Sorption Model for Dissolved and Leachable Particulate Aluminium in the Great Ouse Estuary, England

The behaviour of dissolved Al in the Great Ouse estuary, in particular with respect to salinity, is complex. There is, however, evidence from field data as well as laboratory mixing experiments to suggest that flocculation and sorption mechanisms play important roles affecting the concentrations of dissolved Al during the early stages of estuarine mixing. In contrast, a near-buffering of dissolved Al occurs in the entire stretch of the estuary (salinity >0.2) with concentrations varying around 1.4 μg l⁻¹. This distribution and lack of variation with salinity is attributable to sorption processes which might dominate over other processes in these turbid estuarine waters (suspended particulate load 48–888 mg l⁻¹) impacting dissolved Al levels. Sorption models have been developed for both dissolved and leachable particulate Al concentrations in these waters. These observations provide compelling evidence of sorption processes that might be important in the geochemistry of Al in estuarine waters.     

Particulate matter grain-size characteristics and flocculation in a partially mixed estuary

The concentration and grain size of the natural and deflocculated inorganic suspended particulate matter were measured along the length of the Miramichi Estuary and interpreted with respect to flocculation and transport properties. Changes in particulate matter concentration are associated with regular changes in grain-size characteristics. In the turbidity maximum region of the estuary the suspended matter occurs mostly as large flocculated particles whereas, in the waters with lower particle concentrations, a larger proportion of the material occurs as fine material. At higher concentrations natural floc modes and inorganic grain modes vary simultaneously but at low concentrations the two modes vary inversely. This modal relationship and the variation in organic matter within the estuary is proposed to result from variation in inorganic—organic composition of flocs. Increase in settling rates due to flocculation is believed to increase the trapping effect of the estuarine circulation that produces the turbidity maximum.     

Lower Seine River and estuary (France) carbon and oxygen budgets during low flow

Ecological processes driving the oxygen budget were investigated in the downstream part of the Seine River and its estuary. Phytoplankton and bacterioplankton production were measured along longitudinal profiles (11 to 17 stations) in a range of low discharges from 300 m³ s⁻¹ in 1993 and 1995 to 140 m³ s⁻¹ in 1996. Values representative of the water column were based on investigations carried out during two tidal cycles. Net primary production was invariably greatest in the freshwater estuary, from Poses to Rouen (from 500 to 1,000 μg C l⁻¹ d⁻¹ between PK 202 and 240) and decreased sharply downstream (from 10 to 25 μg c l⁻¹ d⁻¹ between PK 250 and 310). This decrease was mainly due to the deterioration of the light conditions with the increase in depth and suspended matter concentrations. Heterotrophic activity was maximum in the reach where primary production declined. Judging by the production:respiration ratio (P:R), the system appeared clearly heterotrophic in the Seine River immediately downstream of the Paris region due to high allochthonous organic pollution by the incompletely treated Parisian effluents and in the part of the estuary characterized by intense degradation of autochthonous material. Because the effluents are not treated by a nitrification step, the oxygen consumption due to nitrification was much higher than expected from the P:R ratio. Oxidation of ammonium represented an oxygen consumption of between 1 and 14 g O₂ m⁻² d⁻¹, almost equalling the sum of heterotrophic respirations that were barely balanced by photosynthesis. The reaeration flux at the water-atmosphere interface was deduced from the calculations and a reaeration coefficient was estimated.     

Wind-driven estuarine turbidity maxima in Mandovi Estuary,central west coast of India

Systematic studies on the suspended particulate matter (SPM) measured on a seasonal cycle in the Mandovi Estuary, Goa indicate that the average concentrations of SPM at the regular station are ∼20mg/l, 5mg/l, 19mg/l and 5mg/l for June–September, October–January, February–April and May, respectively. SPM exhibits low-to-moderate correlation with rainfall indicating that SPM is also influenced by other processes. Transect stations reveal that the SPM at sea-end stations of the estuary are at least two orders of magnitude greater than those at the river-end during the monsoon. Estuarine turbidity maximum (ETM) of nearly similar magnitude occurs at the same location in two periods, interrupted by a period with very low SPM concentrations. The ETM occurring in June–September is associated with low salinities; its formation is attributed to the interactions between strong southwesterly winds (5.1–5.6ms⁻¹) and wind-induced waves and tidal currents and, dominant easterly river flow at the mouth of the estuary. The ETM occurring in February–April is associated with high salinity and is conspicuous. The strong NW and SW winds (3.2–3.7ms⁻¹) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum. The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension and deposition     

