Total Phosphate Concentrations Research Articles

Correlation assessment and monitoring of the potential pollutants in the surface sediments of Pyeongchang River, Korea

The study provides a baseline for the assessment of the organic and inorganic pollution specially, heavy metal contamination in the surface sediments of Pyeongchang River, South Korea. The assessment of the study areas was done with respect to metal pollution load, ecological risk and geoaccumulated risk. Based upon the used indices, a priority index ( P index ) was used to rank the utmost contaminated sites. Though the concentrations of mercury in all sediments were below the guideline, the significant enriched contamination was observed by all applied indices. As expected, the values of pollution load index ( PLI), ecological risk index ( RI) and geoaccumulation risk index ( I geo ) demonstrated lower heavy metal contamination in upstream areas compared to the downstream. Admittedly, sediments were unpolluted to slightly-polluted according to PLI while high to extremely high ecological risks were observed in several sediment samples. Furthermore, all the samples were uncontaminated as per I geo . After simplification of I geo , the P index showed the utmost contaminated sediments with a value of 2.537. Notably, protective measures should be taken to the highly contaminated areas which are prioritized by P index . Admittedly, the maximum concentrations of total organic carbon, total nitrogen, inorganic nitrogen, total phosphorous, inorganic phosphorous, calcium, magnesium, sodium and potassium were significantly observed as 7.8×10 4, 3,185, 36, 1,032, 3.7, 1,5163, 2,881, 669 and 4,076mg/kg accordingly.

Evaluation of the toxicity of cyanogens in a commonly consumed Nigeria legume pigeon pea (<i>Cajanus cajan</i>) seed and its biochemical effects in rabbits

The effect of a commonly consumed Nigeria legume pigeon pea (Cajanus cajan) seeds with high cyanogen concentration on some important biochemical parameters and haemoglobin concentration in new Zealand rabbits was investigated over a period of 72 hours. Quantitative analysis of the legume seed revealed that it has in mg/100g dry weight 39.3+1.30 cyanogenic glycosides, 11.57+1.20 phytate, 28.58+1.02 oxalate and 3.80+0.01 Tiu/100g dry weight typsin inhibitor respectively. Analysis of the serum and urine samples from test and control rabbits indicated that there was no significant difference (p£ 0.05) in the concentrations of total protein, bilirubin, inorganic phosphate and creatinine. There was a slight decrease in the activities of alkaline phosphatase. However, the activities of serum transaminases: alanine amino transferase (ALT), aspartate amino transferase (AST) as well as cyanide concentration increased significantly (P£±0.05). Cyanide concentration in the serum increased from 5 to 27 mg/l and that in the urine from 3.5 to 26mg/l in the rabbits fed with commercial feed when compared to those fed with Cajanus cajan formulated feed. The study revealed that consumption of Cajanus cajan seed made pulses occasionally would not result to cyanide toxicity.

Characterization and Comparison of Stream Nutrients, Land Use, and Loading Patterns in Maryland Coastal Bay Watersheds

Land use and its relation to nutrient concentrations and loading via streams is an important issue in coastal lagoons and embayments worldwide including the Maryland coastal bays system, USA. As in many coastal areas around the globe, declining water quality in the bays is the result of nutrient inputs from the surrounding watershed. In this study, the sources of the nutrient inputs were examined. Monthly concentrations of total nitrogen (TN), ammonium (NH4+), nitrate (NO3-), phosphate (PO4-3), and total phosphorus (TP) were measured in six streams in the St. Martin River basin from July 2006 to January 2008. Current land use information for the basins of each stream was also compiled. Several significant correlations between nutrients and land use type were found. The most significant correlation was with the land area of feeding operations, which demonstrated a significant positive relationship with mean baseflow TN concentrations. A similar relationship was also found with anthropogenic land area (cropland + urban + feeding operations), and wetland area was also positively associated with hydric soils. Using local water yields from a US Geological Survey station, annual stream watershed export was calculated using the concentration data, which indicated that the watershed with the most crop agriculture had the highest N export coefficient (20.4 kg N ha-1 year-1), while the highest P export (0.47 kg P ha-1 year-1) was in a watershed containing a nonoperational chicken hatchery and a subsequently modified channel. This suggests that agricultural development, especially animal feeding operations, and landscape characteristics are important factors to understand nutrient loading in St. Martin River and Maryland coastal bays. The methods used and the results determined in this study have implications for determining nutrient loading in lagoons and embayments, in relation to land use in coastal regions globally.

