Studies On The Effects Of Smoke And Ash From Burning Rice Straw On Growth,Quality And PAHs Contents Of Vegetable Crops

Rice straw is one of the most important crop residues. The phenomenon of burning crop residues is widespread in most vast rural areas of China. Organic pollutants generated from burning crop residues are a major source of polycyclic aromatic hydrocarbons (PAHs). PAHs aroused the world’s attention because of their harm to environment and human health. In this dissertation, the harmful substances in the artificial simulated acid rain and rice straw ash had been detected. Meanwhile, the effects of the smoke, the artificial simulated acid rain, and ash from burning rice straw on growth, quality, and PAHs contents of vegetable crops were studied. Lastly, the effects of the neutralization of three Chinese herbal decoctions to acid rain and purification of two Chinese herbal decoctions to PAHs in soil were evaluated in laboratory. The main results of the study are summarized as follows.1. The smoke from burning rice straw was dissolved in water and made into smoke dissolved liquid(or artificial simulated acid rain). The harmful substances in smoke dissolved liquid and rice straw ash had been detected. The results showed that fifteen kinds of PAHs including naphthalene,acenaphthylene,phenanthrene,fluorene,acenaphthene, anthracene,fluoranthene,pyrene,benzo(a)anthracene,chrysene,benzo(b)fluoranthene,benzo(k) fluoranthene,benzo(a)pyrene,indeno(1.2.3-c.d)pyrene and benzo(g, h, i)perylene were found in smoke dissolved liquid and rice straw ash. And some nitrite (NaNO2) with the concentration of13.9mg/kg were discovered in the rice straw ash. Furthermore, the acidity of smoke dissolved liquid increased with enhance of smoke content. In addition, most of the PAHs in smoke dissolved liquid volatilized easily and degraded fast, and especially benzo (b) fluoranthene, benzo (k) fluoranthene, indeno (1.2.3-c.d) pyrene and benzo (g, h, i) perylene did much fast. 2. Effects of the different rice straw burning smoke fumigation time (0,2,4,6,8h/d) on growth, quality, and PAHs of peas were studies in laboratory. The results showed that the smoke fumigation time showed no effect on fiber content of pea sprouts. Smoke fumigation had no significant effect on plant weight of pea sprouts.Rice straw burning smoke fumigation (2,4,6,8h/d) obviously inhibited the elongation growth of pea, but could increase the content of total sugar and protein compared with control treatment(0h/d). Crude fat content of pea sprouts decreased with increasing the smoke fumigation time. The less time of smoke fumigation (2,4,6h/d) could improve soluble solids content of the pea sprouts, and more time (8h/d) showed the inhibition on the formation of soluble solid. The results of polycyclic aromatic hydrocarbons (PAHs) contents of pea sprouts detected showed that a total of15kinds of PAHs pollutants were found in the pea sprouts which were fumigated by different smoke fumigation time and7kinds of PAHs found in the pea sprouts which were not fumigated by any smoke fumigation,AHs and average PAHs in pea sprouts decreased with increasing the smoke fumigation time, indicating that the PAHs pollutants were easily absorbed by pea sprouts in continuous rice straw smoke fumigation stress, eventually leading to the accumulation of toxic substances in the pea body, resulting in the PAHs of contamination of vegetable crops leading PAHs polluting.3. Effects of different dosages of rice straw ash on growth, quality, and PAHs of mung bean sprout and Chinese flowering cabbage were studies in laboratory. The results showed that rice straw ash could promote elongation of mung bean sprout and flowering Chinese cabbage and inhibit stem diameter to some extent. Along with the increase of dosages of straw ash, straw ash inhibited the synthesis and accumulation of total sugar in mung bean sprout and flowering Chinese cabbage. Dosages of rice straw ash could increase the conents of PHE、FLU、ACE、ANT、FLT、PYR、BaA and CHR in mung bean sprout significantly,polluting mung bean sprout.11and12kinds of PAHs in mung bean sprout and flowering Chinese cabbage which were treated by rice straw ash were detected, respectively. Different dosages of rice straw ash have different effects on total PAHs in mung bean sprout and flowering