鲁北平原养鸡场周边包气带与地下水砷化合物分布规律

Distribution of arsenic compounds in vadose zone and groundwater around the chicken farm in Lubei Plain

洛克沙胂(3-硝基-4-羟基苯胂酸)被广泛用作饲料添加剂,但大部分以原体形式随粪便排出,进入环境的洛克沙胂在微生物和光照作用下最终转化为毒性较大的As(V)和As(III)等,并在雨水或农灌的淋滤冲积下污染周边土壤、地表水和地下水。以鲁北平原某养鸡场为研究区,对鸡粪、饲料、周边表层土壤、鸡粪堆积和背景包气带垂向剖面以及地下水进行洛克沙胂及其代谢物的检测,结果饲料中洛克沙胂浓度为34mg/kg,鸡粪中HAPA(3-氨基-4-羟基苯胂酸)浓度为11 mg/kg,距离鸡场越近的表层土壤砷含量越高。三个包气带垂向剖面均以As(V)为主,As(III)含量较小。鸡粪堆积处垂向剖面上HAPA、As(V)和As(III)在土壤表层含量最高,浓度随深度增加而呈下降趋势,同时受到土壤岩性的影响,砷化合物主要的吸附层位为0~30cm与200cm以下;背景包气带垂向剖面上各砷化合物含量均明显低于鸡粪堆积处包气带垂向剖面的砷化合物含量;在鸡场内旧井中检测到浓度为165μg/kg的As(V)。结果证实鸡粪堆积导致土壤包气带、周边土壤和地下水砷含量增加,且这种污染很难消除。

Roxarsone （3-nitro-4-hydroxyphenylarsonic acid） has been used extensively in broiler poultry feed, and most roxarsone is excreted, almost untransformed, as part of the waste. After entering into the environment, roxarsone can be rapidly transformed into more toxic derivatives, such as arsenate and arsenite, via microbial action or photolysis. These arsenical products can then contaminate soil, surface water, and groundwater through rain and farming irrigation. A chicken farm of Lubei Plain was taken as the study area. The chicken manure, chicken feed, surface soil, manure-piled or background vertical vadose zone profiles, and groundwater around the chicken farm were sampled and the arsenic compounds were detected. The roxarsone concentration in the chicken feed was 34 mg/kg and the HAPA （3-amino-4-hydroxyphenylarsonic） concentration in the chicken manure was 11 mg/kg. The closer to the chicken farm, the higher the arsenic concentration in the surface soil. The arsenic compounds in the three vadose zone profiles were mainly AS（V）, with a little AS（III）. The concentrations of HAPA, As（V）, and As（III） in the manure-piled vertical vadose zone profiles were the highest in the topsoil, and they decreased as the depth increased, while also being affected by soil lithology. The main adsorption layers of arsenic compounds were at 0-30 cm depth and below 200 cm. Compared with that in the background vadose zone, the concentration of arsenic compounds in the manure-piled vertical vadose zone was higher. Among the groundwater samples, 165 μg/kg of As（V） was detected in the old well. The results confirmed that the piled chicken manure had increased the arsenic concentration in the vertical vadose zone, surface soil, and groundwater around the chicken farm, and this pollution was difficult to eliminate.