In situ estimation of water quality parameters in freshwater aquaculture ponds using hyperspectral imaging system

Knowledge of water quality parameters is integral to sustainability of freshwater aquaculture operations that raise ornamental fish. Our objective in this study is to evaluate the ability of a mobile, ground-based hyperspectral (HS) imaging sensor to determine chlorophyll-a (Chl-a) concentrations in working aquaculture ponds, which represent manipulated, shallow, nutrient-rich systems, and to determine the effect of using submerged reflectance targets on the accuracy of Chl-a estimation. We collected Chl-a measurements from aquaculture ponds ranging from 0.8 to 494 μ g / L . Chl-a measurements showed a strong correlation with two-band and three-band spectral indices computed from the HS image reflectance. Coefficient of determination ( R 2 ) values of 0.975 and 0.982 were obtained for the two- and three-band models, respectively, using spectra captured from the submerged target at 10 cm depth. Using spectra captured from water (no submerged targets), R 2 values were slightly lower at 0.833 and 0.862 for two- and three-band models. Data from the submerged target at 30 cm depth had the lowest correlation with measured chlorophyll-a concentrations, potentially due to variations in water column properties and shadows cast by the platform. Modeling total Phosphorous (P) and Nitrogen (N) concentrations of the collected samples with the spectral indices sensitive to Chl-a concentrations showed a moderate level of correlation. Removing a model outlier (observation with maximum N and P concentrations) led to a significant increase in the models’ coefficient of determination ( e.g. from 0.478 to 0.823 for the P model using three-band index values), which highlighted the possibility of using HS imagery to estimate N and P concentrations and the need for more research to model the interrelationships between Chl-a and nutrient concentrations in aquaculture water systems.

Phosphorus Removal and Recovery from Hog Lagoon Supernatant Using a Gravity-Settled Batch Reactor and Increased pH

In Canada, the majority of swine waste is stored in open lagoons and land applied according to crop nitrogen requirements. This practice over-applies phosphorus (P) two- to five-fold, leading to potential runoff or leaching loss of P to the environment. Removing P from liquid hog waste is an important step in correcting the N:P ratio of manure applied to cropland. Reclaiming this P as struvite (MgNH4PO4) would ease environmental concerns of eutrophication, provide a saleable fertilizer, and help address the limited global supply of phosphate. Most struvite reactors are capital and operationally intensive, making the process too expensive to be implemented by the average farmer. In addition, high calcium levels found in some supernatants compete with magnesium (Mg), and struvite formation is impaired. The objective of our study is to test the effective P removal and settled solids quality from using a low energy, low capital, pilot-scale gravity-settled batch reactor. Lagoon supernatant with total phosphate (TP) concentration from 58 to 216 mg L-1 and pH of 6.7 was adjusted to pH 8.5 and allowed to settle with no addition of magnesium chloride. Results show that TP was reduced by 76.5%, total suspended solids were reduced by half, soluble P was reduced by approximately 90% (94.5 to 10.3 mg L-1), and particulate mineral forms of P were reduced by 69% (83 to 26 mg L-1), perhaps by flocculation. The dried solids had a TP concentration of 5.6%, total nitrogen of 6.3%, and potassium of 3.8%. Struvite content in the solids was estimated at 30%, and calcium phosphates comprised the remainder of the mineral P compounds. Half of the dried solids were estimated to be organic. The presence of calcium did not impede good P removal, perhaps due to long settling times (24 h). These results indicate that nutrient-rich supernatants with high suspended solids are good targets for P recovery, but product purity is a challenge.

