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Interpretation of the potential bioavailability of phosphorus forms and fractions indicates some of the P entering lakes may have a limited effect on lake productivity. Some P sources, such as land runoff, are often high in particulate P, significant portions of which cannot be utilized in the growth of algae and higher plants. Based on existing information (mostly from Great Lakes studies), potentially bioavailable P in tributaries generally does not exceed 60% of the total P and is often considerably less. Potentially bioavailable P is shown to correspond to the dissolved reactive P (DRP) plus the fraction of particulate inorganic P obtained by extraction with 0.1NNaOH. Whether potentially bioavailable particulate P actually becomes available in a receiving water depends on factors such as the receiving‐water DRP concentration and the position (location) of the particle in the water. A mathematical model, combining two classical modeling approaches, is used to illustrate the importance of positional limitation. Consideration of bioavailability in eutrophication‐control strategies should lead to more cost‐effective management.

A simplified method for the analysis of total P(TP), total dissolved P(TDP) and dissolved reactive P(DRP) in multiple water samples has been developed. The reported modification utilizes a single digestion reagent and a single “mixed reagent” to eliminate neutralization, transfer and dilution steps normally required in total P analyses. The method results in a 70 percent decrease in analysis time for multiple samples, a reduction in the glassware required, and about a 30 percent increase in sensitivity. The method can be directly applied to water samples with P levels of 2 to 1100 μg P/l. Reproducibility and precision measurements compare to or exceed commonly used P techniques.

Degradation of the insecticide diazinon was followed in acid soil‐free systems and in soil systems. The mechanism of diazinon degradation in soils is a partial chemical hydrolysis with formation of 2‐isopropyl‐4‐methyl‐6‐hydroxypyrimidine and diethyl thiophosphoric acid; hydrolysis in soils is adsorption rather than acid catalyzed. Degradation rates were 11, 7, and 6% per day for Poygan sicl, Kewaunee c, and Ella Is, respectively, and these rates were related to organic matter content and pH of the soil.

The organic phosphorus of 10 Wisconsin lake sediments of diverse properties was fractionated on the basis of extractability and anion exchange properties. The fractionation procedure involved sequential extraction of the sediments with 1NHCl for 1 hour (HCl‐Po), cold 0.3NNaOH for 16 hours (Cold NaOH‐Po), and hot 0.3NNaOH for 8 hours (hot NaOH‐Po) followed by anion exchange chromatography of the NaOH extracts into three fractions: fraction I, the 0.3NNaOH eluate, contained organic P that was not retained by the resin; fraction II, the 0.5MLiCl eluate, contained organic P with exchange properties similar to inorganic orthophosphate and monophosphate esters; fraction III, the 1MLiCl + 0.2NHCl eluate, contained organic P comparable to polyphosphate esters in exchange properties. Total organic P extracted by the fractionation method was comparable to that removed by the standard Mehta et al. extractants indicating that the fractionation method provided valid total organic P data as well as information on the forms of organic P present in sediments. HCl‐Po constituted 6 to 17%, cold NaOH‐Po 60 to 80%, and hot NaOH‐Po 10 to 30% of the total organic P of the sediments. Anion exchange chromatography of the NaOH extracts showed that most of the organic P (48 to 80%) was present in fraction I, the fraction likely composed of high molecular weight humic‐fulvic complexes. Fraction II contained 14 to 36% and fraction III less than 10% of the organic P in the NaOH extracts. Total inositol penta‐ and hexa‐phosphates comprised less than 10% of the total organic P of the sediments. The total and major fractions of sediment organic P were related to organic C, total N and oxalate‐extractable Al, but were not related consistently to any other sediment property or to the trophic level of the lake.

