Effects Of Agricultural Activities Research Articles

Hydrogeochemical evolution processes, groundwater quality, and non-carcinogenic risk assessment of nitrate-enriched groundwater to human health in different seasons in the Hawler (Erbil) and Bnaslawa Urbans, Iraq

The main objectives of this research are to assess groundwater, a primary source of drinking water in the urban areas of Hawler (Erbil) and Bnaslawa in northern Iraq, and the non-carcinogenic human health risks of nitrate contamination associated with drinking water quality. For this purpose, twenty-seven groundwater samples were collected from wells to assess the hydrogeochemical characteristics and groundwater quality for both natural and anthropogenic purposes during the wet (May 2020) and dry (September 2020) seasons. During the wet and dry seasons, NO3− in groundwater ranged from 14.00 to 61.00 mg/L and 12.00 to 60.00 mg/L, with an average value of 35.70 and 29.00 mg/L, respectively. Approximately 25.92% of the samples exceeded the permissible limit of the WHO (2011) drinking water standard. The ratios of NO3−/Na+ vs. Cl−/Na+ and SO42−/Na+ vs. NO3−/Na+ indicate the effect of agricultural activities and wastewater leaking from cesspools or septic tanks on the quality of groundwater during the wet and dry seasons. The entropy weighted water quality index method ranked 62.5% and 75% of the urban groundwater as not recommended for drinking, and the remaining samples are moderately suitable in both wet and dry seasons. The non-carcinogenic human health risk assessment displayed that during the wet and dry seasons, 29.6% and 25.9% of adults, 48% and 30% of children, and 48.1% and 29.6% of infants were exposed to increased concentrations of nitrate in groundwater. Due to high nitrate in drinking water, non-carcinogenic human health risk levels vary as infant > child > adults. The main findings obtained from this study can assist policymakers in better understanding the hydrogeochemical properties of groundwater in terms of drinking water safety, thereby facilitating the management of water resources to take the necessary measures.

Research on Effects of Agricultural Activities and Transgenic Crops in Biodiversity in Bangladesh

Research on Effects of Agricultural Activities and Transgenic Crops in Biodiversity in Bangladesh

Effect of agricultural activity on diet in an assemblage of lizards from Monte, Argentina

AbstractEven though the encroachment of agriculture is the main cause for biodiversity loss, studies have focused in tropical and temperate environment, mainly in birds, mammals and beneficial and/or pests' invertebrates. However, little is known about the impact in poor environment or lizards communities. Our aim was to compare food use and availability in trophic resources in two assemblages of seven lizard (Liolaemus darwinii, L. riojanus, L. cuyanus, L. wiegmannii, Aurivela longicauda, Homonota underwoodi and Teius teyou) at a cultivated and a non‐cultivated site in a desert area of San Juan, Argentina. We analysed lizard food preferences, taxonomic and functional diversity, dissimilarity and the relationship between morphological variables and prey item frequency. We found that the diet of six species, at both sites, was focused on Hymenoptera (< 80%), whereas secondary and accessory items varied widely between species and sites, with 40% dissimilarity. Prey at the cultivated site were more abundant, rich and diverse than in the non‐cultivated site, with 20% dissimilarity in species composition. Functional diversity showed redundancy when comparing morphological and dietary traits. Results suggest that the greater variation in the diet of species at the cultivated site is likely due to a higher diversity of prey available. We determined that diet could be a limiting factor for L. cuyanus, because there are no native plants at the cultivated site, whereas the remaining species opted for increasing their intake of Hymenoptera.

