Atmospheric oxidation of the pyritic waste rock in Maardu, Estonia. 1 field study and modelling

 A field survey and modelling of the oxidation and carbonate buffering reactions inside the alum-shale-containing waste rock dumps located in Maardu, Estonia, was accomplished. In the slope areas, the shale has been altered at high temperatures due to the spontaneous combustion and the pyritic acidity has been eliminated through migration of SO_x gases out from the dump. In the central parts of the waste rock plateaus, low temperature pyrite oxidation fronts develop towards the dump depth and towards the centres of individual shale lumps. The main secondary phases precipitating in the weathering profile are gypsum, ferric oxyhydroxide, K-jarosite and smectite. The respective field data made it possible to calibrate the two-stage oxygen diffusion model and the characteristic pyrite oxidation rate 0.06–0.08 mol of pyrite reacted per kg of available water (pyrox/H₂O value) was estimated to describe the first tens of years of dump performance. The model is capable to compare different shale disposal strategies that are illustrated with two case scenarios. The buffering of sulphuric acid by Mg-calcite appears to be an incongruent reaction with gypsum precipitating that leads to the build-up of the high Mg/Ca ratio in the leachate. Application of the Mg/Ca method estimates the pyrox/H₂O value in the range of 0.05–0.14 mol/kg. Received: 26 January 1999 · Accepted: 23. February 1999     

The groundwater resources and sustainable yield of Cheju volcanic island, Korea

 Hydrogeologic data of 455 water wells comprising geologic logs, water qualities, and aquifer test results are analyzed to determine hydrogeological characteristics, water quality, and sustainable yield of the groundwater resources of Cheju volcanic island. The groundwater of the island occurs in unconsolidated pyroclastic deposits and clinkers interbedded in highly jointed basaltic and andesitic rocks as high-level, basal, and parabasal groundwater under unconfined conditions. The total storage of groundwater is estimated at about 44 billion m³. The average transmissivity and specific yield of the aquifer are at about 0.34 m² s^–1(29300 m² day^–1) and 0.12, respectively. The average annual precipitation is about 3.39 billion m³, of which 1.49 billion m³– equivalent to 44.0% of the total annual precipitation – is recharged into aquifers, with 0.638 billion m³ year^–1 of runoff and 1.26 billion m³ year^–1 of evapotranspiration. Based on a groundwater budget analysis, the sustainable yield is estimated at about 0.62 billion m³ year^–1, equivalent to 41.6% of annual recharge. A low-permeability marine sedimentary formation (Sehwari formation), composed of loosely cemented sandy silt, was recently found to be situated at 120±68 m below mean sea level. If the said marine sediment is distributed as a basal formation of the freshwater zone of the island, most of its groundwater will be of parabasal type. So the marine sediment is one of the most important hydrogeological boundaries and groundwater occurrences in the area. Received: 16 January 1997 / Accepted: 16 June 1997     

Benthic nutrient remineralization in a coastal lagoon ecosystem

In situ measurements of the exchange of ammonia, nitrate plus nitrite, phosphate, and dissolved organic phosphorus between sediments and the overlying water column were made in a shallow coastal lagoon on the ocean coast of Rhode Island, U.S.A. The release of ammonia from mud sediments in the dark (20–440 μmol per m² per h) averaged ten times higher than from a sandy tidal flat (0–60 μmol per m² per h), and while mud sediments also released nitrate and phosphate, sandy sediments took up these nutrients. Fluxes of nutrients from mud sediments, but not from sandy areas, markedly increased with temperature. Ammonia release rates for mud sediments in the light (0–350 μmol per m² per h) were lower than those in the dark and it is estimated that some 25% of the ammonia released to the water column on an annual basis may be intercepted by the benthic microfloral community. Estimates of the annual net exchange of nutrients across the sediment-water interface, weighted by sediment type for the lagoon as a whole, showed a release of 450 mmol per m² of ammonia, 5 mmol per m² of phosphate, 5 mmol per m² of dissolved organic phosphorus, and an uptake of 80 mmol per m² of nitrate. Although rates of ammonia and nitrate exchange were comparable to those described for the deeper heterotrophic bottom communities of nearby Narragansett Bay, rates of benthic phosphate release were significantly lower. On an annual basis the Bay benthos released approximately 20 times more inorganic phosphate per unit area than did the lagoon benthos. As a result., the N/P ratio for the flux from the sediments was 74∶1 in the lagoon, compared with 16∶1 in “average” marine plankton and 8∶1 for the benthic flux from Narragansett Bay. The lack of remineralized phosphate in the lagoon, is reflected in water, column phosphate concentrations (always <1 μm) and water column N/P ratios (annual N/P=27) and suggests that the lagoon may show phosphate limitation rather than the nitrogen limitation commonly associated with marine systems.     