Fate of Nitrogen and Phosphorous in Source-Separated Urine

In this paper, we focus on the fate of nitrogen (N) and phosphorous (P) in source-separated urine. Fresh mixed urine of pH 6.7 was diluted with different factors and stored openly and closed respectively. With pH increasing concentration of total phosphate (TP), total nitrogen (TN), ammonia nitrogen(NH3-N) and dissolved phosphate(PO43-) were measured to understand the fate of N and P in urine. Because of volatilization and precipitation, concentration of NH4+-N and PO43- in the urine stored closed was higher than them of stored openly with the equal dilution. Under same storing conditions, the higher dilution factor, the higher concentration of NH4+-N. When stored openly the pH of the samples increasing due to urea-hydrolysis resulted in precipitation which consumed N and P, and could be promoted by dilution with tap water containing hardness ions. Because of a few of hardness ions in the urine and tap water, the amount of precipitations containing calcium, magnesium, N and P in the urine sludge of every sample were not high enough to be detected by XRD. Although more flushing water would caused more precipitation, which is also helpful for nutrient recycling, using of large deal of tap water is not economic and environmentally friendly.

Performance evaluation of eight years experience of constructed wetland systems in Catalonia as alternative treatment for small communities

In Catalonia (Spain), a variety of different systems have been built to naturally treat liquid residues from small communities. Some of these wastewater treatment plants (WWTPs) include constructed wetlands with horizontal subsurface flow (HSSF) as secondary treatment. The present study described and characterized the performance of 11 WWTPs with secondary HSSF constructed wetland systems after an initial operating period of 8 years. The effluent concentrations of Biochemical Oxygen Demand (BOD5), Total Suspended Solids (TSS), Total Nitrogen (TN) and Total Phosphorous (TP) were statistically analyzed, and removal efficiencies for all WWTPs including all stages in treatment were calculated. The accumulated probability functions of those parameters were evaluated to determine the influence of two different types of polishing units on the overall performance: (a) only lagoon systems and (b) lagoon systems with HSSF. The statistical analysis indicates good performance for BOD5 and TSS. In the first case, mean concentrations below 25mg/L were found in 9 of the 11 plants analyzed and removal efficiencies between 78 and 96% were observed. In the second case, mean concentrations below 35mg/L were found in 8 of the 11 plants, and removal efficiencies were between 65 and 88%. For the nutrients, the removal efficiency for TN and TP were in the range of 48–66% and 39–58%, respectively. Additionally, the analysis of the influence of the polishing units did not show a significant improvement (α>0.05) for any parameter in the wetland systems without a subsequent polishing unit. However, in the wetland systems with a polishing unit of HSSF, a significant improvement (α<0.05) was found for the effluent's BOD5, TN and TP concentrations but with no significant contribution in TSS management.

Combined Pond–Wetland Systems for Treatment of Urban Surface Runoff and Lake Water

Abstract Purifying initial surface runoff is one of the most important measures to improve water quality and recreation value of water bodies in an urbanized area such as Moshui Lake. Two types of combined pond–wetland systems were constructed to store and treat the initial urban surface runoff together with the combined sewer overflow in rainy season and the diluted municipal wastewater or the Moshui Lake water in dry season. After one year, the deposition pond–landscape pond–vertical flow constructed wetland (VFCW)–horizontal flow subsurface constructed wetland (HFCW) system was more effective than the deposition pond–HFCW system in removing chemical oxygen demand (COD), total phosphorous (TP), total nitrogen (TN), and suspended solids (SS). After being treated by the deposition pond–landscape pond–VFCW–HFCW system, the initial influent containing COD 161.0 ± 28.4 mg L−1, TP 2.65 ± 0.27 mg L−1, TN 23.21 ± 2.04 mg L−1, and SS 531.2 ± 56.2 mg L−1 was purified to have the COD, TP, TN, and SS concentrations...

