Organic matter properties of soils were studied in a territory covered by Stagnosols after afforestation. We quantified the impact of afforestation on the amount and distribution of free organic matter, microaggregates (unstable and stable under low-intensity sonification) and their components in the upper horizons of former arable soils overgrown by different species of forest vegetation. The duration of 45 years after afforestation was revealed to be not sufficient for a complete renewal of soil humus state, which appears only after till 115 years of the duration of forest cenosis. The carbon storage in light fractions remains lower by 21–40 % relative to that of forest soil, including significant losses of free organic matter (42–58 %) and occluded organic matter (12–33 %), which present the most active part of soil organic matter. The positive impact of the deposit regime, expressed by a sharp improvement of the carbon cycle balance, is reflected by the Cunstable/Cstable ratio, which decreases from 6.2 in arable soil to 2.4 on average in forest stands.
Surface sediment samples from three water reservoirs of Slovakia were analyzed for selected organochlorine pesticides (OCPs). Concentrations of total dichlorodiphenyltrichloroethanes (ΣDDTs) in the sediments from Velke Kozmalovce, Ruzin, and Zemplinska Sirava ranged from 12 to 24 ng g-1, 5 to 28 ng g-1, and 1 to 20 ng g-1, respectively, with the exception of one sediment sample from Zemplinska Sirava, having anomalously high concentration of ΣDDTs (526 ng g-1). Concentrations of hexachlorobenzene (HCB) in the sediments from these water reservoirs were generally lower and ranged from 0.3 to 9 ng g-1. Other organochlorine pesticides such as mirex, lindane and heptachlor were not detected in the surface sediments. Ratios of DDT/(DDE + DDD) were lower than 1.0 in majority of the sediment samples indicating that the degradation of the parent DDT occurred significantly and DDT in the sediments from the studied water reservoirs was derived mainly from the weathered agricultural soils. Moreover, ratios of DDD/DDE indicated that the parent DDT was degraded under aerobic conditions before depositing into the sediments of these water reservoirs. and V štúdii boli analyzované vzorky sedimentov z troch vodných nádrží Slovenska na vybrané organochlórované pesticídy (OCPs). Koncentrácie sumy DDT a jeho metabolitov DDE a DDD (ΣDDTs) v sedimentoch z vodných nádrží Veľké Kozmálovce, Ružín a Zemplínska Šírava sa nachádzali v intervale od 12 do 24 ng g-1, od 5 do 28 ng g-1 a od 1 do 20 ng g-1, s výnimkou jednej vzorky sedimentu zo Zemplínskej Šíravy, ktorá vykazovala anomálne vysokú koncentráciu ΣDDTs (526 ng g-1). Koncentrácie hexachlórbenzénu (HCB) v sedimentoch z týchto vodných nádrží boli všeobecne nižšie a pohybovali sa v intervale od 0,3 do 9 ng g-1. Iné v sedimentoch sledované organochlórované pesticídy ako mirex, lindán a heptachlór neboli zistené. Vo väčšine vzoriek sedimentov boli hodnoty pomeru DDT/(DDE + DDD) nižšie ako 1, z čoho sa dá usúdiť, že väčšia časť pôvodne prítomného DDT sa rozložila na jeho hlavné metabolity a že DDT v sedimentoch vodných nádrží pochádza najmä z erodovaných poľnohospodárskych pôd. Hodnoty pomeru DDD/DDE ukázali, že predtým ako bol DDT deponovaný do sedimentov vodných nádrží, rozkladal sa najmä za aeróbnych podmienok.
HPx is a multicomponent reactive transport model which uses HYDRUS as the flow and transport solver and PHREEQC-3 as the biogeochemical solver. Some recent adaptations have significantly increased the flexibility of the software for different environmental and engineering applications. This paper gives an overview of the most significant changes of HPx, such as coupling transport properties to geochemical state variables, gas diffusion, and transport in two and three dimensions. OpenMP allows for parallel computing using shared memory. Enhancements for scripting may eventually simplify input definitions and create possibilities for defining templates for generic (sub)problems. We included a discussion of root solute uptake and colloid-affected solute transport to show that most or all of the comprehensive features of HYDRUS can be extended with geochemical information. Finally, an example is used to demonstrate how HPx, and similar reactive transport models, can be helpful in implementing different factors relevant for soil organic matter dynamics in soils. HPx offers a unique framework to couple spatial-temporal variations in water contents, temperatures, and water fluxes, with dissolved organic matter and CO2 transport, as well as bioturbation processes.