Sustainability of Water Quality and Ecology最新文献

Denitrification, the microbially mediated reduction of NO₃⁻ to N₂, NO, or N₂O gas, provides an important ecosystem service by reducing N loads to downstream waters. To incorporate denitrification services into management planning, it is important to quantify the benefit; however, it is difficult to quantify denitrification rates and even harder to extrapolate them spatially and temporally to generate landscape-scale estimates of denitrification. We developed a coupled hydrologic-denitrification model that predicts daily denitrification rates across an agricultural watershed and calibrated it using in situ denitrification measurements and two types of hydrologic observations (streamflow and upland soil moisture). The model fits well with the observed denitrification (R² = 0.77, RMSE = 272 kg N ha⁻¹ yr⁻¹, NRMSE = 0.77), stream discharge (NSE = 0.66) and soil moisture (NSE = 0.77), and quantifies the denitrification ecosystem service provided by the watershed as a whole, as well as by the various land classes. Over the seven year model run, mean annual denitrification rates were 21 kg N ha⁻¹ yr⁻¹ watershed-wide, 47 kg N ha⁻¹ yr⁻¹ in the wetland, 52 kg N ha⁻¹ yr⁻¹ in cropped areas, and 4 kg N ha⁻¹ yr⁻¹ in pastures and forests. Quantification of ecosystem services is an essential prerequisite to accounting for those benefits in management decisions. This study is one step towards addressing the lack of field validated ecosystem service quantification studies. In the future, the model will allow us to further examine the spatial and temporal patterns of denitrification and to explore the implications of changes in management practices or climate.

The potential of managed aquifer recharge (MAR) in semi-arid areas of Nigeria was evaluated using the Kano River irrigation Project (KRIP) as a case study. Groundwater recharge was evaluated daily for 3 years (2009–2011) using the water level fluctuation (wlf) method. Temporal and spatial analyses of recharge were carried out using Microsoft Excel® spread sheet and ArcGIS® 9.0 software. Results show that recharge range from 17 to 32 mm daily on the farmland. Further analysis showed that an average of 8 mm of water is added to storage daily from both rainfall and irrigation. The observed waterlogging problems has implication for salt build up in the area and could be ameliorated by conjunctive use of both surface water and groundwater from the farmland. This will lead to huge water savings that could be released from the Tiga dam to recharge the Chad formation aquifers downstream of the Hadejia River in a systematic MAR implementation via infiltration basin. However, additional modelling studies and aquifer characterization are required to implement this.

Sustaining water availability for smallholder farmers in the near future presents a great challenge to agricultural production in Nigeria. This study assessed the smallholder farmers’ welfare using assets possession and factors affecting their production outputs in Nigeria. A multistage sampling technique was applied in three agro-ecological zones with primary data collected and analysed using both descriptive and inferential statistics. Results show that the crop water application system practiced across the study area included rainfed system, gravity flow system, motor pump system and bucket system. A large percentage of the motor pump farmers had improved livelihood going by the type of assets they possess. Some of the irrigators were observed to use water unsustainably (not maintaining the existing system for the future generations through misuse and management of the available water resources) especially those using gravity flow system and motor pump systems. This should be discontinued in the face of the climate change affecting the country. Likewise, the use of some agro inputs such as fertilizers need to be controlled since increasing the level of these inputs was found not to translate to increased output for the farmers. Finally, the land tenure system in Nigeria does not promote smallholder farmer’s welfare as no farmer had formal title to their lands. This makes it difficult to have sufficient access to credit facilities. The policy is inimical to agricultural development in Nigeria and should be relaxed.