Growth, reproductive and photosynthetic responses to copper in the yellow-horned poppy, Glaucium flavum Crantz.

Glaucium flavum Crantz. is found in an anthropized coastal grassland at the joint estuary of the Tinto and Odiel rivers (SW Spain), growing under the influence of high levels of copper contamination derived from nearby petrochemical industries, with no obvious adverse affects on the performance of the plant. In addition, this species exhibits a series of ecological characteristics which may render it appropriate for use in the phytoremediation of contaminated areas. Nonetheless, the response of G. flavum to elevated copper concentrations has not been studied. A greenhouse experiment was conducted to investigate the effects of a range of Cu concentrations (0 to 47mmoll−1) on the growth, reproduction and photosynthetic performance of G. flavum, by measuring relative growth rate, fruit and seed production, chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. We also determined total copper, nitrogen, phosphorous, sulphur, calcium and magnesium concentrations. G. flavum survived with concentrations of up to 730mgCukg−1 DW in the leaves, when treated with 30mmolCul−1 (2000mgl−1). Quantum efficiency of PSII, net photosynthesis rate, as well as leaf Ca and Mg concentrations were all negatively affected by Cu concentrations greater than 9mmoll−1 in the nutrient solution. Our results indicate that the reduction in photosynthetic performance may be attributed to the adverse effect of excess Cu on the photosynthetic apparatus of the plant, both directly, via a decrease in pigment concentrations, and indirectly, via interference of Cu with Ca ions of PSII. Growth and seed production were only slightly affected by leaf tissue concentrations as high as 230mgCukg−1 dry mass, which suggests that this species could play an important role in phytoremediation of Cu-contaminated soils.

Acid‐base imbalances during a 120 km endurance race compared by traditional and simplified strong ion difference methods

Acid-base disturbances are traditionally assessed using the Henderson-Hasselbach equation. The simplified strong ion approach describes more accurately the complex acid-base and electrolyte abnormalities present in endurance horses. To describe acid-base and electrolytes changes in fit horses competing in a FEI*** 120 km endurance race and to compare the traditional vs. strong ion approaches. Thirty horses were initially enrolled in the study. Venous blood samples were obtained before the race (n = 25), at the second (n = 29; 65.4 km) and third vet-gates (n = 23, 97.4 km) and upon race completion (n = 17). Blood gas analysis was performed to determine pH, PCO(2), PO(2), Na(+), K(+) and iCa(++), and calculate HCO(3)(-), base excess and tCO(2). Packed cell volume and total protein, globulin, albumin, lactate, phosphate, glucose and creatinine concentrations, as well as muscle enzymes activities, were also determined. Calculated variables included strong ion difference (SIDm), strong ion gap (SIG) and nonvolatile buffer concentration (A(tot)). A longitudinal linear model using the general estimating equation methodology was used for statistical analysis. Mild but significant increases in PCO(2), SIDm, lactate, plasma protein, globulins and A(tot), as well as a decrease in potassium concentrations were observed from the second vet-gate to race finish when compared to prerace values (P < 0.05). Using the strong ion approach, 67% samples showed acid-base disturbances vs. 70% when using the traditional method, but their interpretations only matched in 24% of measurements. A complex acid-base imbalance characterised by a mild strong ion alkalosis (hypochloraemia attenuated by hyperlactataemia), nonvolatile buffer acidosis and compensatory mild respiratory acidosis were present in most horses, although pH did not significantly change during a 120 km endurance race. The strong ion approach to interpretation of acid-base balance should be favoured over the traditional approach in endurance horses, given the frequent and complex alterations in PCO(2), SIDm and A(tot) during a race.

