Watershed Ecology and the Environment最新文献

The invasion of Spartina alterniflora has threatened and damaged coastal wetlands in China, therefore, control and removal of this severe invasive plant are urgently needed. Green chemical control is an effective and low-cost method that can be used for large-scale removal of invasive specie. To study the control effect of imazapyr on S. alterniflora and evaluate its impact on other species and the wetland environment, a control experiment was set up in the Yellow River Delta Reserve in Shandong Province in May 2021. A total of 9 treatments were set up in the experiment: 25 % (W) imazapyr water (main agent), three treatments with dose gradients of 3.0, 6.0, and 9.0 L/acre, and the main agent at a dose of 6.0 L/acre with six treatments of AGE 809 (adjuvant A) and AGE 852 (adjuvant B) with dose gradients of 1.3, 2.6, and 5.2 L/acre, respectively. The results showed that after 60 days of application, the control efficiency of Spartina alterniflora was over 90 %, and the residual amount was small in the plots with the main agent additive < 6.0 L/acre. Among them, the residues on leaves were 0.499 ∼ 2.822 mg/kg, the residues in soil ranged from 0.0012 to 0.0714 mg/kg, and were from not detected in water to 8.8E-4 mg/kg. During the experiment, there were significant differences in soil physicochemical properties among different treatments, and imazapyr significantly affected on the availability of soil C, N, and P at the stage of large chemical residues (P < 0.05). In addition, imazapyr was not toxic to the benthic community and increased from 168.72/m³ to 633.75/m³ in 60 days after spraying. This study provides a theoretical basis, data support, and technical support for applying herbicides to control S. alterniflora in coastal wetlands of China.

The contamination levels and distribution of heavy metals were assessed in riverbed sediments and water column samples from Mura and Kimpulande Rivers, both impacted by copper-cobalt and gold mining activities. Analyses were performed using inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), and atomic fluorescence spectrometry (AFS). Results showed high concentrations of Ni, Cu, Zn, As, Cd, and Hg in water samples. The concentrations of As, Cd, and Hg in water from both rivers exceeded the limits set in Democratic Republic of the Congo (DRC) legislation on requirements for mine water discharges. High concentrations were found also for Cu, Cr, Zn, As, Cd, Pb, and Hg in river sediments and were assessed against sediment quality guidelines for the protection of aquatic life. The Enrichment factor (EF) and the Geoaccumulation index (Igeo) values revealed extremely severe enrichment of Cu, Co, As, and Cd and extreme pollution by Cu and Co in sediment samples demonstrating high contamination of these rivers. The results from calculated ecologic risk factors revealed that aquatic ecosystems in the investigated rivers are at risk. Therefore, a review of current mining practices is needed and the urgent enforcement of good practices is recommended in order to protect the environment and public health.

This study evaluates the concentrations of Cd, Cr, Pb, Ni, As and Cu in water, sediment and tissues (gill, muscle, hepatopancreas) of two crab species (Callinectes sapidus and Cardisoma armatum) collected from the Woji Creek in Niger Delta, Nigeria. As well as the health risk of consuming the crabs was determined. Mean values of metals in surface water revealed concentrations (mg/L) of a trend of Pb (3.252) > Cu (2.328) > Cr (1.590) > Cd (0.146) > Ni (0.109) and in sediments, the trend was in the order Pb (140.930) > Ni (37.481) > Cr (29.984) > Cu (21.001) > Cd (8.910). Hepatopancreas of the crabs accumulated higher concentrations of Cd and Pb; with mean concentrations of Cd and Pb of 0.110 ± 0.008 mg/kg and 1.364 ± 0.060 mg/kg in Callinectes amnicola, and 0.112 ± 0.008 mg/kg and 0.735 ± 0.026 mg/kg in Cardisoma armatum respectively. In the tissues of the three crab species, Pb and Cr were highest; while As was very low in the crab species. The HI was below 1 for males and females (adults and children) which indicates no risk to health from consumption of the edible crab species. Although the risk due to the consumption of these is low, they could be a dietary source of chronic doses of metals to humans.