A Simple Floc-Growth Function for Natural Flocs in Estuaries

Natural flocs in an estuary grow with increasing time, salinity, suspended particulate matter concentration, and with decreasing turbulence. Although various theoretical and empirical functions for floc growth have been proposed in the literature, they are all complex. It is argued in this study that there should be a simple and general function of floc size D against time t, salinity S, suspended particulate matter concentration C, microscale η, and biochemical composition M. Theory and experiments seem to corroborate that average floc size responds systematically to its drivers. Moreover, the response is partly similar to all drivers: a lower plateau followed by a rise, and partly different: an upper plateau for t, S and a fall for C, η. Assuming drivers are independent, each curve is normalized around its rise. The drivers are joined into one variable X that holds each normalized driver with equal weight. The result is a function that gives floc size against this composite variable X. This composite variable in turn is a function of ambient conditions and the function predicts floc size for any set of ambient conditions. The case is presented here using linear segments, but eventually the logistic growth function is proposed.     

Suspended Matter,Chl-a,CDOM, Grain Sizes,and Optical Properties in the Arctic Fjord-Type Estuary,Kangerlussuaq, West Greenland During Summer

Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM), and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66°) in August 2007 along with optical properties. These comprised diffuse attenuation coefficient of downwelling PAR (K _d(PAR)), upwelling PAR (K _u(PAR)), particle beam attenuation coefficient (c _p), and irradiance reflectance R(−0, PAR). PAR is white light between 400 and 700 nm. The estuary receives melt water from the Greenland Inland Ice and stations covered a transect from the very high turbid melt water outlet to clear marine waters. Results showed a strong spatial variation with high values as for suspended matter concentrations, CDOM, diffuse attenuation coefficient K _d(PAR), particle beam attenuation coefficients (c _p), and reflectance R(−0, PAR) at the melt water outlet. Values of optical constituents and properties decreased with distance from the melt water outlet to a more or less constant level in central and outer part of the estuary. There was a strong correlation between inorganic suspended matter (SPMI) and diffuse attenuation coefficient K _d(PAR) (r ² = 0.92) and also for particle beam attenuation coefficient (c _p; r ² = 0.93). The obtained SPMI specific attenuation—K _d^*(PAR) = 0.13 m² g⁻¹ SPMI—and the SPMI specific particle beam attenuation—c _p^* = 0.72 m² g⁻¹—coefficients were about two times higher than average literature values. Irradiance reflectance R(−0, PAR) was comparatively high (0.09−0.20) and showed a high (r ² = 0.80) correlation with K _u(PAR). Scattering dominated relative to absorption—b(PAR)/a(PAR) = 12.3. Results strongly indicated that the high values in the optical properties were related to the very fine particle sizes (mean = 2–6 μm) of the suspended sediment. Data and results are discussed and compared to similar studies from both temperate and tropical estuaries.     

Aluminum in the macrotidal Yalujiang estuary: Partitioning of Al along the estuarine gradients and flux

Water samples were collected from the Yalujiang estuary in both flood periods (August 1992 and August 1994) and dry season (May 1996) and were analyzed for aluminum (Al). Al behaves non-conservatively in the Yalujiang estuary, and a significant loss (70–80%) in dissolved concentration is observed in the upper estuary, in spite of seasonal variation in water discharge and sediment load. About 0.4×10⁶, tons of Al is annually transported from Yalujiang to the estuary, of which the particulate pool clearly dominates. The particulate Al flux through the Yalujiang contributes 35% of the total Al input from Chinese rivers to the Yellow Sea. The data sets from size fractionation and C-18 SPE separation demonstrate that a large fraction of dissolved Al is in colloidal (≈50%) and organically complex (≈60%) forms in the Yalujiang. The observed scavenging from solution to particulate pools in the estuary is most likely through the flocculation of colloidal and organic-complexed Al, which results in a considerable change in dissolved-particulate partitioning, shown by laboratory mixing experiments. Exchange between dissolved and particulate phases is examined by analysis of K_d, the distribution coefficient. The empirical relationship of K_d with chlorinity and suspended matter concentrations was investigated with field observations and model simulations. The model indicated that K_d values of Al are inversely related to the amount of total suspended matter, but K_d-chlorinity plots show different features between dry and flood seasons.     