Background Characteristics and Influence Analysis of Greenhouse Gases at Jinsha Atmospheric Background Station in China

Central China has been acting as a major convergence zone for sources and sinks in China, such that the climate change studies of Central China have taken on critical significance. The Jinsha atmospheric background station refers to the sole background monitoring site in Central China. It is noteworthy that the greenhouse gas attributes of the Jinsha atmospheric background station represent the greenhouse gas conditions of Central China. The seasonal and daily variations in CO2, CH4, and CO in the scope of time between October 2019 to April 2021 at the station were examined in this study. The effect of meteorological conditions on greenhouse gas concentrations at the site was evaluated. Furthermore, the primary transmission origins affecting the station were identified using the backward trajectory through potential source contribution function analysis. As indicated by the results, the background concentrations at the Jinsha station in 2020 for CO2, CH4, and CO reached 424.1 ± 0.1 ppm, 2046.2 ± 0.6 ppb, and 324.1 ± 1.1 ppb, respectively. CO2 varied on a daily basis with higher nighttime levels, which was affected by the boundary layer elevation, photosynthesis, and human activities. In autumn, CH4 levels peaked under the effect of agricultural activities in Central China. However, CO2 and CO concentrations reached the maximum in winter, majorly affected by the transmissions from the Beijing–Tianjin–Hebei region and Hubei. Under China’s comprehensive carbon neutrality, more attention should be paid to the emissions from winter heating and industrial activities in the Beijing–Tianjin–Hebei region, and effects exerted by transport in the monitoring process should be differentiated in depth.

Evaluation of nitrate concentrations in groundwater of Llío and San Pablo, Guano – EC

This paper analyzes the groundwater of the Chambo aquifer in the Llío and San Pablo sector, with emphasis on the temporary alternation of nitrate concentration, identifying the anthropogenic activities that may influence this area. This from the cartographic definition of the areas of begging influence the crossing of geological, hydraulic and anthropic activities. The temporality of the geochemical data is 5 years (2016-2020), these results show that water quality meets the requirements of the Ecuadorian national standard, and that the main composition of water is bicarbonated type of calcium-magnesium. Even if the groundwater in this sector meets the standard, variation in nitrate concentration is evident. This type of concentration is presented by the effect of agricultural activities on the surface of the soil, where nitrates occur naturally due to the nitrogen cycle, and that are dragged into the water table by infiltration when the rainy season occurs. In addition, it was found that the type of rock found underground cannot naturally generate nitrates.

Occurrence, bioaccumulation and ecological risks of antibiotics in the water-plant-sediment systems in different functional areas of the largest shallow lake in North China: Impacts of river input and historical agricultural activities.

Antibiotics are widely used and ubiquitous in the environment, which in turn poses potential threat to human health. However, the effects of agricultural activities and river input on the fate and ecological risks of antibiotics in shallow lake are still poorly understood. Surface water, overlying water and pore water, sediments and aquatic plant samples in the historical planting subarea (PA), historical aquaculture subarea (AU), inflow subarea (IW), discharge subarea (DC), and conservation subarea (CK) of Baiyangdian Lake were collected and analyzed. Our results revealed that the total antibiotic concentrations ranged from 85.33 ng/L to 1631.47 ng/L in waters and from 66.90 ng/g to 177.03 ng/g in sediments. Generally, the total antibiotic concentrations introduced by planting activity in surface water, overlying water and sediments were higher and the levels of total antibiotics in pore water were more affected by river input. In addition, three quinolones (QNs) and two tetracyclines (TCs) were dominant antibiotics in almost five subareas. The pseudo-partitioning coefficient kd(pw) and bioaccumulation factor (BAF) of antibiotics varied according to the effects of river input and historical agricultural activities. The ecological risk (RQ) of antibiotics from agricultural activities was higher than that from river input. The norfloxacin (NOR) in pore water showed high RQ, which contributed to a large proportion (>50 %) of the combined ecological risks (∑RQs) except for surface water. Therefore, NOR should be used as the primary ecological risk control index for antibiotic contamination management in the BYD. ∑RQs showed high risk in water in the five subareas. This study can act as a reference for governments to formulate effective management strategies for protecting the ecological health of lakes.

