshore Kuroshio branch current could affect the formation of a bloom of Prorocentrum donghaiense.With the blooming and senescence of phytoplankton,low dissolved oxygen(DO)and hypoxia occurred in the bottom waters.The bottom DO concentration displayed a significantly negative correlation with phytoplankton carbon flux.The present study provides straightforward evidence for the source of organic matter for oxygen consumption in the CE and its adjacent waters.

Vertical variations and composition of dissolved free amino acid in the seawater of the Yap Trench in the western Pacific Ocean

The composition and concentration of dissolved free amino acid(DFAA)of seawater samples collected in May 2016 from the surface to the hadal zone of the northern region of the Yap Trench were analyzed by pre-column derivatization of o-phthalaldehyde.Results show that the average concentration of DFAA in the study area was 0.47±0.36μmol/L.In different sampling stations,the concentrations of DFAA with water depth showed complex variation patterns.At the sediment-seawater interface,the concentrations of DFAA in the western side of the trench were obviously higher than that in its eastern side.In the study area,there were no significant correlations between the concentrations of DFAA and the environmental parameters such as concentrations of chlorophyll a(Chl a),dissolved oxygen(DO),pH,and dissolved inorganic nitrogen(DIN),indicating that the concentrations of DFAA in seawater of the trench are affected by many factors,such as photosynthesis,respiration,temperature,pressure,illumination,and circulation.The dominant DFAA are similar in different water layers of sampling stations,including aspartic acid(Asp),glutamic acid(Glu),glycine(Gly),and serine(Ser).The composition of different amino acids,and the relative abundance of acidic,basic,and neutral amino acids might be related to the sources and consumption of various amino acids.Nine pairs of amino acids in the DFAA showed significantly positive relationship by correlation matrix analysis,suggesting that they might share similar biogeochemical processes.The degradation index(DI)of the DFAA in seawater of the Yap Trench could reflect the degradation,source,and freshness of DFAA in the trench to some extents.This is a preliminary study of amino acids from sea surface to hadal zone in the ocean,more works shall be done in different trenches to reveal their biogeochemical characte ristics in extreme marine environme nts.

Characteristics of vertical distributions of methane and dimethylsulphoniopropionate in the southern Yap Trench

Methane(CH_(4) )and dimethylsulphoniopropionate(DMSP)are major carbon and sulfur sources for bacterioplankton in the ocean.We investigated the characteristics of CH_(4) and DMSP in the southern Yap Trench from sea surface to hadal zone in June 2017.We found that concentrations of CH_(4) varied from 1.5 to 4.5 nmol/L with saturation between 94% and 204% in the euphotic layer.Concentrations of dissolved DMSP(DMSPd)ranged from 0.5 to 3.7 nmol/L with higher values in surface water and decreased with depth.Concentrations of particulate DMSP(DMSPp)varied from 0 to 13.6 nmol/L.Concentrations of total DMSP(DMSPt)ranged 2.0-15.2 nmol/L.Their concentrations decreased slightly and reached consistent levels in 200-3000-m depth due probably to heterotrophic bacterial production in marine aphotic and high-pressure environments.An exception occurred around 4000-m depth where their concentrations increased considerably and then decreased in deeper water.This previously unrecognized phenomenon sheds light on the elevated concentrations of DMSP in the abyssal layer that might be affected by the Lower Circumpolar Deep Water(LCPW).Concentrations of CH_(4) in seawater of the Benthic Boundary Layer of the southern Yap Trench were slightly higher than those in the water column at approximate depth,and concentrations of DMSP in seawater of the Benthic Boundary Layer of the southern Yap Trench were not much higher than those in the water column at the approximate depth,indicating that sediment was a weak source of CH_(4) but was not a source of DMSP for seawater in the study area.This study presented clear correlations between CH_(4) and DMSP from sea surface to sea bottom,proving that DMSP might be a potential substrate for CH_(4) not only in oxic surface seawater but also in deep water.