Natural Variations in Flow Are Critical in Determining Concentrations of Point Source Contaminants in Rivers: An Estrogen Example

Daily steroid estrogen concentrations as 17β-estradiol equivalents (E2 equiv.) were modeled from 1992 to 2008 for single locations on the well populated Thames and Soar rivers in England. The historic daily mean flow values which were the basis of this exercise came from a selected gauging site on each river. The natural variation in flow from winter to summer typically produced a 20- to 30-fold difference in predicted estrogen concentration over the course of a year. Based on all the predicted values from minimum to maximum over the 1992 to 2008 period there was a 98-fold difference in estrogen concentrations on the basis of flow alone for the Thames (0.1-12.7 ng/L E2 equiv.) and 67-fold for the Soar (0.2-13.3 ng/L E2 equiv.). This compares to a predicted 0.5-fold difference that could arise from differences in sewage treatment and 0.1-fold difference due to differences in in-stream biodegradation. The seasonal variation in flow generated a repeating "roller coaster" in predicted estrogen concentrations. Regularly measured phosphate data for the river Avon over the period 1993 to 1996, where point sources also dominate, was compared against flow and predicted estrogen concentrations. The pattern of predicted estrogen and measured total phosphate concentration were very closely related. This dramatic variation in contaminant concentration over the year due to flow poses questions over what we mean by environmental relevance and the representation of the real environment in aquatic ecotoxicity tests.

The influence of shrimp farms organic waste management on chemical water quality

We evaluated the physical–chemical properties and nutrient concentrations in two shrimp ponds under conventional management, intensive (I-P) and semi-intensive (SI-P), and one under organic management (O-P), three days after loading and before stoking. The mean’s total alkalinity concentrations were 2.26 ± 0.04 mM, 2.28 ± 0.01 mM and 2.59 ± 0.01 mM, respectively for I-P, SI-P and O-P. Bicarbonate and carbonate accounted for 62% and 37% in I-P, 64% and 36% in SI-P and 83–17% in O-P, respectively. Aragonite and calcite were oversaturated around Ω = 5. Mean total phosphate (TP) concentrations were 441.37 ± 92.06 μg/L, 449 ± 48 μg/L and 473.64 ± 84.17 μg/L, under I-P SI-P and O-P management respectively. Following this sequence, NO 3 − concentration was 2.98 ± 0.7 μg/L, 1.16 ± 0.16 μg/L and 0.32 ± 0.12 μg/L, under I-P, SI-P and O-P management respectively. Thus, the data suggest that different management of farm organic waste leads to different chemical water quality.

Aquatic ecosystem responses to fire and flood size in the Okavango Delta: observations from the seasonal floodplains

The frequency of fires in the Okavango Delta seasonal floodplains peaked at an intermediate frequency of flooding. Floodplains are commonly burnt every 3–5 years. This study showed fundamental changes in ecosystem properties due to burning. A burnt seasonal floodplain in the aquatic phase had oxygen levels well above saturation, 100–200%, while the levels in the un-burnt control site were below saturation and, at night, could decline to 10–40% saturation. The total phosphorous and total nitrogen concentrations were similar on both floodplains but considerably enriched relative to inflowing water, due to nutrient release from the flooded soil-sediment and animal droppings. Zooplankton biomass was very high in both systems although the abundance of fish fry was ten times higher on the un-burnt floodplain. In a low flood year the un-burnt floodplain water had high nutrient levels, primary production, methane emission, and subsequent uptake of methane in biota, as well as a high zooplankton biomass. The very high flood the following year showed the opposite with much lower production at all levels owing primarily to greater dilution of nutrients. The abundance of fish, however, was much higher during the high flood year. Macrophytes and litter provide direct shelter for fish fry but also promote low oxygen levels when decaying. Large flooded areas result in high fish production by removing obstacles related to congestion. This interplay between hydroperiod and fire may be crucial for the maintenance of high biological productivity both in the aquatic and terrestrial phases in a very nutrient poor wetland landscape. Understanding these interactions is crucial for optimal management.