Interregional comparative analysis of farmers’ perceptions and expectations of climate change

This study looked into the relationship and effects of agricultural activities in different regions of Turkey on climate change. This study aims to determine farmer awareness of climate change and its effects, as well as farmer adaptation capabilities in different regions of Turkey against climate change, and to develop extension and policy tools based on the findings. Data were collected through face-to-face surveys with farmers in the provinces where the research was conducted. In this context, a proportional sampling survey of 418 farmers was conducted. The collected information was subjected to factor analysis and the independent t-test. According to the findings, farmers associate climate change with precipitation, and the effect of precipitation and the risks it poses in increasing or decreasing crop yields are of particular concern. Farmers in the Southeastern Anatolia Region are more concerned about heat and drought than farmers in the Mediterranean Region. Furthermore, producers believe that human-caused factors and economic development have a greater impact on climate change than agricultural activities. Farmers in research areas are concerned that climate change will increase migration from rural areas and the decline of forests and animal species. As a result, raising individual awareness and utilising new technology in rural areas is critical. Farmers’ awareness of new and environmentally friendly agricultural techniques must be raised to increase their use. Highlights - Farmers associate climate change with drought. - According to the farmers, the leading factors causing climate change are human-induced factors that disrupt the ecological balance. - The most important concern regarding the effects of climate change is that production costs will increase. - Farmers are reluctant to implement adaptation or mitigation methods that can be developed against climate change.

Investigating the Assemblages of Two Groups of Collembola (Strong Furca and Weak Furca) under Different Agricultural Management Systems, Northeastern China

Agriculture itself has been considered one of the leading reasons for biodiversity loss because of the huge quantity of land dedicated to just this activity, and agricultural intensification has impacted soil organisms at several taxonomic levels. Soil biota is a vital component of the agricultural system, providing essential ecosystem services while also having synergistic impacts on crop yield. Preservation of their diversity becomes a major element of an agricultural sustainability strategy. Many studies focused on agricultural activities’ effects on soil organisms, but few of them have focused on their effects on the co-occurrence patterns of their communities. Collembola communities are frequently employed as a substitute for soil organisms; thus, as a surface-dwelling arthropods representative, we investigated assemblages of soil Collembola in reaction to the arrangement of 6 treatments varying in crop rotation (MC: monoculture (corn) vs. CS: corn–soybean rotation) and tillage types (MP: mould ploughing; RT: ridge tillage; and NT: no-tillage). We hypothesized that Collembola communities with strong furca would respond well to the agricultural practices than those with weak furca, and there would be strong co-occurrence between species of Collembola communities belonging to the treatments with less intensity of soil disturbance and more variation in crop rotation. Our study found no clear evidence of a beneficial effect of crop rotation on Collembola communities. Although Collembola with strong furca shows higher abundances in plots with mold plowing, weak furca abundances were not showing any difference (differences in abilities to move fast from harsh habitats could be the reason for different responses of these two groups). Network analysis revealed that Collembola assemblages seem to occur more responsive to tillage intensity than crop rotation. Network graphs of treatments with ridge tillage are significantly more clustered than all others. For the first time, we can show that assemblages of springtails in agriculture were distinguished by a pattern of co-occurrence alongside agricultural practices (crop rotation, soil tillage), showing variations in the disturbance of soil and soil nutrients. Our results, contrary to our expectations, demonstrated that the effects of agricultural activities on Collembola abundance and diversity could be weak after long-term application of the same treatment, but still, they will clearly affect the bonds between Collembola species by affecting their co-occurrence pattern in Collembola communities.

Spatial pattern of soil erosion using RUSLE model and GIS software at the Saf Saf watershed, Algeria

Soil erosion is one of the problems threatening the Algerian environment. In agriculture, soil erosion leads to the thinning of the topsoil under the effect of the natural erosive forces of water, or under the effect of agricultural activities. The present study aims to estimate average soil loss rate and to identify vulnerable zones. Through the integration of RUSLE model at the Saf Saf watershed, various parameters are utilized such as the rainfall erosivity factor (R), soil erodibility factor (K), slope length - slope factor (LS), crop management factor (C) and practice management factor (P). All these parameters are prepared and processed through a geographic information system (GIS) and remote sensing using various database sources. The results reveal that the river basin has an average annual soil loss of 3.9 t ha−1 yr−1, and annual soil loss of 4.53 million tonnes for the period 1975-2017. Meanwhile, eighty five percent of the study area is experiencing acceptable rate of soil erosion loss, which is ranging between 0 to 5 t ha−1 yr−1. The present study of risk assessment can contribute to understand the spatial pattern of soil erosion in order to use appropriate conservation practices for sustainable soil management.