Dissolved and particulate trace metals and their partitioning in a hypoxic estuary: The Tanshui Estuary in Northern Taiwan

The distribution and partitioning of trace metals (Co, Cu, Fe, Mn, Ni, and Zn) between dissolved and particulate phases were studied in the Tanshui Estuary. The upper reach of the estuary is hypoxic and heavily polluted due to domestic and industrial discharges. The concentration ranges of dissolved and leachable particulate trace metals in the Tanshui Estuary were: Co: 0.3–6.1 nM, 1.8–18.6 mg kg⁻¹; Cu: 5–53 nM, 22–500 mg kg⁻¹; Fe: 388–3,364 nM, 1.08–6.67%; Mn: 57–2,914 nM, 209–1,169 mg kg⁻¹; Ni: 7–310 nM, 6–108 mg kg⁻¹; and Zn: 12–176 nM, 62–1,316 mg kg⁻¹; respectively. The dissolved concentrations of the metals were 2–35 times higher than the average values of the world river water. The distributions of dissolved and particulate studied metals, except Mn, in the estuary showed scattering, which could be attributed to the discharges from many industrial wastewater disposal works located in the upper tributaries. The daily input of dissolved metals from the disposal works to the Tanshui Estuary ranged from 0.1–0.4 tons. Dissolved Mn was nearly conservative in the region with salinity higher than 10 psu, while particulate Mn decreased in the region with salinity of 10–15 psu. The concentration increased significantly seawards, corresponding with the distribution of dissolved oxygen. The distribution coefficient (K_D) for Mn in the lower estuary was nearly three orders of magnitude higher than in the upper estuary. This phenomenon may be attributed to the diffusion of Mn from the anoxic sediment in the upper estuary and gradual oxidation into particulate Mn in the middle and lower estuary as the estuarine water became more oxygenated. The distribution coefficient for Cu decreased with increasing salinity. The percentages of trace metals bound by suspended particulate matter decreased in the following order: Fe>Zn, Cu>Co>Mn>Ni.     

The strength and fractal dimension characteristics of alum–kaolin flocs

Flocs generated by various shear forces exhibit different characteristics of size, strength and structure. These properties were investigated by employing a continuous optical monitoring and a microscope with CCD camera to directly monitor aggregation under six different shear intensities. The floc structure was characterized by the fractal dimension. The results showed that the flocculation index (FI) decreased from 1.16 at 20 rpm to 0.25 at 250 rpm and the floc size decreased from 550 μm to 150 μm, meantime, the FI value showed a good correlation with floc size. In order to determine the floc strength, two methods were used. One was the strength factor, ranging from 18.3% to 62.5%, calculated from FI curve, and the other was a theoretical value between 0.005 N/m² and 0.240 N/m², estimated by calculation. The floc strength increased with the G value in both cases. Furthermore, the fractal dimension increased with G and its value was between 1.30 and 1.63. The relation between fractal dimension and strength was also obtained.     

Narragansett Bay Hypoxic Event Characteristics Based on Fixed-Site Monitoring Network Time Series: Intermittency,Geographic Distribution,Spatial Synchronicity,and Interannual Variability