Predictive modelling of dump water impact on the surroundings of the lignite dump site Jänschwalde (Eastern Germany)

Open cast mining of lignite leads to dumps containing highly mineralised pore waters. To predict the impact of the dump waters on the undisturbed aquifers two steps are necessary. (1) The prediction of dump water quality at times when steady state flow conditions will be established. (2) The simulation of the dump ground water migration with a model that is able to handle the complexity of the homogeneous and heterogeneous interactions of the migration process.For the investigated site Jänschwalde, which is still dewatered, a chemical mass balance was performed. The predicted alkalinity potentials exceed acidity potentials for the dump as a whole. The distribution of these parameters show high alkalinity potentials for the northern part.In order to model the migration process the transport code PCGEOFIM^® [Anwenderdokumentaion, IBGW Leipzig, (in German)] was coupled with the geochemical equilibrium code PHREEQC [USGS, Water-Resources Investigations Report]. This was done to simulate redox reactions, mineral dissolution and precipitation, and cation exchange in the ground water zone. The model is verified by a column flow test. The results of the simulations show a small effect of the migrating dump waters on the quartenary aquifer with respect to acidity changes. This results from calcite buffering and cation exchange. The impact on the quartenary aquifer by sulphate is much higher.     

Ammonium release characteristics of the sediments from the shallow lakes in the middle and lower reaches of Yangtze River region,China

Ammonium release from sediments has significant effects on the water quality in eutrophic lakes. In this study, the ammonium release kinetics and adsorption–desorption processes were investigated in 13 sediments of 6 shallow lakes from the middle and lower reaches of Yangtze River region, China. The results show that First Order Model best described the ammonium release process, the maximal release capacity had a strong correlation with organic matter (OM), cationic exchange capacity (CEC), total nitrogen (TN) and total phosphorus (TP). But it only had a weak correlation with Fe, Ca and Al. The ammonium release capacity in more polluted sediments was higher than that in less polluted sediments. The average release rate within 0–5 min was the highest among the experimental period, the amount released within 0–5 min accounted for approximately 50–70% of the total release capacity. The ammonium release rate had a significant and positive correlation with OM. But it did not have a strong correlation with TN, TP, Fe, Ca and Al. The ammonium potential release capacity (obtained when the water/sediment ratio was about 2,500) had strong and positive relation with OM and maximal release capacity, and it may provide useful information for the sediment release risk assessment. Henry Model best described the ammonium sorption isotherms, and ammonium adsorption–desorption equilibrium concentration can be considered as the ammonium release threshold to assess the release risk in the sediments.     

Toxic metal contamination in the lateral lakes of the Coeur d'Alene River valley, Idaho

 The 11 lateral lakes of Coeur d'Alene River valley in northern Idaho have received heavy metal contamination from over a century of upstream mining. The lateral lakes lie within the flood plain of the Coeur d'Alene River, and in their bottom sediments is preserved a stratigraphic record of the upstream mining operations. To characterize the contaminated sediments in the lateral lakes, sampling techniques, including the Livingston piston corer and the Huttenen freeze box, have been developed by Quaternary geologists to preserve the vertical stratigraphy in the samples. From 26 cm to over 55 cm of undisturbed tailing sediments, commonly with “varve-like” features, have been found in each of the lateral lakes, with maximum concentrations by weight of lead at 3.8%, zinc at 3.4%, arsenic at 340 mg/kg, cadmium at 120 mg/kg and mercury at 7 mg/kg. The contamination in the lakes appears to be restricted to the shallow subsurface and heavy metal concentrations generally drop to background levels within a meter of depth. Received: 22 May 1998 · Accepted: 21 September 1998     

Hydrogeochemical genesis of groundwaters with abnormal fluoride concentrations from Zhongxiang City,Hubei Province,central China