Effects of agricultural activities on hydrochemistry in the Shiyang River Basin, China.

Agricultural water accounts for more than 80% of the available water in arid areas. Agricultural activities have a great impact on surface water and groundwater. If the impact of agricultural activities on hydrochemistry is not prevented, the risk of water quality change in arid areas may be greatly intensified. Based on the hydrochemical data of the whole Shiyang River Basin from April 2014 to October 2019, this paper analyzes the impact of agricultural activities on hydrochemistry in the basin. The results show that (i) in the middle and lower reaches of farmland with high intensity of agricultural activities, the ion concentration of groundwater in summer and autumn is significantly higher than that in winter and spring due to the influence of irrigation; (ii) the runoff ion concentration in the backflow of the river reaches recharged by irrigation water is significantly higher than that of other reaches; (iii) due to strong evaporation, different types of reservoirs will lead to an overall increase in ion concentration, which is more obvious in plain reservoirs and river tail lakes. In addition, the reservoirs have a certain removal effect on nitrates.

Effects of agricultural activities on long-term accumulations of 226Ra and 210Po in topsoil

Effects of agricultural activities on long-term accumulations of 226Ra and 210Po in topsoil

Effect of agricultural activities on surface water quality from páramo ecosystems.

Páramos are high mountain ecosystems strategic for water provision in South America. Currently, páramos are under threat due to agricultural intensification that impairs surface water sources. This research analyzed the effect of agriculture (spring onion—Allium fistulosum, potato—Solanum tuberosum, and livestock farming) on water quality in páramo ecosystems. A Hydrographic Unit upstream of the Jordan river catchment (Colombia) was selected and monitored in two different rainfall regimes, following the paired catchments and upstream-downstream approaches to compare water quality from natural and anthropic areas. Twenty-two parameters related to agricultural activities were analyzed (nutrients, salts, organic matter, sediments, and pathogens). The studied agricultural activities increased loads of surface water in quality in nitrates (0.02 to 2.56 mg N-NO3/L), potassium (0.13 to 1.24 mg K/L), and Escherichia coli (63 to 2718 FCU/100 mL), generating risks on the human health and promoting eutrophication. Total nitrogen and organic matter in the rainy season were higher than dry. BOD5, COD, turbidity, and E. coli were above international standards for direct human consumption. However, water could be used for irrigation, livestock watering, and aquatic life ambient freshwater. The results show that a small land-use change of almost 15% from natural páramo vegetation to agricultural uses in these ecosystems impairs water quality, limiting its uses, and the need to harmonize small-scale livelihoods in the páramo with the sustainability of ecosystem service provision.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-21709-6.

A distributed robust optimization model based on water-food-energy nexus for irrigated agricultural sustainable development

Sustainable agricultural development covers all aspects of agricultural production involving the water-food-energy nexus (WFEN) and considers the effects of agricultural activities on society, economy and ecology. Multi-objective optimization models play an important role in making tradeoff among multiple interests of stakeholders.Aimed at canal-based irrigated agricultural areas, water allocation highly depends on canal distribution, and the spatial location of irrigation regions determines their water-intake order, which usually induces serious water allocation inequality. The social, economic and ecological problems resulting from water inequality would deteriorate without intervention and seriously impact sustainable development. Thus, optimization models must consider water use equity, water-intake order as well as water equilibrium simultaneously. However, this will greatly increase computational efforts and solution difficulty. The problem becomes worse when uncertain factors are involved.In order to overcome these difficulties, a distributed multi-objective uncertain optimization model was established to help develop comprehensive strategies for agricultural sustainability. A novel robust solution method was proposed to offer an efficient way to handle stochastic and fuzzy uncertainties from the perspective of feasibility and optimality robustness. Finally, a case study was conducted to demonstrate the practical application of the developed model. The results offer managers insights on agricultural sustainable development.