Low dissolved oxygen events were characterized in Narragansett Bay (NB), a moderate-size (370 km²) temperate estuary with a complex passage/embayment geometry, using time series from 2001 to 2006 at nine fixed-site monitoring stations. Metrics for event intensity and severity were the event-mean deficit relative to a threshold (mg O₂ l⁻¹) and the deficit-duration (mg O₂ l⁻¹ day; product of deficit and duration [day]). Hypoxia (threshold 2.9 mg O₂ l⁻¹) typically occurred intermittently from late June through August at most stations, as multiple (two to five per season) events each 2 to 7 days long with deficit-duration 2 to 5 mg O₂ l⁻¹ day. Conditions were more severe to the north and west, a pattern attributed to a north–south nutrient/productivity gradient and east–west structure of residual circulation. Spatial patterns for suboxic and severely hypoxic events (thresholds 4.8 and 1.4 mg O₂ l⁻¹) were similar. The view that different processes govern event variability in different regions, each influenced by local hydrodynamics, is supported by both weak spatial synchronicity (quantified using overlap of event times at different sites) and multiple linear regressions of biological and physical parameters against event severity. Interannual changes were prominent and season-cumulative hypoxia severity correlated with June-mean river runoff and June-mean stratification. Benthic ecological implications for areas experiencing events include: NB hypoxia classifies as periodic/episodic on a near-annual basis; highest direct mortality risk is to sensitive and moderately sensitive sessile species in the northern West Passage and western Greenwich Bay, with some risk to Upper Bay; direct risk to mobile species may be ameliorated by weak spatial synchronicity; and indirect impacts, including reduced growth rates and shifts in predator–prey balances, are very likely throughout the sampled area due to observed suboxic and hypoxic conditions.     

Transport and retention of suspended particulate matter and bacteria in the Humber-Ouse Estuary, United Kingdom, and their relationship to hypoxia and anoxia

Data are presented on dissolved oxygen (DO) concentrations and their relationship to salinity, suspended particulate matter (SPM), concentrations, and the turbidity maximum in the Humber-Ouse Estuary, United Kingdom, during summer 1995. Measurements in the upper Humber during March 1995 showed DO in the range 82% to 87% of saturation. Suspended particulate matter concentrations were <5000 mg l^?1 and salinity was in the range 0.5 to 12. In contrast, a pronounced DO sag occurred in the upper reaches of the Ouse during medium and spring tide, summer conditions. The DO minimum was essentially an anoxic level and was associated with the location of the turbidity maximum, at salinities between about 0.4 and 1.5. SPM concentrations at 1 m beneath the surface reached 25,000 mg l^?1 in the turbidity maximum, between about 20 km and 40 km from the tidal limit. Suspended particulate matter concentrations were much lower at neap tides, although dense suspensions of SPM (>60,000 mg l^?1) occurred within 1 m of the bed in the turbidity maximum region. A spring-neap record showed a dramatic and tidally controlled decrease in DO at very low salinities as the tides progressed from neaps to springs. An anchor station located down-channel of the turbidity maximum showed that about 95% of the variance in DO, which varied from 28% at low-water slack to 67% at high-water slack, could be explained in terms of salinity variation. At the up-channel margins of the turbidity maximum, DO increased from zero (anoxia) near high water to 60% near low water slack, in contrast to the behavior down-channel of the turbidity maximum. About 82% of the variance in DO could be explained in terms of salinity variations alone. Only 43% of the DO variance could be explained in terms of SPM alone. Up-channel of the turbidity maximum, SPM concentrations were relatively low (<3000 mg l^?1) and DO levels varied from 48% of saturation near high water to 83% near low water slack. About 76% of the variance in DO could be explained in terms of salinity variations alone. Within the turbidity maximum region, DO varied from <2% saturation on the early flood and late ebb and maximized around 7% at high water slack. About 63% of the variance in DO could be explained in terms of salinity variation alone. This increased to 70% when suspended particulate matter was taken into account. Only 29% of the DO variance could be explained in terms of suspended particulate matter alone. Because bacteria were likely to have been the cause of the observed reduction in DO, the numbers of bacteria, both free-living and attached to particles, were measured in the turbidity maximum region. Numbers of free-living bacteria were low and most of the bacteria were attached to sediment particles. There was a linear correlation between total bacterial number and suspended particulate matter concentration, suggesting that the strong DO demand was exerted locally as a result of bacterial activity associated with increased suspended particulate matter concentrations. An order of magnitude analysis of DO consumption within the Ouse’s turbidity maximum, based on the premise that DO depletion was directly related to suspended particulate matter concentrations and that DO addition was due to reaeration, indicates that complete deoxygenation could have occurred with an oxygen depletion rate of ～0.01 mg DO h^?1/g suspended particulate matter during the residence time of waters within the turbidity maximum (～7 d). This rate was sufficiently fast that anoxic to aerobic conditions were able to develop a spring-neap periodicity within the turbidity maximum, but too slow to generate substantial intratidal fluctuations in DO. This is in accordance with the observations, which show that relatively little of the intratidal variance in DO could be explained in terms of suspended particulate matter fluctuations, whereas most of the variance could be explained in terms of salinity, which behaved as a surrogate measure for the proximity of the turbidity maximum.     