YAG及其掺杂纳米粉体的结构与光学特性(英文)

由于透明多晶钇铝石榴石(YAG)陶瓷在高功率全固态激光器中巨大的应用价值,所以其研究在近几年引起了广泛的关注。YAG陶瓷与其单晶材料相比,可以实现大尺寸激光晶体,高掺杂浓度,并且制备的成本低。我们报道水热方法制备的纯YAG和硅、铷掺杂YAG陶瓷纳米粉体中掺杂与煅烧温度对陶瓷相组分、晶格参数和晶粒尺寸的影响。通过XRD和透射电子显微镜表征了YAG陶瓷及掺杂粉体的结构及其受到掺杂和烧结的作用,利用光吸收和发射谱研究了共掺杂和煅烧温度对YAG陶瓷粉体光学特性的影响。结果表明Si4+和Nd3+的共掺杂提高了Nd3+在YAG纳米体中的可溶度,促进了YAG相的生成,单相纳米Si/Nd∶YAG粉体在 920℃煅烧温度即可获得。它的光学特性与报道的单晶Nd∶YAG一致。

和频振动光谱研究多晶金电极/溶液界面乙腈分子取向的flip-flop行为

应用和频振动光谱研究乙腈/金电极界面吸附,观测到乙腈的甲基振动峰强度随电极电势而变化.当电极电势越过零电荷电势(pzc)时,甲基振动峰符号发生反转,这意味着该基团取向发生反转(flip-flop).由此而推断乙腈分子在金电极界面的吸附构型.即在零电荷电势下,电极界面吸附的乙腈分子构型为甲基靠近电极表面而腈基远离电极表面;高于零电荷电势,则变为腈基靠近电极表面而甲基远离电极表面.

Control factors of DIC in the Y3 seamount waters of the Western Pacific Ocean

An investigation was carried out in the Y3 seamount area of the Western Pacific Ocean in December 2014,and the distribution of dissolved inorganic carbon(DIC)and its relationship with environmental factors in this area were explored.The results show that DIC concentration was higher in the adjacent waters of the Y3 seamount area,and the uplift of DIC isolines at the stations was close to the seamount.Meanwhile,interaction between the North Equatorial Current(NEC)and the Y3 seamount affected the DIC distribution,i.e.,the upwelling in the same direction of the NEC was obvious,resulting in a decreasing trend of average concentration of DIC in the 200 m water column from the top to the two sides in this direction but in the cross direction.The DIC concentration increased with the water depth increase,and its distribution was affected by various environmental factors.In the surface water,high temperature was a decisive factor for the decrease of the DIC concentration,but the photosynthesis of phytoplankton showing only a weak influence.In the North Pacific Tropic Water(NPTW),DIC production rate from organic matter decomposition was higher than that of DIC consumption by phytoplankton photosynthesis,leading to a continual increase of DIC.In the North Pacific Intermediate Water(NPIW),organic matter decomposition played a leading role in the increase of DIC.In the deep water,decomposition of organic matter weakened,and the dissolution of CaCO3 controlled the carbonate system,and DIC had the smallest variation range.

Geochemical characteristics of hadal sediment in the northern Yap Trench

Two sediment cores were retrieved in the hadal zone of the Yap Trench,and their concentrations of six major elements Mg,Al,Ca,Ti,Mn and Fe and nine trace elements Sr,Ba,Pb,V,Cr,Co,Ni,Cu and Zn were determined in inductively coupled plasma atomic emission spectrometry(ICP-AES).According to the vertical distribution profiles of the 15 elements,the correlation of their concentrations,the ratios of Ni/Co,V/Cr,Fe/Al,and Ti/Al,and morphological characteristics of the sediment samples,the implications of the depositional environment and the sediment provenance were analyzed.The results show that the ratio of Ni/Co in all depths of the two sediment cores were below 5,and the ratio of V/Cr were lower than 2,indicating that the depositional environment of the hadal zone in the trench was oxidative and might have inflow of the Antarctic bottom oxygen-rich water.The sediment samples on the eastern side of the trench were siliceous mud mainly composed of diatoms,radiolarian,and sponge needles from surface to deep layer.The vertical profile of the elements,the concentration of TOC and the fossil record indicated that the sediment sample from station Dive113 was well mixed from surface to bottom layer.Based on the correlation of concentrations of the elements,the morphological characteristics of the sediment,and the ratios of Fe/Al and Ti/Al,we inferred that the sediment in the hadal zone of the trench had terrestrial,volcanic,biological,and authigenic sources.Major source of the sediment in the eastern side of the trench were terrestrial;whereas the sediment in the western side of the trench received more volcaniclastic input.