Prashar Lake, an unexplored, high-altitude, shallow, and cold water body located in Himachal Pradesh (India) was studied through monthly surveys in two consecutive years (March 2008 to February 2010). The seasonal variations in chlorophyll a, abundance, and species composition of plankton in relation to hydrography were studied. A total of 67 species belonging to eight groups of phytoplankton were identified. Among 67 phytoplankton species, 19 species exhibited perennial habit. Both plankton and chlorophyll a showed bimodal pattern of fluctuation with peaks in May and September. Annual mean concentrations of chlorophyll a (mg L⁻¹) were recorded as 4.87 in 2008–09, and 4.03 in 2009–10. Palmer pollution index indicated absence of all the 20 pollution tolerant algal species. Pearson correlation revealed a significant relationship between physicochemical parameters and different algal groups. Important physicochemical parameters responsible for distribution of phytoplankton have been studied taking into account the portability of water for irrigation and drinking purposes as per permissible limits of WHO, ICMR, and ISI standards. The values of water quality index were 14.42 during 2008–09 and 16.51 during 2009–10. Based on water quality standards given by Central Pollution Control Board, the water quality at Prashar Lake was between “A and B”. Carlson’s trophic status classified Prashar Lake as oligotrophic with TSI values 17.085 (2008–09) and 14.57 (2009–10). The phytoplankton assemblage, as well as water quality data, suggest that water at Prashar Lake is unpolluted and could be used for various human purposes after disinfection.

In order to enhance and protect the resilience of the Great Lakes, predicting future outcomes of climatic changes, particularly in already degraded geographical areas is instrumental to success. These changes include warming air and water temperatures; shifts in the timing, severity and frequency of precipitation events and storms; varying lake levels; and reductions in lake ice cover. Changes to regional climate pose increased risks to the water resources and the beneficial uses or services they provide. This review paper examines how a changing climate will likely affect beneficial uses as defined in the Great Lakes Water Quality Agreement. Extracting the drivers of the degradation of the beneficial uses is a strategy to reduce the risk of beneficial use impairment. The variables reviewed include the changes driven by air and water temperatures, precipitation events and storms as well as evaporation and water level declines. We assessed the impacts of climate change on beneficial uses systematically and provide adaptations strategies that target the driver of degradation to strengthen the resilience of beneficial uses in the Great Lakes Areas of Concern. Adaptation to water quality issues, water level declines and aquatic invasive species are highlighted. This review provides up to date climate information and is designed to aid policymakers, coastal managers, and planning professionals as they begin to address the impacts of climate change.

There are plans to use Irish energy crop plantations as repositories of organic by-products (OBs). It is first necessary to determine the risk of surface-water (SW) pollution from amendment of OBs to energy crops under typical Irish conditions. Therefore, the impact of application of two OBs on the quality of overland flow (OLF) emanating from plantations of Miscanthus × giganteus was assessed. Municipal biosolids (BS) and distillery effluent (DE) were spread annually (for four years) on six 0.1174 ha plots at “100%”, “50%” and “0%” treatment rates. The 100% rate was the maximum P-load of 15 t ha⁻¹ allowed by regulation. Surface flows were sampled over 25 months and tested for pH, electrical conductivity, NO₃⁻, P, K, Cu, Cd, Cr, Pb, Ni, and Zn. Results were compared to drinking-water (DW) and SW quality limits; total exports were used to assess risk to SW. The concentrations of nitrate and heavy metals were within DW limits. Concentrations of PO₄³⁻ were above limits in all cases; K in OLF from M-DE_x plots was above DW limits (in some cases). Despite high concentrations, all exports were relatively small, as OLF events were rare and involved small volumes. There was correlation between OB treatment and increases in OLF concentration in some cases, implying higher applications could result in larger exports. Results imply very low SW quality risks exist in areas that are not prone to OLF (at treatment rates and plot scales used). It is recommended further work is conducted to assess risks at catchment scales, particularly for P-loss.