The groundwaters from Zhongxiang City, Hubei Province of central China, have high fluoride concentration up to 3.67 mg/L, and cases of dental fluorosis have been found in this region. To delineate the nature and extent of high fluoride groundwaters and to assess the major geochemical factors controlling the fluoride enrichment in groundwater, 14 groundwater samples and 5 Quaternary sediment samples were collected and their chemistry were determined in this study. Some water samples from fissured hard rock aquifers and Quaternary aquifers have high fluoride concentrations, whereas all karst water samples contain fluoride less than 1.5 mg/L due to their high Ca/Na ratios. For the high fluoride groundwaters in the fissured hard rocks, high HCO₃ ⁻ concentration and alkaline condition favor dissolution of fluorite and anion exchange between OH⁻ in groundwater and exchangeable F⁻ in some fluoride-bearing minerals. For fluoride enrichment in groundwaters of Quaternary aquifers, high contents of fluoride in the aquifer sediments and evapotranspiration are important controls.     

Environmental impact of mining waste disposal on a tropical lowland river system: a case study on the Ok Tedi Mine, Papua New Guinea

The 1000 km long Ok Tedi/Fly River system receives about 66 Mt/year of mining waste from the Ok Tedi copper-gold porphyry mine. Mine input has increased the suspended sediment load of the Middle Fly River about 5–10 times over the natural background. A significant yet unknown amount of copper-rich material deposits unevenly in the extensive tropical lowland floodplain. Recent alluvial sediments of the Fly River floodplain have copper contents of 620 mg/kg (±1σ: 430–900), whereas the regional background is 40 mg/kg (±σ: 25–60). This pattern is mirrored and enhanced by the gold dispersal pattern with a 7 ppb Au background versus a 140–275 ppb population in mine-derived material. Very high deposition rates (around 4 cm/y) of mine-derived sediment were determined in locations close to the creeks and channels which link the Fly River with the outer floodplain. A thin layer of 1–5 cm of copper-rich material (400–900 mg/kg Cu) was usually found on the bottom of drowned (tributary) valley lakes. Average dissolved copper content in waters of the inner floodplain is around 9 μg/l (±1σ: 5–14) as compared to unpolluted water from the outer floodplain with < 2 μg/l Cu. The present Fly River water, about 600 km downstream of the mine site, has concentrations of 17 ± 3 μg/l dissolved Cu. Received: 30 June 1996 / Accepted: 9 January 1997     

Geochemical factors controlling accumulation of major and trace elements in Greenland coastal and fjord sediments

 The major (Al, Ti, Ca, Mg, Fe, Mn, Si) and trace element (Cd, Cr, Cu, Hg, Li, Ni, Pb, V, Zn) concentrations in surficial (<20 cm) sediments from fjords and open coastal waters around Greenland have been determined. Regionally, high concentrations of Fe, Ti, Mg, Cr, Cu, Ni, and V occur in some west and east coast sediments, but they appear to be natural in origin, as there is no indication of anthropogenic influence. Chemical partition indicates that most of the heavy metals are structurally bound in various silicate, oxide, and sulfide minerals. These host minerals occur more or less equally in the coarse and fine sediment fractions (material >63 μm and <63 μm) and have accumulated at the same rate as other detrital clastic material. Provenance and glaciomarine deposition are the main factors controlling the abundance and distribution of the major and trace elements. The chemical composition reflects the mineralogical differences in the provenance of glacial marine material deposited by water and ice adjacent to Greenland. The main source of the sediments enriched in Ti, Fe, Mg, Cr, Cu, Ni, and V appears to be material derived from the volcanic rocks of the Mesozoic-Tertiary Provinces of Greenland by glacial erosion. Received: 26 June 1995 · Accepted: 11 August 1995     

Water quality and sediment geochemistry in lakes of Yunnan Province, southern China