The southwest coast of India is densely populated and experiences a wide range of natural and anthropogenic pressures. The diversity of macro and meiobenthos was documented in order to assess the ecosystem health of an anthropogenically impacted coastal ecosystem for the first time along the southwest coast of Tamil Nadu. Offshore sediment and water samples (n = 63) were collected from 14 sampling stations using the grid sampling method. Water and sediment samples were analysed for environmental variables such as pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), salinity, sulphate, dissolved oxygen (DO), carbohydrate (CHO), protein, lipid, labile organic matter (LOM), total organic carbon (C_org), total organic matter (TOM) and sediment texture. Benthic macro and meiobenthos were isolated and identified using standard identification keys. A total of 5 phyla of macrobenthos with 29 species and 5 phyla of meiobenthos with 60 species were identified in the study area. Relative abundance analysis showed that the largest numbers of species belonged to Polychaeta for macrobenthos and foraminifera for meiobenthos. Redundancy analysis indicated that sediment carbohydrate content was the highest determining factor for explaining variation in the diversity of benthos. AMBI & M−AMBI results revealed that among the 14 stations, 2 were categorized as “poor” and 9 as “bad”. Multiple anthropogenic activities in the coastal environment leading to increased organic matter input have resulted in a decline in the ecosystem health of this region, which warrants site-specific management to control organic pollution.

Wetlands are under severe threat due to anthropogenic activities and pollutants. Many pollutants such as heavy metals may accumulate to a hazardous level. In the present study, Scylla serrata, the mud crab and associated sediments were collected from three sites of Ashtamudi lake, the Ramsar site, to investigate the bioaccumulation of heavy metals Cadmium, Chromium, Copper, Lead and Zinc. Elemental analysis in the sediment sample showed that Cadmium and Chromium were found to be above USEPA and CCME limits and Copper was found to be above CCME limit on site 1. In site 2, Chromium was found to be above USEPA and CCME limits. In all the three sites, Lead and Zinc are below the permissible limit. Bioaccumulation status of heavy metals in the muscle of Scylla serrata with respect to the sites are in the order of site 1 > site 2 > site. The heavy metals Cadmium, Chromium and Lead were found to be above the permissible limit in site 1 and site 2, whereas Copper and Zinc concentrations in the muscle of crab from Ashtamudi wetland are below levels of concern for human consumption. A number of histological alterations such as splitting of muscle fibres, focal area of necrosis and muscular oedema were noticed in the samples. The result clearly indicates the fact that S. serrata undergoes intensified stress, when exposed to heavy metal contamination. Knowledge of metal concentrations in shell fish and fin fish are important both with respect to nature management and human consumption of fish.

Intense urbanization and increased industrialization in urban and suburban watersheds result in the decrease of vegetation and increase in impermeable surfaces contributing to the decline of soil and water quality. The goal of this study is to investigate the impact of urbanization and industrialization on urban watersheds. The specific objectives are to, 1) determine nutrient and heavy metal concentrations in soil and water samples along Sims Bayou (SB) and Vince Bayou (VB), 2) analyze land cover changes over the last 3 decades in each watershed and 3) evaluate socio-economic characteristics and human health risks within these watersheds. Triplicate soil and water samples were collected from downstream, midstream, and upstream locations during the fall and spring seasons along both bayous. The samples were analyzed to determine elemental concentrations using inductive coupled plasma mass spectrometer (ICP-MS) and total carbon and nitrogen (TCN) analyzer. Landsat 5 TM and Landsat 8 OLI/TIRS images were used to derive thematic land cover maps using ERDAS Imagine v16.5 software. The elemental concentrations were interpolated to spatial maps for distribution analysis using ESRI ArcGIS-10.8 software. The chemical analysis of water samples collected from SB and VB revealed that the N, P, Cu, Ni, Pb, and Zn concentrations were found at elevated levels that can pose threat for aquatic organisms. Among soil samples, the concentrations of Cr, Cu, Ni, Pb and Zn exceeded the levels of soil background concentrations of Texas. Land cover change patterns were similar for both watersheds with high vegetative surfaces decreasing and low vegetative surfaces increasing significantly over the past three decades. Both watersheds experienced an increase in total population with SB watershed increasing 27.9% and VB watershed increasing 9.1% from 1990 to 2020. Health risk assessments revealed risks for Cd, Cr, and Ni in soil via ingestion for children under age 6 in both bayous. This research is critical in improving our understanding on the impact of natural and human activities on Houston watersheds.

Water insecurity is a major concern both in the global and local contexts. The study estimated the sub-catchment water poverty index and the household water security index, on cross-sectional farm household data collected from 652 households randomly selected from eight sub-catchments of the Upper Ewaso Ng’iro North Catchment Area (ENNCA). The impact of water security on household income per adult equivalent and prevalence of waterborne diseases was assessed using ordinary least squares regression and Poisson regression models respectively. Water Poverty Index (WPI) results revealed that Sirimon and Ewaso Narok sub-catchments are faced with acute water stress, while the rest of the sub-catchments are faced with moderate water stress despite being in the sub-catchment area. The results showed that improved water security can offer welfare benefits to households through increments in household income and reduced water-borne disease prevalence. From the findings, therefore, improved water security can offer both economic and health solutions to some of the country's problems including poverty alleviation and reduce the government's budget spending on communicable and non-communicable water-related diseases.