Regulation of bone formation using rapamycin-induced BMP2 expression system: influence of implanted cell number

A rapamycin (RPM)-inducible fibroblast cell line expressing BMP2, BLK-RapBMP2, was previously developed using a stringent dimerizer-regulated transcription system to achieve more kinetic control of bone morphogenetic protein (BMP) expression for exogenous bone regeneration. This study examined the precise control of BMP2 synthesis and the induction of bone formation using various amounts of cells and rapamycin. The response to the rapamycin analogue (AP21967) caused the BLK-RapBMP2 cells to induce BMP2 expression in a cell amount-dependent manner corresponding to changes in the bone formation components in vitro and in vivo. The administration of rapamycin (1 mg/kg, i.p. for 6 weeks) induced variable ectopic bone formation to diverse number (2−10 × 106) of BLK-RapBMP2 cells in collagen hydrogel implants of a skin pouch in C57BL/6 mice. Microradiographic, biochemical (total calcium and phosphate concentration) and histological analyses suggest that control of the implanted cell number affects the level of rapamycin-induced bone formation. These results suggest that this technical control of BMP2 expression by adjusting the number of cells is a potential factor that might allow more precise control of bone regeneration.

하천변 양배추 밭에서의 영양물질의 거동

This study was conducted to investigate the dynamics of nutrients such as total nitrogen (TN), nitrate nitrogen (<TEX>$NO_3$</TEX>-N) total phosphorous (TP), and phosphate phosphorous (<TEX>$PO_4$</TEX>-P) in outflow from a cabbage farmland in a mixed land-use watershed. The TN concentrations in groundwater showed twice peaks in late July 2006 and late March 2007 (3.8, 4.7 mg/L, respectively), when it rained shortly after fertilizer application, indicating that nitrogen leaching is greatly influenced by fertilization and rainfall. The mean concentrations of TN and <TEX>$NO_3$</TEX>-N in surface water were not significantly higher than those in groundwater, while the mean concentrations of TP and <TEX>$PO_4$</TEX>-P in surface water were significantly (p < 0.05) were higher than those in groundwater. The TN concentrations in groundwater were generally higher than those in surface water during fertilization and early growing season due to the effect of fertilization, but vice versa in the other periods. In contrast, the TP concentrations in groundwater were always lower than those in surface water due to the sorption of particulate phosphorous by soil. The ratio of TN load in baseflow to that in total TN load (39 %) was much greater than the TP ratio (7 %), suggesting that baseflow contribute to nitrogen export. Therefore, proper fertilization management should be taken to reduce nitrogen load through baseflow.

Dynamics of the water bloom-forming Microcystis and its relationship with physicochemical factors in Lake Xuanwu (China)

China's freshwater subtropical shallow lakes are increasingly eutrophic and susceptible to production of heavy growths or water blooms of cyanobacteria. One example was the heavy water bloom that occurred for the first time in Lake Xuanwu, in 2005, an urban lake located in Nanjing city. The aim of the present study was to determine dynamics of water bloom dominating Microcystis in this lake. Meanwhile, the relationship between environmental factors and Microcystis populations was also analyzed. Molecular detection, using quantitative polymerase chain reaction, was used in this lake to study the dynamics of the cyanobacterial community, its Microcystis populations, and the microcystin-producing Microcystis genotypes from August 2005 to November 2006. It was shown that Microcystis wesenbergii and Microcystis aeruginosa were the main components of the cyanobacterial blooms in Lake Xuanwu, and they coexisted with species of the filamentous cyanobacterial genera Anabaena, Planktothrix, and Anabaenopsis. Microcystis cells were detected during the entire survey period and in all sample sites. The cell abundance of Microcystis ranged from 3.6 × 10(2) cellsml(-1) to a peak of 3.8 × 10(6) cellsml(-1). The ratio of mcyB-containing Microcystis subpopulations to the total Microcystis varied, ranging from 0.1% to 12.8%. The abundance of Microcystis containing the mcyB microcystin gene was shown to be significantly correlated with concentrations of total phosphorus and phosphate. Water temperature was the primary factor affecting Microcystis abundance in the lake, and phosphorus loading was shown to be a main factor in governing the growth of both microcystin-producing genotype and total Microcystis population. Higher Microcystis cell counts at the bottom of the water column before and after appearance of water blooms in Lake Xuanwu suggested that Microcystis numbers in the water column, especially at the bottom of the water column, play an important role in forming the next water bloom.

