RESUMEN
Biochar is widely and increasingly applied to farmlands. However, it remains unclear how long-term biochar addition alters the characteristics and chlorine reactivity of soil-derived dissolved organic matter (DOM), an important terrestrial disinfection byproduct (DBP) precursor in watersheds. Here, we analyzed the spectroscopic and molecular-level characteristics of soil-derived DOM and the formation and toxicity of DBP mixtures from DOM chlorination for two long-term (5 and 11 years) biochar addition experimental farmlands. As indicated by spectroscopic indices and Fourier transform ion cyclotron resonance mass spectrometry analyses, 11 years of biochar addition could increase the humic-like and aromatic and condensed aromatic DOM and decrease the microbial-derived DOM, while 5 years of biochar addition at the other site did not. The response of condensed aromatic dissolved black carbon did not increase with increasing cumulative biochar dose but appeared to be affected by biochar aging time. Despite the possible increase in aromatic DOM, biochar addition neither increased the reactivity of DOM in forming trihalomethanes, haloacetonitriles, chloral hydrates, or haloketones nor significantly increased the microtoxicity or genotoxicity of the DBP mixture. This study indicates that biochar addition in watersheds may not deteriorate the drinking water quality via the export of terrestrial DBP precursors like wildfire events.
Asunto(s)
Cloro , Suelo , Carbón Orgánico , Desinfección , Trihalometanos/análisisRESUMEN
Land use change is an important factor affecting soil carbon and nitrogen cycle, and this is a hot spot in the study of global climate change. Based on the fixed depth method (FD) and the equivalent mass method (ESM), we explored the effects of land use change on soil organic carbon (SOC) and total nitrogen (TN) storage from the perspectives of forest reclamation and farmland vegetation restoration in Karst area. The storage of SOC and TN significantly decreased after the fore-sts were converted to grassland, eucalyptus and farmland. On average, the SOC and TN losses calculated by the FD method were 47.4% and 41.6%, respectively, the losses of SOC and TN calculated by ESM method were 54.8% and 49.7%. The SOC and TN storage increased significantly after abandonment of farmland to grassland or planting eucalyptus. On average, the SOC and TN stocks calculated based on the FD method increased by 60.5% and 49.7%, while the SOC and TN calculated by the ESM method increased by 85.5% and 70.8% respectively. The difference between FD method and ESM method was analyzed, it was concluded that FD method ignored the difference of soil bulk density after land use change. Soil bulk density was significantly increased after forest destruction. The loss of SOC and TN storage was overestimated by the FD method. Soil bulk density decreased after vegetation restoration, FD method will underestimate the enhancement of SOC and TN storage. It is suggested that the ESM method should be used to estimate the impacts of land use change on SOC and TN storage.
Asunto(s)
Carbono/análisis , Monitoreo del Ambiente , Nitrógeno/análisis , China , Suelo/químicaRESUMEN
A 3-year field experiment with randomized block design was conducted to study the effects of biochar amendment on the soil bulk density, cation exchange capacity (CEC), and particulate organic matter C (POM-C) and N (POM-N) contents in a high-yielding cropland in the North China Plain. Four treatments were installed, i.e., chemical NPK (CK), chemical NPK plus 2250 kg x hm(-2) of biochar (C1), chemical NPK plus 4500 kg x hm(-2) of biochar (C2), and 750 kg x hm(-2) of biochar-based slow release fertilizer (CN). Comparing with CK, treatments C1 and C2 significantly decreased the bulk density of 0-7.5 cm soil layer by 4.5% and 6.0%, respectively, and the treatments with biochar amendment increased the CEC in 0-15 cm soil layer, with an increment of 24.5% in treatment C2. Biochar amendment also increased the C (POM-C) and N (POM-N) contents in 0-7.5 cm soil layer, e.g., the POM-C and N contents in treatment C1 and C2 were 250% and 85%, and 260% and 120% higher than those of the CK, respectively. After three years of biochar amendment, the soil had obvious improvement in its physical and chemical properties, and played more active roles in soil carbon sequestration and greenhouse gases emission reduction.
Asunto(s)
Cationes/metabolismo , Carbón Orgánico/farmacología , Productos Agrícolas/crecimiento & desarrollo , Compuestos Orgánicos/análisis , Suelo/análisis , Secuestro de Carbono , China , Fertilizantes , Efecto Invernadero/prevención & control , Nitrógeno/análisisRESUMEN
In Quzhou County, Hebei Province where now intensive farming system is operated, original grassland and farming land under different tillage, crop straw return and fertilization measures were studied using isotope carbon for the analysis of the impact on soil organic carbon (SOC) properties. The research indicated that after change into farmland (34 years), SOC is significantly reduced and for 1 m of soil layer, the scope of reduction is from 13.3%-35% and this decrease happens in 0-40 cm of soil layer. After 8 years of fertilization, SOC can be increased at 0.83 g x kg(-1). No-tillage can significantly increase the SOC especially in 0-10 cm but plough will increase the SOC at 10-15 cm and 15-20 cm. Change of delta13 C of SOC due to land use change mainly happens in 0-20 cm, where input of organic materials from maize stored. In soil layer of 0-5 cm, only maximum 18% of SOC is from crop residues and in 15-20 cm, this percentage is about 5%.