Effects of dietary protein and energy levels on cow manure excretion and ammonia volatilization.

Adjusting dietary composition is considered an effective way to reduce nutrient losses to the environment. The effects of various dietary protein and energy levels on manure composition (Ca, Mg, K, Na, N, P, and pH) were studied by determining total and direct available (free) nutrient concentrations in 8 slurries obtained from a feeding trial. Furthermore, the effects of dietary changes on NH(3) volatilization from manure slurries were studied. Increasing the crude protein (CP) content of the feed (108 to 190 g/ kg of dry matter) resulted in an average increase in total N and P content of the slurries of 56 and 48%, respectively. Feeding the cows more energy (5,050 to 6,840 kJ/kg of dry matter) increased total N and P content of the slurries by 27 and 39%, respectively. Total ammoniacal nitrogen (TAN) amounted to 52 to 77% of the total N content present in manure slurries. A low protein content or a low energy content of the diets reduced TAN concentrations in the slurries by 43% (CP) or 25% (energy). Changes in the protein content or the energy content of the feed did not significantly affect the free:total ratios of Na, Ca, and Mg content of the slurries. In agreement with the calculated NH(3,aq) (aqueous) content, the total amount of NH(3) volatilized from manure slurries was much greater (on average 10 times greater) when the cows were fed greater levels of CP. Although the slurries contained more TAN when cows were fed diets richer in energy, NH(3) volatilization from the slurries was lower.

Volatilization of ammonia from manure as affected by manure additives, temperature and mixing.

Ammonia (NH(3)) volatilization decreases the N-nutrient value of livestock manure slurries and can lead to soil acidification and eutrophication problems. In this study the effect of three manure additives (Euro Mest-mix (Mx), Effective Micro-organisms (EM), and Agri-mest (Am)) on NH(3) volatilization at three temperatures (4, 20, and 35 degrees C) was investigated. The manufacturers claim that Mx contains absorbing clay minerals and that applying Am and EM to slurry will reduce nitrogen losses, most likely by enhancing the biodegradation of manure slurry. Furthermore, the effect of mixing slurry on NH(3) volatilization has been investigated. Ammonia volatilization increased with increasing temperature and mixing of the slurries. However, at 35 degrees C mixing of manure reduced NH(3) emissions compared to non-mixing, which is related to a reduced crust resistance to gaseous transport at higher temperatures for non-mixing. Moreover, mixing introduces oxygen into the anaerobic slurry environment which will slow down microbial activity. The use of additives did not change manure characteristics (pH, dry matter, N(total), N(mineral), C/N, and C/N(organic)) and did not result in a significant (p<0.05) decrease in NH(3) emissions, except that at 4 degrees C and no mixing a significant decrease of 34% in NH(3) volatilization was observed, when Am and EM together, were applied to slurry.

In situ metal precipitation in a zinc-contaminated, aerobic sandy aquifer by means of biological sulfate reduction.

The applicability of in situ metal precipitation (ISMP) based on bacterial sulfate reduction (BSR) with molasses as carbon source was tested for the immobilization of a zinc plume in an aquifer with highly unsuitable initial conditions (high Eh, low pH, low organic matter content, and low sulfate concentrations), using deep wells for substrate injection. Batch experiments revealed an optimal molasses concentration range of 1-5 g/L and demonstrated the necessity of adding a specific growth medium to the groundwater. Without this growth medium, even sulfate, nitrogen, phosphorus, and potassium addition combined with pH optimization could not trigger biological sulfate reduction. In column experiments, precipitation of ZnS(s) was induced biologically as well as chemically (by adding Na2S). In both systems, zinc concentrations dropped from about 30 mg/L to below 0.02 mg/L. After termination of substrate addition the biological system showed continuation of BSR for at least 2 months, suggesting the insensitivity of the sulfate reducing system for short stagnations of nutrient supply, whereas in the chemical system an immediate increase of Zn concentrations was observed. A pilot experiment conducted in situ at the zinc-contaminated site showed a reduction of zinc concentrations from around 40 mg/L to below 0.01 mg/L. Termination of substrate supply did not result in an immediate stagnation of the BSR process, but continuation of BSR was observed for at least 5 weeks.