 Yungui Plateau lakes in southwestern China are economically important, although few have been studied previously. Water and sediments of 24 lakes throughout Yunnan Province were sampled in October 1994. We describe the chemical and physical characteristics of Yunnan lakes, and address effects of regional geology and human influences on water quality and sediment type. Water quality differs between deep Yunnan lakes of tectonic origin and shallow solution basins. Shallow lakes generally have higher nutrient concentrations and appear to be more susceptible to riparian disturbance than deeper lakes. Shallow lakes with high macrophyte standing crops, nevertheless, exhibit nutrient-poor waters. Principal ions Ca²⁺, Mg²⁺, and HCO₃ ^– reflect regional carbonate geology, except in Cheng Hai, which is a sodium bicarbonate lake. Specific conductance and δ¹⁸O are positively correlated, indicating that evaporation concentrates both solutes and ¹⁸O. Large, shallow lakes in southeastern Yunnan exhibit ¹⁸O-enriched waters because of substantial evaporation, whereas small, deep lakes are ¹⁸O-depleted. Lake waters are ¹⁸O-depleted in small, shallow basins that receive substantial rainwater input relative to their small volumes. ¹⁸O enrichment in Cheng Hai suggests that a recent 5-m water-level decline in this lake was caused by increased evaporation or diversion of freshwater inflow. Yunnan watersheds have undergone substantial deforestation, agricultural cultivation, soil erosion, and industrialization. Limnetic nutrient concentrations indicate that human activities have affected water quality. Organic matter content is low in sediments because of increased non-carbonate, clastic sediment yield from watersheds. Environmental policies are needed to balance ecological contraints with economic activities that impact water quality. Received: 1 July 1996 / Accepted: 2 October 1996     

Natural and anthropogenic influences on the geochemistry of Quaternary lake sediments from Holzmaar, Germany

 The accumulation of heavy metals and trace elements has been investigated in a well laminated sequence of Holocene and late Pleistocene lake sediments composed of diatomaceous gyttja, tuff and silt and clay sediments. Varve chronology of the annually deposited gyttja yielded a continuous high-resolution time sequence and allowed the absolute age dating of the sediment. Fluxes of elements remained largely uniform from the late Pleistocene into the Holocene (12 867–2 364 VT years ago; VT: varve time, years before 1950). Higher trace element and heavy metal fluxes occur from 2 322 to 862 VT years ago and reached their maxima in the uppermost sediments (<845 VT years ago). These increasing element fluxes correlate with increasing inputs of clastic material. The changing accumulation rates are the result of elevated soil erosion in the lake catchment caused by human settlement, deforestation and agricultural activities. Thus disturbances of the natural geochemical cycles of the Holzmaar region have occurred since the beginning of the Iron Age and especially since the beginning of the Middle Ages. Received: 29 May 1996 · Accepted: 19 August 1996     

Nutrient (P, N) dynamics in the southwestern Kattegat, Scandinavia: sedimentation and resuspension effects

 The yearly nutrient supply from land and atmosphere to the study area in SW Kattegat is 10 900 tons of N and 365 tons of P. This is only few percent of the supply from adjacent marine areas, as the yearly transport through the study area is 218 000 tons of N and 18 250 tons of P. Yearly net deposition makes up 1340 tons of N (on average 2.5 g m^–2 yr^–1) and 477 ton of P (on average 0.9 g m^–2 yr^–1). Shallow-water parts of the study area have no net deposition because of frequent (>35% of the year) resuspension. Resuspension frequency in deep water is <1% of the year. Resuspension rates, as averages for the study area, are 10–17 times higher than net deposition rates. Because of resuspension, shallow-water sediments are coarse lag deposits with small amounts of organic matter (1.1%) and nutrients (0.04% N and 0.02% P). Deep-water sediments, in contrast, are fine grained with high levels of organic matter (11.7%) and nutrients (0.43% N and 0.15% P). Laboratory studies showed that resuspension changes the diffusive sediment water fluxes of nutrients, oxygen consumption, and penetration into the sediment. Fluxes of dissolved reactive phosphate from sediment to water after resuspension were negative in organic-rich sediments (13.2% organic matter) with low porosity (56) and close to zero in coarse sediments with a low organic matter content (2.3%) and high porosity (73). Fluxes of inorganic N after resuspension were reduced to 70% and 0–20% in relation to the rates before resuspension, respectively. Received: 10 July 1995 · Accepted: 19 January 1996     

Diagenetic formation of gypsum and dolomite in a cold‐water coral mound in the Porcupine Seabight,off Ireland

Authigenic gypsum was found in a gravity core, retrieved from the top of Mound Perseverance, a giant cold‐water coral mound in the Porcupine Basin, off Ireland. The occurrence of gypsum in such an environment is intriguing, because gypsum, a classic evaporitic mineral, is undersaturated with respect to sea water. Sedimentological, petrographic and isotopic evidence point to diagenetic formation of the gypsum, tied to oxidation of sedimentary sulphide minerals (i.e. pyrite). This oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments. The oxidation of pyrite produced acidity, causing carbonate dissolution and subsequently leading to pore‐water oversaturation with respect to gypsum and dolomite. Calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21·6% and 28·6% of the sulphate incorporated into the gypsum derived from pyrite oxidation. The dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment‐water interface. Thus, authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate‐rich sediments. These observations demonstrate that fluid flow, steered by environmental factors, has an important effect on the diagenesis of coral mounds.     