Sediment dynamics of turbidity maximum in Changjiang River mouth in dry season

High-resolution current velocity and suspended sediment concentration (SSC) data were collected by using an Acoustic Doppler Current Profiler (ADCP) at two anchor stations and a cross-section in the South Channel of the Changjiang River mouth during meso and neap tides on Nov. 16, 2003. In addition, tidal cycle (13-hour) observation at two stations was carried out with traditional methods during the spring tide. Results indicated that resuspension occurred not only at the flood and ebb maximum, but also in the early phase of ebb in the meso and neap tide. When tidal current transited from high to ebb phase, current speed accelerated. Subsequently, fine-grained sediment with low critical threshold was resuspended and increased concentration. The river mouth area remained in siltation in the meso and neap tidal phase during the observation season, with calculated resuspension flux in the order of magnitude of 10⁻⁴–10⁻⁷ kg·m−2/s. Suspended sediment transport in the South Channel was dominated by freshwater discharge, but the Storks drift, vertical circulation and vertical shear effect due to tidal oscillation also played an important role in resuspension and associated sediment transport. In contrast, resuspension sediment flux in the spring tide was larger than that in meso and neap tide, especially at the ebb maximum and flood maximum. The present study revealed that intensive resuspension corresponded well with the larger current velocity during winter. In addition, the ‘tidal pumping’ effect and tidal gravity circulation were also vital for forming the turbidity maximum in the Changjiang River estuary.     

The Nature and Distribution of Particulate Matter in the Mandovi Estuary,Central West Coast of India

Systematic seasonal variations of suspended particulate matter (SPM) along a 44-km transect of the Mandovi estuary reveal that the concentrations of SPM are low at river-end stations, increase generally seaward, and are highest at sea-end stations of the estuary. An estuarine turbidity maximum (ETM) occurs at sea-end stations during June–September when river discharge is high and also in February–May when river discharge is low. These are the two windiest times of year, the former associated with the southwest monsoon and the latter characterized by a persistent sea breeze. The salinity vs. SPM plot shows that high SPM is a seaward deposit and skewed landward. Suspended matter comprised of floccules, fecal pellets, and aggregates that consist of clay and biogenic particles occur everywhere in the estuary. Diatoms are the most common and are of marine type at the sea-end and freshwater-dominated at river-end stations of the estuary. SPM is characterized by kaolinite- and smectite-rich clay mineral suites at the river- and sea-end stations, respectively. Smectite concentrations increase seawards with the increase in SPM content and are not influenced by salinity. Wind-driven waves and currents and biogeochemical processes at the mouth of estuary likely play an important role in the formation of ETM in resuspension and transformation of SPM into floccules and aggregates and in their upkeep or removal.     

Remotely sensed observations of the turbidity maximum in the highly turbid Humber Estuary, UK

The Humber Estuary, UK, divides into the Ouse and Trent estuaries at the so-called Apex within its upper reaches. Remotely sensed Compact Airborne Spectrographic Imager (CASI) images and boat measurements were used to observe a strong turbidity maximum in the upper Humber and Ouse during a spring tide in November 1995. Surface suspended particulate matter (SPM) concentrations during the late ebb, as estimated from the CASI data, increased from approximately 6 to 13 g I⁻¹ moving up-estuary into the Ouse. Greater SPM concentrations (∼10 g I⁻¹) were evident in the deeper channels of the Ouse, compared with shallower areas, possibly due to faster ebb currents there and differential down-estuary advection of the turbidity maximum. Ribbons, or streaks, of lower SPM and slightly cooler waters were observed. It appears that slightly cooler and lower turbidity waters from the confluent Trent estuary remained fairly distinct for distances of approximately 2 km down-stream of its confluence with the upper Humber and Ouse. These waters eventually broke into ribbon-like or streak-like structures within the higher SPM-laden and slightly warmer waters of the Humber. They were discernible for more than 5 km down-estuary of the confluence of the Humber, Ouse, and Trent. Boat measurements showed that the turbidity maximum occurred over a fairly restricted region of the upper Humber, between about 20 to 50 km from the tidal limit at high water. The turbidity maximum’s sediment load was largely suspended in the water column during stronger currents. SPM rapidly settled close to the bed during high water and low water slack periods. At these times, SPM concentrations in a thin, near-bed layer were >60 g I⁻¹ in the turbidity maximum region of the Ouse and >30 g 1⁻¹ in the upper Humber (where channel volumes were much greater). SPM within the turbidity maximum comprised very fine-grained material and its low organic content demonstrated that the SPM was essentially mineral, clastic sediment derived originally from erosion and decay of crustal rocks.     