Inorganic P added with 0.5MNH4F to noncalcareous sediments was recovered in the NH4F and succeeding 0.1NNaOH extractions. Values of NH4F‐P, corrected on the basis of the recovery of P added with the NH4F reagent, underestimated the total amount of inorganic P capable of interacting with NH4F, but by less than the corresponding uncorrected values. The amounts of inorganic P extracted by 0.5MNH4F followed by 0.1NNaOH, by citrate‐dithionite‐bicarbonate, and by 0.3NNaOH were very similar, the means of the three quantities varying by only 11 ppm. Oxalate‐extractable inorganic P exceeded these quantities by an average of 250 ppm but exceeded the sum of NH4F‐P, 1st NaOH‐P, and reductant‐soluble P by an average of 60 ppm, the difference in the latter comparison being ascribed to the partial or complete dissolution of apatite by the oxalate reagent. Although NH4F‐Al was moderately well correlated with oxalate‐Al (r= 0.70) neither variable was related to NH4F‐P. The very high correlations between NH4F‐P, 1st NaOH‐P, and reductant‐soluble P, on the one hand, and between these three fractions and oxalate‐ and citrate‐dithionite‐bicarbonate‐extractable Fe, on the other, indicate a common origin for the inorganic P in the three fractions as part of a short range order Fe‐rich complex. Apatite was low in all sediments.

Twenty‐five sediments from nine soft‐water and five hard‐water Wisconsin lakes sorbed between 20 and 100% of the inorganic P added at a level of 830 µg P/g oven‐dried sediment and between 14 and 99% of that added at a level of 6,700 µg P/g oven‐dried sediment. Noncalcareous sediments usually sorbed more added P than calcareous sediments. P sorption fended to be inversely related to the CaCO3content of the calcareous sediments. Treatment with oxalate destroyed or virtually eliminated the ability of noncalcareous sediments to sorb added P and greatly reduced that of the calcareous sediments. Oxalate extracted widely varying amounts of Fe (3 to 131 mmoles/100 g) and Al (6 to 26 mmoles/100 g) from the noncalcareous sediments; an appreciable proportion of the total Fe in the noncalcareous sediments was oxalate‐extractable. One noncalcareous sediment, high in oxalate‐extractable Fe, sorbed over 80% of inorganic P added at a level of 16,700 µg P/g oven‐dried sediment. With one exception, two treatments with citrate‐dithionite‐bicarbonate or one oxalate extraction had similar effects on the P‐sorption capacity and released comparable amounts of Fe, suggesting that the extractable Fe is derived from an amorphous iron oxide complex. The proportion of added P sorbed was closely related to the amount of oxalate Fe and to the levels of native total inorganic P in the sediments. It is postulated that a gel complex of hydrated Fe oxide which contains small amounts of Al2O3, Si(OH)4, and organic matter, is the major P‐sorbing component of sediments.

Inorganic orthophosphate (inorganic P) added with NH4F reagent to calcareous Wisconsin lake sediments was recovered in the NH4F (0–32%), citrate‐dithionite‐bicarbonate (18–23%), and first HCl (38–63%) reagents of an inorganic P fractionation scheme. Calcium fluoride, formed during NH4F extraction of calcareous materials, sorbed inorganic P, presumably resulting in the formation of a CaF2‐orthophosphate complex; inorganic P was also sorbed by CaCO3and CaF2in an NaOH system. Consequently, the values of NH4F‐P and first NaOH‐P underestimated the amount of inorganic P released from secondary Al‐ and Fe‐containing sediment components during the NH4F and first NaOH extractions, whereas the values for “reductant‐soluble P” (citrate‐dithionite‐bicarbonate‐extractable) overestimated the amount of P occluded within Fe oxides, and the P extracted subsequently by HCl overestimated the amount of acid‐extractable Ca‐P present. Because of the side reactions with CaCO3, the NH4F reagent was omitted in subsequent fractionation studies. Added inorganic P sorbed from 0.1NNaOH solution by CaCO3in pure form or in calcareous sediments was essentially quantitatively recovered in a subsequent citrate‐bicarbonate extraction. A proposed inorganic P fractionation scheme for calcareous materials, based on successive single extractions with NaOH, citrate‐dithionite‐bicarbonate, and HCl reagents, removed approximately 90% of the total inorganic P in the sediments. Native inorganic P released in the NaOH extraction originated from Fe‐ and Al‐bound P but not from Ca‐bound P, and P released in the subsequent citrate extraction was largely, if not wholly derived from P resorbed during the preceding NaOH extraction. Phosphorus released in the following HCl extraction was derived from Ca‐bound P. Previous inorganic P fractionation schemes have underestimated nonoccluded Fe‐ and Al‐bound P and overestimated Cabound P and, frequently, occluded Fe‐bound P in calcareous soils and sediments.