Vertical Profiles of Major Organic Geochemical Constituents and Extracellular Enzymatic Activities in Sandy Sediments of Aransas and Copano Bays, TX

Vertical distribution patterns of organic geochemical constituents and the enzymes aminopeptidase and β-glucosidase provide insights about the nature and reactivity of sediment organic matter in the sandy sediments of two shallow “South Texas” estuaries. Sediment total organic carbon (TOC) δ¹³C values indicated that the organic matter (OM) was derived more from a mixture of seagrass and phytoplankton than from terrigenous OM. Down-core amounts of TOC and total nitrogen (TN) were <0.2% of dry weight, respectively. Enzyme activities were highest near surface and ranged from 25 to 1 μM/h for aminopeptidase as compared to 5 to 0.2 μM/h for glucosidase. In Aransas Bay, aminopeptidase activity correlated with sediment TN content (r _s = 0.30) and β-glucosidase with TOC content (r _s = 0.27). In Copano Bay, aminopeptidase correlated with TOC, TN, and carbohydrate content (r _s = 0.89, 0.90, and 0.83, respectively). Variations of glucosidase activity also related positively to TOC, TN, and total carbohydrate content (r _s = 0.68, 0.77, and 0.48, respectively). Overall, enzyme activities in these low OM, sandy sediments resembled those for other benthic marine environments.     

Application of allochthonous organic carbon and phosphorus forms in the interpretation of past environmental conditions

Organic matter in sediments, for instance, carbon, nitrogen and phosphorus, can be used to reconstruct the paleoecological and pollution history of lakes and their catchment basins. In this paper, the contents of allochthonous organic carbon (allochthonous OC) and autochthonous organic carbon (autochthonous OC) in sediment cores taken from Wuliangsuhai Lake and Daihai Lake in northern China are quantified by using a binary model, and phosphorus forms in the sediment cores from the two lakes are extracted by sequential extraction techniques. The results indicate that the palaeoenvironment and paleoclimate of Daihai Lake and its catchment basin in the recent 250 years can be well reconstructed based on the content of allochthonous OC. The climate was relatively humid and warm in the period of 1865–2005, while relatively dry and cold in the period of 1765–1865. The sedimentary information of allochthonous OC in the 22–42-cm portion of the sediment cores in Daihai Lake corresponds to the final cold fluctuation of the Little Ice Age that occurred since the Middle Holocene. The difference of phosphorus forms in the sediment cores between the two lakes indicates that phosphorus input to the lakes and the correlation between phosphorus forms and distribution and the changes of environment are influenced by the eutrophication mechanisms and environmental conditions of the two lakes.     

A possible varving mechanism for meromictic lakes

A variety of mechanisms have been proposed to explain how light and dark couplets are formed in the profundal sediments of meromictic lakes but none of these explanations acknowledges the significance of the sudden and massive mortality of mixolimnetic anaerobic bacteria. Data collected from sedimentation chambers suspended below the chemocline in a small meromictic lake indicate that a massive mortality of photosynthetic bacteria was induced by a sudden intrusion of partially oxygenated water into the anaerobic lower mixolimnion. The resulting deposition of anaerobic bacteria (0.45 mg dry wt cm^?2 day^?1) contributed 60% of the annual sediment influx during a 14-day period. It is postulated that the sudden sedimentation of the anaerobic bacteria inhabiting the lower mixolimnion of some meromictic lakes contributed to the formation of the dark-colored laminae in the sediments of these lakes.     

Inorganic pollutants in the Padma River, Bangladesh

The water and bed-sediment pollution status of the Padma River was determined by analysis of representative samples for selected metals and ions. Water and bed-sediment samples were collected at a T-dam, Rajshahi, Bangladesh, for 7 months. Water and silt-metal content analysis was performed using atomic absorption spectrophotometry or other analytical methods. The data showed the variation of the metal ion-levels in water as follows: Ca 17.11–48.37 ppm, Na 17.51–20.09 ppm, K 1.00–3.60 ppm, Cr 2.80–7.00 ppm, and SO₄ 4.17–5.48 ppm; in bed sediment, the levels were Cr 35–1050 ppm and Pb 12–48 ppm. The occurrence of Na, K and Ca was in the normal range (US EPA permissible limit), but the levels of Cr in water were much higher than the permissible limit. The SO₄ ion content was well below the pollution level. The concentration of Pb in the bed sediment was within the permissible limit for the standard International Atomic Energy Agency (IAEA) Soil-5a, but the concentration of Cr in the bed sediment was significantly higher than the permissible limit for the standard IAEA Soil-5a. Thus the Padma river water was polluted with Cr. The occurrence of some ions showed a monthly variation. Received: 19 August 1999 · Accepted: 12 October 1999     