Effect of exposure to ambient PM2.5 pollution on the risk of respiratory tract diseases： a meta-analysis of cohort studies

The International Agency for Research on Cancer and the World Health Organization have designated airborne particulates, including particulates of median aerodynamic diameter 〈 2.5 gm （PM2.5）, as Group 1 carcinogens. It has not been determined, however, whether exposure to ambient PM2.5 is associated with an increase in respiratory related diseases. This meta-analysis assessed the association between exposure to ambient fine particulate matter （PM2.5） and the risk of respiratory tract diseases, using relevant articles extracted from PubMed, Web of Science, and Embase. In results, of the 1,126 articles originally identified, 35 （3.1%） were included in this meta-analysis. PM2.5 was found to be associated with respiratory tract diseases. After subdivision by age group, respiratory tract disease, and continent, PM2.5 was strongly associated with respiratory tract diseases in children, in persons with cough, lower respiratory illness, and wheezing, and in individuals from North America, Europe, and Asia. The risk of respiratory tract diseases was greater for exposure to traffic-related than non-traffic-related air pollution. In children, the pooled relative risk （RR） represented significant increases in wheezing （8.2%）, cough （7.5%）, and lower respiratory illness （15.3%）. The pooled RRs in children were 1.091 （95%CI： 1.049, 1.135） for exposure to 〈 25 gg/m3 PM2.5, and 1.126 （95%CI： 1.067, l. 190） for exposure to 〉 25 gg/m3 PM2.5. In conclusion, exposure to ambient PM2.5 was significantly associated with the development of respiratory tract diseases, especially in children exposed to high concentrations of PM2.5.

Identification and characterization of a delta-12 fatty acid desaturase gene from marine microalgae Isochrysis galbana

The cDNA of the delta-12 fatty acid desaturase gene, IgFAD2, was cloned from the marine microalgae Isochrysis galbana, a species capable of producing docosahexaenoic acid. Sequence analysis indicated that the open reading frame measured a length of 1 158 bp and encoded 386 amino acids with a predicted molecular weight of 42.8 kDa and an isoelectric point of 9.2. Computational analysis of the protein sequence of IgFAD2 showed typical features of membrane-bound desaturase such as three conserved histidine boxes along with four membranespanning regions that were universally present among plant desaturases. Quantitative real-time PCR results showed that the abundance of IgFAD2 transcript was significantly upregulated under different environmental stresses including low temperature(15℃), high salinity(salinity of 62 and 93), and nitrogen starvation(220 μmol/L). Heterologous expression indicated that yeast cells transformed with a plasmid construct containing IgFAD2 could convert endogenous oleic acid(18:1^(?9), OA) into linoleic acid(18:2^(?9, 12), LA). These findings confirm that I. galbana IgFAD2 plays important roles in the biosynthetic pathways of unsaturated fatty acids.

Diel vertical migration of mesozooplankton in the northern Yellow Sea

The Yellow Sea Cold Water Mass(YSCWM),one of the most vital hydrological features of the Yellow Sea,causes a seasonal thermocline from spring to autumn.The diel vertical migration(DVM)of zooplankton is crucial to structural pelagic communities and food webs,and its patterns can be aff ected by thermocline depth and strength.Hence,we investigated zooplankton community succession and seasonal changes in zooplankton DVM at a fixed station in the YSCWM.Annual zooplankton community succession was aff ected by the forming and fading of the YSCWM.A total of 37 mesozooplankton taxa were recorded.The highest and lowest species numbers in autumn and spring were detected.The highest and lowest total densities were observed in autumn(14464.1 inds./m^(3))and winter(3115.4 inds./m^(3)),respectively.The DVM of the dominant species showed obvious seasonal variations.When the YSCWM was weak in spring and autumn,most species(e.g.Paracalanus parvus,Oithona similis,and Acartia bifilosa)stayed above the thermocline and vertically migrated into the upper layer.Calanus sinicus and Aidanosagitta crassa crossed the thermocline and vertically migrated.No species migrated through the stratification in summer,and all of the species were limited above(P.parvus and A.crassa)or below(C.sinicus and Centropages abdominalis)the thermocline.The YSCWM disappeared in winter,and zooplankton species were found throughout the water column.Thus,the existence of thermocline influenced the migration patterns of zooplankton.Cluster analyses showed that the existence of YSCWM resulted in significant differences between zooplankton communities above and below the thermocline.