Chinese cabbage. The content ofAHs was highest (37.77μg/kg) when the mung bean sprout was treated by the dosage of2g rice straw ash per pot. But with the dosage of rice straw ash increasing (from2to8g/pot), theAHs in mung bean sprout decreased (from37.77to11.15μg/kg). Along with increasing dosages of straw ash (from90to360g/pot), theAHs in flowering Chinese cabbage rose at the beginning (22.24μg/kg) and then fell (from24.91to3.22μg/kg). The contents ofAHs in flowering Chinese cabbage under the treatment in straw ash of360g/pot were3.22μg/kg,which were lower than CK(18.34μg/kg) significantly. The above results showed that the PAHs pollutants were not easily absorbed by the plant when the concentration of PAHs in the soil increased to a certain amount. The absorbing of every PAH between mung bean sprout and flowering Chinese cabbage had no obvious rule.4. The effects of different concentrations of rice straw smoke dissolved liquid on growth, quality and PAHs content of mung bean sprouts and flowering Chinese cabbage were researched by pot experiments in laboratory. The results showed that different concentrations of the smoke dissolved liquid did not affect on the morphology, protein and soluble solids content of the mung bean sprouts but increased the crude fat and crude fiber content in plants. It also increased the PAHs content in plants. The PAHs content was the highest (5.96μg/kg) under the added2-fold dilution of smoke dissolved solution. The plant weight, root weight and root to shoot ratio of flowering Chinese cabbage showed significant difference with the control but showed no significant effect on the stem diameter and plant height under original smoke dissolved solution treamment. Smoke dissolved solution could inhibit the synthesis of total sugar and crude fat to some extent in flowering Chinese cabbage and increased the crude fiber content in mung bean sprouts. The PAHs content in different treated plants showed no apparent regularity.5. The effects of the neutralization of three Chinese herbal decoctions to artificial simulated acid rain acidity(made from smoke dissolved solution) and purification of two Chinese herbal decoctions to PAHs in soil were evaluated in laboratory, the results showed that the Indigowoad leaf boiled liquid could effectively neutralize artificial simulated acid rain acidity in a short time, the pH value of artificial simulated acid rain increased from6.5in the beginning to7.1on the fourth day after artificial simulated acid rain treated by Indigowoad leaf boiled liquid,which were all higher than CK. The pH value of artificial simulated acid rain remained weak alkaline level after the eighth day. Isatis root boiled liquid had no effect on neutralization of artificial simulated acid rain acidity, and could exacerbate acidity of artifical simulated acid rain on the contrary from the beginning to the fortieth day, the pH value getting down from4.6to4.1. The effect of the neutralization of licorice boiled liquid to artificial simulated acid rain acidity was very weak and slow, the pH of artificial simulated acid rain treated by licorice boiled liquid after40days later rose to a neutral state. This study showed that the Indigowoad leaf boiled liquid could effectively neutralize artificial simulated acid rain acidity in a short time, which was one of the effective measures for the improvement and management of acid soils.The honeysuckle and clove boiled liquid show obvious effect on degradation and purification of PAHs in the soil, but distilled water is not conducive to degradation of PAHs in the soil. The contents of Σ11PAHs in the soil soaked by honeysuckle boiled liquid and the conents of Σ7PAHs in the soil soaked by clove boiled liquid were all lower than those of CK significantly,and the conents of Σ16PAHs in the soil soaked by honeysuckle and clove boiled liquid were all lower than those of CK insignificantly. Such as the contents of most kinds of PAHs in the soil soaked by distilled water were higher than those of CK. Their contents of the ΣAHs and average PAHs were higher than those of CK. It was first reported that plant decoction was used to study on degradation and purification of PAHs pollutions in the soil, which opened up new ways and new ideas for the comprehensive management of soil pollution in the present studies.