Effects of agricultural activities on energy-carbon-water nexus of the Qinghai-Tibet Plateau

Energy, carbon, water and their interactions determine agricultural production efficiency and sustainability. On the Qinghai-Tibet Plateau (QTP), agricultural activities threaten the ecological security of the region, and agriculture itself is susceptible to climate change. In this study, we applied an energy-carbon-water nexus framework to assess the carbon emissions, water utilization, and energy flow, and their links with agricultural production on the QTP, using emergy analysis, footprint analysis (carbon footprint and water footprint) and a coupling model. The results showed that agricultural activities on the QTP released 2.17 × 1010 kgCO2-eq and absorbed 6.00 × 1010 kgCO2-eq, using 3.24 × 1022 sej of emergy and 8.19 × 109 m3 of water in 2018. Meanwhile, the energy-carbon-water nexus of agricultural production on the QTP was imbalanced, and the environmental footprint revealed large spatial heterogeneity at county scale. The coupling interaction among the energy-carbon-water nexus in agricultural production was investigated based on the coupling coordination model. Five categories of coupling interaction were identified by the degree of coordination. The largest emitter was agricultural input, especially electricity and nitrogen fertilizer, accounting for 24% and 7% of the total on average, respectively. With regard to emergy flows, renewable organic resources, accounted for 47%, making them the predominant in emergy inputs. The green water footprint (water from natural rainfall) at 51% was higher than the blue water footprint (water from irrigation) at 49%. More measurements to reduce carbon emission and improve the efficiency of energy usage and water usage are needed, such as optimizing planting patterns and structures, promoting cleaner energy, improving the efficiency of agrochemical use and proposing reasonable spatial planning for regional ecological development. Our findings provide a systematic reference for energy-carbon-water nexus analysis and sustainable agricultural development policy for decision-makers on the QTP.

Coastal-Hinterland Exchange and Garden Hunting Practices Prior to the European Invasion of Hispaniola

ABSTRACT This study analyses zooarchaeological material recovered from the late precolumbian site of El Flaco (AD 990–1450), northern Dominican Republic. The faunal assemblage from this inland settlement demonstrates terrestrially focused modes of faunal exploitation but with some resources obtained from coastal ecosystems, such as mangrove forests, sandy-bottom, and reefs, which are located approximately 20 km to the northwest. This study establishes last occurrence dates for extinct taxa; examines the spatial distribution of fauna; explores modes of food procurement; and the effects of agricultural activities on local fauna by investigating animal remains from three excavation units. A diachronic study of animal remains from one artificial mound demonstrates changing patterns in resource exploitation, such as an increasing consumption of land crab over a roughly 100-year period. This study follows previous research that examined the isotope ecology of endemic species from El Flaco that indicates some hutias were possibly scavenging or being fed cultivated plants. Palaeoenvironmental data suggest that Indigenous landscape transformations led to the creation of mosaic environments, which may have attracted and supported certain species, implying that the inhabitants of El Flaco likely did not have to venture far to trap or hunt many of the animals upon which they relied.

Agricultural land use changes stream dissolved organic matter via altering soil inputs to streams

Agricultural land use leads to significant changes in both the quality (e.g., sources and compositions) and quantity of dissolved organic matter (DOM) exported from terrestrial to aquatic ecosystems. However, the effect of agricultural activities often interacts with those of hydroclimatic drivers, making it difficult to delineate agriculture-induced changes and identify associated mechanisms. Using partial least square path modeling (PLS-PM), we examined the relative importance of agricultural land use, stream order, precipitation, and temperature in mediating allochthonous versus autochthonous sources and pathways that influenced stream DOM quality and quantity. We analyzed stream water DOM from 15 small streams draining watersheds across a gradient of agricultural land use in Southeast USA for about one year. For DOM quantity, agricultural land use increased the export of DOC and various DOM pools (terrestrial humic, microbial humic, and protein-like DOM) from land to streams, and for DOM quality, agricultural streams showed greater proportions of microbial humic compounds than forested streams. The PLS-PM model for DOM quantity accounted for 75.5% of total variance and identified that agricultural land use increased stream water DOM quantity primarily through increasing allochthonous inputs, which can be attributed to shallower flow paths in agricultural watersheds that enabled the export of organic materials from the upper, organic-rich soil horizon. PLS-PM models for DOM quality only explained ~13% of the total variance, highlighting the complex dynamics between environmental drivers and stream water DOM. Relative to commonly used multivariate statistic modeling (e.g., redundancy analysis (RDA)), PLS-PM models offer the advantages of identifying the primary pathway by which agricultural lands alter freshwater DOM and quantifying the relative importance of interactive effects of agriculture and hydroclimatic drivers. Therefore, structural equation modeling is a powerful tool that should be more widely adopted to distinguish among multiple drivers and mechanisms regulating freshwater biogeochemistry.