A modification of the luciferin‐luciferase bioluminescence technique was developed for determining adenosine triphosphate (ATP) in sediments. The method involves extraction with cold H2SO4, clean up with a cation exchange resin and use of living Aerobacter aerogenescells as an internal standard to correct for incomplete ATP recovery from the sediments. ATP recovery ranged from 20 to 85%, was a characteristic, reproducible property of a given sediment, but was not related consistently to any other sediment property. The detection limits of the method were about 0.05 µg ATP/g oven dry sediment but were dependent on the recovery characteristic of the sediment and the amounts of bioluminescence‐inhibitory solutes present in the extract used for final ATP analysis. Precision was low at ATP levels approaching the detection limit, primarily because of the high coefficient of variation shown at low ATP concentrations (about 3 × 10‐10Mfor the instrumentation and luciferin‐luciferase extracts used in this investigation). Theoretical considerations supported by preliminary experimental results indicate that the method should be applicable to soils as well as sediments. The ATP contents of nine sediment samples obtained from different lakes in Wisconsin ranged from 0.34 to 9.5 µg ATP/g sediment.

The origin and significance of adenosine triphosphate (ATP) in lake sediments were evaluated using the H2SO4‐exchange resin, bioluminescene technique for ATP determination. The effects of growth stage and media composition, particularly P status, on the ATP content of Aerobacter aerogenesand other bacterial species were characterized under well‐defined growth conditions in sediment‐free systems as a basis for interpreting ATP‐bacterial cell relationships in the presence of sediments. ATP calculated from plate count‐derived bacterial numbers using a conversion factor of 1 to 4 × 10‐10µg ATP/cell was consistent with the ATP content of irradiation‐sterilized sediment suspensions incubated with A. aerogenesor a mixed indigenous sediment microbial population, indicating that (i) no measureable extracellular ATP accumulated in the sediments, (ii) the sediment bacteria existed in a relatively inactive but not P‐deficient steady‐state characterized by an ATP content in the 1 to 4 × 10‐10µg/cell range, and (iii) the majority of the bacteria developing in the incubated sediments were capable of growth on Na caseinate agar. Bacterial ATP calculated from plate count data constituted a minor fraction of the total ATP of most of the natural sediment samples evaluated. The potential of using ATP as an index of the relative amounts of C, N, P, and S associated with the living as compared to the nonliving phase of the sediments is discussed.

The interference from As in the colorimetric determination of inorganic P by the method of Murphy and Riley was evaluated in water and sediment extract systems. Whereas up to 20 µg As/ml as arsenite (AsIII) did not interfere, arsenate (AsV) showed a positive interference and the extent of interference was independent of the level of inorganic P in both systems. On a weight basis, 1.0 µg of As is equivalent to 0.33 µg of “apparent inorganic P.” The amounts of As extractable by 3N HCl from nine surficial Wisconsin lake sediments ranged from <0.1 to 45 µg/g. The overestimation of inorganic P in 3N HCl extracts due to the positive interference from As was less than 1% in all cases. Calculations indicate that the maximum possible interference from As in a variety of extracts of these sediments is less than 2%, even if all of the As exists as arsenate, which is unlikely in reduced sediments. Arsenic was concentrated in the most recent sediments in a core from a Wisconsin lake, indicating that As interference in the determination of inorganic P in the older sediments is also not significant in view of the very low levels of As relative to inorganic P.