Source and distribution of trace metals and nutrients in Narmada and Tapti river basins,India

The study was designed to establish the distributions of trace metals, dissolved organic carbon, and inorganic nutrients as well as to assess the extent of anthropogenic inputs into the Narmada and Tapti rivers. Water and sediment qualities are variable in the rivers, and there are major pollution problems at certain locations, mainly associated with urban and industrial centers. The metal concentrations of samples of the aquatic compartments investigated were close to the maximum permissible concentration for the survival of aquatic life, except for higher values of Cu (5–763 μg l⁻¹), Pb (24–376 μg l⁻¹), Zn (24–730 μg l⁻¹), and Cr (70–740 μg l⁻¹) and for drinking water except for elevated concentrations of metals such as Pb, Fe (850–2,060 μg l⁻¹), Cr, and Ni (20–120 μg l⁻¹). In general, the concentrations of trace metals in the rivers vary down stream which may affect the “health” of the aquatic ecosystem and may also affect the health of the rural community that depends on the untreated river water directly for domestic use. The assessment of EF, I _geo, and PLI in the sediments reveals overall moderate pollution in the river basins.     

A variable turbidity maximum in the Kennebec estuary, Maine

A turbidity maximum has been observed in the Kennebec estuary during mode rate and low flow conditions near the upstream limit of salinity intrusion. Hydrographic, ADCP, and transmissometer data were collected at different river flow levels and seasons during 1995–1998. The location of the tip of the salt intrusion changes dramatically and during high runoff may be flushed from the channel of the estuary along with the accumulated particles in the turbidity maximum. It is hypothesized that the estuarine turbidity maximum (ETM) was absent 18% of the time with occurrences in all seasons during 1993–1999 based on river flow volumes from the Kennebec and Androscoggin Rivers throughout the study period. When the flow is moderate and low, which occurred 73% of the time on average, a region of high turbidity can be found as far as 40 km upstream of the mouth. Suspended particulate loads are low in the ETM, on the order of tens of mg l⁻¹ and may vary with the length of time that the ETM has been present.     

水力紊动条件对泥沙絮体分形结构的影响

在含沙量为85 kg/m3的悬浊液中投加阳型高分子聚合物,改变水力紊动条件:剪切速率(r)或速度梯度(G)与剪切时间(t),借助沉降技术、图像分析技术及分形特性定量表征参数“分维”探讨了架桥絮体结构的演变规律,得出分形结构达最佳状态时的水力紊动强度(Gt)值存在两个临界值:快速絮凝阶段和慢速絮凝阶段。实验发现,不同含沙量架桥絮体分形结构致密度最高时所需的最佳Gt值相近。含沙量越低,r或G值应降低,t值增加,分维值降低。另外,相同含沙量无机混凝剂絮体与高分子架桥絮体分形结构达最佳时,前者所需Gt值高,对应的G值低,t需延长,絮体平均质量分维(D₃)值高,但絮体结构脆弱。     

Drinking water quality in villages of southwestern Haryana,India: assessing human health risks associated with hydrochemistry