Microbial and toxic metals contamination of freshwater resources is still a major problem in many parts of the world. In this study, water and sediment samples (n = 9) were subjected to the microbiological and some physicochemical analysis to assess the water quality of the N’Djili River (Kinshasa, Democratic Republic of Congo). Microbiological analysis was performed for faecal indicator bacteria (FIB) including Escherichia coli (E. coli) and Enterococcus (ENT). The FIB characterization was performed for general E. coli, Enterococcus faecalis (E. faecalis) and human-specific bacteroides by PCR, using specific primers. The physicochemical parameters including pH and electrical conductivity were measured in water samples, and grain size distribution, organic matter and total mercury (Hg) were measured in sediments samples. The results revealed high concentration of FIB, with the maximum values of 1.6 × 10³ and 2.7 × 10³ CFU 100 mL⁻¹ for E. coli and ENT, respectively. The FIB in sediment samples present higher concentration than in water, with maximum values of 9.4 × 10⁵ and 1.2 × 10⁵ for E. coli and ENT, respectively. The PCR assays for human-specific bacteroides HF183/HF134 indicated that more than 90% of bacteria were from human origin. The Hg concentration in sediment samples reaches the values of 0.5 mg kg⁻¹. Thus, our results indicate that the uncontrolled landfills and mixing of untreated urban and industrial effluents lead to the deterioration of the water quality of the rivers traversing the economically important cities. This study represents useful tools to evaluate water and sediment quality in river systems which can be applied to similar aquatic environments.

Aquifer Storage and Recovery (ASR) technology has been proposed to meet the competing ecological and water-supply needs of south Florida and the Everglades Protection Area (EPA). The water recovered from ASR, however, may have altered water quality. Of particular concern is the enrichment of ASR recovery water in sulfate, which can stimulate microbial sulfate reduction and methylmercury (MeHg) production within the EPA. MeHg is already a serious issue with regard to wildlife and human health, and there is concern that ASR might exacerbate the problem. In order to address these concerns, the Lake Okeechobee Environmental Model (LOEM) and the Everglades Landscape Model (ELM) were adapted with sulfur modules to predict concentrations and distributions of sulfate within Lake Okeechobee and the EPA resulting from the release of ASR water. In addition, equations were developed relating the biogeochemistry of sulfate and MeHg production to produce a MeHg production risk assessment from the modeled ASR sulfate loading. Baseline runs (no ASR discharge water), and three different ASR release scenarios with varying sulfate loading were evaluated. Results show that ASR release will temporarily elevate sulfate concentrations in Lake Okeechobee from the present level of about 30 mg/L to as high as 50 mg/L in a worst case scenario, but that this will have little impact on MeHg production in the lake. The model indicates that ASR release will have minimal impacts on sulfate loading to the EPA, primarily because of the already large sulfate loading from other sources within the Everglades Agricultural Area (EAA). Maps of sulfate distributions show that certain locations in the EPA, especially those near canal or Stormwater Treatment Area (STA) discharges, may experience significantly higher sulfate loading from ASR. Overall impacts with regard to increased MeHg production risk are predicted to be low based on this model, although sites with increased ASR sulfate loading (e.g. canal and STA discharge sites) may experience some change in MeHg risk.

We have determined the water quality index (WQI) of post-monsoon water samples with an aim to assess changes in Ganges river at various locations in Allahabad stretch including that from the confluence with river Yamuna. Physicochemical parameters such as temperature, pH, electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS), major cations e.g. Na⁺, K⁺, Mg²⁺, Ca²⁺, major anions e.g. F⁻, Cl⁻, Br⁻, SO₄²⁻, NO₃⁻, PO₄²⁻ and alkalinity were analyzed by standard procedures. The values obtained were compared with the guideline values for drinking water by Bureau of Indian Standard (BIS) and World Health Organization (WHO). From the measured quantities, certain parameters were selected to derive WQI for the variations in water quality of each designated sampling site. Results showed considerable deterioration in quality of water at some of the sites. WQI of Ganges river water at Allahabad ranged from 86.20 to 157.69 which falls in the range of poor quality of water. Pearson’s correlation matrix was drawn to find possible interrelations among measured water quality parameters. It is shown that WQI may be a useful tool for assessing water quality and predicting trend of variation in water quality at different locations in the Ganges river.