Characteristics of zooplankton community in North Yellow Sea unveiled an indicator species for the Yellow Sea Warm Current in winter: Euchaeta plana

Zooplankton distributions are largely influenced by both biotic and abiotic factors in the surrounding environment.Some zooplankton species can be used as bio-indicators for particular currents and water masses to help discover the dynamics of water current in the ocean.In this study,we investigated the distribution of zooplankton in North Yellow Sea(NYS)during winter when the Yellow Sea Warm Current(YSWC)influenced that area.Zooplankton communities in the NYS were dominated by temperate and warm-temperate species,such as Calanus sinicus,Paracalanus parvus,Acartia bifilosa,and Sagitta crassa.Two warm-water species,Eucheata plana and Sagitta enflata were also present.Cluster analysis grouped NYS zooplankton into three communities,the Shandong Coastal Community(SCC)in the Shandong neritic area,the Yellow Sea Central Community(YSCC)in the central waters of the NYS,and the Liaoning Coastal Community(LCC)in the Liaoning neritic area.Abundances varied significantly among these communities,with an average of 102.2 ind./m^3 in SCC,179.8 ind./m^3 in YSCC,and 1244.2 ind./m^3 in LCC.Depth and the bottom(3 m from the sea floor)temperature were likely the primary abiotic factors influencing zooplankton distributions.The appearance of E.plana,an indicator species for the YSWC path,indicated a significant northwestward trend for the YSWC in 2007.

Vertical variations of dissolved carbohydrates in the North Yap Trench

The concentrations of dissolved monosaccharides(MCHO),polysaccharides(PCHO),and total carbohydrates(TCHO)in the seawater samples collected from the north of the Yap Trench in the western Pacific Ocean were measured by 2,4,6-tripyridine-s-triazine(TPTZ)spectrophotometry method.The results show that the concentrations of MCHO,PCHO,and TCHO ranged from 4.6 to 22.1μmol C/L,3.5 to 27.3μmol C/L,and 13.8 to 36.3μmol C/L,respectively.In different sampling stations,the concentrations of MCHO,PCHO,and TCHO with water depth showed complex variation patterns.In the study area,the maximum concentrations of MCHO,PCHO,and TCHO occurred in the euphotic layer and the minimum concentrations occurred in mesopelagic seawater layer.Generally,the concentrations of MCHO,PCHO,and TCHO decreased with water depth from the euphotic layer to the hadal zone.The average value of PCHO/TCHO was higher than the average value of MCHO/TCHO,indicating that PCHO was the main component of TCHO in north of the Yap Trench.

Transmission Electron Microscopy as a Powerful Tool for Investigating Lithium-ion Battery Materials

Transmission electron microscopy(TEM) stands out as one of the most powerful tools for characterizing materials at multiple scales and dimensions. This unique technique has nowadays been widely employed in investigating the lithium-ion battery(LIB) materials. The present perspective paper focuses on several LIB related aspects that are recently revealed by using TEM. Finally, we present outlook on the future directions of TEM for LIB research and development.

Global air-sea CO_(2) exchange fl ux since 1980s: results from CMIP6 Earth System Models

The ocean could profoundly modulate the ever-increasing atmospheric CO_(2) by air-sea CO_(2) exchange process,which is also able to cause signifi cant changes of physical and biogeochemical properties in return.In this study,we assessed the long-term average and spatial-temporal variability of global air-sea CO_(2) exchange fl ux(F CO_(2))since 1980s basing on the results of 18 Coupled Model Intercomparison Project Phase 6(CMIP6)Earth System Models(ESMs).Our fi ndings indicate that the CMIP6 ESMs simulated global CO_(2) sink in recent three decades ranges from 1.80 to 2.24 Pg C/a,which is coincidence with the results of cotemporaneous observations.What’s more,the CMIP6 ESMs consistently show that the global oceanic CO_(2) sink has gradually intensifi ed since 1980s as well as the observations.This study confi rms the simulated F CO_(2) could reach agreements with the observations in the aspect of primary climatological characteristics,however,the simulation skills of CIMP6 ESMs in diverse open-sea biomes are unevenness.None of the 18 CMIP6 ESMs could reproduce the observed F CO_(2) increasement in the central-eastern tropical Pacifi c and the midlatitude Southern Ocean.Defi ciencies of some CMIP6 ESMs in reproducing the atmospheric pressure systems of the Southern Hemisphere and the El Niño-Southern Oscillation(ENSO)mode of the tropical Pacifi c are probably the major causes.