The chemical quality of groundwater of western Haryana, India was assessed for its suitability for drinking purposes. A total of 275 water samples were collected from deep aquifer based hand-pumps situated in 37 different villages/towns of Bhiwani region. The water samples were analyzed for different physico-chemical properties, e.g., pH, total dissolved solids (TDS), total harness (TH), total alkalinity (TA), calcium, magnesium, carbonate, bicarbonate, sulphate, chloride and fluoride concentrations. In this study, the average TDS content was greater ranging 1,692 (Bhiwani block) to 2,560 mg l⁻¹ (Siwani block), and other important parameters of water, e.g., TA (442–1,232 mg l⁻¹), TH (437–864 mg l⁻¹) and bicarbonate (554–672 mg l⁻¹), were also higher than maximum permissible limit by WHO or BIS. The fluoride appeared as a major problem of safe drinking water in this region. We recorded greater fluoride concentration, i.e., 86.0 mg l⁻¹ from Motipura village that is highest fluoride level ever recorded for Haryana state. The average fluoride concentration ranged between 7.1 and 0.8 mg l⁻¹ in different blocks of western Haryana. On the basis of fluoride concentration, Siwani block showed the maximum number of water samples (84% of total collected samples) unsuitable for drinking purposes (containing fluoride >1.5 mg l⁻¹) followed by Charki Dadri block (58%), Bhiwani block (52%), Bawani Khera block (33%) and Loharu block (14%). This study clearly suggest that some health deteriorating chemicals in drinking water were at dangerous level and; therefore, water quality could be a major health threat for local residents of western Haryana. The high fluoride level in drinking water has posed some serious dental health risks in local residents.     

Water quality analysis of a freshwater diversion at Caernarvon, Louisiana

Since 1991, Mississippi River water has been diverted at Caernarvon, Louisiana, into Breton Sound estuary. Breton Sound estuary encompasses 1100 km² of fresh and brackish, rapidly subsiding wetlands. Nitrite + nitrate, total Kjeldahl nitrogen, ammonium, total phosphorus, total suspended sediments, and salinity concentrations were monitored at seven locations in Breton Sound from 1988 to 1994. Statistical analysis of the data indicated decreased total Kjeldahl nitrogen with associated decrease in total nitrogen, and decreased salinity concentrations in the estuary due to the diversion. Spring and summer water quality transects indicated rapid reduction of nitrite + nitrate and total suspended sediment concentration as diverted Mississippi River water entered the estuary, suggesting near complete assimilation of these constituents by the ecosystem. Loading rates of nitrite + nitrate (5.6–13.4 g m⁻² yr⁻¹), total nitrogen (8.9–23.4 g m⁻² yr⁻¹), and total phosphorus (0.9–2.0 g m⁻² yr⁻¹) were calculated along with removal efficiencies for these constituents (nitrite + nitrate 88–97%; total nitrogen 32–57%; total phosphorus 0–46%). The low impact of the diversion on water quality in the Breton Sound estuary, along with assimilation of TSS over a very short distance, suggests that more water may be introduced into the estuary without detrimental affects. This would be necessary if freshwater diversions are to be used to distribute nitrients and sediments into the lower reaches of the estuary, in an effort to compensate for relative sea-level rise, and reverse the current trend of rapid loss of wetlands in coastal Louisiana.     

Planktonic and whole system metabolism in a nutrient-rich estuary (the Scheldt estuary)

Planktonic gross primary production (GPP), community respiration (CR), and nitrification (NIT) were measured monthly in the Scheldt estuary by the oxygen incubation method in 2003. No significant evolution of planktonic GPP was observed since the 1990s with high rates in the freshwater area (salinity 0; 97±65 mmol C m⁻² d⁻¹) decreasing seaward (22–37 mmol C m⁻² d⁻¹). A significant decrease of NIT was observed with regard to previous investigations although this process still represents up to 20% of total organic matter production in the inner estuary. Planktonic CR was highest in the inner estuary and seemed to be mainly controlled by external organic matter inputs. Planktonic net community production was negative most of the time in the estuary with values ranging from −300 to 165 mmol C m⁻² d⁻¹. Whole estuary net ecosystem production (NEP) was investigated on an annual scale using the results mentioned above and published benthic metabolic rates. A NEP of −39±8 mmol C m⁻² d⁻¹ was estimated, which confirms the strong heterotrophic status of this highly nutrified estuary. NEP rates were computed from June to December 2003 to compare with results derived from the Land-Ocean Interaction in the Coastal Zone budgeting procedure applied to dissolved inorganic phosphorus and carbon (DIP and DIC). DIP budgets failed to provide realistic estimates in the inner estuary where abiotic processes account for more than 50% of the nonconservative DIP flux. DIC budgets predicted a much lower NEP than in situ incubations (−109±31 versus −42±9 mmol C m⁻² d⁻¹) although, as each approach is associated with several critical assumptions, the source of this discrepancy remains unclear.