Effects of Seagrass Rhizospheres on Sediment Redox Conditions in SE Asian Coastal Ecosystems

We examined the rhizosphere structure of 14 seagrass meadows (seven mixed, three Enhalus acoroides, two Zostera japonica, one Thalassia hemprichii, and one Halophila ovalis) in the Philippines and Vietnam and tested their effect on sediment redox potential by comparing the redox potential in vegetated vs unvegetated sediments. The effect of seagrass photosynthesis on sediment redox potential was tested in an E. acoroides meadow during a short-term (2-day) clipping experiment. In all the meadows, the centroidal depth (i.e., depth comprising 50%) of seagrass belowground biomass was within the top 15 cm sediment layer. Redox potentials in vegetated sediments tended to be higher than those in adjacent unvegetated ones; sediment redox potential anomaly ranged from −61 to 133 mV across the meadows. The centroidal depths of positive redox potential anomaly and seagrass root biomass were significantly correlated across the meadows investigated (type II regression analysis, slope = 0.90, lower confidence limit [CL] = 0.42 upper CL = 1.82, R ² = 0.59, p < 0.01). Experimental removal of E. acoroides leaves resulted in a decrease in rhizosphere redox potential by 20 mV, further confirming the positive effect of seagrass roots and rhizomes on sediment redox potential and, thus, the general conditions for microbial processes in the coastal zone.     

Environmental pollution of Udaisagar lake and impact of phosphate mine, Udaipur, Rajasthan, India

 The study of water chemistry and sediment core samples from Udaisagar lake in Rajasthan has revealed high phosphate contents; 186 and 236 μg/l in surface and sub-surface waters and in core samples 0.157 wt % P₂O₅, low D.O. 4.61 and 3.50 mg/l on average in surface and depth waters and high E.C. 1316 and 1395 μs/cm and higher sedimentation rate 8.90 mm/year in this lake compared to other lakes in the vicinity. The enormous and wide-spread growth of algal bloom in lake water and Ahar river and occasional fish mortality are indications of eutrophic conditions prevailing in the lake. Such a situation is developing due to the discharge of pollutants from phosphorite mines, chemical factories, distillary, sewage and domestic waste from settlements, hotels throughout the length of River Ahar which during its journey receives and finally discharges pollution in this lake. This renders the water unhygenic for human consumption and deleterious to aquatic life. Received: 27 January 1998 · Accepted: 28 September 1998     

Phosphorus Speciation and Sedimentary Fluxes in Hypersaline Sediments of the Guerrero Negro Salt Evaporation Area,Baja California Sur,Mexico

In the past several decades, the techniques used to discern the different sedimentary fractions of P have been refined. This has allowed for a better understanding of P burial of the different P fractions and diagenetic reactions and, ultimately, the constraining of P residence time in the oceans. P sequential extraction was performed on eight sediment cores (between 16 and 24 cm deep) collected along a salinity gradient from the Ojo de Liebre Lagoon and the salt evaporation saltern of Guerrero Negro, Baja California Sur, Mexico in order to determine, under purely diagenetic conditions (in the absence of anthropogenic activities and biogenic sediment reworking), the fractionation and flux of P to the sediments. The majority of P was found in the authigenic fraction (37 ± 5.4% to 53 ± 8.9%), with P associated to organic matter comprising the overall smallest percentage (0.25 ± 0.43% to 21 ± 6.0%) relative to total P. The average flux of total P to the sediments for all the sites was found to be (451 ± 127) × 10⁻⁴ mol m⁻² year⁻¹, up to several orders of magnitude greater than those found in other studies. It is concluded that P is most likely transformed from P associated to organic matter to the authigenic mineral phase and that P was retained in the sediments in its mineral form rather than in reactive forms. This particular study area has the ability to retain large quantities of P in the sediments.