South and Southeast Asia (SSEA) is a socially, economically and ecologically diverse region, with a rapidly growing population and accelerating industrial development, agricultural intensification using manufactured fertilizers, terrestrial landscape change, expansion of water engineering, sewage production and land conversions. Nitrogen and phosphorus are major nutrients that play an essential role in the eutrophication of inland and coastal water bodies. Eutrophic areas, when combined with appropriate coastal ocean physical conditions, can develop into hypoxic zones that result in long-term ecosystem disruption. This study addressed changes in terrestrial nitrogen and phosphorus mobilization associated with land-use transitions, fertilizer use and sewage from 2002 to 2016 in the SSEA region, with a focus on the Mekong and Krishna-Godavari watersheds. Terrestrial mobilization results from the internal production or addition of reactive, soluble and/or plant available forms of nitrogen and phosphorus. To estimate terrestrial mobilization associated with land conversion, published data were mined for estimates of land cover change effects on soil carbon, nitrogen and phosphorus pools. Data on exogenous fertilizer and sewage effluents were also compiled from the literature. From the analysis, it showed that fertilizer input was the largest source of nitrogen and phosphorus in both case study watersheds. Sewage and land conversion were not a significant source of terrestrial phosphorus mobilization in either watershed. All land conversions resulted in declines in soil carbon, ranging from 11% to 38%. Nitrogen increased, on average by 15%, in conversions of agricultural to urban land, but decreased in all other conversions. Phosphorus increased by 89% in wetland to agriculture conversions, but decreased between 2% and 24% for other land conversions. Expansion of agriculture at the expense of forest was the dominant land conversion in the Mekong watershed. Urbanization, at the expense of agriculture and forest, was the dominant land conversion in the Krishna/Godavari watershed. These results suggest that management of nutrient pollution (N and P) in SSEA will need to focus on reducing the use and/or improving the efficiency of fertilizer use along with regular consolidated monitoring in both watersheds.

The Kenyan Lake Victoria basin has been experiencing land degradation and overexploitation as seen in various landscape changes. Quantifying and understanding the nature of these changes is essential for management decision-making. This study sought to apply the Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized Difference Built-up Index (NDBI) - Enhanced Normalized Difference Built-up Index (NDBI-ENDBI) indices to assess the changes in vegetation, water bodies, and build-up area, respectively, in the basin between 1978 and 2018. Landsat imageries for 1978, 1988, 1998, 2008, and 2018 with thematic-oriented bands were acquired, pre-processed, and subjected to spectral-based classification techniques in ArcGIS software to compute and generate NDVI, NDWI, and NDBI-ENDBI maps. According to the results, NDVI indicated an intense decreasing trend in the density of vegetated landscapes while NDVI, NDWI, and NDBI all depicted fluctuations in moisture content (in Lake Victoria and its wetlands). The NDBI-ENDBI showed an intense increasing trend in the built-up area expansion. Based on these changes, the study concluded that urban development has been rapidly progressing within the Lake Victoria basin over the years. Intensive and strategic planning that strikes a balance between economic development and environmental conservation is recommended to realize the sustainability of this important watershed.

Water demand for consumption has been increasing continuously due to the expanding population worldwide. The current accessible water is continually contaminated by global climate change and anthropogenic activities. Economically viable and safe treatment technologies are required for the contemporary world to meet the water demand. The coagulation process is an economically feasible method and gaining much prominence in developing countries for water treatment. During the operation, Sludge and secondary by-products are formed due to the overdosage of the coagulant and improper mixing speeds. Optimizing process parameters is essential to reduce the costs associated with further treatment. Thus, the current study aimed to optimize the process parameters by using Alum, Chitin and Sago coagulants with three pH variations, i.e., 6, 7, and 8, with a mixing speed of 100–30 and 80–20 rpm. The results revealed that Sago performed better than other coagulants and removed the turbidity up to 99.42 %. In addition, Sludge was reduced to 90 % with a dosage of 0.4 g/L, a minor dosage compared to the literature with an optimal pH of 7. Further, the coagulants were characterized to identify the functionalized groups by FTIR, the nature of the coagulant by XRD and Surface morphology by SEM. From the current study, it can be concluded that a coagulant dose ranging from 0.1 to 0.4 g/L with a mixing speed of 100 rpm for 2 min and 30 rpm for 30 min might be the best solution for obtaining greater coagulation efficiency.