Solid-solution partitioning of organic matter in soils as influenced by an increase in pH or Ca concentration.

Organic matter is an important component of soil with regard to the binding of contaminants. Hence, the partitioning of organic matter influences the partitioning of soil contaminants. The partitioning of organic matter is, among other factors, influenced by the ionic composition and ionic strength of the soil solution. This study focuses on the behavior of organic matter after a change in the ionic composition of the soil solution, particularly in Ca concentration and pH. Different amounts of Ca(NO3)2 and NaOH were added to soil suspensions. The dissolved organic carbon (DOC) concentration increased with increasing pH (addition of NaOH), whereas an increase in Ca (addition of Ca(NO3)2) had the opposite effect. A stronger increase in DOC was observed if a single dose of NaOH was added, compared to a gradual addition of the same amount of NaOH. Cation binding by organic matter in the supernatant was calculated using the NICA-Donnan model. The log DOC concentration appeared to be correlated to the Donnan potential, calculated under the assumption that all DOC equals humic acid. This correlation was found for all eight neutral to acidic soils used in this study, although the slopes and elevations of the regression lines varied. The slope varied by a factor of 2 and the elevation appeared to be strongly influenced by the DOC concentration in the untreated soils, which is related to the total organic matter in the soil. Finally, we predicted the Donnan potential on the basis of an extraction of untreated soil with 0.03 M NaNO3, and the total additions of Ca(NO3)2 and NaOH. Comparison of these predictions with speciation calculations in solution showed a good correlation, indicating that a combination of one batch experiment and the presented calculation procedure can provide good estimations of DOC concentrations after addition of chemicals.

Contribution of individual sorbents to the control of heavy metal activity in sandy soil.

A multisurface model is used to evaluate the contribution of various sorption surfaces to the control of heavy metal activity in sandy soil samples at pH 3.7-6.1 with different sorbent contents. This multisurface model considers soil as a set of independent sorption surfaces, i.e. organic matter (NICA-Donnan), clay silicate (Donnan), and iron hydroxides (DDL, CD-MUSIC). The activities of Cu2+, Cd2+, Zn2+, Ni2+, and Pb2+ in equilibrium with the soil have been measured using a Donnan membrane technique. The metal activities predicted by the model agree with those measured reasonably well over a wide concentration range for all the metals of interest except for Pb. The modeling results suggest that soil organic matter is the most important sorbent that controls the activity of Cu2+, Cd2+, Zn2+, and Ni2+ in these sandy soils. When metal loading is high in comparison with soil organic matter content, the contribution of clay silicates to metal binding becomes more important. Adsorption to iron hydroxides is found not significant in these samples for Cu, Cd, Zn, and Ni. However, for Pb the model estimates strong adsorption on iron hydroxides. The model predicts that acidification will not only lead to increased solution concentrations but also to a shift toward more nonspecific cation-exchange type binding especially for the metals Cd, Zn, and Ni. Lowering the pH has led to a loss of 56% of Cd, 69% of Zn, and 66% of Ni during 16 years due to increased leaching.

Determination of lead in plant tissues: a pitfall due to wet digestion procedures in the presence of sulfuric acid.

Two wet digestion procedures for the determination of lead in plant materials by electrothermal atomic absorption spectrometry have been evaluated. The combination of HNO3, H2O2 and HF, though leading to incomplete digestion, yielded values corresponding well with the reference or indicative values of the vegetal tissues used. The mixture of H2SO4, HNO3 and HCIO4 gave results that were too low in some instances, owing to the formation of a mixed precipitate (Pb,Ba)SO4.