Mapping Croplands in the Granary of the Tibetan Plateau Using All Available Landsat Imagery, A Phenology-Based Approach, and Google Earth Engine

The Tibetan Plateau (TP), known as “The Roof of World”, has expansive alpine grasslands and is a hotspot for climate change studies. However, cropland expansion and increasing anthropogenic activities have been poorly documented, let alone the effects of agricultural activities on food security and environmental change in the TP. The existing cropland mapping products do not depict the spatiotemporal characteristics of the TP due to low accuracies and inconsistent cropland distribution, which is affected by complicated topography and impedes our understanding of cropland expansion and its associated environmental impacts. One of the biggest challenges of cropland mapping in the TP is the diverse crop phenology across a wide range of elevations. To decrease the classification errors due to elevational differences in crop phenology, we developed two pixel- and phenology-based algorithms to map croplands using Landsat imagery and the Google Earth Engine platform along the Brahmaputra River and its two tributaries (BRTT) in the Tibet Autonomous Region, also known as the granary of TP, in 2015–2019. Our first phenology-based cropland mapping algorithm (PCM1) used different thresholds of land surface water index (LSWI) by considering varied crop phenology along different elevations. The second algorithm (PCM2) further offsets the phenological discrepancy along elevational gradients by considering the length and peak of the growing season. We found that PCM2 had a higher accuracy with fewer images compared with PCM1. The number of images for PCM2 was 279 less than PCM1, and the Matthews correlation coefficient for PCM2 was 0.036 higher than PCM1. We also found that the cropland area in BRTT was estimated to be 1979 ± 52 km2 in the late 2010s. Croplands were mainly distributed in the BRTT basins with elevations of 3800–4000 m asl. Our phenology-based methods were effective for mapping croplands in mountainous areas. The spatially explicit information on cropland area and distribution in the TP aid future research into the effects of cropland expansion on food security and environmental change in the TP.

Changes in Water Quality of the River das Antas as It Passes through Rural and Urban Areas

The catchment area of River das Antas (Irati, Paraná, Brazil) is of high importance both for human consumption and irrigation. Within Irati, this river passes through a rural area and through the city of Irati, crossing both poor and rich neighbourhoods. We selected three study areas downstream (a rural area, poor community, and rich neighbourhood) in which we measured turbidity, the concentration of sediments and pH during rainy days. Our results showed downstream trends of increasing turbidity and concentrations of sediments with decreasing pH. The values of turbidity and of concentration of sediments were significantly different in the rural area, while the pH values were significantly different between the three study areas. These findings highlight the effect of agricultural activities in the generation of sediments and turbidity. The—presumably expected—effects of organic urban waste from the poor neighbourhood were also detected in the pH values. We conclude that efforts should be made to ensure that land planning and training/education programmes on sustainable farming practices are undertaken by the authorities to reduce water pollution and its effects on water bodies during rainfall events, since paving streets is not a feasible option in the short term due to the high costs associated with this measure.