The Co-effect of Cordyceps sinensis and Strontium on Osteoporosis in Ovariectomized Osteopenic Rats

The co-effect of Cordyceps sinensi (CS; caterpillar fungus) and strontium on ovariectomized osteopenic rats was studied in this paper. After the rats were treated orally with CS, strontium (SR), and CS rich in strontium (CSS), respectively, the urine calcium, plasma calcium, plasma phosphorus, bone mineral content, mechanical testing, and the mass of uterus, thymus, and body were examined. Both CSS and SR have a positive effect on mechanical strength and mineral content of ovariectomized osteopenic rats. However, femoral neck strength in the CSS-treated group was higher than those in the SR-treated groups. CSS and SR significantly decreased urinary calcium excretion and plasma total calcium and inorganic phosphate concentrations. On the contrary, CS and CSS significantly increased weights of atrophic uteri and weights of body and also decreased the thymus mass in animals, whereas SR did not exhibit any such effects. Our experiments have demonstrated that CSS possess a preferable effect against the decrease of bone strength and bone mineral mass caused by osteoporosis. It was caused by the co-effect of CS and strontium. The mechanism of it includes decreases bone resorption, increases bone formation, increases in body weight, and enhances 17β-estradiol-producing as well as enhancing the immune functions in animals. The data provide an important proof of concept that CSS might be a new potential therapy for the management of postmenopausal osteoporosis in humans.

Phytoplankton dynamics and cyanobacterial dominance in Murchison Bay of Lake Victoria (Uganda) in relation to environmental conditions

Murchison Bay is a shallow embayment in the north-western part of Lake Victoria, strongly influenced by urban pollution from the Ugandan capital Kampala. Two stations, representing the semi-enclosed innermost part of the bay and the wider outer part of the bay, were sampled in the period from April 2003 to March 2004, in order to assess the phytoplankton community and the nutrient status in the bay. Murchison Bay was highly eutrophic with average concentrations ( n= 25) of total phosphorous >90 μg L −1 and total nitrogen >1100 μg L −1 in the inner part of the bay. The phytoplankton community was dominated by a variety of cyanobacterial species and diatoms. Cyanobacteria were dominant in the whole bay, whereas diatoms were more abundant in the outer part of the bay. Moreover, the proportion of N-fixing species like Anabaena sp. was higher in the outer part of the bay, whereas species like Microcystis sp. were more abundant in the inner part of the bay. The phytoplankton community, especially in the outer part of the bay, may be influenced by light limitation. Low NO 3 –N concentrations in the bay may also indicate a possible N-limitation, thus favouring growth of N-fixing cyanobacteria. The open bay is, however, a complex system, and additional environmental factors and loss processes most likely affect the phytoplankton community.

The distribution of phosphorus in sediment and water downstream from a sewage treatment works