Geospatial Assessment of the Impact of Urban Sprawl in Akure, Southwestern Nigeria

This study analyzed trend and examined the factors responsible for urban sprawl in Akure with a view to develop a user-friendly geospatial database for monitoring urban sprawl in the study area. Medium resolution satellite imageries derived from Landsat (TM) and (ETM+) comprising of four dates (1986, 1991, 2002 and 2011) were analyzed. The results revealed that built-up area increased rapidly by 43.31% from 5857.54 hectares in 1986 to 8394.21 hectares in 1991. It further increased by 72.02% from 8762.76 hectares to 15073.7 hectares in 2011. Field study conducted in 2013 involved in-depth interviews and questionnaires to stakeholders and residence respectively. The analysis showed that there was a weak negative relationship (r = -0.189, p < 0.01) between gender and “house ownership”, a weak positive relationship (r = 0.343, p < 0.01) between marital status and “house ownership” and a weak negative relationship (r = -0.159, p < 0.05) between “number of children” and “house ownership” in the sprawl location. Geo-spatial database modeled was tested by subjecting it to spatial analysis to show its capability to answer question pertaining to all the entities of the database. The study concluded that urban sprawl increased and if not reversed, might constitute greater social and environmental problems in the future.

The ecological cost of land reclamation and its enlightenment to coast sustainable development in the northwestern Bohai Bay,China

Land has been widely reclaimed in large area in coastal zones all over the world to relieve the pressure of land shortage,promoting social development and economic growth.Asia has become a focus of land reclamation with the rapid industrialization and urbanization.From the Binhai New Area of Tianjin to the Caofeidian New Area of Tangshan,the undergoing project of land reclamation on the northwest coast of Bohai Bay,China,is the largest in the world.To clarify the environmental issues and benefit sustainable development of the coastal zone,we conducted both retrospective and predictive assessments of the ecological cost caused by land reclamation on the northwest coast of Bohai Bay,China.We calculated the ecological costs of ten aspects of the four ecosystem services,i.e.,supply,regulation,support and culture,with the monetary estimate approach.The results indicate that the ecological cost of the new land reclamation is US$971.9 million from 2000 to 2010 and that the cost will be US$702.1 million from 2010 to 2020.The costs of gas regulation and marine food supply account for the greatest parts of the total value.Suggestions for land reclamation oriented to sustainable development in the study area are put forward,including a rational planning based on the comprehensive evaluation,reducing the amount of land reclamation area,optimizing the structure of the reclaimed land,reclaiming land with the concept of ＂low impact development＂ and implementing ecological compensation mechanisms,etc.

Variation of Physical and Chemical Properties of Soils under Different Cropping Systems in the Watershed of Kpocomey, Southern Benin

Soils degradation is one of the constraints in food security achievement in Benin. This study aimed at assessing the effect of cropping systems and slope on soil physical and chemical properties in the watershed of Kpacomey located in the Aplahoué district. Soil samples were collected from three parallel transects along the slope. Sampling was carried out under different treatments combining cropping systems (Maize-Cassava, pure Palm grove, Palm grove-Maize-Cassava and Teak Plantation) along with slope levels (low slope, medium slope and high slope degree). The impact of cropping systems and slope on soil properties was assessed by determining the physical and chemical parameters. The cropping systems significantly (p < 0.05) influenced soil bulk density, root biomass, soil acidity and soil organic matter. The lowest soil bulk density (1.38 g/cm3) was recorded under the Palm grove-Maize-Cassava cropping system while the highest (1.47 g/cm3) was obtained with pure Palm grove cropping system. Root biomass was more abundant (0.28%) with the pure Palm grove cropping system. However, root biomass was significantly (p < 0.05) influenced by slope. Soil crusting resulted in no significant influence (p > 0.05) on the effect of cropping systems and slope. Moreover, cropping systems resulted in significant effects (p < 0.05). Soil organic matter and soil-assimilated phosphorus content were significantly influenced by the effect of the slope. These findings indicated that cropping systems and slope are significant drivers in soil degradation in the Kpacomey watershed and bringing out cropping systems that best aim at soil conservation.