典型喀斯特流域旱雨季交替下溶解硅的输送特征

河流溶解硅（DSi）作为营养物质对维持陆地、河流及海洋生态系统稳定性起到至关重要的作用。选取贵州典型喀斯特流域为研究对象，通过对DSi湿沉降过程，基流过程及降雨径流过程的动态变化进行全年监测分析，探讨DSi在旱雨季交替下的输送特征及河流DSi浓度变化引起的环境效应。结果表明：①湿沉降过程降雨量越大，DSi浓度越小，河流DSi浓度变化有明显的旱、雨季特征，雨季DSi浓度较高，旱季较低，地表水径流量及DSi浓度对降雨径流过程的响应比地下水明显。②DSi沉降通量及输出通量呈明显的旱、雨季差异，雨季DSi湿沉降通量占全年的69.5%，地表水雨季DSi输出负荷占全年的98.1%，地下水占51.4%。③流域硅酸盐岩风化过程不强烈，主要受到碳酸盐岩及蒸发岩控制。流域DSi浓度受人为水库影响明显，经过水库后河流中DSi浓度旱季下降29.0%、雨季下降70.9%。研究为全面认识硅在陆地生态系统中的生物地球化学循环提供科学依据。;Dissolved silicon (DSi) in natural waters plays important roles in sustaining continent, riverine and ocean ecosystems. It is a necessary nutrient for the growth and reproduction of aquatic plants and phytoplankton, especially diatoms. The composition of dissolved silicon in river systems is complex and depends on physical, chemical, and biological processes that occur in drainage basins and rivers. In this study, a typical karst watershed located in Guizhou Province, Southwest China was selected as the study area to reveal the characteristics of DSi transport and discuss seriously environmental effects on the variation of DSi concentration. The objects of this research were to monitor the dynamic characteristics of dissolved silicon in wet deposition, rainfall-runoff processes and baseflow process in the dry and wet seasons during the whole year and to discuss about serious environmental effects on the variation of DSi concentration. Results showed that (1) The greater the rainfall, the smaller the DSi concentration during the wet deposition. DSi concentration in the wet season was higher than that in the dry season. DSi concentration and discharge in surface water were more easily responded by rainfall-runoff process than in groundwater. (2) The deposition flux and export flux of DSi showed evident differences in the wet and dry seasons. DSi deposition flux in the wet season accounted for 69.5%, and export load of surface water and groundwater accounted for 98.1% and 51.4% of the whole year, respectively. (3) The study area had a slow weathering rate of silicate minerals which was mainly controlled by carbonates and evaporite rates. DSi concentration was significantly affected by man-made reservoir as the results showed that the DSi concentration dropped by 29% and 70% in the dry and wet seasons, respectively. The study is conducive to a more comprehensive understanding of the silicon biogeochemical cycle in terrestrial ecosystems. In future studies, long-term studies on the effects of agricultural activities and land use patterns on the supply of nutrients in the watershed are needed to predict the change of phytoplankton community with the dynamic change of DSi concentration from a long-term perspective. In addition to DSi monitoring, BSi monitoring should be added to further study the silicon cycling process and related environmental effects in terrestrial ecosystems.

ASSESSMENT OF AGRO-ENVIRONMENTAL CHALLENGES AND POLICY RECOMMENDATIONS FOR SUSTAINABLE AGRO-ENVIRONMENTAL MANAGEMENT IN WEST AFRICA

The agricultural sector, indispensable in meeting the increasing demand for food, is the main user of natural resources. Agricultural production breeds significant environmental impacts and problems both within and outside farms or agricultural holdings. This situation increases the sensitivity of the agriculture to the risks that can cause serious economic losses. Thus, unless measures are taken to solve the environmental problems arising from agricultural production, the sustainability of agricultural production and food supply even less the achievement of food and agriculture-related sustainable development goals can be seriously threatened. However, these risks and losses can be mitigated through policy reform, institutional and technological innovations. In West Africa, more than 40% of water and land resources are used for agricultural production. This makes agro-environment relations more important. This study has been carried out to reveal the major agro-environmental challenge in West Africa and to examine the current approaches and policies applied to solve these problems. In the study, data obtained from FAO agro-environmental indicators database were used as the main material. In this study, using a research methodology subdivided into two stages, the effects of agricultural activities on the environment were examined, analyzed and interpreted by comparing the agro-environmental profiles of West African countries with other OECD countries based on agro-environmental indicators. Agro-environmental policies applied to resolve agro-environmental problems in West African countries were reviewed and recommendations for sustainable agro-environmental management and also a more efficient and environmentally friendly agricultural sector were formulated for sustainable agriculture and food supply.