In order to ensure the good ecological status of a range of waterbodies, as set out in the EU Water Framework Directive, a clearer understanding of nutrient sources and delivery mechanisms is required. Therefore, this study aimed to investigate the quantity and distribution of phosphates in Cam Brook, downstream from Paulton sewage treatment works (STW). Nine sites along a 2.6 km stretch of the river were surveyed; including one upstream of the STW, in October 2008 and the following February to determine whether there is seasonal variation in phosphorus concentrations. Water samples taken from each site were analysed for orthophosphate although sediment samples were analysed for orthophosphate and total phosphate. In February, water samples were further analysed for total phosphorus. Other variables such as dissolved oxygen (DO), water velocity, substrate, width, depth and land use were also surveyed to determine whether they influence the distribution of phosphorus. The water orthophosphate concentrations in Cam Brook significantly increased downstream from the STW in both October and February, rising from mean concentrations of 0.07-0.23 mg l −1 . This suggests that the STW was the major contributor to water orthophosphate concentrations. There was also strong negative correlation between water orthophosphate and DO concentrations in October (r-value −0.414) which could be due to the high biological oxygen demand of decomposers in the Autumn. There were large concentrations of total phosphate in the sediment which can be attributed to the small particle size of the substrate (clay) which increases its adsorption capacity. There were no seasonal variations in the water orthophosphate or sediment total phosphate concentrations although sediment orthophosphate concentrations were significantly higher in February (p-value < 0.001). However, orthophosphate still only accounted for a small proportion, at 3.47%, of the total phosphate concentrations in the sediment. The orthophosphate entering Cam Brook from the STW appears to be subject to a complex set of storage and transformation mechanisms which results in its storage as the non-bioavailable fraction of the total phosphate. Further research needs to be undertaken to determine the phosphorus cycling mechanisms that cause seasonal variation in sediment orthophosphate concentrations.

Evaluación de mejores prácticas de manejo para reducir las pérdidas de nutrientes contaminantes en escorrentía desde suelos enmendados con carnada de pollos parrilleros. II. Cobertura de hierbas.

Se evaluó el impacto de la extensión de la cobertura del pasto Bermuda [Cynodon dactylon (L.)] en la pérdida de sedimentos y nutrientes en escorrentía en suelos enmendados con residuos de carnada de pollos parrilleros (con alum). La escorrentía generada de los suelos completamente descubiertos reflejó valores significativamente mayores en los volúmenes de escorrentía y en las concentraciones de sólidos suspendidos, fósforo total (TP) y nitrógeno total Kjeldahl (TKN), que en suelos con ≥80% de cobertura de pasto. Además, el suelo descubierto exhibió un tiempo de inicio de escorrentía menor (lapso de tiempo entre inicio de la lluvia y el comienzo de la escorrentía) que los suelos con pasto. Las concentraciones promedio de P total y TKN en la escorrentía de bandejas experimentales con a80% de cobertura de hierba exhibieron una reducción de 93% y 89.5%, respectivamente, comparado con aquellas en la escorrentía de las bandejas con suelo al descubierto. Por otra parte, la concentración de sólidos suspendidos mostró una reducción de 99% sobre la del suelo al descubierto. Las pérdidas en fósforo disuelto estuvieron bien por debajo del límite de 1 mg/L sugerido como el nivel para el control de contaminación de fósforo de tierras agrícolas, incluyendo suelos enmendados con residuos de carnada de pollos parrilleros. En el caso de estos residuos, el resultado es un reflejo de la efectividad del alum en la reducción de la pérdida de fósforo disuelto en la escorrentía. En general, tanto las concentraciones de P total como TKN siguieron las tendencias establecidas por las pérdidas de sedimentos. Una disminución significativa en la concentración de sedimentos suspendidos fue observada con el tiempo en ambos tipos de coberturas del suelo, con pérdidas significativamente más altas en suelos al descubierto que en suelos con cobertura vegetal. En contraste, el nitrato exhibió una correlación negativa con las concentraciones de sólidos suspendidos. Aplicaciones de residuos de carnada de pollos parrilleros causaron un aumento significativo en las concentraciones de los constituyentes disueltos (i.e., P disuelto y N03-N) en la escorrentía, pero no así de otros constituyentes (i.e., P total y TKN) para los cuales las pérdidas de sedimentos representan un mecanismo significativo de transporte. La aplicación de residuos de carnada de pollos parrilleros redujo significativamente la pérdida en la concentración de sólidos suspendidos para cada categoría de cubierta vegetal, aunque una pérdida mucho mayor fue observada para el suelos al descubierto. La combinación de aplicación de alum y una buena cobertura de hierba (≥80%) reduce los estimados de carga de exporte de sedimentos suspendidos, P total y TKN en la escorrentía por más de un 95% comparado con los de los suelos al descubierto.