The amounts and forms of inorganic and organic phosphate (P) in lake sediments are discussed in relation to sediment composition and properties. The ability of noncalcareous and calcareous sediments to sorb and desorb added P in the laboratory and in the lake environment is interpreted in terms of the amounts and reactivities of sediment components involved in the sorption of P; emphasis is placed on the role of an Fe‐rich gel complex. Factors controlling the chemical mobility and biological availability of sediment inorganic and organic P are considered. Whether sediments act as a P source or sink is determined by sediment composition and limnological conditions. The factors involved in the interchange of P between the sediment interstitial water and the overlying water column are reviewed. The role of P in lake eutrophication is discussed briefly.

A Soxhlet procedure is described for the quantitative extraction from soils of γ‐BHC, aldrin, dieldrin, heptachlor epoxide, p,p′‐DDD, p,p′‐DDT, and methoxychlor in mixtures containing all these insecticides. On prolonged equilibration (30 days) of the insecticides with soil, indicatons of γ‐BHC and aldrin degradation were noted. When soils were incubated in sealed containers to restrict O2availability the rates of γ‐BHC and aldrin degradation were enhanced. No effect of soil H2O content at the time of incubation or extraction on the efficiency of the extraction procedure was found.

The exchangeability of sediment inorganic P was investigated by adding carrier‐free 32P inorganic phosphate to steady‐state lake sediment‐water systems and measuring the rate and extent of 32P incorporation into the sediment phase. The effects of sediment properties (calcareous and noncalcareous), oxygen status, and addition of inorganic P on exchangeability were evaluated. Exchangeable P comprised from 19 to 43% of the total native inorganic P of the sediments investigated. Although inorganic P was released into solution in anaerobic systems due to reduction of iron from the ferric to the ferrous state, the total pool of exchangeable P (sediment phase plus in solution) was not greatly altered. Sorbed added inorganic P (equilibrated 2 weeks) showed approximately the same degree of exchangeability as native inorganic P in noncalcareous sediments but was more exchangeable in calcareous sediments. Exchangeable P exhibited exchange rates which were resolved into three separate first‐order reactions by a graphical procedure. A major portion of exchangeable native sediment P (45 to 87%) participated in the rapid exchange reaction characterized by an exchange rate constant ranging from 7.4 to 46 hours‐1. These results show that a large pool of sediment inorganic P has a high potential for interaction with the overlying lake water and for biological assimilation.

Rates of malathion degradation in soils were related directly to extent of malathion adsorption, suggesting that degradation occurred by a chemical mechanism which was catalyzed by adsorption. Malathion degradation was rapid (50 to 90% in 24 hours, depending on the type of soil) in both sterile and nonsterile soil systems, and no lag phase occurred prior to degradation. In aqueous soil‐free systems inoclulated with a soil extract, a lag phase (7 days) occurred, followed by rapid malathion loss, likely due to microbial degradation. Thus in soils, complete chemical degradation of malathion occurred prior to microbial adaptation to malathion. To obtain information on the pathway and products of malathion degradation, chemical hydrolysis in soil‐free systems was investigated using liquid:liquid partition techniques with 14C‐labeled malathion. Hydrolysis did not occur in acid systems (> pH 2), was slow at pH 9 (< 50% in 20 days) and rapid at pH 11 (> 99% in 1 day). At pH 9 the hydrolysis resulted in formation of thiomalic acid and dimethyl thiophosphoric acid as final products with accumulation of diethyl thiomalate as an intermediate due to unequal rates of hydrolysis of the ester linkages. In soils, both ester linkages are hydrolyzed, although not at the same rate, resulting in the accumulation of diethyl thiomalate in some soils.